Familial cardiomyopathy underlies syndrome of right bundle branch block, ST segment elevation and sudden death.

OBJECTIVES: We sought to assess whether structural heart disease underlies the syndrome of right bundle branch block, persistent ST segment elevation and sudden death. BACKGROUND: Ventricular fibrillation and sudden death may occur in patients with a distinctive electrocardiographic (ECG) pattern of right bundle branch block and persistent ST segment elevation in the right precordial leads. METHODS: Sixteen members of a family affected by this syndrome underwent noninvasive cardiac evaluation, including electrocardiography, Holter ambulatory ECG monitoring, stress testing, echocardiography and signal-averaged electrocardiography; two patients had electrophysiologic and angiographic study. Endomyocardial biopsy was performed in one living patient, and postmortem examination, including study of the specialized conduction system, was performed in one victim of sudden death. RESULTS: Five years before a fatal cardiac arrest, the proband had been resuscitated from sudden cardiac arrest due to recorded ventricular fibrillation. Serial ECGs showed a prolonged PR interval, right bundle branch block, left-axis deviation and persistent ST segment elevation in the right precordial leads, in the absence of clinical heart disease. Postmortem investigation disclosed right ventricular dilation and myocardial atrophy with adipose replacement of the right ventricular free wall as well as sclerotic interruption of the right bundle branch. A variable degree of right bundle branch block and upsloping right precordial ST segment was observed in seven family members; four of the seven had structural right ventricular abnormalities on echocardiography and late potentials on signal-averaged electrocardiography. A sib of the proband also had a prolonged HV interval, inducible ventricular tachycardia and fibrofatty replacement on endomyocardial biopsy. CONCLUSIONS: An autosomal dominant familial cardiomyopathy, mainly involving the right ventricle and the conduction system, accounted for the ECG changes and the electrical instability of the syndrome.

Signal-averaged electrocardiography in familial form of arrhythmogenic right ventricular cardiomyopathy.

This study was performed to establish whether signal-averaged electrocardiography can aid in the diagnosis of the familial form of arrhythmogenic right ventricular cardiomyopathy in order to determine the severity of the disease and to predict ventricular arrhythmias. In arrhythmogenic right ventricular cardiomyopathy there is a fatty fibrous substitution of myocardium, which is the substrate for delayed myocardial activation; this is responsible for the abnormalities seen on the signal-averaged electrocardiogram (SAECG). Seventy-five members of 11 families, both healthy and with various forms of the disease, were studied using a signal-averaged electrocardiographic technique. Forty-seven members, 16 with a severe and 31 with a minor form of the disease, were found to be affected. Forty-three subjects had abnormal results on the SAECG; of these, 39 had the disease (100% in patients with widespread disease and 74.1% in patients with a minor form), whereas the other 4 had no sign of the disease. Only 44.1% of the subjects with an abnormal SAECG had ventricular arrhythmias, whereas 76% of the subjects with ventricular arrhythmias had an abnormal SAECG. In contrast, 90.6% of patients with an abnormal SAECG had the disease, and only subjects with arrhythmogenic right ventricular cardiomyopathy had ventricular arrhythmias. The abnormality on the SAECG appears to be correlated with the severity of the disease. Signal-averaged electrocardiography does not seem useful in diagnosing the minor forms of the disease and it does not give precise information about electrical instability in these patients.

The effects of sympathetic stimulation induced by mental stress on signal-averaged electrocardiogram.

We evaluated the influence of sympathetic stimulation, induced by mental stress test, on signal-averaged ECG in 30 healthy subjects and in 30 patients with previous myocardial infarction. Both patient and control groups underwent three consecutive signal-averaged ECG: under basal conditions, during a continuous mental stress test, and 5 min after the mental stress test. The signal-averaged ECG parameters, analyzed by mean of a bandpass filter of 25-250 and 40-250 Hz, were: the filtered QRS duration, the duration of the low-amplitude high frequency signals in the terminal portions of the QRS complex below 40 microV (HFLA), and the root mean square voltage in the last 40 ms of the filtered QRS (RMS). The mathematical stress test was considered effective when the heart rate increased by at least 15 beats/min, remaining stable for the total duration of the signal-averaged ECG acquisition. A significant reduction of the filtered QRS duration and HFLA with a simultaneous increase of RMS were found in control group, while no significant changes occurred in patient group. These results indicate that the sympathetic nervous system may affect the results of signal-averaged ECG, probably by influences on intraventricular conduction, in healthy subjects. On the contrary, myocardial alterations in ischemic heart disease induce modification of signal-averaged ECG not influenced by autonomic nervous system activity.