Gilles O’Hara

Mechanisms, prevention, and treatment of atrial fibrillation after cardiac surgery.

Post-operative atrial fibrillation (POAF) is a frequent complication occurring in 30% to 50% of patients after cardiac surgery. It is associated with an increased risk of mortality and morbidity, predisposes patients to a higher risk of stroke, requires additional treatment, and increases the costs of the post-operative care. The aim of this review is to present the current state of knowledge about the risk factors, mechanisms, prevention, and treatment of this complication. In addition to the well known risk factors for the development of POAF such as age, left atrial enlargement, and valvular surgery, new metabolic risk factors related to visceral obesity have been identified. With regard to the prevention of POAF, beta-blocker drugs are effective and safe and can be used in most patients, whereas amiodarone can be added in high-risk patients. Biatrial pacing was shown to be effective; however, its complexity might limit its application. Although there are only few data regarding the usefulness of magnesium, statins, N-3 polyunsaturated fatty acids, and corticosteroids, their addition to beta-blocker drugs might be of benefit for further reducing POAF. Treatment includes the use of an AV nodal blocking agent to achieve the rate control. If AF does not spontaneously convert to sinus rhythm within 24 h, anticoagulation should be initiated and a rhythm control strategy should be attempted. More investigations are warranted to explore mechanisms by which POAF occurs. This new knowledge would undoubtedly translate into a more efficient prevention and treatment of this common post-operative complication that is associated with a major health and economic burden.

Sildenafil (Viagra) Prolongs Cardiac Repolarization by Blocking the Rapid Component of the Delayed Rectifier Potassium Current

BACKGROUND-Several cases of unexpected death have been reported with sildenafil in patients predisposed to ischemic cardiac events. Although acute episodes of ischemia could account for some of these deaths, we hypothesized that sildenafil may have unsuspected electrophysiological effects predisposing some patients to proarrhythmia. METHODS AND RESULTS-Studies were undertaken in 10 isolated guinea pig hearts that demonstrated prolongation of cardiac repolarization in a reverse use-dependent manner by sildenafil 30 mcmol/L. Action potential duration increased 15% from baseline 117+/-3 to 134+/-2 ms with sildenafil during pacing at 250 ms cycle length, whereas a 6% increase from 99+/-2 to 105+/-2 ms was seen with pacing at 150 ms cycle length. Experiments in human ether-a-go-go-related gene (HERG)-transfected HEK293 cells (n=30) demonstrated concentration-dependent block of the rapid component (I(Kr)) of the delayed rectifier potassium current: activating current was 50% decreased at 100 mcmol/L. This effect was confirmed using HERG-transfected Chinese hamster ovary (CHO) cells, which exhibit no endogenous I(K)-like current. CONCLUSIONS-Sildenafil possesses direct cardiac electrophysiological effects similar to class III antiarrhythmic drugs. These effects are observed at concentrations that may be found in conditions of impaired drug elimination such as renal or hepatic insufficiency, during coadministration of another CYP3A substrate/inhibitor, or after drug overdose and offer a new potential explanation for sudden death during sildenafil treatment.

Catheter ablation for cardiac arrhythmias: A 14-year experience with 5330 consecutive patients at the Quebec Heart Institute, Laval Hospital

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 re-entry 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.

Randomized trial of a noninvasive strategy to reduce hospital stay for patients with low-risk myocardial infarction

OBJECTIVES This study evaluated the feasibility, pertinence and psychosocial repercussions of a noninvasive reduced hospital stay strategy (three days) for low-risk patients with acute myocardial infarction using simple clinical criteria and predischarge 24-h ambulatory ST-segment ischemic monitoring. BACKGROUND Previous studies evaluating shorter stays for uncomplicated myocardial infarction have been limited by retrospective or nonrandomized design and overdependence on invasive cardiac procedures. METHODS One-hundred twenty consecutive patients admitted with an acute myocardial infarction fulfilling low-risk criteria were randomized 2:1 to a short hospital stay (80 patients) or standard stay (40 patients). Short-stay patients with no ischemia on ST-segment monitoring were discharged on day 3, returning for exercise testing a week later. All analyses were on an intention-to-treat basis. RESULTS Forty-one percent of all screened patients with acute myocardial infarction would have been medically eligible for the short-stay strategy. Seventeen patients (21%) were not discharged early because of ischemia on ST-monitoring or angina. Median initial hospital stay was halved from 6.9 days in the standard stay to 3.5 days in the short-stay group. At six months, median total days hospitalized were 7.5 in the standard stay and 3.6 in the short-stay group (p < 0.0001). Adverse events and readmissions were low and not significantly different, and there were 25% fewer invasive cardiac procedures in the short-stay group. Psychosocial outcomes, risk factor changes and exercise test results were similar in the two groups. CONCLUSIONS This reduced hospital stay strategy for low-risk patients with acute myocardial infarction is feasible and worthwhile, resulting in a substantial and sustained reduction in days hospitalized. It is without unfavorable psychosocial consequences, appears safe and does not increase the number of invasive cardiac procedures.

Contractile reserve assessed using dobutamine echocardiography predicts left ventricular reverse remodeling after cardiac resynchronization therapy: prospective validation in patients with left ventricular dyssynchrony.

