Marc W. Deyell

Pulmonary vein isolation using “contact force” ablation: The effect on dormant conduction and long-term freedom from recurrent atrial fibrillation—A prospective study

BACKGROUND Atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI) is associated with PV to left atrium reconduction. Effective lesion creation necessitates adequate contact force between the ablation catheter and myocardium. OBJECTIVE The purpose of this study was to study the utility of contact force-guided ablation on immediate and long-term outcomes. METHODS Seventy-five patients with highly symptomatic paroxysmal AF underwent wide circumferential PVI using an irrigated-tip radiofrequency catheter. In 25 patients, ablation was guided by real-time contact force measurements (CF group; SmartTouch, Biosense Webster). A control group of 50 patients underwent PVI using a standard nonforce sensing catheter (standard group; ThermoCool, Biosense Webster). After PVI, all patients underwent adenosine testing to unmask dormant conduction. Patients were followed up at 3, 6, and 12 months and by transtelephonic monitoring as well. RESULTS Dormant conduction was unmasked and subsequently eliminated in 4 PV pairs (8%; 16% of patients) in the CF group and 35 PV pairs (35%; 52% of patients) in the standard group (P = .0004 per PV pair; P = .0029 per patient). The single-procedure, off-antiarrhythmic drug freedom from recurrent atrial arrhythmias at 1 year was 88% in the CF group vs 66% in the standard group (P = .047). Procedure duration and fluoroscopy time were significantly longer in the CF group (P = .0038 and P = .0001, respectively). CONCLUSION The use of real-time contact force guidance results in a significant reduction in the prevalence of dormant conduction with improved long-term freedom from recurrent arrhythmias. The utility of a contact force-guided approach requires evaluation in a long-term prospective randomized study.

Risk of Bleeding on Triple Antithrombotic Therapy After Percutaneous Coronary Intervention/Stenting: A Systematic Review and Meta-analysis

BACKGROUND There are no reported randomized controlled trials of triple antithrombotic therapy (TT; aspirin plus a thienopyridine plus vitamin K antagonist) vs dual antiplatelet therapy (DAPT; aspirin plus a thienopyridine) among patients undergoing percutaneous coronary intervention with stenting (PCI-S). A systematic review and meta-analysis was undertaken to assess the risk of bleeding among patients receiving TT after PCI-S. METHODS Electronic databases were searched for studies reporting bleeding among patients receiving TT after PCI-S. Of the 4108 articles screened, 18 met study inclusion criteria and underwent detailed data extraction: of these, 6 reported in-hospital outcomes, 14 reported 30-day outcomes, and 9 reported 6-month outcomes. At each time point, pooled estimates of bleeding with TT were ascertained and where possible summary odds ratios (ORs) for comparative risks vs DAPT were calculated. RESULTS The pooled estimate of major bleeding rate with TT post PCI-S was 2.38% by 30 days postprocedure (95% confidence interval [CI], 0.98-3.77%) and 4.55% by 6 months postdischarge (95% CI, 0.56-8.53%). At 30 days and 6 months the rates of major bleeding with TT were significantly higher than those observed with DAPT: OR, 2.38 at 30 days (95% CI, 1.05-5.38) and OR, 2.87 at 6 months (95% CI, 1.47-5.62). CONCLUSIONS This systematic review and meta-analysis of reports of triple therapy with a vitamin K antagonist, aspirin, and clopidogrel after PCI-S provides precise and valid bleeding risk data. Based on existing observational studies the rates of major and any bleeding associated with TT are clinically important and significantly greater than those reported with DAPT.

