Abstract
To assess the effects of pacing-induced tachycardia on phasic coronary blood flow pattern and flow reserve of left anterior descending artery, we examined 16 patients with chest pain and angiographically normal coronary arteries by using an intravascular Doppler catheter with spectral analysis of the velocity signal. The heart rate was increased from a mean of 68 ± 11 beats/min during sinus rhythm to 100 beats/min and again to 120 beats/min. Cross-sectional area of the epicardial artery and resting systolic and diastolic coronary blood flows increased progressively, resulting in an elevation of total coronary flow from 142 ± 54 ml/min during sinus rhythm to 190 ± 66 ml/min at 100 beats/min ( p < 0.05) and to 219 ± 69 ml/min at 120 beats/min ( p < 0.01). During maximal hyperemia with intracoronary injection of 10 to 12 mg of papaverine, there was an increase in the systolic coronary blood flow with a decrease in the diastolic flow, resulting in no significant change in the total flow. These alterations led to progressive reductions in coronary flow reserve from 3.9 ± 0.7 during sinus rhythm to 2.9 ± 0.9 at 100 beats/min ( p < 0.01) and to 2.3 ± 0.3 at 120 beats/min ( p < 0.001). Thus careful consideration should be given to the effects of heart rate when phasic coronary blood flow pattern and flow reserve are assessed.
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