A majority of patients (61 percent) evaluated for chest pain of uncertain cardiac cause have a coronary artery calcium (CAC) score of zero, which predicts both a normal SPECT result and an excellent short-term outcome, according to a single-center study published online Feb. 8 in the Annals of Emergency Medicine.

Faisal Nabi, MD, and colleagues from the Methodist DeBakey Heart and Vascular Center, the Methodist Hospital in Houston, undertook this prospective observational cohort study of stable patients presenting to the emergency department (ED) with chest pain of uncertain cardiac cause.

The researchers included participants with a normal initial troponin level, non-ischemic ECG, no history of coronary artery disease and had undergone SPECT and a CAC score within 24 hours of ED admission. They defined cardiac events as an acute coronary syndrome during the index hospitalization or in follow-up, assessed the CAC score results in relation to SPECT findings and cardiac events.

Nabi and colleagues enrolled 1,031 patients (mean age, 54 years), who had a median CAC score of zero (61 percent).
 
The frequency of an abnormal SPECT ranged from 0.8 percent (CACS of zero) to 17 percent (CAC score of more than 400). Cardiac events occurred in 32 patients (3.1 percent) during the index hospitalization (28 patients) or after hospital discharge (4 patients) (mean 7.4 months), according to the authors.

Only two events occurred in 625 patients with a CAC score of zero (0.3 percent).
 
Thus, the researchers found that two of 32 patients with a cardiac event had a CAC score of zero (6 percent). Both of these patients developed increased troponin levels during their index visit but had normal serial ECG and SPECT study results and no cardiac events at six-month follow up.

Based on their findings, the authors recommended that patients with a CAC score of zero can be “discharged home, without further cardiac testing.”