CT Angiography for the Prediction of Hemodynamic Significance in Intermediate and Severe Lesions

Utility of Noninvasive Testing Before Invasive Coronary Angiography in the Assessment for Revascularization

Objective

To examine the role of noninvasive testing (NIT) before invasive coronary angiography (ICA) by evaluating the association between a positive myocardial perfusion imaging (MPI) or computed tomography angiography (CTA) result and the decision to perform coronary revascularization.

Patients and Methods

We screened all patients who received ICA between August 1, 2015, and July 31, 2019, and identified those who received MPI or CTA within the preceding 12 months. We considered MPI to be a positive result if it found moderate or severe ischemia in a specific coronary territory and CTA to be a positive result if it identified a stenosis greater than 50% in any major coronary artery.

Results

Of the 17,181 individual procedures, 2183 were included. Positive CTA had an odds ratio (OR) of 2.68 (95% CI, 1.82-3.94) for revascularization and positive MPI an OR of 1.29 (95% CI, 1.07-1.56). Overall sensitivity for CTA in the prediction of revascularization was 80.4% (95% CI, 75.7%-84.6%), with vessel-level sensitivity ranging from 57.3% (95% CI, 47.5%-66.7%) to 71.8% (95% CI, 65.8%-77.4%). Overall sensitivity of MPI was 48.2% (95% CI, 44.7%-51.7%), with territory-specific sensitivity ranging from 33.7% (95% CI, 29.9%-37.7%) to 36.5% (95% CI, 32.6%-40.6%). Overall specificity for CTA was low, at 39.5% (32.9%-46.3%), but higher when evaluating at the vessel level, ranging from 60.3% (95% CI, 54.5%-66.0%) to 83.5% (95% CI, 79.6%-86.9%). Overall specificity for MPI was 58.1% (95% CI, 54.9%-61.3%), with territory-specific specificity ranging from 78.6% (95% CI, 76.1%-80.9%) to 78.9% (95% CI, 76.5%-81.3%).

Conclusion

In this population of patients referred for ICA, positive CTA was more closely associated with revascularization than MPI. Further studies are necessary to determine the role of NIT before ICA.

Accuracy of coronary computed tomography angiography-derived quantitative flow ratio for onsite assessment of coronary lesions

BACKGROUND

Coronary computed tomography angiography (CCTA)-derived Murray law-based quantitative flow ratio (CT-μFR) is a novel non-invasive method for fast computation of fractional flow reserve (FFR) from CCTA images, yet its diagnostic performance remains to be prospectively validated.

AIMS

We aimed to evaluate the diagnostic performance of onsite CT-μFR in patients with coronary artery disease.

METHODS

This prospective, single-centre trial enrolled patients with ≥1 lesion with 30-90% diameter stenosis on CCTA and planned invasive coronary angiography (ICA) within 30 days. CT-μFR, ICA-derived μFR and FFR were evaluated separately in a blinded fashion. The primary endpoint was the diagnostic accuracy of CT-μFR in identifying patients with haemodynamically significant coronary stenosis defined by the invasive standard: FFR ≤0.80, or μFR ≤0.80 when FFR was not available.

RESULTS

Between December 2020 and August 2023, 260 patients were consecutively enrolled. Paired comparison between CT-μFR and the invasive standard was obtained in 706 vessels from 260 patients. The patient-level accuracy of CT-μFR was 89.6% (95% confidence interval [CI]: 85.9-93.4%), which was significantly higher than the prespecified target of 72.0% (p<0.001). Sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios for CT-μFR were 93.1%, 86.1%, 87.1%, 92.5%, 6.7, and 0.1, respectively. Out of the 231 vessels investigated by FFR, the accuracy of CT-μFR in vessels without extensive calcification was non-inferior to that of μFR (90.6% vs 88.9%; difference=1.8% [95% CI: -2.8 to 5.5%]; p for non-inferiority<0.001).

CONCLUSIONS

The study met its prespecified primary endpoint of the diagnostic accuracy of CT-μFR in identifying patients with haemodynamically significant coronary stenosis. CT-μFR was non-inferior to ICA-derived μFR in vessels without extensive calcification. (ClinicalTrials.gov: NCT04665817).

Ultra-high-resolution CT vs. invasive angiography for detecting hemodynamically significant coronary artery disease: Rationale and methods of the CORE-PRECISION multicenter study

BACKGROUND

Direct coronary arterial evaluation via computed tomography (CT) angiography is the most accurate noninvasive test for the diagnosis of coronary artery disease (CAD). However, diagnostic accuracy is limited in the setting of severe coronary calcification or stents. Ultra-high-resolution CT (UHR-CT) may overcome this limitation, but no rigorous study has tested this hypothesis.

METHODS

The CORE-PRECISION is an international, multicenter, prospective diagnostic accuracy study testing the non-inferiority of UHR-CT compared to invasive coronary angiography (ICA) for identifying patients with hemodynamically significant CAD. The study will enroll 150 patients with history of CAD, defined as prior documentation of lumen obstruction, stenting, or a calcium score ≥400, who will undergo UHR-CT before clinically prompted ICA. Assessment of hemodynamically significant CAD by UHR-CT and ICA will follow clinical standards. The reference standard will be the quantitative flow ratio (QFR) with <0.8 defined as abnormal. All data will be analyzed in independent core laboratories.

RESULTS

The primary outcome will be the comparative diagnostic accuracy of UHR-CT vs. ICA for detecting hemodynamically significant CAD on a patient level. Secondary analyses will focus on vessel level diagnostic accuracy, quantitative stenosis analysis, automated contour detection, in-depth plaque analysis, and others.

CONCLUSION

CORE-PRECISION aims to investigate if UHR-CT is non-inferior to ICA for detecting hemodynamically significant CAD in high-risk patients, including those with severe coronary calcification or stents. We anticipate this study to provide valuable insights into the utility of UHR-CT in this challenging population and for its potential to establish a new standard for CAD assessment.

Agreement of Fractional Flow Reserve Estimated by Computed Tomography With Invasively Measured Fractional Flow Reserve: A Systematic Review and Meta-Analysis

BACKGROUND

Fractional flow reserve (FFR) is the ratio of blood pressure measured distal to a stenosis and pressure proximal to a stenosis. FFR can be estimated noninvasively using computed tomography (CT) although the usefulness of this technique remains controversial. This meta-analysis evaluated the agreement of FFR estimated by CT (FFR-CT) with invasively measured FFR. The study also evaluated the diagnostic accuracy of FFR-CT, defined as the ability of FFR-CT to classify lesions as hemodynamically significant (invasive FFR ≤0.8) or insignificant (invasive FFR >0.8).

METHODS AND RESULTS

Forty-three studies reporting on 7291 blood vessels from 5236 patients were included. A moderate positive linear relationship between FFR-CT and invasively measured FFR was observed (Spearman correlation coefficient: 0.67). Agreement between the 2 measures increased as invasively measured FFR values approached 1. The overall diagnostic accuracy, sensitivity and specificity of FFR-CT were 82.2%, 80.9%, and 83.1%, respectively. Diagnostic accuracy of 90% could be demonstrated for FFR-CT values >0.90 and <0.49. The diagnostic accuracy of off-site tools was 79.4% and the diagnostic accuracy of on-site tools was 84.1%.

CONCLUSIONS

The agreement between FFR-CT and invasive FFR is moderate although agreement is highest in vessels with FFR-CT >0.9. Diagnostic accuracy varies widely with FFR-CT value but is above 90% for FFR-CT values >0.90 and <0.49. Furthermore, on-site and off-site tools have similar performance. Ultimately, FFR-CT may be a useful adjunct to CT coronary angiography as a gatekeeper for invasive coronary angiogram.

