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Interstudy variability of coronary flow reserve. Influence of heart rate, arterial pressure, and ventricular preload
A L McGinn1, C W White, R F Wilson
1Department of Medicine, University of Minnesota, Minneapolis 55455.
Insights
Serial coronary flow reserve (CFR) measurements are reproducible long-term. However, increased heart rate or preload can reduce CFR by affecting resting coronary blood flow velocity, while mean arterial pressure does not significantly alter it.
Area of Science:
- Cardiology
- Physiology
- Medical Imaging
Background:
- Coronary flow reserve (CFR) is a crucial indicator of myocardial perfusion.
- Understanding the long-term variability and influencing factors of CFR is essential for accurate clinical interpretation.
Purpose of the Study:
- To determine the long-term reproducibility of serial CFR measurements in humans.
- To evaluate the impact of heart rate, mean arterial pressure, and left ventricular preload on CFR.
Main Methods:
- Serial CFR measurements were performed in 45 patients with normal left ventricular function using Doppler guidewires and intracoronary papaverine.
- Hemodynamic variables (heart rate, mean arterial pressure, preload) were manipulated via atrial pacing, handgrip exercise, and volume expansion.
Main Results:
- Initial and repeat CFR measurements showed high correlation over approximately 11 months (r=0.95).
- Increased heart rate and preload significantly reduced CFR due to elevated resting coronary blood flow velocity without affecting hyperemic flow.
- Changes in mean arterial pressure did not alter CFR.
Conclusions:
- Serial CFR measurements are highly reproducible in the absence of confounding factors.
- Heart rate and preload significantly influence CFR, necessitating consideration of hemodynamic conditions during measurement.
- Mean arterial pressure does not appear to affect CFR outcomes.
Abstract:
To define the long-term variability of serial coronary flow reserve (CFR) measurements in humans and to evaluate the influence of changes in heart rate, mean arterial pressure, and left ventricular preload on CFR, 45 patients with normal left ventricular function (38 cardiac allograft recipients, five patients with normal coronary arteries, and two patients with minimal coronary artery disease [less than 50% diameter stenosis]) were studied. CFR (ratio of peak hyperemic [h] to resting [r] coronary blood flow velocity [CBFV]) was measured with a 3F coronary Doppler catheter and intracoronary papaverine. Initial CFR measurements were highly correlated with repeat measurements obtained 11 +/- 0.6 months later (r = 0.95; mean absolute difference, 0.3 +/- 0.1; n = 17). Differences in CFR between studies were related to changes in heart rate (r = 0.61, p = 0.01) but not to changes in mean arterial pressure (r = 0.25, p = 0.33). To define the effects of rapid changes in heart rate, mean arterial pressure, and preload on CFR, these variables were altered by atrial pacing, handgrip exercise, and volume expansion, respectively. Atrial pacing produced a rate-related increase in rCBFV but did not change hCBFV. Consequently, CFR was significantly reduced as heart rate was increased progressively from 76 +/- 2 in sinus rhythm (4.5 +/- 0.2) to 100 (3.8 +/- 0.2, p less than 0.05, n = 32) to 120 beats/min (3.2 +/- 0.1, p less than 0.05, n = 7). Despite a 19 +/- 2 mm Hg rise in mean arterial pressure during handgrip exercise, CFR was unchanged from baseline (3.7 +/- 0.3 vs. 3.7 +/- 0.4, p = NS, n = 7) because rCBFV rose proportionally with hCBFV. When pulmonary capillary wedge pressure was increased from 9 +/- 1 to 16 +/- 1 mm Hg after volume expansion, CFR was significantly decreased (from 3.8 +/- 0.2 to 2.9 +/- 0.2, p less than 0.05, n = 9) because rCBFV was increased while hCBFV remained unchanged. Hence, serial CFR measurements in humans are highly reproducible in the absence of conditions known to affect resting or hyperemic coronary blood flow. Increases in heart rate or preload reduced CFR because rCBFV was increased while hCBFV was unchanged. In contrast, changes in mean arterial pressure did not alter CFR. Proper interpretation of CFR measurements should take into account the hemodynamic conditions at which they are obtained.