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Background: To avoid causing a thromboembolic event in patients undergoing catheter ablation for atrial fibrillation (AF), patients are treated with oral anticoagulants (OAC) prior to the procedure. Despite being on anticoagulants, some patients develop a left atrial appendage thrombus (LAAT). To exclude the presence of LAAT, transesophageal ultrasound (TEE) is performed in all patients prior to the procedure. We hypothesized continuous treatment with anticoagulants would result in a low prevalence of LAAT, in patients with low CHA2DS2‐VASc score. Method: Medical records of consecutive patients planned to undergo AF ablation at Lund University Hospital during the years 2018–2020 were reviewed retrospectively. Examination protocols from transesophageal and transthoracic echocardiography were examined for LAAT and spontaneous echo contrast (SEC). Patients with LAAT and SEC were compared to patients without using Mann–Whitney U‐test and Pearson Chi‐squared analysis to test for correlation. Results: Of 553 patients, three patients (0.54%) had LAAT, and 18 (3.25%) had spontaneous contrast (SEC). Patients with LAAT or SEC had a higher CHA2DS2‐VASc score, more often presented in AF at TEE and less often had a normal sized left atrium. Conclusion: There is a low prevalence of LAAT and SEC in patients with AF scheduled for pulmonary vein isolation. Patients with SEC or LAAT tend to have paroxysmal AF less often and more often presented in AF at admission. No patients with CHA2DS2‐VASc 0, paroxysmal AF, normal sized left atrium and sinus rhythm at TEE were found to have LAAT or SEC. [ABSTRACT FROM AUTHOR]

Background: Hypokalemia is common in hospitalized patients and associated with ECG abnormalities. The prevalence and prognostic value of ECG abnormalities in hypokalemic patients are, however, not well established. Methods: The study was a multicentered cohort study, including all ault patients with an ECG and potassium level <4.4 mmol/L recorded at arrival to four emergency departments in Denmark and Sweden. Using computerized measurements from ECGs, we investigated the relationship between potassium levels and heart rate, QRS duration, corrected QT (QTc) interval, ST‐segment depressions, T‐wave flattening, and T‐wave inversion using cubic splines. Within strata of potassium levels, we further estimated the hazard ratio (HR) for 7‐day mortality, admission to the intensive care unit (ICU), and diagnosis of ventricular arrhythmia or cardiac arrest, comparing patients with and without specific ECG abnormalities matched 1:2 on propensity scores. Results: Among 79,599 included patients, decreasing potassium levels were associated with a concentration‐dependent increase in all investigated ECG variables. ECG abnormalities were present in 40% of hypokalemic patients ([K+] <3.5 mmol/L), with T‐wave flattening, ST‐segment depression, and QTc prolongation occurring in 27%, 16%, and 14%. In patients with mild hypokalemia ([K+] 3.0–3.4 mmol/L), a heart rate >100 bpm, ST‐depressions, and T‐wave inversion were associated with increased HRs for 7‐day mortality and ICU admission, whereas only a heart rate >100 bpm predicted both mortality and ICU admission among patients with [K+] <3.0 mmol/L. HR estimates were, however, similar to those in eukalemic patients. The low number of events with ventricular arrhythmia limited evaluation for this outcome. Conclusions: ECG abnormalities were common in hypokalemic patients, but they are poor prognostic markers for short‐term adverse events under the current standard of care. [ABSTRACT FROM AUTHOR]

The ECG diagnosis of LVH is predominantly based on the QRS voltage criteria. The classical paradigm postulates that the increased left ventricular mass generates a stronger electrical field, increasing the leftward and posterior QRS forces, reflected in the augmented QRS amplitude. However, the low sensitivity of voltage criteria has been repeatedly documented. We discuss possible reasons for this shortcoming and proposal of a new paradigm. The theoretical background for voltage measured at the body surface is defined by the solid angle theorem, which relates the measured voltage to spatial and non‐spatial determinants. The spatial determinants are represented by the extent of the activation front and the distance of the recording electrodes. The non‐spatial determinants comprise electrical characteristics of the myocardium, which are comparatively neglected in the interpretation of the QRS patterns. Various clinical conditions are associated with LVH. These conditions produce considerable diversity of electrical properties alterations thereby modifying the resultant QRS patterns. The spectrum of QRS patterns observed in LVH patients is quite broad, including also left axis deviation, left anterior fascicular block, incomplete and complete left bundle branch blocks, Q waves, and fragmented QRS. Importantly, the QRS complex can be within normal limits. The new paradigm stresses the electrophysiological background in interpreting QRS changes, i.e., the effect of the non‐spatial determinants. This postulates that the role of ECG is not to estimate LV size in LVH, but to understand and decode the underlying electrical processes, which are crucial in relation to cardiovascular risk assessment. [ABSTRACT FROM AUTHOR]

Background: Prolonged endurance exercise increase the risk of atrial fibrillation (AF) in men. Functional parameters may help separate physiological from pathological atrial remodeling in athletes. LA mechanical dispersion (LA MD) is associated with AF in the general population, but the associations between prolonged exercise, LA MD and AF are not known. Purpose: To describe LA MD in veteran athletes with and without paroxysmal AF (pAF) and to investigate LA MD's ability to identify veteran athletes with pAF. Methods: Two hundred and ninety‐three men, skiers with (n = 57) and without (n = 87) pAF, and controls with (n = 61) and without pAF (n = 88) underwent an echocardiographic exam in sinus rhythm. LA reservoir strain (LASr) was measured, and LA MD defined as the standard deviation of time‐to‐peak strain (SD‐TPS). Results: Skiers (mean age 70.7 ± 6.7 years) reported an average of 40–50 years of endurance exercise. LA volumes were associated with pAF and athletic status (p <.001). SD‐TPS was associated with pAF (p <.001) but not athletic status (p =.173). We found no significant trend between years of exercise and SD‐TPS in individuals without AF (p =.893). SD‐TPS did not add incremental value in identifying athletes with pAF in addition to clinical markers, QRS width, LA volume, and LASr (p =.056). Conclusion: LA MD was associated with pAF regardless of athletic status but not related to years of endurance exercise, suggesting LA MD could be a promising marker of pathological atrial remodeling in athletes. However, we found no incremental value of LA MD identifying athletes with pAF when LASr was included in the model. [ABSTRACT FROM AUTHOR]

