Clinical Outcomes of Dynamic Computed Tomography Myocardial Perfusion Imaging Combined With Coronary Computed Tomography Angiography Versus Coronary Computed Tomography Angiography–Guided Strategy

Coronary Artery Disease: Role of Computed Tomography and Recent Advances

In this review, the authors summarize the role of coronary computed tomography angiography and coronary artery calcium scoring in different clinical presentations of chest pain and preventative care and discuss future directions and new technologies such as pericoronary fat inflammation and the growing footprint of artificial intelligence in cardiovascular medicine.

Feasibility and Diagnostic Performance of Functional SYNTAX Score Derived From Dynamic CT Myocardial Perfusion Imaging

BACKGROUND

Computed tomography (CT) fractional flow reserve (FFR)-derived functional SYNTAX score (FSSCT-FFR) is a valuable method for guiding treatment strategy in patients with multivessel coronary artery disease. Dynamic CT myocardial perfusion imaging (CT-MPI) demonstrates higher diagnostic accuracy than CT-FFR in identifying hemodynamically significant coronary artery disease. We aimed to evaluate the feasibility of CT-MPI-derived FSS (FSSCT-MPI) with reference to invasive FSS.

METHODS

In this retrospective study, patients with multivessel coronary artery disease who underwent dynamic CT-MPI+ coronary CT angiography and invasive coronary angiography or FFR within 4 weeks were consecutively included. Invasive (FSSinvasive) and noninvasive FSS (FSSCT-MPI and FSSCT-FFR) were calculated by an online calculator, which assigned points to lesions with hemodynamic significance (defined as FFRinvasive ≤0.80, invasive coronary angiography diameter stenosis ≥90%, CT-FFR ≤0.80, and myocardial ischemia on CT-MPI). Weighted κ value and net reclassification index were calculated to determine the consistency and incremental discriminatory power of FSSCT-MPI. Receiver operating characteristic curve analysis was used for the comparison of FSSCT-MPI and FSSCT-FFR in detecting intermediate- to high-risk patients.

RESULTS

A total of 119 patients (96 men; 64.6±10.6 years) with 305 obstructive lesions were included. The average FSSCT-MPI, FSSCT-FFR, and FSSinvasive were 15.58±13.03, 16.18±13.30, and 13.11±12.22, respectively. The agreement on risk classification based on the FSSCT-MPI tertiles was good (weighted κ, 0.808). With reference to FSSinvasive, FSSCT-MPI correctly reclassified 27 (22.7%) patients from the intermediate- to high SYNTAX score group to the low-score group (net reclassification index, 0.30; P<0.001). In patients with severe calcification, FSSCT-MPI had better diagnostic value than FSSCT-FFR in detecting intermediate- to high-risk patients when compared with FSSinvasive (area under the curve, 0.976 versus 0.884; P<0.001).

CONCLUSIONS

Noninvasive FSS derived from CT-MPI is feasible and has strong concordance with FSSinvasive. It allows accurate categorization of FSS in patients with multivessel coronary artery disease, in particular with severe calcification.

A stepwise strategy integrating dynamic stress CT myocardial perfusion and deep learning-based FFRCT in the work-up of stable coronary artery disease

OBJECTIVES

To validate a novel stepwise strategy in which computed tomography-derived fractional flow reserve (FFRCT) is restricted to intermediate stenosis on coronary computed tomography angiography (CCTA) and computed tomography myocardial perfusion imaging (CT-MPI) was reserved for vessels with gray zone FFRCT values.

MATERIALS AND METHODS

This retrospective study included 87 consecutive patients (age, 58 ± 10 years; 70% male) who underwent CCTA, dynamic CT-MPI, interventional coronary angiography (ICA), and fractional flow reserve (FFR) for suspected or known coronary artery disease. FFRCT was computed using a deep learning-based platform. Three stepwise strategies (CCTA + FFRCT + CT-MPI, CCTA + FFRCT, CCTA + CT-MPI) were constructed and their diagnostic performance was evaluated using ICA/FFR as the reference standard. The proportions of vessels requiring further ICA/FFR measurement based on different strategies were noted. Furthermore, the net reclassification index (NRI) was calculated to ascertain the superior model.

