Enhanced vagal modulation and exercise-induced ischemia of the inferoposterior myocardium

Tatsuya Kawasaki ^1*, Akihiro Azuma ², Toshiro Kuribayashi ³, Takuya Taniguchi ¹, Satoshi Asada ¹, Tadaaki Kamitani ¹, Shingo Kawasaki ¹, Hiroaki Matsubara ² and Hiroki Sugihara ¹

¹ Department of Cardiology, Matsushita Memorial Hospital, Japan
² Department of Cardiovascular Medicine, Kyoto Prefectural University Graduate School of Medicine, Japan
³ Kuribayashi Clinic of Cardiology, Japan

^* To whom correspondence should be addressed. E-mail: js-k{at}wf6.so-net.ne.jp.

Accepted 2 June 2005

Abstract

Objective: To determine whether Bezold-Jarisch reflex or enhancement of vagal nerves, which are preferentially distributed in the inferoposterior myocardium, results from exercise-induced ischemia in this region.

Methods: Based on exercise myocardial scintigraphy and coronary angiography, 145 subjects were classified into: Group I, 34 with inferoposterior ischemia; Group A, 32 with anterior ischemia; and control, 79 without ischemia. We analyzed the relationship of ischemic areas to electrocardiographic leads with ST-segment changes and vagal modulation assessed by heart rate variability (HRV): high frequency component (HF, 0.15-0.40 Hz) and coefficient of component variance (CCV_HF, square root of HF/mean RR interval).

Results: The rate of ST-segment depression in any lead did not differ between Group I and Group A. HF and CCV_HF were similar before exercise but higher in Group I than in Group A and control after exercise (HF, mean (SEM) 94 (17) ms², 41 (7) ms², 45 (6) ms², p = 0.021; CCV_HF, 1.18 (0.09)%, 0.81 (0.07)%, 0.89 (0.05)%, p = 0.0053). Furthermore, the percentile change in CCV_HF before and after exercise was higher in Group I (mean (SEM) 22 (10)%, -24 (4)%, -21 (3)%, p < 0.0001); the optimal cutoff for diagnosis of inferoposterior ischemia was -5% with a sensitivity of 74%, a specificity of 75%, and an accuracy of 75%.

Conclusions: The vagal modulation as assessed by HRV analysis was enhanced in association with exercise-induced inferoposterior ischemia. Exercise electrocardiographic test combined with HRV analysis will increase accuracy in the diagnosis of ischemic areas in selected patients with angina pectoris.

Keywords: Bezold-Jarisch reflex, autonomic nervous system, heart rate, ischemia, vagal nerve

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