The information offered by multislice CT and myocardial perfusion imaging is sufficiently different that both tools are meaningful to the diagnosis of coronary artery disease—but evidence may predispose MSCT to becoming the first-line test, Joanne D. Schuijf of Leiden (the Netherlands) University Medical Center and colleagues reported.
They reported results from 114 patients (mean age 60 years) who underwent single-photon emission CT (SPECT) myocardial perfusion imaging (MPI) along with noninvasive coronary angiography with MSCT after presenting to either of two outpatient clinics with chest pain (J. Am. Coll. Cardiol. 2006;48:2508–14). Each patient underwent both tests within 30 days of the other.
MSCT showed that 29% of the patients had nonobstructive coronary artery disease (CAD), with 35% diagnosed with at least one significant lesion. The remaining 36% of patients were determined by MSCT not to have CAD. Notably, of the patients with abnormal MSCT findings, 55% (40 patients) had normal results on MPI—a dichotomy illustrating that “only half of the observed lesions on MSCT may be of hemodynamic significance. Even among patients with obstructive CAD on MSCT, 50% had normal MPI,” the investigators wrote.
Their study “is a first attempt to apply MSCT in patients with an intermediate likelihood of CAD,” they noted. The consistency of MSCT findings with those of invasive coronary angiography indicated that “the high accuracy of MSCT demonstrated previously in patients with a high likelihood of CAD also applies to patients with an intermediate likelihood of CAD.”
With the advent of MSCT and its greater diagnostic sensitivity over MPI, “a paradigm shift occurs in the definition of CAD, displacing the emphasis from inducible ischemia to atherosclerosis,” Ms. Schuijf and colleagues wrote. “Based on the discrepancy between MSCT and MPI, one can argue that MSCT could be used as the first-line test. A normal MSCT excludes CAD, and the patient can be reassured.”
In an accompanying editorial, Dr. Sharmila Dorbala of Brigham and Women's Hospital, Boston, and colleagues noted that although the consistency between the findings via MSCT and those via invasive coronary angiography was “excellent,” the study—like its predecessors in the literature—showed a diagnostic inconsistency between MSCT and MPI.
However, their ultimate assessment of the study's findings seemed to indicate a diagnostic advantage to MSCT. “Except in patients with high-risk scan features, combined testing with [MSCT and MPI] may be an effective strategy to both diagnose extent of CAD and guide management to the appropriate vessel,” they wrote.