RESULTS

The CCTA + FFRCT + CT-MPI strategy yielded the lowest proportion of vessels requiring additional ICA/FFR measurement when compared to the CCTA + FFRCT and CCTA + CT-MPI strategies (12%, 22%, and 24%). The CCTA + FFRCT + CT-MPI strategy exhibited the highest accuracy for ruling-out (91%, 84%, and 85%) and ruling-in (90%, 85%, and 85%) functionally significant lesions. All strategies exhibited comparable sensitivity for ruling-out functionally significant lesions and specificity for ruling-in functionally significant lesions (p > 0.05). The NRI indicated that the CCTA + FFRCT + CT-MPI strategy outperformed the CCTA + FFRCT strategy (NRI = 0.238, p < 0.001) and the CCTA + CT-MPI strategy (NRI = 0.233%, p < 0.001).

CONCLUSIONS

The CCTA + FFRCT + CT-MPI stepwise strategy was superior to the CCTA + FFRCT strategy and CCTA+ CT-MPI strategy by minimizing unnecessary invasive diagnostic catheterization without compromising the agreement rate with ICA/FFR.

CLINICAL RELEVANCE STATEMENT

Our novel stepwise strategy facilitates greater confidence and accuracy when clinicians need to decide on interventional coronary angiography referral or deferral, reducing the burden of invasive investigations on patients.

KEY POINTS

• A stepwise CCTA + FFRCT + CT-MPI strategy holds promise as a viable method to reduce the need for invasive diagnostic catheterization, while maintaining a high level of agreement with ICA/FFR. • The CCTA + FFRCT + CT-MPI strategy performed better than the CCTA + FFRCT and CCTA + CT-MPI strategies. • A stepwise CCTA + FFRCT + CT-MPI strategy allows to minimize unnecessary invasive diagnostic catheterization and helps clinicians to referral or deferral for ICA/FFR with more confidence.

Dynamic CT Myocardial Perfusion: The Role of Functional Evaluation in the Diagnosis of Coronary Artery Disease

Coronary computed tomography angiography (CTA) is a widely accepted, non-invasive diagnostic modality for the evaluation of patients with suspected coronary artery disease (CAD). However, a limitation of CTA is its inability to provide information on the hemodynamic significance of the coronary lesion. The recently developed stress dynamic CT perfusion technique has emerged as a potential solution to this diagnostic challenge. Dynamic CT myocardial perfusion provides information on the hemodynamic consequences of coronary stenosis and is used to detect myocardial ischemia. The combination of stress dynamic CT myocardial perfusion with CTA provides a comprehensive assessment that integrates anatomical and functional information. CT myocardial perfusion has been validated in several clinical studies and has shown comparable accuracy to Positron Emission Tomography (PET) and stress magnetic resonance imaging (MRI) in the diagnosis of hemodynamically significant coronary stenosis and superior performance to Single Photon Emission Computed Tomography (SPECT). More importantly, CTP-derived myocardial perfusion has been shown to have a strong correlation with FFR, and the use of CTP results in a reduction of negative catheterizations. In the context of suspected stable coronary artery disease, the CT protocol with dynamic perfusion imaging combined with CTA eliminates the need for additional testing, making it a convenient "one-stop-shop" method and an effective gatekeeper to an invasive approach.

Financial and clinical outcomes of CT myocardial perfusion imaging and coronary CT angiography-guided versus coronary CT angiography-guided strategy

OBJECTIVES

To compare the financial and clinical outcomes of CT myocardial perfusion imaging (CT-MPI) + coronary CT angiography (CCTA)-guided versus CCTA-guided strategy in patients suspected of chronic coronary syndrome (CCS).

MATERIALS AND METHODS

This study retrospectively included consecutive patients suspected of CCS and referred for CT-MPI+CCTA-guided and CCTA-guided treatment. The details of medical costs within 3 months after index imaging, including downstream invasive procedures, hospitalization, and medications, were recorded. All patients were followed up for major adverse cardiac events (MACE) at a median time of 22 months.

RESULTS

A total of 1335 patients (559 in the CT-MPI+CCTA group and 776 in the CCTA group) were finally included. In the CT-MPI+CCTA group, 129 patients (23.1%) underwent ICA and 95 patients (17.0%) received revascularization. In the CCTA group, 325 patients (41.9%) underwent ICA whereas 194 patients (25.0%) received revascularization. An addition of CT-MPI in the evaluation strategy remarkably reduced the healthcare expenditure, compared with CCTA-guided strategy (USD 1441.36 vs. USD 232.91, p < 0.001). After adjustment for potential cofounders after inverse probability weighting, the CT-MPI+CCTA strategy was significantly associated with lower medical expenditure [adjusted cost ratio (95% CI) for total costs: 0.77 (0.65-0.91), p < 0.001]. In addition, there was no significant difference regarding the clinical outcome between the two groups (adjusted HR= 0.97; p = 0.878).

