Diagnostic Performance of CT-Derived Fractional Flow Reserve in Australian Patients Referred for Invasive Coronary Angiography

BACKGROUND

Non-invasive computed tomography (CT)-derived fractional flow reserve (FFR_CT) is computed from standard coronary CT angiography (CTA) datasets and provides accurate vessel-specific ischaemia assessment of coronary artery disease (CAD). To date, the technique and its diagnostic performance has not been verified in the Australian clinical context. The aim of this study was to describe and compare the diagnostic performance of FFR_CT and CTA for the detection of vessel-specific ischaemia as determined by invasive fractional flow reserve (FFR) in the Australian patient population.

METHODS

One-hundred-and-nine patients (219 vessels) referred for clinically mandated invasive angiography were retrospectively assessed. Each patient underwent research mandated CTA and FFR_CT within 3 months of invasive angiography and invasive FFR assessment. Independent core laboratory assessments were made to determine visual CTA stenosis, FFR_CT and invasive FFR values. FFR_CT values were matched with the corresponding invasive FFR measurement taken at the given wire position. Visual CTA stenosis ≥50%, FFR_CT values ≤0.8 and invasive FFR values ≤0.8 were considered significant for ischaemia.

RESULTS

Per vessel accuracy, sensitivity, specificity, positive predictive value and negative predictive value of FFR_CT were 80.4%, 80.0%, 80.6%, 64.9% and 90.0% respectively. Corresponding values for CTA were 75.1%, 87.1%, 69.2%, 58.1% and 91.7% respectively. In receiver operating characteristic curve analysis, FFR_CT demonstrated superior area under the curve (AUC) compared with CTA in both per vessel (0.87 vs 0.77, p=0.004) and per patient analysis (0.86 vs 0.74, p=0.011). Per vessel AUC of combined CTA and FFR_CT was superior to CTA alone (0.89 vs 0.77, p<0.0001).

CONCLUSION

In this cohort of Australian patients, the diagnostic performance of FFR_CT was found to be comparable to existing international literature, with demonstrated improvement in performance compared with CTA alone for the detection of vessel-specific ischaemia.

Influence of operator expertise and coronary luminal segmentation technique on diagnostic performance, precision and reproducibility of reduced-order CT-derived fractional flow reserve technique

BACKGROUND

Onsite workstation-based CT-derived Fractional-Flow-Reserve (CT-FFR) is accurate in assessing hemodynamic-significance of coronary stenoses. We aim to describe the influence of operator expertise and luminal-segmentation technique on the diagnostic performance, precision and reproducibility of CT-FFR in identifying hemodynamically-significant stenosis (FFR≤0.8).

METHODS

Forty-eight consecutive stable-patients (86 vessels) with suspected CAD underwent research indicated invasive-FFR and 320-detector CT-coronary-angiography (CTA). CT-FFR was derived using reduced-order model on standard desktop-computer. Semi-automated coronary luminal segmentation was performed using focused-technique with manual adjustments at regions of stenosis and calcification or comprehensive-technique with manual adjustments along the entire course of the vessel. CT-FFR analysis was performed using 3 blinded operators; core-laboratory engineer using focused-technique and radiographer and cardiologist using the comprehensive-technique. Diagnostic performance was assessed by area under receiver-operating-curve (AUC). Precision with invasive FFR was determined by Bland-Altman analysis, and reproducibility by intraclass-correlation-coefficient (ICC).

RESULTS

Diagnostic performance was comparable among operators (Engineer: AUC = 0.88, Radiographer 0.84; Cardiologist 0.87; P = 0.59). Coronary luminal-segmentation time was shortest using focused technique (engineer 6:17 ± 2.43 min), compared with comprehensive technique (cardiologist 14.83 ± 7.09, radiographer 24.74 ± 12.65; P < 0.001). Use of focused technique was associated with widest limits of agreement (LOA) with FFR and moderate intra-operator reproducibility (engineer LOA -0.20-0.33; ICC 0.66), when compared with the comprehensive technique which demonstrated narrower LOA and excellent reproducibility [radiographer (LOA -0.17-0.20, ICC = 0.91) and cardiologist (LOA-0.15-0.23, ICC = -0.93)] CONCLUSION: A workstation-based CT-FFR technique was reproducible with high and comparable diagnostic performance among operators with different expertise. A comprehensive luminal segmentation technique was the most time-consuming and associated with the highest reproducibility and precision with FFR.

Non-invasive CT-derived fractional flow reserve and static rest and stress CT myocardial perfusion imaging for detection of haemodynamically significant coronary stenosis

Computed tomography derived fractional flow reserve (FFR_CT) and computed tomography stress myocardial perfusion imaging (CTP) are techniques to assess haemodynamic significance of coronary stenosis. To compare the diagnostic performance of FFR_CT and static rest/stress CTP in detecting fractional flow reserve (FFR) defined haemodynamically-significant stenosis (FFR ≤ 0.8). Fifty-one patients (96 vessels) with suspected coronary artery disease from a single institution planned for elective invasive-angiography prospectively underwent research indicated 320-detector-CT-coronary-angiography (CTA) and adenosine-stress CTP and invasive FFR. Analyses were performed in separate core-laboratories for FFR_CT and CTP blinded to FFR results. Myocardial perfusion was assessed visually and semi-quantitatively by transmural perfusion ratio (TPR). Invasive FFR ≤ 0.8 was present in 33% of vessels and 49% of patients. FFR_CT, visual CTP and TPR analysis was feasible in 96%, 92% and 92% of patients respectively. Overall per-vessel sensitivity, specificity and diagnostic accuracy for FFR_CT were 81%, 85%, 84%, for visual CTP were 50%, 89%, 75% and for TPR were 69%, 48%, 56% respectively. Receiver-operating-characteristics curve analysis demonstrated larger per vessel area-under-curve (AUC) for FFR_CT (0.89) compared with visual CTP (0.70; p < 0.001), TPR (0.58; p < 0.001) and CTA (0.70; p = 0.0007); AUC for CTA + FFR_CT (0.91) was higher than CTA + visual CTP (0.77, p = 0.008) and CTA + TPR (0.74, p < 0.001). Per-patient AUC for FFR_CT (0.90) was higher than visual CTP (0.69; p = 0.0016), TPR (0.56; p < 0.0001) and CTA (0.68; p = 0.001). Based on this selected cohort of patients FFR_CT is superior to visually and semi-quantitatively assessed static rest/stress CTP in detecting haemodynamically-significant coronary stenosis as determined on invasive FFR.

