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Current guidelines recommend 4 weeks of private driving restriction after implantation of a primary-prevention implantable cardioverter-defibrillator (ICD). These driving restrictions result in significant inconvenience and social implications. Advances in medical treatment and ICD programming have lowered the overall rate of device therapies. The objective of this study was to assess the incidence of ICD therapies at 30, 60, and 180 days after implantation.Driving Restrictions and Early Arrhythmias in Patients Receiving a Primary-Prevention Implantable Cardioverter-Defibrillator (DREAM-ICD) was a retrospective cohort study conducted at 2 Canadian university centres enrolling patients with new implantation of a primary-prevention ICD. Device programming was standardised according to current guidelines. A total of 803 patients were enrolled.The cumulative rates of appropriate ICD therapies at 30, 60, and 180 days were 0.12%, 0.50%, and 0.75%, respectively. There was no syncope during the first 6 months. The median duration to the first appropriate ICD therapy was 208 (range 23-1109) days after implantation. The rate of inappropriate ICD therapies at 30 days was only 0.2%. Overall,13.6% of all appropriate ICD therapies occurred within the first 6 months after implantation.The rate of appropriate ICD therapies within the first 30 days after device insertion is extremely low in contemporary primary prevention cohorts with guideline-concordant device programming. There was no increased risk for ventricular arrhythmia early after ICD insertion. The results of DREAM-ICD suggest the need for a revision of the existing driving restrictions for primary-prevention ICD recipients.

BACKGROUND Following an unexplained cardiac arrest, patients and family members typically undergo a comprehensive series of investigations to identify the underlying cause of arrest, with a diagnosis identified in more than half of cardiac arrest survivors. However, the long-term arrhythmic outcomes among cardiac arrest survivors remains unclear. METHODS AND RESULTS The Cardiac Arrest Survivors with Preserved Ejection Fraction Registry (CASPER) prospectively enrolls cardiac arrest survivors and their first-degree relatives (FDR) across 16 Canadian centers. Patient demographics, cardiac investigations, working diagnoses, and follow-up events are recorded. Those with a history of significant coronary artery disease or manifest cause of cardiac arrest are excluded. Arrhythmic events, including implantable cardioverter-defibrillator (ICD) shock or anti-tachycardia pacing (ATP) are recorded. Patients with at least one follow-up visit were included. Hazard ratios for arrhythmic events were calculated using Cox proportional hazards models. 741 patients were enrolled, with a median age of 42 years (interquartile range [IQR] 29-53), 56% being male, and mostly Caucasian (82%). Patients included cardiac arrest suvivors/probands (n=480, 66%) and first-degree relatives (n=243, 34%). In addition to baseline investigations, patients undertook signal-averaged ECG (56%), exercise testing (70%), extended monitoring (50%), cardiac MRI (62%), and provocative testing with procainamide (39%), adrenaline (31%) or an electrophysiologic study (14%). After excluding 18 patients with ongoing diagnosis adjudication, the working diagnoses of probands and FDRs are reported in the Table. Working diagnoses among probands were divided into three categories, including unexplained/idiopathic (after comprehensive investigations, n=351), structural/cardiomyopathy (including arrhythmogenic right ventricular cardiomyopathy and others, n=64), and electrical/channelopathy (including Long QT Syndrome, Brugada Syndrome, and others, n=65). During a median follow-up of 3.3 years (IQR 1.7-5.9), 69 patients (9%) suffered an ICD shock or ATP with a median time-to-event of 1.0 years (IQR 0.5-2.8). Probands had a significantly higher rate of events (hazard ratio [HR] 16.9, 95% confidence interval [CI] 4.1-69.0, p CONCLUSION In a cohort of unexplained cardiac arrest survivors and first-degree relatives, probands had a significant rate of recurrent events. Probands with structural/cardiomyopathy diagnoses had twice the risk of arrhythmia recurrence. Patients with structural diagnoses may be more likely to have arrhythmic events in follow-up, potentially due to a progressive disease process compared to other diagnoses.