Summary: Background: The recurrence rate of atrial fibrillation (AF) in horses after cardioversion to sinus rhythm (SR) is relatively high. Atrial fibrillatory rate (AFR) derived from surface ECG is considered a biomarker for electrical remodelling and could potentially be used for the prediction of successful AF cardioversion and AF recurrence. Objectives: Evaluate if AFR was associated with successful treatment and could predict AF recurrence in horses. Study design: Retrospective multicentre study. Methods: Electrocardiograms (ECG) from horses with persistent AF admitted for cardioversion with either medical treatment (quinidine) or transvenous electrical cardioversion (TVEC) were included. Bipolar surface ECG recordings were analysed by spatiotemporal cancellation of QRST complexes and calculation of AFR from the remaining atrial signal. Kaplan‐Meier survival curve and Cox regression analyses were performed to assess the relationship between AFR and the risk of AF recurrence. Results: Of the 195 horses included, 74 received quinidine treatment and 121 were treated with TVEC. Ten horses did not cardiovert to SR after quinidine treatment and AFR was higher in these, compared with the horses that successfully cardioverted to SR (median [interquartile range]), (383 [367‐422] vs 351 [332‐389] fibrillations per minute (fpm), P <.01). Within the first 180 days following AF cardioversion, 12% of the quinidine and 34% of TVEC horses had AF recurrence. For the horses successfully cardioverted with TVEC, AFR above 380 fpm was significantly associated with AF recurrence (hazard ratio = 2.4, 95% confidence interval 1.2‐4.8, P =.01). Main limitations: The treatment groups were different and not randomly allocated, therefore the two treatments cannot be compared. Medical records and the follow‐up strategy varied between the centres. Conclusions: High AFR is associated with failure of quinidine cardioversion and AF recurrence after successful TVEC. As a noninvasive marker that can be retrieved from surface ECG, AFR can be clinically useful in predicting the probability of responding to quinidine treatment as well as maintaining SR after electrical cardioversion. [ABSTRACT FROM AUTHOR]

This collaborative statement from the International Society for Holter and Noninvasive Electrocardiology/Heart Rhythm Society/European Heart Rhythm Association/Asia Pacific Heart Rhythm Society describes the current status of mobile health ("mHealth") technologies in arrhythmia management. The range of digital medical tools and heart rhythm disorders that they may be applied to and clinical decisions that may be enabled are discussed. The facilitation of comorbidity and lifestyle management (increasingly recognized to play a role in heart rhythm disorders) and patient self‐management are novel aspects of mHealth. The promises of predictive analytics but also operational challenges in embedding mHealth into routine clinical care are explored. [ABSTRACT FROM AUTHOR]

This collaborative statement from the International Society for Holter and Noninvasive Electrocardiology/ Heart Rhythm Society/ European Heart Rhythm Association/ Asia Pacific Heart Rhythm Society describes the current status of mobile health ("mHealth") technologies in arrhythmia management. The range of digital medical tools and heart rhythm disorders that they may be applied to and clinical decisions that may be enabled are discussed. The facilitation of comorbidity and lifestyle management (increasingly recognized to play a role in heart rhythm disorders) and patient self‐management are novel aspects of mHealth. The promises of predictive analytics but also operational challenges in embedding mHealth into routine clinical care are explored. [ABSTRACT FROM AUTHOR]

Background and Purpose: Inhibition of the G-protein gated ACh-activated inward rectifier potassium current, IK,ACh may be an effective atrial selective treatment strategy for atrial fibrillation (AF). Therefore, the anti-arrhythmic and electrophysiological properties of a novel putatively potent and highly specific IK,ACh inhibitor, XAF-1407 (3-methyl-1-[5-phenyl-4-[4-(2-pyrrolidin-1-ylethoxymethyl)-1-piperidyl]thieno[2,3-d]pyrimidin-6-yl]azetidin-3-ol), were characterised for the first time in vitro and investigated in horses with persistent AF.Experimental Approach: The pharmacological ion channel profile of XAF-1407 was investigated using cell lines expressing relevant ion channels. In addition, eleven horses were implanted with implantable cardioverter defibrillators enabling atrial tachypacing into self-sustained AF. The electrophysiological effects of XAF-1407 were investigated after serial cardioversions over a period of 1 month. Cardioversion success, drug-induced changes of atrial tissue refractoriness, and ventricular electrophysiology were assessed at baseline (day 0) and days 3, 5, 11, 17, and 29 after AF induction.Key Results: XAF-1407 potently and selectively inhibited Kir 3.1/3.4 and Kir 3.4/3.4, underlying the IK,ACh current. XAF-1407 treatment in horses prolonged atrial effective refractory period as well as decreased atrial fibrillatory rate significantly (~20%) and successfully cardioverted AF, although with a decreasing efficacy over time. XAF-1407 shortened atrioventricular-nodal refractoriness, without effect on QRS duration. QTc prolongation (4%) within 15 min of drug infusion was observed, however, without any evidence of ventricular arrhythmia.Conclusion and Implications: XAF-1407 efficiently cardioverted sustained tachypacing-induced AF of short duration in horses without notable side effects. This supports IK,ACh inhibition as a potentially safe treatment of paroxysmal AF in horses, suggesting potential clinical value for other species including humans. [ABSTRACT FROM AUTHOR]

Introduction: Long QT syndrome (LQTS) mutation carriers have elevated the risk of cardiac events even in the absence of QTc prolongation; however, mutation penetrance in patients with normal QTc may be reflected in abnormal T‐wave shape, particularly in KCNH2 mutation carriers. We aimed to assess whether the magnitude of a three‐dimensional T‐wave vector (TwVM) will identify KCNH2‐mutation carriers with normal QTc at risk for cardiac events. Methods: Adult LQT2 patients with QTc < 460 ms in men and <470 ms in women (n = 113, age 42 ± 16 years, 43% male) were compared with genotype‐negative family members (n = 1007). The TwVM was calculated using T‐wave amplitudes in leads V6, II, and V2 as the square root of (TV62 + TII2 + (0.5*TV2)2). Cox regression analysis adjusted for gender and time‐dependent beta‐blocker use was performed to assess cardiac event (CE) risk, defined as syncope, aborted cardiac arrest, implantable cardioverter‐defibrillator therapy, or sudden death. Results: Dichotomized by median of 0.30 mV, lower TwVM was associated with elevated CE risk compared to those with high TwVM (HR = 2.95, 95% CI, 1.25‐6.98, P = .014) and also remained significant after including sex and time‐dependent beta‐blocker usage in the Cox regression analysis (HR = 2.64, 95% CI, 1.64‐4.24, P < .001). However, these associations were found only in women but not in men who had low event rates. Conclusion: T‐wave morphology quantified as repolarization vector magnitude using T‐wave amplitudes retrieved from standard 12‐lead electrocardiogram predicts cardiac events risk in LQT2 women and appears useful for risk stratification of KCNH2‐mutation carriers without QTc prolongation. [ABSTRACT FROM AUTHOR]

Introduction: The atrial fibrillatory rate is a potential biomarker in the study of antiarrhythmic drug effects on atrial fibrillation (AF). The purpose of this study was to evaluate whether dose‐dependent changes in the atrial fibrillatory rate can be monitored on surface electrocardiography (ECG) following treatment with dofetilide, ranolazine, and a combination of the two in an acute model of AF in horses. Methods and Results: Eight horses were subjected to pacing‐induced AF on 4 separate days. Saline (control), dofetilide, ranolazine, or a combination of dofetilide and ranolazine was administered in four incremental doses. Atrial fibrillatory activity was extracted from surface ECGs using spatiotemporal QRST cancellation. The mean atrial fibrillatory rate before drug infusion was 297 ± 27 fpm. Dofetilide reduced the atrial fibrillatory rate following the infusion of low doses (0.89 µg/kg, P < 0.05) and within 5 minutes preceding cardioversion (P < 0.05). Cardioversion with ranolazine was preceded by a reduction in the atrial fibrillatory rate in the last minute (P < 0.05). The combination of drugs reduced the atrial fibrillatory rate in a similar manner to dofetilide used alone. A trend toward a lower atrial fibrillatory rate before drug infusion was found among horses cardioverting on low doses of the drugs. Conclusion: The atrial fibrillatory rate derived from surface ECGs showed a difference in the mode of action on AF between dofetilide and ranolazine. Dofetilide reduced the atrial fibrillatory rate, whereas ranolazine displayed a cardioverting mechanism that was distinct from a slowing of the fibrillatory process. [ABSTRACT FROM AUTHOR]

