Central hemodynamics and cardiac output control in essential hypertensive patients

Echocardiographic functions and blood pressure levels in children and young adults from a biracial population: the Bogalusa Heart Study

M-mode echocardiograms were obtained on 651 healthy subjects, 7-22 years of age, whose diastolic blood pressure levels remained in the same height-, race-, and sex-specific decile during two biannual examinations. Echocardiographic measures of heart size and dynamics were compared across the total blood pressure distribution. Left ventricular stroke volume, cardiac output and ejection fraction, minor axis shortening, velocity of circumferential fiber shortening, and peripheral vascular resistance were correlated with blood pressure levels. There were positive correlations (p less than .001) of cardiac output and stroke volume with both systolic and diastolic blood pressure levels. Left ventricular output and stroke volume were associated with measures of body size, especially height, weight, ponderal index, and body surface area (p less than .001). The left ventricular output and stroke volume increased with age and with systolic blood pressure quintiles in the four race-sex groups. With adjustment for systolic blood pressure and measures of body size, white males had greater cardiac output (1.25 l/minute for ages 18-22 years, p = .01) and stroke volume than black males. Black males had higher peripheral resistance (4.5 mm Hg/(l/minute), p = .01) than whites. These results suggest that different hemodynamic mechanisms operate in the early phase of hypertension in blacks vs. whites in this population.

Increased cardiac performance in mild essential hypertension. Left ventricular mechanics

To analyze cardiovascular dynamics in essential hypertension, 81 subjects with untreated mild essential hypertension (mean blood pressure, 112 +/- 14 mm Hg) and 87 normotensive subjects from the same working population were studied by echocardiography and simultaneous blood pressure determination. Hypertensive subjects had significantly higher pulse pressure, stroke volume index, cardiac index, left ventricular internal dimension, end-systolic pressure/volume ratio, end-systolic stress, left ventricular mass index, and relative wall thickness than normotensive subjects. Among both normotensive and hypertensive subjects, cardiac performance was closely dependent on afterload, as indicated by close inverse linear relationships between left ventricular fractional shortening and log end-systolic stress (r = -0.83 and -0.78 respectively; both, p less than 0.001). However, 19 of 81 hypertensive patients (23%) fell above the 95% confidence limits of this relationship in normotensive subjects (p less than 0.001 compared with that in normotensive subjects), with a bimodal distribution of fractional shortening as a percent of predicted in relation to end-systolic stress among patients with essential hypertension. This subgroup of hypertensive subjects, with increased resting cardiac performance independent of afterload, was similar in age to the remaining hypertensive subjects but had higher fractional shortening (41 +/- 5% vs 35 +/- 7%; p less than 0.001) and cardiac index (4.3 +/- 1.3 L/min/m2 vs 3.4 +/- 1.0 L/min/m2; p less than 0.005) and lower total peripheral resistance (1257 +/- 502 dyn sec cm-5 vs 1582 +/- 584 dyn sec cm-5 p less than 0.05) and left ventricular relative wall thickness (0.34 +/- 0.06 vs 0.42 +/- 0.10; p less than 0.005). Thus, analysis of cardiac mechanics detected a subset of patients with essential hypertension in whom increased cardiac function cannot be attributed either to relative youth or to supercompensatory left ventricular hypertrophy.