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Aims Studies have demonstrated shortening of the atrial effective refractory period (ERP) after episodes of atrial fibrillation (AF). This is termed atrial remodelling. It is unclear whether restoration of SR after persistent AF in patients with a clinical substrate results in reversal of this shortening and whether this is maintained long term. Methods and results The ERP was determined at mid-lateral right atrial wall (MLRA) and right atrial appendage (RAA) at 600 ms and 400 ms drive cycle lengths and at basic sinus cycle length in 81 patients with persistent AF immediately, 24 h and 2 weeks following external DC cardioversion. All atrially active drugs were stopped for at least 5 half lives. (1) Prolongation of the ERP was observed at both atrial sites and all cycle lengths up to 24 h post cardioversion ( p

Single site left ventricular (LV) pacing in the absence of intrinsic ventricular activity can be as detrimental to LV function as right ventricular apical pacing. This report describes a patient with complete heart block who developed significant dyssynchrony and cardiomyopathy secondary to single site lateral LV pacing. The process was reversed by placement of a second anterior LV lead. (PACE 2013; 36:e35–e37)

The purpose of this study was to determine the changes in atrial electrophysiology associated with chronic persistent atrial fibrillation in man.Atrial monophasic action potential duration at 90% repolarization and the effective refractory period were measured in 13 patients with chronic persistent atrial fibrillation after low-energy endocardial cardioversion, and compared to eight controls without a history of atrial fibrillation. Measurements were made at the right atrial appendage and midlateral right atrial wall at basic, 600 ms and 400 ms drive cycle lengths. In control patients, the effective refractory periods were significantly longer at the atrial appendage than the lateral wall at 600 ms (right atrial appendage 265 ms, midlateral right atrial wall 228 ms, P0.05), and 400 ms cycle lengths (right atrial appendage 270 ms, midlateral right atrial wall 218 ms, P0.05), but this was not evident in patients with atrial fibrillation. The monophasic action potentials and effective refractory periods at both atrial sites were shorter in the atrial fibrillation patients compared to controls; however, only the effective refractory periods at atrial appendage at 600 ms (atrial fibrillation 210 ms, controls 265 ms, P0.001), and 400 ms cycle lengths (atrial fibrillation 200 ms, controls 270 ms, P0.001) reached statistical significance. Effective refractory period dispersion was significantly greater in controls than in patients with atrial fibrillation (cycle length 600 ms: controls 36, atrial fibrillation 13, P=0.01; cycle length 400 ms: controls 54, atrial fibrillation 18, P0.01).In patients without a history of atrial fibrillation, the refractory period at the right atrial appendage is significantly longer than at the midlateral right atrial wall. This 'normal' pattern of atrial refractory dispersion is lost in patients with chronic persistent atrial fibrillation, with marked shortening of the effective refractory period at the right atrial appendage. This may explain the high risk of recurrence of atrial fibrillation following successful electrical cardioversion.

Objectives. We sought 1) to compare three pacing modalities—DDDR with mode switching (DM), DDDR with conventional upper rate behavior (DR) and VVIR (VR)—in patients with a history of atrial tachyarrhythmias, and 2) to assess the efficacy of six mode-switching algorithms.Background. A history of atrial tachyarrhythmias has been a relative contraindication to dual-chamber pacing. Several mode-switching algorithms have recently been developed to prevent rapid tracking of atrial tachyarrhythmias.Methods. Forty-eight patients (mean age 64 years, 58% male) with a history of atrial tachyarrhythmias and heart block had a DM pacemaker implanted. Pacemakers were programmed to DM, DR and VR modes for 4 weeks each in a randomized crossover design. All subjects used a patient-activated electrocardiographic (ECG) recorder throughout the study and additionally underwent ambulatory ECG monitoring and a treadmill exercise test in each mode. They completed three symptom questionnaires at the end of each pacing period. At the end of the study, patients chose their preferred pacing period.Results. DM was significantly better than VR mode objectively (exercise time DM 8.1 min, VR 7.0 min, p < 0.01) and subjectively (perceived well-being DM 69, VR 51, p < 0.001; functional class DM 2.2, VR 2.5, p < 0.05; subjective symptom score DM 21.2, VR 26.8, p = 0.01). Patient-perceived well-being was significantly better with DM than with DR mode (DM 69, DR 60, p = 0.02). DM mode was the preferred pacing period (DM 51%, DR 14%, VR 14%). Early termination of pacing because of adverse symptoms was requested by 33% of patients during VR, 19% during DR but only 3% during DM mode. A higher proportion of patients with a fast mode-switching device preferred DM mode (fast 55%, slow 49%), whereas no patients with a fast mode-switching device chose VR as the preferred mode (fast 0%, slow 19%). In the subgroup of patients who had had atrioventricular node ablation, DM was also preferred to VR mode (DM 53%, VR 27%). Overall, there were only two cases of inappropriate mode switching and one case of inappropriate tracking of an atrial tachyarrhythmia.Conclusions. DM is the pacing mode of choice of patients with paroxysmal atrial tachyarrhythmias. With optimal programming, inappropriate mode switching and tracking of atrial tachyarrthmias was very uncommon.