Long-term prognostic implications of CT angiography-derived fractional flow reserve: Results from the DISCOVER-FLOW study

BACKGROUND & OBJECTIVES

The long-term prognostic implications of CT angiography-derived fractional flow reserve (FFRCT) remains unclear. We aimed to explore the long-term outcomes of FFRCT in the first-in-human study of it.

MATERIALS & METHODS

A total of 156 vessels from 102 patients with stable coronary artery disease, who underwent coronary CT angiography (CCTA) and invasive FFR measurement, were followed. The primary endpoint was target vessel failure (TVF), including cardiovascular death, target vessel myocardial infarction, and target vessel revascularization. Outcome analysis with FFRCT was performed on a per-vessel basis using a marginal Cox proportional hazard model.

RESULTS

During median 9.9 years of follow-up, TVF occurred in 20 (12.8%) vessels. FFRCT ​≤0.80 discriminated TVF (hazard ratio [HR] 2.61, 95% confidence interval [CI] 1.06, 6.45). Among 94 vessels with deferral of percutaneous coronary intervention (PCI), TVF risk was inversely correlated with FFRCT ​(HR 0.62 per 0.1 increase, 95% CI 0.44, 0.86), with the cumulative incidence of TVF being 2.6%, 15.2%, and 28.6% for vessels with FFRCT ​>0.90, 0.81-0.90, and ≤0.80, respectively (p-for-trend 0.005). Predictive value for clinical outcomes of FFRCT was similar to that of invasive FFR (c-index 0.79 vs 0.71, P ​= ​0.28). The estimated TVF risk was higher in the deferral of PCI group than the PCI group for vessels with FFRCT ≤0.81.

CONCLUSION

FFRCT showed improved long-term risk stratification and displayed a risk continuum similar to invasive FFR.

CLINICAL TRIAL REGISTRATION

NCT01189331.

Selective Use of CT Fractional Flow at a Large Academic Medical Center: Insights from Clinical Implementation after 1 Year of Practice

Purpose This special report outlines a retrospective observational study of CT fractional flow reserve (CT-FFR) analysis using dual-source coronary CT angiography (CTA) scans performed without heart rate control and its impact on clinical outcomes. Materials and Methods All patients who underwent clinically indicated coronary CTA between August 2020 and August 2021 were included in this retrospective observational study. Scans were performed in the late systolic to early diastolic period without heart rate control and analyzed at the interpreting physician's discretion. Demographics, coronary CTA features, and rates of invasive coronary angiography (ICA), percutaneous coronary intervention (PCI), myocardial infarction, and all-cause death at 3 months were assessed by chart review. Results During the study period, 3098 patients underwent coronary CTA, of whom 113 with coronary bypass grafting were excluded. Of the remaining 2985 patients, 292 (9.7%) were referred for CT-FFR analysis. Two studies (0.7%) were rejected from CT-FFR analysis, and six (2.1%) analyses did not evaluate the lesion of concern. A total of 160 patients (56.3%) had CT-FFR greater than 0.80. Among patients with significant stenosis at coronary CTA, patients who underwent CT-FFR analysis presented with lower rates of ICA (74.5% vs 25.5%, P = .04) and PCI (78.9% vs 21.1%, P = .05). Conclusion CT-FFR was implemented in patients not requiring heart rate control by using dual-source coronary CTA acquisition and showed the potential to decrease rates of ICA and PCI without compromising safety in patients with significant stenosis and an average heart rate of 65 beats per minute. Keywords: Angiography, CT, CT-Angiography, Fractional Flow Reserve, Cardiac, Heart, Arteriosclerosis Supplemental material is available for this article. © RSNA, 2024.

Is it the Time to Move Towards Coronary Computed Tomography Angiography-Derived Fractional Flow Reserve Guided Percutaneous Coronary Intervention? The Pros and Cons

Coronary artery disease is the leading cause of mortality worldwide. Diagnosis is conventionally performed by direct visualization of the arteries by invasive coronary angiography (ICA), which has inherent limitations and risks. Measurement of fractional flow reserve (FFR) has been suggested for a more accurate assessment of ischemia in the coronary artery with high accuracy for determining the severity and decision on the necessity of intervention. Nevertheless, invasive coronary angiography-derived fractional flow reserve (ICA-FFR) is currently used in less than one-third of clinical practices because of the invasive nature of ICA and the need for additional equipment and experience, as well as the cost and extra time needed for the procedure. Recent technical advances have moved towards non-invasive high-quality imaging modalities, such as magnetic resonance, single-photon emission computed tomography, and coronary computed tomography (CT) scan; however, none had a definitive modality to confirm hemodynamically significant coronary artery stenosis. Coronary computed tomography angiography (CCTA) can provide accurate anatomic and hemodynamic data about the coronary lesion, especially calculating fractional flow reserve derived from CCTA (CCTA-FFR). Although growing evidence has been published regarding CCTA-FFR results being comparable to ICA-FFR, CCTA-FFR has not yet replaced the invasive conventional angiography, pending additional studies to validate the advantages and disadvantages of each diagnostic method. Furthermore, it has to be identified whether revascularization of a stenotic lesion is plausible based on CCTA-FFR and if the therapeutic plan can be determined safely and accurately without confirmation from invasive methods. Therefore, in the present review, we will outline the pros and cons of using CCTA-FFR vs. ICA-FFR regarding diagnostic accuracy and treatment decision-making.

Coronary CT angiography-derived fractional flow reserve in-stable angina: association with recurrent chest pain

AIMS

The aim of this study was to evaluate the association between coronary computed tomography angiography (CCTA)-derived fractional flow reserve (FFRCT) and recurrent chest pain (CP) at 1-year follow-up in patients with stable angina pectoris (SAP).

METHODS AND RESULTS

Study of patients (n = 267) with SAP who underwent CCTA and FFRCT testing; 236 (88%) underwent invasive coronary angiography; and 87 (33%) were revascularized. Symptomatic status at 1-year follow-up was gathered by a structured interview. Three different FFRCT algorithms were applied using the following criteria for abnormality: (i) 2 cm-FFRCT ≤0.80; (ii) d-FFRCT ≤0.80; and (iii) a combination in which both a d-FFRCT ≤0.80 and a ΔFFRCT ≥0.06 must be present in the same vessel (c-FFRCT). Patients were classified into two groups based on the FFRCT test result and revascularization: completely revascularized/normal (CRN), patients in whom all coronary arteries with an abnormal FFRCT test result were revascularized or patients with completely normal FFRCT test results, and incompletely revascularized (IR), patients in whom ≥1 coronary artery with an abnormal FFRCT test result was not revascularized. Recurrent CP was present in 62 (23%) patients. Classification of patients (CRN or IR) was significantly associated with recurrent CP for all applied FFRCT interpretation algorithms. When applying the c-FFRCT algorithm, the association with recurrent CP was found, irrespective of the extent of coronary calcification and the degree of coronary stenosis. A negative association between per-patient minimal d-FFRCT and recurrent CP was demonstrated, P < 0.005.

CONCLUSION

An abnormal FFRCT test result is associated with an increased risk of recurrent CP in patients with new-onset SAP.

