Can right-sided atrioventricular sequential pacing provide benefit for selected patients with severe congestive heart failure?

This study reports on the methods and results of applying right-sided atrio ventricular (AV) pacing in 26 patients with advanced cardiomyopathy. Ten of these patients had ischemic cardiomyopathy. Of the 16 patients with nonisc hemic cardiomyopathy, 10 were idiopathic and 6 were due to secondary causes . The patients had a mean age of 56 +/- 12 years and a left ventricular eje ction fraction of 26 +/- 11%. Two transvenous stimulation electrodes were t emporarily placed in the high right atrium and right ventricle, respectivel y. A Swan Ganz catheter was positioned into the pulmonary artery to determi ne cardiac output by the thermodilution method and to measure the pressure in the pulmonary artery and right atrium. In addition, aortic pressure was measured through a catheter sheath via the right femoral artery. Systemic a nd pulmonary vascular resistance were calculated. Stimulation was performed in VVI and DDD pacing modes using different AV intervals (40, 80, 125, 150 , 175, 200, and 250 msec). No increase of cardiac output was observed far t he overall study cohort (p = 0.51). At VVI pacing, stroke volume significan tly decreased from 66 +/- 20 mL to 53 +/- 13 mL (p < 0.01). We distinguishe d between responders who developed an increase of cardiac output of >1L/min (n = 12, 46%) and nonresponders (n = 14, 54%). Etiology of either ischemic or nonischemic cardiomyopathy for responders, as well as conduction distur bances (first-degree AV block, LBBB, RBBB), were equally distributed among both groups. Using an AV delay of 150 and 175 msec, responders to DDD pacin g derived a significant increase in cardiac output. An AV delay of 150 msec produced both a significant increase of strake volume and decrease of syst emic vascular resistance. In 46% of patients with dilated cardiomyopathy of either ischemic or nonischemic origin, right-sided AV-sequential pacing br ought about an improvement of left ventricular function in terms of enhance d cardiac output. We suggest individual testing in all patients with severe left ventricular dysfunction to find responders. (C) 1999 by Excerpta Medi co, Inc.