Diagnostic performance of static single-scan stress perfusion cardiac computed tomography in detecting hemodynamically significant coronary artery stenosis: a comparison with combined invasive coronary angiography and cardiovascular magnetic resonance-myocardial perfusion imaging

Abstract

Background

Non-invasive anatomical and physiological evaluations of coronary artery disease (CAD) may be obtained with static single-scan stress perfusion cardiac computed tomography (SSPCT).

Purpose

To determine the diagnostic performance of static SSPCT for identifying hemodynamically significant CAD.

Material and Methods

This prospective study included 29 patients with suspected or known CAD who underwent static SSPCT, cardiovascular magnetic resonance myocardial perfusion imaging (CMR-MPI), and invasive coronary angiography (ICA). CT was performed as follows: (i) coronary calcium scan; (ii) static SSPCT for both coronary artery (coronary CT angiography [CCTA]) and myocardial perfusion (perfusion CT [PCT]) during adenosine infusion; (iii) late-phase scan. The diagnostic performance of CCTA alone, PCT alone, and SSPCT for the detection of a hemodynamically significant CAD (a perfusion defect in a vascular territory subtended by a coronary vessel with ≥ 50% stenosis) was compared with that of combined ICA/CMR-MPI representing the standard of reference.

Results

Twenty-three (79%) patients and 47 (54%) vascular territories manifested ischemia-causing coronary stenoses by combined ICA/CMR-MPI. The per-vessel sensitivity, specificity, positive and negative predictive values, and area under the receiver operating characteristic curve (AUC) of the SSPCT were 92%, 88%, 90%, 90%, and 0.90, respectively, compared to those of the combined ICA/CMR-MPI. These values for the CCTA alone were 96%, 63%, 75%, 93%, and 0.79, respectively; and the values for the PCT alone were 94%, 83%, 86%, 92%, and 0.88, respectively. The AUC of SSPCT was significantly (P = 0.013) higher than that of the CCTA alone.

Conclusion

Static SSPCT may facilitate detection of hemodynamically significant CAD.

Keywords

Multidetector computed tomography magnetic resonance imaging coronary angiography coronary artery disease myocardial perfusion imaging

Introduction

Coronary computed tomography angiography (CCTA) is a non-invasive method for diagnosing high-grade coronary stenosis. However, prior multicenter studies have highlighted a non-negligible false-positive rate for CCTA-identified coronary stenosis (1 –4). Furthermore, less than half of high-grade stenoses identified by CCTA are physiologically causal of myocardial ischemia, and concerns have arisen that the use of CCTA-identified coronary artery disease (CAD) may precipitate high rates of unnecessary invasive coronary angiography (ICA) (5,6). To address these limitations, pharmacologic stress perfusion CT (PCT) has emerged as an additional CT method for diagnosing myocardial ischemia, and salutary diagnostic performance is observed when compared to single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI), fractional flow reserve (FFR), a combination of ICA and SPECT-MPI, and a combination of ICA and cardiovascular magnetic resonance (CMR)-MPI (7 –14). In clinical practice, combined CCTA and stress PCT for evaluating the anatomic and physiologic significance of coronary stenoses requires double the amount of iodinated contrast medium and radiation exposure as well as examination time of at least 30 min for a single-day protocol.

Due to the availability of CT scanners with a high temporal resolution, information on coronary artery anatomy and stress myocardial perfusion using static single-scan stress perfusion CT (SSPCT) can be obtained simultaneously (15). The static SSPCT protocol is different from the stress/rest PCT protocol because of the absence of rest PCT, which enables identification of reversibility or persistence of a perfusion defect (PD) from stress to rest, and has the potential to reduce the radiation dose and scan time by obviating the need for rest PCT. However, the diagnostic performance of the static SSPCT for identifying a hemodynamically significant CAD is lacking in comparison with an anatomic–physiologic reference standard. Therefore, the aim of this prospective study was to determine the performance of static SSPCT for diagnosing hemodynamically significant coronary stenoses that cause ischemia when compared to combined ICA/CMR-MPI as a reference standard.

