The present invention relates to measuring ventricular function.
Ventricular function is often measured by researchers in an isolated heart, such as an isolated rat heart. The use of an isolated heart allows a broad spectrum of biochemical, physiological, morphological, and pharmacological indices to be measured without the presence of confounding effects of other organs, the systemic circulation, and peripheral complications. One method that researchers often use is the Langendorff method. In the Langendorff method, a balloon attached to a cannula is inserted into the heart and attached to a reservoir containing oxygenated perfusion fluid. The fluid is delivered down the aorta in a retrograde direction at either a constant flow rate or at a constant hydrostatic pressure. The aortic valves are forced shut and the perfusion fluid is directed into the coronary ostia, perfusing the entire ventricular mass of the heart and draining into the right atrium via the coronary sinus.
Although the size of an isolated heart changes under many conditions, such as with ischemia, reperfusion, or drug treatment, in the traditional Langendorff method, any changes in the size of the heart are not taken into account. The result is the incorporation of a systematic error into repeated measurements of ventricular function following interventions. The present invention takes the changing size of the heart into account in calculating ventricular function, yielding accurate measurements.
In one embodiment, the invention relates to a method of measuring ventricular function in an isolated, perfused heart using an intraventricular balloon connected to a plumbing circuit containing a fluid, the plumbing circuit including (a) a valve for selectively opening the plumbing circuit to (i) atmospheric pressure or (ii) a pressure control circuit of a pressure control apparatus or (b) a pressure control apparatus which can be selectively connected to the plumbing circuit, including the steps of establishing a base pressure by (1) opening the valve to atmospheric pressure or the pressure control circuit or (2) operating the pressure control apparatus, after equalization of the pressure within the intraventricular balloon with the base pressure, closing the valve or stopping operation of the pressure control apparatus, following the closing of the valve, measuring ventricular function as a function of a titrated infusion of fluid into the plumbing circuit and intraventricular balloon, performing an intervention, and repeating at least the first three steps.
In another embodiment, the invention relates to a system for measuring ventricular function in an isolated, perfused heart, including an intraventricular balloon adapted to be inserted into the isolated heart, a plumbing circuit containing a fluid, connected to the intraventricular balloon, a pressure transducer connected to the plumbing circuit, a pump, and a three-way valve connected to the plumbing circuit, the pump, and to the atmosphere, wherein opening the three-way valve to the atmosphere causes atmospheric pressure to be exerted by the intraventricular balloon on the isolated heart, and wherein subsequently opening the three-way valve to the pump causes the pressure exerted by the intraventricular balloon on the isolated heart to be equal to the sum of the atmospheric pressure and the pressure exerted by an infused volume of fluid.