Original ArticleIncremental value of combining 64-slice computed tomography angiography with stress nuclear myocardial perfusion imaging to improve noninvasive detection of coronary artery disease
Introduction
Since the recent advent of multidetector computed tomography angiography (CTA), image quality has greatly improved with the progression from 8- to 16- and now 64-slice capability, thus allowing for more precise evaluation of coronary artery stenosis.1 However, CTA is technically limited by suboptimal image quality when severe calcifications or motion artifacts are present. Even with the use of 64-slice CT scanners, the positive predictive value (PPV) of CTA is relatively low when evaluating patients with chest pain.2 This limited PPV is clinically important because it could result in the performance of unnecessary invasive coronary angiography (ICA). The latest multicenter 64-slice CT trial (CORE 64) indicated that multidetector CTA cannot be used as a replacement for ICA at present, given its negative predictive value (NPV) of 83% and PPV of 91% in symptomatic patients.3
Stress nuclear myocardial perfusion imaging (MPI) using single-photon emission tomography (SPECT) is an established method for assessment of the functional significance of coronary stenosis and delivers valuable information for risk stratification.4 Recently, the results of hybrid SPECT/CTA imaging have provided a marked increase in specificity and PPV to detect hemodynamically significant coronary lesions compared to those of 16-slice CTA alone.5 However, diagnostic performance of the 16-slice CT device used in that study was only moderate for detection of significant coronary artery stenosis, with 23% of coronary segments not evaluable.
We previously indicated that 64-slice CTA alone is not always sufficient to assess the functional significance of anatomic stenoses, especially stenoses of intermediate grade.6 When stenosis severity by CTA was <60%, ischemia was seldom observed, and when stenosis severity was ≥80%, ischemia was common. For intermediate stenosis severity values of 60-80%, the prevalence of reversible defects was difficult to determine, given CTA’s current spatial resolution.6 The aim of the present study was to compare the accuracy of combined use of 64-slice CTA and stress nuclear MPI for the noninvasive detection of coronary artery disease (CAD) with that of 64-slice CTA alone.
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Study Population
Initially, 142 symptomatic patients with suspected CAD who underwent both 64-slice CTA and stress nuclear MPI from January 2006 to August 2006 were enrolled in this study. Inclusion criteria included sinus heart rhythm; no previous myocardial infarction; no previous percutaneous coronary intervention or coronary bypass surgery; and no unstable angina. The subjects included in this study underwent ICA as the standard of reference within 1 month after the CTA and stress nuclear MPI tests. Of the
Patient Characteristics
Baseline clinical characteristics of the 130 patients enrolled in the study are summarized in Table 1. Before-test likelihood of CAD determined by the methods of Diamond and Forrester was low in 8 (6%), intermediate in 109 (84%), and high in 13 (10%) patients.
Invasive Coronary Angiography
Among the 130 patients, 124 (32%) of 390 arteries had a stenosis of more than 50% by ICA (single-vessel disease: 40 patients; 2-vessel disease: 26 patients; 3-vessel disease: 11 patients).
Stress Nuclear MPI Finding
Normal myocardial perfusion was observed in 49
Discussion
The major findings in the present study are as follows. First, our analysis was performed once for CTA alone after censoring nonevaluable arteries as positive and was then repeated with the stress nuclear MPI results substituted for nonevaluable CTA results. Stress nuclear MPI studies improved the specificity and PPV of CTA for the detection of coronary artery stenosis in all three vessels and could be used to complement the finding from coronary CTA. Second, the majority of nonevaluable
Conclusions
Combining 64-slice CTA and stress nuclear MPI provides improved diagnostic accuracy for the noninvasive detection of CAD and is especially useful in nonevaluable coronary vessels on CTA. This study underlies the value of a combined assessment of coronary anatomy and myocardial perfusion in patients with CAD and adds to an increasing body of evidence suggesting an added diagnostic value when combining both modalities.
Acknowledgments
The authors have indicated they have no financial conflicts of interest.
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