CONCLUSIONS

CT-MPI+CCTA considerably reduced medical expenditures in patients suspected of CCS, compared to the CCTA strategy alone. Moreover, CT-MPI+CCTA led to a lower rate of invasive procedures with a similar long-term prognosis.

CLINICAL RELEVANCE STATEMENT

CT myocardial perfusion imaging + coronary CT angiography-guided strategy reduced medical expenditure and invasive procedure rate.

KEY POINTS

• CT-MPI+CCTA strategy yielded significantly lower medical expenditure than did the CCTA strategy alone in patients with suspected CCS. • After adjustment for potential confounders, the CT-MPI+CCTA strategy was significantly associated with lower medical expenditure. • No significant difference was observed regarding the long-term clinical outcome between the two groups.

Should we choose CT angiography first instead of SPECT/PET first for the diagnosis and management of coronary artery disease?

In patients presenting with chest pain, current guidelines recommend the use of coronary computed tomography angiography and single-photon emission tomography/positron emission tomography, both with equal class 1 indication and level of evidence A. There is no clear recommendation on which test should be used as a first-line test. The choice of the test should be based on individualized clinical risk assessment, patient characteristics, local expertise/availability, and patient preferences. In this context, it is fair to ask which non-invasive imaging test to choose. The debate reproduced in this article answers this question by summarizing the considerations in selecting present state-of-the-art criteria of the right test for the right patient to ensure efficient resource utilization, minimize unnecessary testing, and maximize diagnostic accuracy and therapeutic efficacy.

Dynamic myocardial perfusion computed tomography with mental stress test to detect changes in myocardial microcirculation in patients with anxiety and no obstructive coronary artery disease

OBJECTIVE

Mental stress can induce myocardial ischemia in patients with anxiety and other psychological disorders. Computed tomography myocardial perfusion imaging (CT-MPI) has the potential to quantitatively diagnose myocardial ischemia. The aim of this study was to measure changes in myocardial microcirculation perfusion (MMP) in patients with anxiety who have angina symptoms/ischemia but no obstructive coronary artery disease (INOCA) using dynamic CT-MPI in combination with a mental stress test.

METHODS

Patients with INOCA were divided into five subgroups (none, minimal, mild, moderate, and severe) according to the generalized anxiety disorder scale. Patients underwent dynamic CT-MPI with mental stress testing using a series of the standardized color word/arithmetic stressors. Myocardial blood flow (MBF) during resting and stress phases of CT-MPI was recorded.

RESULTS

Fifty-eight patients with 986 segments were included for final analysis. Compared to patients with none, minimal, mild, and moderate anxiety, those with severe anxiety had the largest rate of MBF decrease and the largest MBF decrease value. At the same time, those with no anxiety had the largest rate of MBF increase, the largest MBF increase value (all p < 0.05). As anxiety intensified, the rate of MBF increased and the MBF value increased (r = -0.24, r = -0.27, p < 0.05). Concomitantly, the rate of MBF decreased and the MBF value decreased (r = 0.63, r = 0.43, p < 0.05).

CONCLUSIONS

Dynamic CT-MPI with a mental stress test can be used to evaluate MMP in patients with anxiety and INOCA. Mental stress resulted in significant differences in changes in the rate and value of MBF among patients with different anxiety degrees.

KEY POINTS

• Dynamic CT-MPI with mental stress test worked well to quantitatively evaluate myocardial microcirculation perfusion in patients with anxiety and INOCA. • The rates of MBF decrease and MBF decrease value were positively correlated with anxiety degree of anxiety patients with INOCA. • MBF change derived from CT-MPI with mental stress test had a good performance to predicting anxiety degree of patients with anxiety and INOCA.

Evaluation of Myocardial Microcirculation in Rats under a High-Altitude Hypoxic Environment by Computed Tomography Myocardial Perfusion Imaging

This study aims to examine the changes in myocardial microcirculation in rats in a high-altitude hypoxic environment via computed tomography (CT) myocardial perfusion imaging technology. Rats in two groups were raised in different environments from 4 weeks of age for a period of 24 weeks. At 28 weeks of age, both groups underwent CT myocardial perfusion scanning, and the following myocardial perfusion parameters were measured: time to peak (TTP), mean transit time (MTT), blood flow (BF), and blood volume (BV). Following the scan, the rats were sacrificed, the cardiac index and right ventricular hypertrophy index were obtained, and hematoxylin-eosin (HE) staining was utilized to observe the pathological changes in the myocardium. In the group of rats that are subject to a high-altitude hypoxic environment for 24 weeks (the high-altitude group), the TTP and MTT values were increased (P < 0.05), the BF and BV values were lower (P < 0.05), the right heart mass was higher (P < 0.05) than that in the low-altitude group. As shown by the pathological results of HE staining, the gap between cardiomyocytes in the high-altitude group was widened, the arrangement of cardiomyocytes was irregular, and the cells were filled with a few fat vacuoles. The myocardial microcirculation is altered in a high-altitude hypoxic environment. In particular, the myocardium is in a state of inadequate perfusion, the BF in the myocardium slows down, and the right heart displays compensatory hypertrophy.