Background: Myocardial scar burden quantification is an emerging clinical parameter for risk stratification of sudden cardiac death and prediction of ventricular arrhythmias in patients with left ventricular dysfunction. We investigated the relationships among semiautomated Selvester score burden and late gadolinium enhancement-cardiovascular magnetic resonance (LGE-CMR) assessed scar burden and clinical outcome in patients with underlying heart failure, left bundle branch block (LBBB) and implantable cardioverter-defibrillator (ICD) treatment.Methods: Selvester QRS scoring was performed on all subjects with ischemic and nonischemic dilated cardiomyopathy at Skåne University Hospital Lund (2002-2013) who had undergone LGE-CMR and 12-lead ECG with strict LBBB pre-ICD implantation.Results: Sixty patients were included; 57% nonischemic dilated cardiomyopathy and 43% ischemic cardiomyopathy with mean left ventricular ejection fraction of 27.6% ± 11.7. All patients had scar by Selvester scoring. Sixty-two percent had scar by LGE-CMR (n = 37). The Spearman correlation coefficient for LGE-CMR and Selvester score derived scar was r = .35 (p = .007). In scar negative LGE-CMR, there was evidence of scar by Selvester scoring in all patients (range 3%-33%, median 15%). Fourteen patients (23%) had an event during the follow-up period; 11 (18%) deaths and six adequate therapies (10%). There was a moderate trend indicating that presence of scar increased the risk of clinical endpoints in the LGE-CMR analysis (p = .045).Conclusion: There is a modest correlation between LGE-CMR and Selvester scoring verified myocardial scar. CMR based scar burden is correlated to clinical outcome, but Selvester scoring is not. The Selvester scoring algorithm needs to be further refined in order to be clinically relevant and reliable for detailed scar evaluation in patients with LBBB. [ABSTRACT FROM AUTHOR]

Background Primary prophylactic implantable cardioverter defibrillator ( ICD) therapy is indicated for patients with reduced left ventricular ejection fraction ( LVEF). We aimed to determine if preoperative clinical risk profiling can predict long-term benefit, and if clinical risk scores can be applied and improved in a patient cohort outside the clinical trial setting. Methods Using registry data, 789 patients with reduced LVEF who received ICDs for primary prevention during 2006-2011 were identified (age 64 ± 11 years, 82% men, 63% ischemic etiology, 52% cardiac resynchronization therapy with defibrillator). The patients were divided into three risk groups, based on the presence of baseline clinical risk factors (age >70, QRS duration >120 ms, New York Heart Association class III- IV, atrial fibrillation history, or creatinine >106 μmol/L). Endpoints were all-cause mortality and survival free of adequate ICD therapy. Results Mean follow-up was 39 ± 18 months. Annual mortality was 7.6%, and increased with risk group ( p < .001). Rates of appropriate antitachycardia pacing and shock therapy were not statistically different between the groups, and ranged from 11%-16% and 6%-14%, respectively. By combining the previous risk score with data on diabetes, a better independent prediction of mortality was achieved; mortality rates then ranged from 11% (low-risk) to 46% (high-risk) ( p < .0001). Conclusions Implantable cardioverter defibrillator therapies occur across the spectrum of comorbidities in a population with systolic heart failure. However, all-cause mortality is considerably higher in the group of patients with accumulated risk factors, and using the proposed scoring system can be helpful for the evaluation and risk stratification of the patient prior to making a decision for a primary prophylactic ICD implantation. [ABSTRACT FROM AUTHOR]

Background: It has previously been demonstrated that orthogonal P-wave morphology in healthy athletes does not depend on atrial size, but the possible impact of left atrial orientation on P-wave morphology remains unknown. In this study, we investigated if left atrial transverse orientation affects P-wave morphology in different populations.Methods: Forty-seven patients with atrial fibrillation, 21 patients with arrhythmogenic right ventricular cardiomyopathy, 67 healthy athletes, and 56 healthy volunteers were included. All underwent cardiac magnetic resonance imaging or computed tomography and the orientation of the left atrium was determined. All had 12-lead electrocardiographic recordings, which were transformed into orthogonal leads and orthogonal P-wave morphology was obtained.Results: The median left atrial transverse orientation was 87 (83, 91) degrees (lower and upper quartiles) in the total study population. There was no difference in left atrial transverse orientation between individuals with different orthogonal P-wave morphologies.Conclusions: The physiological variation in left atrial orientation was small within as well as between the different populations. There was no difference in left atrial transverse orientation between subjects with type 1 and type 2 P-wave morphology, implying that in this setting the P-wave morphology was more dependent on atrial conduction than orientation. [ABSTRACT FROM AUTHOR]

Atrial fibrillation (AF) is currently considered a risk factor for stroke. Depending on the severity of clinical factors (risk scores) a recommendation for full anticoagulation is made. Although AF is most certainly a risk factor for ischemic stroke, it is not necessarily the direct cause of it. The causality of association between AF and ischemic stroke is questioned by the reported lack of temporal relation between stroke events and AF paroxysms (or atrial high-rate episodes detected by devices). In different studies, only 2% of patients had subclinical AF > 6 minutes in duration at the time of stroke or systemic embolism. Is it time to consider AF only one more factor of endothelial disarray rather than the main contributor to stroke? In this "opinion paper" we propose to consider not only clinical variables predicting AF/stroke but also electrocardiographic markers of atrial fibrosis, as we postulate this as a strong indicator of risk of AF/stroke. We ask if it is time to change the paradigm and to consider, in some special situations, to protect patients (preventing stroke) who have no evidence of AF. [ABSTRACT FROM AUTHOR]

Background: During atrial fibrillation (AF), conventional electrophysiological techniques for assessment of refractory period or conduction velocity of the atrioventricular (AV) node cannot be used. We aimed at evaluating changes in AV nodal properties during administration of tecadenoson and esmolol using a novel ECG-based method.Methods: Fourteen patients (age 58 ± 8 years, 10 men) with AF were randomly assigned to either 75 or 300 μg intravenous tecadenoson. After tecadenoson wash-out, patients received esmolol continuously (100 μg/kg per min for 10 mins, then 50 μg/kg per min for 50 mins). Atrial fibrillatory rate (AFR) and heart rate (HR) were assessed in 15-min segments. Using the novel method, we assessed the absolute refractory periods of the slow and fast pathways (aRPs and aRPf) of the AV node to produce an estimate of the functional refractory period.Results: During esmolol infusion, AFR and HR were significantly decreased and the absolute refractory period was significantly prolonged in both pathways (aRPs: 387 ± 73 vs 409 ± 62 ms, P < 0.05; aRPf: 490 ± 80 vs 529 ± 58 ms, P < 0.05). During both tecadenoson doses, HR decreased significantly and AFR was unchanged. Both aRPs and aRPf were prolonged for a 75 μg dose (aRPs: 322 ± 97 vs 476 ± 75 ms, P < 0.05; aRPf: 456 ± 102 vs 512 ± 55 ms, P < 0.05) whereas a trend toward prolongation was observed for a 300 μg dose.Conclusions: The estimated parameters reflect expected changes in AV nodal properties, i.e., slower conduction through the AV node for tecadenoson and prolongation of the AV node refractory period for esmolol. Thus, the proposed approach may be used to assess drug effects on the AV node in AF patients. [ABSTRACT FROM AUTHOR]

