Santabhanu Chakrabarti

Outcome of Apparently Unexplained Cardiac Arrest: Results From Investigation and Follow-Up of the Prospective Cardiac Arrest Survivors With Preserved Ejection Fraction Registry

Background—The Cardiac Arrest Survivors with Preserved Ejection Fraction Registry (CASPER) enrolls patients with apparently unexplained cardiac arrest and no evident cardiac disease to identify the pathogenesis of cardiac arrest through systematic clinical testing. Exercise testing, drug provocation, advanced cardiac imaging, and genetic testing may be useful when a cause is not apparent. Methods and Results—The first 200 survivors of unexplained cardiac arrest from 14 centers across Canada were evaluated to determine the results of investigation and follow-up (age, 48.6±14.7 years, 41% female). Patients were free of evidence of coronary artery disease, left ventricular dysfunction, or evident repolarization syndromes. Advanced testing determined a diagnosis in 34% of patients at baseline, with a diagnosis emerging during follow-up in 7% of patients. Of those who were diagnosed, 28 (35%) had an underlying structural condition and 53 (65%) had a primary electric disease. During a mean follow-up of 3.15±2.34 years, 23% of patients had either a shock or an appropriate antitachycardia pacing from their implantable cardioverter defibrillator, or both. The implantable cardioverter defibrillator appropriate intervention rate was 8.4% at 1 year and 18.1% at 3 years, with no clear difference between diagnosed and undiagnosed subjects, or between those diagnosed with a primary electric versus structural pathogenesis. Conclusions—Obtaining a diagnosis in previously unexplained cardiac arrest patients requires systematic clinical testing and regular follow-up to unmask the cause. Nearly half of apparently unexplained cardiac arrest patients ultimately received a diagnosis, allowing for improved treatment and family screening. A substantial proportion of patients received appropriate implantable cardioverter defibrillator therapy during medium-term follow-up. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT00292032.

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.

Procainamide infusion in the evaluation of unexplained cardiac arrest: From the Cardiac Arrest Survivors with Preserved Ejection Fraction Registry (CASPER)

BACKGROUND Provocative testing with sodium channel blockers is advocated for the evaluation of unexplained cardiac arrest (UCA) with the primary purpose of unmasking the typical ECG features of Brugada syndrome. The Cardiac Arrest Survivors with Preserved Ejection Fraction Registry (CASPER) systematically assesses subjects with UCA or a family history of sudden death (FHSD). OBJECTIVE The purpose of this study was to determine the clinical yield of procainamide infusion in a national registry of subjects with either UCA or a FHSD. METHODS Subjects with either UCA or a FHSD without evidence of a Brugada pattern at baseline underwent procainamide testing (15 mg/kg to a maximum of 1 g at 50 mg/min). A test was considered positive for Brugada pattern if there was an increase in ST elevation >1 mm or if there was >1 mm of new ST elevation in leads V1 and/or V2. Genetic testing was performed on the basis of phenotype detection. RESULTS Procainamide testing was performed in 174 subjects (age 46.8 ± 15.4 years, 47% female). Testing provoked a Brugada pattern in 12 subjects (6.9%), 5 of whom had no ST abnormalities at baseline. No subjects with a negative procainamide challenge were subsequently diagnosed with Brugada syndrome. Genetic testing was conducted in 10 of the 12 subjects with a provoked Brugada pattern and was positive for a mutation in the SCN5A gene in 1. CONCLUSION Irrespective of the baseline ECG, procainamide testing provoked a Brugada pattern in a significant proportion of subjects with UCA or a FHSD, thereby facilitating a diagnosis of Brugada syndrome, and is recommended in the workup of UCA.

Evolution of clinical diagnosis in patients presenting with unexplained cardiac arrest or syncope due to polymorphic ventricular tachycardia.