Current Concepts and Future Applications of Non-Invasive Functional and Anatomical Evaluation of Coronary Artery Disease

Over the last decades, significant advances have been achieved in the treatment of coronary artery disease (CAD). Proper non-invasive diagnosis and appropriate management based on functional information and the extension of ischemia or viability remain the cornerstone in the fight against adverse CAD events. Stress echocardiography and single photon emission computed tomography are often used for the evaluation of ischemia. Advancements in non-invasive imaging modalities such as computed tomography (CT) coronary angiography and cardiac magnetic resonance imaging (MRI) have not only allowed non-invasive imaging of coronary artery lumen but also provide additional functional information. Other characteristics regarding the plaque morphology can be further evaluated with the latest modalities achieving a morpho-functional evaluation of CAD. Advances in the utilization of positron emission tomography (PET), as well as software advancements especially regarding cardiac CT, may provide additional prognostic information to a more evidence-based treatment decision. Since the armamentarium on non-invasive imaging modalities has evolved, the knowledge of the capabilities and limitations of each imaging modality should be evaluated in a case-by-case basis to achieve the best diagnosis and treatment decision. In this review article, we present the most recent advances in the noninvasive anatomical and functional evaluation of CAD.

Influence of Different Segmentations on the Diagnostic Performance of Pericoronary Adipose Tissue

Objective

To investigate the influence of different segmentations on the diagnostic performance of pericoronary adipose tissue (PCAT) CT attenuation and radiomics features for the prediction of ischemic coronary artery stenosis.

Methods

From June 2016 to December 2018, 108 patients with 135 vessels were retrospectively analyzed in the present study. Vessel-based PCAT was segmented along the 40 mm-long proximal segments of three major epicardial coronary arteries, while lesion-based PCAT was defined around coronary lesions. CT attenuation and radiomics features derived from two segmentations were calculated and extracted. The diagnostic performance of PCAT CT attenuation or radiomics models in predicting ischemic coronary stenosis were also compared between vessel-based and lesion-based segmentations.

Results

The mean PCAT CT attenuation was −75.7 ± 9.1 HU and −76.1 ± 8.1 HU (p = 0.395) for lesion-based and vessel-based segmentations, respectively. A strong correlation was found between vessel-based and lesion-based PCAT CT attenuation for all cohort and subgroup analyses (all p < 0.01). A good agreement for all cohort and subgroup analyses was also detected between two segmentations. The diagnostic performance was comparable between vessel-based and lesion based PCAT CT attenuation in predicting ischemic stenosis. The radiomics features of PCAT based on vessel or lesion segmentation can both adequately identify the ischemic stenosis. However, no significant difference was detected between the two segmentations.

Conclusions

The quantitative evaluation of PCAT can be reliably measured both from vessel-based and lesion-based segmentation. Furthermore, the radiomics analysis of PCAT may potentially help predict hemodynamically significant coronary artery stenosis.

The use of lesion-specific calcium morphology to guide the appropriate use of dynamic CT myocardial perfusion imaging and CT fractional flow reserve

Background

We aimed to optimize the diagnostic strategy for dynamic computed tomography myocardial perfusion imaging (CT-MPI) and CT fractional flow reserve (CT-FFR) in the evaluation of coronary artery disease (CAD).

Methods

Patients who had undergone coronary CT angiography (CCTA) + dynamic CT-MPI and invasive coronary angiography (ICA)/FFR within a 4-week period were retrospectively included. Lesion-specific characteristics were recorded, and multivariate logistic regression was performed to determine the predictors of mismatched CT findings with ICA results. An optimized diagnostic strategy was proposed based on the diagnostic performance of dynamic CT-MPI and CT-FFR compared with ICA/FFR. A net reclassification index (NRI) was calculated to determine the incremental discriminatory power of optimized CT-FFR + dynamic CT-MPI strategy compared to CT-FFR alone.

