We assessed the relationship between stress-induced myocardial ischemia on myocardial perfusion single-photon emission computed tomography (MPS) and magnitude of coronary artery calcification (CAC) by X-ray tomography in patients undergoing both tests.
There has been little evaluation regarding the relationship between CAC and inducible ischemia or parameters that might modify this relationship.
A total of 1,195 patients without known coronary disease, 51% asymptomatic, underwent stress MPS and CAC tomography within 7.2 ± 44.8 days. The frequency of ischemia by MPS was compared to the magnitude of CAC abnormality.
Among 76 patients with ischemic MPS, the CAC scores were >0 in 95%, ≥100 in 88%, and ≥400 in 68%. Of 1,119 normal MPS patients, CAC scores were >0, ≥100, and ≥400 in 78%, 56%, and 31%, respectively. The frequency of ischemic MPS was <2% with CAC scores <100 and increased progressively with CAC ≥100 (p for trend <0.0001). Patients with symptoms with CAC scores ≥400 had increased likelihood of MPS ischemia versus those without symptoms (p = 0.025). Absolute rather than percentile CAC score was the most potent predictor of MPS ischemia by multivariable analysis. Importantly, 56% of patients with normal MPS had CAC scores ≥100.
Ischemic MPS is associated with a high likelihood of subclinical atherosclerosis by CAC, but is rarely seen for CAC scores <100. In most patients, low CAC scores appear to obviate the need for subsequent noninvasive testing. Normal MPS patients, however, frequently have extensive atherosclerosis by CAC criteria. These findings imply a potential role for applying CAC screening after MPS among patients manifesting normal MPS.