EFFECT OF BETA-BLOCKADE ON HEART-RATE-VARIABILITY DURING VESSEL OCCLUSION AT THE TIME OF CORONARY ANGIOPLASTY

Beta blockers modify cardiovascular neural regulation, which may contr ibute to their protective effect against sudden cardiac death. To eval uate the effects of beta blockade on cardiovascular autonomic reaction s caused by acute coronary occlusion in humans, heart rate (HR) variab ility was analyzed in the time and frequency domains immediately befor e and during balloon occlusion of a coronary artery in 116 patients ra ndomly assigned to either chronic beta-blocker therapy (beta-blocker g roup) or no beta blockade (control group)during elective 1-vessel coro nary angioplasty. Coronary occlusion (mean 112 seconds) caused a signi ficant increase in both the high- and low-frequency components of HR v ariability in the control group (n = 58), from 2.7 +/- 1.6 to 3.4 +/- 1.7 (logarithmic units, p <0.001) and from 4.3 +/- 1.3 to 4.8 +/- 1.5 (p <0.01), respectively, whereas in the beta-blocker group (n = 58), t he high-frequency power did not change during occlusion, but the low-f requency power increased from 3.9 +/- 1.4 to 4.4 +/- 1.4 (p = 0.01). C hanges in high- and low-frequency components and HR were related to th e change in systolic blood pressure during occlusion in the beta-block er group (r = 0.53, p <0.001; r = 0.34, p <0.05; and r = -0.41, p <0.0 1, respectively), but not in the control group (r = -0.17, r = -0.14, and r = 0.24 respectively). Thus, beta blockade attenuates the initial vagal activation; associated with acute coronary occlusion and seems to maintain baroreflex-mediated cardiovascular control. The maintained integrity of baroreflex regulation and the alleviation of extreme aut onomic reactions during beta blockade may modify the clinical outcome of acute coronary occlusion in a beneficial way.