Abstract
ObjectiveMyocardial ischemia is known to suppress fatty acid metabolism and favor glucose metabolism. However, changes in myocardial metabolism after coronary revascularization are not fully elucidated.MethodsThirty-eight patients with coronary artery disease were retrospectively enrolled. These patients had undergone stress perfusion single photon emission computed tomography (SPECT) and 123I-BMIPP SPECT in both the short-term (6.4 ± 4.7 months) and mid-term (29.9 ± 7.2 months) after isolated coronary artery bypass grafting. Tracer uptake was graded using a 17-segment, 5-point scoring model. Serial changes in SRS (summed rest score), SDS (summed difference score), the BMIPP score (total defect score of BMIPP), and the mismatch score (BMIPP score–SRS) were evaluated. In addition, persistent perfusion–metabolism mismatch (PM) was defined as mismatch score minus SDS of 3 or more during the mid-term postoperative period. The clinical parameters associated with PM were examined.ResultsFrom short- to mid-term postoperative period, the extent of infarcted myocardium (SRS) did not change significantly (7.8 ± 8.0 to 7.1 ± 7.0, P = 0.117). The extent of ischemic myocardium (SDS), the BMIPP score and the mismatch score, which reflects perfusion–metabolism mismatch, were significantly improved (2.0 ± 2.8 to 0.7 ± 1.0, P = 0.010; 12.2 ± 9.0 to 9.5 ± 7.9, P < 0.001; 4.4 ± 3.7 to 2.5 ± 2.6, P < 0.001; respectively). Remarkably, perfusion–metabolism mismatch persisted in 13 patients (34%) even in the mid-term postoperative period. eGFR and SYNTAX score were independent predictors of persistent perfusion–metabolic mismatch in multivariable analysis (OR = 0.951, 95% CI 0.898–0.985, P = 0.010 and OR = 1.126, 95% CI 1.011–1.254, P = 0.031, respectively). The mismatch score both in the short- and mid-term significantly correlated with SYNTAX score (r = 0.400 and r = 0.472, respectively).ConclusionsFatty acid metabolism disturbance improved from short- to mid-term postoperative period in patients with successful reperfusion by coronary artery bypass grafting. However, in patients with severe atherosclerosis, impaired fatty acid metabolism was sustained until the mid-term postoperative period, even though ischemia had resolved.
Highlights
In the follow-up of patients after coronary artery bypass grafting (CABG), evaluation of graft patency by coronary angiography and cardiac function by echocardiography is considered conventional management
LVEF left ventricular ejection fraction, LVEDVI left ventricular end-diastolic volume index, pre-op preoperation. This is the first study to evaluate the serial alteration of myocardial fatty acid metabolism in relation to myocardial perfusion in patients after CABG
The present results demonstrated that perfusion–metabolism mismatch improved from the short- to the mid-term after CABG in the whole patient population
Summary
In the follow-up of patients after coronary artery bypass grafting (CABG), evaluation of graft patency by coronary angiography and cardiac function by echocardiography is considered conventional management. Evaluation of myocardial metabolic function in relation to myocardial perfusion may be more important after revascularization for ischemic myocardium than graft angiography. Myocardial energy metabolism changes in response to stressors such as ischemia and pressure overload [1]. Elucidation of myocardial metabolism is important for understanding physiological and pathological processes in ischemic heart disease. Myocardial fatty acid metabolism can be visualized using single photon emission computed tomography (SPECT) with 123I-BMIPP (β-methyl-iodophenyl pentadecanoic acid). The combination of 123I-BMIPP SPECT and myocardial perfusion imaging (MPI) can, evaluate the relationship between myocardial fatty acid metabolism and perfusion. Discordant BMIPP uptake less than perfusion is often observed, which is called perfusion–metabolism mismatch. BMIPP imaging can demonstrate this metabolic imprint of a past ischemic episode, known as ‘ischemic memory’ [5]
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