Arterial compliance, assessed by the ratio of stroke volume to pulse pressure, and baroreceptor sensitivity (Oxford method), were determined in ten patients with essential hypertension, treated with placebo or indapamide (2.5 mg/day), in a cross-over, single blind study. After three months of therapy, mean arterial pressure was significantly reduced from 127 +/- 10 to 118 +/- 9 mmHg, (P less than 0.001), as was total peripheral vascular resistance (from 3017 +/- 561 to 2457 +/- 614 dyne/sec/cm-5/m2, P less than 0.001). Significant increases occurred in cardiac index (3.47 +/- 0.55 to 4.03 +/- 0.86 l/min/m2, P less than 0.01), baroreceptor sensitivity assessed with phenylephrine (from 11.69 +/- 7.9 to 15.0 +/- 9.1 msec/mmHg, P less than 0.01) or with nitroglycerine (from 4.77 +/- 1.6 to 7.11 +/- 2.7 msec/mmHg, P less than 0.01) and arterial compliance (from 1.27 +/- 0.42 to 1.55 +/- 0.57, P less than 0.01). A significant direct correlation was found between arterial compliance and baroreceptor sensitivity assessed during induced increase and reduction of BP, both during placebo (r = 0.88, P less than 0.001 and r = 0.77, P less than 0.01, respectively) and during active therapy (r = 0.94, P less than 0.001 and r = 0.92, P less than 0.001, respectively). These results support the conclusion that chronic treatment with indapamide enhances arterial compliances and reduces the heart load and blood vessel stress. The same effect could explain the enhancement of baroreceptor sensitivity promoted by the drug.
