A Ardehali1, J Segal, M D Cheitlin. 1. Cardiovascular Research Institute, University of California, San Francisco, USA.
Abstract
OBJECTIVES: This study sought to determine the impact of acute aortic regurgitation on coronary blood flow reserve and phasic epicardial coronary blood flow in closed-chest dogs. BACKGROUND: Hemodynamic changes in acute aortic regurgitation are known to precipitate myocardial ischemia. Coronary blood flow reserve has not been studied in closed-chest experimental preparations with acute aortic regurgitation. METHODS: Graded temporary acute aortic regurgitation was produced in 11 mongrel dogs. Phasic coronary blood flow velocities were measured using a Doppler guide wire. Coronary flow reserve was defined as the ratio of the time average of spectral peak velocity after administration of papaverine to that of the baseline state. RESULTS: Under control conditions (mean [+/- SEM] diastolic blood pressure 82.2 +/- 4.5 mm Hg), coronary flow reserve was 3.51 +/- 0.27 with predominantly diastolic epicardial coronary blood flow. With mild acute aortic regurgitation (diastolic blood pressure 61.8 +/- 3.0 mm Hg), coronary flow reserve decreased to 2.38 +/- 0.27, with an increase in phasic systolic epicardial coronary blood flow. At the onset of moderate acute aortic regurgitation (diastolic blood pressure 42.1 +/- 0.9 mm Hg), coronary flow reserve declined further to 1.46 +/- 0.12, and the phasic systolic epicardial coronary blood flow became more prominent. With severe aortic regurgitation (diastolic blood pressure 29.2 +/- 2.2 mm Hg), coronary flow reserve reached 1.20 +/- 0.05, and the phasic epicardial coronary blood flow pattern was found to be predominantly systolic with retrograde diastolic flow. The ratio of diastolic to systolic pressure-time indexes with severe aortic regurgitation suggested subendocardial underperfusion. CONCLUSIONS: This study demonstrates a marked decline in coronary blood flow reserve and documents a progressive change in the phasic epicardial blood flow to a predominantly systolic pattern with increasing degrees of acute aortic regurgitation.
OBJECTIVES: This study sought to determine the impact of acute aortic regurgitation on coronary blood flow reserve and phasic epicardial coronary blood flow in closed-chest dogs. BACKGROUND: Hemodynamic changes in acute aortic regurgitation are known to precipitate myocardial ischemia. Coronary blood flow reserve has not been studied in closed-chest experimental preparations with acute aortic regurgitation. METHODS: Graded temporary acute aortic regurgitation was produced in 11 mongrel dogs. Phasic coronary blood flow velocities were measured using a Doppler guide wire. Coronary flow reserve was defined as the ratio of the time average of spectral peak velocity after administration of papaverine to that of the baseline state. RESULTS: Under control conditions (mean [+/- SEM] diastolic blood pressure 82.2 +/- 4.5 mm Hg), coronary flow reserve was 3.51 +/- 0.27 with predominantly diastolic epicardial coronary blood flow. With mild acute aortic regurgitation (diastolic blood pressure 61.8 +/- 3.0 mm Hg), coronary flow reserve decreased to 2.38 +/- 0.27, with an increase in phasic systolic epicardial coronary blood flow. At the onset of moderate acute aortic regurgitation (diastolic blood pressure 42.1 +/- 0.9 mm Hg), coronary flow reserve declined further to 1.46 +/- 0.12, and the phasic systolic epicardial coronary blood flow became more prominent. With severe aortic regurgitation (diastolic blood pressure 29.2 +/- 2.2 mm Hg), coronary flow reserve reached 1.20 +/- 0.05, and the phasic epicardial coronary blood flow pattern was found to be predominantly systolic with retrograde diastolic flow. The ratio of diastolic to systolic pressure-time indexes with severe aortic regurgitation suggested subendocardial underperfusion. CONCLUSIONS: This study demonstrates a marked decline in coronary blood flow reserve and documents a progressive change in the phasic epicardial blood flow to a predominantly systolic pattern with increasing degrees of acute aortic regurgitation.