Feasibility and Comparison of Resting Full-Cycle Ratio and Computed Tomography Fractional Flow Reserve in Patients with Severe Aortic Valve Stenosis

Background: Computed tomography derived Fractional Flow Reserve (CT-FFR) has been shown to decrease the referral rate for invasive coronary angiography (ICA). The purpose of the study was to evaluate the diagnostic performance of CT-FFR compared to hyperemia-free index Resting Full-cycle Ratio (RFR) in patients with relevant aortic stenosis (AS) and intermediate coronary stenosis. Methods: 41 patients with 46 coronary lesions underwent ICA with quantitative coronary angiography (QCA), pressure wire assessment and routine pre-transcatheter aortic valve replacement (TAVR) computed tomography (CT). CT-FFR analysis was performed using prototype on-site software. Results: RFR showed a significant correlation with CT-FFR (Pearson’s correlation, r = 0.632, p < 0.001). On a per-lesion basis, diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of CT-FFR were 82.6% (95% CI 68.6−92.2), 69.6% (95% CI 47.1−86.8), 95.7% (95% CI  78.1−99.9), 94.1% (95% CI 69.8−99.1), and 75.9% (95% CI 62.7−85.4), respectively. The optimal cutoff value of the CT-FFR for RFR ≤ 0.89 prediction was 0.815. The area under the receiver curve showed a larger area under the curve for CT-FFR (0.87; 95% CI 0.75−0.98) compared with CTA stenosis of ≥50% (0.54, 95% CI 0.38−0.71), CTA ≥ 70% (0.72, 95% CI 0.57−0.87) and QCA ≥ 50% (0.67, 95% CI 0.52−0.83). Conclusions: CT-FFR assessed by routine pre-TAVR CT is safe and feasible and shows a significant correlation with RFR in patients with AS. CT-FFR is superior to QCA ≥ 50%, CT ≥ 50% and CT ≥ 70% in assessing the hemodynamic relevance of intermediate coronary lesions. Thus, CT-FFR has the potential to guide revascularization in patients with AS.

One-year outcomes of CCTA alone versus machine learning-based FFRCT for coronary artery disease: a single-center, prospective study

OBJECTIVES

To explore downstream management and outcomes of machine learning (ML)-based CT derived fractional flow reserve (FFR_CT) strategy compared with an anatomical coronary computed tomography angiography (CCTA) alone assessment in participants with intermediate coronary artery stenosis.

METHODS

In this prospective study conducted from April 2018 to March 2019, participants were assigned to either the CCTA or FFR_CT group. The primary endpoint was the rate of invasive coronary angiography (ICA) that demonstrated non-obstructive disease at 90 days. Secondary endpoints included coronary revascularization and major adverse cardiovascular events (MACE) at 1-year follow-up.

RESULTS

In total, 567 participants were allocated to the CCTA group and 566 to the FFR_CT group. At 90 days, the rate of ICA without obstructive disease was higher in the CCTA group (33.3%, 39/117) than that (19.8%, 19/96) in the FFR_CT group (risk difference [RD] = 13.5%, 95% confidence interval [CI]: 8.4%, 18.6%; p = 0.03). The ICA referral rate was higher in the CCTA group (27.5%, 156/567) than in the FFR_CT group (20.3%, 115/566) (RD = 7.2%, 95% CI: 2.3%, 12.1%; p = 0.003). The revascularization-to-ICA ratio was lower in the CCTA group than that in the FFR_CT group (RD = 19.8%, 95% CI: 14.1%, 25.5%, p = 0.002). MACE was more common in the CCTA group than that in the FFR_CT group at 1 year (HR: 1.73; 95% CI: 1.01, 2.95; p = 0.04).

CONCLUSION

In patients with intermediate stenosis, the FFR_CT strategy appears to be associated with a lower rate of referral for ICA, ICA without obstructive disease, and 1-year MACE when compared to the anatomical CCTA alone strategy.

KEY POINTS

• In stable patients with intermediate stenosis, ML-based FFR_CT strategy was associated with a lower referral ICA rate, a lower normalcy rate of ICA, and higher revascularization-to-ICA ratio than the CCTA strategy. • Compared with the CCTA strategy, ML-based FFR_CTshows superior outcome prediction value which appears to be associated with a lower rate of 1-year MACE. • ML-based FFR_CT strategy as a non-invasive "one-stop-shop" modality may be the potential to change diagnostic workflows in patients with suspected coronary artery disease.

Additional value of deep learning computed tomographic angiography-based fractional flow reserve in detecting coronary stenosis and predicting outcomes

BACKGROUND

Deep learning (DL) has achieved great success in medical imaging and could be utilized for the non-invasive calculation of fractional flow reserve (FFR) from coronary computed tomographic angiography (CCTA) (CT-FFR).

PURPOSE

To examine the ability of a DL-based CT-FFR in detecting hemodynamic changes of stenosis.

MATERIAL AND METHODS

This study included 73 patients (85 vessels) who were suspected of coronary artery disease (CAD) and received CCTA followed by invasive FFR measurements within 90 days. The diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the receiver operating characteristics curve (AUC) were compared between CT-FFR and CCTA. Thirty-nine patients who received drug therapy instead of revascularization were followed for up to 31 months. Major adverse cardiac events (MACE), unstable angina, and rehospitalization were evaluated and compared between the study groups.

RESULTS

At the patient level, CT-FFR achieved 90.4%, 93.6%, 88.1%, 85.3%, and 94.9% in accuracy, sensitivity, specificity, PPV, and NPV, respectively. At the vessel level, CT-FFR achieved 91.8%, 93.9%, 90.4%, 86.1%, and 95.9%, respectively. CT-FFR exceeded CCTA in these measurements at both levels. The vessel-level AUC for CT-FFR also outperformed that for CCTA (0.957 vs. 0.599, P < 0.0001). Patients with CT-FFR ≤0.8 had higher rates of rehospitalization (hazard ratio [HR] 4.51, 95% confidence interval [CI] 1.08-18.9) and MACE (HR 7.26, 95% CI 0.88-59.8), as well as a lower rate of unstable angina (HR 0.46, 95% CI 0.07-2.91).

CONCLUSION

CT-FFR is superior to conventional CCTA in differentiating functional myocardial ischemia. In addition, it has the potential to differentiate prognoses of patients with CAD.

Real-world clinical and cost analysis of CT coronary angiography and CT coronary angiography-derived fractional flow reserve (FFRCT)-guided care in the National Health Service

AIM

To quantify the real-world clinical and cost impact of computed tomography (CT) coronary angiography (CTCA)-derived fractional flow reserve (FFR_CT) in the National Health Service (NHS).

MATERIALS AND METHODS

Consecutive clinical CTCA examinations from September to December 2018 with ≥1 stenosis of ≥25% underwent FFR_CT analysis. The Heart Team reviewed clinical data and CTCA findings, blinded to FFR_CT values, and documented hypothetical consensus management. FFR_CT results were then unblinded and hypothetical consensus management re-recorded. Diagnostic waiting times for management pathways were estimated. A per-patient cost analysis for diagnostic certainty regarding coronary artery disease (CAD) management was performed using 2014-2020 NHS tariffs for pre- and post-FFR_CT pathways.

RESULTS

Two hundred and fifty-one CTCAs were performed during the study period. Fifty-seven percent (145/251) had no CAD or stenosis <25%. One study was non-diagnostic. Of the remaining 42% (105/251), two were ineligible for FFR_CT and there was a 5% (5/103) failure rate. FFR_CT led to a change in hypothetical management in 65% (64/98; p<0.001) patients with a functional imaging test cancelled in 17% (17/98) and a diagnostic angiogram cancelled in 47% (46/98). FFR_CT-guided management had a reduced mean time to definitive investigation compared with CTCA alone (28 ± 4 versus 44 ± 4 days; p=0.004). Using the proposed 2020/21 tariff, CTCA + FFR_CT for stenosis ≥50% resulted in a diagnostic pathway £44.97 more expensive per patient than usual care without FFR_CT.

CONCLUSIONS

In the real-world NHS setting, FFR_CT-guided management has the potential to rationalise patient management, accelerate diagnostic pathways, and depending on the stenosis severity modelled, may be cost-effective.

