Effect of growth on variability of left ventricular mass: assessment of allometric signals in adults and children and their capacity to predict cardiovascular risk.

OBJECTIVES: We sought to determine whether growth influences the relation between left ventricular mass and body size and whether use of different body size indexes affects the ability of ventricular mass to predict complications of hypertension. BACKGROUND: Allometric (or growth) signals between left ventricular mass and height have recently been reported to improve previous approaches for normalization of ventricular mass for body size. METHODS: Residuals of left ventricular mass-height2.7 relations were analyzed in a learning series of 611 normotensive, normal-weight subjects 4 months to 70 years old and, separately, in 383 children (< 17 years old) and 228 adults. Ten-year cardiovascular morbidity in a test series of 253 hypertensive adults was compared with groups with normal or high baseline left ventricular mass normalized for body weight, height, body surface area and allometric powers of height. RESULTS: The dispersion of residuals of ventricular mass versus height2.7 increased with increasing height or age in children but not in adults, suggesting that the effect of other variables on ventricular growth increases during body growth and stabilizes in adulthood. Therefore, we derived separate allometric signals for adults (predicted ventricular mass = 45.4 x height2.13, r = 0.48) and children (32.3 x height2.3, r = 0.85) (both p < 0.0001). Patients with left ventricular hypertrophy had 3.3 times higher cardiac risk with elevated left ventricular mass/height2.7 (p < 0.001), 2.6 to 2.7 times higher risk with left ventricular mass indexed for height, height2.13 and body surface area (all p < 0.01) and 1.7 times the risk with ventricular mass/weight (p > 0.1). CONCLUSIONS: These results show the following: 1) Variability of left ventricular mass in relation to height increases during human growth; 2) allometric signals of left ventricular mass versus height are lower in adults and children than those obtained across the entire age spectrum; 3) height-based indexes of left ventricular mass at least maintain and may enhance prediction of cardiac risk by hypertensive left ventricular hypertrophy; and 4) the allometric signal derived across the entire spectrum of age appears to be more useful for prediction of cardiovascular risk than that computed in adults.

Assessment of left ventricular function by the midwall fractional shortening/end-systolic stress relation in human hypertension.

OBJECTIVES: This study examined left ventricular performance in relatively unselected hypertensive patients by use of physiologically appropriate midwall shortening/end-systolic stress relations. BACKGROUND: Supranormal left ventricular function has been reported in hypertensive patients, possibly due to an artifact of mismatching endocardial rather than midwall fractional shortening to mean left ventricular end-systolic stress. METHODS: Samples of 474 hypertensive patients (150 women, 324 men) and 140 normal subjects (68 women, 72 men) were drawn from a large urban employed population. The inverse relations (p < 0.0001) of both echocardiographic endocardial and midwall fractional shortening to end-systolic stress in normal subjects were used to calculate the ratios of observed to predicted endocardial and midwall fractional shortening in hypertensive patients. Midwall shortening was calculated from an elliptic model, taking into account the epicardial migration of the midwall during systole. RESULTS: Use of midwall fractional shortening in hypertensive patients reduced the proportion of patients with function above the 95th percentile of normal from 22% to 4% (p < 0.0001) and fractional shortening as a percent of predicted from 107% (p < 0.001 vs. 100% in normotensive control subjects) to 95% (p < 0.0001; p < 0.001 vs. 101% in normotensive control subjects). Midwall shortening was below the 5th percentile of normal in 16% of hypertensive patients instead of 2% with endocardial shortening (p < 0.0001): They tended to be older than other hypertensive patients and had concentric left ventricular hypertrophy. Among hypertensive patients, those with concentric left ventricular hypertrophy or remodeling had reduced midwall shortening as a percent of predicted from end-systolic stress (p < 0.0001). CONCLUSIONS: Use of the physiologically more appropriate midwall shortening/end-systolic stress relation 1) markedly reduces the proportion of hypertensive subjects identified as having high endocardial left ventricular function; and 2) identifies a substantial subgroup of patients with reduced left ventricular function who have concentric geometry of the left ventricle, a pattern associated with high cardiovascular risk.

Assessment of the effects of alpha- and beta-blockade in hypertensive patients who smoke cigarettes.