Prognostic Value and Risk Continuum of Noninvasive Fractional Flow Reserve Derived from Coronary CT Angiography

Background Coronary CT angiography with noninvasive fractional flow reserve (FFR) predicts lesion-specific ischemia when compared with invasive FFR. The longer term prognostic value of CT-derived FFR (FFR_CT) is unknown. Purpose To determine the prognostic value of FFR_CT when compared with coronary CT angiography and describe the relationship of the numeric value of FFR_CT with outcomes. Materials and Methods This prospective subanalysis of the NXT study (Clinicaltrials.gov: NCT01757678) evaluated participants suspected of having stable coronary artery disease who were referred for invasive angiography and who underwent FFR, coronary CT angiography, and FFR_CT. The incidence of the composite primary end point of death, myocardial infarction, and any revascularization and the composite secondary end point of major adverse cardiac events (MACE: cardiac death, myocardial infarction, unplanned revascularization) were compared for an FFR_CT of 0.8 or less versus stenosis of 50% or greater on coronary CT angiograms, with treating physicians blinded to the FFR_CT result. Results Long-term outcomes were obtained in 206 individuals (age, 64 years ± 9.5), including 64% men. At median follow-up of 4.7 years, there were no cardiac deaths or myocardial infarctions in participants with normal FFR_CT. The incidence of the primary end point was more frequent in participants with positive FFR_CT compared with clinically significant stenosis at coronary CT angiography (73.4% [80 of 109] vs 48.7% [91 of 187], respectively; P < .001), with the majority of outcomes being planned revascularization. Corresponding hazard ratios (HRs) were 9.2 (95% confidence interval [CI]: 5.1, 17; P < .001) for FFR_CT and 5.9 (95% CI: 1.5, 24; P = .01) for coronary CT angiography. FFR_CT was a superior predictor compared with coronary CT angiography for primary end point (C-index FFR_CT, 0.76 vs coronary CT angiography, 0.54; P < .001) and MACE (FFR_CT, 0.71 vs coronary CT angiography, 0.52; P = .001). Frequency of MACE was higher in participants with positive FFR_CT compared with coronary CT angiography (15.6% [17 of 109] vs 10.2% [19 of 187], respectively; P = .02), driven by unplanned revascularization. MACE HR was 5.5 (95% CI: 1.6, 19; P = .006) for FFR_CT and 2.0 (95% CI: 0.3, 14; P = .46) for coronary CT angiography. Each 0.05-unit FFR_CT reduction was independently associated with greater incidence of primary end point (HR, 1.7; 95% CI: 1.4, 1.9; P < .001) and MACE (HR, 1.4; 95% CI: 1.1, 1.8; P < .001). Conclusion In stable patients referred for invasive angiography, a CT-derived fractional flow reserve (FFR_CT) value of 0.8 or less was a predictor of long-term outcomes driven by planned and unplanned revascularization and was superior to clinically significant stenosis on coronary CT angiograms. Additionally, the numeric value of FFR_CT was an independent predictor of outcomes. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Dennie and Rubens in this issue.

Impact of heart rate on diagnostic accuracy of second generation 320-detector computed tomography coronary angiography

OBJECTIVE

To assess the impact of elevated heart rate (HR) on the diagnostic accuracy and image quality of second-generation 320-detector computed tomography coronary angiography (320-CTCA).

METHODS

Consecutive patients with suspected coronary disease referred for invasive coronary angiography (ICA) were prospectively recruited and underwent 320-CTCA. Pre-scan beta-blockers were administered if native HR>80 bpm and post-scan cohorts stratified by traditional (HR ≤60 bpm) and elevated HR (61-80 bpm). A wider phase window was used for the elevated HR group (30-80%). 320-CTCA and ICA were analyzed by independent readers blinded to other data. Significant disease was defined as ≥50% visual stenosis on ICA. Uninterpretable segments by 320-CTCA were considered to be significant on an intention-to-diagnose principle. Image quality was assessed by 5-point Likert score.

RESULTS

Of 107 patients studied (1,662 segments), there was no significant difference in sensitivity, specificity, positive and negative predictive value between patients with HR ≤60 bpm (n=55) vs. HR 61-80 bpm (n=52): 97%, 88%, 95%, 94% vs. 100%, 88%, 95%, 100%; Receiver operator characteristic-area under the curve 0.93 vs. 0.94, P=0.82). Overall per-patient diagnostic accuracy was 96% in both groups with no significant difference in interpretable segments (Likert ≥2) or median radiation dose (2.4 mSv vs. 2.7 mSv, P=0.35). Only 4/1,662 (0.2%) segments were uninterpretable by motion artefact in the whole cohort.

CONCLUSIONS

In patients with HR >60 and up to 80bpm, second generation 320-CTCA provides comparably adequate diagnostic accuracy to HR ≤60 without significantly impacting upon overall segmental evaluability.

