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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 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.

Sudden cardiac death is a major public health issue in Canada. However, despite the overwhelming evidence to support the use of implantable cardioverter defibrillators (ICDs) in the prevention of cardiac death there remains significant variability in implantation rates across Canada. Since the most recent Canadian Cardiovascular Society position statement on ICD use in Canada in 2005, there has been a plethora of new scientific information to assist physicians in their discussions with patients considered for ICD implantation to prevent sudden cardiac death due to ventricular arrhythmias. We have reviewed, critically appraised, and synthesized the pertinent evidence to develop recommendations regarding: (1) ICD implantation in the primary and secondary prevention of sudden cardiac death in patients with and without ischemic heart disease; (2) when it is reasonable to withhold ICD implantation on the basis of comorbidities; (3) ICD implantation in patients listed for heart transplantation; (4) implantation of a single- vs dual-chamber ICD; (5) implantation of single- vs dual-coil ICD leads; (6) the role of subcutaneous ICDs; and (7) ICD implantation infection prevention strategies. We expect that this document, in combination with the companion article that addresses the implementation of these guidelines, will assist all medical professionals with the care of patients who have had or at risk of sudden cardiac death.

Background Catheter ablation is a curative treatment with excellent success and minimal complication rates for patients with supraventricular or ventricular arrhythmias. Methods The acute outcomes and complications of all catheter ablation procedures for supraventricular and ventricular arrhythmias performed at the Quebec Heart Institute (Sainte-Foy, Quebec) during a 14-year period from January 1, 1993, to December 31, 2006, were prospectively assessed. The ablation procedures were classified according to the arrhythmias induced using standard electrophysiological techniques and definitions. Immediate success and complication rates were prospectively included in the database. Results A total of 5330 patients had catheter ablation performed at the Institute during the period assessed. The mean (± SD) age of patients was 50±18 years (range four to 97 years), and 2340 patients (44%) were men. Most of the patients were younger than 75 years (group 1), and 487 (9%) were 75 years of age and older (group 2). Indications for ablations were as follows: atrioventricular nodal reentry tachycardia (AVNRT) in 2263 patients, accessory pathways in 1147 patients, atrioventricular node ablation in 803 patients, typical atrial flutter in 377 patients and atrial tachycardia in 160 patients; 580 patients had other ablation procedures. The overall success rates were 81% for atrial tachycardia, 92% for accessory pathways or flutter, and 99% for AVNRT or atrioventricular node ablation. There was no difference in the success rates of the younger (group 1) and older (group 2) patients. Seventy-seven patients (1.4%) had complications, including 11 major events (myocardial infarction in one patient, pulmonary embolism in three patients and permanent pacemaker in seven patients). In patients undergoing AVNRT ablation, two had a permanent pacemaker implanted immediately after the procedure and three had a permanent pacemaker implanted at follow-up. Conclusions The results confirm that radiofrequency ablation is safe and effective, supporting ablation therapy as a first-line therapy for the majority of patients with cardiac arrhythmias.

Extra-anatomic Course of a Right Ventricular Pacing Lead: Clinical Implications Pierre-Louis Nadeau, MD, Jean Champagne, MD, Franck Molin, MD, Jean-Francois Sarrazin, MD, Gilles O’Hara, MD, Isabelle Nault, MD, Louis Blier, MD, Eric Charbonneau, MD, Fr ed eric Jacques, MD, and Francois Philippon, MD Electrophysiology Division, Institut universitaire de cardiologie et de pneumologie de Qu ebec, Laval University, Qu ebec City, Qu ebec, Canada Cardiac Surgery Division, Institut universitaire de cardiologie et de pneumologie de Qu ebec, Laval University, Qu ebec City, Qu ebec, Canada

days, during the index surgical admission, or during readmission to hospital within 30 days of discharge. Electronic health records of those with AF/AFL were reviewed and departmental data were obtained from the TOH surgical database. RESULTS: During the study period, 859 non-cardiothoracic surgeries were performed and POAF was documented in 42 patients (4.9%). POAF patients were predominantly male of mean age 74 years, with mean CHADS2 and CHA2DS2VASc scores of 2.24 and 4.14, respectively [Table 1]. POAF prolonged median length of stay from 1.6 days (IQR 0.5-2.1) to 8.5 d (IQR 4.25-19.5), and approximately 1 in 4 POAF patients experienced a major adverse event [Table 1]. POAF was associated with in-hospital mortality of 16.7% and 26% of survivors were discharged to a facility with increased level of care compared to baseline [Fig. 1]. The vast majority (93%) of POAF patients had CHADS2 1; 72% of patients with known AF were taking oral anticoagulants (OAC) prior to admission and 63% were discharged on OAC. Thirty-three percent of patients with newly diagnosed AF were discharged home on OAC [Table 1]. CONCLUSION: POAF complicates approximately 5% of surgical admissions in our sample, potentially translating to 527 cases per year at OCH alone and > 2500 cases per year in a medium sized city such as Ottawa. The POAF population is relatively young and sick; suffering prolonged hospitalizations and adverse outcomes. There appear to be multiple opportunities to improve outcomes following POAF in our population. Further research is required to confirm these data in a larger population and to test the hypothesis that aggressive intervention in POAF improves patient outcomes and/or reduces hospital costs. 451 COMPARISON OF PULMONARY VEIN ISOLATION USING CRYOBALLOON ARTIC FRONT ADVANCE VERSUS CONTACT FORCE-GUIDED RADIOFREQUENCY FOR PAROXYSMAL ATRIAL FIBRILLATION