Sudden Cardiac Death Risk Stratification

Arrhythmic sudden cardiac death (SCD) may be caused by ventricular tachycardia/fibrillation or pulseless electric activity/asystole. Effective risk stratification to identify patients at risk of arrhythmic SCD is essential for targeting our healthcare and research resources to tackle this important public health issue. Although our understanding of SCD because of pulseless electric activity/asystole is growing, the overwhelming majority of research in risk stratification has focused on SCD-ventricular tachycardia/ventricular fibrillation. This review focuses on existing and novel risk stratification tools for SCD-ventricular tachycardia/ventricular fibrillation. For patients with left ventricular dysfunction or myocardial infarction, advances in imaging, measures of cardiac autonomic function, and measures of repolarization have shown considerable promise in refining risk. Yet the majority of SCD-ventricular tachycardia/ventricular fibrillation occurs in patients without known cardiac disease. Biomarkers and novel imaging techniques may provide further risk stratification in the general population beyond traditional risk stratification for coronary artery disease alone. Despite these advances, significant challenges in risk stratification remain that must be overcome before a meaningful impact on SCD can be realized.

Pulmonary vein isolation using a pace-capture-guided versus an adenosine-guided approach: effect on dormant conduction and long-term freedom from recurrent atrial fibrillation--a prospective study.

Background— Atrial fibrillation recurrence after pulmonary vein (PV) isolation is associated with PV to left atrium reconduction. We prospectively studied the use of 2 procedural techniques designed to facilitate identification of residual gaps within the index ablation line. Methods and Results— After wide circumferential PV isolation, 40 patients received additional ablation targeted at locations of left atrial capture during high-output pacing (pace-capture group), while 40 patients underwent adenosine testing with targeted ablation at sites of dormant conduction (adenosine group). Patients were followed up at 3, 6, and 12 months. After PV isolation, high-output pace-capture was documented in 39 PVs (25%; 50% of patients) in the pace-capture group. Dormant conduction was unmasked in 34 PVs (22%; 53% of patients) in the adenosine group. A subset of 25 patients in the pace-capture group underwent adenosine testing without targeted ablation of dormant conduction. In these patients, only 10 out of 86 PVs (11.6%; 24% of patients) demonstrated dormant conduction after the elimination of local pace-capture. At a follow-up of 329±124 days, the single procedure off antiarrhythmic drug freedom from recurrent atrial fibrillation was 67.5% in the adenosine group and 65.0% in the pace-capture group ( P =0.814). Procedure duration and fluoroscopy time were significantly longer in the pace-capture group ( P =0.002 and P <0.001), whereas radiofrequency ablation time was comparable ( P =0.192). Conclusions— The use of high-output pacing post-PV isolation results in a significant reduction in the incidence of dormant conduction with a comparable long-term freedom from recurrent atrial fibrillation (versus adenosine-guided ablation). The use of these approaches requires evaluation in a long-term prospective randomized study.Background—Atrial fibrillation recurrence after pulmonary vein (PV) isolation is associated with PV to left atrium reconduction. We prospectively studied the use of 2 procedural techniques designed to facilitate identification of residual gaps within the index ablation line. Methods and Results—After wide circumferential PV isolation, 40 patients received additional ablation targeted at locations of left atrial capture during high-output pacing (pace-capture group), while 40 patients underwent adenosine testing with targeted ablation at sites of dormant conduction (adenosine group). Patients were followed up at 3, 6, and 12 months. After PV isolation, high-output pace-capture was documented in 39 PVs (25%; 50% of patients) in the pace-capture group. Dormant conduction was unmasked in 34 PVs (22%; 53% of patients) in the adenosine group. A subset of 25 patients in the pace-capture group underwent adenosine testing without targeted ablation of dormant conduction. In these patients, only 10 out of 86 PVs (11.6%; 24% of patients) demonstrated dormant conduction after the elimination of local pace-capture. At a follow-up of 329±124 days, the single procedure off antiarrhythmic drug freedom from recurrent atrial fibrillation was 67.5% in the adenosine group and 65.0% in the pace-capture group (P=0.814). Procedure duration and fluoroscopy time were significantly longer in the pace-capture group (P=0.002 and P<0.001), whereas radiofrequency ablation time was comparable (P=0.192). Conclusions—The use of high-output pacing post-PV isolation results in a significant reduction in the incidence of dormant conduction with a comparable long-term freedom from recurrent atrial fibrillation (versus adenosine-guided ablation). The use of these approaches requires evaluation in a long-term prospective randomized study.

