Absence of Coronary Artery Calcium During Positron Emission Tomography Stress Testing in Patients Without Known Coronary Artery Disease Identifies Individuals With Very Low Risk of Cardiac Events.

BACKGROUND: Myocardial perfusion imaging, including positron emission tomography/computed tomography (PET/CT), is often used to assess for high-grade coronary artery disease (CAD) requiring revascularization. The use of coronary artery calcium (CAC) to predict risk of major adverse cardiovascular events in asymptomatic patients is accepted. However, little is known regarding the use of CAC in PET/CT patients without known CAD in identifying patients unlikely to need revascularization. Here, we determined whether the absence of CAC, using low-dose attenuation correction CT obtained during the PET/CT, identifies patients unlikely to undergo coronary revascularization within 90 days of a PET/CT. METHODS: Patients, without a history of CAD and no elevation in troponin, referred for PET/CT at Intermountain Medical Center were studied (n=5528). The presence of CAC was visually assessed using low-dose attenuation correction CT. The association between CAC and 90-day high-grade CAD and revascularization were assessed. Longer-term (up to 4 years) major adverse cardiovascular events, including all-cause death, myocardial infarction, and late revascularization (>90 days), were examined. RESULTS: There were 2510 (45.4%) patients in CAC-present group and 3018 (54.6%) patients in CAC-absent group. The CAC-absent group, compared with the CAC-present group, was less likely to undergo coronary angiography (3.4% versus 10.2%, P<0.0001), have high-grade CAD (0.5% versus 6.5%, P<0.0001), and receive revascularization (0.4% versus 5.8%, [adjusted odds ratio =0.09; 95% CI, 0.05-0.16]; P<0.0001). In patients with an ischemic burden >10%, the CAC-absent group was associated with reduced revascularization (P<0.0001). Longer-term major adverse cardiovascular events were lower in the CAC-absent (2.4%) compared with the CAC-present (6.9%) group (adjusted hazard ratio, 0.45 [95% CI, 0.34-0.60]; P<0.0001). CONCLUSIONS: The absence of CAC on low-dose attenuation correction CT identifies PET/CT patients unlikely to have high-grade CAD or require revascularization within 90 days and unlikely to experience longer-term major adverse cardiovascular events. The prognostic value of CAC, beyond ischemic burden, suggests its potential as a first-step screening tool in intermediate-risk patients to identify those who do not need coronary revascularization.

Implementation of a cardiac PET stress program: comparison of outcomes to the preceding SPECT era.

BACKGROUND: Cardiac positron emission testing (PET) is more accurate than single photon emission computed tomography (SPECT) at identifying coronary artery disease (CAD); however, the 2 modalities have not been thoroughly compared in a real-world setting. We conducted a retrospective analysis of 60-day catheterization outcomes and 1-year major adverse cardiovascular events (MACE) after the transition from a SPECT- to a PET-based myocardial perfusion imaging (MPI) program. METHODS: MPI patients at Intermountain Medical Center from January 2011-December 2012 (the SPECT era, n = 6,777) and January 2014-December 2015 (the PET era, n = 7,817) were studied. Outcomes studied were 60-day coronary angiography, high-grade obstructive CAD, left main/severe 3-vessel disease, revascularization, and 1-year MACE-revascularization (MACE-revasc; death, myocardial infarction [MI], or revascularization >60 days). RESULTS: Patients were 64 ± 13 years old; 54% were male and 90% were of European descent; and 57% represented a screening population (no prior MI, revascularization, or CAD). During the PET era, compared with the SPECT era, a higher percentage of patients underwent coronary angiography (13.2% vs. 9.7%, P < 0.0001), had high-grade obstructive CAD (10.5% vs. 6.9%, P < 0.0001), had left main or severe 3-vessel disease (3.0% vs. 2.3%, P = 0.012), and had coronary revascularization (56.7% vs. 47.1%, P = 0.0001). Similar catheterization outcomes were seen when restricted to the screening population. There was no difference in 1-year MACE-revasc (PET [5.8%] vs. SPECT [5.3%], P = 0.31). CONCLUSIONS: The PET-based MPI program resulted in improved identification of patients with high-grade obstructive CAD, as well as a larger percentage of revascularization, thus resulting in fewer patients undergoing coronary angiography without revascularization. FUNDING: This observational study was funded using internal departmental funds.