Functional assessment of coronary plaques using CT based hemodynamic simulations: Current status, technical principles and clinical value

In recent years, coronary computed tomography angiography (CCTA) has emerged as an accurate and safe non-invasive imaging modality in terms of detecting and excluding coronary artery disease (CAD). In the latest European Society of Cardiology Guidelines CCTA received Class I recommendation for the evaluation of patients with stable chest pain with low to intermediate clinical likelihood of CAD. Despite its high negative predictive value, the diagnostic performance of CCTA is limited by the relatively low specificity, especially in patients with heavily calcified lesions. The discrepancy between the degree of stenosis and ischemia is well established based on both invasive and non-invasive tests. The rapid evolution of computational flow dynamics has allowed the simulation of CCTA derived fractional flow reserve (FFR-CT), which improves specificity by combining anatomic and functional information regarding coronary atherosclerosis. FFR-CT has been extensively validated against invasively measured FFR as the reference standard. Due to recent technological advancements FFR-CT values can also be calculated locally, without offsite processing. Wall shear stress (WSS) and axial plaque stress (APS) are additional key hemodynamic elements of atherosclerotic plaque characteristics, which can also be measured using CCTA images. Current evidence suggests that WSS and APS are important hemodynamic features of adverse coronary plaques. CCTA based hemodynamic calculations could therefore improve prognostication and the management of patients with stable CAD.

Prognostic value of noninvasive combined anatomic/functional assessment by cardiac CT in patients with suspected coronary artery disease - Comparison with invasive coronary angiography and nuclear myocardial perfusion imaging for the five-year-follow up of the CORE320 multicenter study

BACKGROUND

Few data exist on long-term outcome in patients undergoing combined coronary CT angiography (CTA) and myocardial CT perfusion imaging (CTP) as well as invasive coronary angiography (ICA) and single photon emission tomography (SPECT).

METHODS

At 16 centers, 381 patients were followed for major adverse cardiac events (MACE) for the CORE320 study. All patients underwent coronary CTA, CTP, and SPECT before ICA within 60 days. Prognostic performance according binary results (normal/abnormal) was assessed by 5-year major cardiovascular events (MACE) free survival and area under the receiver-operating-characteristic curve (AUC).

RESULTS

Follow up beyond 2-years was available in 323 patients. MACE-free survival rate was greater among patients with normal combined CTA-CTP findings compared to ICA-SPECT: 85 vs. 80% (95% confidence interval [CI] for difference 0.1, 11.3) though event-free survival time was similar (4.54 vs. 4.37 years, 95% CI for difference: -0.03, 0.36). Abnormal results by combined CTA-CTP was associated with 3.83 years event-free survival vs. 3.66 years after abnormal combined ICA-SPECT (95% CI for difference: -0.05, 0.39). Predicting MACE by AUC also was similar: 65 vs. 65 (difference 0.1; 95% CI -4.6, 4.9). When MACE was restricted to cardiovascular death, myocardial infarction, or stroke, AUC for CTA-CTP was 71 vs. 60 by ICA-SPECT (difference 11.2; 95% CI -1.0, 19.7).

CONCLUSIONS

Combined CTA-CTP evaluation yields at least equal 5-year prognostic information as combined ICA-SPECT assessment in patients presenting with suspected coronary artery disease. Noninvasive cardiac CT assessment may eliminate the need for diagnostic cardiac catheterization in many patients.

CLINICAL TRIAL REGISTRATION

NCT00934037.

Clinical application of computed tomography angiography and fractional flow reserve computed tomography in patients with coronary artery disease: A meta-analysis based on pre- and post-test probability

PURPOSE

To assess the diagnostic role of coronary computed tomography angiography (CCTA) and fractional flow reserve computed tomography (FFRCT) in confirming or excluding ischemic coronary artery disease (CAD) and to provide a rational use of CCTA and FFRCT in different pre-test probability (PTP) of CAD.

METHODS

We searched the electronic databases from the earliest relevant literature to July 2020 comparing FFRCT or CCTA with FFR. The bivariate random-effects models and Bayes' theorem were used to investigate the diagnostic performance of CCTA and FFRCT with the sensitivity, specificity, pre- and post-test probability.

RESULTS

Fifty-three articles with 4817 patients and 7026 vessels finally met our inclusion criteria. At the patient level, the sensitivity and specificity of CCTA were (0.94, 0.89-0.97), and (0.50, 0.43-0.58), respectively. For FFRCT, the sensitivity and specificity were (0.90, 0.87-0.93) and (0.81, 0.73-0.87). CCTA or FFRCT could increase the post-test probability to >85 % in patients with a PTP > 74.9 % or 54.5 %; CCTA or FFRCT could decrease the post-test probability to <15 % in patients with a pre-test probability <61.3 % or 59.3 %.

CONCLUSIONS

In patients with low to intermediate PTP, CCTA is suggested to exclude CAD, while the time-consuming calculation of FFRCT may be unnecessary. If CCTA detects significant or uncertain stenosis with intermediate to high PTP of CAD, further FFRCT is suggested. The advantages of FFRCT for guiding CAD treatment have sufficiently been demonstrated.

Prospective comparison of integrated on-site CT-fractional flow reserve and static CT perfusion with coronary CT angiography for detection of flow-limiting coronary stenosis

OBJECTIVES

To compare the diagnostic power of separately integrating on-site computed tomography (CT)-derived fractional flow reserve (CT-FFR) and static CT stress myocardial perfusion (CTP) with coronary computed tomography angiography (CCTA) in detecting patients with flow-limiting CAD. The flow-limiting stenosis was defined as obstructive (≥ 50%) stenosis by invasive coronary angiography (ICA) with a corresponding perfusion deficit on stress single photon emission computed tomography (SPECT/MPI).

METHODS

Forty-eight patients (74 vessels) were enrolled who underwent research-indicated combined CTA-CTP (320-row CT scanner, temporal resolution 137 ms) and SPECT/MPI prior to conventional coronary angiography. CT-FFR was computed on-site using resting CCTA data with dedicated workstation-based software. All five imaging modalities were analyzed in blinded independent core laboratories. Logistic regression and the integrated discrimination improvement (IDI) index were used to evaluate incremental differences in CT-FFR or CTP compared with CCTA alone.

RESULTS

The prevalence of obstructive CAD defined by combined ICA-SPECT/MPI was 40%. Per-vessel sensitivity and specificity were 95 and 42% for CCTA, 76 and 89% for CCTA + CTP, and 81 and 96% for CCTA + CT-FFR, respectively. The diagnostic performance of CCTA (AUC = 0.82) was improved by combining it with CT-FFR (AUC = 0.92, p = 0.01; IDI = 0.27, p < 0.001) or CTP (AUC = 0.90, p = 0.02; IDI = 0.18, p = 0.003).

CONCLUSION

On-site CT-FFR combined with CCTA provides an incremental diagnostic improvement over CCTA alone in identifying patients with flow-limiting CAD defined by ICA + SPECT/MPI, with a comparable diagnostic accuracy for integrated CTP and CCTA.

KEY POINTS

• Both on-site CT-FFR and CTP perform well with high diagnostic accuracy in the detection of flow-limiting stenosis. • Comparable diagnostic accuracy between CCTA + CT-FFR and CCTA + CTP is demonstrated to detect flow-limiting stenosis. • Integrated CT-FFR and CCTA derived from a single widened CCTA data acquisition can accurately and conveniently evaluate both coronary anatomy and physiology in the future management of patients with suspected CAD, without the need for additional vasodilator administration and contrast and radiation exposure.

Werden die Karten der CT-Koronarangiographie mit der FFRCT neu gemischt?

