DEVELOPMENTAL CHANGES IN THE END-SYSTOLIC PRESSURE DIAMETER RELATIONSHIP (ESPDR) IN PUPPIES

Abstract

In order to evaluate the developmental changes in the ESPDR, an index of ventricular contractility independent of afterload and preload, we studied 13 normal puppies age 6 weeks to 6 months, weighing 1.7 to 21.0 kg (mean 6.8 kg). Arterial blood pressure and M-mode echocardiographic left ventricular dimensions were measured simultaneously during brief balloon occlusion of the inferior vena cava. The ESPDR using this technique was linear (r=0.95±0.02) over the range of end systolic pressure from 104.9±22.0 to 75.7±23.5 mmHg. The slope of the ESPDR (E_es) correlated significantly with the left ventricular diastolic diameter (LVD) prior to balloon occlusion, (r=-0.63 p 0.02) with E_es = -31.3 LVD + 154. The diameter intercept, D_o, did not correlate with LVD (r =0.33). We conclude that E_es does decrease with normal growth and the resultant increase in LVD. This apparent change in E_es with growth may be normalized by the LVD, suggesting that left ventricular pump function and contractility does not change in puppies over the ages studied. Furthermore, studies of the ESPDR in pathological states which alter the LVD should normalize E_es for LVD to more accurately assess left ventricular contractility.

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