Additional value of dipyridamole stress myocardial perfusion by 64-row computed tomography in patients with coronary stents

Diagnostic accuracy of subendocardial vs. transmural myocardial perfusion defect for the detection of in-stent restenosis or progression of coronary artery disease after percutaneous coronary intervention

BACKGROUND

The ADVANTAGE study demonstrated in a cohort of stented patients a diagnostic accuracy of stress myocardial CT perfusion (CTP) significantly higher than that of coronary CT angiography (CCTA) for the detection of in-stent restenosis (ISR) or CAD progression vs. quantitative coronary angiography (QCA). This is a pre-defined subanalysis of the ADVANTAGE aimed at assessing the difference in terms of diagnostic accuracy vs. QCA of a subendocardial vs. a transmural perfusion defect using static stress CTP.

METHODS

We enrolled consecutive patients who previously underwent coronary stenting and were referred for QCA. All patients underwent stress CTP and rest CTP ​+ ​CCTA. The diagnostic accuracy of CCTA and CTP were evaluated in territory-based and patient-based analyses. We compared the diagnostic accuracy of "subendocardial" perfusion defect, defined as hypo-enhancement encompassing >25% but <50% of the transmural myocardial thickness within a specific coronary territory vs. "transmural" perfusion defect, defined as hypo-enhancement encompassing >50% of the transmural thickness.

RESULTS

In 150 patients (132 men, mean age 65.1 ​± ​9.1 years), the diagnostic accuracy of subendocardial vs. transmural perfusion defect in a vessel-based analysis was 93.5% vs. 87.7%, respectively (p ​< ​0.0001). The sensitivity and specificity of subendocardial vs. transmural defect were 87.9% vs. 46.9% (p ​< ​0.001) and 94.9% vs. 97.9% (p ​= ​0.004), respectively. In a patient-based analysis, the diagnostic accuracy of the subendocardial vs. transmural approach was 86.6% vs. 68% (p ​< ​0.0001).

CONCLUSIONS

This study shows that detection of a subendocardial perfusion defect as compared to a transmural defect is significantly more accurate to identify coronary territories with ISR or CAD progression.

Cost-effectiveness of stress CTP versus CTA in detecting obstructive CAD or in-stent restenosis in stented patients

Objectives

The aim of this retrospective study was to determine cost-effectiveness of stress myocardial CT perfusion (CTP), coronary CT angiography (CTA), and the combination of both in suspected obstructive coronary artery disease (CAD) or in-stent restenosis (ISR) in patients with previous coronary stent implantation.

Methods

A decision model based on Markov simulations estimated lifetime costs and quality-adjusted life years (QALYs) associated with CTA, CTP, and CTA + CTP. Model input parameters were obtained from published literature. Probabilistic sensitivity analysis was performed to evaluate overall model uncertainty. A single-variable deterministic sensitivity analysis evaluated the sensitivity of the results to plausible variations in model inputs. Cost-effectiveness was assessed based on a cost-effectiveness threshold of $100,000 per QALY.

Results

In the base-case scenario with willingness to pay of $100,000 per QALY, CTA resulted in total costs of $47,013.87 and an expected effectiveness of 6.84 QALYs, whereas CTP resulted in total costs of $46,758.83 with 6.93 QALYs. CTA + CTP reached costs of $47,455.63 with 6.85 QALYs. Therefore, strategies CTA and CTA + CTP were dominated by CTP in the base-case scenario. Deterministic sensitivity analysis demonstrated robustness of the model to variations of diagnostic efficacy parameters and costs in a broad range. CTP was cost-effective in the majority of iterations in the probabilistic sensitivity analysis as compared with CTA.

Conclusions

CTP is cost-effective for the detection of obstructive CAD or ISR in patients with previous stenting and therefore should be considered a feasible approach in daily clinical practice.

Key Points

• CTP provides added diagnostic value in patients with previous coronary stents.

• CTP is a cost-effective method for the detection of obstructive CAD or ISR in patients with previous stenting.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-07202-z) contains supplementary material, which is available to authorized users.