Die koronare Computertomographie-Angiographie (CCTA) besitzt, insbesondere aufgrund ihres hohen negativen prädiktiven Werts und der hohen Sensitivität, bereits einen hohen Stellenwert in der Primärdiagnostik der koronaren Herzkrankheit (KHK) bei allerdings limitierter Spezifität. Invasiv lässt sich die Spezifität der Herzkatheteruntersuchung (HKU) mit der „fractional flow reserve“ (FFR) mittels Nachweises der hämodynamischen Relevanz einer morphologisch nachgewiesenen Koronarstenose gut erhöhen. Neue, entweder auf „computational fluid dynamics“ (CFD) oder „machine learning“ (ML) basierende, nicht-invasive Methoden der FFR-Bestimmung in der CT (FFRCT) zeigen vielversprechende Ergebnisse. Die Möglichkeit des Einsatzes der CCTA wird aber v. a. von der Bildqualität und der Möglichkeit einer guten Segmentierung der Koronararterien bestimmt, die in 7–12 % der CCTA für die Anwendung der FFRCT nicht ausreicht, obwohl eine rein morphologische Beurteilung meist möglich ist. Beim Verschluss eines Koronargefäßes, z. B. zur Beurteilung des Kollateralflusses, kann die FFRCT ebenfalls nicht angewendet werden. Die FFRCT ist somit allein kein „game changer“ bei der Diagnose der chronischen KHK („chronic conorary syndrome“, CCS), sondern vielmehr ist es der ergänzende Einsatz zur CCTA bei nicht eindeutigen Fällen. Außerdem gibt es bisher nur einen kommerziellen Anbieter der FFRCT, bei dem die Analyse zeitlich verzögert („off-site“) erfolgt, was den akuten Nutzen bisher noch einschränkt. Es gibt allerdings auch On-site-Lösungen, die jedoch bisher nur für wissenschaftliche Zwecke und nicht klinisch eingesetzt werden dürfen. Eine sinnvolle Ergänzung zur rein morphologischen Beurteilung stellt die FFRCT aber auf jeden Fall dar. Wenn On-site-FFRCT-Lösungen auch kommerziell verfügbar sind, werden sie die Wertigkeit der CCTA im klinischen Alltag zur Primärdiagnostik des CCS in jedem Fall noch weiter erhöhen helfen.

13N-ammonia PET/CT stress myocardial blood flow compared to fractional flow reserve in coronary artery disease

AIM

In this retrospective study, fractional flow reserve was compared to stress myocardial blood flow derived by -ammonia (-NH3) myocardial perfusion PET/CT.

METHODS

From a large cohort of patients referred for -NH3 PET/CT, patients who also had fractional flow reserve-measurements within 6 months of the PET study were selected. These fractional flow reserve measurements were compared to PET/CT derived stress myocardial blood flow of the corresponding coronary territory. Results were categorized as concordant or discordant. Patients with discordant results were subdivided into a group with reduced fractional flow reserve but normal stress myocardial blood flow (group A) or into a group with normal fractional flow reserve but reduced stress myocardial blood flow (group B).

RESULTS

From September 2013 through July 2016, 46 patients examined with -NH3 PET/CT also had fractional flow reserve-measurements within 6 months. A total of 66 measurements were used for comparison. Discordance was found in 32% of the measurements. Group B showed a significant reduction in stress myocardial blood flow of all coronary territories compared to group A (P = 0.000). During follow-up (median 3.96 years), group B showed more visits to the emergency department and newly developed heart failure.

CONCLUSION

Discordance with stress myocardial blood flow in the corresponding flow territory was found in 32% of the fractional flow reserve-measurements. Patients with reduced stress myocardial blood flow but normal fractional flow reserve showed significantly reduced stress myocardial blood flow in all coronaries and a trend towards more cardiac adverse events.

Diagnostic Performance of On-Site Coronary CT Angiography-derived Fractional Flow Reserve Based on Patient-specific Lumped Parameter Models

Purpose

To evaluate the diagnostic performance of a prototype on-site coronary CT angiography-derived fractional flow reserve (CT FFR) algorithm, based on patient-specific lumped parameter models, for the detection of functionally significant stenosis defined by invasive FFR, and to compare the performance to anatomic evaluation of stenosis degree.

Materials and Methods

In this retrospective feasibility study, 77 vessels in 57 patients (42 of 57 [74%]) men; mean age, 58.5 years ± 9.2 [standard deviation]) who underwent clinically indicated coronary CT angiography within 60 days prior to an invasive FFR measurement were analyzed. Invasive FFR less than or equal to 0.80 was used to indicate a functionally significant stenosis. Diagnostic performance of CT FFR was evaluated and compared with evaluation of stenosis degree. Analysis was performed on a per-vessel basis.

Results

Invasive FFR revealed functionally significant stenoses in 37 vessels (48%). CT FFR showed a significantly increased ability to indicate functionally significant stenosis (area under the receiver operating characteristic curve [AUC], 0.87) compared with degree of stenosis at coronary CT angiography (AUC, 0.70; ΔAUC 0.17; P < .01). Using a cutoff of less than or equal to 0.80 for CT FFR and greater than or equal to 50% degree of stenosis at coronary CT angiography to indicate a significant stenosis, sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 33 of 37 (89.2%), 31 of 40 (77.5%), 33 of 42 (78.6%), 31 of 35 (88.6%), and 64 of 77 (83.1%), respectively, for CT FFR, and 33 of 37 (89.2%), 17 of 40 (42.5%), 33 of 56 (58.9%), 17 of 21 (81.0%), and 50 of 77 (64.9%), respectively, for degree of stenosis at coronary CT angiography.

Conclusion

Diagnostic performance of on-site CT FFR was superior to stenosis evaluation at coronary CT angiography for identification of functionally significant coronary artery stenosis in patients suspected of having or known to have coronary artery disease.© RSNA, 2019See also commentary by Schoepf et al.

Non-invasive fractional flow reserve derived from coronary computed tomography angiography in patients with acute chest pain: Subgroup analysis of the ROMICAT II trial

BACKGROUND

Non-invasive fractional flow reserve (FFR_CT) derived from coronary computed tomography angiography (CTA) permits hemodynamic evaluation of coronary stenosis and may improve efficiency of assessment in stable chest pain patients. We determined feasibility of FFR_CT in the population of acute chest pain patients and assessed the relationship of FFR_CT with outcomes of acute coronary syndrome (ACS) and revascularization and with plaque characteristics.

METHODS

We included 68 patients (mean age 55.8 ± 8.4 years, 71% men) from the ROMICAT II trial who had ≥50% stenosis on coronary CTA or underwent additional non-invasive stress test. We evaluated coronary stenosis and high-risk plaque on coronary CTA. FFR_CT was measured in a core laboratory.

RESULTS

We found correlation between anatomic severity of stenosis and FFR_CT ≤0.80 vs. FFR_CT >0.80 (severe stenosis 84.8% vs. 15.2%; moderate stenosis 33.3% vs. 66.7%; mild stenosis 33.3% vs. 66.7% patients). Patients with severe stenosis had lower FFR_CT values (median 0.64, 25th-75th percentile 0.50-0.75) as compared to patients with moderate (median 0.84, 25th-75th percentile, p < 0.001) or mild stenosis (median 0.86, 25th-75th percentile 0.78-0.88, p < 0.001). The relative risk of ACS and revascularization in patients with positive FFR_CT ≤0.80 was 4.03 (95% CI 1.56-10.36) and 3.50 (95% CI 1.12-10.96), respectively. FFR_CT ≤0.80 was associated with the presence of high-risk plaque (odds ratio 3.91, 95% CI 1.55-9.85, p = 0.004) after adjustment for stenosis severity.

CONCLUSION

Abnormal FFR_CT was associated with the presence of ACS, coronary revascularization, and high-risk plaque. FFR_CT measurements correlated with anatomic severity of stenosis on coronary CTA and were feasible in population of patients with acute chest pain.

Coronary computed tomography angiography equals invasive angiography for the prediction of coronary revascularization

INTRODUCTION

Growing role of coronary computed tomography angiography (CTA) as a diagnostic tool in patients with suspected coronary artery disease (CAD) calls for better recognition of its value in clinical decision making as compared to the gold standard of invasive coronary angiography (ICA).

AIM

To assess the diagnostic value of quantitative coronary computed tomography angiography (QCT) as compared to quantitative coronary angiography (QCA) for the prediction of coronary revascularization.

