Telemetry for Cardiovascular Monitoring in a Pharmacological Study

Abstract

Abstract-Radio-telemetry systems offer the ability to measure blood pressure and heart rate in experimental models of hypertension without the stress artifacts induced by some other methods. We therefore aimed to develop improved, nonparametric 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 control 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 were monitored for 4 weeks. Cardiac hypertrophy was assessed by the left ventricle plus septum weight to body weight ratio and vascular hypertrophy by flow-cytometry analysis of vascular smooth muscle cell polyploidy. Hemodynamic series were split into trend and cyclic components by the seasonal and trend decomposition procedure based on Loess and compared between groups by Loess regression modeling. Systolic and diastolic blood pressures were reduced systematically by losartan and perindopril (PϽ10 Ϫ10) but to a lesser extent by hydralazine plus hydrochlorothiazide (PϽ10 Ϫ8 ), and diurnal variation was reduced in the latter group (PϽ10 Ϫ6). L-NAME significantly reduced the hypotensive effect only of losartan. Vascular and cardiac hypertrophy were significantly attenuated with losartan or perindopril, but were unchanged with other treatments. The new analysis proposed here identifies differential effects on trends and cyclic variation and associations with regression of end-organ damage for losartan and perindopril compared with hydralazine plus hydrochlorothiazide. The method offers a powerful tool for detailed investigation of radio-telemetry data. Key Words: telemetry Ⅲ statistics Ⅲ hypertension, genetic Ⅲ hypertrophy, cardiac Ⅲ rats M onitoring of blood pressure and heart rate in experimental models of hypertension has played an important part in the study of cardiovascular physiology, pharmacology, and more recently in the genetics of hypertension. 1Ϫ3 A wide variety of techniques have been used to obtain these measurements. Anesthesia is the simplest method but it affects normal physiological regulation and thus measurements from conscious animals are preferred. 4 The most common techniques for monitoring conscious animals use tethers or restraining devices with measurements taken via indwelling exteriorized vascular catheters or blood pressure cuffs. 5 This use of restraints and tethers introduces a significant stress artifact with well-documented elevations of plasma catecholamines and cortisol. 6 In addition, the so called noninvasive tail-cuff measurements require both warming and restraint, thus producing several stressful stimuli.Radio-telemetry provides an alternative means of obtaining blood pressure and heart rate measurements from freely moving conscious animals. It provides the ability to collect data around the clock without ...

Two Genomic Regions of Chromosomes 1 and 18 Explain Most of the Stroke Susceptibility Under Salt Loading in Stroke-Prone Spontaneously Hypertensive Rat/Izm

“…Stress imposed on rats in the tail-cuff BP measurement might be a major cause of the discrepancy between the BP data measured by the tail-cuff method and by the telemetry. 13,14 In any case, these observations indicate the difficulty in analyzing QTLs for BP.…”

Recommendations for Blood Pressure Measurement in Humans and Experimental Animals

“…Other analytic methods for examining BP fluctuations in both the frequency and the time domain have also been developed and used. 37,57 The high-fidelity BP phenotyping that is achievable with BP radiotelemetry and with direct measurements through external catheter systems has also provided an invaluable tool for the investigation of genetic determinants of BP regulation. Identifying quantitative trait loci for BP using genetic strategies has been of intense interest in recent years.…”

False Claims of Blood Pressure–Independent Protection by Blockade of the Renin Angiotensin Aldosterone System?

“…Indeed, other investigators using continuous radiotelemetry measurements in SHRsp have found that the superior ability of losartan or perindopril to attenuate cardiac and vascular hypertrophy, in comparison with a hydralazine/ hydrochlorothiazide combination, may also be related to their superior ability to reduce blood pressure. 7 Thus, the findings of Griffin et al may be relevant to the protective effects of RAAS blockade on a variety of forms of target organ damage. These kinds of radiotelemetry studies not only raise questions about claims regarding BP-independent mechanisms that mediate the protective effects of RAAS blockade, but they also remind us of what should be obvious but is so often ignored in hypertension research: that to draw valid conclusions about the relationship between blood pressure and any other variable, it is important to obtain a thorough and accurate assessment of all phenotypes-including blood pressure!…”