Prognostic impact of myocardial flow reserve assessed by cadmium-zinc-telluride single-photon emission computed tomography.

BACKGROUND

Myocardial flow reserve (MFR) reflects the ability of the coronary circulation to augment blood flow in response to increased demand, integrating both epicardial and microvascular function. Although its prognostic value has been demonstrated with invasive techniques and positron emission tomography (PET), evidence using cadmium-zinc-telluride (CZT) single-photon emission computed tomography (SPECT) remains limited. The aim of this study was to evaluate the prognostic impact of MFR assessed by CZT-SPECT in patients with and without obstructive coronary artery disease (CAD).

METHODS

We retrospectively analyzed 452 consecutive patients who underwent one-day rest/stress ˆ99mTc-sestamibi dynamic CZT-SPECT for MFR quantification. MFR was calculated as the ratio of stress to rest myocardial blood flow, with values <2 considered abnormal. Median follow-up was 792 days. Follow-up was censored at the last documented clinical visit for patients without events. Adverse cardiovascular events included angina, myocardial infarction, stroke, revascularization, hospitalization for angina or heart failure, and death. Major adverse cardiovascular events (MACE) were defined as death, myocardial infarction, revascularization, or stroke. Kaplan-Meier survival curves and Cox proportional hazard models were used, and incremental prognostic value was assessed with the C-index and likelihood ratio tests.

RESULTS

Among 452 patients (mean age: 63 ± 12 years, 54% male), 190 (42%) had MFR <2. During follow-up, 190 total events and 63 major events occurred. All deaths (n = 7) were observed in the reduced MFR group. MFR <2 was significantly associated with a higher risk of total events (hazard ratio [HR]: 3.8, 95% confidence interval [CI]: 2.5-5.7; P < 0.001) and major events (HR: 7.9, 95% CI: 3.5-17.6; P < 0.001). Incorporating MFR improved predictive performance (C-index from 0.63 to 0.77 for total events and from 0.76 to 0.84 for MACE; both P < 0.001).

CONCLUSIONS

MFR <2 assessed by CZT-SPECT significantly predicted adverse cardiovascular outcomes, including death, and provided incremental prognostic value beyond clinical risk factors and relative perfusion imaging. Routine incorporation of MFR assessment may improve risk stratification and guide personalized management of chronic coronary syndromes.