Myocardial Blood Flow Distribution in Concentric Left Ventricular Hypertrophy

Abstract

A B S T R A C T Regional myocardial blood flow during both control conditions and ischemia-induced vasodilatation was studied in eight chronically instrumented awake dogs. Seven of these animals had coarctationbanding ofthe ascending aorta performed at 6 wk of age, and the other dog had congenital subvalvular aortic stenosis. The mean left ventricular weight for the group was 157±7.6 g, and the left ventricular body weight ratio was 8.76+0.47 g/kg. None ofthe animals exhibited signs of congestive heart failure.During the control state, the mean left ventricular systolic pressure was 249+12 mm Hg and the left ventricular end-diastolic pressure was 11.5±0.5 mm Hg. The aortic diastolic pressure was 74±6 mm Hg. Mean left circumflex coronary artery blood flow was 71±6 cm3/min. In the animals with coarctation-banding, 52±6% of the flow occurred during systole. In the dog with congenital subvalvular aortic stenosis, 5% of the coronary flow was systolic. Mean transmural blood flow during resting conditions was 0.97±0.08 cm3/min per g, and the ratio of endocardial to epicardial flow (endo/epi) was 0.88±0.07. During reactive hyperemia, the mean transmural blood flow increased to 3.5±0.30 cm3/min per g; however, the endo/epi decreased to 0.52±0.06.These studies document a difference in transmural blood flow distribution between the normal and the hypertrophied left ventricle: during resting conditions, in the normal ventricle, the highest flow occurs in the endocardial layer, whereas in the hypertrophied ventricle, the highest flow is in the middle layers with the endocardial flow less than the epicardial flow.

Abnormal coronary vascular response to exercise in dogs with severe right ventricular hypertrophy.

“…Whereas RV hypertrophy is characterized by a marked increase in blood flow per gram of ventricle at rest (1), blood flow to the hypertrophied left ventricle has been shown to be either modestly reduced (16)(17)(18)(19), unchanged (20)(21)(22)(23)(24), or only slightly increased (25). Moreover, in contrast to the results ofthe present study, coronary vascular adjustments to exercise of the hypertrophied left ventricle appear to be largely normal (21,22,(26)(27)(28).…”

Bioenergetic abnormalities associated with severe left ventricular hypertrophy.

“…Mean myocardial blood flow tended to be increased in the hypertrophied hearts, but the fraction of flow delivered to the subendocardium was significantly decreased. These findings are similar to those previously reported ( 18,19). In response to adenosine infusion, mean myocardial blood flow increased 369% in normal hearts and 228% in hypertrophied hearts, indicating that the coronary vasodilator reserve was compromised in the hypertrophy group.…”

Impaired Endocardial Radial Strain in Hypertensive Patients with Electrocardiographic Strain Pattern on Twodimensional Speckle-Tracking Echocardiography

“…In addition to increased LVM, the strain pattern may be a marker of subendocardial myocardial ischemia, without coronary artery disease. Despite the increased diameter of coronary arteries in hypertrophied hearts, some predisposition to ischemia may exist, particularly in the subendocardial layers [18]. In the present study, endocardial radial strain was significantly correlated with the LVM index in hypertensive patients.…”