Systolic time interval changes after aorto-coronary bypass

Pre-operative assessment of PEP/LVET ratio was as reliable as invasively measured ejection fraction in separating patients with normal ventricular performance from those with abnormal indices. Our study demonstrates significant impairment of ventricular performance following aorto-coronary bypass procedures. The duration of this dysfunction is between two and five days following operation and is maximal in the first 48 hours. Meaningful interpretation of systolic time interval changes requires measurement of pre-load and after-load. Changes in these variables account for at least some of the increase in PEP/LVET ratio noted in our study. On the basis of a shortened QS2I these patients are thought to exhibit increased adrenergic activity for the entire period of their hospitalization.