Dual assessment of coronary artery calcium and exercise ability enhances mortality prediction in stress single-photon emission computed tomography-myocardial perfusion imaging patients.

BACKGROUND

The application of hybrid stress single-photon emission computed tomography/computed tomography (SPECT/CT) imaging allows for the combined assessment of patients' exercise ability and coronary artery calcium (CAC) burden. The prognostic utility of this combined information among patients undergoing stress SPECT-myocardial perfusion imaging (MPI) remains incompletely understood.

METHODS

To simulate the prognostic information that can be provided by stress SPECT/CT, we assessed 2435 patients undergoing stress SPECT-MPI and CAC scanning within six months of each other. Patients were grouped into four groups of descending stress test performance: those exercising greater than or equal to 9 minutes, exercising less than 9 minutes, undergoing pharmacologic testing while performing a walk protocol, or pharmacologic testing without walking. Patients were followed for all-cause mortality (ACM) over a mean of 9.0 ± 6.4 years.

RESULTS

During follow-up, 291 patients (12.0%) died. There was a stepwise decrease in survival with poorer stress test performance and with increasing CAC scores. Mortality was consistently higher in patients with lower stress test performance among all CAC categories. Conversely, higher CAC scores were associated with increased mortality risk across all four stress test performance groups. Patients with CAC scores greater than or equal to 400 but exercising greater than or equal to 9 minutes had a mortality rate similar to patients with zero CAC scores who could not walk during pharmacologic stress testing (8.8 vs 8.0 per 1000 person-years, P = 0.898). A multivariable analysis identified stress test performance as the strongest adverse ACM predictor, followed by age and CAC scores.

CONCLUSIONS

The combined assessment of stress test performance and the magnitude of CAC abnormality provides highly synergistic prognostic information among patients undergoing stress SPECT-MPI.