Background: Single photon emission computed tomography (SPECT) is a well-established method to evaluate patients with coronary artery disease (CAD). Myocardial contrast echocardiography (MCE) is an imaging technique that allows assessment of myocardial perfusion in a real-time setting. A short term prognostic study has shown that vasodilator MCE is superior to SPECT for the prediction of hard events. We sought to investigate the long term prognostic value of SPECT and MCE in the assessment of patients with known or suspected CAD.
Methods: We retrospectively followed-up patients with suspected or known CAD who were scheduled for coronary angiography and who also underwent MCE and SPECT at our institute, as part of multicentre studies performed between January 2002 and December 2009. Rest and vasodilator SPECT was performed after injection of 99mTc-sestamibi using the standard technique on separate days. We calculated the ratio of the number of abnormal segments (at rest and/or stress) to the total number of segments expressed as % for both MCE and SPECT in order to obtain a uniform assessment of the total ischaemic and scar burden (MCE and SPECT indexes). This population was followed up in 2016 to obtain a long term prognostic value of MCE and SPECT for hard events, all-cause mortality and non-fatal myocardial infarction (NFMI).
Results: Of the 277 patients who were analysed, 258 followed up and 19 were lost to follow up (6.8%). The mean age was 63.4 years and 186 (72.1%) patients were male, 82 (31.8%) had diabetes, 179 (69.4%) hypertension, 188 (72.9%) dyslipidaemia, 26 (10.1%) family history of CAD (FHCAD) and 64 (24.8%) were smokers. Prior CAD (angina, known acute myocardial infarction (AMI) or coronary revascularization) was present in 177 (68.6%) patients, left ventricular systolic dysfunction in 32 (12.4%), atrial fibrillation (AF) in 15 (5.8%) and chronic kidney disease in 16 (6.2%).
Over a mean follow-up period of 80.4±6.1 months (6.7±0.5 years), 18 patients suffered NFMI and 28 died (18% hard events, annualized hard events 2.7%).
Both MCE and SPECT indexes were significant predictors on univariate analysis (p=0.008 and p=0.035 respectively) for all-cause mortality, but MCE index was the only independent predictor for hard events (HR 3.827, 95% CI (1.1–13.2), p=0.034). Figure 1 demonstrates the Kaplan-Meier curve for the long-term prognostic value in all-cause mortality and NFMI of abnormal versus normal MCE. The annualized event rate for the abnormal MCE is 3.4% versus 1.6% for the normal MCE.
Conclusion: This is the first study to our knowledge that investigated the long-term prognostic value of SPECT and MCE in patients with suspected or known CAD. MCE was the only independent predictor of hard events. These results thus further support the routine use of MCE and not SPECT for the long-term prognostication of patients with known or suspected CAD.