Interventricular Septum Thickness Predicts Future Systolic Hypertension in Young Healthy Pilots

15 Hypertens Res Vol.31 (2008) No.1 p.15-20 Original Article Interventricular Septum Thickness Predicts Future Systolic Hypertension in Young Healthy Pilots Chagai GROSSMAN1), Alon GROSSMAN2), Nira KOREN-MORAG3), Bella AZARIA2), Liav GOLDSTEIN2), and Ehud GROSSMAN1) Left ventricular hypertrophy (LVH) has been associated with hypertension, although debate exists as to whether LVH is caused by elevated blood pressure (BP) or is a risk factor for its development. The present study evaluates the association between left ventricular structure and the development of hypertension in a young healthy population. We followed young healthy Israeli Air Force aviators from initial echocardiography at the start of their military service to a mean of 7.5 ± 3.0 years. Data collection included annual BP measurements, height, weight, smoking habits, and lipid profile. We monitored 500 Air Force men with a mean age of 20.5 ± 3.3 (range, 17–40) years and baseline BP of 125 ± 13/74 ± 8 mmHg. Systolic BP during follow-up was associated with baseline systolic BP, interventricular septum (IVS) thickness, and ejection fraction, whereas diastolic BP was associated only with baseline diastolic BP and body mass index. The probability that the systolic BP during follow-up would be higher than the median was twice that in those with an IVS thickness greater than the median. In conclusion, IVS thickening was associated with long-term elevation of systolic BP. Therefore, it seems that IVS thickening is not merely a result of long-term BP elevation, but may predict the development of systolic hypertension. (Hypertens Res 2008; 31: 15–20) Key Words: echocardiography, normotensives, blood pressure Introduction Elevated blood pressure (BP) and obesity are risk factors that affect the structure and function of the left ventricle (1–3). Left ventricular hypertrophy (LVH) is an independent risk factor for cardiovascular disease (4, 5). The association between hypertension and left ventricular mass (LVM) has been clearly demonstrated in several studies (1, 6–9). Lauer et al. demonstrated that systolic BP, and to a lesser degree diastolic BP, are independent markers associated with increased LVM (9). Harpaz et al. evaluated a group of healthy subjects and showed that isolated interventricular septum (IVS) hypertrophy, even in the presence of a normal LVM, is associated with hypertension (8). Yet, it is a matter of debate whether BP is a risk factor for the development of LVH or merely a result of it. Several studies, mainly in children, have shown that increased LVM may precede hypertension (10–14). de Simone et al. followed a group of 132 subjects without hypertension for 4.7 years, during which 15 (11%) developed hypertension. Those who developed hypertension were found to have a greater LVM at baseline compared with their normotensive counterparts (11). These results were the basis for the hypothesis that LVH may in fact be a risk factor for the development of hypertension (10–14). Yet, data regarding the significance of LVH in the future development of hypertension in young, healthy subjects are scarce. The aim of this study was to evaluate the significance of LVM on the future development of hypertension in healthy normotensive subjects. From the 1)Department of Internal Medicine D and Hypertension Unit, The Chaim Sheba Medical Center, Tel Hashomer affiliated to the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel; 2)Israel Air Force Aeromedical Center, Tel Hashomer, Israel; 3)Division of Epidemiology, Sackler Medical Faculty, Tel Aviv University, Tel Aviv, Israel. Address for Reprints: Ehud Grossman, M.D., Internal Medicine D and Hypertension Unit, The Chaim Sheba Medical Center, Tel Hashomer 52621, Israel. E-mail: Received May 4, 2007; Accepted in revised form July 25, 2007. 16 Hypertens Res Vol. 31, No. 1 (2008) Table 1. Baseline Subjects’ Characteristics and Echocardiographic Values Variable Mean±SD Median Age (years) Baseline SBP (mmHg) Baseline DBP (mmHg) Baseline HR (beats/min) Height (cm) Baseline weight (kg) Baseline BMI (kg/m2) Total cholesterol (mg/dL) Triglycerides (mg/dL) LDL cholesterol (mg/dL) HDL cholesterol (mg/dL) End-diastolic dimension (cm) End-systolic dimension (cm) Interventricular septum thickness (cm) Posterior wall thickness (cm) Left atrium (cm) Ejection fraction (%) Left ventricular mass index (g/m2) Relative wall thickness 20.5±3.3 125±13 74±8 68±13 178±6 67±8 21.3±2.1 165±32 81±42 103±33 52±12 5.1±0.4 3.1±0.4 0.9±0.1 0.9±0.1 3.4±0.4 77±6 103.2±19.7 0.35±0.05 19 120 75 66 178 67 21.1 160 71 100 50 5.1 3.1 0.9 0.9 3.4 78 101.6 0.35 Range 17–40 90–180 50–120 34–160 157–193 48–97 16.6–30.6 95–279 19–337 22–226 25–116 4.0–6.5 2.3–4.4 0.6–1.2 0.6–1.2 2.0–4.5 59–84 54.3–182.9 0.27–0.53 SBP, systolic blood pressure; DBP, diastolic blood pressure; HR, heart rate; BMI, body mass index; LDL, low-density lipoprotein; HDL, high-density lipoprotein. Methods Subjects The study population consisted of 500 consecutively examined Israeli Air Force aviators. These healthy subjects underwent baseline evaluation and routine echocardiography prior to their enlistment and were then evaluated annually. The evaluation included BP, height, weight, and lipid profile. Subjects whose echocardiographs were inconclusive for technical reasons were excluded from the study, as were those with significant cardiac defects. Subjects who did not have at least 1 year of BP follow-up were also excluded. BP Measurements BP was measured at every visit twice in the sitting position following 2 min of rest using a sphygmomanometer, and the mean of the measurements was recorded. The BP was measured in the same arm every visit by skilled physicians who were unaware of the echocardiographic findings. Echocardiographic Evaluation Echocardiography was performed by an HP SONOS 2500 device (Hewlett-Packard, Palo Alto, USA) using a 2.5 MHz transducer. All examinations were performed using a similar technique. Two-dimensional M-mode guided measurements were performed according to the recommendations of the American Society of Echocardiography (15). Data collected included diastolic and systolic left ventricular (LV) diameter, posterior wall (PW) and interventricular septum (IVS) thickness, and left atrial (LA) diameter. The intra- and interobserver variations in these measurements were less than 10%. LA diameter was taken from the leading edge of the posterior aortic wall to the leading edge of the posterior left atrial wall as described by the American Society of Echocardiography (15). LVM was determined by the cube formula, using the Penn convention, as suggested by Devereux and Reichek (16). Left ventricular mass index (LVMI) was calculated by dividing the LVM by the body surface area (BSA). LVH was defined if either the PW or IVS thickness was greater than 11 mm as measured by M-mode echocardiography, or if the LVMI was at least 134 g/m2. Relative wall thickness (RWT) was calculated b (...truncated)