Experimental Instrumentation and Left Ventricular Pressure-strain Relationship

Pericardial pressure measurement with a balloon transducer requires opening and reapproximating the pericardium. If this instrumentation significantly compromises pericardial volume, the heart may be constrained, exaggerating the magnitude of pericardial pressure and thus altering the left ventricular end-diastolic pressure-volume relationship. In open-chest dogs, we studied the effects of opening the pericardium, inserting a pericardial balloon transducer and myocardial sonomicrometer crystals, and reapproximating the pericardium on the left ventricular end-diastolic pressure-strain relationship (LVEDPSR). After a thoracotomy, sonomicrometer crystals were inserted through small holes (less than 3 mm) in the pericardium to measure LV segment length. A micromanometer with a reference lumen was used to measure LV pressure. LVEDPSRs were recorded in the following situations: 1) before the pericardium was opened (but after the crystals were inserted); 2) after the pericardium was opened, the heart was instrumented (4 pairs of crystals and 1 balloon), and the pericardium was reapproximated with interrupted sutures; and 3) after the pericardium was removed. For each dog, a cubic regression equation was fitted to the data obtained before opening the pericardium, and the 95% confidence intervals for the individual data points were determined. In each case, the LVEDPSR obtained after instrumentation was similar to the LVEDPSR described before opening the pericardium. Furthermore, data obtained after instrumentation were uniformly located within the confidence intervals of the LVEDPSR obtained before opening the pericardium and instrumenting the heart.(ABSTRACT TRUNCATED AT 250 WORDS)