Results

The study included 180 patients with 229 diseased vessels. For CT-FFR, a calcified lesion with a calcium arc >180° was the only independent predictor for misdiagnosis of ischemic coronary stenosis (odds ratio =2.367; P=0.002). For noncalcified lesions and calcified lesions with a calcium arc ≤180°, the sensitivity and negative predictive value (NPV) of CT-FFR were similar to those of CT-MPI (all P values >0.05), whereas the specificity and positive predictive value (PPV) of CT-FFR were significantly lower (all P values <0.05). For calcified lesions with a calcium arc >180°, the specificity, NPV, and PPV of CT-FFR were inferior to those of CT-MPI (21.2% vs. 100%, 58.3% vs. 86.8%, and 62.9% vs. 100%, respectively; all P values <0.05). As guided by lesion-specific calcium morphology, an optimized CT-FFR + dynamic CT-MPI strategy (NRI =0.2; P=0.004) would have resulted in a 27.0% and 33.9% reduction of radiation dose and contrast medium consumption, respectively, and 25.3% of patients would have avoided unnecessary invasive tests.

Conclusions

The diagnostic performance of CT-FFR was significantly inferior in lesions with a calcium arc >180°. Lesion-specific calcium morphology is the preferred parameter to guide the appropriate use of CT-based functional assessment.

Myocardial CT perfusion imaging for the detection of obstructive coronary artery disease: multisegment reconstruction does not improve diagnostic performance

BACKGROUND

Multisegment reconstruction (MSR) was introduced to shorten the temporal reconstruction window of computed tomography (CT) and thereby reduce motion artefacts. We investigated whether MSR of myocardial CT perfusion (CTP) can improve diagnostic performance in detecting obstructive coronary artery disease (CAD) compared with halfscan reconstruction (HSR).

METHODS

A total of 134 patients (median age 65.7 years) with clinical indication for invasive coronary angiography and without cardiac surgery prospectively underwent static CTP. In 93 patients with multisegment acquisition, we retrospectively performed both MSR and HSR and searched both reconstructions for perfusion defects. Subgroups with known (n = 68) or suspected CAD (n = 25) and high heart rate (n = 30) were analysed. The area under the curve (AUC) was compared applying DeLong approach using ≥ 50% stenosis on invasive coronary angiography as reference standard.

RESULTS

Per-patient analysis revealed the overall AUC of MSR (0.65 [95% confidence interval 0.53, 0.78]) to be inferior to that of HSR (0.79 [0.69, 0.88]; p = 0.011). AUCs of MSR and HSR were similar in all subgroups analysed (known CAD 0.62 [0.45, 0.79] versus 0.72 [0.57, 0.86]; p = 0.157; suspected CAD 0.80 [0.63, 0.97] versus 0.89 [0.77, 1.00]; p = 0.243; high heart rate 0.46 [0.19, 0.73] versus 0.55 [0.33, 0.77]; p = 0.389). Median stress radiation dose was higher for MSR than for HSR (6.67 mSv versus 3.64 mSv, p < 0.001).

CONCLUSIONS

MSR did not improve diagnostic performance of myocardial CTP imaging while increasing radiation dose compared with HSR.

TRIAL REGISTRATION

CORE320: clinicaltrials.gov NCT00934037, CARS-320: NCT00967876.

Calcium Scoring at Coronary CT Angiography Using Deep Learning

Background Separate noncontrast CT to quantify the coronary artery calcium (CAC) score often precedes coronary CT angiography (CTA). Quantifying CAC scores directly at CTA would eliminate the additional radiation produced at CT but remains challenging. Purpose To quantify CAC scores automatically from a single CTA scan. Materials and Methods In this retrospective study, a deep learning method to quantify CAC scores automatically from a single CTA scan was developed on training and validation sets of 292 patients and 73 patients collected from March 2019 to July 2020. Virtual noncontrast scans obtained with a spectral CT scanner were used to develop the algorithm to alleviate tedious manual annotation of calcium regions. The proposed method was validated on an independent test set of 240 CTA scans collected from three different CT scanners from August 2020 to November 2020 using the Pearson correlation coefficient, the coefficient of determination, or r², and the Bland-Altman plot against the semiautomatic Agatston score at noncontrast CT. The cardiovascular risk categorization performance was evaluated using weighted κ based on the Agatston score (CAC score risk categories: 0-10, 11-100, 101-400, and >400). Results Two hundred forty patients (mean age, 60 years ± 11 [standard deviation]; 146 men) were evaluated. The positive correlation between the automatic deep learning CTA and semiautomatic noncontrast CT CAC score was excellent (Pearson correlation = 0.96; r² = 0.92). The risk categorization agreement based on deep learning CTA and noncontrast CT CAC scores was excellent (weighted κ = 0.94 [95% CI: 0.91, 0.97]), with 223 of 240 scans (93%) categorized correctly. All patients who were miscategorized were in the direct neighboring risk groups. The proposed method's differences from the noncontrast CT CAC score were not statistically significant with regard to scanner (P = .15), sex (P = .051), and section thickness (P = .67). Conclusion A deep learning automatic calcium scoring method accurately quantified coronary artery calcium from CT angiography images and categorized risk. © RSNA, 2021 See also the editorial by Goldfarb and Cao et al in this issue.

