Simultaneous determination of ventricular function and systemic hemodynamics in the conscious rat

This study describes a method that utilizes a combination of the Millar transducer and Columbus thermistor in the conscious, spontaneously hypertensive rat and that permits simultaneous evaluation of the effects of cardiovascular agents on ventricular performance and systemic hemodynamics. Left ventricular end diastolic pressure (LVEDP, mmHg) and LV dp/dt (mmHg/sec) were measured with a Millar transducer inserted into the left ventricle of spontaneously hypertensive rats under ether anesthesia. Cardiac output (CO, ml/min) was measured by thermodilution (Columbus Instruments) with a thermocouple in the thoracic aorta via the femoral artery. Mean arterial pressure (MAP, mmHg) was measured via a catheter in the other femoral artery. All cardiovascular parameters measured were shown to attain a steady state within 3 hr after cessation of ether administration. Infusion of the beta adrenergic receptor agonist isoproterenol increased LV max dP/dt, heart rate (HR), and CO, and decreased arterial blood pressure and peripheral resistance. Administration of propranolol resulted in decreased HR, LV dP/dt and CO. The results show that this model was stable over an extended period of time and was responsive to standard inotropic agents. Thus, the combined use of the Millar transducer and the Columbus thermistor appears suitable for the assessment of acute pharmacological interventions on cardiovascular function in the conscious rat.