“Benign” early repolarization versus malignant early abnormalities: Clinical-electrocardiographic distinction and genetic basis
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In the great majority of cases the ECG pattern of early repolarization (ERP) is a benign phenomenon observed predominantly in teenagers, young adults, male athletes and the black race. The universally accepted criterion for its diagnosis is the presence, in at least two adjoining leads, of ≥ 1 mm or 0.1 mV ST segment elevation. In benign ERP reciprocal ST segment changes are possible only in lead aVR. In contrast, reciprocal ST segment changes can be observed in several leads in idiopathic ventricular fibrillation (IVF) and acute coronary syndrome. In benign ERP the ST segment and T wave patterns have a relative temporal stability. IVF is an entity with low prevalence, possibly familiar, and characterized by the occurrence of VF events in a young person. More frequently this occurs in male subjects without structural heart disease and with otherwise with normal ECG even using high right accessory leads and/or after ajmaline injection. Several clinical entities cause ST segment elevation include asthenic habitus, acute pericarditis, ST segment elevation myocardial infarction, Brugada syndrome, congenital short QT syndrome, and idiopathic VF. In these circumstances clinical and ECG data are most important for differential diagnosis. In IVF the modifications could be dramatic and predominantly at night during vagotonic predominance when J waves > 2 mm in amplitude. The ST/T abnormalities are dynamic, inconstant, and reversed with isoproterenol. Convex upward J waves, with horizontal/descending ST segments or "lambda-wave" ST shape are suggestive of IVF with early repolarization abnormalities. Premature ventricular contractions with very short coupling and "R on T" phenomenon are characteristics with two pattern: When originate from right ventricular outflow tract left bundle branch block morphology and from peripheral Purkinje network, left bundle branch block pattern. The inherited-familial forms are not frequent in IVF; however mutations were identified in the genes KCNJ8, DPP6, SCN5A, SCN3B, CACNA1C, CACNB2, and CACNA2D1. The management of IVF has class I indication for ICD implantation. Ablation therapy is considered additional to ICD implantation in those patients with repetitive ventricular arrhythmia. Quinidine is a highly efficient drug that prevents recurrence.
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