Evaluation of Myocardial Perfusion by Computed Tomography - Principles, Technical Background and Recommendations

Coronary computed tomography angiography (CCTA) has gained a prominent role in the evaluation of coronary artery disease. However, its anatomical nature does not allow the evaluation of the functional repercussion of coronary obstructions. It has been made possible to evaluate Myocardial computed tomography perfusion (Myocardial CTP) recently, based on myocardial contrast changes related to coronary stenoses. Several studies have validated this technique against the anatomical reference method (cardiac catheterization) and other functional methods, including myocardial perfusion scintigraphy and fractional flow reserve. The Myocardial CTP is performed in conjunction with the CCTA, a combined analysis of anatomy and function. The stress phase (with assessment of myocardial perfusion) can be performed before or after the resting phase (assessment of resting perfusion and coronary arteries), and different acquisition parameters are proposed according to the protocol and type of equipment used. Stressors used are based on coronary vasodilation (e.g. dipyridamole, adenosine). Image interpretation, similar to other perfusion assessment methods, is based on the identification and quantification of myocardial perfusion defects. The integration of both perfusion and anatomical findings is fundamental for the examination interpretation algorithm, allowing to define if the stenoses identified are hemodynamically significant and may be related to myocardial ischemia.

Optimal Scan Time for Single-Phase Myocardial Computed Tomography Perfusion to Detect Myocardial Ischemia - Derivation Cohort From Dynamic Myocardial Computed Tomography Perfusion

BACKGROUND

Single-phase myocardial computed tomography perfusion (CTP) is useful for detecting myocardial ischemia, but determining the optimal scan time is difficult. The present study evaluated this by analyzing dynamic CTP data.Methods and Results:We retrospectively selected 32 patients, all of whom had undergone stress dynamic CTP and magnetic resonance myocardial perfusion imaging (MR-MPI). Myocardial ischemia was assessed by MR-MPI using the 16-segment model. Whole-heart dynamic CTP data were acquired for 30 consecutive heartbeats without spatial or temporal gaps using a wide-detector CT, and redistributed into 11 series of single-phase CTP acquired from -2 s to 8 s from the time of maximal enhancement (Tmax) in the ascending aorta. Single-phase CTP images were visually assessed at the segment level, and diagnostic performance of single-phase CTP images for detecting myocardial ischemia was compared with dynamic CTP. Of 512 segments, 177 segments (35%) were diagnosed as ischemic by MR-MPI. The diagnostic accuracy of single-phase CTP acquired at 2-6 s from Tmax in the ascending aorta (median 86%, range 84-87%) was comparable to that of dynamic CTP.

CONCLUSIONS

The optimal scan time for detecting myocardial ischemia with single-phase CTP was at 2-6 s from Tmax in the ascending aorta. (Circ J 2016; 80: 2506-2512).

Functional Evaluation of Coronary Disease by CT Angiography

In recent years, several technical developments in the field of cardiac computed tomography (CT) have made possible the extraction of functional information from an anatomy-based examination. Several different lines have been explored and will be reviewed in the present paper, namely: 1) myocardial perfusion imaging; 2) transluminal attenuation gradients and corrected coronary opacification indexes; 3) fractional flow reserve computed from CT; and 4) extrapolation from atherosclerotic plaque characteristics. In view of these developments, cardiac CT has the potential to become in the near future a truly 2-in-1 noninvasive evaluation for coronary artery disease.

Rationale and design of the dual-energy computed tomography for ischemia determination compared to "gold standard" non-invasive and invasive techniques (DECIDE-Gold): A multicenter international efficacy diagnostic study of rest-stress dual-energy computed tomography angiography with perfusion

BACKGROUND

Dual-energy CT (DECT) has potential to improve myocardial perfusion for physiologic assessment of coronary artery disease (CAD). Diagnostic performance of rest-stress DECT perfusion (DECTP) is unknown.

OBJECTIVE

DECIDE-Gold is a prospective multicenter study to evaluate the accuracy of DECT to detect hemodynamic (HD) significant CAD, as compared to fractional flow reserve (FFR) as a reference standard.

