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      Telemetric left ventricular monitoring using wireless telemetry in the rabbit model

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          Abstract

          Background

          Heart failure is a critical condition that affects many people and often results from left ventricular dysfunction. Numerous studies investigating this condition have been performed using various model systems. To do so, investigators must be able to accurately measure myocardial performance in order to determine the degree of left ventricular function. In this model development study, we employ a wireless telemetry system purchased from Data Sciences International to continuously assess left ventricular function in the rabbit model.

          Findings

          We surgically implanted pressure-sensitive catheters fitted to wireless radio-transmitters into the left ventricle of Dutch-belted rabbits. Following recovery of the animals, we continuously recorded indices of cardiac contractility and ventricular relaxation at baseline for a given time period. The telemetry system allowed us to continuously record baseline left ventricular parameters for the entire recording period. During this time, the animals were unrestrained and fully conscious. The values we recorded are similar to those obtained using other reported methods.

          Conclusions

          The wireless telemetry system can continuously measure left ventricular pressure, cardiac contractility, and cardiac relaxation in the rabbit model. These results, which were obtained just as baseline levels, substantiate the need for further validation in this model system of left ventricular assessment.

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          Most cited references 29

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          A clinical study of left ventricular relaxation.

           Y Hirota (1980)
          Left ventricular (LV) relaxation was studied in patients with hypertrophic cardiomyopathy (HCM, n =18), congestive cardiomyopathy (CCM, n = 11), hypertensive heart disease (HHD, n = 8), coronary artery disease (CAD) without left ventricular (LV) asynergy (n = 9) and with LV asynergy (n =17), mitral stenosis (MS, n = 16), and mitral regurgitation (MR, n = 8). The time constant T and peak negative dP/dt were used as indexes of LV relaxation, and 18 normal subjects served as controls. The time constant T was higher in elderly patients among normal contros (r = 0.652, p < 0.01), which suggests that prolongation of relaxation is a phenomenon of aging. The normal value of the time constant T was 33 +/- 8 msec (mean +/- SD), and that of peak negative dp/dt was 1864 +/- 390 mm Hg/sec. The time constant T was significantly higher in HCM (64 +/- 20 msec), CCM (56 +/- 14 msec), CAD without asynergy (53 +/- 16 msec), CAD with asynergy (57 +/- 13 msec) and MS (47 +/- 12 msec). Peak negative dP/dt was significantly lower in HCM (998 +/- 303 mm Hg/sec), CCM (1060 +/- 334 mm Hg/sec), CAD with asynergy (1370 +/- 299 mm Hg/sec), MS (1367 +/- 313 mm Hg/sec) and MR (1139 +/- 305 mm Hg/sec). Although the genesis of LV relaxation abnormality is not clear from this investigation, it seems to have multiple causes. Relaxation abnormality seems to be one of the earliest manifestations of mechanical dysfunction of the human left ventricle.
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            Assessment of cardiac contractility. The relation between the rate of pressure rise and ventricular pressure during isovolumic systole.

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              Noninvasive assessment of the ventricular relaxation time constant (tau) in humans by Doppler echocardiography.

              The time constant of ventricular relaxation (tau) is a quantitative measure of diastolic performance requiring intraventricular pressure recording. This study validates in humans an equation relating tau to left ventricular pressure at peak -dP/dt (P0), pressure at mitral valve opening (PMV), and isovolumic relaxation time (IVRTinv). The clinically obtainable parameters peak systolic blood pressure (Ps), mean left atrial pressure (PLA), and Doppler-derived IVRT (IVRTDopp) are then substituted into this equation to obtain tau Dopp noninvasively. High-fidelity left atrial and left ventricular pressure recordings with simultaneous Doppler by transesophageal echocardiography were obtained from 11 patients during cardiac surgery. Direct curve fitting to the left ventricular pressure trace by Levenberg-Marquardt regression assuming a zero asymptote generated tau LM, the "gold standard" against which tau calc (IVRT inv/[ln(P0)-ln(PMV)]) and tau Dopp [IVRTDopp/[ln(Ps)-ln(PLA)]] were compared. For 123 cycles analyzed in 18 hemodynamic states, mean tau LM was 53.8 +/- 12.9 ms. tau calc (51.5 +/- 11 ms) correlated closely with this standard (r = .87, SEE = 5.5 ms). Noninvasive tau Dopp (43.8 +/- 11 ms) underestimated tau LM but exhibited close linear correlation (n = 88, r = .75, SEE = 7.5 ms). Substituting PLA = 10 mm Hg into the equation yielded tau 10 (48.7 +/- 15 ms), which also closely correlated with the standard (r = .62, SEE = 11.6 ms). The previously obtained analytical expression relating IVRT, invasive pressures, and tau is valid in humans. Furthermore, a more clinically obtainable, noninvasive method of obtaining tau also closely predicts this important measure of diastolic function.
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                Author and article information

                Journal
                BMC Res Notes
                BMC Research Notes
                BioMed Central
                1756-0500
                2011
                5 September 2011
                : 4
                : 320
                Affiliations
                [1 ]Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, USA
                [2 ]Animal Resources Center, University of Texas Medical Branch, Galveston, Texas, USA
                [3 ]Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, USA
                Article
                1756-0500-4-320
                10.1186/1756-0500-4-320
                3228511
                21892949
                Copyright ©2011 Lawrence et al; licensee BioMed Central Ltd.

                This is an open access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Categories
                Technical Note

                Medicine

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