Material and Methods

Study population and design

This prospective study enrolled a total of 41 consecutive patients with suspected or known CAD who were aged ≥ 40 years and referred for ICA from October 2010 to October 2012. We excluded patients with deteriorated renal function (serum creatinine > 1.5 mg/dL and estimated glomerular filtration rate < 60 mL/min/1.73 m²), high-degree atrioventricular block, decompensated congestive heart failure, known allergy to iodinated contrast agents, unwillingness or inability to provide informed consent, previous coronary artery bypass graft surgery, unstable clinical status, or contraindications for adenosine. Among 41 patients eligible for the study, 12 were excluded: refusal to participate in the study because of dissatisfaction with non-diagnostic image quality of SSPCT (n = 5); and refusal to perform CMR-MPI (n = 4) or ICA (n = 3) because of time commitment or medical costs. Finally, 29 patients were included. Fig. 1 summarizes the patient flow chart within this study. Enrolled patients underwent three studies within 30 days without intervening changes in clinical status or coronary revascularization. The study protocol was approved by the institutional ethics committee and all patients provided written informed consent before enrolment.

Fig. 1.

Flow diagram of patients eligible for recruitment and reasons for exclusion. The 29 patients completed the entire protocol with no adverse events. CAD, coronary artery disease; SSPCT, single-scan stress perfusion computed tomography; ICA, invasive coronary angiography; CMR-MPI, cardiovascular magnetic resonance myocardial perfusion imaging

Image acquisition

Cardiac CT protocol: Beta-blockers or nitroglycerine was not used to avoid any impact on myocardial perfusion. All images were performed using a dual-source CT scanner (Somatom Definition, Siemens Medical Solutions, Forchheim, Germany). A static SSPCT was performed during the infusion of adenosine by using a retrospective electrocardiographically gated acquisition. CT protocol is described in Fig. 2. A triphasic contrast injection protocol was used for the static SSPCT. A late-phase CT was performed without the additional use of a contrast medium. The specific scanning parameters and contrast medium administration of CT are described in the supplementary material. The total radiation dose was calculated using a conversion coefficient (κ = 0.014 mSv∙mGy^–1∙cm^–1) (16).

Fig. 2.

CT protocol. After the coronary calcium scan with a non-enhanced, prospective ECG-triggering protocol, a static SSPCT with a contrast-enhanced, retrospective ECG-gating protocol with an ECG-based tube current modulation was acquired 4 min after the initiation of the adenosine infusion. Five minutes after the SSPCT, a late-phase CT with a prospective ECG-triggering protocol was performed without the additional use of an iodinated contrast medium.

CMR-MPI protocol: CMR-MPI was performed on a SignaHDxt 1.5-T system (GE Healthcare, Milwaukee, WI, USA) with an eight-element phased-array surface coil or a Magnetom Skyra 3.0-T system (Siemens, Erlangen, Germany) with a 32-channel body coil. The specific scanning parameters and contrast medium administration of CMR-MPI are described in the Suppl. material.

ICA: ICA (AlluraXper FD-10; Philips Medical Systems, Eindhoven, The Netherlands) was performed in direct accordance with societal guidelines. A minimum of six projections was obtained.

Image reconstruction and interpretation

Cardiac CT: CCTA datasets were reconstructed using an automated algorithm (Best Phase, Siemens Medical Solutions) of cardiac-phase selection. All CT datasets were transferred to a three-dimensional workstation (Vitrea® 2, Version 4; Vital Images, Plymouth, MN, USA). Coronary segments of the three main coronary arteries and their major side branches with a luminal diameter ≥ 1.5 mm were classified according to a modified 16-segment American heart Association (AHA) coronary model (17). Coronary segments were considered non-interpretable if any of the following were present: extensively calcified plaque or an obfuscating stent that precluded coronary luminal assessment or significant motion artifacts. Coronary arteries with a luminal diameter reduction of ≥50% or with non-evaluable segments were considered “positive” for anatomically obstructive coronary stenosis.

