Changes in Follow-Up ECG and Signal-Averaged ECG in Patients with Arrhythmogenic Right Ventricular Cardiomyopathy

Natural Course of Electrocardiographic Features in Arrhythmogenic Right Ventricular Cardiomyopathy and Their Relation to Ventricular Arrhythmic Events

BACKGROUND

Electrocardiographic abnormalities are common in arrhythmogenic right ventricular cardiomyopathy and are included in the 2010 Task Force Criteria. Their time course, however, remains uncertain. In this retrospective observational study, we aimed to assess the long-term evolution of electrocardiographic characteristics and their relation to ventricular arrhythmias.

METHODS AND RESULTS

Three hundred fifty-three patients with arrhythmogenic right ventricular cardiomyopathy as per the 2010 Task Force Criteria with 6871 automatically processed 12-lead digital ECGs were included. The relationship between the electrocardiographic parameters and the risk of ventricular arrhythmias was assessed at 10 years from the first ECG. Electrocardiographic parameters were compared between the first contact ECG, the ECG at diagnosis, and the most recent ECG. Median time between the first and the latest ECG was 6 [interquartile range, 1-14] years. Reductions of QRS voltage, R- and T-wave amplitudes between the first, diagnostic, and the latest ECGs were observed across precordial and extremity leads. Mean QRS duration increased from 96 to 102 ms (P<0.001), terminal activation duration (V1) from 47 to 52 ms (P<0.001), and QTc from 419 to 432 ms (P<0.001). T-wave inversions in leads V3 to V6 and aVF at first ECG were associated with ventricular arrhythmias (adjusted hazard ratio [HRadj][V3], 2.03 [95% CI, 1.23-3.34] and HRadj[aVF], 1.87 [95% CI, 1.13-3.08]).

CONCLUSIONS

Depolarization and repolarization parameters evolved over time in patients with arrhythmogenic right ventricular cardiomyopathy, supporting the progressive nature of arrhythmogenic right ventricular cardiomyopathy. Electrocardiographic abnormalities may be detected before diagnosis and might, although not fulfilling the 2010 Task Force Criteria, be markers of early disease. T-wave inversion in leads V3 or aVF before diagnosis was associated with ventricular arrhythmias during follow-up.

Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) encompasses a group of conditions characterized by right ventricular fibrofatty infiltration, with a predominant arrhythmic presentation. First described in the late 1970s and early 1980s, it is now frequently recognized to have biventricular involvement. The prevalence is ∼1:2,000 to 1:5,000, depending on geographic location, and it has a slight male predominance. The diagnosis of ARVC is determined on the basis of fulfillment of task force criteria incorporating electrophysiological parameters, cardiac imaging findings, genetic factors, and histopathologic features. Risk stratification of patients with ARVC aims to identify those who are at increased risk of sudden cardiac death or sustained ventricular tachycardia. Factors including age, sex, electrophysiological features, and cardiac imaging investigations all contribute to risk stratification. The current management of ARVC includes exercise restriction, β-blocker therapy, consideration for implantable cardioverter-defibrillator insertion, and catheter ablation. This review summarizes our current understanding of ARVC and provides clinicians with a practical approach to diagnosis and management.

Late potentials and their correlation with ventricular structure in patients with ventricular arrhythmias

INTRODUCTION

The presence of late potentials (LP) may indicate a predisposition to ventricular arrhythmias and sudden cardiac death. We investigated the association between presence of LP and structural cardiac anomalies assessed by magnetic resonance (CMR) in patients presenting with ventricular arrhythmias.

METHODS

We included 42 patients admitted with ventricular tachycardia or fibrillation who had undergone both signal-averaged ECG recording and CMR imaging. Clinical data and CMR findings were compared in patients with and without LP.

