Coronary grafts flow and cardiac pacing modalities: how to improve perioperative myocardial perfusion.
OBJECTIVE: Aim of this study was to investigate modifications of coronary grafts flow during different pacing modalities after CABG. MATERIALS AND METHODS: Two separate prospective studies were conducted in patients undergoing CABG and requiring intraoperative epicardial pacing. In a first study (22 patients) coronary grafts flows were measured during dual chamber pacing (DDD) and during ventricular pacing (VVI). In a second study (10 patients) flows were measured during DDD pacing at different atrio-ventricular (A-V) delay periods. A-V delay was adjusted in 25 ms increments from 25 to 250 ms and flow measurements were performed for each A-V delay increment. A transit time flowmeter was used for the measurements. RESULTS: An average of 3.4 grafts/patient were performed. In the first study, average coronary graft flow was 47.4+/-20.8 ml/min during DDD pacing and 41.8+/-18.2 ml/min during VVI pacing (P = 0.0004). Furthermore average systolic pressure was 94.3+/-10.1 mmHg during DDD pacing and 89.6+/-12.2 mmHg during VVV pacing (P = 0.0007). No significant differences in diastolic pressure were recorded during the two different pacing modalities. In the second study, maximal flows were achieved during DDD pacing with an A-V delay of 175 ms (54+/-9.6 ml/min) and minimal flows were detected at 25 ms A-V delay (38.1+/-4.7 ml/min) (P=ns). No significant differences in systolic or diastolic blood pressure were noticed during the different A-V delays. CONCLUSION: Grafts flowmetry provides an extra tool to direct supportive measures such as cardiac pacing after CABG. DDD mode with A-V delay around 175 ms. should be preferred to allow for maximal myocardial perfusion via the grafts.