A wrist-applied transtelephonic device (WrTTD) and a precordial (PrTTD) patient-activated transtelephonic electrocardiographic (ECG) recorder were compared objectively (quality of ECG traces) and subjectively (device preference) in a prospective randomized crossover study of 24 patients. All underwent cardioversion for chronic atrial fibrillation and were then randomized to each device for 1 month. The ECG traces were sent weekly with additional traces if symptomatic. Self-administered questionnaires were completed after 1 month with each device, and the first five telemetered ECG traces for each patient were blindly assessed by two experienced cardiologists. Although the QRS complexes were smaller with the WrTTD (P < .001), the quality of the traces was similar. In particular, there was no significant difference in number of nondiagnostic traces, ability to detect atrial activity, degree of baseline fluctuation, or amount of artifact. Overall, patients preferred the PrTTD (P = .02). Patients found the PrTTD easier to use (P = .007) and were able to apply it more rapidly (P = .02). The quality of ECG traces obtained from the upper limbs by using a wrist-applied transtelephonic device was concluded to be comparable with those obtained by direct precordial application. In order to increase patient acceptability of the former, further improvements to simplify its operation are necessary.

Single site left ventricular (LV) pacing in the absence of intrinsic ventricular activity can be as detrimental to LV function as right ventricular apical pacing. This report describes a patient with complete heart block who developed significant dyssynchrony and cardiomyopathy secondary to single site lateral LV pacing. The process was reversed by placement of a second anterior LV lead.

The aim of this study was to determine the effect of early patient activated cardioversion of atrial fibrillation (AF) using the atrial defibrillator on recurrence of AF. Fifteen patients, mean age 63 ± 14 years, 80% men, with drug-resistant persistent AF were implanted with the Jewel AF atrial defibrillator. All patients performed self-administered cardioversion for AF recurrences. Over a 2 year follow-up, 238 patient-activated cardioversions were performed in 14 patients. Sinus rhythm was restored on every occasion with 96% of episodes terminating with a single shock. The median time from AF onset to patient awareness of symptoms was 2.5 hours. The median time from onset of symptoms to cardioversion was 3.5 hours. Comparison of the first and second six month period following implant showed a nonsignificant increase in mean total AF duration (75.7 ± 107.8 hours vs 146.6 ± 194.1 hours, P = 0.28). Two patients (13%) had a decreasing frequency of AF recurrences. The majority continued to have regular recurrences of AF. The atrial defibrillator is an extremely effective method of restoring sinus rhythm in patients with persistent AF. Regular early use of the atrial defibrillator, increased the duration of sinus rhythm in a minority of patients during long-term follow-up. Most patients had regular recurrences of AF requiring patient-activated cardioversion. (PACE 2004; 27:175–181)