METHODS

Eligible participants are subjects with symptoms of CAD referred for invasive coronary angiography (ICA). Participants will undergo DECTP, which will be performed by pharmacological stress, and participants will subsequently proceed to ICA and FFR. HD-significant CAD will be defined as FFR ≤ 0.80. In those undergoing myocardial stress imaging (MPI) by positron emission tomography (PET), single photon emission computed tomography (SPECT) or cardiac magnetic resonance (CMR) imaging, ischemia will be graded by % ischemic myocardium. Blinded core laboratory interpretation will be performed for CCTA, DECTP, MPI, ICA, and FFR.

RESULTS

Primary endpoint is accuracy of DECTP to detect ≥1 HD-significant stenosis at the subject level when compared to FFR. Secondary and tertiary endpoints are accuracies of combinations of DECTP at the subject and vessel levels compared to FFR and MPI.

CONCLUSION

DECIDE-Gold will determine the performance of DECTP for diagnosing ischemia.

Combined coronary angiography and myocardial perfusion by computed tomography in the identification of flow-limiting stenosis - The CORE320 study: An integrated analysis of CT coronary angiography and myocardial perfusion

BACKGROUND

The combination of coronary CT angiography (CTA) and myocardial CT perfusion (CTP) is gaining increasing acceptance, but a standardized approach to be implemented in the clinical setting is necessary.

OBJECTIVES

To investigate the accuracy of a combined coronary CTA and myocardial CTP comprehensive protocol compared to coronary CTA alone, using a combination of invasive coronary angiography and single photon emission CT as reference.

METHODS

Three hundred eighty-one patients included in the CORE320 trial were analyzed in this study. Flow-limiting stenosis was defined as the presence of ≥50% stenosis by invasive coronary angiography with a related perfusion defect by single photon emission CT. The combined CTA + CTP definition of disease was the presence of a ≥50% stenosis with a related perfusion defect. All data sets were analyzed by 2 experienced readers, aligning anatomic findings by CTA with perfusion defects by CTP.

RESULTS

Mean patient age was 62 ± 6 years (66% male), 27% with prior history of myocardial infarction. In a per-patient analysis, sensitivity for CTA alone was 93%, specificity was 54%, positive predictive value was 55%, negative predictive value was 93%, and overall accuracy was 69%. After combining CTA and CTP, sensitivity was 78%, specificity was 73%, negative predictive value was 64%, positive predictive value was 0.85%, and overall accuracy was 75%. In a per-vessel analysis, overall accuracy of CTA alone was 73% compared to 79% for the combination of CTA and CTP (P < .0001 for difference).

CONCLUSIONS

Combining coronary CTA and myocardial CTP findings through a comprehensive protocol is feasible. Although sensitivity is lower, specificity and overall accuracy are higher than assessment by coronary CTA when compared against a reference standard of stenosis with an associated perfusion defect.

Comprehensive assessment of radiation dose estimates for the CORE320 study

OBJECTIVE. The purpose of this study was to comprehensively study estimated radiation doses for subjects included in the main analysis of the Combined Non-invasive Coronary Angiography and Myocardial Perfusion Imaging Using 320 Detector Computed Tomography (CORE320) study ( ClinicalTrials.gov identifier NCT00934037), a clinical trial comparing combined CT angiography (CTA) and perfusion CT with the reference standard catheter angiography plus myocardial perfusion SPECT. SUBJECTS AND METHODS. Prospectively acquired data on 381 CORE320 subjects were analyzed in four groups of testing related to radiation exposure. Radiation dose estimates were compared between modalities for combined CTA and perfusion CT with respect to covariates known to influence radiation exposure and for the main clinical outcomes defined by the trial. The final analysis assessed variations in radiation dose with respect to several factors inherent to the trial. RESULTS. The mean radiation dose estimate for the combined CTA and perfusion CT protocol (8.63 mSv) was significantly (p < 0.0001 for both) less than the average dose delivered from SPECT (10.48 mSv) and the average dose from diagnostic catheter angiography (11.63 mSv). There was no significant difference in estimated CTA-perfusion CT radiation dose for subjects who had false-positive or false-negative results in the CORE320 main analyses in a comparison with subjects for whom the CTA-perfusion CT findings were in accordance with the reference standard SPECT plus catheter angiographic findings. CONCLUSION. Radiation dose estimates from CORE320 support clinical implementation of a combined CT protocol for assessing coronary anatomy and myocardial perfusion.