BACKGROUND A systematic evaluation of patients with unexplained cardiac arrest (UCA) yields a diagnosis in 50% of the cases. However, evolution of clinical phenotype, identification of new disease-causing mutations, and description of new syndromes may revise the diagnosis. OBJECTIVE To assess the evolution in diagnosis among patients with initially UCA. METHODS Diagnoses were reviewed for all patients with UCA recruited from the Cardiac Arrest Survivors with Preserved Ejection Fraction Registry with at least 1 year of follow-up. RESULTS After comprehensive investigation of 68 patients (age 45.2 ± 14.9 years; 63% men), the initial diagnosis was as follows: idiopathic ventricular fibrillation (n = 34 [50%]), a primary arrhythmic disorder (n = 21 [31%]), and an occult structural cause (n = 13 [19%]). Patients were followed for 30 ± 17 months, during which time the diagnosis changed in 12 (18%) patients. A specific diagnosis emerged for 7 patients (21%) with an initial diagnosis of idiopathic ventricular fibrillation. A structural cardiomyopathy evolved in 2 patients with an initial diagnosis of primary electrical disorder, while the specific structural cardiomyopathy was revised for 1 patient. Two patients with an initial diagnosis of a primary arrhythmic disorder were subsequently considered to have a different primary arrhythmic disorder. A follow-up resting electrocardiogram was the test that most frequently changed the diagnosis (67% of the cases), followed by genetic testing (17%). CONCLUSIONS The reevaluation of patients presenting with UCA may lead to a change in diagnosis in up to 20%. This emphasizes the need to actively monitor the phenotype and also has implications for the treatment of these patients and the screening of their relatives.

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.

Using Left-Ventricular–Only Pacing to Eliminate T-Wave Oversensing in a Biventricular Implantable Cardiac Defibrillator

A man aged 75 years and with nonischemic cardiomyopathy had implantation of a biventricular implantable cardiac defibrillator (ICD). Consistent biventricular pacing was limited by intermittent T-wave oversensing (TWOS). A strategy of left-ventricular-only pacing was used to eliminate TWOS. This strategy obviates the need to reduce ventricular sensitivity and thus may be an effective alternative to biventricular pacing complicated by TWOS.

Recognizing Life-Threatening Causes of Syncope

While the overall prognosis of syncope is favorable, the identification of individuals with a potentially life-threatening cause is of paramount importance. Cardiac syncope is associated with an elevated risk of mortality, and includes both primary arrhythmic and obstructive etiologies. Identification of these individuals is contingent on careful clinical assessment and judicious use of diagnostic investigations. This article focuses on life-threatening causes of syncope and a diagnostic approach to facilitate their identification.

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.

Nothing inside the heart – Combining epicardial pacing with the S-ICD

Introduction The implantation of implantable cardioverter-defibrillator (ICD) systems in patients with no or limited venous access is technically challenging. After disappointing experiences with epicardial ICD patches, surgical techniques focused on the implantation of subcutaneous high-voltage array electrodes or intrapericardial placement of standard transvenous ICD leads. The Boston Scientific subcutaneous ICD (Boston Scientific, Marlborough, MA) is the first completely subcutaneous ICD (S-ICD), initially approved in Europe in 2009 and market released in the United States in 2012. The S-ICD is an effective and attractive alternative to transvenous ICD systems in patients without need for antitachycardia or antibradycardia pacing. Previous trials excluded patients with existing epicardial defibrillation patches or coils, presence of epicardial pacing leads, unipolar pacemaker systems, or documented monomorphic ventricular tachycardia likely to be terminated by antitachycardia pacing. Therefore the safety and feasibility of S-ICD systems in patients with a concomitant epicardial pacing system and a class I indication for antibradycardia pacing is unknown. We report a case of a patient with an indication for both a secondary prevention ICD and permanent pacing who was high risk for recurrent bacterial seeding of a transvenous device and who underwent successful implantation of an epicardial pacemaker and a Boston Scientific S-ICD system.

Lead Integrity Alert Is Useful for Assessment of Performance of Biotronik Linox Leads

Medtronics Lead Integrity Alert (LIA) software algorithm is useful for detecting abnormal parameters across various ICD‐lead families. However, its utility in the assessment of the Biotronik Linox™ family of high‐voltage (HV) leads is unknown.