E Bielen

The inheritance of left ventricular structure and function assessed by imaging and Doppler echocardiography

Abstract The heritability of left ventricular structure and function was studied in 53 pairs of monozygotic and dizygotic twins, aged 18 to 31 years, by means of M-mode and Doppler echocardiography. A significant fraction of the phenotypic variances of left ventricular wall thickness was explained by genetic variance. For the left ventricular internal dimension, however, no genetic effect was found after correction for body weight. After appropriate adjustment a genetic component of 32% was found for aortic peak flow velocity, 55% for stroke distance, and 47% for minute distance. The early and late diastolic peak flow velocities at the mitral valve showed a genetic component estimated at 43% and 26%, repectively. The inheritance of the late/early diastolic peak flow velocity ratio was estimated at 53%. In conclusion, these data suggest a significant genetic component for left ventricular structural features but not for cavity dimension. A significant influence of heredity was detected for left ventricular inflow and outflow characteristics.

Comparison of the effects of isradipine and lisinopril on left ventricular structure and function in essential hypertension.

The effects on cardiac structure and function of antihypertensive regimens with different effects on the renin-angiotensin system were compared. In a 1-year study, 32 patients with essential hypertension were randomized to treatment with either the converting enzyme inhibitor lisinopril or the calcium antagonist isradipine; hydrochlorothiazide could be added. Blood pressure (BP) decreased significantly (p less than 0.001) and similarly in the 2 treatment groups. Left ventricular (LV) mass was already significantly reduced after 16 weeks of treatment (p less than 0.001) and remained decreased thereafter, with no difference in the response to the 2 treatment regimens. The change in LV mass was related to the decrease in systolic BP for the total study group (p less than 0.001) and for each treatment group separately. During the 3-week run-out period on placebo, BP and LV mass increased again (p less than 0.01). Afterload decreased during active treatment (p less than 0.001), and fractional shortening of the LV internal diameter was significantly increased (p less than 0.01) to a similar extent in both groups. The ratio of peak mitral flow velocities during atrial contraction and early filling was reduced after 1 year of active treatment in the total study group (p less than 0.01); this change was similar in both groups. The data suggest that the regression of LV mass during antihypertensive therapy is mainly related to the decrease in systolic BP.

12. The inheritance of left ventricular structure and function, assessed by imaging and Doppler echocardiography

The heritability of left ventricular structure and function was studied in 53 pairs of monozygotic and dizygotic twins, aged 18 to 31 years, by means of M-mode and Doppler echocardiography. A significant fraction of the phenotypic variances of left ventricular wall thickness was explained by genetic variance. For the left ventricular internal dimension, however, no genetic effect was found after correction for body weight. After appropriate adjustment a genetic component of 32% was found for aortic peak flow velocity, 55% for stroke distance, and 47% for minute distance. The early and late diastolic peak flow velocities at the mitral valve showed a genetic component estimated at 43% and 26%, respectively. The inheritance of the late/early diastolic peak flow velocity ratio was estimated at 53%. In conclusion, these data suggest a significant genetic component for left ventricular structural features but not for cavity dimension. A significant influence of heredity was detected for left ventricular inflow and outflow characteristics.

Carotid baroreceptor control of heart rate and physical fitness

The carotid sinus baroreceptor reflex control of heart rate was studied in 12 endurance runners, 12 matched controls and in 24 cycling tourists using a variable negative pressure applied through a neck chamber. Baroreflex sensitivity was expressed as the slope of the linear relationship between the strength of the stimulus and the maximal lengthening of the RR interval on the electrocardiogram. Baroreflex sensitivity averaged 6.8 ± 1.1 (SEM) msec/mm Hg in controls, 10.3 ± 1.8 in runners and 7.3 ± 0.8 msec/mm Hg in cycling tourists. No significant differences were observed between the three groups. In single and multiple regression analysis, no significant relationship was found between carotid baroreflex sensitivity and age, blood pressure, resting heart rate, peak oxygen uptake and characteristics of training.