Coupling between the heart and arterial system in heart failure.

A number of experimental studies have demonstrated the optimal coupling between the ventricle and arterial load, under physiologic and pathologic circumstances, directed to produce maximal stroke work. We investigated matching of the ventricular properties, quantified by the slope of end-systolic pressure-volume relationship, with arterial load properties, expressed by the slope of end-systolic pressure-stroke volume relationship. In normal subjects, with ejection fraction of greater than or equal to 60%, ventricular elastance was nearly twice as large as arterial elastance. This condition affords maximal mechanical efficiency. In patients with moderate heart failure, with ejection fraction of 40-59%, ventricular elastance was almost equal to arterial elastance. This condition affords maximal stroke work from a given end-diastolic volume. In patients with severe heart failure, with ejection fraction of less than 40%, ventricular elastance was less than half of arterial elastance, which resulted in increased potential energy and decreased work efficiency. Ventriculoarterial coupling is normally set toward higher left ventricular work efficiency, whereas in patients with moderate cardiac dysfunction, ventricular and arterial properties are matched, in order to maximize stroke work at the expense of work efficiency. Neither the stroke work nor work efficiency is near maximum for patients with severe cardiac dysfunction.