Reduced left ventricular myocardial blood flow per unit mass in aortic stenosis.

Abstract

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...

Effects of exerimental right ventricular hypertrophy on myocardial blood flow in conscious dogs.

“…Inadequate perfusion of the hypertrophied ventricle could limit the extent to which the heart can compensate for the pressure overload, and thus may precipitate a decline in ventricular function. Results from recent studies examining the effects of left ventricular hypertrophy on myocardial blood flow appear to be consistent with this hypothesis, in that blood flow per gram of myocardial tissue has been found to be either decreased (1)(2)(3)(4), unchanged (5-9), or only slightly elevated (10). This concept is further supported by the observation of Rembert et al (10), that left ventricular hypertrophy is associated with a relative decline in preferential subendocardial perfusion (i.e., a decrease in the endocardial:epicardial perfusion ratio) at rest.…”

2015 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death

“…Takie czynniki etiologiczne, jak zwiększona masa mięśnia sercowego, rozstrzeń komory, naprężenie jej ścian i niedokrwienie podwsierdziowe bez obecności CAD, w połączeniu z przewlekłym uszkodzeniem mięśnia sercowego i jatrogennym włóknieniem po operacji, mogą być odpowiedzialne za zwiększoną częstość wystę-powania złożonych tachyarytmii komorowych, które mogą się wiązać z utrwalonym VT i SCD [606]. Złośliwy substrat arytmogenny może być dodatkowo wzmocniony przez częste współistnienie strukturalnej choroby serca, głównie CAD i HF.…”

Left ventricular systolic function in aortic stenosis

“…The decrease of (r/h) is the typical feature of concentric hypertrophy. As long as the product of (r/h) and LV systolic pressure remains constant, hypertrophy is appropriate' 11 . An increase of the product which represents an increase in wall stress signals inadequate LV hypertrophy.…”