The static stress PCT and the late-phase CT datasets were visually evaluated using LV short-axis multiplanar reformatted images according to the AHA 17-segment model and three vascular territorial distributions (18). The PD was defined as being a contiguous, circumscribed area of low attenuation conforming to the coronary artery territory (≥ 2 segments) within the LV myocardium at both the end-systolic and mid-diastolic phases. PD on either systolic or diastolic phases was regarded as motion or beam-hardening artifacts (19). The presence of PD but no delayed enhancement (DE) at late-phase CT was defined as myocardial ischemia. The transmurality of the DE at late-phase CT suggestive of myocardial infarction (MI) in each segment was defined visually (20). Matching of perfusion segments to corresponding vascular territories and assessment of CT and CMR image quality are described in the Suppl. material. The assessment of PD and DE on CMR-MPI, and the quantitative assessment of stenosis severity on ICA are described in the supplementary material.

Hemodynamically significant coronary stenosis and reference standard

An angiographically significant stenotic or non-evaluable vessel was considered to cause or not cause ischemia if a PD was observed or not observed, respectively, in the same vascular territory on the SSPCT and the combined ICA/CMR-MPI. A PD in a vascular territory subtended by a coronary vessel with <50% stenosis was considered a false-positive result (21).

Statistical analysis

Quantitative variables are expressed as means ± standard deviation, and categorical variables as frequencies or percentages. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated from 2 × 2 contingency tables, and their respective 95% confidence intervals (CIs) were calculated from the binomial proportion. The area under the receiver operating characteristic curve (AUC) analysis was performed to evaluate the discriminatory ability of CT. Kappa (κ) statistic values were used to determine intermodality concordance and inter-observer agreement. A P < 0.05 was considered to indicate significance for all analyses. All statistical analyses were performed using the SAS software, ver. 9.4 (SAS Institute, Cary, NC, USA).

Results

Patient population

Twenty-nine patients were included and all patients successfully completed the study protocol with no adverse events. The pretest probability of the CAD was intermediate in 34% and high in 66% of the study population. Table 1 summarizes the characteristics of the patients.

Table 1.

Baseline characteristics of study patients (n = 29).

Characteristics	Total (n = 29)
Mean age (years)	63.9 ± 9.1
Male (n, (%))	21 (72%)
Body mass index (kg/m²)	26.2 ± 3.9
Risk factors (n (%))
Smoking	14 (48)
Hypertension	17 (59)
Diabetes mellitus	11 (38)
Hyperlipidemia	16 (55)
Obesity	4 (14)
Family history	4 (14)
Systolic BP (mmHg)	131 ± 19 (105–176)
Diastolic BP (mmHg)	77 ± 13 (54–112)
Biomarker of lipid level (mg/dL)
Total cholesterol	185.8 ± 38.8
HDL cholesterol	58.0 ± 13.9
LDL cholesterol	111.5 ± 39.2
Serum triglyceride	172.1 ± 133.4
Medical history (n (%))
Previous angina pectoris	18 (62)
Previous myocardial infarction	5 (17)
Prior cerebrovascular accident	0 (0)
Prior coronary revascularization	4 (14)
Baseline medication (n (%))
Aspirin	14 (48)
Anti-hypertension	9 (31)
Statin	9 (31)

Values are n (%) or means ± standard deviations (95% CI).

Obesity was defined as a BMI ≥ 30 kg/m². Hyperlipidemia was defined as total cholesterol >240 mg/dL, triglycerides >200 mg/dL, or treatment for hypercholesterolemia. Hypertension was defined as blood pressure >140/90 mmHg or treatment for hypertension.