Prognostic value of CT-derived myocardial blood flow, CT fractional flow reserve and high-risk plaque features for predicting major adverse cardiac events

Background

Myocardial blood flow (MBF), CT fractional flow reserve (CT-FFR) and high-risk plaque (HRP) features have been revealed to be associated with patients' prognosis. However, direct intra-individual comparison of these CT-derived parameters has not been explored yet. The aim of this study was to investigate the prognostic value of CT-derived MBF, CT-FFR and HRP features for predicting major adverse cardiac events (MACEs).

Methods

Consecutive patients with chest pain and intermediate-to-high pre-test probability of coronary artery disease (CAD) were prospectively enrolled. All patients were referred for dynamic CT myocardial perfusion imaging (CT-MPI) + coronary CT angiography (CCTA) and followed up for at least 1 year. MBF_ischemic (mean MBF of all ischemic segments), MBF_ratio (MBF of ischemic segments/MBF of reference segments), CT-FFR and HRP features were measured and multivariate analysis was used to evaluate the predictive value of all above parameters for MACEs.

Results

One hundred and forty-two patients were included into final analysis. MBF_ischemic and MBF_ratio was significantly lower in patients with MACE compared to patients without MACE (87 vs. 153 mL/100 mL/min and 0.64 vs. 0.95, both P<0.001). Similarly, CT-FFR was also markedly lower in patients with MACE (0.58 vs. 0.88, P<0.001) whereas coronary artery calcium score (CACS) was significantly higher (1,038.9 vs. 34.2, P<0.001). According to ROC curve analysis, MBF_ischemic, MBF_ratio and CACS had largest area under curve (AUC =0.872, 0.855 and 0.813 respectively, all P<0.001) for identifying patients with MACE. After adjusted by multivariate analysis, MBF_ischemic (hazard ratio =23.382, P=0.003) and CACS (hazard ratio =3.759, P=0.029) were revealed to be the independent predictors for MACE where CT-FFR and HRP features failed to have prognostic value.

Conclusions

MBF_ischemic derived from dynamic CT-MPI was the strongest predictor for MACE, followed by CACS. MBF_ischemic outperformed HRP features and CT-FFR for prediction of unfavorable clinical outcome.

A Novel Computed Tomography-Based Imaging Approach for Etiology Evaluation in Patients With Acute Coronary Syndrome and Non-obstructive Coronary Angiography

Objective: This study sought to investigate the diagnostic value of dynamic CT myocardial perfusion imaging (CT-MPI) combined with coronary CT angiography (CCTA) in acute coronary syndrome (ACS) patients without obstructive coronary angiography. Methods: Consecutive ACS patients with normal or non-obstructive coronary angiography findings who had cardiac magnetic resonance (CMR) contraindications or inability to cooperate with CMR examinations were prospectively enrolled and referred for dynamic CT-MPI + CCTA + late iodine enhancement (LIE). ACS etiology was determined according to combined assessment of coronary vasculature by CCTA, quantified myocardial blood flow (MBF) and presence of LIE. Results: Twenty two patients were included in the final analysis. CCTA revealed two cases of side branch occlusion and one case of intramural hematoma which were overlooked by invasive angiography. High risk plaques were observed in 6 (27.3%) patients whereas myocardial ischemia was presented in 19 (86.4%) patients with varied extent and severity. LIE was positive in 13 (59.1%) patients and microvascular obstruction was presented in three cases with side branch occlusion or spontaneous intramural hematoma. The specific etiology was identified in 20 (90.9%) patients, of which the most common cause was cardiomyopathies (41%), followed by microvascular dysfunction (14%) and plaque disruption (14%). Conclusion: Dynamic CT-MPI + CCTA was able to reveal the potential etiologies in majority of patients with ACS and non-obstructive coronary angiography. It may be a useful alternative to CMR for accurate etiology evaluation.

