Arrhythmias, catecholamines and electrolytes.

The prognosis in patients with heart failure secondary to left ventricular dysfunction is poor. Although survival can be related to the extent of cardiac functional impairment, many patients die suddenly rather than in refractory heart failure. Ambulatory electrocardiography has revealed a high prevalence of simple and complex ventricular arrhythmias in these patients, which was the most important predictor of subsequent mortality in our patients. Factors predisposing to arrhythmias are many, but increased catecholamines and electrolyte abnormalities are among the more obvious. In patients who have undergone treatment for congestive heart failure, serum and total body potassium are reduced, and this is closely and inversely related to the state of activation of the renin-angiotensin system. Renin and noradrenaline are also closely and directly correlated, while both are inversely related to the arterial pressure. Treatment with angiotensin-converting enzyme inhibitors tends to reverse these neuroendocrine and electrolyte abnormalities and reduces the frequency of ventricular arrhythmias. Whether this will have a favorable impact on mortality, and, in particular, on sudden death, remains to be seen.