Ethnic differences in coronary plaque and epicardial fat volume quantified using computed tomography

Epidemiological studies observed a higher prevalence of coronary atherosclerosis in South Asians when compared to Caucasians, but quantitative computed tomography differences in aggregate plaque volume (APV) and epicardial fat volume (EFV) between South Asians, Southeast or East Asians (SEEAs) and Caucasians remain unknown. We aimed to compare APV and EFV quantified on computed-tomographic-coronary-angiography (CTCA) between South Asian, SEEA and Caucasian populations residing in Australia. Age, gender and body-mass-index matched subjects from three ethnic groups who underwent clinically indicated 320-detector CTCA were retrospectively analysed. Percentage APV in the first 5 cm of the left anterior descending artery (LAD) and EFV were quantified using dedicated software (Vital Images, USA). One-hundred-and-fifty subjects (average age = 57.7 years, 56 % male, n = 50 in each ethnic group) were analysed. Mean LAD percentage APV was highest in South Asians (44.5 ± 8.4 % vs. 37.5 ± 6.5 % in SEEAs and 39.5 ± 6.4 % in Caucasians, P = 0.00001). South Asian ethnicity predicted LAD APV above traditional risk factors on multivariate analysis (P = 0.000002). EFV was significantly higher in both South Asians (103.2 ± 41.7 cm³ vs. 85.8 ± 39.4 cm³, P = 0.035) and SEEAs (110.8 ± 36.9 cm³ vs. 85.8 ± 39.4 cm³, P = 0.001) when compared with Caucasians. In this cohort LAD percentage APV and EFV, as quantified on CTCA, differs between South Asians, SEEA and Caucasian populations, with higher LAD APV observed in South Asians and lower EFV in Caucasians. Atherosclerotic volume in LAD was best predicted by South Asian ethnicity above traditional risk factors and EFV. Further research is required to establish whether APV and EFV quantification can improve cardiac risk prediction in the South Asian population.

Clinical utility of multi-detector cardiac computed tomography in structural heart interventions

In recent years, there have been major advances in structural interventional cardiology, which have revolutionized the practice of cardiology. Appropriate selection and follow-up of patients undergoing these structural heart interventions is vital. Multi-detector computed tomography (MDCT) has emerged as a key imaging modality in the peri-procedural assessment of patients undergoing multiple structural cardiac interventions. The purpose of this review is to provide an evidence-based clinical update on the roles of MDCT in both established and evolving structural heart interventions, including transcatheter aortic valve replacement (TAVR) and transcatheter mitral valve implantation (TMVI). The utility of MDCT in the peri-procedural assessment of patients undergoing pulmonary vein isolation (PVI) for atrial fibrillation, cardiac resynchronization therapy (CRT) and left atrial appendage (LAA) closure will also be reviewed.

Diagnostic Performance of Transluminal Attenuation Gradient and Noninvasive Fractional Flow Reserve Derived from 320-Detector Row CT Angiography to Diagnose Hemodynamically Significant Coronary Stenosis: An NXT Substudy

PURPOSE

To compare the diagnostic performance of 320-detector row computed tomography (CT) coronary angiography-derived computed fractional flow reserve (FFR; FFRCT), transluminal attenuation gradient (TAG; TAG320), and CT coronary angiography alone to diagnose hemodynamically significant stenosis as determined by invasive FFR.

MATERIALS AND METHODS

This substudy of the prospective NXT study (no. NCT01757678) was approved by each participating institution's review board, and informed consent was obtained from all participants. Fifty-one consecutive patients who underwent 320-detector row CT coronary angiographic examination and invasive coronary angiography with FFR measurement were included. Independent core laboratories determined coronary artery disease severity by using CT coronary angiography, TAG320, FFRCT, and FFR. TAG320 is defined as the linear regression coefficient between luminal attenuation and axial distance from the coronary ostium. FFRCT was computed from CT coronary angiography data by using computational fluid dynamics technology. Diagnostic performance was evaluated and compared on a per-vessel basis by the area under the receiver operating characteristic (ROC) curve (AUC).

RESULTS

Among 82 vessels, 24 lesions (29%) had ischemia by FFR (FFR ≤ 0.80). FFRCT exhibited a stronger correlation with invasive FFR compared with TAG320 (Spearman ρ, 0.78 vs 0.47, respectively). Overall per-vessel accuracy, sensitivity, specificity, and positive and negative predictive values for TAG320 (<15.37) were 78%, 58%, 86%, 64%, and 83%, respectively; and those of FFRCT were 83%, 92%, 79%, 65%, and 96%, respectively. ROC curve analysis showed a significantly larger AUC for FFRCT (0.93) compared with that for TAG320 (0.72; P = .003) and CT coronary angiography alone (0.68; P = .008).

CONCLUSION

FFRCT computed from 320-detector row CT coronary angiography provides better diagnostic performance for the diagnosis of hemodynamically significant coronary stenoses compared with CT coronary angiography and TAG320.

Relationship between epicardial fat and quantitative coronary artery plaque progression: insights from computer tomography coronary angiography

Epicardial fat volume (EFV) has been suggested to promote atherosclerotic plaque development in coronary arteries, and has been correlated with both coronary stenosis and acute coronary events. Although associated with progression of coronary calcification burden, a relationship with progression of coronary atheroma volume has not been previously tested. We studied patients who had clinically indicated serial 320-row multi-detector computer tomography coronary angiography with a median 25-month interval. EFV was measured at baseline and follow-up. In vessels with coronary stenosis, quantitative analysis was performed to measure atherosclerotic plaque burden, volume and aggregate plaque volume at baseline and follow-up. The study comprised 64 patients (58.4 ± 12.2 years, 27 males, 192 vessels, 193 coronary segments). 79 (41 %) coronary segments had stenosis at baseline. Stenotic segments were associated with greater baseline EFV than those without coronary stenosis (117.4 ± 45.1 vs. 102.3 ± 51.6 cm(3), P = 0.046). 46 (24 %) coronary segments displayed either new plaque formation or progression of adjusted plaque burden at follow-up. These were associated with higher baseline EFV than segments without stenosis or those segments that had stenoses that did not progress (128.7 vs. 101.0 vs. 106.7 cm(3) respectively, P = 0.006). On multivariate analysis, baseline EFV was the only independent predictor of coronary atherosclerotic plaque progression or new development (P = 0.014). High baseline EFV is associated with the presence of coronary artery stenosis and plaque volume progression. Accumulation of EFV may be implicated in the evolution and progression of coronary atheroma.

