Measurement of left ventricular hemodynamic parameters in closed-chest rats under control and various pathophysiologic conditions.

A prototype of a recently developed mikro-tip pressure transducer catheter (3 French) was inserted into the left ventricle of closed-chest rats via the right carotid artery. In thiobutabarbital-sodium anesthesia, heart rate (409 +/- 7 beats/min), left ventricular systolic pressure (LVSP: 142 +/- 4 mm Hg) and the maximal rate of rise of left ventricular pressure (LV dP/dtmax: 6073 +/- 187 mm Hg/sec, mean values +/- SEM, n = 19) were measured. The baroreceptor reflex was intact under these experimental conditions. In closed-chest guinea pigs, all functional parameters determined were lower (heart rate: 271 +/- 11 beats/min; LVSP: 94 +/- 6 mm Hg; LV dP/dtmax: 3248 +/- 295 mm Hg/sec, mean values +/- SEM, n = 9). To test the applicability of the new catheter tip manometer, cardiac hemodynamic parameters were determined in rats under various pathophysiologic conditions: Several periods of asphyxia were followed by progressive depressions in heart rate, LVSP and LV dP/dtmax, and acute as well as chronic stimulation with catecholamines (noradrenaline and isoproterenol) and with triiodothyronine was characterized by a pronounced positive inotropic and chronotropic effect. The technique described has many potential applications in cardiovascular studies on intact small laboratory animals.