Heart rate variability during repeated arterial occlusion in coronary angioplasty

Acute coronary occlusion may cause severe autonomic reactions that can modify the clinical presentation of acute ischemic events. To evaluate whether adaptation in these autonomic reactions exists during repeated short coronary occlusions, heart rate (HR) and its variability in the time and frequency domains were analyzed in 70 patients with significant (50% to 95%) coronary artery stenosis immediately before and during 2 identical balloon occlusions of the vessel (mean 110 seconds). Reactions were compared with the range of nonspecific changes formed by analyzing a control group (n = 13) with no ischemia during balloon inflation in a totally occluded coronary artery. Thus, neither occlusion caused significant changes in HR or HR variability in 29 patients (41%). Vagal activation, as seen by an abnormal increase in HR variability or bradycardia, or both, was observed in 24 patients (34%). HR reactions in this group (p < 0.05) were significantly attenuated during the second occlusion. An opposite reaction (i.e., abnormal decrease in HR variability or tachycardia, or both) was observed in 17 patients (24%). A nonsignificant tendency for attenuation of the reactions was also seen in this group. Severity of chest pain, frequency of ST-segment shifts, or narrowing of pulse pressure were comparable during the 2 occlusions. Thus, a preceding short vessel occlusion-reperfusion cycle seems to attenuate autonomic HR reactions, especially vagal reactions, during subsequent coronary occlusion. Alleviation of extreme autonomic reactions may modify the clinical outcome of coronary occlusion in a beneficial way.