Background Cardiac resynchronization therapy (CRT) with or without a defibrillator has a positive effect on mortality and morbidity for patients with heart failure. However, comparisons between CRT-defibrillators (CRT-D) and CRT-pacemakers (CRT-P) are relatively scarce outside the clinical trial setting. This study aimed to assess baseline characteristics in relation to long-term prognosis in patients treated with CRT, and to investigate the potential benefit of CRT-D versus CRT-P. Methods Data were retrospectively collected from the medical records of all consecutive patients treated with CRT-P or primary prophylactic CRT-D at a large tertiary care center between 1999 and 2012. Predictors of mortality were investigated, and time-dependent analysis was performed with all-cause mortality as the primary end point. Results A total of 705 patients were included (69.6 ± 10 years, 78% New York Heart Association classes III-IV, left ventricular ejection fraction median 25%, 16% female, 36% CRT-D). The patients were followed for a median of 59 months. Annual mortality differed between CRT-D primary prophylactic and CRT-P groups (5.3% and 11.8%, respectively), but when adjusted for covariates, CRT-D treatment (compared to CRT-P) was not associated with better long-term survival. Independent predictors of survival were: age, use of loop diuretics, hemoglobin levels, and use of renin angiotensin aldosterone system blockers. Conclusions In CRT treatment outside of the clinical trial setting, CRT-D treatment was not an independent predictor of long-term survival. Future research should focus on correct selection of the patients who receive enough benefit of an added defibrillator to justify CRT-D implantation instead of CRT-P treatment only. [ABSTRACT FROM AUTHOR]

Background Vernakalant is a novel atrial-selective antiarrhythmic drug able to convert recent-onset atrial fibrillation (AF) with reportedly low proarrhythmic risk. Successful cardioversion predictors are largely unknown. We sought to evaluate clinical and electrocardiographic predictors of cardioversion of recent-onset AF with vernakalant. Methods Consecutive patients with AF ≤48 hours admitted for cardioversion with vernakalant (n = 113, median age 62 years, 69 male) were included. Sinus rhythm (SR) within 90 minutes after infusion start was considered to be successful cardioversion. Predictive values of demographics, concomitant therapy, comorbidities, and electrocardiographic parameters were assessed. Atrial fibrillatory rate (AFR), exponential decay, and mean fibrillatory wave amplitude were measured from surface ECG using QRST cancellation and time-frequency analysis. Results Cardioversion was achieved in 66% of patients. Conversion rate was higher in women than in men (80% vs 58%, P = 0.02) while none of other clinical characteristics, including index AF episode duration, could predict SR restoration. Female gender was predictive of vernakalant's effect in logistic regression analysis (OR = 2.82 95%CI 1.18-6.76, P = 0.020). There was no difference in AFR (350 ± 60 vs 348 ± 62 fibrillations per minute [fpm], P = 0.893), mean fibrillatory wave amplitude (86 ± 33 vs 88 ± 67 μV, P = 0.852), or exponential decay (1.30 ± 0.42 vs 1.35 ± 0.42, P = 0.376) between responders and nonresponders. Conclusions Female gender is associated with a higher rate of SR restoration using intravenous (i.v.) vernakalant for recent-onset AF. ECG-derived indices of AF organization, which previous studies associated with effect of rhythm control interventions, did not predict vernakalant's effect. [ABSTRACT FROM AUTHOR]

Heart Rate Variability and Irregularity During AF Introduction Irregularity measures have been suggested as risk indicators in patients with atrial fibrillation (AF); however, it is not known to what extent they are affected by commonly used rate-control drugs. We aimed at evaluating the effect of metoprolol, carvedilol, diltiazem, and verapamil on the variability and irregularity of the ventricular response in patients with permanent AF. Methods and Results Sixty patients with permanent AF were part of an investigator-blind cross-over study, comparing 4 rate-control drugs (diltiazem, verapamil, metoprolol, and carvedilol). We analyzed five 20-minute segments per patient: baseline and the 4 drug regimens. On every segment, heart rate (HR) variability and irregularity of RR series were computed. The variability was assessed as standard deviation, pNN20, pNN50, pNN80, and rMSSD. The irregularity was assessed by regularity index, approximate (ApEn), and sample entropy. A significantly lower HR was obtained with all drugs, the HR was lowest using the calcium channel blockers. All drugs increased the variability of ventricular response in respect to baseline (as an example, rMSSD: baseline 171 ± 47 milliseconds, carvedilol 229 ± 58 milliseconds; P < 0.05 vs. baseline, metoprolol 226 ± 66 milliseconds; P < 0.05 vs. baseline, verapamil 228 ± 84; P < 0.05 vs. baseline, diltiazem 256 ± 87 milliseconds; P < 0.05 vs. baseline and all other drugs). Only β-blockers significantly increased the irregularity of the RR series (as an example, ApEn: baseline 1.86 ± 0.13, carvedilol 1.92 ± 0.09; P < 0.05 vs. baseline, metoprolol 1.93 ± 0.08; P < 0.05 vs. baseline, verapamil 1.86 ± 0.22 ns, diltiazem 1.88 ± 0.16 ns). Conclusion Modification of AV node conduction by rate-control drugs increase RR variability, while only β-blockers affect irregularity. [ABSTRACT FROM AUTHOR]

Aims Exercise increases risk of ventricular arrhythmia in subjects with arrhythmogenic right ventricular cardiomyopathy ( ARVC). We aimed to investigate the impact of exercise on myocardial function in ARVC subjects. Methods and Results We included 110 subjects (age 42 ± 17 years), 65 ARVC patients and 45 mutation-positive family members. Athletes were defined as subjects with ≥4 h vigorous exercise/week [≥1440 metabolic equivalents ( METs × minutes/week)] during a minimum of 6 years. Athlete definition was fulfilled in 37/110 (34%) subjects. We assessed right ventricular ( RV) and left ventricular ( LV) myocardial function by echocardiography, and by magnetic resonance imaging ( MRI). The RV function by RV fractional area change ( FAC), RV global longitudinal strain ( GLS) by echocardiography, and RV ejection fraction ( EF) by MRI was reduced in athletes compared with non-athletes ( FAC 34 ± 9% vs. 40 ± 11%, RVGLS -18.3 ± 6.1% vs. -22.0 ± 4.8%, RVEF 32 ± 8% vs. 43 ± 10%, all P < 0.01). LV function by LVEF and LVGLS was reduced in athletes compared with non-athletes ( LVEF by echocardiography 50 ± 10% vs. 57 ± 5%, LVEF by MRI 46 ± 6% vs. 53 ± 8%, and LVGLS -16.7 ± 4.2% vs. -19.4 ± 2.9%, all P < 0.01). The METs × minutes/week correlated with reduced RV and LV function by echocardiography and MRI (all P < 0.01). The LVEF by MRI was also reduced in subgroups of athlete index patients (46 ± 7% vs. 54 ± 10%, P = 0.02) and in athlete family members (47 ± 3% vs. 52 ± 6%, P < 0.05). Conclusion Athletes showed reduced biventricular function compared with non-athletes in ARVC patients and in mutation-positive family members. The amount and intensity of exercise activity was associated with impaired LV and RV function. Exercise may aggravate and accelerate myocardial dysfunction in ARVC. [ABSTRACT FROM AUTHOR]

