Insulin resistance is an important determinant of left ventricular mass in the obese

Multivariate Analysis of Left Ventricular Mass Determinants in Adults: Different Patterns in Men and Women

Echocardiographic left ventricular mass (LVM) estimates are strong predictors of subsequent mortality and cardiovascular events. It is known that blood pressure (BP), weight (WT), and age are significantly correlated with LVM. We hypothesized that stroke volume (SV) measured by Doppler echocardiography would also be correlated with LVM. Two hundred and thirteen patients referred for routine echocardiography had determination of LVM, cuff BP, and Doppler SV. Those with localized LV disease, valvular disease, or cor pulmonale were excluded. In both men and women, systolic BP (SBP) was more closely correlated with LVM than was diastolic blood pressure or mean arterial pressure, and SV was more closely correlated with LVM than cardiac output or cardiac index. Stepwise regression, followed by multiple regression showed that four variables (WT, SV, SBP, and AGE) explained 32.3% of the variability in LVM in men and 48.5% of the variability in LVM in women. WT and SV were significant determinants of LVM in both men and women. Age was also significant in men and SBP was also significant in women. For both men and women, SV was more significantly correlated with LVM than was SBP. The changes in LVM associated with 1 SD increments of SV and SBP, respectively, were 8 and 5 g for men and 13 and 11 g for women. We conclude that men and women have different patterns of variables influencing LVM. Doppler echocardiographic SV is a newly described determinant of LVM that has a greater correlation with LVM than does SBP. This study reemphasizes the importance of WT as the major determinant of LVM. (ECHOCARDIOGRAPHY, Volume 13, January 1996)

Serum insulin levels, 24-hour blood pressure profile, and left ventricular mass in nonobese hypertensive patients

In essential hypertensive patients, considered to be insulin-resistant, a blunted decline in nocturnal blood pressure is associated with increased adrenergic tone and left ventricular mass. Since insulin stimulates the sympathetic system, we tested whether insulin resistance and insulinemia influence left ventricular mass and the 24-hour blood pressure profile. We studied 29 nonobese hypertensive patients with office diastolic pressure between 95 and 110 mm Hg and normal oral glucose tolerance test after a 4-month washout period. They were then assigned to M-mode echocardiographic evaluation and 24-hour ambulatory blood pressure monitoring. The glucose and insulin responses to a 75-g oral glucose load were compared with those obtained in 16 weight-matched normotensive control subjects. During the oral glucose tolerance test the hypertensive patients compared with control subjects presented higher levels of glucose at 60 minutes (138.7 +/- 30.3 versus 108.7 +/- 35.7 mg/dL; P < .05) and 90 minutes (114.0 +/- 23.8 versus 94.8 +/- 31.1 mg/dL; P < .05) and insulin at 60 minutes (287.1 +/- 259.4 versus 142.1 +/- 83.9 pmol/L; P < .05). However, peak insulin levels after glucose load did not correlate with ambulatory blood pressure values or left ventricular mass index. Left ventricular mass index showed significant correlation with mean sleeping systolic pressure (rs = 56, P < .05) and diurnal systolic pressure (rs = .37, P < .05) but not with mean diurnal or sleeping diastolic pressures. In conclusion, our results indicate that in nonobese hypertensive patients, insulin resistance does not have any influence on the 24-hour blood pressure profile or on left ventricular mass index.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet size and left ventricular hypertrophy in hypertensive patients over 50 years of age

Both mean platelet volume (MPV) and left ventricular hypertrophy have been described as associated with increased risk for vascular events. Seventy-six hypertensive patients (37 M and 39 F) over 50 years of age were studied. They were divided into subgroups according to the presence of left ventricular hypertrophy (LVH = LV mass index > 125 g m-2, when LV mass was assessed by M-mode echocardiography according to Penn's Convention). MPV was 3% higher in hypertensive patients with LVH compared with those without LVH (P > 0.05) and it was associated with the occurrence of LVH (chi-square = 8.44, P = 0.042). MPV significantly correlated with left ventricular mass index (r = 0.298, P = 0.004) and interventricular septum thickness (r = 0.231, P = 0.022). Both correlations remained significant after adjustment for age, blood pressure and glycaemia. MPV seemed to be associated with increased left ventricular mass and interventricular septum thickness in middle-aged to elderly hypertensive patients.

Left ventricular hypertrophy is associated with a stronger impairment of non-oxidative glucose metabolism in hypertensive patients

Hypertensive patients with left ventricular hypertrophy (LVH) have a higher degree of hyperinsulinaemia than hypertensive patients without LVH. Obese patients with LVH have also been demonstrated to have a very low glucose disappearance rate after an intravenous glucose bolus. No studies have investigated the difference in insulin action and substrate oxidation in hypertensive patients with and without LVH. For this reason 36 subjects were enrolled for our study: (1) healthy control subjects (n = 10); (2) hypertensive patients without LVH (n = 12); and (3) hypertensive patients with LVH (n = 14). All subjects underwent an oral glucose tolerance test (OGTT, 75 g of glucose) and a euglycaemic hyperinsulinaemic glucose clamp (insulin infusion rate, 7.1 pmol (kg min)-1 for 120 min). In this latter test indirect calorimetry allowed substrate oxidation determination. Echocardiographic methods allowed LVH assessment. Hypertensive patients with LVH had the lowest insulin-mediated nonoxidative glucose metabolism compared to hypertensive patients without LVH (P < 0.01) and to healthy subjects (P < 0.001). In the whole group of hypertensive patients (n = 26), partial correlations showed left ventricular mass index (LVMI) associated with fasting plasma insulin levels (r = 0.44 P < 0.005), insulin-mediated whole body glucose disposal (r = -0.41 P < 0.01) and nonoxidative glucose metabolism (r = -0.33 P < 0.04) independently of age, body weight, systolic blood pressure and plasma catecholamines levels. In conclusion, our data provide evidence that LVH in hypertensive patients is associated with a worsening in nonoxidative glucose metabolism.

