Evaluation of indices of left ventricular contractility and relaxation in evolving canine experimental heart failure

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Abstract
Objective: The aim was to evaluate changes in indices of left ventricular contractility and relaxation in relation to changes in loading conditions in dogs with rapid pacing induced heart failure. Methods: 14 conscious male mongrel dogs were paced at 250 beats·min−1 to severe heart failure, which occurred at 4.2(SDI.9) weeks. Six sham operated dogs served as controls. Right sided pressures were obtained by a thermodilution catheter. Left ventricular pressure and its derived variables were obtained by a high fidelity manometer tipped catheter. Rate corrected velocity of circumferential fibre shortening — end systolic wall stress relations were obtained by simultaneous haemodynamic and echocardiographic studies. Results: In the paced dogs, baseline right atrial pressure, 6.4(2.0) mm Hg, and pulmonary capillary wedge pressure, 7.1(2.5) mm Hg, increased to 13.3(3.1) mm Hg and 34.5(7.1) mm Hg respectively at severe heart failure (both p−1 at baseline to 975(321) mm Hg·s−1 at severe heart failure (pConclusions: In pacing induced heart failure, there is impairment of left ventricular contractility and relaxation. The major downward shift of the shortening-wall stress relation at one week suggests that left ventricular contractility is impaired early and may be the initiating mechanism of heart failure in this model.

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