Background Orthogonal P-wave morphology has previously been described in different populations, but its relation to atrial size has not been studied in detail. In this study, we investigated whether atrial size affects P-wave morphology in athletes, who are known to have different degrees of atrial enlargement. Methods A total of 504 healthy, male, professional soccer players were included (median age 25 years). All underwent echocardiographic and 12-lead electrocardiographic (ECG) recordings. The ECG was transformed into orthogonal leads, using the inverse Dower transform. The association between echocardiographic parameters and standard P-wave measures (i.e., orthogonal morphology, left atrial abnormality assessed as negative P-wave terminal force [PTF] in lead V1 > 0.04 mm × s, and duration) was analyzed. Results The vast majority had either type 1 P-wave morphology (75%) (positive leads X and Y and negative lead Z) or type 2 P-wave morphology (22%) (positive leads X and Y and biphasic lead Z [negative/positive]). Left atrial enlargement (≥29 mL/m2) was found in 79% on echocardiography. There was no significant difference in left atrial end-systolic volume, left or right atrial diameters, or right atrial area between individuals with different P-wave morphologies. ECG signs of left atrial abnormality were found in eight subjects, who did not have significantly larger left atrial dimensions than the rest. Conclusions We demonstrated that P-wave morphology does not depend on the size of the atria in young, healthy athletes, and that PTF is not a reliable marker of left atrial enlargement in the current population. [ABSTRACT FROM AUTHOR]

Background In this study we hypothesized that signs of atypical atrial activation would be associated with cardiac resynchronization therapy (CRT) response in patients with mildly symptomatic heart failure (CHF), left ventricular dysfunction, and wide QRS complex. Methods Patients included in the CRT-D arm in MADIT-CRT were studied (n = 892). Unfiltered signal-averaged P waves were analyzed to determine orthogonal P-wave morphology (typical morphologies were predefined as having positive signals in Leads X and Y and a negative or negative-positive signal in Lead Z. All other patterns were classified as atypical). The association between P-wave morphology and data on echocardiographic response at 1 year was analyzed. Results Atypical P-wave morphology was found in 21% (n = 186) of the patients at baseline. Patients with atypical P-wave morphology were more often female (31% vs. 24%, P = 0.025), had lower BMI (28 ± 5 kg/m2 vs. 29 ± 5 kg/m2, P = 0.008), had more ischemic CHF (60% vs. 52%, P = 0.026) and had smaller left atrial volumes (90 ± 20 mL vs. 94 ± 22 mL, P = 0.034). Atypical P-wave morphology at baseline was associated with superior response to CRT at 1 year with a larger reduction in left ventricular end-diastolic volume (−23 ± 12% vs. −20 ± 11%, P = 0.009), left ventricular end-systolic volume (−36 ± 16% vs. −31 ± 16%, P = 0.006), and left atrial volume (−31 ± 12% vs. −27 ± 12%, P = 0.005), with a slightly larger absolute increase in left ventricular ejection fraction (LVEF) (12 ± 5% vs. 11 ± 5%, P = 0.009). These associations were found to be independent of traditional predictors. Conclusion The presence of atypical P-wave morphology recorded is independently associated with a favorable echocardiographic cardiac remodeling response to CRT. [ABSTRACT FROM AUTHOR]

Aims Atrial fibrillation (AF) is a frequent co-morbidity in heart failure (HF) associated with increased mortality, but little is known about the mechanisms underlying AF onset in HF patients. We evaluated the association of cardiovascular and genetic risk factors with AF in HF patients. Methods and results Individuals hospitalized for HF (n = 1040; 500 with AF) were identified from a large, population-based cohort study (n = 30 447; 2339 with AF). Genetic polymorphisms in the chromosomal regions 4q25 (rs2200733) and 16q22 (rs2106261) associated with AF in genome-wide association studies were genotyped. Association of cardiovascular risk factors and polymorphisms with AF was tested in HF patients and the entire cohort using both prospective and non-time-dependent models. Cardiovascular risk factors—hypertension, body mass index, sex, smoking, diabetes, and myocardial infarction—were associated with AF in the entire cohort but not in HF patients. In contrast, polymorphisms on chromosomes 16q22 and 4q25 were associated with AF both in the entire cohort and in HF patients, conferring 75% [95% confidence interval (CI) 35–126, P = 2 × 10−5] and 57% (95% CI 18–109, P = 0.002) increased risk of AF per copy in HF patients, respectively. In the entire cohort, AF risk in the presence of HF was multiplicatively magnified by genotype for 16q22 (P for interaction = 7 × 10−4) but not 4q25 (P = 0.83). In prospective analyses excluding patients with AF diagnosis prior to or simultaneously with HF diagnosis, 16q22 but not 4q25 remained robustly associated with AF (hazard ratio 1.96, 95% CI 1.40–2.73, P = 8 × 10−5). The proportion of AF diagnoses in HF patients attributable to polymorphisms was 19% and 12%, respectively. Conclusions A polymorphism in the ZFHX3 gene, encoding a cardiac transcription factor, was associated with increased AF risk in HF patients, and the genetic association with AF was more pronounced in HF patients than in the general population. [ABSTRACT FROM AUTHOR]

Background Even if atrial fibrillatory rate (AFR) has been related to clinical outcome in patients with atrial fibrillation (AF), its relation with ventricular response has not been deeply studied. The aim of this study was to investigate the relation between AFR and RR series variability in patients with AF. Methods Twenty-minute electrocardiograms in orthogonal leads were processed to extract AFR, using spatiotemporal QRST cancellation and time frequency analysis, and RR series in 127 patients (age 69 ± 11 years) with congestive heart failure (NYHA II-III) enrolled in the MUSIC study (MUerte Subita en Insufficiencia Cardiaca). Heart rate variability and irregularity were assessed by time domain parameters and entropy-based indices, respectively and their correlation with AFR investigated. Results Variability measures seem not to be related to AFR, while irregularity measures do. A significant correlation between AFR and variability parameters of heart rate variability during AF was found only in patients not treated with antiarrhythmics drugs (correlation = 0.56 P < 0.05 for pNN50), while this correlation was lost in patients taking rate- or rhythm-control drugs. A significant positive correlation between AFR and indices of RR irregularity was found, showing that a higher AFR is related to a less organized RR series (correlation = 0.33 P < 0.05 for regularity index for all patients, correlation increased in subgroups of patients treated with the same drug). Conclusions These results suggest that a higher AFR is associated with a higher degree of irregularity of ventricular response that is observed regardless of the use of rate-controlling drugs. [ABSTRACT FROM AUTHOR]

