Telemetry for cardiovascular monitoring in a pharmacological study - New approaches to data analysis

Radio-telemetry systems offer the ability to measure blood pressure and hea rt rate in experimental models of hypertension without the stress artifacts induced by some other methods. We therefore aimed to develop improved, non parametric regression methods for radio-telemetry data and to use these to assess the effects of pharmacological interventions on cardiac and vascular hypertrophy in the stroke-prone spontaneously hypertensive rat. One contro l group and 5 groups treated either with losartan (alone or in combination with N-G-nitro-L-arginine methyl ester [ L-NAME]), perindopril (also alone or in combination with L-NAME), or hydralazine plus hydrochlorothiazide wer e monitored for 4 weeks. Cardiac hypertrophy was assessed by the left ventr icle plus septum weight to body weight ratio and vascular hypertrophy by fl ow-cytometry analysis of vascular smooth muscle cell polyploidy. Hemodynami c series were split into trend and cyclic components by the seasonal and tr end decomposition procedure based on Loess and compared between groups by L oess regression modeling. Systolic and diastolic blood pressures were reduc ed systematically by losartan and perindopril (P<10(-10)) but to a lesser e xtent by hydralazine plus hydrochlorothiazide (P<10(-8)), and diurnal varia tion was reduced in the latter group (P<10(-6)). L-NAME significantly reduc ed the hypotensive effect only of losartan. Vascular and cardiac hypertroph y were significantly attenuated with losartan or perindopril, but were unch anged with other treatments. The new analysis proposed here identifies diff erential effects on trends and cyclic variation and associations with regre ssion of end-organ damage for losartan and perindopril compared with hydral azine plus hydrochlorothiazide. The method offers a powerful tool for detai led investigation of radio-telemetry data.