Myocardial contractility of the isovolumetrically beating isolated rat heart

Abstract

Several indexes of myocardial contractility have been proposed to assess ventricular function in the isovolumetrically beating isolated heart. However, the conclusions reached on the basis of these indexes may be influenced by ventricular geometry rather than contractility itself. The objective of the present study was to assess the performance of widely used contractility indexes in the isovolumetrically beating isolated heart in two experimental models of hypertrophy, the spontaneously hypertensive rat (SHR) and infrarenal aortocava fistula. Compared to normotensive controls (N = 8), SHRs with concentric hypertrophy (N = 10) presented increased maximum rate of ventricular pressure rise (3875 ± 526 vs 2555 ± 359 mmHg/s, P < 0.05) and peak of isovolumetric pressure (187 ± 11 vs 152 ± 11 mmHg, P < 0.05), and decreased developed stress (123 ± 20 vs 152 ± 26 g/cm 2 , P < 0.05) and slope of stress-strain relationship (4.9 ± 0.42 vs 6.6 ± 0.77 g/cm 2 /%). Compared with controls (N = 11), rats with volume overload-induced eccentric hypertrophy (N = 16) presented increased developed stress (157 ± 38 vs 124 ± 22 g/cm 2 , P < 0.05) and slope of stress-strain relationship (9 ± 2 vs 7 ± 1 g/cm 2 /%, P < 0.05), and decreased maximum rate of ventricular pressure rise (2746 ± 382 vs 3319 ± 352 mmHg, P < 0.05) and peak of isovolumetric pressure (115 ± 14 vs 165 ± 13 mmHg/s, P < 0.05). The results suggested that indexes of myocardial contractility used in experimental studies may present opposite results in the same heart and may be influenced by ventricular geometry. We concluded that several indexes should be taken into account for proper evaluation of contractile state, in the isovolumetrically beating isolated heart.

Myocardial dysfunction with increased ventricular compliance in volume overload hypertrophy

“…Later, Sato et al [32] using a miniaturized conductance catheter showed that ESPVR is useful for evaluating myocardial contractility in rats. Other studies in rats submitted to the same experimental model have shown that this index is useful for detecting alterations in myocardial contractility associated with ventricular dilatation [11,33]. In our study, finding an inverse and significant association between ESPVR and dilatation in both the AVF and control group suggests that in isolated rat heart, this index is influenced by ventricular volume, independently of contractile state.…”

Combined Assessment of Functional and Metabolic Performance of Human Donor Hearts: Possible Application in Donation After Circulatory Death

“…Is isovolumic ventricular pressure measured by balloon a reliable surrogate for contractility and does it reflect pumping capacity? This technique for assessing contractility is well established in the physiological literature both in rats, 27 in dogs in our laboratory 28 and elsewhere 20 and in human donor hearts. 17,19 The intraventricular balloon system is easy to set up and this can be done during reperfusion.…”

“…Cardiac edema has been described previously during prolonged continuous ex vivo perfusion. 26,27 To set our lactate cutoff, we utilized a lactate of 10 mmol/L multiplied by a factor of 2 over the Hamed cutoff of 5 mmol/L to account for our blood perfusion priming volume of 600-800 mL being approximately half that of the priming volume of the OCS (1200 mL). 18 Although both our DP and lactate cutoffs were somewhat arbitrary, they allowed us to correlate measurements of function and lactate metabolism in individual hearts.…”

Hemodinâmica sistêmica e função ventricular esquerda de ratos hipertensos tornados diabéticos

“…Como demonstrado na literatura (14,15), todos os ventrículos dos animais hipertensos (BHR e SHR) apresentavam um aumento na relação entre o peso ventricular/volume inicial (V 0 ) quando comparados aos ratos normotensos (WST) (WST = 4,73 ± 0,70; BHR = 7,16 ± 2,33*; SHR = 7,96 ± 1,12* mg/ml, *p < 0,05 vs. WST). Quando se compararam esse parâmetro entre ratos normoglicêmicos e diabéticos, verificou-se uma redução desse índice nos ratos BHR + DM e SHR + DM (WST + DM = 5,64 ± 1,06; BHR + DM = .4,79 ± 1,07#, SHR + DM = 4,99 ± 0,95# mg/ml, #p < 0,05 vs. não diabético).…”