Dynamic Myocardial Perfusion CT for the Detection of Hemodynamically Significant Coronary Artery Disease

OBJECTIVES

In this international, multicenter study, using third-generation dual-source computed tomography (CT), we investigated the diagnostic performance of dynamic stress CT myocardial perfusion imaging (CT-MPI) in addition to coronary CT angiography (CTA) compared to invasive coronary angiography (ICA) and invasive fractional flow reserve (FFR).

BACKGROUND

CT-MPI combined with coronary CTA integrates coronary artery anatomy with inducible myocardial ischemia, showing promising results for the diagnosis of hemodynamically significant coronary artery disease in single-center studies.

METHODS

At 9 centers in Europe, Japan, and the United States, 132 patients scheduled for ICA were enrolled; 114 patients successfully completed coronary CTA, adenosine-stress dynamic CT-MPI, and ICA. Invasive FFR was performed in vessels with 25% to 90% stenosis. Data were analyzed by independent core laboratories. For the primary analysis, for each coronary artery the presence of hemodynamically significant obstruction was interpreted by coronary CTA with CT-MPI compared to coronary CTA alone, using an FFR of ≤0.80 and angiographic severity as reference. Territorial absolute myocardial blood flow (MBF) and relative MBF were compared using C-statistics.

RESULTS

ICA and FFR identified hemodynamically significant stenoses in 74 of 289 coronary vessels (26%). Coronary CTA with ≥50% stenosis demonstrated a per-vessel sensitivity, specificity, and accuracy for the detection of hemodynamically significant stenosis of 96% (95% CI: 91–100), 72% (95% CI: 66–78), and 78% (95% CI: 73–83), respectively. Coronary CTA with CT-MPI showed a lower sensitivity (84%; 95% CI: 75–92) but higher specificity (89%; 95% CI: 85–93) and accuracy (88%; 95% CI: 84–92). The areas under the receiver-operating characteristic curve of absolute MBF and relative MBF were 0.79 (95% CI: 0.71–0.86) and 0.82 (95% CI: 0.74–0.88), respectively. The median dose-length product of CT-MPI and coronary CTA were 313 mGy·cm and 138 mGy·cm, respectively.

CONCLUSIONS

Dynamic CT-MPI offers incremental diagnostic value over coronary CTA alone for the identification of hemodynamically significant coronary artery disease. Generalized results from this multicenter study encourage broader consideration of dynamic CT-MPI in clinical practice. (Dynamic Stress Perfusion CT for Detection of Inducible Myocardial Ischemia [SPECIFIC]; NCT02810795)

Coronary Computed Tomographic Angiography for Complete Assessment of Coronary Artery Disease: JACC State-of-the-Art Review

Coronary computed tomography angiography (CTA) has shown great technological improvements over the last 2 decades. High accuracy of CTA in detecting significant coronary stenosis has promoted CTA as a substitute for conventional invasive coronary angiography in patients with suspected coronary artery disease. In patients with coronary stenosis, CTA-derived physiological assessment is surrogate for intracoronary pressure and velocity wires, and renders possible decision-making about revascularization solely based on computed tomography. Computed tomography coronary anatomy with functionality assessment could potentially become a first line in diagnosis. Noninvasive imaging assessment of plaque burden and morphology is becoming a valuable substitute for intravascular imaging. Recently, wall shear stress and perivascular inflammation have been introduced. These assessments could support risk management for both primary and secondary cardiovascular prevention. Anatomy, functionality, and plaque composition by CTA tend to replace invasive assessment. Complete CTA assessment could provide a 1-stop-shop for diagnosis, risk management, and decision-making on treatment.

Myocardial perfusion imaging using computed tomography: Current status, clinical value and prognostic implications

Combined anatomical and functional evaluation of coronary artery disease (CAD) using computed tomography (CT) has recently emerged as an accurate, robust, and non-invasive tool for the evaluation of ischemic heart disease. Cardiac CT has become a one-stop-shop imaging modality that allows the simultaneous depiction, characterization, and quantification of coronary atherosclerosis and the assessment of myocardial ischemia. Advancements in scanner technology (improvements in spatial and temporal resolution, dual-energy imaging, wide detector panels) and the implementation of iterative reconstruction algorithms enables the detection of myocardial ischemia in both qualitative and quantitative fashion using low-dose scanning protocols. The addition of CT perfusion (CTP) to standard coronary CT angiography is a reliable tool to improve diagnostic accuracy. CTP using static first-pass imaging enables qualitative assessment of the myocardial tissue, whereas dynamic perfusion imaging can also provide quantitative information on myocardial blood flow. Myocardial tissue assessment by CTP holds the potential to refine risk in stable chest pain or microvascular dysfunction. CTP can aid the detection of residual ischemia after coronary intervention. Comprehensive evaluation of CAD using CTP might therefore improve the selection of patients for aggressive secondary prevention therapy or coronary revascularization with high diagnostic certainty. In addition, prognostic information provided by perfusion CT imaging could improve patient outcomes by quantifying the ischemic burden of the left ventricle. The current review focuses on the clinical value of myocardial perfusion imaging by CT, current status of CTP imaging and the use of myocardial CTP in various patient populations for the diagnosis of ischemic heart disease.