The ASLA Score: A CT Angiographic Index to Predict Functionally Significant Coronary Stenoses in Lesions with Intermediate Severity-Diagnostic Accuracy

PURPOSE

To identify computed tomographic (CT) coronary indexes independently associated with a fractional flow reserve (FFR) of 0.8 or less, to derive a score that combines CT indexes most predictive of an FFR of 0.8 or less, and to evaluate the diagnostic accuracy of the score in predicting an FFR of 0.8 or less.

MATERIALS AND METHODS

This retrospective study had institutional review board approval and waiver of the need to obtain informed consent. Consecutive patients who underwent CT coronary angiography and FFR assessment with one or more discrete lesion(s) of intermediate (30%-70%) severity at CT were included. Quantitative CT measurements were performed by using dedicated software. The CT indexes evaluated included the following: plaque burden, minimal luminal area and diameter, stenosis diameter, area of stenosis, lesion length, remodeling index, plaque morphology, calcification severity, and the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) score, which approximates the size of the myocardium subtended by a lesion. By using covariates independently associated with an FFR of 0.8 or less, a score was determined on the basis of modified Akaike information criteria, and the C statistics of individual and combined indexes were compared.

RESULTS

Eighty-five patients (mean age, 64.2 years; range, 48-88 years; 65.9% men; 124 lesions; 38 lesions with an FFR ≤ 0.8) were included. Area of stenosis, lesion length, and APPROACH score were the strongest predictors of an FFR of 0.8 or less and were used to derive the ASLA score. The optimism-adjusted Harrell C statistic for the combined score was 0.82, which was superior to that for area of stenosis (0.74), lesion length (0.75), and the APPROACH score (0.71) (P < .001 for trend). The corresponding incremental discrimination improvement indexes were 0.17, 0.11, and 0.19, respectively (P < .001 for all), suggesting that the score improves reclassification compared with any one angiographic index. The average time required for score derivation was 102.6 seconds.

CONCLUSION

The ASLA score, which accounts for CT-derived area of stenosis, lesion length, and APPROACH score, may conveniently improve the prediction, beyond individual indexes, of functionally significant intermediate coronary lesions.

Epicardial adipose tissue: far more than a fat depot

Epicardial adipose tissue (EAT) refers to the fat depot that exists on the surface of the myocardium and is contained entirely beneath the pericardium, thus surrounding and in direct contact with the major coronary arteries and their branches. EAT is a biologically active organ that may play a role in the association between obesity and coronary artery disease (CAD). Given recent advances in non-invasive imaging modalities such a multidetector computed tomography (MDCT), EAT can be accurately measured and quantified. In this review, we focus on the evidence suggesting a role for EAT as a quantifiable risk marker in CAD, as well as describe the role EAT may play in the development and vulnerability of coronary artery plaque.

Superior CT coronary angiography image quality at lower radiation exposure with second generation 320-detector row CT in patients with elevated heart rate: a comparison with first generation 320-detector row CT

BACKGROUND

This study aims to compare the image quality of second generation versus first generation 320-computed tomography coronary angiography (CTCA) in patients with heart rate ≥65 bpm as it has not been specifically reported.

METHODS

Consecutive patients who underwent CTCA using second-generation-320-detector-row-CT were prospectively enrolled. A total of 50 patients with elevated (≥65 bpm) heart rate and 50 patients with controlled (<65 bpm) heart rate were included. Age and gender matched patients who were scanned with the first-generation-320-detector-row-CT were retrospectively identified. Image quality in each coronary artery segment was assessed by two blinded CT angiographers using the five-point Likert scale.

RESULTS

In the elevated heart rate cohorts, while there was no significant difference in heart rate during scan-acquisition (66 vs. 69 bpm, P=0.308), or body mass index (28.5 vs. 29.6, P=0.464), the second generation scanner was associated with better image quality (3.94±0.6 vs. 3.45±0.8, P=0.001), and with lower radiation (2.8 vs. 4.3 mSv, P=0.009). There was no difference in scan image quality for the controlled heart rate cohorts.

CONCLUSIONS

The second generation CT scanner provides better image quality at lower radiation dose in patients with elevated heart rate (≥65 bpm) compared to first generation CT scanner.

Anatomic characteristics and outcome of adults with coronary arteries arising from an anomalous location detected with coronary computed tomography angiography

We sought to determine the anatomic characteristics of coronary arteries arising from an anomalous location (CAAL) detected on coronary computed tomography angiography (CTA) and assess the impact of high-risk anatomic characteristics on patient management and outcomes. We reviewed 9,774 consecutive CTA studies performed in adults between 2008-2013 and identified 114 with CAAL. CTA examinations were analysed to determine CAAL type, CAAL course (pre-pulmonary, interarterial, septal or retroaortic) and whether additional high-risk anatomic characteristics were present (luminal compression, intramural course, slit-like ostium and acute takeoff angle). Patients were contacted at mean 27.1-months to determine safety outcomes. The prevalence of CAAL was 1.14 % (114 of 9,974), with 36 (32 %) having anomalous right coronary artery from left coronary sinus, 71 (62 %) having anomalous left coronary artery from right coronary sinus and 7 (6 %) having a coronary artery arising outside coronary sinuses. Fifty-six patients (49 %) had ≥1 high-risk anatomic characteristic on CTA. Ten patients (9 %) underwent surgical intervention. Patients with high-risk anatomic features more frequently underwent functional testing (46 vs. 12 %, P = 0.01) and surgical intervention (14 vs. 3 %; P = 0.04) compared to patients without high-risk features. Patients undergoing surgery were more likely to have obstructive coronary disease on CTA than patients managed conservatively (50 vs. 13 %, P = 0.01). There was no cardiac death or ACS at follow-up (100 % complete). High-risk anatomic features on CTA in patients with CAAL more frequently lead to surgical management. Regardless of CAAL type, presence of high-risk anatomic characteristics or management strategy, the medium-term outcome of adults with CAAL is excellent.

