Does obesity influence early target organ damage in hypertensive patients?

Various prospective studies have found that lean hypertensive patients have greater cardiovascular morbidity and mortality than obese hypertensive subjects. It was therefore hypothesized that hypertension is more benign when associated with obesity. In the present study, we evaluated effects of obesity on early target organ damage in patients with essential hypertension.

In a total of 207 subjects, systemic and renal hemodynamics as well as left ventricular structure and function were assessed by measuring cardiac output (indocyanine green dye dilution), renal blood flow (clearance of 131I paraimmunohippuric acid), and mean arterial pressure (invasively) and by two-dimensionally guided M-mode echocardiographic findings. Systemic and renal vascular resistance, compliance of the large arteries evaluated by the stroke volume/pulse pressure index, and left ventricular mass served as parameters for early target organ damage. All individuals were categorized into four groups: lean and obese normotensive as well as lean and obese hypertensive subjects. In obese hypertensive patients, total peripheral resistance was significantly lower and stroke volume/pulse pressure index was higher than in the lean hypertensive group, almost reaching values of normotensive control subjects. No effect of obesity on the renal circulation was noted, whereas in hypertension, renal vascular resistance was elevated. The degree of left ventricular hypertrophy was more pronounced in the hypertensive groups than in their normotensive counterparts and progressively increased with obesity. Nevertheless, in obese hypertensive patients, left ventricular function, as measured by fractional fiber shortening and velocity of circumferential fiber shortening, was maintained despite the fact that the heart had been exposed to the double burden of an increased preload (obesity) and afterload (hypertension).

Obesity had a disparate effect on target organs in hypertension. At rest, obesity seemed to mitigate cardiovascular changes in the systemic vascular bed caused by hypertension. However, no such mitigation was observed in the renal vasculature, and left ventricular hypertrophy was even exacerbated by the presence of obesity. Our findings in part negate the concept that obesity is able to exert a protective effect on early target organ damage in hypertensive patients and, in particular, on the heart.