The natural history of myocardium awaiting revascularisation in patients with impaired left ventricular function

Our aim was to follow changes in myocardial function and physiology in patients awaiting coronary artery bypass surgery (CABG) and relate changes to post-revascularisation functional response.

In 21 patients with CAD and LV dysfunction, myocardial glucose utilisation (MGU) and blood flow (MBF) were measured with positron emission tomography using F-18-fluorodeoxyglucose and oxygen-15-labelled water. Left ventricular function, MGU, and MBF were re-assessed after one year, immediately prior to CABG. At baseline, dysfunctional myocardium displayed a reduction in MGU, hyperaemic MBF, and coronary vasodilator reserve (CVR) compared to normally functioning muscle. In the year preceding CABG, the overall wall motion score index increased (2.09 +/- 0.65 vs. 2.3 +/- 0.7, p=0.0001) and the LV ejection fraction decreased (30.6 +/- 11.1% vs. 27.3 +/- 11.5%, p<0.001). LVEF fell in 14 patients (28.7 +/- 9.4 vs. 23.8, p<0.0001). Aggregate regional wall motion worsened in 15 patients. In contrast to myocardium displaying stable function at echocardiography, myocardium with evidence of deterioration showed a parallel decrease in hyperaemic MBF and CVR (1.57 +/- 0.67 vs. 1.19 +/- 0.7 ml/min/g, [p=0.004] and 1.9 +/- 0.75 vs. 1.33 +/- 0.6, [p=0.005], respectively). Such myocardium displayed attenuated recovery postoperatively (21/68 [31%] LV segments) versus 'waiting-time' stable myocardium (98/169 [58%], p=0.0002).

Delayed revascularisation in ischaemic left ventricular impairment results in declining function and a reduced likelihood of contractile improvement.