Conduction abnormalities in arrhythmogenic right ventricular cardiomyopathy

Sudden Unexpected Death Associated with Arrhythmogenic Cardiomyopathy: Study of the Cardiac Conduction System

A retrospective study was conducted on pathologically diagnosed arrhythmogenic cardiomyopathy (ACM) from consecutive cases over the past 34 years (n = 1109). The anatomo-pathological analyses were performed on 23 hearts diagnosed as ACM (2.07%) from a series of 1109 suspected cases, while histopathological data of cardiac conduction system (CCS) were available for 15 out of 23 cases. The CCS was removed in two blocks, containing the following structures: Sino-atrial node (SAN), atrio-ventricular junction (AVJ) including the atrio-ventricular node (AVN), the His bundle (HB), the bifurcation (BIF), the left bundle branch (LBB) and the right bundle branch (RBB). The ACM cases consisted of 20 (86.96%) sudden unexpected cardiac death (SUCD) and 3 (13.04%) native explanted hearts; 16 (69.56%) were males and 7 (30.44%) were females, ranging in age from 5 to 65 (mean age ± SD, 36.13 ± 16.06) years. The following anomalies of the CCS, displayed as percentages of the 15 ACM SUCD cases in which the CCS has been fully analyzed, have been detected: Hypoplasia of SAN (80%) and/or AVJ (86.67%) due to fatty-fibrous involvement, AVJ dispersion and/or septation (46.67%), central fibrous body (CFB) hypoplasia (33.33%), fibromuscular dysplasia of SAN (20%) and/or AVN (26.67%) arteries, hemorrhage and infarct-like lesions of CCS (13.33%), islands of conduction tissue in CFB (13.33%), Mahaim fibers (13.33%), LBB block by fibrosis (13.33%), AVN tongue (13.33%), HB duplicity (6.67%%), CFB cartilaginous meta-hyperplasia (6.67%), and right sided HB (6.67%). Arrhythmias are the hallmark of ACM, not only from the fatty-fibrous disruption of the ventricular myocardium that accounts for reentrant ventricular tachycardia, but also from the fatty-fibrous involvement of CCS itself. Future research should focus on application of these knowledge on CCS anomalies to be added to diagnostic criteria or at least to be useful to detect the patients with higher sudden death risks.

Bradyarrhythmias in Arrhythmogenic Right Ventricular Cardiomyopathy

Less is known about bradyarrhythmias in arrhythmogenic right ventricular cardiomyopathy (ARVC). This cross-sectional study aimed to assess the prevalence and clinical significance of bradyarrhythmias in ARVC. From May 1995 to December 2017, bradyarrhythmias including sick sinus syndrome, atrioventricular block, and intraventricular conductional block (ICB) were investigated in 522 ARVC patients. A total of 169 patients (32.4%) presented with bradyarrhythmias including sick sinus syndrome in18 (3.5%), atrioventricular block in 56 (10.7%), and ICB in 118 patients (22.6%). Multivariate analysis showed right atrial dilation increased the risk of bradyarrhythmias (odds ratio [OR] 1.641, 95% confidence interval [CI] 1.081 to 2.492, p= 0.020). Bradyarrhythmias were not associated with death and heart transplantation. In patients with bradyarrhythmias, female gender, left atrial diameter >40 mm, and New York Heart Association Ⅲ/Ⅳ increased the risk of death and heart transplantation (hazards ratio [HR] = 2.790, 95% CI 1.220 to 6.377, p = 0.015; HR = 4.913, 95% CI 2.058 to 11.730, p <0.001; HR = 3.223, 95% CI 1.246 to 8.340, p = 0.016). Among the 23 patients who underwent device implantation, left atrial diameter >40mm was associated with death and heart transplantation (HR = 9.523, 95% CI 1.587 to 57.126, p = 0.014). In conclusion, bradyarrhythmias were commonly seen in ARVC, and ICB was the most common type. Female, left atrial diameter >40 mm, and NYHA class were associated with death and heart transplantation.

Common presentation of rare cardiac diseases: Arrhythmias

Ventricular or supraventricular ectopic beats or atrial fibrillation may be the first presentation of uncommon cardiac disease, both acquired and genetically determined. In some patients, these manifestations can be the first sign of the underlying cardiac disorder. In others, however, they are also important as prognostic indicators, reflecting electrical instability and risk. Most cardiology clinics are busy environments where the implementation of complex diagnostic algorithms is not feasible. However, it is equally impossible to reach a final diagnosis, among the thousands of rare diseases that involve the heart, moving from a first line clinical and instrumental examination. Cardiac and extra-cardiac red flags, an accurate family and clinical history and ECG interpretation may be of help in identifying a rare disease. Advanced imaging and laboratory testing at experienced referral centers is then necessary to reach a final diagnosis, but the first step in the right direction, based on these simple elements, is the most important. We here review arrhythmic presentations of rare or relatively rare diseases, and suggest a simple "rule out-rule in" approach to help direct clinical suspicion and minimize risk of neglect.