Low dose dynamic CT myocardial perfusion imaging using a statistical iterative reconstruction method

PURPOSE

Dynamic CT myocardial perfusion imaging has the potential to provide both functional and anatomical information regarding coronary artery stenosis. However, radiation dose can be potentially high due to repeated scanning of the same region. The purpose of this study is to investigate the use of statistical iterative reconstruction to improve parametric maps of myocardial perfusion derived from a low tube current dynamic CT acquisition.

METHODS

Four pigs underwent high (500 mA) and low (25 mA) dose dynamic CT myocardial perfusion scans with and without coronary occlusion. To delineate the affected myocardial territory, an N-13 ammonia PET perfusion scan was performed for each animal in each occlusion state. Filtered backprojection (FBP) reconstruction was first applied to all CT data sets. Then, a statistical iterative reconstruction (SIR) method was applied to data sets acquired at low dose. Image voxel noise was matched between the low dose SIR and high dose FBP reconstructions. CT perfusion maps were compared among the low dose FBP, low dose SIR and high dose FBP reconstructions. Numerical simulations of a dynamic CT scan at high and low dose (20:1 ratio) were performed to quantitatively evaluate SIR and FBP performance in terms of flow map accuracy, precision, dose efficiency, and spatial resolution.

RESULTS

Forin vivo studies, the 500 mA FBP maps gave -88.4%, -96.0%, -76.7%, and -65.8% flow change in the occluded anterior region compared to the open-coronary scans (four animals). The percent changes in the 25 mA SIR maps were in good agreement, measuring -94.7%, -81.6%, -84.0%, and -72.2%. The 25 mA FBP maps gave unreliable flow measurements due to streaks caused by photon starvation (percent changes of +137.4%, +71.0%, -11.8%, and -3.5%). Agreement between 25 mA SIR and 500 mA FBP global flow was -9.7%, 8.8%, -3.1%, and 26.4%. The average variability of flow measurements in a nonoccluded region was 16.3%, 24.1%, and 937.9% for the 500 mA FBP, 25 mA SIR, and 25 mA FBP, respectively. In numerical simulations, SIR mitigated streak artifacts in the low dose data and yielded flow maps with mean error <7% and standard deviation <9% of mean, for 30 × 30 pixel ROIs (12.9 × 12.9 mm(2)). In comparison, low dose FBP flow errors were -38% to +258%, and standard deviation was 6%-93%. Additionally, low dose SIR achieved 4.6 times improvement in flow map CNR(2) per unit input dose compared to low dose FBP.

CONCLUSIONS

SIR reconstruction can reduce image noise and mitigate streaking artifacts caused by photon starvation in dynamic CT myocardial perfusion data sets acquired at low dose (low tube current), and improve perfusion map quality in comparison to FBP reconstruction at the same dose.

Regadenoson-stress myocardial CT perfusion and single-photon emission CT: rationale, design, and acquisition methods of a prospective, multicenter, multivendor comparison

Pharmacologic stress myocardial CT perfusion (CTP) has been reported to be a viable imaging modality for detection of myocardial ischemia compared with single-photon emission CT (SPECT) in several single-center studies. However, regadenoson-stress CTP has not previously been compared with SPECT in a multicenter, multivendor study. The rationale and design of a phase 2, randomized, cross-over study of regadenoson-stress myocardial perfusion imaging by CTP compared with SPECT are described herein. The study will be conducted at approximately 25 sites by using 6 different CT scanner models, including 64-, 128-, 256-, and 320-slice systems. Subjects with known/suspected coronary artery disease will be randomly assigned to 1 of 2 imaging procedure sequences; rest and regadenoson-stress SPECT on day 1, then regadenoson-stress CTP and rest CTP/coronary CT angiography (same acquisition) on day 2; or regadenoson-stress CTP and rest CTP/CT angiography on day 1, then rest and regadenoson-stress SPECT on day 2. The prespecified primary analysis examines the agreement rate between CTP and SPECT for detecting or excluding ischemia (≥2 or 0-1 reversible defects, respectively), as assessed by 3 independent blinded readers for each modality. Non-inferiority will be indicated if the lower boundary of the 95% CI for the agreement rate is within 0.15 of 0.78 (the observed agreement rate in the regadenoson pivotal trials). The protocol described herein will support the first evaluation of regadenoson-stress CTP by using multiple scanner types compared with SPECT.