MATERIAL AND METHODS

In this prospective observational study we included 100 patients who underwent ICA following CTA. Quantitative diameter stenosis analysis (qCTA) was performed with Syngo.via (Siemens Medical Systems) software by an experienced investigator blinded to results of ICA. Quantitative Coronary Angiography (QCA) was chosen to define %DS in a repetitive manner. ICA images were submitted to Qangio XA (Medis, Leiden, The Netherlands) software for QCA analysis.

RESULTS

Eighty out of 400 analysed vessels were revascularized. Per-vessel diagnostic accuracy, sensitivity, specificity, PPV an NPV were 80%, 98%, 73%, 48% and 99% for QCT and 81%, 99%, 73%, 48% and 100% for QCA, respectively, for the prediction of revascularization. AUC was similar: 0.88 for QCT and 0.89 for QCA (p = NS).

CONCLUSIONS

These real-world data support the concept that CTA is as precise in prediction of coronary revascularization as ICA. This may add to the discussion about CTA having the potential to replace ICA for diagnosing vessels qualified for intervention, reserving the invasive diagnostic approach for those with the highest probability of revascularization.

Real-world clinical utility and impact on clinical decision-making of coronary computed tomography angiography-derived fractional flow reserve: lessons from the ADVANCE Registry

AIMS

Non-invasive assessment of stable chest pain patients is a critical determinant of resource utilization and clinical outcomes. Increasingly coronary computed tomography angiography (CCTA) with selective CCTA-derived fractional flow reserve (FFRCT) is being used. The ADVANCE Registry, is a large prospective examination of using a CCTA and FFRCT diagnostic pathway in real-world settings, with the aim of determining the impact of this pathway on decision-making, downstream invasive coronary angiography (ICA), revascularization, and major adverse cardiovascular events (MACE).

METHODS AND RESULTS

A total of 5083 patients with symptoms concerning for coronary artery disease (CAD) and atherosclerosis on CCTA were enrolled at 38 international sites from 15 July 2015 to 20 October 2017. Demographics, symptom status, CCTA and FFRCT findings, treatment plans, and 90 days outcomes were recorded. The primary endpoint of reclassification between core lab CCTA alone and CCTA plus FFRCT-based management plans occurred in 66.9% [confidence interval (CI): 64.8-67.6] of patients. Non-obstructive coronary disease was significantly lower in ICA patients with FFRCT ≤0.80 (14.4%) compared to patients with FFRCT >0.80 (43.8%, odds ratio 0.19, CI: 0.15-0.25, P < 0.001). In total, 72.3% of subjects undergoing ICA with FFRCT ≤0.80 were revascularized. No death/myocardial infarction (MI) occurred within 90 days in patients with FFRCT >0.80 (n = 1529), whereas 19 (0.6%) MACE [hazard ratio (HR) 19.75, CI: 1.19-326, P = 0.0008] and 14 (0.3%) death/MI (HR 14.68, CI 0.88-246, P = 0.039) occurred in subjects with an FFRCT ≤0.80.

CONCLUSIONS

In a large international multicentre population, FFRCT modified treatment recommendation in two-thirds of subjects as compared to CCTA alone, was associated with less negative ICA, predicted revascularization, and identified subjects at low risk of adverse events through 90 days.

ESTIMATION OF DIAGNOSTIC REFERENCE LEVELS FOR CT CORONAROGRAPHY IN SLOVAKIA

The coronary CT angiography (CCTA) is a frequent diagnostic method connected with large variability of effective dose. Therefore, it is the type of examination where optimization is very important and the use of a national diagnostic reference level (DRL) recommended. In Slovakia the DRL for interventional radiology examinations until now fails. The objective of our study was to propose the national DRL for CCTA examinations in Slovak Republic, on the basis of a cross-sectional multicenter study, performed in four departments of radiology. The study was realized in 2014-16 in a sample of 1725 patients undergoing CCTA examination. The proposed DRL expressed by CTDIVOL is 45 mGy and of DLP is 510 mGy cm.

Correlation of FFR-derived from CT and stress perfusion CMR with invasive FFR in intermediate-grade coronary artery stenosis

Only one-third of intermediate-grade coronary artery stenosis (i.e. 40-70% diameter narrowing) causes myocardial ischemia, requiring most often additional invasive work-up with invasive fractional flow reserve (FFR). To evaluate the correlations between FFR estimates derived from computed tomography (FFR_CT) and adenosine perfusion cardiac magnetic resonance (CMR) with invasive FFR in intermediate-grade stenosis. Thirty-seven patients (mean age 61 ± 9 years; 25 men) who underwent adenosine perfusion CMR, quantitative coronary angiography and FFR in the work-up for intermediate-grade stenoses (n = 39) diagnosed at coronary CT angiography were retrospectively evaluated. Blinded FFR_CT analysis was computed on each intermediate-grade lesion and correlated to the FFR values. On adenosine CMR, subendocardial time-enhancement maximal upslopes, normalized by respective left ventricle cavity upslopes, were obtained distal to a coronary stenosis (RISK area) and in remote myocardium (REMOTE area). The perfusion was subsequently assessed without (uncorrected RISK) and after correction for remote perfusion (relative myocardial perfusion index = REMOTE/RISK ratio), and then correlated to the FFR values. Differences in correlations were tested with z statistics and considered statistically significant different at a p < 0.05 level. The average FFR value was 0.85 ± 0.10 (0.60-0.98 range), 28% (n = 11) was ≤ 0.80. FFR value correlated poorly with uncorrected RISK upslopes (r = 0.151; p = 0.36), but equally strongly with FFR_CT (r = 0.675; p < 0.001) and the relative myocardial perfusion index (r = - 0.63) (p < 0.001; z = 6.72) for assessment of lesion-specific ischemia. Both FFR_CT and adenosine perfusion CMR strongly correlate with invasive FFR measurements for intermediate-grade stenosis. These preliminary findings pave the way for further studies evaluating non-invasively intermediate coronary stenosis in clinical practice.

Coronary CTA enhanced with CTA based FFR analysis provides higher diagnostic value than invasive coronary angiography in patients with intermediate coronary stenosis

BACKGROUND

CTA based FFR, a software based application, enhances diagnostic value of coronary computed tomography angiography (CTA) examination. However it remains unknown whether it improves accuracy over the gold standard of invasive coronary angiography (ICA) in predicting functionally significant coronary stenosis. The aim of our study was to compare diagnostic accuracies of coronary CTA, CTA based FFR, and ICA, with invasive FFR as the reference standard in patients with intermediate stenosis on CTA.

METHODS

96 intermediate stenoses (50-90%) from 90 subjects, with intermediate pre-test probability of CAD, who underwent coronary CTA were analyzed. Each patient had subsequent ICA with FFR. CTA based FFR (cFFR v2.1, Siemens) analysis was performed on-site. The stenoses with invasive FFR≤0.8 were considered hemodynamically significant.

RESULTS

41/96 stenoses were hemodynamically significant (FFR≤0.8). While the area under ROC curves (AUC) for identification of significant stenosis evaluated on QCA (0.653), visual ICA (0.652), qCTA (0.690) and visual CTA (0.660) did not significantly differ, the AUC for CTA based FFR (0.835) was significantly higher (p = 0.004, p = 0.004, p = 0.010, p = 0.007, respectively). The accuracies of CTA based FFR, qCTA and QCA were 76%, 63% and 58% respectively.

CONCLUSION

Our results suggest that diagnostic potential of routine coronary CTA, augmented with CTA based FFR analysis, is superior to ICA in patients with intermediate stenosis.

Myocardial Assessment with Cardiac CT: Ischemic Heart Disease and Beyond

PURPOSE OF REVIEW

The aim of this review is to highlight recent advancements, current trends, and the expanding role for cardiac CT (CCT) in the evaluation of ischemic heart disease, nonischemic cardiomyopathies, and some specific congenital myocardial disease states.

