[The new indications for permanent cardiac pacing].

In spite of conflicting data from several studies, pacing is being used in several indications beyond the classic ones, namely to treat patients with hypertrophic cardiomyopathy, severe heart failure and to prevent atrial fibrillation. In this article the authors briefly review the new indications for this therapeutic intervention and discuss the utilization criteria, the technical details and the results of trials with dual-chamber pacing in patients with hypertrophic cardiomyopathy and severe heart failure. In obstructive hypertrophic cardiomyopathy, dual-chamber pacing significantly reduces the gradient and improves symptoms. Criteria suggested for the application of pacemaker therapy are: 1) persistent symptoms in spite of an adequate medical therapy trial (i.e., B-blockers, calcium antagonists, disopyramide): 2) left ventricular tract gradients of > 30 mmHg at rest or > 50 mmHg with provocation. In heart failure (NYHA class III ou IV with ejection fraction < 35) only a small percentage seems to benefit from this new therapeutic approach. They are those with a long PR interval on the surface electrocardiogram, with presystolic mitral regurgitation and with abbreviated diastolic filling period on the mitral inflow velocity on Doppler echocardiography. On the basis of some preliminary results, it appears that pacing may decrease the frequency of paroxysms of atrial fibrillation in some patients with vagal mediated fibrillation, chronotropic incompetence and those with long interatrial conduction times. Noninvasive detection of acute cardiac allograft rejection in heart transplant recipients by the analysis of some pacing parameters with telemetry is, at present, in an experimental stage.