END-SYSTOLIC PRESSURE-DIMENSION RELATIONSHIP OF IN-SITU MOUSE LEFT-VENTRICLE

The increasing popularity of genetically engineered mice in cardiovasc ular research has made it important to evaluate cardiac function in sm all animals. We have developed a system to enable simultaneous pressur e-dimension analysis of the mouse left ventricle. The chest was opened under anesthesia, and a 1.4F micromanometer catheter was inserted int o the left ventricle through the apex. A pair of sonomicrometry crysta ls were attached to the anterior and posterior walls using tissue adhe sive. Pressure and dimension were recorded simultaneously at baseline and after isoproterenol injection (1 mu g, intraperitoneally). The asc ending aorta was occluded transiently to estimate the end-systolic pre ssure-dimension relationship (ESPDR), which was parameterized subseque ntly by the quadratic equation: P-es=C(2)x(D-es-D-0)(2)+E(0)x(D-es-D-0 ), where P-es is end-systolic pressure, D-es is end-systolic dimension , D-0 is the dimension axis intercept, E-0 is the local slope at D-0, and C-2 is the curvilinearity coefficient. The maximum and minimum ext ernal dimensions at baseline were 5.82 +/- 0.50 (S.D.) mm and 5.49 +/- 0.46 mm with fractional shortening of 0.057 +/- 0.014 (n = 12). The E SPDR was significantly curvilinear and increased convexity after isopr oterenol injection (C-2, -444 +/- 281 to -1113 +/- 780 mmHg/mm(2), P<0 .05; E-0, 536 +/- 175 to 889 +/- 276 mmHg/mm, P<0.001), while the dime nsion axis intercept remained relatively constant (D-0, 5.39 +/- 0.46 to 5.37 +/- 0.52 mm). In conclusion, the combination of miniature piez o-electric crystals and a micromanometer enables continuous measuremen t of pressure and dimension of in situ mouse left ventricle. This tech nology may be useful in evaluating the cardiac phenotype of geneticall y engineered mice. (C) 1998 Academic Press Limited.