Cardiac Performance, Dr. D. Penney


Table 2.01. Similarities / Differences between Increased Preload and Afterload, Pressure-Volume changes, Incidence, Mechanism, and Consequences.

Comparison Increased Preload Increased Afterload
Similarities Increased tension on muscle fibers (related to pressure and volume) Increased tension on muscle fibers (related to pressure and volume
Pressure-volume changes Primarily an increase in volume (= volume load) Primarily an increase in pressure (= pressure load)
Incidence At the end of ventricular diastole During ventricular ejection
Mechanism Increased end-diastolic volume (heart failure, aortic insufficiency, etc.) Increased output resistance (constriction, etc.)
Consequence Increased product of mean ejection pressure and stroke volume; Increased stroke work Increased mean ejection pressure; Decreased stroke volume; Little change in stroke work




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