A 24-week, crossover, comparison study was conducted to observe the effects of alpha-blockade with prazosin and beta-blockade with propranolol on blood pressure and plasma lipoprotein levels in 15 hypertensive cigarette smokers. Before treatment, mean sitting blood pressure was 140/100 mm Hg and rose to 147/105 mm Hg after the patients smoked two cigarettes. Treatment with prazosin and propranolol lowered sitting blood pressure to 127/89 mm Hg and 129/91 mm Hg, respectively (not significant), and did not alter the pressor response to smoking. The total cholesterol level at baseline was 207.3 +/- 11.0 mg/dl. This increased to 210.5 +/- 10.2 mg/dl with propranolol treatment and decreased to 201.0 +/- 11.1 mg/dl with prazosin treatment. The low-density lipoprotein cholesterol level was 132.5 +/- 8.1 mg/dl at baseline, 136.9 +/- 8.3 mg/dl with propranolol treatment, and 129.4 +/- 9.0 mg/dl with prazosin treatment (0.05 less than p less than 0.10 between-group comparison). The data indicated that whereas prazosin and propranolol are equally effective in controlling blood pressure in hypertensive cigarette smokers, effects on plasma lipoproteins also may need to be considered when selecting a first-step antihypertensive agent in this coronary-prone population.

Cost-effectiveness of echocardiography and electrocardiography for detection of left ventricular hypertrophy in patients with systemic hypertension.

Although echocardiography is more accurate than electrocardiography for detection of left ventricular hypertrophy, it is also more expensive, making it uncertain whether echocardiography is cost-effective for detection of this abnormality in hypertensive patients. Accordingly, the sensitivity of M-mode echocardiographic and electrocardiographic criteria for left ventricular hypertrophy was determined in necropsied patients with anatomic hypertrophy of mild (n = 26), moderate (n = 21) or severe (n = 46) degree, and the prevalence of each degree of hypertrophy was determined in 561 hypertensive adults drawn from clinical and employed population samples. The sensitivity of echocardiographic left ventricular mass index criteria was 57% in necropsied patients with mild hypertrophy and 98% in patients with moderate or severe hypertrophy. All electrocardiographic criteria exhibited lower sensitivity: 15 to 42% for mild, 10 to 38% for moderate, and 30 to 57% for severe hypertrophy. Cost estimates from three sources were $160 for M-mode echocardiography and $48 to $64 for 12-lead electrocardiography. In populations with a 12 to 40% prevalence of hypertrophy, echocardiography was calculated to cost less than electrocardiography per instance of hypertrophy detected ($390-$1013 vs $800-$1829), yielded better separation in predicted incidence of morbid events between hypertensive patients with or without hypertrophy (3.4-4.7 vs 1.5-2.1 per 100 patient-years as opposed to 3.0-4.4 vs 1.9-2.9 per 100 patient-years), and required smaller case and control samples for hypothetical research studies (n = 254-309 vs 397-3478).(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic assessment of cardiac anatomy and function in hypertensive subjects.

Cardiovascular complications are a major source of morbidity and mortality in hypertensive patients. To assess the prevalence of anatomic and functional abnormalities of the heart in such patients, we studied 234 asymptomatic subjects with mild-to-moderate systemic hypertension by echocardiography. After adjusting the echocardiographic values for age and body surface area, we found abnormally increased ventricular septal and/or posterobasal free-wall thickness in 61% of the hypertensive subjects. We found increased left atrial, aortic root, and left ventricular internal dimension (at end-diastole) in 5-7%, and decreased mitral valve closing velocity (E-F slope) and left ventricular ejection fraction were noted in six and 15% of the subjects, respectively. Four percent of the patients had disproportionate septal thickening (i.e., ventricular septal-to-left ventricular free-wall thickness ratio greater than or equal to 1.3). In contrast to the high prevalence of cardiac abnormalities detected by echocardiography, less than 10% of the hypertensive subjects had abnormal 12-lead ECGs or abnormal chest x-rays. These findings demonstrate a high prevalence of cardiac abnormalities in a population of asymptomatic hypertensive subjects. These abnormalities can be detected by echocardiography before they are otherwise apparent.