Scan protocol findings

Cardiac CT: Table 2 summarizes characteristics of each CT protocol. The total radiation dose was 7.4 ± 1.2 mSv. The mean best reconstruction phase for the CCTA was end-systolic phase in 14 patients or mid-diastolic phase in 15 patients. The median Agatston calcium score was 150 (interquartile range = 282.55). Four (5%) coronary vessels in four patients were considered non-evaluable due to extensive calcification (n = 2) or a cardiac motion artifact due to heart rates >80 beats per minute (bpm; n = 2). All 29 patients with 60 (69%) arteries were categorized with anatomically obstructive CAD on CCTA. At PCT and late-phase CT, 464 (100%) segments in 29 patients were interpretable. PDs were identified in 26 (90%) patients, 51 (59%) vascular territories, and 181 (39%) segments. In 26 patients with PDs, nine (31%), nine (31%), and eight (28%) had a defect involving one-vessel, two-vessel, or three-vessel territories, respectively (Figs. 3 and 4). DE was observed in five (17%) patients and nine (10%) vascular territories (three left anterior descending coronary arteries [LADs], three left circumflex arteries [LCXs], and three right coronary arteries [RCAs]). The five territories were located in the subendocardium (25–50% transmurality) and four in the transmural wall (51–75% transmurality). All of the territories corresponded to those of PDs on PCT. The κ value for inter-observer agreement of CCTA and PCT for 87 vascular territories were 0.77 (95% CI = 0.62–0.91) and 0.81 (95% CI = 0.69–0.94), respectively.

Table 2.

Heart rate, image quality, and radiation dose for CT protocol (n = 29).

	Heart rate (bpm)	Image quality	Radiation dose (mSv)
Calcium scan	63 ± 7	1.1 ± 0.4	0.8 ± 0.2 (0.36–1.2)
SSPCT	73 ± 10	1.5 ± 0.6 (PCT)	5.2 ± 1.1 (3.2–7.0)
		1.8 ± 0.5 (CCTA)
Late-phase CT	67 ± 8	1.6 ± 0.6	1.4 ± 0.2 (1.1–2.0)

Values are numbers or means ± standard deviations.

CT, computed tomography; SSPCT, single-shot stress perfusion computed tomography; bpm, beats per minute.

Fig. 3.

Images in a 59-year-old man with significant edge in-stent restenosis. (a) Curved multiplanar reformatted coronary CT angiography image showed significant, discrete stenosis in the proximal edge of the proximal left LAD stent (arrow). (b, c) Static stress perfusion CT images acquired at the end-systolic (b) and mid-diastolic (c) phases showed transmural perfusion defects in the mid-anterior and anteroseptal left ventricular (LV) wall (arrowheads). (d) Late-phase CT did not show delayed contrast enhancement in the LV wall. (e–g) Cardiovascular magnetic resonance myocardial perfusion imaging acquired at stress (e), rest (f), and delayed contrast enhancement (g) showed fixed subendocardial perfusion defects and delayed hyperenhancement in the mid-anterior LV wall (f, g, arrows) and complete reversible subendocardial perfusion defect in the mid-anteroseptal LV wall (e, arrowheads). (h) Invasive coronary angiography image confirmed severe in-stent restenosis (arrow) at the proximal edge of proximal LAD stent.

Fig. 4.

Images in a 54-year-old man with multi-vessel CAD. (a–c) Multiplanar reformatted CCTA images showed extensively calcified plaques (arrow) in the middle LAD (a) and significant, discrete stenoses in the middle (arrowhead) and distal (arrow) RCA (b), and last obtuse marginal branch (arrow) (c, OM). (d, e) Static stress perfusion CT images acquired at the end-systolic (d) and mid-diastolic (e) phases showed myocardial perfusion defects in the mid-anterior, anteroseptal and inferior LV wall (arrowheads). (f) Late-phase CT did not show delayed contrast enhancement in the mid-LV wall. (g–i) Cardiovascular magnetic resonance myocardial perfusion imaging acquired at stress (g), rest (h), and delayed enhancement (i) showed complete reversible subendocardial perfusion defects in the mid-anterior, anteroseptal, and inferior LV wall (arrowheads) and subendocardial delayed hyperenhancement in the mid-inferior LV wall (i, arrow). (j, k) Invasive coronary angiography images showed significant stenoses in the middle (j, arrowhead) and distal RCA (j, arrow), middle LAD (k, arrowhead), first diagonal branch (k, short arrow), and last OM branch (k, long arrow). RCA stenoses did not show perfusion defects in the corresponding RCA territories.

