CLINICAL IMPORTANCE OF MEASURING CORONARY GRAFT FLOWS IN THE REVASCULARIZED HEART - ULTRASONIC OR ELECTROMAGNETIC

Background. In the past, routine coronary graft now measurement at the end of coronary artery bypass grafting (CABG) was not universally ado pted by cardiac surgeons due to the lack of reliable now measurement t echniques. The purpose of this study was to investigate the efficacy o f ultrasonic and electromagnetic techniques in coronary graft now meas urements and to determine the relationship, if any, between intraopera tive ultrasonic or electromagnetic coronary graft flows and postoperat ive early clinical outcome. Methods. We studied 66 consecutive patient s who underwent elective CABG using internal thoracic artery (ITA) and reversed saphenous vein graft (SVG) conduits. All patients were males with the mean age of 65+/-1 yrs (range=45 to 80 yrs). Coronary bypass graft flows (both ITA and SVG) were determined by the use of both ult rasonic and electromagnetic flowmeters. In addition, the flow waveform pattern was continuously recorded and analyzed with the ultrasonic te chnique. In this prospective non-randomized study, the following varia bles were considered in the forward stepwise multivariate regression a nalysis of the data: age, weight, body surface area, ejection fraction , perfusion and ischemia times, number of grafts, amount of allogenic banked blood, platelets, fresh frozen plasma transfusions, cardiac out put/index, ultrasonic (USF) and electromagnetic flows (EMF), length of intensive care unit (ICU) and hospital stays, and early (30-day) mort ality. Results. Based on their location, 226 grafts were divided into four groups: CI) ITA to left anterior descending (LAD) (n=66) 34+/-2.5 ml/min USF and 45+/-4.4 ml/min EMF; (II) SVG to circumflex (CX) (n=62 ) 33+/-2.4 m/min USF and 58+/-4.9 ml/min EMF; (III) SVG to diagonal (D IAG) (n=37); 30+/-3.5 ml/min USF and 50+/-6.0 ml/min EMF; (IV) SVG to right coronary artery (RCA) (n=61); 36+/-3.1 ml/min USF and 56+/-5.3 m l/min EMF. Electromagnetic flow measurements were higher than USP valu es in all locations (p<0.05). Difficulties in obtaining proper contact with the vessel wall and finding suitable size probes were major draw backs in measurement of ITA graft flow by the use of electromagnetic t echnique. All flow measurements were done within 10 minutes or less. T here was no demonstrable correlation between the length of stay (ICU a nd hospital), and coronary graft flows at the ITA to LAD, SVG to DIAG, or SVG to CX locations. However, ultrasonic coronary graft flows at t he SVG to RCA location had a significant inverse correlation with the length of ICU and hospital stays (r=-0.45, p<0.0005 for both). Early m ortality was unaffected by the intraoperative coronary graft flow valu es (p=NS). Conclusions. The ultrasonic flowmeter is well-suited for in traoperative assessment of arterial and venous coronary graft flows at the completion of CABG. There is a real potential for using intraoper ative graft flow values to predict early outcome after coronary bypass .