RESULTS

The majority, 26 (62%) patients, were sudden cardiac death survivors and the remaining 16 (38%) were admitted with ventricular tachycardia. After full diagnostic work-up, the most common diagnoses in the cohort were idiopathic ventricular tachycardia/ventricular fibrillation (25 patients, 60%) or cardiomyopathies (11 patients, 26%). LPs were positive in 29 (69%) when using the revised Task Force criteria. When comparing patients with and without late potentials, there were no significant differences in right ventricular size relative to body surface area (102 mL/m² vs 92 mL/m² ), right ventricular ejection fraction (55% vs 58%), or positive late gadolinium enhancement (29% vs 24%).

CONCLUSIONS

Among patients with malignant arrhythmias, the presence of LP does not distinguish between patients with normal and abnormal RV structure or function on CMR. LP may indicate the presence of an arrhythmic heart disease beyond what can be inferred from CMR. The frequent finding of late potentials indicates that the diagnostic value of LP as an ARVC criteria should be tested in larger studies comparing ARVC patients and controls.

Exercise testing for long-term follow-up in arrhythmogenic right ventricular cardiomyopathy

OBJECTIVES

We investigated arrhythmia, electrocardiography and physical work capacity (PWC) in the follow-up of ARVC.

DESIGN

Twenty-three patients (13 men; age 41±12years) fulfilling diagnostic criteria were re-investigated after at least five years.

RESULTS

Ventricular arrhythmia during exercise testing (ET) was present in 14 patients (61%) and showed variation between examinations. In eleven (48%), complex ventricular ectopic activity was observed at peak exercise or immediately thereafter. Mutations known to be pathogenic in ARVC were present in 13 patients (57%) of which 11 developed complex ventricular arrhythmia at ET. PWC at baseline was 190±66W (104±26%) decreasing to 151±61W (91±23%, p=0.008) after 10.7years.

CONCLUSION

The appearance of ventricular arrhythmia during exercise testing showed temporal variation but was frequent in patients with relevant genetic mutation. Physical exercise capacity decreased over time in patients with ARVC in excess to the age-related deterioration and regardless of medication.

Analysis of Abnormal Intra-QRS Potentials in Signal-Averaged Electrocardiograms Using a Radial Basis Function Neural Network

Abnormal intra-QRS potentials (AIQPs) are commonly observed in patients at high risk for ventricular tachycardia. We present a method for approximating a measured QRS complex using a non-linear neural network with all radial basis functions having the same smoothness. We extracted the high frequency, but low amplitude intra-QRS potentials using the approximation error to identify possible ventricular tachycardia. With a specified number of neurons, we performed an orthogonal least squares algorithm to determine the center of each Gaussian radial basis function. We found that the AIQP estimation error arising from part of the normal QRS complex could cause clinicians to misjudge patients with ventricular tachycardia. Our results also show that it is possible to correct this misjudgment by combining multiple AIQP parameters estimated using various spread parameters and numbers of neurons. Clinical trials demonstrate that higher AIQP-to-QRS ratios in the X, Y and Z leads are visible in patients with ventricular tachycardia than in normal subjects. A linear combination of 60 AIQP-to-QRS ratios can achieve 100% specificity, 90% sensitivity, and 95.8% total prediction accuracy for diagnosing ventricular tachycardia.

Cell junctions in the specialized conduction system of the heart

Anchoring cell junctions are integral in maintaining electro-mechanical coupling of ventricular working cardiomyocytes; however, their role in cardiomyocytes of the cardiac conduction system (CCS) remains less clear. Recent studies in genetic mouse models and humans highlight the appearance of these cell junctions alongside gap junctions in the CCS and also show that defects in these structures and their components are associated with conduction impairments in the CCS. Here we outline current evidence supporting an integral relationship between anchoring and gap junctions in the CCS. Specifically we focus on (1) molecular and ultrastructural evidence for cell-cell junctions in specialized cardiomyocytes of the CCS, (2) genetic mouse models specifically targeting cell-cell junction components in the heart which exhibit CCS conduction defects and (3) human clinical studies from patients with cell-cell junction-based diseases that exhibit CCS electrophysiological defects.