Long-term outcome after CT angiography in patients with possible acute coronary syndrome

PURPOSE

To assess the long-term outcome and hospital readmission rate associated with a computed tomographic (CT) angiography-guided strategy used to examine patients who present to the emergency department (ED) with symptoms of possible acute coronary syndrome (ACS).

MATERIALS AND METHODS

The study was approved by the institutional review board, and all patients provided written informed consent. A total of 585 consecutive patients (mean age, 58 years ± 11 [standard deviation]; 58% were male) with ischemic-type chest pain and low to intermediate risk for ACS were evaluated prospectively. Patients underwent coronary CT angiography after single or serial troponin I (TnI) measurement, depending on time of presentation to the ED. Subsequent care was determined with CT angiography findings: Patients without plaque and patients with nonobstructive plaque and at most mild to moderate stenosis (<40% luminal narrowing) were discharged without further investigation. Patients with moderate stenosis (40%-70% narrowing) were discharged and referred for outpatient stress echocardiography. Patients with severe stenosis (>70% narrowing) were admitted. Discharged patients were contacted and their medical records were reviewed to determine rates of death, ACS, revascularization, and hospital admission. By using binomial distribution, Clopper-Pearson confidence intervals (CIs) were calculated for outcome data.

RESULTS

Coronary CT angiography findings were as follows: A total of 196 patients (34%) had no coronary plaque or stenosis, 288 (49%) had nonobstructive plaque, 22 (4%) had moderate stenosis, and 79 (13%) had severe stenosis. At median 47.4-month follow-up (range, 24-57 months) of the 506 discharged patients, five (1%; 95% CI: 0.4%, 2.3%) had been readmitted for chest pain; there were no instances of coronary revascularization, ACS, or death (0% for all; 95% CI: 0%, 0.7%). Follow-up was 100% complete.

CONCLUSION

Use of a CT angiography-guided strategy to investigate patients with low to intermediate risk of ACS who present to the ED with chest pain is safe at long-term follow-up, including patients discharged after single TnI measurement.

320-row CT coronary angiography predicts freedom from revascularisation and acts as a gatekeeper to defer invasive angiography in stable coronary artery disease: a fractional flow reserve-correlated study

OBJECTIVES

To determine the accuracy of 320-row multidetector coronary computed tomography angiography (M320-CCTA) to detect functional stenoses using fractional flow reserve (FFR) as the reference standard and to predict revascularisation in stable coronary artery disease.

METHODS

One hundred and fifteen patients (230 vessels) underwent M320-CCTA and FFR assessment and were followed for 18 months. Diameter stenosis on invasive angiography (ICA) and M320-CCTA were assessed by consensus by two observers and significant stenosis was defined as ≥50%. FFR ≤0.8 indicated functionally significant stenoses.

RESULTS

M320-CCTA had 94% sensitivity and 94% negative predictive value (NPV) for FFR ≤0.8. Overall accuracy was 70%, specificity 54% and positive predictive value 65%. On receiver operating characteristic (ROC) curve analysis, the area under the curve (AUC) for CCTA to predict FFR ≤0.8 was 0.74 which was comparable with ICA. The absence of a significant stenosis on M320-CCTA was associated with a 6% revascularisation rate. M320-CCTA predicted revascularisation with an AUC of 0.71 which was comparable with ICA.

CONCLUSIONS

M320-CCTA has excellent sensitivity and NPV for functional stenoses and therefore may act as an effective gatekeeper to defer ICA and revascularisation. Like ICA, M320-CCTA lacks specificity for functional stenoses and only has moderate accuracy to predict the need for revascularisation.

KEY POINTS

• Important information about the heart is provided by 320-row multidetector CT coronary angiography (M320-CCTA). • M320-CCTA accurately detects and excludes functional stenoses determined by fractional flow reserve (FFR). • Non-significant stenoses on M320-CCTA associated with fewer cardiac events and less revascularisation. • M320-CCTA may act as a gatekeeper for invasive angiography and inappropriate revascularisation. • Like ICA, M320-CCTA only has moderate accuracy to predict vessels requiring revascularisation.

Validation of conventional fluoroscopic and ECG criteria for right ventricular pacemaker lead position using cardiac computed tomography

INTRODUCTION

It is hypothesized that pacing the right ventricular (RV) septum is associated with less deleterious outcomes than RV apical pacing. Our aim was to validate fluoroscopic and electrocardiography (ECG) criteria for describing pacemaker and implantable cardioverter defibrillator RV "septal" lead position against the proposed gold standard: cardiac computed tomography (CT).

METHODS

Using the conventional fluoroscopic criteria, we intended to place RV nonapical leads on the interventricular septum. Lead positions were later retrospectively analyzed with CT and correlated with ECGs and fluoroscopic projections: posterior-anterior, 40° left anterior oblique (LAO), 40° right anterior oblique (RAO), and left lateral.

RESULTS

Only 21% (nine of 35) of presumed "septal" RV nonapical leads using the conventional fluoroscopic criteria were on the true septum. A schema developed to define septal position in the RAO fluoroscopic view had high agreement with CT images. ECG criteria had only fair to moderate agreement with CT. The paced QRS duration was significantly longer (P < 0.001) with RV apical pacing (176 ± 10.7 ms), compared to RV nonapical pacing (144.5 ± 14.3 ms).