RECENT FINDINGS

CCT is a highly versatile imaging modality for the assessment of numerous cardiovascular disease states. Coronary CT angiography (CCTA) is now a well-established first-line imaging modality for the exclusion of significant coronary artery disease (CAD); however, CCTA has modest positive predictive value and specificity for diagnosing obstructive CAD in addition to limited capability to evaluate myocardial tissue characteristics.

SUMMARY

CTP, when combined with CCTA, presents the potential for full functional and anatomic assessment with a single modality. CCT is a useful adjunct in select patients to both TTE and CMR in the evaluation of ventricular volumes and systolic function. Newer applications, such as dynamic CTP and DECT, are promising diagnostic tools offering the possibility of more quantitative assessment of ischemia. The superior spatial resolution and volumetric acquisition of CCT has an important role in the diagnosis of other nonischemic causes of cardiomyopathies.

In vitro validation of coronary CT angiography for the evaluation of complex lesions

AIMS

The aim of this study was to assess in vitro the diagnostic accuracy of computed tomography angiography (CTA) for the evaluation of complex coronary lesions.

METHODS AND RESULTS

Five Plexiglas phantoms with three bifurcation lesions each were designed to mimic the anatomic variations and fractal phenomena of the coronary tree. In addition, luminal stenoses were scaled up with increases of 10% from 40% to 80%, corresponding to luminal areas ranging from 3.0 mm2 to 0.22 mm2. Third-generation dual-source computed tomography was used. Automated quantitative CTA analysis was performed according to the bifurcation segment model. The primary objective was to determine the diagnostic accuracy of quantitative CTA in assessing bifurcation lesions with the phantoms as a reference. The accuracy of CTA for the assessment of minimal luminal diameter was -0.07 mm (limits of agreement -0.75 to 0.61), for reference vessel diameter 0.19 mm (limits of agreement -0.25 to 0.63) and diameter stenosis 8.2% (limits of agreement -13.2 to 29.5) with no difference regarding the location within the bifurcation (i.e., proximal and distal main vessel and side branch). In stenosis with minimal luminal diameter ≥1 mm, CTA overestimated the lesion severity (bias 0.19 mm, limits of agreement -0.09 to 0.47), whereas in lesions with severe stenosis and minimal luminal diameter ≤1 mm, CTA underestimated the lesion severity (bias -0.48 mm, limits of agreement -0.55 to -0.41). CTA was able to identify the contrast-filled lumen in all degrees of lesion severity.

CONCLUSIONS

In vitro, CTA is accurate for the evaluation of bifurcation lesions. CTA was able to distinguish contrast-filled lumen even in severe obstructive lesions. These findings require further validation in the clinical setting.

Cardiac-Specific Conversion Factors to Estimate Radiation Effective Dose From Dose-Length Product in Computed Tomography

OBJECTIVES

This study sought to determine updated conversion factors (k-factors) that would enable accurate estimation of radiation effective dose (ED) for coronary computed tomography angiography (CTA) and calcium scoring performed on 12 contemporary scanner models and current clinical cardiac protocols and to compare these methods to the standard chest k-factor of 0.014 mSv·mGy-1cm-1.

BACKGROUND

Accurate estimation of ED from cardiac CT scans is essential to meaningfully compare the benefits and risks of different cardiac imaging strategies and optimize test and protocol selection. Presently, ED from cardiac CT is generally estimated by multiplying a scanner-reported parameter, the dose-length product, by a k-factor which was determined for noncardiac chest CT, using single-slice scanners and a superseded definition of ED.

METHODS

Metal-oxide-semiconductor field-effect transistor radiation detectors were positioned in organs of anthropomorphic phantoms, which were scanned using all cardiac protocols, 120 clinical protocols in total, on 12 CT scanners representing the spectrum of scanners from 5 manufacturers (GE, Hitachi, Philips, Siemens, Toshiba). Organ doses were determined for each protocol, and ED was calculated as defined in International Commission on Radiological Protection Publication 103. Effective doses and scanner-reported dose-length products were used to determine k-factors for each scanner model and protocol.

RESULTS

k-Factors averaged 0.026 mSv·mGy-1cm-1 (95% confidence interval: 0.0258 to 0.0266) and ranged between 0.020 and 0.035 mSv·mGy-1cm-1. The standard chest k-factor underestimates ED by an average of 46%, ranging from 30% to 60%, depending on scanner, mode, and tube potential. Factors were higher for prospective axial versus retrospective helical scan modes, calcium scoring versus coronary CTA, and higher (100 to 120 kV) versus lower (80 kV) tube potential and varied among scanner models (range of average k-factors: 0.0229 to 0.0277 mSv·mGy-1cm-1).

CONCLUSIONS

Cardiac k-factors for all scanners and protocols are considerably higher than the k-factor currently used to estimate ED of cardiac CT studies, suggesting that radiation doses from cardiac CT have been significantly and systematically underestimated. Using cardiac-specific factors can more accurately inform the benefit-risk calculus of cardiac-imaging strategies.

Experience With an On-Site Coronary Computed Tomography-Derived Fractional Flow Reserve Algorithm for the Assessment of Intermediate Coronary Stenoses

Fractional flow reserve (FFR) derived from coronary computed tomography angiography (CTA) is a new technique for the diagnosis of ischemic coronary artery stenoses. The aim of this prospective study was to evaluate the diagnostic performance of a novel on-site computed tomography-based fractional flow reserve algorithm (CT-FFR) compared with invasive FFR as the gold standard, and to determine whether its diagnostic performance is affected by interobserver variations in lumen segmentation. We enrolled 44 consecutive patients (64.6 ± 8.9 years, 34% female) with 60 coronary atherosclerotic lesions who underwent coronary CTA and invasive coronary angiography in 2 centers. An FFR value ≤0.8 was considered significant. Coronary CTA scans were evaluated by 2 expert readers, who manually adjusted the semiautomated coronary lumen segmentations for effective diameter stenosis (EDS) assessment and on-site CT-FFR simulation. The mean CT-FFR value was 0.77 ± 0.15, whereas the mean EDS was 43.6 ± 16.9%. The sensitivity, specificity, positive predictive value, and negative predictive value of CT-FFR versus EDS with a cutoff of 50% were the following: 91%, 72%, 63%, and 93% versus 52%, 87%, 69%, and 77%, respectively. The on-site CT-FFR demonstrated significantly better diagnostic performance compared with EDS (area under the curve 0.89 vs 0.74, respectively, p <0.001). The CT-FFR areas under the curve of the 2 readers did not show any significant difference (0.89 vs 0.88, p = 0.74). In conclusion, on-site CT-FFR simulation is feasible and has better diagnostic performance than anatomic stenosis assessment. Furthermore, the diagnostic performance of the on-site CT-FFR simulation algorithm does not depend on the readers' semiautomated lumen segmentation adjustments.

Diagnostic Accuracy of Coronary CT Angiography for the Evaluation of Bioresorbable Vascular Scaffolds

OBJECTIVES

The purpose of this study was to assess the diagnostic accuracy of coronary computed tomography angiography (CTA) for bioresorbable vascular scaffold (BVS) evaluation.

BACKGROUND

Coronary CTA has emerged as a noninvasive method to evaluate patients with suspected or established coronary artery disease. The diagnostic accuracy of coronary CTA to evaluate angiographic outcomes after BVS implantation has not been well established.

METHODS

In the ABSORB II (A Bioresorbable Everolimus-Eluting Scaffold Versus a Metallic Everolimus-Eluting Stent II) study, patients were randomized either to receive treatment with the BVS or everolimus-eluting metallic stent. At the 3-year follow-up, 238 patients (258 lesions) treated with BVS underwent coronary angiography with intravascular ultrasound (IVUS) evaluation and coronary CTA. The diagnostic accuracy of coronary CTA was assessed by the area under the receiver-operating characteristic curve with coronary angiography and IVUS as references.

