Circulating insulin and insulin growth factor-1 are independent determinants of left ventricular mass and geometry in essential hypertension.

BACKGROUND: It is unclear whether insulin and insulin-like growth factor-1 (IGF-1) are independent determinants of left ventricular (LV) mass in essential hypertension. METHODS AND RESULTS: We studied 101 never-treated nondiabetic subjects with essential hypertension. All had 24-hour noninvasive ambulatory blood pressure (ABP) monitoring and a 75-g oral glucose tolerance test. We determined fasting glucose, insulin, and IGF-1 and postload glucose and insulin 2 hours after glucose. Insulin resistance was estimated by the homeostasis model assessment (HOMA(IR)) formula. LV mass showed an association with body mass index (BMI) (r=0.47; P<0.01), postload insulin (r=0.54; P<0.01), HOMA(IR) (r=0.39; P<0.01), and IGF-1 (r=0. 43; P<0.01) and a weaker association with average 24-hour systolic and diastolic ABPs (r=0.29 and r=0.26; P<0.05) and basal insulin (r=0.31; P<0.05). Relative wall thickness was positively related to IGF-1 (r=0.39; P<0.01) but not to fasting or 2-hour postload insulin, HOMA(IR), and glucose. In a multiple regression analysis, the final LV mass model (R(2)=0.64) included IGF-1, postload insulin, average 24-hour systolic ABP, sex, and BMI. IGF-1 and postload insulin accounted for >40% of variability of LV mass. The final model (R(2)=0.36) for relative wall thickness included IGF-1 (16% total explained variability), average 24-hour systolic ABP, sex, BMI, and age but not insulin and HOMA(IR). CONCLUSIONS: These data indicate that insulin and IGF-1 are powerful independent determinants of LV mass and geometry in untreated subjects with essential hypertension and normal glucose tolerance.

Adverse prognostic value of a blunted circadian rhythm of heart rate in essential hypertension.

BACKGROUND: Previous studies revealed a direct association between resting heart rate and risk of mortality in essential hypertension. However, resting heart rate is a highly variable measure since it is affected by the alerting reaction to the visit. OBJECTIVE: To investigate whether the heart rate values recorded during the 24 h of ambulatory blood pressure monitoring are independent predictors of survival of uncomplicated subjects with essential hypertension. METHODS: We followed up 1942 initially untreated and uncomplicated subjects with essential hypertension (mean age 51.7 years, 52% men) for an average of 3.6 years (range 0-10 years). All subjects underwent baseline procedures including 24 h non-invasive blood pressure monitoring with simultaneous assessment of heart rate, one reading every 15 min for 24 h. MAIN OUTCOME MEASURES: All-cause mortality and cardiovascular morbidity. RESULTS: During follow-up there were 74 deaths from all causes (1.06 per 100 person-years) and 182 total (fatal plus non-fatal) cardiovascular morbid events (2.66 per 100 person-years). Clinic, average 24 h, daytime and night-time heart rates exhibited no association with total mortality. However, the subjects who subsequently died had had a blunted reduction of heart rate on going from day to night during the baseline examination. After adjustment for age (P < 0.001), diabetes (P < 0.001) and average 24 h systolic blood pressure (SBP, P= 0.002) in a Cox model, for each 10% less reduction in the heart rate from day to night the relative risk of mortality was 1.30 (95% confidence interval 1.02-1.65, P = 0.04). Rates of death were 0.38, 0.71, 0.94 and 2.0 per 100 person-years among subjects in the four quartiles of the distribution of the percentage reduction in heart rate from day to night The baseline day-night changes in the heart rate exhibited an inverse correlation to age and to clinic and ambulatory SBP and a direct association with the day-night changes in blood pressure. The degree of reduction of heart rate from day to night also had an independent inverse association with total cardiovascular morbidity after adjustment for age, diabetes and left ventricular hypertrophy, but this association did not remain significant when average 24 h SBP and the degree of day-night reduction in SBP were entered into the equation. CONCLUSIONS: A flattened diurnal rhythm of heart rate in uncomplicated subjects with essential hypertension is a marker of risk for subsequent all-cause mortality and this association persists after adjustment for several risk factors. For assessing these subjects, a limited and uniformly distributed period of ambulatory heart rate recording during the 24 h is clinically valuable.

Value of a simple echocardiographic linear predictor of left ventricular mass in systemic hypertension.

The need for calculations limits the clinical use of left ventricular (LV) mass. Because LV mass is strictly dependent on wall thickness for every given value of LV external dimension, we tested the clinical value of the sum of LV external dimension plus ventricular septal thickness plus posterior wall thickness as predictors of standard LV mass. We studied 295 healthy normotensive subjects and 1,686 subjects with systemic hypertension, followed up for 1 to 9 years. In the normotensive group, the predictor of LV mass showed a very close association with standard LV mass according to an allometric model (LV mass [g] = 0.230 x LV mass predictor [cm]3.01), with 99.7% of LV mass variability explained by the model. Also, in the hypertensive group, the LV mass predictor showed a very close allometric relation to standard LV mass (R2 = 0.998). During follow-up there were 154 cardiovascular morbid events and 50 deaths from all causes. The risk of cardiovascular morbid events and that of death increased to a similar extent with LV mass normalized by body surface area, height or height2.7, as well as with the LV mass predictor. The risk estimates for cardiovascular morbidity and all-cause mortality provided by models including either LV mass predictor or LV mass uncorrected or corrected by height, body surface area, or height2.7 did not show any statistical differences between the different models. In conclusion, the sum of LV external dimension plus ventricular septum thickness plus posterior wall thickness, easily measurable from the M-mode echocardiographic tracing, very closely predicts standard LV mass in adult hypertensive subjects. The prognostic value of this measure does not differ from that of standard LV mass.