BACKGROUND In patients with refractory atrial fibrillation (AF) rate control strategy, atrioventricular node (AVN) ablation and permanent pacemaker implantation is recommended. The Micra Transcatheter Pacing System (TPS) is a single chamber leadless pacemaker implanted from the femoral vein and thus offers the possibility of AVN ablation in the same procedure. Here, we describe two cases of acute Micra TPS ventricular pacing threshold elevation immediately following radiofrequency AVN ablation at distance from the TPS requiring device retrieval and re-implantation of new Micra systems. METHODS AND RESULTS All consecutive patients with a Micra TPS implantation, at a single center, from November 2014 to March 2020, were analyzed retrospectively (n=56). Among them, 36% had a prior complication from a transvenous implant and in 16% lead extraction was performed concurrently with the TPS implantation. A total of ten patients (18%) underwent AVN ablation within the same procedure. Among them, two (20%) presented acute increase in the right ventricular pacing threshold after radiofrequency delivery requiring retrieval of the initial TPS and deployment of a new device. The first case was a 48 years-old man with previous heart transplantation. A Micra TPS was implanted in a mid-septal position (threshold 0,5 Volts x 0,24 milliseconds; impedance 800 Ohms; correct pull and hold test). To obtain a complete atrioventricular block, a retrograde arterial approach with an 8 mm nonirrigated catheter (60 degrees Celsius for 294 seconds) was required. After RF delivery, a loss of capture was observed. The second case included a 69 years-old woman. The TPS was implanted at an apico-septal position (Threshold 0,75 Volts x 0,24 milliseconds; impedance 720 Ohms; correct pull and hold test). The AVN ablation was achieved (52 degrees Celsius for 136 seconds) with a 4 mm nonirrigated catheter. Immediately, a threshold elevation >2 Volts x 0,24 milliseconds was observed. In both cases, continuous fluoroscopic control confirmed no direct interaction between the ablation catheter and the TPS. The device was successfully recaptured, and a new leadless PPM was immediately implanted with good results in these two cases. CONCLUSION We described two cases of acute threshold elevation during a combined procedure of TPS implantation and AVN ablation. This complication was not reported in series assessing safety of combining AVN ablation and Micra TPS implantation. We hypothesize a possible shunt of current to the distal electrode. An in vitro study is currently underway to explain the mechanism of indirect interaction between radiofrequency delivery and Micra TPS dysfunction.

Inherited heart rhythm disorders (IHRDs) are complex and uncommon arrhythmogenic conditions that can lead to sudden unexpected death in seemingly healthy individuals. Multidisciplinary programs can assist in the diagnostic testing of potentially affected individuals and their family members.Patients evaluated in a specialized adult and pediatric IHRD clinic between April 2013 and February 2015 were characterized. The total costs per evaluation and diagnosis were calculated. Patients were divided according to referral indication (primary referral or family member).A total of 618 patients were evaluated (age 36 ± 21 years; 52% male), of which 274 (44%) were primary referrals and 344 (56%) were family members referred for cascade screening. Overall, 47% had at least 1 follow-up visit. Patients had a median of 3 tests; primary referrals required more tests (4 vs 2; P0.01). The median cost per patient was $1340 CAD. Evaluation of the primary referrals was costlier than family members ($3096 vs $983; P0.01). A definite or probable diagnosis was determined in 464 patients (77%), with no difference according to patient type (P = 0.18). The total cost per diagnosis was $4021 in primary referrals compared with $1277 in family members (P0.01).Clinical evaluation of patients with suspected IHRD results in a high diagnostic yield and costs aligned with other complex disorders involving multidisciplinary clinics. Evaluation costs are expectedly higher in primary referrals compared with targeted family screening.

BACKGROUND: Patients with PMs or ICDs may be exposed to significant electromagnetic fields (EMF) from high voltage transmission lines (HVTL), which may interact with their device. To our knowledge, the rate of electromagnetic interference (EMI) has not been quantified nor have the circumstances of these EMIs. These were the objectives of the current registry. METHOD: Between February 2012 and March 2014, 18 296 device interrogations from patient visits to the PM/ICD clinic were reviewed (11 640 from PMs and 6 656 from ICDs). Fifty patients were recruited after noise episodes were seen during a routine follow-up interrogation. Only 10% of patients with noise episodes refused recruitment in the registry. Recruited patients were asked to keep a detailed log of their activities and travels. Their devices were then re-interrogated after 1, 4 and 12 weeks. Noise events registered on the devices interrogated in the PM/ICD clinic were correlated with a geographical map of the EMFs created by HVTLs, provided by Hydro-Quebec, the province of Quebec’s hydroelectric producer. RESULTS: Two patients were lost to follow-up. Of the remaining 48, 25 had further interference episodes for a total number of 1,080 episodes. Of these, 985 (91.2%) took place at home, 76 (7.1%), during an unknown activity (no activity recorded in the patient log at the time of the interference) and 19 (1.8%), during travels where a HVTL was identified in the vicinity. All of these travels, but one, were in motor vehicles which acted as a Faraday cage and shielded the patients and device from the electric field generated by the HVTLs. No episode was associated with a movement directly under a HVTL, on foot. There was no difference in the morphology of the noise signals based on the type of activity. A single inappropriate mode switch was noted as a result of the noise episodes. There was no relation between patient reported symptoms and the noise episodes. CONCLUSION: The overall rate of EMI is very low (0.3%) and the majority of episodes occur in the home environment. Despite the large number of patients sampled, there were no episodes of EMI linked to passage under a HVTL, which is reassuring from a public safety standpoint.

Accurate sensing of malignant arrhythmia is critical for the appropriate delivery of therapy from implantable cardioverter defibrillators, and undersensing of ventricular tachyarrhythmias can have catastrophic consequences. Here, we present an unusual case of ventricular fibrillation undersensing from the right ventricular lead at multiple different implantation sites because of very low amplitude voltage signals during induced ventricular fibrillation. A left ventricular sensing electrode was implanted to allow correct sensing and therapy delivery.