Application of noninvasive techniques for measuring cardiac output in hypertensive patients.

The hemodynamic hallmark of hypertension is increased systemic vascular resistance, although this variable is usually not determined in hypertensive patients because it has generally required invasive procedures to measure cardiac output. Reliable, totally noninvasive methods are now available that measure cardiac output accurately enough under a variety of conditions, including rest, exercise, and pharmacologic interventions. These methods include echocardiography, Doppler echocardiography, CO2 rebreathing, and impedance cardiography. Their serial application to large numbers of patients offers the opportunity to significantly broaden our understanding of the spectrum and course of hemodynamic alterations associated with hypertension. A more complete knowledge of underlying hemodynamics could improve our diagnostic and prognostic accuracy in hypertensive patients and enhance our understanding of the pathophysiology of hypertension and the mechanism of action of antihypertensive interventions.