FIXED RATE VERSUS RATE-RESPONSIVE VENTRICULAR PAClNG EXERCISE PERFORMANCE & HAEMODYNAMIC ASSESSMENT USING ECHOCARDIOGRAPHY

Abstract

To assess the effects of physiologic rate variation during cardiac pacing on exercise performance and haemodynamics, :-ve studied 24 patients (9 males, 14 females) V.iih the mean age (40 years) in whom permanent pacemakers had to be implanted for complete heart block (21 pts), sinus mode disease (1 pt) and binodal disease (2 pts). The implanted pacemakers were all of the rate­ responsive type; namely (Meta 1202, Telectronics) where rate variation is triggered by hyperventilation. Studies were conductde in both the fixed rate mode at optimum heart rate and the rate-responsive mode in the same .patient at two different days. Parameters assessed included echo-Doppler evaluation of stroke volume (SV), cardiac output (CO), cardiac index (CI) and treadmill exercise performance, expressed as the percentage increase in the time spent on the treadmill in rate responsive mode compared with fixed rate mode at optimum heart rate in the same group of pts. Following implantation, CO was measured by usmg the impedance cardiography at various heart rates to construct a rate-output curve and to determine the ,?Ptimum heart rate yielding the highst CO in the fixed rate mode. Echo-Doppler was carried out to measure SV, CO in both fixed rate mode programmed at (OHR) and in rate-responsive mode before and immediately after treadmill exercise testing.