SYNCHRONICITY OF VENTRICULAR CONTRACTION: OBSERVATIONS COMPARING HAeMODYNAMIC EFFECTS OF ATRIAL AND VENTRICULAR PACING

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Abstract
When the atrium and ventricle contract at or about the same time instead of sequentially, the ventricle is deprived of the atrial contribution to ventricular filling, mean atrial pressure rises in relation to left ventricular end-diastolic pressure, the end-diastolic pressure is lower, and the ventricle produces less external work. Further, when the ventricle is caused to contract as the result of direct electrical excitation instead of a normally propagated impulse, it will produce less external work from any given end-diastolic pressure. Hemodynamic evidence suggests that this is due, at least in part, to a less synchronous ventricular contraction.