Long-term prognostic value of exercise 99mTc-MIBI SPET myocardial perfusion imaging in patients after percutaneous coronary intervention

The purpose of this study was to evaluate the long-term prognostic value of exercise technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) single-photon emission tomography (SPET) imaging in patients after percutaneous coronary intervention (PCI). Three hundred and eighteen consecutive post-PCI patients who underwent exercise and rest 99mTc-MIBI SPET myocardial perfusion imaging (MPI) were followed up for 38±27 months. Patients with early revascularisation (<3 months after MPI) were excluded. A semiquantitative visual analysis employing a 20-segment and four-point scoring system was used to define the summed stress score (SSS), summed rest score (SRS) and summed difference score (SDS). Death and non-fatal myocardial infarction (MI) were considered as hard events, and late revascularisation procedures (≥3 months after MPI) as soft events. Fifty-one patients (16.0%) suffered from cardiac events during follow-up, including 1 (0.3%) death, 13 (4.1%) non-fatal MIs, 9 (2.8%) coronary artery bypass grafting procedures and 28 (8.8%) PCIs. According to the SPET results, patients were classified into three groups: patients with normal MPI (SSS=0, n=153), patients with irreversible defects (SDS<3 and SRS>1, n=100) and patients with reversible defects (SDS≥3, n=65). The annual hard cardiac event rate in patients with reversible defects was 3.9%, which was significantly higher than that in patients with normal MPI (0.2%, χ2=7.71; P<0.01). The annual soft cardiac event rate in patients with reversible defects was 10.7%, which was significantly higher than that in patients with irreversible defects (2.5% χ2=17.69; P<0.001), and also significantly higher than that in patients with normal MPI (1.5%, χ2=33.89; P<0.001). In patients with normal and reversible defects, there was no significant difference in soft and hard cardiac event rates according to whether patients were symptomatic or asymptomatic (P>0.05). However, the annual soft event rate in patients with irreversible defects and symptoms was 5.0%, which was higher than that of 0.6% in asymptomatic patients (χ2=6.11, P<0.05). Multivariate Cox analysis showed that SSS was the best independent predictor for hard cardiac events (χ2=12.70; P<0.001) and SDS was the strongest independent predictor for soft cardiac events (χ2=11.72; P<0.001). Post-PCI patients who have normal exercise 99mTc-MIBI SPET MPI have a good long-term prognosis, while those with reversible defects are at a higher risk for future cardiac events, without correlation to the chest pain symptoms. However, symptomatic patients with irreversible defects have a higher risk for repeat revascularisation, but not for hard events, compared with asymptomatic patients. Exercise 99mTc-MIBI SPET MPI has important clinical value for risk stratification and management decision-making in post-PCI patients. (orig.)