Preload recruitable stroke work in the presence of intact cardiovascular reflexes in rats fed a diet high in unsaturated fats.

A decreased inotropic effect of myocardial beta receptor agonists in animals receiving diets high in unsaturated fats (UNSAT) has been demonstrated. The effect of an UNSAT diet on myocardial systolic performance under different loading conditions, in the presence of intact cardiovascular reflexes, has not been examined. We investigated the effect of an UNSAT diet on preload recruitable stroke work (SW) in the anaesthetised, open chest, ventilated rat. A control (CONTROL, 11% by energy), a high saturated fat (SAT, 37% by energy) and a high UNSAT (37% by energy) diet were fed to three groups of rats. At three months, systolic myocardial performance (stroke work: SW) at increasing left ventricular end diastolic pressures (LVEDP) was measured within a physiological preload range. There were no significant differences in either the slope or the intercept of the LVEDP/SW relation were found between the three diet groups. Systemic vascular resistance and heart rate decreased to the same extent in the three diet groups over the range of preloads examined. This occurred as a consequence of intact baroreceptor reflexes. Hence dietary modulation of unsaturated fats does not influence myocardial contraction over a wide range of physiological preloads in the presence of intact baroreceptor reflexes.