CONCLUSION

Using the conventional fluoroscopic criteria, only a minority of RV leads were implanted on the true RV septum. Instead, aiming for the middle of the cardiac silhouette in the RAO fluoroscopic view, confirming rightward orientation in the LAO view, and having a paced QRS duration <140 ms may allow the implanting cardiologist a simple, more accurate method to achieve true RV septal lead positioning.

Combined CT coronary angiography and stress myocardial perfusion imaging for hemodynamically significant stenoses in patients with suspected coronary artery disease: a comparison with fractional flow reserve

OBJECTIVES

We sought to determine the accuracy of combined coronary computed tomography angiography (CTA) and computed tomography stress myocardial perfusion imaging (CTP) in the detection of hemodynamically significant stenoses using fractional flow reserve (FFR) as a reference standard in patients with suspected coronary artery disease.

BACKGROUND

CTP can be qualitatively assessed by visual interpretation or quantified by the transmural perfusion ratio determined as the ratio of subendocardial to subepicardial contrast attenuation. The incremental value of each technique in addition to coronary CTA to detect hemodynamically significant stenoses is not known.

METHODS

Forty symptomatic patients underwent FFR and 320-detector computed tomography assessment including coronary CTA and CTP. Myocardial perfusion was assessed using the transmural perfusion ratio and visual perfusion assessment. Computed tomography images were assessed by consensus of 2 observers. Transmural perfusion ratio <0.99 was used as the threshold for abnormal perfusion. FFR ≤0.8 indicated hemodynamically significant stenoses.

RESULTS

Coronary CTA detected FFR-significant stenoses with 95% sensitivity and 78% specificity. The additional use of visual perfusion assessment and the transmural perfusion ratio both increased the specificity to 95%, with sensitivity of 87% and 71%, respectively. The area under the receiver-operating characteristic curve for coronary CTA + visual perfusion assessment was significantly higher than both coronary CTA (0.93 vs. 0.85, p = 0.0003) and coronary CTA + the transmural perfusion ratio (0.93 vs. 0.79, p = 0.0003). Per-vessel and per-patient accuracy for coronary CTA, coronary CTA + the transmural perfusion ratio, and coronary CTA + visual perfusion assessment was 83% and 83%, 87% and 92%, and 92% and 95%, respectively.

CONCLUSIONS

In suspected coronary artery disease, combined coronary CTA + CTP identifies patients with hemodynamically significant stenoses with >90% accuracy compared with FFR. When interpreted with coronary CTA, visual perfusion assessment provided superior incremental value in the detection of FFR-significant stenoses compared with the quantitative transmural perfusion ratio assessment.

Transluminal attenuation gradient in coronary computed tomography angiography is a novel noninvasive approach to the identification of functionally significant coronary artery stenosis: a comparison with fractional flow reserve

OBJECTIVE

The purpose of this study was to assess the diagnostic accuracy of TAG320 in predicting functional stenosis severity evaluated by fractional flow reserve (FFR).

BACKGROUND

Coronary computed tomography angiography (CCTA) has limited specificity for predicting functionally significant stenoses. Recent studies suggest that contrast gradient attenuation along an arterial lesion, or transluminal attenuation gradient (TAG), may provide assessment of functional significance of coronary stenosis. The use of 320-detector row computed tomography (CT), enabling near isophasic, single-beat imaging of the entire coronary tree, may be ideal for TAG functional assessment of a coronary arterial stenosis.

METHODS

We assessed the diagnostic accuracy of TAG320 using 320-row CCTA with FFR for the evaluation of functional stenosis severity in consecutive patients undergoing invasive coronary angiography and FFR for stable chest pain. The luminal radiological contrast attenuation (Hounsfield units [HU]) was measured at 5-mm intervals along the artery from ostium to a distal level where the cross-sectional area decreased to <2.0 mm(2). TAG320 was defined as the linear regression coefficient between luminal attenuation and axial distance. Functionally significant coronary stenosis was defined as ≤0.8 on FFR.

RESULTS

In our cohort of 54 patients (age 62.7 ± 8.7 years, 35 men, 78 vessels), TAG320 in FFR-significant vessels was significantly lower when compared with FFR nonsignificant vessels (-21 [-27; -16] vs. -11 [-16; -3] HU/10 mm, p < 0.001). On receiver-operating characteristic analysis, a retrospectively determined TAG320 cutoff of -15.1 HU/10 mm predicted FFR ≤0.8 with (a bootstrapped resampled) a sensitivity of 77%, specificity of 74%, positive predictive value of 67%, and negative predictive value of 86%. The combined TAG320 and CCTA assessment had an area under the curve of 0.88. There was incremental value of adding TAG320 to CCTA assessment for detection of significant FFR by Wald test (p = 0.0001) and integrated discrimination improvement index (0.11, p = 0.002).

CONCLUSIONS

Assessment of TAG320 with a 320-detector row CT provides acceptable prediction of invasive FFR and may provide a noninvasive modality for detecting functionally significant coronary stenoses. Combined TAG320 and CCTA assessment may have incremental predictive value over CCTA alone for detecting functionally significant coronary arterial stenoses; however, larger studies are required to determine the benefit of combined TAG320 and CCTA assessment.

A stepwise approach to the visual interpretation of CT-based myocardial perfusion

Cardiovascular anatomic and functional testing have been longstanding and key components of cardiac risk assessment. As part of that strategy, CT-based imaging has made steady progress, with coronary computed tomography angiography (CTA) now established as the most sensitive noninvasive strategy for assessment of significant coronary artery disease. Myocardial CT perfusion imaging (CTP), as the functional equivalent of coronary CTA, is being tested in currently ongoing multicenter trials and is proposed to enhance the accuracy of coronary CTA alone. However, unlike coronary CTA that has published guidelines for interpretation and is rapidly gaining applicability in the noninvasive risk assessment paradigms, myocardial CTP is rapidly evolving, and guidance on a standard approach to its interpretation is lacking. In this article we describe a practical stepwise approach for interpretation of myocardial CTP that should add to the clinical applicability of this modality. These steps include (1) coronary CTA interpretation for potentially obstructive atherosclerosis, (2) reconstruction and preprocessing of myocardial CTP images, (3) image quality assessment and the identification of potentially confounding artifacts, (4) rest and stress image interpretation for enhancement patterns and areas of hypoattenuation, and (5) correlation of coronary anatomy and myocardial perfusion deficits. This systematic review uses already published methods from multiple clinical studies and is intended for general usage, independent of the platform used for image acquisition.

