Time-varying spectral analysis of heart rate and left ventricular pressurevariability during balloon coronary occlusion in humans - A sympathoexcitatory response to myocardial ischemia

OBJECTIVES We assessed time-varying spectral components of heart rate and l eft ventricular (LV) pressure variability during coronary angioplasty to el ucidate dynamic autonomic responses to transient myocardial ischemia. BACKGROUND Sympathoexcitatory reflexes elicited by acute coronary occlusion are rarely addressed in the clinical settings because of a lack of techniq ue to monitor transient changes in sympathetic activation. METHODS RR interval and LV pressure and volume were serially recorded in 14 patients with effort angina during balloon coronary angioplasty. Wavelet a nalysis was applied for determination of nonstationary spectral components of RR interval and LV peak pressure variability. RESULTS The wavelet analysis revealed that coronary occlusion provoked low- frequency (LF) fluctuations of RR interval (seven patients) and LV peak pre ssure (six patients) at 0.06 +/- 0.01 Hz, but not in the remaining patients . Following the balloon inflation, the LF component of RR interval began to increase after the onset of myocardial ischemia, peaked at about 80 s, and then declined in the: late phase of inflation. Consequently, the ratio of low to high frequency component rose to be significantly greater in the LF augmentation group than in the no LF augmentation group in the middle phase of coronary occlusion. The patients with no LF augmentation had little evi dence of myocardial ischemia as reflected by changes in ST segment and LV s ystolic function during coronary occlusion. CONCLUSIONS The wavelet analysis of RR interval and LV pressure variability clearly showed a dynamic profile of spectral components in response to tra nsient coronary artery occlusion. The resultant regional myocardial ischemi a elicited a profound sympathoexcitatory response followed by a gradual sup pression. This method provides a useful tool to gain a new insight into the nonstationary autonomic influence on the cardiovascular system. (C) 1999 b y the American College of Cardiology.