Prognostic impact of inappropriate defibrillator shocks in a population cohort

Background There is a relative paucity of data linking inappropriate implantable cardioverter-defibrillator (ICD) shocks to adverse clinical outcomes. Objective To examine the association between inappropriate ICD shocks and mortality or heart transplantation in a large population cohort. Design, setting, patients A cohort study which included all subjects who underwent ICD implantation between 1998 and 2008 and were followed up at our institution. Main outcome measures Multivariable Cox regression analyses were conducted to investigate the effect of inappropriate shocks on the risk of death and heart transplantation. Appropriate and inappropriate ICD therapies were modelled as time-dependent covariates. Results A total of 1698 patients were included. During a median follow-up of 30 months, there were 246 (14.5%) deaths and 42 (2.5%) heart transplants. The incidence of inappropriate shocks was 10% at 1 year and 14% at 2 years. In the adjusted model, inappropriate shocks were not associated with death or transplantation (HR=0.97, 95% CI 0.70 to 1.36, p value=0.873). In contrast, appropriate shocks were associated with adverse outcomes (HR=3.11, 95% CI 2.41 to 4.02, p value<0.001). The lack of association between inappropriate shocks and outcomes persisted for those with severely impaired left ventricular function (ejection fraction <30%) and for those receiving multiple inappropriate treatments. Conclusions In this study, we observed no association between inappropriate ICD shocks and increased mortality or heart transplantation, even among those with severely impaired cardiac function. These findings question whether inappropriate ICD shocks lead to adverse outcomes.

Timing of nonemergent coronary artery bypass grafting and mortality after non-ST elevation acute coronary syndrome

BACKGROUND The purpose of this study was to determine the association between time to coronary artery bypass grafting (CABG) and mortality among patients admitted with non-ST elevation acute coronary syndrome (NSTEACS). Patients are increasingly being referred for CABG soon after NSTEACS, although few data exist to guide the optimal timing of bypass surgery. METHODS We identified a cohort of all patients who underwent nonemergent CABG within 60 days of hospitalization for NSTEACS in the province of Alberta, Canada, from 2000 to 2004. Time from admission to CABG was categorized as early (2-7 days), intermediate (8-14 days), or late (15-60 days-reference group). The primary outcome was mortality occurring within 30 days of surgery. RESULTS Of the total cohort of 1,454 patients, 213 (14.6%) underwent early, 637 (43.8%) underwent intermediate, and 707 (48.6%) underwent late CABG surgery. In the final adjusted model time to CABG was not statistically significant as an independent predictor of short-term mortality. Compared to late CABG, there was a nonsignificant increased risk of mortality for those undergoing early (hazard ratio 2.36, 95% CI 0.72-7.76) and intermediate (hazard ratio 1.68, 95% CI 0.76-3.72) CABG surgery. CONCLUSIONS Time from admission to CABG was not associated with an increased risk of short-term mortality. However, there was a trend toward increased mortality with early CABG, and this study does not exclude the presence of a modest risk association between timing of CABG and short-term mortality.

Preventing cardiac implantable electronic device infections

Cardiac implantable electronic devices (CIEDs) have dramatically improved clinical outcomes in patients with heart disease, and the number of CIED-related procedures being performed continues to grow. Unfortunately, the rate of device-related infection (DRI) is increasing disproportionately to the rate of implantation, with DRI rates of >2% in many series. This increase in DRI is a consequence of the increased number of patients with a higher burden of comorbidities, who are more susceptible to infection and are undergoing more complex device procedures. Identification of high-risk patients is an important component of procedural planning, and targeted therapy and surveillance may be beneficial in certain groups. An understanding of the pathophysiology of DRI has facilitated more effective and widespread use of prophylactic antibiotics; however, current guidelines for antibiotic prophylaxis are based on a relatively small evidence base. Clinical equipoise remains regarding the optimal prophylactic regimen, and we are continuing to learn how best to manage these patients. In this review, we discuss the epidemiology and pathophysiology of DRI and its clinical presentation, the risk factors for DRI, and the existing and emerging evidence supporting strategies to prevent DRI.

