Left ventricular myocardial blood flow in multivessel coronary artery disease

The relationshp 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 rate 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 ( 3/4 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 <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 <0.05); 3/4 SV (35 ± 3 vs 44 ± 4%, p <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 <0.01) and LV mass index (94 ± 32 vs 64 ± 17 g/m², p <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 <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. Adter 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.