A Novel Arresting Solution for Study of Postmortem Pressure–Volume Curves of the Rat Left Ventricle

Objective. We have found diastolic properties of the rat heart extremely sensitive to the method used to induce arrest. Accordingly, we sought to develop a reliable solution for measuring the LV pressure-volume relationship (LVPVR) in the rat. Materials and methods. The study had five phases: (i) K-120-Na-100, consisting of KCl (120 mEq/L) in NaCl (100 mEq/L) diluted with distilled water was developed in preliminary experiments. (ii) ACI rats were arrested with 3 cc of 4 degrees C KCl (n = 6) or K120Na100 (n = 6) infused into the aortic root. The LVPVR was expressed as normalized volume (V-n) at standardized pressures, Myocardial water content (%MWC) was determined, (iii) Six hearts were arrested with K120Na100 and LVPVRs observed over 1 h, (iv) Four hearts were instrumented with sonomicrometry crystals to compare in vivo and postmortem pressure diameter data, (v) The relation between body weight and dry heart weight was determined in 48 animals, Results. In hearts arrested with KCl, mean V-n at pressures of 10, 15, and 20 mmHg (206 +/- 26, 306 +/- 21, and 336 +/- 25 mu l, respectively) was significantly reduced vs K120Na100 hearts (345 +/- 11, 407 +/- 12, and 472 +/- 18 mu l) (P < 0.05). Mean %MWC changed insignificantly. V-n at 20 mm Hg became significantly smaller vs initial data 60 min after arrest with K120Na100 (P < 0.05, ANOVA). No differences between in vivo and postmortem mean normalized diameter were observed. The correlation coefficient for the relation between body weight and dry heart weight was 0.80. Conclusions. K120Na100 at 4 degrees C reliably preserves LV diastolic properties in the rat heart for 30 min. Normalization of LV volume to body weight is justified. (C) 1998 Academic Press.