Increasing awareness of atrial fibrillation (AF) and its impact on public health revives interest in identification of noninvasive markers of predisposition to AF and ECG-based risk stratification. P-wave duration is generally accepted as the most reliable noninvasive marker of atrial conduction, and its prolongation has been associated with history of AF. However, patients with paroxysmal AF without structural heart disease may not have any impressive P-wave prolongation, thus suggesting that global conduction slowing is not an obligatory requirement for development of AF. P-wave morphology is therefore drawing increasing attention as it reflects the three-dimensional course of atrial depolarization propagation and detects local conduction disturbances. The factors that determine P-wave appearance include (1) the origin of the sinus rhythm that defines right atrial depolarization vector, (2) localization of left atrial breakthrough that defines left atrial depolarization vector, and (3) the shape and size of atrial chambers. However, it is often difficult to distinguish whether P-wave abnormalities are caused by atrial enlargement or interatrial conduction delay. Recent advances in endocardial mapping technologies have linked certain P-wave morphologies with interatrial conduction patterns and the function of major interatrial conduction routes. The value of P-wave morphology extends beyond cardiac arrhythmias associated with atrial conduction delay and can be used for prediction of clinical outcome of a wide range of cardiovascular disorders, including ischemic heart disease and congestive heart failure. [ABSTRACT FROM AUTHOR]

Interatrial frequency gradient is used to guide catheter ablation of atrial fibrillation (AF). Lead V1 adequately reflects right atrial activity, but reliable tools for noninvasive estimation of right versus left fibrillatory frequency are lacking. In this study, patients with dissociated left and right atrial rhythms were studied in order to identify which surface electrocardiographic (ECG) leads that most closely reflect the left atrial activity. Two consecutive patients with atrial tachycardia confined to the left atrial appendage (LAA) detected during catheter ablation of AF were included (2 men, 54 and 72 years old). A 12-lead ECG was recorded simultaneously with electrograms from the right and left atrial appendages (RAA/LAA). AF frequency spectra were calculated from all 12 leads using spatiotemporal QRST cancellation and Welch periodogram. The dominating atrial cycle length (DACL) in the surface ECG leads was subsequently compared with the invasively measured LAA cycle length. LAA activation frequency was seen as a prominent peak in the frequency-power spectrum derived from frontal plane leads as well as lead V1. The absolute difference in noninvasively and invasively measured LAA cycle length was lowest for leads aVR, II, aVF, III, and V1 in which it was in the range of 2-4 ms. Prominent left atrial component is present in the majority of standard ECG leads, including those traditionally associated with right atrial activity such as V1. Spectral analysis is able to extract the LAA component on surface ECG. (J Cardiovasc Electrophysiol, Vol. 22, pp. 706-710, June 2011) [ABSTRACT FROM AUTHOR]

Background: Several ECG-based approaches have been shown to add value when risk-stratifying patients with congestive heart failure, but little attention has been paid to the prognostic value of abnormal atrial depolarization in this context. The aim of this study was to noninvasively analyze the atrial depolarization phase to identify markers associated with increased risk of mortality, deterioration of heart failure, and development of atrial fibrillation (AF) in a high-risk population with advanced congestive heart failure and a history of acute myocardial infarction. Methods: Patients included in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) with sinus rhythm at baseline were studied (n = 802). Unfiltered and band-pass filtered signal-averaged P waves were analyzed to determine orthogonal P-wave morphology (prespecified types 1, 2, and 3/atypical), P-wave duration, and RMS20. The association between P-wave parameters and data on the clinical course and cardiac events during a mean follow-up of 20 months was analyzed. Results: P-wave duration was 139 ± 23 ms and the RMS20 was 1.9 ± 1.1 μV. None of these parameters was significantly associated with poor cardiac outcome or AF development. After adjustment for clinical covariates, abnormal P-wave morphology was found to be independently predictive of nonsudden cardiac death (HR 2.66; 95% CI 1.41–5.04, P = 0.0027) and AF development (HR 1.75; 95% CI 1.10–2.79, P = 0.019). Conclusion: Abnormalities in P-wave morphology recorded from orthogonal leads in surface ECG are independently predictive of increased risk of nonsudden cardiac death and AF development in MADIT II patients. Ann Noninvasive Electrocardiol 2010;15(1):63–72 [ABSTRACT FROM AUTHOR]

Background: Orthogonal P-wave morphology in healthy men and women has been described using unfiltered signal-averaged technique and holds information on interatrial conduction. The stability of P-wave morphology in healthy subjects over time is not fully known. Methods: Sixty-seven healthy volunteers were investigated (29 males, aged 63 ± 14 years, 48 females, 60 ± 13 years). Orthogonal lead data (X, Y, and Z) were derived from standard 12-lead ECGs (recording length 6 minutes, sampling rate 1kHz, resolution 0.625 μV) recorded at baseline (BL), and 3 years later at follow-up (FU). P waves were then signal-averaged and analyzed regarding P-wave morphology, locations of maxima, minima, zero-crossings, and P-wave duration (PWD). Results: No differences of P-wave variables were observed at FU compared to BL, including PWD (127 ± 12 vs 125 ± 14 ms at BL and FU, respectively, n.s.). In 59 of the 67 subjects (88%), the P-wave morphology was unaltered at FU. However, in the remaining eight cases a distinctively different morphology was observed. The most common change (P = 0.030) was from negative polarity to biphasic (−/+) in Lead Z (n = 5). In one case the opposite change was observed and in two cases transition into advanced interatrial block morphology was evident at FU. Conclusions: In the majority of healthy subjects, P-wave morphology is stable at 3-year FU. Subtle morphological changes, observed principally in Lead Z, suggest variation of interatrial conduction. These changes could not be detected by measuring conventional PWD that remained unchanged in the total population. [ABSTRACT FROM AUTHOR]

Background: Changes in P-wave morphology have recently been shown to be associated with interatrial conduction route used, without noticeable changes of P-wave duration. This study aimed at exploring the association between P-wave morphology and future atrial fibrillation (AF) development in the Multicenter Automatic Defibrillator Trial II (MADIT II) population. Methods: Patients included in MADIT-II without a history of AF with sinus rhythm at baseline who developed AF during the study (“Pre-AF”) were compared to matched controls without AF development (“No-AF”). Patients were followed for a mean of 20 months. A 10-minute high-resolution bipolar ECG recording was obtained at baseline. Signal-averaged P waves were analyzed to determine orthogonal P-wave morphology, P-wave duration, and RMS20. The P-wave morphology was subsequently classified into one of three predefined types using an automated algorithm. Results: Thirty patients (age 68 ± 7 years) who developed AF during MADIT-II were compared with 60 patients (age 68 ± 8 years) who did not. P-wave duration and RMS20 in the Pre-AF group was not significantly different from the No-AF group (143 ± 21 vs 139 ± 30 ms, P = 0.26, and 2.0 ± 1.3 vs 2.1 ± 1.0 μV, P = 0.90). The distribution of P-wave morphologies was shifted away from Type 1 in the Pre-AF group when compared to the No-AF group (Type 1/2/3/atypical; 25/60/0/15% vs 10/63/10/17%, P = 0.04). Conclusions: This study is the first to describe changes in P-wave morphology in patients prior to AF development. The results indicate that abnormal interatrial conduction may play a role in AF development in patients with prior myocardial infarction and congestive heart failure. [ABSTRACT FROM AUTHOR]

