Enhanced vagal modulation and exercise induced ischaemia of the inferoposterior myocardium

Abstract

Objective: To determine whether the Bezold-Jarisch reflex or enhancement of vagal nerves, which are preferentially distributed in the inferoposterior myocardium, results from exercise induced ischaemia in this region. Methods: On the basis of exercise myocardial scintigraphy and coronary angiography, 145 patients were classified as follows: group I, 34 patients with inferoposterior ischaemia; group A, 32 with anterior ischaemia; and control, 79 without ischaemia. The relation between ischaemic areas and ECG leads with ST segment changes and vagal modulation assessed by heart rate variability (HRV) (high frequency (HF) component (0.15-0.40 Hz) and coefficient of HF component variance (CCV HF ), which is the square root of HF divided by mean RR interval) were assessed. 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 the control group after exercise (mean (SEM) HF: 94 (17) ms 2 , 41 (7) ms 2 , and 45 (6) ms 2 , respectively, p = 0.021; CCV HF : 1.18 (0.09)%, 0.81 (0.07)%, and 0.89 (0.05)%, p = 0.0053). Furthermore, the percentage change in CCV HF before and after exercise was higher in group I than in group A or controls (mean (SEM) 22 (10)%, 224 (4)%, and 221 (3)%, p , 0.0001). The optimal cut off for diagnosis of inferoposterior ischaemia was 25% with a sensitivity of 74%, specificity 75%, and accuracy 75%. Conclusions: Vagal modulation as assessed by HRV analysis was enhanced in association with exercise induced inferoposterior ischaemia. Exercise ECG testing combined with HRV analysis would increase accuracy in the diagnosis of ischaemic areas in selected patients with angina pectoris.A cute myocardial infarction in the left ventricular (LV) inferoposterior wall is often associated with transient hypotension along with sinus bradycardia.

Vagal enhancement due to subendocardial ischemia as a cause of abnormal blood pressure response in hypertrophic cardiomyopathy

“…However, reversible regional perfusion abnormality involving inferoposterior wall was associated with vagal enhancement despite disproportional sample size of our patients. A similar cardioinhibitory response or Bezold-Jarisch reflex has been observed in the myocardial infarction and/or ischemia involving the inferoposterior wall [10,14], in which vagal nerve distribution is also predominant [26][27][28][29]. In the present results, however, the contribution of BezoldJarisch reflex to abnormal blood pressure response is not considered large compared to that in our previous report [10]; only 1/3 patients with reversible regional perfusion abnormality in inferoposterior wall showed abnormal blood pressure response and 4/5 patients with abnormal blood pressure response did not show regional perfusion abnormality in inferoposterior wall in the present HCM patients.…”

“…Beat-to-beat heart rate data during exercise testing were sampled at a frequency of 500 Hz using personal computer and software (MemCalc/Tarawa, GMS, Tokyo, Japan) as previous described [10]. High frequency component (HF, 0.15-0.40 Hz) was used in the estimation of vagal modulation from short-duration recordings [19][20][21]; HF was extracted every minute and averaged for 5 min immediately before exercise and immediately after a cool-down period following exercise.…”

“…Furthermore, we calculated the root mean square of the differences between adjacent RR intervals (RMSSD), which also can be obtained from a short-term recording and predominantly reflects vagal modulation [21]. To examine vagal responses to exercise, percentage changes from before to after exercise in HF, CCV HF , and RMSSD were calculated [10].…”

“…The neural balance is affected by myocardial ischemia [7][8][9][10] that is not rare in patients with HCM [11][12][13]. Myocardial ischemia has been reported to be a possible trigger for abnormal blood pressure response [13]; vagal nerves are known to mediate depressor stimuli including abnormal blood pressure response in the cardiovascular system [14,15].…”

Listening to Heart Rate for Myocardial Ischemic Site

“…This phenomenon is known as Bezold-Jarisch reflex, which has been explained by the preferential distribution of cardiac receptors along afferent vagal pathways in the inferior wall of the left ventricle [4]. We previously reported that the vagal modulation as assessed by HF and CCV HF was enhanced through exercise-induced myocardial ischemia of the inferoposterior myocardium [5]. Thus, in the present case, the combination of vagal enhancement provoked by exercise-induced inferior ischemia and sustainment of sympathetic activation after exercise possibly led to audibly perceptible heart rate fluctuation without bradycardia or hypotension.…”