Obesity and hypertension. Hemodynamic aspects.

Elevated arterial pressure in patients with obesity-hypertension is associated with an increased cardiac output and total peripheral resistance. The elevated output is related to expanded intravascular volume that increases cardiopulmonary volume, venous return, and left ventricular preload; the elevated pressure and total peripheral resistance increase afterload. This dual ventricular overload promotes a dimorphic, concentric, and eccentric hypertrophy in response to the volume and pressure overload. Increased myocardial oxygen demand results from the elevated tension in the left ventricular wall, reflecting its increased diameter and pressure, and provides physiologic rationale for the greater potential of coronary arterial insufficiency and cardiac failure. There are greater renal blood flow and lower renal vascular resistance in patients with obesity-hypertension at any level of arterial pressure. This may be offset by an increased renal filtration fraction that may favor protein deposition and glomerulosclerosis, and predisposition of obese patients for diabetes may aggravate this problem. With weight reduction, these hemodynamic derangements may be reversed: intravascular volume contracts, cardiac output decreases, and arterial pressure falls.