Borderline hypertension and obesity: two prehypertensive states with elevated cardiac output.

Systemic, renal and splanchnic hemodynamics, intravascular volume, circulating catecholamine levels and plasma renin activity were compared in 39 patients with borderline hypertension and 28 normotensive subjects, who were less than 5% (n = 42, lean patients) or more than 40% overweight (n = 25, obese patients). Lean borderline hypertensive patients had greater cardiac output (p less than 0.05), heart rate (p less than 0.01) and renal blood flow (p less than 0.05); cardiopulmonary redistribution of intravascular volume (p less than 0.05); and higher circulating norepinephrine levels (p less than 0.05). Obese normotensive subjects also showed an increased cardiac output (p less than 0.005), stroke volume (p less than 0.01), left ventricular stroke work (p less than 0.05), and renal blood flow (p less than 0.05) (but not respective indexes), but intravascular volume was expanded (p less than 0.05) without redistribution and circulating catecholamine levels were normal. Obese borderline hypertensive patients had hemodynamic characteristics similar to those of obese normotensive subjects except for an increased peripheral resistance (p less than 0.05). The data indicate that although both populations have an increased cardiac output, the lean borderline hypertensive patients have signs of enhanced adrenergic activity as evidenced by higher circulating catecholamine levels and heart rate with blood volume translocation to the cardiopulmonary circulation. In contrast, the obese subjects (whether normotensive or borderline hypertensive), who also have increased cardiac output, seem to have normal adrenergic activity and an expanded intravascular volume without cardiopulmonary redistribution.