Arnon Adler

Derivation and validation of a simple exercise-based algorithm for prediction of genetic testing in relatives of LQTS probands

Background— Genetic testing can diagnose long-QT syndrome (LQTS) in asymptomatic relatives of patients with an identified mutation; however, it is costly and subject to availability. The accuracy of a simple algorithm that incorporates resting and exercise ECG parameters for screening LQTS in asymptomatic relatives was evaluated, with genetic testing as the gold standard. Methods and Results— Asymptomatic first-degree relatives of genetically characterized probands were recruited from 5 centers. QT intervals were measured at rest, during exercise, and during recovery. Receiver operating characteristics were used to establish optimal cutoffs. An algorithm for identifying LQTS carriers was developed in a derivation cohort and validated in an independent cohort. The derivation cohort consisted of 69 relatives (28 with LQT1, 20 with LQT2, and 21 noncarriers). Mean age was 35±18 years, and resting corrected QT interval (QTc) was 466±39 ms. Abnormal resting QTc (females ≥480 ms; males ≥470 ms) was 100% specific for gene carrier status, but was observed in only 48% of patients; however, mutations were observed in 68% and 42% of patients with a borderline or normal resting QTc, respectively. Among these patients, 4-minute recovery QTc ≥445 ms correctly restratified 22 of 25 patients as having LQTS and 19 of 21 patients as being noncarriers. The combination of resting and 4-minute recovery QTc in a screening algorithm yielded a sensitivity of 0.94 and specificity of 0.90 for detecting LQTS carriers. When applied to the validation cohort (n=152; 58 with LQT1, 61 with LQT2, and 33 noncarriers; QTc=443±47 ms), sensitivity was 0.92 and specificity was 0.82. Conclusions— A simple algorithm that incorporates resting and exercise-recovery QTc is useful in identifying LQTS in asymptomatic relatives.

Quinidine, A Life-Saving Medication for Brugada Syndrome, Is Inaccessible in Many Countries

OBJECTIVES The aim of this study was to determine the availability of quinidine throughout the world. BACKGROUND Quinidine is the only oral medication that is effective for preventing life-threatening ventricular arrhythmias due to Brugada syndrome and idiopathic ventricular fibrillation. However, because of its low price and restricted indication, this medication is not marketed in many countries. METHODS We conducted a survey of the availability of quinidine by contacting professional medical societies and arrhythmia specialists worldwide. Physicians were e-mailed questionnaires requesting information concerning the quinidine preparation available at their hospital. We also requested information concerning cases of adverse arrhythmic events resulting from unavailability of quinidine. RESULTS A total of 273 physicians from 131 countries provided information regarding the availability of quinidine. Quinidine was readily available in 19 countries (14%), not accessible in 99 countries (76%), and available only through specific regulatory processes that require 4 to 90 days for completion in 13 countries (10%). We were able to gather information concerning 22 patients who had serious arrhythmias probably related (10 cases) or possibility related (12 cases) to the absence of quinidine, including 2 fatalities possibly attributable to the unavailability of quinidine. CONCLUSIONS The lack of accessibility of quinidine is a serious medical hazard at the global level.

Viewpoint and CommentaryPreventing Sudden Death of Athletes With Electrocardiographic Screening: What Is the Absolute Benefit and How Much Will it Cost?

OBJECTIVES This study sought to estimate the costs of a national electrocardiographic (ECG) screening of athletes in the United States and the number of lives that would be saved by that program. BACKGROUND A single study from Italy suggests that mandatory ECG screening of athletes reduces their risk of sudden cardiac death. Based on that study, ECG screening of athletes is endorsed by the European Society of Cardiology, though not by the American Heart Association. The widespread application of ECG screening remains controversial because the absolute reduction of sudden cardiac death risk provided, and its economic ramifications, have not been studied in detail. METHODS A cost-projection model was based on the Italian study, replicating its data in terms of athlete characteristics and physician performance. The size of the screening-eligible population was estimated from data provided by the National Collegiate Athletic Association and the National Federation of State High School Associations. The costs of diagnostic tests were obtained from Medicare reimbursement rates. RESULTS A 20-year program of ECG screening of young competitive athletes in the United States would cost between

Effects of flecainide on exercise-induced ventricular arrhythmias and recurrences in genotype-negative patients with catecholaminergic polymorphic ventricular tachycardia

51 and

Risk stratification in Brugada syndrome: Clinical characteristics, electrocardiographic parameters, and auxiliary testing

69 billion and could be expected to save 4,813 lives. Accordingly, the cost per life saved is likely to range between

A mutation in the atrial-specific myosin light chain gene (MYL4) causes familial atrial fibrillation

10.6 and

Prognostic significance of fever-induced Brugada syndrome

14.4 million. CONCLUSIONS Our cost-projection model suggests that replicating the Italian strategy of ECG screening in the United States would result in enormous costs per life saved.