Design and rationale of randomized CT-PRECISION study

Background

Coronary computed tomography angiography (CCTA) combined with dynamic CT myocardial perfusion imaging (CT-MPI) and CCTA combined with CT fractional flow reserve (CT-FFR) are both expected to be efficient one-stop shop imaging strategies to guide clinical management. The aim of the study is to determine which of these two methods has superiority in terms of guiding treatment in patients with intermediate to high pretest probability of coronary artery disease (CAD).

Methods

CT-PRECISION (Computed Tomography myocardial PeRfusion imaging vErsus Computed tomography derived fractional flow reServe: impact ON guiding treatment and prognosis in patients with intermediate to high pretest probability of CAD) is a multicenter, prospective, open-label, randomized study to directly compare the clinical value of guiding treatment and prognostic discrimination of CCTA + dynamic CT-MPI strategy and CCTA + CT-FFR strategy in patients with intermediate to high pretest probability of CAD. Four hundred and twelve patients will be enrolled in this study and randomized to CCTA + dynamic CT-MPI arm and CCTA + CT-FFR arm. All patients will be followed up for at least 2 years. The primary endpoint is the rate of unnecessary invasive coronary angiography (ICA) within 90 days, which is defined as ICA without revascularization. The secondary endpoints will include: (I) a composite of major adverse cardiac events (MACE, defined as all-cause mortality, non-fatal myocardial infarction, rehospitalization due to aggravated angina symptoms, and late revascularization); (II) symptom change at 1 year; (III) the rate of late revascularization after CT examination; (IV) reclassification rate of CCTA + dynamic CT-MPI and CCTA + CT-FFR guided strategies compared with CCTA alone; (V) overall radiation dose, contrast media usage and medical cost.

Discussion

The study will provide valuable information about the optimal CT-based diagnostic strategy with regard to the clinical management of patients with intermediate to high pretest probability of CAD.

Trial registration

The study is registered at Chinese Clinical Trial Registry (ChiCTR) with the identifier number ChiCTR2000041102. The first enrollment is planned for January 2021.

Prevalence and disease features of myocardial ischemia with non-obstructive coronary arteries: Insights from a dynamic CT myocardial perfusion imaging study

BACKGROUND

Ischemia with non-obstructive coronary arteries (INOCA) is not uncommon in clinical practice. However, the incidence and imaging characteristics of INOCA on dynamic CT myocardial perfusion imaging (CT-MPI) remains unclear. We aimed to investigate the prevalence and disease features of INOCA as evaluated by dynamic CT-MPI + coronary CT angiography (CCTA).

METHODS

Patients with suspected chronic coronary syndrome and intermediate-to-high pre-test probability of obstructive CAD (according to updated Diamond and Forrester Chest Pain Prediction Rule) were referred for dynamic CT-MPI + CCTA and retrospectively included. Various parameters, including myocardial blood flow (MBF) and high-risk plaque (HRP) features, were measured. INOCA was diagnosed if patients were revealed to have myocardial ischemia and absence of obstructive stenosis.

RESULTS

314 patients were finally included. 20 patients (6.4%) were observed to have myocardial ischemia without obstructive stenosis. In addition, 138 patients (43.9%) had normal or near normal findings, 101 patients (32.2%) had obstructive stenosis without myocardial ischemia and 55 patients (17.5%) had obstructive stenosis with myocardial ischemia. Compared with patients with normal/near normal findings, patients with INOCA showed a higher prevalence of positive remodeling (40.0% vs. 17.4%, p = 0.04). In patients with obstructive stenosis, the mean age, calcium score and incidence of spotty calcification, positive remodeling as well as HRPs were significantly higher than those in patients with INOCA (p < 0.05 for all).

CONCLUSIONS

The overall prevalence of INOCA was low in patients with suspected chronic coronary syndrome. HRPs were less frequently presented in patients with INOCA, compared with patients having obstructive coronary stenosis.