Background: The presence of viable myocardium may predict response to cardiac resynchronization therapy (CRT). The aim of this study is to evaluate in patients with left ventricular (LV) dyssynchrony whether response to CRT is related to myocardial viability in the region of the pacing lead. Methods: Forty‐nine consecutive patients with advanced heart failure, LV ejection fraction < 35%, QRS duration > 120 ms and intraventricular asynchronism ≥ 50 ms were included. Dobutamine stress echocardiography was performed within the week before CRT implantation. Resting echocardiography was performed 6 months after CRT implantation. Viability in the region of LV pacing lead was defined as the presence of viability in two contiguous segments. Response to CRT was defined by evidence of reverse LV remodeling (≥15% reduction in LV end‐systolic volume). Results: Thirty‐one patients (63%) were identified as responders at follow‐up. The average of viable segments was 5.9 ± 2 in responders and 3.2 ± 3 in nonresponders (P = 0.0003). Viability in the region of the pacing lead had a sensitivity of 94%, a specificity of 67%, a positive predictive value of 83%, and a negative predictive value of 86% for the prediction of response to CRT. Conclusions: In patients with LV dyssynchrony, reverse remodeling after CRT requires viability in the region of the pacing lead. This simple method using echocardiography dobutamine for the evaluation of local viability (i.e., viability in two contiguous segments) may be useful to the clinician in choosing the best LV lead positioning. (Echocardiography 2010;27:668‐676)

The Brugada syndrome in Canada: A unique French-Canadian experience

UNLABELLED The Brugada syndrome (BS) is a clinical entity involving cardiac sodium channelopathy, typical electrocardiogram (ECG) changes and predisposition to ventricular arrhythmia. This syndrome is mainly recognized by specialized cardiologists and electrophysiologists. Data regarding BS largely come from multicentre registries or Asian countries. The present report describes the Quebec Heart Institute experience, including the clinical characteristics and prognosis of native French-Canadian subjects with the Brugada-type ECG pattern. METHODS AND RESULTS BS has been diagnosed in 35 patients (mean age 51 +/- 12 years) at the Quebec Heart Institute since 2001. Patients were referred from primary care physicians for ECG abnormalities, syncope or ventricular arrhythmia, or were diagnosed incidentally on an ECG obtained for other purposes. The abnormal ECG was recognized after a syncopal spell in four patients and during family screening in four patients. All of the others were incidental findings following a routine ECG. No patient had a family history of sudden cardiac death at younger than 45 years of age. In this population, right bundle branch block pattern with more than 2 mm ST segment elevation in leads V1 to V3 was recorded spontaneously in 25 patients and was induced by sodium blockers in 10 patients. The sodium channel blocker test was performed in 21 patients and was positive in 18 patients (86%). An electrophysiological study was performed in 20 of 35 patients, during which ventricular fibrillation was induced in five patients; three of the five patients were previously asymptomatic. An implantable cardioverter-defibrillator was implanted in six of 35 patients (17%), including three of four patients with a history of syncope. A loop recorder was implanted in three patients. After a mean follow-up of 36 +/- 18 months, one patient died from a noncardiac cause and one patient (with a history of syncope) received an appropriate shock from his implantable cardioverter-defibrillator. No event occurred in the asymptomatic population. CONCLUSIONS BS is present in the French-Canadian population and is probably under-recognized. Long-term prognosis of individuals with BS, especially in sporadic, asymptomatic cases, needs to be clarified.

Contact-Force Catheters: Efficacy Versus Safety? Case Report of 2 Atrioesophageal Fistulae.

Contact‐force (CF) catheters appear to be more effective compared to standard ablation catheters for complex radiofrequency ablation including atrial fibrillation (AF) ablation when optimal CF >10 g is achieved. Some have suggested that this technology could also improve procedural safety. We report 2 cases of atrioesophageal fistulae (AEF), a rare but catastrophic complication of AF ablation. These are to our knowledge the first cases of AEF described after using CF catheters.

Cardiac Implantable Electronic Device Infection: Detailed Analysis of Cost Implications

BACKGROUND Infections of cardiac implantable electronic devices (CIED) are associated with significant morbidity and mortality. Despite many preventive measures, this condition is associated with significant costs for the health care system. METHODS We retrospectively analyzed all infection cases referred for lead extraction at a single university hospital over 1 year (2015-2016). We then calculated all costs related to the infection episode per patient using hospital databases and charts review. RESULTS Thirty-eight patients with CIED infections (29% women-mean age 71 ± 14 years) were referred for lead extraction (27 pocket infections, 11 endocarditis). Devices were mainly pacemakers (60%). When the pathogen was identified, Staphylococcus aureus methicillin sensitive was the main cause. Extraction was performed in all but 3 cases (92%). One death occurred in the nonextracted group. Respective durations of hospitalization and intravenous and antibiotic administration for patients undergoing extraction were 21 and 36 days. The calculated mean total cost for CIED infection management was CAD

Wolff-Parkinson-White as a bystander in a patient with aborted sudden cardiac death

29,907 (median: 26,879; range: CAD

Extra-anatomic Course of a Right Ventricular Pacing Lead: Clinical Implications

4,827-