Background
Stenosis severity ≥50% or ≥70% on coronary computed tomographic angiography (CCTA) is usually considered as significant, however functional significance of these values have not been well-defined. This study was designed to determine the stenosis degree on CCTA which cause ischemia on single-photon emission computed tomography (SPECT) in the patients with coronary artery disease (CAD).
Methods
Between November 2004 and November 2011, a total of 563 patients (72.3% male and 64.0±10.1 years) with CAD diagnosed on CCTA (maximal stenosis ≥50% in one of epicardial coronary arteries, >2mm in diameter) undergoing SPECT (within 3 months) were enrolled from two centers. The results of SPECT were classified as showing normal or abnormal (both reversible and fixed perfusion defects), and summed stress score (SSS) was calculated. In CCTA, the degree of maximal coronary diameter stenosis by visual assessment was graded by 3 groups: 50~69%, 70~89%, or ≥90%. Two hundred and ninety-one (51.7%), 156 (27.7%) and 116 (20.6%) patients had stenosis of 50~69%, 70~89%, and ≥90% on CCTA, respectively, and 230 (40.9%) patients had abnormal MPI on SPECT. With increasing severity of stenosis on CCTA from 50% to ≥90%, there was an increase in proportion of patients with abnormal MPI on SPECT (P <0.001). When stenosis severity on CCTA was 50~90%, prevalence of abnormal MPI on SPECT was ranged from 30.9% to 37.2%, whereas the proportion of the patients with abnormal MPI on SPECT increased dramatically up to 70.7% when luminal stenosis ≥90% on CCTA. With increasing grades of stenosis severity from 50% to ≥90% on CCTA, there was a gradual increase in the value of SSS (P <0.001). Luminal stenosis ≥90% on CTA was strongly associated with high SSS value (P <0.001), while patients with stenosis <90% on CCTA, there was no association between stenosis severity and SSS value (P >0.05).
Conclusion
Luminal stenosis severity on CCTA is not well correlated with the functional significance of myocardial ischemia on SPECT in patients with CAD. Only severe stenosis ≥90 % on CCTA caused ischemia on SPECT in this study. Coronary stenosis on CCTA should be interpreted with caution considering this discrepancy of stenosis with ischemia.
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