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Left ventricular myocardial blood flow in multivessel coronary artery disease
Insights
Resting myocardial blood flow (MBF) is reduced in multivessel coronary artery disease (CAD) due to lower hemodynamic factors. Peak left ventricular (LV) wall stress is the primary determinant of resting MBF in patients with and without CAD.
Area of Science:
- Cardiology
- Cardiovascular Physiology
- Medical Imaging
Background:
- Resting left ventricular (LV) myocardial blood flow (MBF) is crucial for oxygen supply.
- Multivessel coronary artery disease (CAD) can impair myocardial perfusion.
- Hemodynamic determinants significantly influence myocardial oxygen consumption.
Purpose of the Study:
- To investigate the relationship between resting LV MBF and hemodynamic factors in patients with multivessel CAD.
- To compare resting MBF and its determinants in patients with and without CAD.
- To identify key hemodynamic variables influencing resting MBF in CAD patients.
Main Methods:
- MBF measured using xenon-133 clearance with a multicrystal scintillation camera.
- Hemodynamic parameters including LV wall stress, velocity of circumferential fiber shortening (Vcf), and ejection fraction (EF) assessed via contrast left ventriculography.
- Multiple regression analysis used to determine the influence of hemodynamic variables on MBF.
Main Results:
- Patients with multivessel CAD exhibited significantly reduced mean LV MBF per unit mass compared to controls.
- Despite reduced MBF, patients with CAD showed no signs of ischemia at rest.
- Peak LV wall stress, mean Vcf, and heart rate explained 65% of MBF variation in CAD patients.
- After adjusting for these factors, LV MBF rates were not significantly different between groups.
- Peak LV wall stress showed the strongest correlation with resting LV MBF/beat in both groups.
Conclusions:
- Reduced resting LV MBF per unit mass in multivessel CAD is linked to lower hemodynamic determinants of myocardial oxygen consumption.
- Peak LV wall stress is the most critical hemodynamic factor influencing resting MBF in both healthy individuals and CAD patients.
- Hemodynamic optimization may be a target for improving myocardial perfusion in CAD.
Abstract:
The relationship between resting left ventricular (LV) myocardial blood flow (MBF) and hemodynamic determinants of myocardial oxygen consumption was investigated in 15 patients with multivessel coronary artery disease (CAD) and in 10 patients with normal coronary arteriograms. Mean LV MBF per unit mass of tissue was measured with a multicrystal scintillation camera from the regional clearance rates of xenon-133 injected into the left main coronary artery. Peak LV wall stress, mean velocity of circumferential fiber shortening (Vcf), rate of ejection during the first third of systole (1/3 SV), LV ejection fraction (EF), and the ratio of peak LV systolic pressure to LV end-systolic volume were measured by contrast left ventriculography. Mean LV MBF per unit mass was significantly reduced (48 +/- 11 vs 67 +/- 12 ml/100 g.min; p less than 0.01) in patients with multivessel CAD. However, none of the patients with CAD experienced chest pain or had electrocardiographic evidence of myocardial ischemia during the resting MBF measurements. Ejection phase indexes were lower in the patients with CAD: LVEF (56 +/- 10% vs 64 +/- 7%, p less than 0.05); 1/3 SV (35 +/- 3 vs 44 +/- 4%, p less than 0.05); and mean Vcf (1.05 +/- 0.30 vs 1.19 +/- 0.27 circ/sec, NS). LV wall thickness (9.8 +/- 1.9 vs 7.5 +/- 1.4 mm, p less than 0.01) and LV mass index (94 +/- 32 vs 64 +/- 17 g/m2, p less than 0.05) were significantly increased in the patients with CAD, accounting for the reduction in peak LV wall stress (276 +/- 73 vs 373 +/- 91 dyn-cm-2 x 10(-3), p less than 0.05) observed in these patients. Multiple regression analysis indicated that indexes of three of the major determinants of myocardial oxygen consumption explained 65% of the variation in MBF in patients with CAD: peak LV stress, mean Vcf and heart rate. After adjustment for these three indexes, the average LV MBF rates were not significantly different in the two patient groups (54.8 +/- 1.8 vs 57.6 +/- 2.3 ml/100 g.min). In both groups, resting LV MBF/beat correlated most highly with peak LV wall stress (r = 0.79). Thus, the reduction in LV MBF per unit mass observed in patients with multivessel CAD at rest is related to lower levels of hemodynamic variables that determine myocardial oxygen consumption. Peak LV wall stress is the most important hemodynamic variable determining the level of resting MBF in patients with and without CAD.