Background: Shortening of the atrial refractory period is the key feature of atrial electrical remodeling during atrial fibrillation (AF). During sinus rhythm (SR), assessment of the atrial refractoriness is hampered by the fact that the atrial repolarization wave (Ta wave) is largely obscured by the following QRST complex. The purpose of this study was to study the Ta wave in subjects with paroxysmal AF during SR with third-degree atrioventricular (AV) block, and in matched controls. Methods: Fifteen patients (mean age 70 ± 10 years, five males) with paroxysmal AF undergoing AV-nodal ablation were studied. Fifteen age- and gender-matched subjects (mean age 71 ± 9 years, five males) with third-degree AV block, without a history of heart disease, were used as controls. Standard 12-lead electrocardiograms (ECGs) were recorded and transformed to orthogonal leads and studied using P-wave signal averaging technique. Results: The P to Ta interval was shorter (408 ± 47 ms vs 451 ± 53 ms, P = 0.017) and in Lead Y the Ta peak location was earlier (156 ± 31 ms vs 187 ± 34 ms, P = 0.002) in subjects with paroxysmal AF than in the controls. The P-wave duration (126 ± 15 ms vs 129 ± 17 ms, P = 0.59) and morphology was similar in AF patients and controls. Conclusions: In this study, the ECG signs of shorter atrial refractoriness associated with a history of AF are visualized for the first time during SR. The finding of the earlier location of the PTa peak in AF subjects implies that a possible indicator of increased arrhythmia susceptibility may be visible already in the unprocessed ECG. [ABSTRACT FROM AUTHOR]

Introduction: Data on human atrial repolarization are scarce since the QRS complex normally obscures its ECG trace. In the present study, consecutive patients with third-degree AV block were studied to better describe the human Ta wave. Methods and Results: Forty patients (mean age 75 years, 17 men) were included. All anti-arrhythmic drugs were discontinued before ECG recording. Standard 12-lead ECGs were recorded, transformed to orthogonal leads and studied using signal-averaged P wave analysis. The average P wave duration was 124 ± 16 ms. The PTa duration was 449 ± 55 ms (corrected PTa 512 ± 60 ms) and the Ta duration (P wave end to Ta wave end) was 323 ± 56 ms. The polarity of the Ta wave was opposite to that of the P wave in all leads. The Ta peaks were located at 196 ± 55 ms in Lead Y, 216 ± 50 ms in Lead X, and 335 ± 92 in Lead Z. No correlation was found between P wave duration and Ta duration, or between Ta peak amplitude and Ta duration. The morphology of the Ta wave was similar regardless of the interatrial conduction. Conclusions: The Ta wave has the opposite polarity, and the duration is generally two to three times that, of the P wave. Although the Ta peak may occasionally be located in the PQ interval during normal AV conduction, it is unlikely that enough information can be obtained from analysis of this segment to differentiate normal from abnormal atrial repolarization. Hence, an algorithm for QRST cancellation during sinus rhythm is needed to further improve analysis. [ABSTRACT FROM AUTHOR]

Introduction: Radiofrequency ablation of atrial fibrillation (AF) is associated with energy delivery on the posterior left atrial (LA) wall with small but significant risk of life-threatening complications. Anatomy of LA walls has been described, but wall thickness in patients with AF has not been studied systematically. The aim of the present study was to describe LA posterior wall thickness in patients with and without history of AF. Methods and Results: Heart mass and LA wall thickness was measured during 298 consecutive autopsies (142 male, age 61 ± 17 years). LA posterior wall was measured at three levels: between the superior pulmonary veins (SPV), in the center of the posterior LA wall (CPV), and between the inferior pulmonary veins (IPV). Information about AF history was obtained from medical records. Fifty-nine subjects (20%) had documented AF. They were older than subjects without AF (74 ± 10 years vs 58 ± 17 years, P < 0.0001) and had greater heart mass (522 ± 114 g vs 389 ± 99 g, P < 0.0001). LA posterior wall thickness increased from the most superior to the most inferior measured level (2.3 ± 0.9 mm vs 2.5 ± 1.0 mm vs 2.9 ± 1.3 mm for SPV, CPV, and IPV, respectively; P < 0.001). Subjects with AF history had thinner LA posterior wall at CPV and IPV compared with those without AF. Conclusions: LA posterior wall thickness is described on a large series of consecutive autopsies. LA posterior wall is found to be generally thinner in patients with history of AF. Study results have clinical implications for understanding complication risk and improvement of safety of AF ablation procedures. [ABSTRACT FROM AUTHOR]

Background: Atrial fibrillation (AF) is a common problem in pacemaker patients. We conducted a prospective observational study in patients paced for bradycardia with associated paroxysmal or persistent AF, to determine whether P-wave duration may stratify patients at higher risk for AF recurrences and AF-related hospitalizations. The patients were evaluated for the prevalence, cause, and predictors of hospitalization. Methods: We studied 660 consecutive patients (50% male, 72 ± 9 years) who received a dual-chamber pacemaker. Median value of baseline P-wave duration was equal to 100 ms (25%–75% quartile range equal to 80–120 ms). We used this cut-off to divide the patients into group A (P ≤ 100 ms), composed of 385 (58.3%) patients, and group B (P>100 ms), composed of 275 (41.7%) patients. Results: In a median follow-up of 19 months, 173 patients were hospitalized for all causes, 130 for cardiovascular causes, and 85 for AF-related hospitalizations. Multivariate logistic analysis showed that P-wave duration >100 ms identified patients at higher risk (OR = 1.6, 95% confidence interval (1.1–2.8), P = 0.044) for AF-related hospitalizations. Patients in group B (P > 100 ms) more frequently suffered AF-related hospitalizations (16.4% vs 10.4%, P = 0.02) and underwent more frequent cardioversions (14.5% vs 9.1%, P = 0.029) compared with group A (P ≤ 100 ms). Conclusions: P-wave duration may define the risk of persistent AF requiring cardioversion or AF-related hospitalization in patients with a pacemaker for bradycardia with associated paroxysmal or persistent AF. [ABSTRACT FROM AUTHOR]

Background: Patients with hypertrophic cardiomyopathy (HCM) have a high incidence of atrial fibrillation. They also have a longer P-wave duration than healthy controls, indicating conduction alterations. Previous studies have demonstrated orthogonal P-wave morphology alterations in patients with paroxysmal atrial fibrillation. In the present study, the P-wave morphology of patients with HCM was compared with that of matched controls in order to explore the nature of the atrial conduction alterations.Methods and Results: A total of 65 patients (45 men, mean age 49 +/- 15) with HCM were included. The control population (n = 65) was age and gender matched (45 men, mean age 49 +/- 15). Five minutes of 12-lead ECG was recorded. The data were subsequently transformed to orthogonal lead data, and unfiltered signal-averaged P-wave analysis was performed. The P-wave duration was longer in the HCM patients compared to the controls (149 +/- 22 vs 130 +/- 16 ms, P < 0.0001). Examination of the P-wave morphology demonstrated changes in conduction patterns compatible with interatrial conduction block of varying severity in both groups, but a higher degree of interatrial block seen in the HCM population. These changes were most prominent in the Leads Y and Z.Conclusion: The present study suggests that the longer P-wave duration observed in HCM patients may be explained by a higher prevalence of block in one or more of the interatrial conduction routes. [ABSTRACT FROM AUTHOR]

The author reflects on the role played by rate modulation drugs in atrial fibrillation (AF). Topics discussed include effect of four rate-control drugs on variability as well as irregularity of RR intervals or heart rate in permanent AF patients, significance of RR interval irregularity as predictability/pattern of variation of RR intervals, and use of rate control medications in improving the prognosis of the patients in AF. It mentions the use of β-blockers for management of arrhythmia.