Computed tomography stress myocardial perfusion imaging in patients considered for revascularization: a comparison with fractional flow reserve

AIMS

Adenosine stress computed tomography myocardial perfusion imaging (CTP) is an emerging non-invasive method for detecting myocardial ischaemia. Its value when compared with fractional flow reserve (FFR), a highly accurate index of ischaemia, is unknown. Our aim was to determine the diagnostic accuracy of CTP and its incremental value when used with computed tomography coronary angiography (CTA) for detecting ischaemia compared with FFR.

METHODS AND RESULTS

Forty-two patients (126 vessel territories), who had at least one ≥50% angiographic stenosis on invasive angiography considered for non-urgent revascularization, were included and underwent FFR and CT assessment, including CTP, delayed contrast enhancement scan and CTA all acquired using 320-detector row CT, and prospective ECG gating. Fractional flow reserve was determined in 86 territories subtended by vessels with ≥50% stenosis upon visual assessment. Fractional flow reserve ≤0.8 was considered to indicate significant ischaemia. Computed tomography myocardial perfusion imaging correctly identified 31/41 (76%) ischaemic territories and 38/45 (84%) non-ischaemic territories. Per-vessel territory sensitivity, specificity, positive, and negative predictive values of CTP were 76, 84, 82, and 79%, respectively. The combination of a ≥50% stenosis on CTA and perfusion defect on CTP was 98% specific for ischaemia, while the presence of <50% stenosis on CTA and normal perfusion on CTP was 100% specific for exclusion of ischaemia. Mean radiation for CTP and combined CT was 5.3 and 11.3 mSv, respectively.

CONCLUSION

Computed tomography myocardial perfusion imaging is moderately accurate in identifying perfusion defects associated with ischaemia as assessed by FFR in patients considered for revascularization. In territories, where CTA and CTP are concordant, CTA/CTP is highly accurate in the detection and exclusion of ischaemia. This is achievable with acceptable radiation exposure using 320-detector row CT and prospective ECG gating.

Acute chest pain investigation: utility of cardiac CT angiography in guiding troponin measurement

PURPOSE

To assess the impact on length of stay and rate of major adverse cardiovascular events of a cardiac computed tomographic (CT) angiography-guided algorithm to examine patients who present to the emergency department (ED) with low- to intermediate-risk chest pain.

MATERIALS AND METHODS

The study was approved by the institutional review board, and all patients gave written informed consent. Two hundred three consecutive patients (mean age, 55 years ± 11 [standard deviation]; 123 men) with low- to intermediate-risk ischemic-type chest pain were prospectively enrolled. Patients underwent initial cardiac CT angiography with subsequent treatment determined by reference to findings at cardiac CT angiography; patients without overt plaque were immediately discharged from the hospital, patients with nonobstructive plaque and mild-to-moderate stenoses were discharged after a negative 6-hour troponin level, and patients with severe stenoses were admitted to the hospital. Discharged patients were followed up for a mean of 14.2 months. Additionally, length of stay and safety outcomes among these patients were compared with those in 102 consecutive patients with low- to intermediate-risk chest pain who presented to the ED and underwent a standard of care (SOC) work-up without cardiac CT angiography. One-way analysis of variance with Bonferroni correction was used to compare length of stay between groups.

RESULTS

Cardiac CT angiography findings in the 203 patients who underwent cardiac CT angiography were as follows: Sixty-five (32%) patients had no plaque, 107 (53%) had nonobstructive plaque, and 31 (15%) had severe stenoses. At follow-up, there were no deaths or cases of acute coronary syndrome (cardiac CT angiography, 0%, 95% confidence interval [CI]: 0%, 1.85%; SOC, 0%, 95% CI: 0%, 3.63%), and the rate of readmission to the hospital because of chest pain was higher with the SOC approach (9% vs 1%, P = .01). Mean ED length of stay was lower with cardiac CT angiography (6.62 hours ± 0.38 after a single troponin level and 9.15 hours ± 0.30 after serial troponin levels) than with the SOC approach (11.62 hours ± 0.47, P < .001).

CONCLUSION

Tailoring troponin measurement to cardiac CT angiography findings is safe and allows early discharge of patients with low- to intermediate-risk chest pain, resulting in reduced length of stay.

Left atrial volume and index by multi-detector computed tomography: comprehensive analysis from predictors of enlargement to predictive value for acute coronary syndrome (ROMICAT study)

OBJECTIVES

We aimed to identify the predictors of left atrial (LA) enlargement by multi-detector computed tomography (CT) and determine its association and predictive value for acute coronary syndrome (ACS).

BACKGROUND

LA enlargement is associated with myocardial ischemia and coronary artery disease (CAD) and is a strong predictor for cardiovascular events. These studies were performed primarily with echocardiography. With the rise of cardiac CT, LA volume can be readily measured.

METHODS

In 377 emergency department patients with chest pain, we performed 64-slice CT for coronary artery assessment. We derived LA volumes (LAV(max), LAV(min)) and indices (LAVI(max), LAVI(min)) using a threshold-based volumetric method.

