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CLINICAL STUDIES

Time-varying spectral analysis of heart rate and left ventricular pressure variability during balloon coronary occlusion in humans

A sympathoexcitatory response to myocardial ischemia

Shuji Joho, MD^*, Hidetsugu Asanoi, MD^*, Hosam A. Remah, MD^*, Akihiko Igawa, MD^*, Tomoki Kameyama, MD^*, Takashi Nozawa, MD^*, Katsumi Umeno, BS and Hiroshi Inoue, MD, FACC^*

^* Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Toyama, Japan
the First Department of Physiology, Toyama Medical and Pharmaceutical University, Toyama, Japan

Manuscript received August 18, 1998; revised manuscript received July 1, 1999, accepted August 30, 1999.

Reprint requests and correspondence: Dr. Hidetsugu Asanoi, Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan
hidetugu{at}ms.toyama-mpu.ac.jp

OBJECTIVES

We assessed time-varying spectral components of heart rate and left ventricular (LV) pressure variability during coronary angioplasty to elucidate 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 technique 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 analysis 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 pressure (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 evidence of myocardial ischemia as reflected by changes in ST segment and LV systolic 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 transient coronary artery occlusion. The resultant regional myocardial ischemia elicited a profound sympathoexcitatory response followed by a gradual suppression. This method provides a useful tool to gain a new insight into the nonstationary autonomic influence on the cardiovascular system.

Abbreviations and Acronyms   ECG = electrocardiogram   HF = high-frequency   LF = low-frequency   LV = left ventricular   RR = relative risk   Tau = time constant of isovolumic left ventricular pressure

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