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 se nsitive to the method used to induce arrest. Accordingly, we sought to deve lop 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, consist ing 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 c c of 4 degrees C KCl (n = 6) or K120Na100 (n = 6) infused into the aortic r oot. The LVPVR was expressed as normalized volume (V-n) at standardized pre ssures, Myocardial water content (%MWC) was determined, (iii) Six hearts we re arrested with K120Na100 and LVPVRs observed over 1 h, (iv) Four hearts w ere instrumented with sonomicrometry crystals to compare in vivo and postmo rtem pressure diameter data, (v) The relation between body weight and dry h eart 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 sig nificantly 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 be came significantly smaller vs initial data 60 min after arrest with K120Na1 00 (P < 0.05, ANOVA). No differences between in vivo and postmortem mean no rmalized diameter were observed. The correlation coefficient for the relati on between body weight and dry heart weight was 0.80. Conclusions. K120Na100 at 4 degrees C reliably preserves LV diastolic prope rties in the rat heart for 30 min. Normalization of LV volume to body weigh t is justified. (C) 1998 Academic Press.