Drug-induced Brugada syndrome: Clinical characteristics and risk factors

BACKGROUND Conventional therapy with beta-blockers is incompletely effective in preventing arrhythmic events in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT). We have previously discovered that flecainide in addition to conventional drug therapy prevents ventricular arrhythmias in patients with genotype-positive CPVT. OBJECTIVE To study the efficacy of flecainide in patients with genotype-negative CPVT. METHODS We studied the efficacy of flecainide for reducing ventricular arrhythmias during exercise testing and preventing arrhythmia events during long-term follow-up. RESULTS Twelve patients with genotype-negative CPVT were treated with flecainide. Conventional therapy failed to control ventricular arrhythmias in all patients. Flecainide was initiated because of significant ventricular arrhythmias (n = 8), syncope (n = 3), or cardiac arrest (n = 1). At the baseline exercise test before flecainide, 6 patients had ventricular tachycardia and 5 patients had bigeminal or frequent ventricular premature beats. Flecainide reduced ventricular arrhythmias at the exercise test in 8 patients compared to conventional therapy, similar to that in patients with genotype-positive CPVT in our previous report. Notably, flecainide completely prevented ventricular arrhythmias in 7 patients. Flecainide was continued in all patients except for one who had ventricular tachycardia at the exercise test on flecainide. During a follow-up of 48±94 months, arrhythmia events (sudden cardiac death and aborted cardiac arrest) associated with noncompliance occurred in 2 patients. Flecainide was not discontinued owing to side effects in any of the patients. CONCLUSIONS Flecainide was effective in patients with genotype-negative CPVT, suggesting that spontaneous Ca(2+) release from ryanodine channels plays a role in arrhythmia susceptibility, similar to that in patients with genotype-positive CPVT.

Brugada syndrome: diagnosis, risk stratification, and management.

Risk stratification in Brugada syndrome remains a clinical challenge because the event rate is low but the presenting symptom is often cardiac arrest (CA). We review the data on risk stratification. A history of CA or malignant syncope is a strong predictor of spontaneous ventricular fibrillation (VF), whereas the prognostic value of a history of familial sudden death and the presence of a SCN5A mutation are less well defined. On the electrocardiogram, the presence of spontaneous type I electrocardiogram increases the risk for VF in all studies, whereas the presence of fragmented QRS complexes and early repolarization correlates with increased risk in several studies. Signal-averaged techniques using late potentials and microscopic T-wave alternans show some promising results in small studies that need to be confirmed. The value of electrophysiologic studies for predicting spontaneous VF remains controversial, and this includes programmed stimulation protocols that avoid a third extrastimuli or stimulation from the right ventricular outflow. Risk prediction is particularly challenging in children and women.

Brugada burden in Brugada syndrome: The way to go in risk stratification?

Atrial fibrillation (AF), the most common arrhythmia, is a growing epidemic with substantial morbidity and economic burden. Mechanisms underlying vulnerability to AF remain poorly understood, which contributes to the current lack of highly effective therapies. Recognizing mechanistic subtypes of AF may guide an individualized approach to patient management. Here, we describe a family with a previously unreported syndrome characterized by early-onset AF (age <35 years), conduction disease and signs of a primary atrial myopathy. Phenotypic penetrance was complete in all mutation carriers, although complete disease expressivity appears to be age-dependent. We show that this syndrome is caused by a novel, heterozygous p.Glu11Lys mutation in the atrial-specific myosin light chain gene MYL4. In zebrafish, mutant MYL4 leads to disruption of sarcomeric structure, atrial enlargement and electrical abnormalities associated with human AF. These findings describe the cause of a rare subtype of AF due to a primary, atrial-specific sarcomeric defect.