Background: Abnormal P-wave morphology (PWM) has been associated with a history of atrial fibrillation (AF) in earlier studies. Although lone AF is believed to have substantial genetic basis, studies on associations between single nucleotide polymorphisms (SNP) linked to lone AF and PWM have not been reported. We aimed to assess whether SNPs previously associated with lone AF (rs2200733, rs13376333, rs3807989, and rs11047543) are also linked to P-wave abnormalities.Methods: Four SNPs were studied in 176 unrelated individuals with early-onset lone AF (age at onset <50 years), median age 38 years (19-63 years), 149 men. Using sinus rhythm ECG, orthogonal PWM was classified as Type 1-positive in leads X and Y and negative in lead Z, Type 2-positive in leads X and Y and biphasic (-/+) in lead Z, Type 3-positive in lead X and biphasic in lead Y (+/-), and the remaining as atypical.Results: Two SNPs were found to be significantly associated with altered P-wave morphology distribution: rs3807989 near the gene CAV1/CAV2 and rs11047543 near the gene SOX5. Both SNPs were associated with a higher risk of non-Type 1 P-wave morphology (rs3807989: OR = 4.8, 95% CI = 2.3-10.2, p < 0.001; rs11047543: OR = 4.7, 95% CI = 1.1-20.5, p = 0.04). No association was observed for rs2200733 and rs13376333.Conclusion: In this study, the two variants rs3807989 and rs11047543, previously associated with PR interval and lone AF, were associated with altered P-wave morphology distribution in patients with early-onset lone AF. These findings suggest that common genetic variants may modify atrial conduction properties. [ABSTRACT FROM AUTHOR]

Background: Primary prophylactic implantable cardioverter defibrillator (ICD) therapy is indicated for patients with reduced left ventricular ejection fraction (LVEF). We aimed to determine if preoperative clinical risk profiling can predict long-term benefit, and if clinical risk scores can be applied and improved in a patient cohort outside the clinical trial setting.Methods: Using registry data, 789 patients with reduced LVEF who received ICDs for primary prevention during 2006-2011 were identified (age 64 ± 11 years, 82% men, 63% ischemic etiology, 52% cardiac resynchronization therapy with defibrillator). The patients were divided into three risk groups, based on the presence of baseline clinical risk factors (age >70, QRS duration >120 ms, New York Heart Association class III-IV, atrial fibrillation history, or creatinine >106 μmol/L). Endpoints were all-cause mortality and survival free of adequate ICD therapy.Results: Mean follow-up was 39 ± 18 months. Annual mortality was 7.6%, and increased with risk group (p < .001). Rates of appropriate antitachycardia pacing and shock therapy were not statistically different between the groups, and ranged from 11%-16% and 6%-14%, respectively. By combining the previous risk score with data on diabetes, a better independent prediction of mortality was achieved; mortality rates then ranged from 11% (low-risk) to 46% (high-risk) (p < .0001).Conclusions: Implantable cardioverter defibrillator therapies occur across the spectrum of comorbidities in a population with systolic heart failure. However, all-cause mortality is considerably higher in the group of patients with accumulated risk factors, and using the proposed scoring system can be helpful for the evaluation and risk stratification of the patient prior to making a decision for a primary prophylactic ICD implantation. [ABSTRACT FROM AUTHOR]

Conduction Along the Coronary Sinus. Introduction: Correlation function analysis was applied to endocardial electrograms to investigate conduction patterns along the coronary sinus (CS) during sinus rhythm (SR) and atrial tachycardias. Methods and Results: Eighteen recordings were obtained from 14 patients with supraventricular tachycardias. Five atrial fibrillation (AF) recordings were compared to 10 SR recordings and 3 ectopic atrial tachycardia (EAT) recordings. The maximum correlation coefficient was used to assess similarity between signals, i.e., if they originate from the same wavefront. The cumulative time delay, calculated as pairwise summation of interelectrode time delays, was used as an indicator of activation sequence along the CS. Method validation using SR showed right-to-left conduction with high correlations in 8 of 10 recordings indicating one single wavefront. EAT recordings showed consistent left-to-right conduction with left atrial foci and right-to-left with right atrial focus and lower correlations than SR. All 5 AF recordings showed predominantly left-to-right conduction direction, also with correlations lower than SR. Conclusion: (1) Correlation function analysis can be used to assess agreement between signals and direction of activation spread. (2) Due to the position of CS, the results can be used to derive mechanisms of interatrial conduction. (3) Consistency in electrical activity propagation along CS is common in AF. (J Cardiovasc Electrophysiol, Vol. 14, pp. S148-S153, October 2003, Suppl.) [ABSTRACT FROM AUTHOR]

Background: The ABC-stroke score is a risk scheme for prediction of stroke or systemic embolism (SE) in atrial fibrillation (AF). This study sought to examine whether the score could be useful in predicting stroke in AF-naïve individuals and risk stratifying for AF screening., Methods and Results: The LOOP (Atrial Fibrillation Detected by Continuous ECG Monitoring Using Implantable Loop Recorder to Prevent Stroke in High-Risk Individuals) study randomized 6004 AF-naïve individuals aged 70 to 90 years with stroke risk factors to either screening with an implantable loop recorder and anticoagulation upon detection of new-onset AF episodes ≥6 minutes, or usual care. A total of 5781 participants had available ABC-stroke score at baseline and were included in this secondary analysis: 4170 (72.1%) with an estimated stroke/SE risk ≤1%/year versus 1611 (27.9%) with an estimated stroke/SE risk >1%/year. Having an annual ABC-stroke risk >1% was associated with stroke/SE, stroke/SE/cardiovascular death, and all-cause death (hazard ratio, 1.82 [95% CI, 1.44-2.21], 2.17 [95% CI, 1.80-2.62], and 2.19 [95% CI, 1.87-2.56], respectively). For screening with implantable loop recorder versus usual care, no significant reduction in these study outcomes was obtained in any ABC-stroke risk groups ( P >0.0500 for all), with no signal toward interaction ( P interaction >0.2500 for all). Similar findings were yielded when assessing the ABC-stroke score as a continuous variable., Conclusions: In an elderly, AF-naïve population with additional stroke risk factors, a higher ABC-stroke score could identify individuals with increased stroke risk. However, this risk score may not be useful in pinpointing those more likely to benefit from AF screening and subsequent preventive treatment. These findings should be considered as hypothesis generating and warrant further study., Registration: URL: https://www.clinicaltrials.gov; unique identifier: NCT02036450.