Reduction of image noise in low tube current dynamic CT myocardial perfusion imaging using HYPR processing: a time-attenuation curve analysis

PURPOSE

This study describes a HighlY constrained backPRojection (HYPR) image processing method for the reduction of image noise in low tube current time-resolved CT myocardial perfusion scans. The effect of this method on myocardial time-attenuation curve noise and fidelity is evaluated in an animal model, using varying levels of tube current.

METHODS

CT perfusion scans of four healthy pigs (42-59 kg) were acquired at 500, 250, 100, 50, 25, and 10 mA on a 64-slice scanner (4 cm axial coverage, 120 kV, 0.4 s∕rotation, 50 s scan duration). For each scan a sequence of ECG-gated images centered on 75% R-R was reconstructed using short-scan filtered back projection (FBP). HYPR processing was applied to the scans acquired at less than 500 mA using parameters designed to maintain the voxel noise level in the 500-mA FBP images. The processing method generates a series of composite images by averaging over a sliding time window and then multiplies the composite images by weighting images to restore temporal fidelity to the image sequence. HYPR voxel noise relative to FBP noise was measured in AHA myocardial segment numbers 1, 5, 6, and 7 at each mA. To quantify the agreement between HYPR and FBP time-attenuation curves (TACs), Bland-Altman analysis was performed on TACs measured in full myocardial segments. The relative degree of TAC fluctuation in smaller subvolumes was quantified by calculating the root mean square deviation of a TAC about the gamma variate curve fit to the TAC data.

RESULTS

HYPR image sequences were produced using 2, 7, and 20 beat composite windows for the 250, 100, and 50 mA scans, respectively. At 25 and 10 mA, all available beats were used in the composite (41-60; average 50). A 7-voxel-wide 3D cubic filter kernel was used to form weighting images. The average ratio of HYPR voxel noise to 500-mA FBP voxel noise was 1.06, 1.10, 0.97, 1.11, and 2.15 for HYPR scans at 250, 100, 50, 25, and 10 mA. The average limits-of-agreement between HYPR and FBP TAC values measured 0.02+∕-0.91, 0.04+∕-1.92, 0.19+∕-1.59, 1.13+∕-4.22, and 1.07+∕-6.37 HU (mean difference +∕-1.96 SD). The HYPR image subvolume that yielded a fixed level of TAC fluctuations was smaller, on average, than the FBP subvolume determined at the same mA.

CONCLUSIONS

HYPR processing is a feasible method for generating low noise myocardial perfusion data from a low-mA time-resolved CT myocardial perfusion scan. The method is applicable to current clinical scanners and uses conventional image reconstructions as input data.

Myocardial perfusion imaging with cardiac computed tomography: state of the art

Cardiac computed tomography (CCT) has become an important tool for the anatomic assessment of patients with suspected coronary disease. Its diagnostic accuracy for detecting the presence of underlying coronary artery disease and ability to risk stratify patients are well documented. However, the role of CCT for the physiologic assessment of myocardial perfusion during resting and stress conditions is only now emerging. With the addition of myocardial perfusion imaging to coronary imaging, CCT has the potential to assess both coronary anatomy and its functional significance with a single non-invasive test. In this review, we discuss the current state of CCT myocardial perfusion imaging for the detection of myocardial ischemia and myocardial infarction and examine its complementary role to CCT coronary imaging.

