The Effects of Increase in Heart Rate on Coronary Flow Reserve and Flow Profiles : A Study with Intracoronary Doppler Wire

ABSTRACT

BACKGROUND: Measurements of coronary flow reserve(CFR) and phasic coronary flow profile are useful in assessment of the physiologic significance of coronary lesions. However, alterations in hemodynamic status are known to influence coronary flow reserve. The purpose of this study was to assess the effect of increase in heart rate on maximal pharmacologin coronry flow reserve and phasic flow pattern. METHODS: We investigated 12 patients(9 females and 3 males, mean age 49+/-12 years) with normal coronary artery and atypical chest pain syndrome for the measurement of CFR and coronary flow profile. CFR and systolic and diastolic coronary flow velocity integral(CFVI) were measured at the proximal portion of left anterior descending artery with 0.018 inch(12MHz) Doppler guide wire before and during intracoronary injection of 12 mcg of adenosine. The heart rate at the baseline ranging from 62 beats/min to 79 beats/min(mean 70+/-5 beats/min) was increased to 100 beats/min and again to 120 beats/min by right atrial pacing. RESULTS: CFR progressively decreased from 3.0+/-0.5 at baseline to 2.4+/-0.4 during pacing at 100 beats/min and to 2.0+/-0.3 during pacing at 120 beats.min(p0.05). Systolic CFVI/min was increased at baseline(185+/-35% at 120 beats/min, p0.05). CONCLUSION: Increase in heart rate induces a substantial reduction in maximal CFR. Thus,heart rate appears to be one of important variable for the measurement of CFR and phasin coronary flow profile.