Electrophysiologic abnormalities of cardiac function in progressive systemic sclerosis.

The heart has been generally recognized as a target organ in progressive systemic sclerosis. Noninvasive studies have assessed the incidence and prognostic importance of cardiac arrhythmias in these patients. However, detailed exploration of the function of impulse formation and the conduction system of the heart in these patients has never been reported. Therefore, invasive electrophysiologic studies were performed in 30 patients with systemic sclerosis, all of whom had neither obvious cardiac involvement nor cardiac arrhythmias, and in 32 subjects with no evidence of heart disease, who served as a control group. Corrected sinus node recovery time in patients with systemic sclerosis was significantly longer (P < .001) than in the control group, as was the HV interval (P < .05). Of the 30 patients with systemic sclerosis, 10 had an HV interval of 60 ms or longer. In four patients with systemic sclerosis, the recorded AH interval exceeded 125 ms. The intra-atrial conduction time tended to increase to a significant degree (P < .05) in patients with systemic sclerosis. The interatrial conduction time was much longer (P < .001), and the maximal conduction delay to the atrioventricular junction and to the distal coronary sinus was much greater in the patients with systemic sclerosis than in the control group (P < .001 for both). Supraventricular tachyarrhythmias were induced in 15 patients with systemic sclerosis versus 3 control group subjects (P < .001). With respect to corrected sinus node recovery time, AH and HV intervals, atrial vulnerability, and ventricular tachycardia, 3 of the 30 patients with systemic sclerosis had abnormal findings in one of these parameters and 14 had abnormalities in more than one. These results suggest that a broad spectrum of electrophysiologic abnormalities is present in patients with systemic sclerosis, which can be revealed only by invasive studies. Furthermore, this study provides additional support for the hypothesis that diffuse myocardial involvement is characteristic of scleroderma patients, since a number of these patients showed more than one electrophysiologic defect.