CMR-MPI: CMR-MPI was performed in 14 patients using the 1.5-T MR scanner and in 15 patients using the 3.0-T MR scanner. All CMR-MPIs were obtained within 3.3 ± 3.4 days of SSPCT, with an average Likert score of 1.3 ± 0.4. All segments in 29 patients were interpretable for stress/rest perfusion and DE images. PDs were identified in 23 (79%) patients, 48 (55%) vascular territories, and 187 (40%) segments. In patients with PDs on CMR-MPI, eight (28%) had a defect involving one-vessel territory, five (17%) in two-vessel territories, and ten (34%) in three-vessel territories. DEs were identified in ten (34%) patients and 15 (17%) vascular territories (six LADs, four LCXs, and five RCAs). The extent of DE was 11 non-transmural ([n = 8, 26–50% transmurality] and [n = 3, 1–25% transmurality]) and four transmural (51–75% transmurality). All of the territories corresponded to those of PDs on stress/rest perfusion CMR. The κ value for inter-observer agreement of CMR-MPI for 87 vascular territories was 0.89 (95% CI = 0.79–0.98).

ICA: All ICAs were obtained within 10.0 ± 8.8 days of SSPCT and CMR-MPI 6.7 ± 4.9 days of CMR-MPI. More than one significantly stenosed coronary artery was noted in 26 (90%) patients, of whom 19 (66%) had significant stenoses in RCA territory, 24 (83%) in LAD territory, and 14 (48%) in LCX territory. Seven (24%) patients had one-vessel disease, seven (24%) had two-vessel disease, and 12 (41%) had three-vessel disease.

Diagnostic performance characteristics

Hemodynamically significant stenoses by combined ICA/CMR-MPI were noted in 23 (79%) patients with 47 (54%) vessel territories. The per-vessel and per-patient diagnostic performance, agreement, and discrimination of CCTA alone, PCT alone, and SSPCT are listed in Table 3. The per-vessel sensitivity, specificity, PPV, and NPV were 96%, 63%, 75%, and 93%, respectively, for the CCTA alone, 94%, 83%, 86%, and 92%, respectively, for the PCT alone, as well as 92%, 88%, 90%, and 90%, respectively, for the SSPCT, as compared to those of the combined ICA/CMR-MPI. CCTA alone tended to be inferior to PCT alone in the receiver operating characteristic (ROC) analysis for hemodynamically significant CAD detection in both per-vessel (0.79 vs. 0.88, P = 0.06) and per-patient-based (0.5 vs. 0.75, P = 0.03) analyses. SSPCT identified 27 (93%) patients and 48 (55%) vessel territories with hemodynamically significant stenosis. Of the four non-evaluable arteries on CCTA, two (50%) with extensive calcification were significantly stenosed on combined ICA/CMR-MPI (Fig. 4). False-positive PDs were seen in four LAD territories with eight segments, one RCA territory with two segments, and two LCX territories with four segments on PCT. Compared with CCTA alone, SSPCT showed a significant increase in the AUC in a per-vessel-based analysis (0.79 vs. 0.90, P = 0.013) (Fig. 5), but a non-significant increase in AUC in a per-patient-based analysis (0.5 vs. 0.67, P = 0.35). The AUC for SSPCT was not significantly different from that for PCT alone in both vessel-based and patient-based analyses.

Table 3.

Per-vessel territory and per-patient diagnostic accuracy of CCTA, PCT, and SSPCT compared with ICA/CMR-MPI (significant stenosis ≥ 50%).

