Cardiac arrhythmias refer to any abnormality or disturbance in the normal activation sequence of the myocardium and may be indicative of structural heart disease and the cause of significant cardiovascular complications and sudden cardiac death. The following review summarizes the current state-of-the-art knowledge on the role of echocardiography in the management of cardiac arrhythmias and focuses on atrial fibrillation and ventricular arrhythmias where echocardiography presents a particular diagnostic and prognostic interest. Moreover, a brief reference is made to the effect of cardiac arrhythmias and conduction abnormalities on echocardiographic examination.

AimsWe investigated the role of endothelin-B receptors on sympathetic activation originating from the adrenal gland or from the myocardium and its impact on arrhythmogenesis during acute myocardial infarction.Main methodsWe studied two groups of rats (n=120, 284±2g), namely wild-type and ETB-deficient. Myocardial infarction was induced by permanent ligation of the left coronary artery and ventricular tachyarrhythmias were evaluated from continuous electrocardiographic recordings. Sympathetic activation, measured by indices of heart rate variability, was evaluated after adrenalectomy or catecholamine depletion induced by reserpine. Acute left ventricular failure was assessed by total animal activity.Key findingsAdrenalectomy decreased the total duration of tachyarrhythmias in ETB-deficient rats, but their incidence remained higher, compared to wild-type rats. After reserpine, heart rate variability indices and tachyarrhythmias were similar in the two groups during the initial, ischaemic phase. During evolving infarction, tachyarrhythmia duration was longer in ETB-deficient rats, despite lower sympathetic activation. Heart rate was lower in ETB-deficient rats throughout the 24-hour observation period, whereas activity was comparable in the two groups.SignificanceEndothelin-B receptors modulate sympathetic activation during acute myocardial infarction not only in the ventricular myocardium, but also in the adrenal gland. Sympathetic activation markedly increases early-phase ventricular tachyarrhythmias, but other mechanisms involving the endothelin system underlie delayed arrhythmogenesis