931-108 Parasympathetic Intervention Affects Ischemia by Increasing Coronary Flow in Normal, but not in Impaired Left Ventricular Function. A New Approach to Antiischemic Therapy?

Abstract

Cardiovascular parasympathetic control reportedly is reduced in left ventricular (LV) dysfunction and in heart-failure. To evaluate whether parasympathetic intervention differentially affects coronary flow and ischemia in normal (N) vs impaired (I = ejection fraction < 40%) LV-function, 17 pts in N and 7 pts in I received atropine before ischemia was induced by incremental atrial pacing. Placebo was administered to a matching control group (CN and CI, resp.). All pts had > 70% left CAD. During maximal pacing, heart rate and rate pressure product (myocardial oxygen demand) where 7% and 12% higher in N, compared to CN, but were comparable in I and CI. Moreover, 1 minute post pacing these values were 8% and 12% higher, resp., N vs CN. Vasoconstrictive circulating neurohormones (norepinephrine) increased similarly in all groups. Coronary flow increased 23% more in N than in CN and to a similar extent in I and CI. Myocardial ischemia, as indicated by changes in myocardial lactate metabolism, was less in N [lactate extraction +10% (N) vs -21% (CN), -18% (I) and -19% (CI)]. Fifteen minutes after pacing, coronary flow was still decreased by 11% and coronary vascular resistance increased by 15% in CN, as compared to N. Thus, reduction of parasympathetic tone improves coronary flow and reduces myocardial ischemia in the latter, despite similar sympathetic activation and more pronounced myocardial oxygen demand in N. This supports a greater role for cardiovascular parasympathetic control of (diseased) coronary arterial system in normal LV-function and, possibly, a new area of intervention in antiischemic therapy in the latter.