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SUMMARY Myocardial blood flow/unit mass (MBF) and the determinants of myocardial oxygen consumption were measured in seven control subjects (group I) and 15 patients (pts) with cardiomyopathy (CM), group II (group Ila-congestive CM: 10 pts; group Ilb-hypertrophic CM: 5 pts). In group I left ventricular (LV) MBF was 64±8 (SD) ml/lOg -min; it was significantly lower in Ila (45 ± 15 ml/lOOg. min, P < 0.01) and IIb (39±7 ml/100g min, P < 0.01). However, calculated total LV flow (LV mass X MBF) was increased in the two CM groups. In nine CM pts, LV MBF increased in response to atrial pacing from 41±7 to 63±13 ml/lOOg * min.PATIENTS WITH CARDIOMYOPATHY frequently complain of chest pain suggestive of ischemic heart disease despite the presence of widely patent coronary arteries.' In addition, these patients often manifest varying degrees of myocardial hypertrophy and impaired ventricular performance. The relationship between these abnormalities and myocardial perfusion is largely unknown. There have been only a few studies, each involving small numbers of patients, of the myocardial circulation in cardiomyopathies and these studies have yielded conflicting results.4The first purpose of this study was to measure average left ventricular as well as regional myocardial perfusion at rest in patients with cardiomyopathy and to compare the values obtained with those in a control group of patients with normal coronary arteriograms and normal ventricular performance. For the study, patients with cardiomyopathy were divided into two functional categories, congestive cardiomyopathy and hypertrophic cardiomyopathy, by criteria developed by Goodwin.8 In nine of the cardiomyopathy patients, myocardial blood flow was also measured during right atrial pacing in order to evaluate the circulatory response to an increase in myocardial oxygen consumption.The second purpose of this study was to investigate in man the relationship between myocardial blood flow and three of the major determinants of myocardial oxygen consumption: heart rate, myocardial contractility, and wall stress. '-12 For this purpose, heart rate, mean velocity of circumferential fiber shortening (MVcf), and peak left ventricular (LV) systolic wall stress were measured in the control sub- 484In group Ila, calculated peak wall stress was normal (4.39±0.77 dynes/cm' X 106) but mean velocity of circumferential fiber shortening (MVcf) was significantly reduced (0.53±0.18 vs 1.26±0.12 circum/sec, P < 0.01). In llb, MVcf was normal but peak stress was significantly reduced (2.80±0.75 vs 4.51±1.10 dynes/cm' X 106, P < 0.05). Multiple regression analysis based on all pts yielded, MBF = 16.9 MVcf + 9.30 Stress + 0.26 Heart Rate -26.4, (r = 0.79). The data indicate that MBF is reduced in CM patients and the regression analysis suggests that MBF in these 22 pts with normal coronary arteriograms was determined largely by heart rate, peak stress, and ventricular performance.jects and in the patients with congestive and hypertrophic cardiomyopathy. The aim of this part of the stu...

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SUMMARY Myocardial blood flow (MBF) per unit mass was measured in 10 patients (pts) with severe aortic stenosis (AS) and no significant aortic Insufficiency, normal ejection fractions, and normal coronary arteriograms, using xenon-133 and a multiple crystal scintillation camera. MBF per unit mass was reduced in AS (53 i 13 ml/lOOg -min) in comparison to a group of seven normal control patients (69 ± 12 ml/lOOg -min) (P < 0.05). When normalized for heart rate, MBF remained depressed in aortic stenosis (0.65 i 0.11 ml/ lOOg -beat). MBF/beat was strongly related to peak left ventricular wall stress in both groups (r-0.97 In a previous study from this laboratory mean left ventricular (LV) myocardial blood flow per unit mass of tissue was measured with xenon-133 and a multiple-crystal scintillation camera in subjects with normal coronary arteriograms and normal cardiac function and in patients with normal coronary arteriograms and left ventricular hypertrophy due to congestive or hypertrophic cardiomyopathy.7 Resting mean left ventricular blood flow was found to be significantly related to indices of three of the major determinants of myocardial oxygen consumption: heart rate, the mean velocity of circumferential fiber shortening, and peak LV wall stress.There is general agreement in published reports that hypertrophy normalizes peak LV wall stress in patients with aortic stenosis who are not in heart failure.8 -3 It is not known, however, whether myocardial contractility is normal or abnormal in patients with aortic stenosis because there is no reliable method for measuring contractility independent of load in the intact human left ventricle with aortic outflow obstruction. Experimental data from animals, however, have shown depressed contractility in hypertrophied myocardium due to sustained pressure overload.'4 -9The present study was designed to measure left ventricular myocardial blood flow per unit mass in a selected group of patients with aortic stenosis using xenon-133 and a scin- MBF/beat were normalized for peak stress using an analysis of covariance; the adjusted mean values were 0.62 ± 0.03 mllOOg -beat for the AS patients and 0.84 ± 0.03 ml/lOOg-beat for the control patients. There was no overlap between groups in adjusted MBF per beat. Values of MBF per beat and peak stress for a group of ten cardiomyopathy patients with depressed contractility were observed to fall close to the regression line for AS patients. The results suggest that variability in resting MBF in these AS patients is due primarily to differences in LV stress and that reduction in MBF per beat in this group may be due to reduced contractility.tillation camera. Patients were selected who had normal coronary arteriograms, severe isolated aortic obstructions, and normal ejection fractions in order to answer two questions. First, do differences in LV wall stress account for any observed variability in resting myocardial blood flow rates among the patients with aortic stenosis? Second, by comparing the relationship between LV stress and myo...