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Effects of coronary blood flow on left ventricular function in essential hypertensive patients
1Second Department of Internal Medicine, Ehime University School of Medicine, Japan.
Insights
Essential hypertension leads to reduced myocardial blood flow per gram of heart tissue, contributing to left ventricular dysfunction. This decrease in unit coronary blood flow is linked to impaired systolic and diastolic functions in hypertensive patients.
Area of Science:
- Cardiology
- Hypertension Research
- Myocardial Physiology
Background:
- Left ventricular hypertrophy (LVH) in hypertension is associated with cardiac dysfunction.
- The precise mechanisms linking LVH and dysfunction require further elucidation.
Purpose of the Study:
- To investigate the relationship between coronary blood flow (CBF) and left ventricular dysfunction in essential hypertension.
- To determine if reduced myocardial blood supply contributes to impaired cardiac function in hypertensive individuals.
Main Methods:
- Measured coronary blood flow (CBF) and left ventricular mass (LVM) in 62 hypertensive patients and 22 controls using thallium-201 and echocardiography.
- Calculated CBF per 100 g of myocardium (unit CBF) and assessed systolic (fractional shortening) and diastolic (isovolumic relaxation time) functions.
- Employed multiple regression analyses to identify predictors of cardiac function.
Main Results:
- Hypertensive patients had higher total CBF but significantly lower unit CBF compared to controls.
- Unit CBF was the strongest predictor of both systolic and diastolic left ventricular function.
- A positive correlation existed between midwall fractional shortening and unit CBF, while isovolumic relaxation time showed a negative correlation with unit CBF.
Conclusions:
- Decreased myocardial blood flow per unit mass (unit CBF) in hypertension may reflect myocardial ischemia.
- This reduction in unit CBF is closely associated with left ventricular systolic and diastolic dysfunction in essential hypertension.
Abstract:
To elucidate the mechanism of left ventricular dysfunction associated with left ventricular hypertrophy in hypertension, coronary blood flow (CBF) and left ventricular mass (LVM) were measured in 62 patients with essential hypertension (mean age, 54 +/- 13 years) and 22 normotensive control subjects (mean age, 57 +/- 13 years). According to the indicator fractionation principle, CBF/cardiac output (CO), estimated on the basis of the ratio of myocardial uptake/total injected dose of thallium-201 (% cardiac uptake), was measured. CBF and CBF per 100 g of myocardium (unit CBF) were calculated according to the following formulas: CBF=% cardiac uptake x CO, and unit CBF=(CBF/LVM) x 100, where CO and LVM are echocardiographically determined. Midwall fractional shortening (FS) and isovolumic relaxation time (IRT) were calculated as the indices of systolic and diastolic functions. CBF was greater in hypertensives than in controls (218.2 +/- 74.0 vs. 187.4 +/- 40.4 ml/min, p < 0.05), though unit CBF was smaller in hypertensives than in controls (99.1 +/- 22.0 vs. 141.2 +/- 31.6 ml/min/100 g, p < 0.0001). Multiple regression analyses showed that unit CBF was the most potent predictor of both midwall FS and IRT. A positive correlation was found between midwall FS and unit CBF (r=0.669, p < 0.0001), and a negative correlation between IRT and unit CBF (r=-0.579, p < 0.0001). In conclusion, myocardial ischemia reflected by the decrease in unit CBF may be closely related to left ventricular dysfunction in patients with essential hypertension.