RESULTS

The mean difference in coronary CTA-derived minimal luminal diameter was -0.14 mm (limits of agreement -0.88 to 0.60) with quantitative coronary angiography as reference, whereas the mean difference in minimal lumen area was 0.73 mm² (limits of agreement -1.85 to 3.30) with IVUS as reference. The per-scaffold diagnostic accuracy of coronary CTA for detecting stenosis based on coronary angiography diameter stenosis of ≥50% revealed an area under the receiver-operating characteristic curve of 0.88 (95% confidence interval [CI]: 0.82 to 0.92) with a sensitivity of 80% (95% CI: 28% to 99%) and a specificity of 100% (95% CI: 98% to 100%), whereas diagnostic accuracy based on IVUS minimal lumen area ≤2.5 mm² showed an area under the receiver-operating characteristic curve of 0.83 (95% CI: 0.77 to 0.88) with a sensitivity of 71% (95% CI: 44% to 90%) and a specificity of 82% (95% CI: 75% to 87%). The diagnostic accuracy of coronary CTA was similar to coronary angiography in its ability to identify patients with a significant lesion based on the IVUS criteria (p = 0.75).

CONCLUSIONS

Coronary CTA has good diagnostic accuracy to detect in-scaffold luminal obstruction and to assess luminal dimensions after BVS implantation. Coronary angiography and coronary CTA yielded similar diagnostic accuracy to identify the presence and severity of obstructive disease. Coronary CTA might become the method of choice for the evaluation of patients treated with BVS.

Bridging the gap for lipid lowering therapy: plaque regression, coronary computed tomographic angiography, and imaging-guided personalized medicine

INTRODUCTION

Lipid-lowering therapy effectively decreases cardiovascular risk on a population level, but it remains difficult to identify an individual patient's personal risk reduction while following guideline directed medical therapy, leading to overtreatment in some patients and cardiovascular events in others. Recent improvements in cardiac CT technology provide the ability to directly assess an individual's atherosclerotic disease burden, which has the potential to personalize risk assessment for lipid-lowering therapy. Areas covered: We review the current unmet need in identifying patients at elevated residual risk despite guideline directed medical therapy, the evidence behind plaque regression as a potential marker of therapeutic response, and highlight state-of-the-art advances in coronary computed tomographic angiography (CCTA) for measurement of quantitative and qualitative changes in coronary atherosclerosis over time. Literature search was performed using PubMed and Google Scholar for literature relevant to statin therapy and residual risk, coronary plaque regression measurement, and CCTA assessment of quantitative and qualitative change in coronary atherosclerosis. Expert commentary: We discuss the potential ability of CCTA to guide lipid-lowering therapy as a bridge between population and personalized medicine in the future, as well as the potential barriers to its use.

Outcomes of anatomical vs. functional testing for coronary artery disease : Lessons from the PROMISE trial

The development of coronary artery disease (CAD) is a major, final common pathway in heart disease worldwide. With a rise in stress testing and increased scrutiny on cost-effectiveness and radiation exposure in medical imaging, a focus on the relative merits of anatomic versus functional characterization of CAD has emerged. In this context, coronary computed tomography angiography (CCTA) is a noninvasive alternative to functional testing as a first-line test for CAD detection but is complimentary in its nature. Here, we discuss the design, results, and implications of the PROMISE trial, a randomized comparative effectiveness study of 10,003 patients across 193 sites in the United States and Canada comparing the prognostic and diagnostic power of CCTA and standard stress testing. Specifically, we discuss the safety (e. g., contrast, radiation exposure) of CCTA versus functional testing in CAD, the need for improved selection for noninvasive testing, the frequency of downstream testing after anatomic or functional imaging, the use of imaging results in clinical management, and novel modalities of CAD risk determination using CCTA. PROMISE demonstrated that in a real-world, low-to-intermediate risk patient population referred to noninvasive testing for CAD, both CCTA and functional testing approaches have similar clinical, economic, and safety-based outcomes. We conclude with open questions in CAD imaging, specifically as they pertain to the utilization of CCTA.

Noninvasive FFR Derived From Coronary CT Angiography: Management and Outcomes in the PROMISE Trial

OBJECTIVES

The purpose of this study was to determine whether noninvasive fractional flow reserve derived from computed tomography (FFR_CT) predicts coronary revascularization and outcomes and whether its addition improves efficiency of referral to invasive coronary angiography (ICA) after coronary computed tomography angiography (CTA).

BACKGROUND

FFR_CT may improve the efficiency of an anatomic CTA strategy for stable chest pain.

METHODS

This observational cohort study included patients with stable chest pain in the PROMISE (PROspective Multicenter Imaging Study for Evaluation of Chest Pain) trial referred to ICA within 90 days after CTA. FFR_CT was measured at a blinded core laboratory, and FFR_CT results were unavailable to caregivers. We determined the agreement of FFR_CT (positive if ≤0.80) with stenosis on CTA and ICA (positive if ≥50% left main or ≥70% other coronary artery), and predictive value for a composite of coronary revascularization or major adverse cardiac events (death, myocardial infarction, or unstable angina). We retrospectively assessed whether adding FFR_CT ≤0.80 as a gatekeeper could improve efficiency of referral to ICA, defined as decreased rate of ICA without ≥50% stenosis and increased ICA leading to revascularization.

RESULTS

FFR_CT was calculated in 67% (181 of 271) of eligible patients (mean age 62 years; 36% women). FFR_CT was discordant with stenosis in 31% (57 of 181) for CTA and 29% (52 of 181) for ICA. Most patients undergoing coronary revascularization had an FFR_CT of ≤0.80 (91%; 80 of 88). An FFR_CT of ≤0.80 was a significantly better predictor for revascularization or major adverse cardiac events than severe CTA stenosis (HR: 4.3 [95% confidence interval [CI]: 2.4 to 8.9] vs. 2.9 [95% CI: 1.8 to 5.1]; p = 0.033). Reserving ICA for patients with an FFR_CT of ≤0.80 could decrease ICA without ≥50% stenosis by 44%, and increase the proportion of ICA leading to revascularization by 24%.

CONCLUSIONS

In this hypothesis-generating study of patients with stable chest pain referred to ICA from CTA, an FFR_CT of ≤0.80 was a better predictor of revascularization or major adverse cardiac events than severe stenosis on CTA. Adding FFR_CT may improve efficiency of referral to ICA from CTA alone.

Infarct characterization using CT

Myocardial infarction (MI) is a major cause of death and disability worldwide. The incidence is not expected to diminish, despite better prevention, diagnosis and treatment, because of the ageing population in industrialized countries and unhealthy lifestyles in developing countries. Nowadays it is highly requested an imaging tool able to evaluate MI and viability. Technology improvements determined an expansion of clinical indications from coronary plaque evaluation to functional applications (perfusion, ischemia and viability after MI) integrating additional phases and information in the mainstream examination. Cardiac computed tomography (CCT) and cardiac MR (CMR) employ different contrast media, but may characterize MI with overlapping imaging findings due to the similar kinetics and tissue distribution of gadolinium and iodinated contrast media. CCT may detect first-pass perfusion defects, dynamic perfusion after pharmacological stress, and delayed enhancement (DE) of non-viable territories.

A systematic review of imaging anatomy in predicting functional significance of coronary stenoses determined by fractional flow reserve

Fractional flow reserve (FFR) is the current gold standard to assess the physiological significance of coronary stenoses. With the development of coronary imaging techniques, several anatomic parameters have been investigated in vivo and their associations with FFR have been studied. The aim of this review is to summarize the accuracy of anatomic parameters derived by the present coronary imaging techniques including invasive coronary angiography, coronary computed tomography angiography, intravascular ultrasound and optical coherence tomography, in predicting a significant FFR. The impact of patient characteristics, lesion locations, variability of FFR and imaging resolution on the predictive ability are discussed.