	CCTA	PCT	SSPCT
Vascular territory analysis
Sensitivity (%)	96 (89–98) (45/47)	94 (86–97) (44/47)	92 (84–96) (43/47)
Specificity (%)	63 (52–72) (25/40)	83 (73–89) (33/40)	88 (79–93) (35/40)
PPV (%)	75 (65–83) (45/60)	86 (78–92) (44/51)	90 (81–94) (43/48)
NPV (%)	93 (85–97) (25/27)	92 (84–96) (33/36)	90 (82–95) (35/39)
Accuracy (%)	81 (71–87) (70/87)	89 (80–94) (77/87)	90 (82–95) (78/87)
κ Value	0.60 (0.43–0.76)	0.77 (0.63–0.90)	0.79 (0.66–0.92)
AUC	0.79 (0.69–0.87)	0.88 (0.79–0.94)	0.90 (0.81–0.95)
Per-patient analysis
Sensitivity (%)	100 (85–100) (23/23)	100 (88–100) (23/23)	100 (88–100) (23/23)
Specificity (%)	0 (0–46) (0/6)	50 (33–67) (3/6)	33 (19–52) (2/6)
PPV (%)	79 (60–92) (23/29)	89 (72–96) (23/26)	85 (68–94) (23/27)
NPV (%)		100 (88–100) (3/3)	100 (88–100) (2/2)
Accuracy (%)	79 (60–92) (23/29)	90 (74–96) (26/29)	86 (68–96) (25/29)
κ Value	0	0.61 (0.23–1.00)	0.44 (0.02–0.86)
AUC	0.5 (0.31–0.69)	0.75 (0.56–0.89)	0.67 (0.47–0.83)

Values for sensitivity, specificity, PPV, NPV, accuracy, kappa statistic, and AUC presented with 95% CI.

CCTA, coronary computed tomography angiography; PCT, perfusion computed tomography; SSPCT, single-shot stress perfusion computed tomography; CMR-MPI, cardiac magnetic resonance-myocardial perfusion imaging; PPV, positive predictive value; NPV, negative predictive value; AUC, area under the curve.

Fig. 5.

ROC curves. CCTA alone, PCT alone, and static SSPCT (combined CCTA and PCT) protocol as predictors of hemodynamically relevant CAD. Static SSPCT had the best diagnostic performance as indicated by the ROC curve analysis.

Discussion

We hypothesized that the acquisition of a coronary artery and stress myocardial perfusion could be combined into a single CT scan in stress (static SSPCT) and be a feasible method for the identification of a hemodynamically significant CAD. The static SSPCT had good diagnostic accuracy for detecting hemodynamically significant coronary stenoses as defined by combined ICA/CMR-MPI in comparison to CCTA alone in a per-vascular territory analysis. In addition, PCT alone exhibited a diagnostic performance for hemodynamically significant stenoses in both vessel-based and patient-based analyses similar to that of SSPCT.

CMR-MPI has excellent diagnostic performance for discriminating hemodynamically significant from insignificant stenosis compared with that of FFR (22 –24). Accordingly, combined ICA/CMR-MPI is sufficient as a reference standard for collecting anatomic and physiologic information regarding coronary stenosis. Bettencourt et al. demonstrated that stress PCT is globally inferior to CMR-MPI but that combined CCTA/PCT has similar diagnostic performance as CMR-MPI (14). In our study, SSPCT had high diagnostic accuracy for detecting hemodynamically significant coronary stenoses, resulting in a significant improvement in specificity, PPV, and AUC as well as reclassification of two of four non-evaluable arteries on SSPCT in comparison to CCTA alone. The diagnostic accuracy is in agreement with that of a previous study (15). Interestingly, SSPCT demonstrated no further improvement in detection of hemodynamically significant coronary artery stenoses in comparison to PCT alone. Accordingly, PCT alone may be sufficient for diagnosing hemodynamically significant stenoses in patients with suspected or known CAD.