Association between left ventricular hypertrophy and erythrocyte sodium-lithium exchange in normotensive subjects with and without NIDDM

The determinants of left ventricular mass in normal control subjects and subjects with non-insulin-dependent diabetes (NIDDM) are ill-defined. We therefore recorded M-mode and pulsed Doppler echocardiograms and 24-h ambulatory blood pressure in 57 normotensive subjects, 34 with NIDDM and 23 matched non-diabetic control subjects. Measurements of erythrocyte sodium-lithium counter-transport, plasma angiotensin II, plasma and platelet catecholamines and fasting plasma insulin were also made. Six control subjects (26%) and 15 diabetic subjects (44%) had some degree of left ventricular hypertrophy. Subjects with left ventricular hypertrophy (n = 21) had an elevated mean rate of sodium-lithium countertransport (0.40 +/- 0.13 vs 0.31 +/- 0.09 mmol.l-1.h-1; p < 0.01), parallel differences being observed in both the diabetic and control groups. Twelve of the subjects with left ventricular hypertrophy (57%) had elevated rates of sodium-lithium counter-transport compared to only seven (19%) of those without (p < 0.05). There was no consistent difference between those with and without left ventricular hypertrophy in any other clinical or biochemical variable. Multivariate analysis, with the presence or absence of left ventricular hypertrophy as the dependent variable, demonstrated that the maximal rate of sodium-lithium countertransport was the only variable that independently contributed to left ventricular hypertrophy (partial r = 0.35; F1.55 = 7.74; p = 0.007). This study demonstrates for the first time an association between left ventricular hypertrophy and erythrocyte membrane cation transport that is independent of hypertension, is present in both diabetic and non-diabetic groups, and may represent a link between elevated rates of membrane sodium transport and cardiovascular risk.

Obesity, lipids, cardiovascular risk, and androgen excess

Several lines of evidence suggest that a subset of women may be at increased risk of cardiovascular disease because of unfavorable alterations in insulin action and/or production, accompanying altered apolipoprotein metabolism and altered androgenicity and/or estrogenicity. A number of cardiovascular disease risk factors, including central obesity, insulin resistance (with associated hyperinsulinemia), dyslipidemia, and/or diabetes mellitus, tend to cluster in these women. Another common ovarian morphology in women with hyperandrogenism is polycystic ovaries, which cluster with hirsutism, anovulation, infertility, gonadotropin secretion abnormalities, android fat distribution, and many important cardiovascular disease risk factors. Studies indicate that androgen excess may be a signal of increased risk for coronary artery disease, even in younger women. If androgenicity and insulin resistance are early warning signs of increasing risk of morbidity and mortality, these patients are prime candidates for preventive medicine. It is important that primary care providers begin to recognize these androgen disorders as a clue to the existence of a complex, lifelong pattern potentially placing women at risk for premature morbidity and mortality and initiate preventive treatment before irreversible thresholds are crossed.

Importance of obesity, race and age to the cardiac structural and functional effects of hypertension. The Department of Veterans Affairs Cooperative Study Group on Antihypertensive Agents

OBJECTIVES

The purpose of this study was to determine the effects of obesity and its interaction with age, race and the magnitude of blood pressure elevation in a large cohort of patients with mild to moderate hypertension and a high prevalence of left ventricular hypertrophy.

BACKGROUND

Obesity, race and age each have important effects on the incidence and severity of hypertension and may contribute to the effects of blood pressure elevation on the cardiac manifestations of hypertension.

METHODS

Left ventricular structure and function were assessed with two-dimensional targeted M-mode echocardiography in 692 men with mild to moderate hypertension (average blood pressure 153/100 mm Hg), and the data were compared in relation to obesity (determined from body mass index), age, race, blood pressure, physical activity, plasma renin activity, urinary sodium excretion, hematocrit, heart rate and serum lipids.

RESULTS

Left ventricular hypertrophy was common (63% with increased left ventricular mass, 22% with left ventricular hypertrophy on the electrocardiogram [ECG]). On multivariable regression analysis, body mass index was the strongest predictor of left ventricular mass and magnified the slope relation of blood pressure to left ventricular mass. Despite a greater prevalence of ECG left ventricular hypertrophy in blacks (31%) than in whites (10%), left ventricular mass and echocardiographic prevalence of left ventricular hypertrophy did not differ by race. However, septal, posterior left ventricular and relative wall thickness were greater in black than in white men.

CONCLUSIONS

Obesity is the strongest clinical predictor of left ventricular mass and left ventricular hypertrophy in men, even in those with mild to moderate hypertension of sufficient severity to be associated with a high prevalence of left ventricular hypertrophy. Moreover, independent effects of systolic blood pressure on left ventricular mass are amplified by obesity. Although race does not affect left ventricular mass or the prevalence of left ventricular hypertrophy, black race is associated with greater relative wall thickness, itself a predictor of unfavorable cardiovascular outcome.