The purpose of this study was to assess the efficacy of overdrive, single-site right atrial appendage pacing to reduce the burden of atrial fibrillation (AF) when compared with a standard lower rate limit of 60 bpm. This was verified by using the pacemaker's Holter. Eighteen subjects with a pre-implant history of paroxysmal AF and implanted DDDR mode-switching pacemakers were recruited. The pacemaker lower rate limit was programmed in random order to 60, 75 or 90 bpm for three 2-month periods and the amount of AF quantified. In addition, the exercise tolerance (ET), general well being (GWB), functional capacity (FC) and specific symptom prevalence (SSP) were assessed. The main finding of the study was that when ranked according to the amount of AF, there was no significant difference in the amount of AF according to the pacing rate. Six patients failed to tolerate pacing at 90 bpm. There were no differences in the ET, GWB, FC and SSP scores. It is concluded that those clinicians that manage patients with paroxysmal

Dual sensor ventricular demand rate responsive (VVIR mode) pacing was compared with single sensor rate responsive pacing to assess whether this new development should be more widely incorporated in modern pacemaker devices. A within patient randomized, double-blind crossover study involving ten patients, mean age 67.4 years (70% male), had Medtronic Legend Plus dual sensor VVIR pacemakers implanted for high grade AV block and chronic or persistent paroxysmal atrial fibrillation. Performance values were compared to 20 healthy control subjects of a similar age and gender. Patients were both subjectively and objectively assessed after 2 weeks of out-of-hospital activity in VVIR mode (minute ventilation sensing), VVIR mode (activity sensing), VVIR mode (dual sensor), and VVI mode (no rate response). All patients were assessed for subjective preference for, and objective improvement in, any pacing modality as assessed by standardized daily activity protocols and graded exercise treadmill testing. Subjective perception of exercise capacity and functional status was significantly lower in VVI mode (P < 0.05) compared to any of the VVIR modes, which did not differ. After completion of the study 70% of patients chose VVIR as their preferred mode, with 30% expressing no preference. Forty percent preferred activity sensor VVIR mode pacing, 30% preferred dual sensor VVIR mode pacing, and 70% found either dual sensor VVIR mode, minute ventilation sensor VVIR mode, or both modalities least acceptable. No patient found activity sensing VVIR mode least acceptable. Graded treadmill testing revealed significantly lower exercise tolerance during VVI mode pacing (P < 0.01) compared to the VVIR modalities, which did not differ. Overall, chronotropic response was best with dual sensor pacing during standardized daily activity protocols and during the standard car journey. The data from this study suggest that there is no marked clinical advantage obtained from the use of dual sensor devices over current activity sensing ventricular demand rate responsive pacemakers, but with the probable added disadvantages of increased size, complexity, cost, and decreased longevity.

Pacemakers are becoming increasingly sophisticated, offering a host of new diagnostic functions. This case illustrates how some of these functions can be used to help with the diagnosis and management of patients with pacemakers who suffer from cardiac arrhythmias.

The new SMARTracking (SMT) algorithm was evaluated in seven patients with the Intermedics Relay DDDE pacemakers and a history of atrial tachyarrhythmias. The SMT algorithm uses the sensor calculated rate to define a physiological band whose upper limit is defined by the SMT rate. Pacemakers were programmed to DDDR with SMT (DDDRSM), DDDR with Conditional Ventricular Tracking Limit (DDDRC), DDDR with standard upper rate behavior, and VVIR, for a period of one month each. Patients underwent a CAEP exercise test and 24-hour ECG Holter monitoring in each mode. They also had ambulatory ECG monitoring during daily activities including rest, slow and fast walk, stairs ascent and descent. Three patients were in atrial fibrillation during the daily activities protocol. Their ventricular rates were paced and highly irregular, in both DDDRSM and DDDRC modes. The heart rate was lower in DDDRSM than DDDRC at rest and low levels of exercise but not during more strenuous activity. Two patients in DDDRSM and 3 in DDDRC requested early change of their mode due to unacceptable symptoms. Two patients exhibited Wenckebach behavior at atrial rates below the upper rate limit in both DDDRSM and DDDRC modes. In conclusion, CVTL or SMARTracking are not adequate protection against atrial tachyarrythmias in patients with DDDR pacemakers.