Selecting Appropriate Diagnostic Tools for Evaluating the Patient With Syncope/Collapse

The investigation of syncope is challenging and physicians have an ever-increasing array of diagnostic tools at their disposal. There are two essential goals that drive investigation: risk stratification and identification of etiology. In this review, we outline our approach while providing a synopsis of the available supportive evidence. The key to syncope is in the story as told by the patient and a bystander, since this drives both risk assessment and diagnostic testing. All patients should initially be evaluated with a systematic history and physical examination as well as an ECG. The initial evaluation provides an estimation of risk and directs whether inpatient or outpatient evaluation is appropriate. In a substantial proportion of patients, the etiology will be evident after initial evaluation and no further investigation is required. In the remaining, targeted use of additional investigations in the form of cardiac imaging, provocative testing and/or ambulatory ECG monitoring should be performed. A thoughtful and systematic approach to the investigation of syncope optimizes the diagnostic yield but also ensures efficient usage of limited health care resources.

The time course of exit and entrance block during cryoballoon pulmonary vein isolation.

AIMS The dynamic time course of entrance and exit block during pulmonary vein isolation (PVI) is unknown. The purpose of this series was to dynamically evaluate the manifestation of entrance and exit conduction block during simultaneous circumferential PVI. METHODS AND RESULTS Pacing manoeuvres were performed during cryoballoon ablation of left-sided pulmonary veins (PVs) in 30 consecutive patients with a history of drug-refractory paroxysmal atrial fibrillation. At the onset of ablation continuous pacing was performed from the PV at a cycle length of 600 ms until the appearance of exit block. Once exit block was demonstrated, uninterrupted pacing was immediately transitioned to the distal coronary sinus (CS) catheter and continued at 600 ms throughout the rest of the cryoapplication. The timing of exit block, entrance block, and corresponding cryoballoon temperature were noted for all patients. In the 45 PVs when real-time PV recordings were available during cryothermal ablation, the presence of exit block was reliably demonstrated to precede entrance block (P < 0.0001) by a median of 5 s [interquartile range (IQR) 3, 12; median temperature at isolation -39°C (IQR -30, -45); nadir ablation temperature -53°C (IQR -48, -59)]. In all cases, when uninterrupted pacing was transitioned from the PV to the distal CS, entrance conduction from the left atrium to PV remained intact. CONCLUSION Circumferential PV ablation results in progressive PVI, beginning with unidirectional exit block, and followed by entrance block. As exit block reliably precedes entrance block, we are able to provide justification for the exclusive use of entrance conduction block as the endpoint of cryoballoon-based PVI.

Assessment of Genetic Causes of Cardiac Arrest

Unexplained cardiac arrest is defined as a cardiac arrest in the absence of coronary artery disease and overt structural heart disease, present in 5%-10% of cardiac arrest survivors. A genetic contribution to cardiac arrest is more common in this population, most commonly attributed to an inherited ion channel abnormality leading to familial syncope and sudden death. The common causes are Long QT and Brugada syndrome, catecholaminergic ventricular tachycardia, idiopathic ventricular fibrillation, and early repolarization syndrome. Latent structural causes include inherited cardiomyopathy such as arrhythmogenic right ventricular cardiomyopathy. We review these causes in detail and a structured approach to the investigation of these patients, which provides a diagnosis in approximately half of these patients. This allows for the initiation of disease-specific treatments and enables family screening.