3D left ventricular extracellular volume fraction by low-radiation dose cardiac CT: assessment of interstitial myocardial fibrosis

BACKGROUND

Myocardial fibrosis leads to impaired cardiac function and events. Extracellular volume fraction (ECV) assessed with an iodinated contrast agent and measured by cardiac CT may be a useful noninvasive marker of fibrosis.

OBJECTIVE

The purpose of this study was to develop and evaluate a 3-dimensional (3D) ECV calculation toolkit (ECVTK) for ECV determination by cardiac CT.

METHODS

Twenty-four subjects (10 systolic heart failure, age, 60 ± 17 years; 5 diastolic failure, age 56 ± 20 years; 9 matched healthy subjects, age 59 ± 7 years) were evaluated. Cardiac CT examinations were done on a 320-multidetector CT scanner before and after 130 mL of iopamidol (Isovue-370; Bracco Diagnostics, Plainsboro, NJ, USA) was administered. A calcium score type sequence was performed before and 7 minutes after contrast with single gantry rotation during 1 breath hold and single cardiac phase acquisition. ECV was calculated as (ΔHUmyocardium/ΔHUblood) × (1 - Hct) where Hct is the hematocrit, and ΔHU is the change in Hounsfield unit attenuation = HUafter iodine - HUbefore iodine. Cardiac magnetic resonance imaging was performed to assess myocardial structure and function.

RESULTS

Mean 3D ECV values were significantly higher in the subjects with systolic heart failure than in healthy subjects and subjects with diastolic heart failure (mean, 41% ± 6%, 33% ± 2%, and 35% ± 5%, respectively; P = 0.02). Interobserver and intraobserver agreements were excellent for myocardial, blood pool, and ECV (intraclass correlation coefficient, >0.90 for all). Higher 3D ECV by cardiac CT was associated with reduced systolic circumferential strain, greater end-diastolic and -systolic volumes, and lower ejection fraction (r = 0.70, r = 0.60, r = 0.73, and r = -0.68, respectively; all P < 0.001).

CONCLUSION

3D ECV by cardiac CT can be performed with ECVTK. We demonstrated increased ECV in subjects with systolic heart failure compared with healthy subjects. Cardiac CT results also showed good correlation with important functional heart biomarkers, suggesting the potential for myocardial tissue characterization with the use of 3D ECV by cardiac CT. This trial is registered at www.ClinicalTrials.gov as NCT01160471.

CT Imaging of Coronary Stents: Past, Present, and Future

Coronary stenting became a mainstay in coronary revascularization therapy. Despite tremendous advances in therapy, in-stent restenosis (ISR) remains a key problem after coronary stenting. Coronary CT angiography evolved as a valuable tool in the diagnostic workup of patients after coronary revascularization therapy. It has a negative predictive value in the range of 98% for ruling out significant ISR. As CT imaging of coronary stents depends on patient and stent characteristics, patient selection is crucial for success. Ideal candidates have stents with a diameter of 3 mm and more. Nevertheless, even with most recent CT scanners, about 8% of stents are not accessible mostly due to blooming or motion artifacts. While the diagnosis of ISR is currently based on the visual assessment of the stent lumen, functional information on the hemodynamic significance of in-stent stenosis became available with the most recent generation of dual source CT scanners. This paper provides a comprehensive overview on previous developments, current techniques, and clinical evidence for cardiac CT in patients with coronary artery stents.

Stress CT perfusion: coupling coronary anatomy with physiology

While multiple different imaging tests can be used to evaluate patients with known or suspected coronary artery disease (CAD), each of them is designed to evaluate either coronary anatomy or physiology. Recently, it has been recognized that cardiac CT can be used to evaluate stress and rest myocardial perfusion in addition to its capabilities to image the coronary arteries, thus allowing for the simultaneous evaluation of the anatomical burden and physiological significance of CAD in a single exam. In this review, the strengths and the limitations of imaging coronary anatomy and myocardial perfusion will be discussed. Next, key technical aspects of how to perform and interpret CT perfusion imaging will be summarized while providing an update of the most recent data in this emerging field. Finally, future directions and opportunities for further research will be discussed.