PubMed · 14975570
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C G Sajeev, T G Jayakumar, M N Krishnan, K Venugopal. 2004. Epsilon wave.. https://doi.org/10.1016/s0167-5273(03)00167-0
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The arrhythmogenic right ventricular dysplasia/cardiomyopathy is an important cause of sudden arrhythmic death, often exertional, in young individuals and athletes. Although the aetiology remains partially unknown, genetic abnormalities have been demonstrated. Reported prevalence is 1 in 5000 individuals but it is considered there are many non-diagnosed cases. The characteristic pathologic finding is the progressive fibro-fatty replacement of the right ventricular myocardium. The clinical manifestations vary from asymptomatic patients with an episode of sudden cardiac death as first symptom to chronically symptomatic patients with recurrent palpitations and/or right or biventricular failure. Approximately a third of the patients show the characteristic Epsilon wave in the 12-lead ECG which is a useful screening test. Signal-averaged ECG frequently demonstrates late potentials. The two-dimensional echocardiography, magnetic resonance imaging, computerized tomography and right ventricular cineangiography show morphologic abnormalities in the right ventricle. Therapy is directed to prevent and/or treat malignant ventricular tachyarrhythmias with medications, implantable cardioverter defibrillator and radiofrequency ablation in selected cases.
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterised by progressive fibro-fatty replacement of right ventricular myocardium. Earlier studies described ARVC as non-inflammatory, non-coronary disorder associated with arrhythmias, heart failure and sudden death due to functional exclusion of the right ventricle. Molecular genetic studies have identified nine different loci associated with ARVC; accordingly each locus is implicated for each type of ARVC (ARVC1-ARVC9). So far five genes have been identified as containing pathogenic mutations for ARVC. Though mutations in each of the gene/s indicate disruption of different pathways leading to the condition, the exact pathogenesis of the condition is still obscure. This review tries to understand the pathogenesis of the condition by examining the individual proteins implicated and relate them to the pathways that could play a role in the aetiology of the condition. Cardiac ryanodine receptor (RYR-2), which regulates intra-cellular Ca(2+) concentration by releasing Ca(2+) reserves from the sarcoplasmic reticulum (SR), was the first gene for ARVC. The mutation in this gene is believed to disrupt coupled gating of RYR-2, causing after-depolarisation, leading to arrhythmias followed by structural changes due to altered intra-cellular Ca(2+) levels. Three other genes implicated for ARVC, plakoglobin (Naxos disease), desmoplakin (ARVC8) and plakophilin (ARVC9) have prompted the speculation that ARVC is primarily a disease of desmosomes. But identification of TGFbeta-3 for ARVC1 and the role of all these three genes (plakoglobin, desmoplakin and plakophilin) in cardiac morphogenesis indicate some kind of signal-transducing pathway disruption in the condition. The finding that ARVC as a milder form of Uhl's anomaly indicates similar ontogeny for the condition. Further, discovery of apoptotic cells in the autopsy of the right ventricular myocardium of ARVC patients does indicate a common pathway for different types of ARVCs, which is more specific for the right ventricular myocardium involving desmosomal plaque proteins, growth factors and Ca(2+) receptors.
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