Our study used different scanning and diagnosis protocols from those used in previous studies, which had diagnostic and acceptable image quality for the CCTA and the stress PCT images in all patients (15). Even though multiple cardiac phases using the 64-slice dual-source CT were used for static SSPCT in this study, five patients were excluded and two coronary arteries were not assessable for CCTA because of severe cardiac motion artifacts due to a too high heart rate. Seven vascular territories were false-positive PD on PCT compared with combined ICA/CMR-MPI because of beam hardening artifacts and cardiac motion artifacts. Quality of interpretation of coronary artery on CCTA was lower than that of PCT. Therefore, cardiac motion artifacts and suboptimal temporal resolution of the CT scanner posed a dilemma for the use of static SSPCT identifying anatomically significant coronary stenoses and myocardial PDs. Also, cardiac phases and change for optimal scan timing on SSPCT may influence the image quality and diagnostic performance for detection of significant CAD.

Late-phase CT is feasible for assessment of MI and viability using DE (20,25). However, our study did not show that late-phase CT provided incremental diagnostic value over SSPCT for the detection of subendocardial MI. Six subendocardial MIs were not detected on late-phase CT. Bettencourt et al. also demonstrated that late-phase CT did not improve diagnostic performance of stress/rest PCT for detection of significant CAD in symptomatic patients with suspected CAD (26). Even though there is no consensus regarding the optimal acquisition protocol for late-phase CT, our late-phase CT protocol was neither optimal nor well-established in terms of a relatively small volumes of contrast material and relatively early delay time. In an animal model, the contrast between the infarcted myocardium and the normal myocardium was equally prominent at both 5 min and 10 min on the late-phase CT images (27). Late-phase CT without additional use of iodinated contrast medium may not be suitable for detection of MI. Accordingly, we acquired the late phase at 5 min after SSPCT instead of 10–15 min after contrast administration. The late-phase CT acquisition may be implemented in a SSPCT protocol with use of the optimized scan parameters including contrast administration and timing of DE images.

The identification of hemodynamically significant coronary stenosis is now accurately evaluable with FFR-CT which can be performed on a “simple” CCTA dataset with the advantage of a significant reduction of radiation exposure. However, FFR-CT is technically demanding, time-consuming, and expensive thus limiting its use in routine clinical practice (28). CCTA could allow rule-out of CAD in patients with low and intermediate pre-test probability, so that in such patients, SSPCT would not be necessary. In case of limited availability of MRI scanners or contraindications to CMR, with the use of state-of-the-art CT scanners, static SSPCT may be useful as an alternative method in the assessment of CAD. Patients with intermediate coronary stenosis by ICA may be considered to be a candidate for SSPCT in the evaluation of atherosclerotic plaque characteristics as well as the hemodynamic significance of coronary stenoses. SSPCT can be also applied to patients with a high coronary calcium score or stent.

This study had several limitations. First, it was subject to the limitations inherent to a single institution and enrolled a small number of highly selected patients. The high prevalence of CAD may influence the PPV and NPV of the tests studied and undermine an evaluation of the role of CCTA alone, but strengthen the role of PCT alone. Second, the PDs assessed by the visual analysis on the static stress PCT lacked the quantitative assessment of myocardial blood flow (29). Third, the diagnostic performance of SSPCT could be biased by excluded patients who were dissatisfied with non-diagnostic image quality of SSPCT. Fourth, the images of the CCTA and the late-phase CT were rated as being acceptable for diagnostic quality but lower in quality as compared with the dedicated CCTA and the late-phase CT images. Finally, we did not perform other functional studies, such as FFR, for comparison of diagnostic performance.

In conclusion, static SSPCT in patients with suspected or known CAD detected hemodynamically significant coronary stenoses compared with those of combined ICA/CMR-MPI. Further studies are needed to compare the diagnostic accuracy of the static SSPCT using cutting-edge CT scanners with that of the combined ICA/FFR in relevant and larger patient cohorts.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This paper was supported by Konkuk University.

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