RESULTS

Subjects, with cardiac risk factors or CAD by CT, had larger LA (ΔLAV(max) 9.1 ml, p=0.004; ΔLAV(min) 8.1 ml, p=0.001; ΔLAVI(max) 3.3 ml/m(2), p=0.03; ΔLAVI(min) 3.4 ml/m(2), p=0.006) than controls. Predictors of LA enlargement were related to risk factors for diastolic dysfunction. ACS risk was greater in patients with top quartile LAV(max) (odds ratio [OR] 3.4, p=0.02) and LAV(min) (OR 4.7, p=0.01) than lowest quartile, but not when indexed. Similarly, the predictive values of LA volumes were incrementally better when added to CT finding of indeterminate stenosis (LAV(max): C statistic 0.62 to 0.70, p=0.046; LAV(min): C statistic 0.65 to 0.73, p=0.008), but not when indexed.

CONCLUSIONS

Risk factors related to diastolic dysfunction are independent predictors of LA enlargement. LA enlargement by volumes are associated with a 3-5 fold increase risk for ACS and have incremental value for predicting ACS when added to the CT finding of indeterminate stenosis.

Diagnostic accuracy of noninvasive coronary angiography with 320-detector row computed tomography

We sought to evaluate the diagnostic accuracy of noninvasive coronary angiography using 320-detector row computed tomography, which provides 16-cm craniocaudal coverage in 350 ms and can image the entire coronary tree in a single heartbeat, representing a significant advance from previous-generation scanners. We evaluated 63 consecutive patients who underwent 320-detector row computed tomography and invasive coronary angiography for the investigation of suspected coronary artery disease. Patients with known coronary artery disease were excluded. Computed tomographic (CT) studies were assessed by 2 independent observers blinded to results of invasive coronary angiography. A single observer unaware of CT results assessed invasive coronary angiographic images quantitatively. All available coronary segments were included in the analysis, regardless of size or image quality. Lesions with >50% diameter stenoses were considered significant. Mean heart rate was 63 ± 7 beats/min, with 6 patients (10%) in atrial fibrillation during image acquisition. Thirty-three patients (52%) and 70 of 973 segments (7%) had significant coronary stenoses on invasive coronary angiogram. Seventeen segments (2%) were nondiagnostic on computed tomogram and were assumed to contain significant stenoses on an "intention-to-diagnose" analysis. Sensitivity, specificity, and positive and negative predictive values of computed tomography for detecting significant stenoses were 94%, 87%, 88%, and 93%, respectively, by patient (n = 63), 89%, 95%, 82%, and 97%, respectively, by artery (n = 260), and 87%, 97%, 73%, and 99%, respectively, by segment (n = 973). In conclusion, noninvasive 320-detector row CT coronary angiography provides high diagnostic accuracy across all coronary segments, regardless of size, cardiac rhythm, or image quality.

Same-day discharge is feasible and safe in the majority of elderly patients undergoing elective percutaneous coronary intervention

BACKGROUND

Same-day discharge after elective percutaneous coronary intervention (PCI) is safe in the majority of patients. However, the elderly have more comorbidities and less favorable coronary and peripheral arterial anatomy, which may preclude safe same-day discharge after PCI. We assessed the feasibility and safety of same-day discharge in an elderly cohort of patients.

METHODS

A total of 1,580 consecutive patients undergoing elective PCI in a single center between January 2001 and January 2009 were included in the study. We compared the outcomes of elderly patients aged 75 or older to control patients under the age of 75 years. Patients were examined 6 hours post procedure and discharged if there were no complications.

RESULTS

Of the 1,580 study patients 212 (13.4%) were elderly and 1,365 (86.6%) were younger controls. The elderly were more likely to be female, hypertensive and to have had previous coronary artery bypass graft (CABG) surgery and less likely to be smokers or to have hyperlipidemia (all p < 0.05). The number of lesions treated and their complexity were similar in both groups. Procedural success, in-hospital major adverse cardiac events (MACE) and the rates of same-day discharge were also similar in both groups. Same-day discharge was achieved in the majority (84%) of the elderly. There were no deaths within 24 hours of discharge. Readmission within 24 hours of discharge was rare (< 0.7%) in both groups. The 30-day MACE rate was low in both the elderly (3.3%) and control groups (3.6%; p = 1.0).

CONCLUSIONS

Same-day discharge is safe and feasible in the majority of elderly patients following elective PCI.

Incremental diagnostic value of regional left ventricular function over coronary assessment by cardiac computed tomography for the detection of acute coronary syndrome in patients with acute chest pain: from the ROMICAT trial

BACKGROUND

The incremental value of regional left ventricular function (LVF) over coronary assessment to detect acute coronary syndrome (ACS) is uncertain.

METHODS AND RESULTS

We analyzed 356 patients (mean age, 53+/-12 years; 62% men) with acute chest pain and inconclusive initial emergency department evaluation. Patients underwent 64-slice contrast-enhanced cardiac computed tomography before hospital admission. Caregivers and patients remained blinded to the results. Regional LVF and presence of coronary atherosclerotic plaque and significant stenosis (>50%) were separately assessed by 2 independent readers. Incremental value of regional LVF to predict ACS was determined in the entire cohort and in subgroups of patients with nonobstructive coronary artery disease, inconclusive assessment for stenosis (defined as inability to exclude significant stenosis due to calcium or motion), and significant stenosis. During their index hospitalization, 31 patients were ultimately diagnosed with ACS (8 myocardial infarction, 22 unstable angina), of which 74% (23 patients) had regional LV dysfunction. Adding regional LVF resulted in a 10% increase in sensitivity to detect ACS by cardiac computed tomography (87%; 95% confidence interval, 70% to 96%) and significantly improved the overall accuracy (c-statistic: 0.88 versus 0.94 and 0.79 versus 0.88, for extent of plaque and presence of stenosis, respectively; both P<0.03). The diagnostic accuracy of regional LVF for detection of ACS has 89% sensitivity and 86% specificity in patients with significant stenosis (n=33) and 60% sensitivity and 86% specificity in patients with inconclusive coronary computed tomographic angiography (n=33).

CONCLUSIONS

Regional LVF assessment at rest improves diagnostic accuracy for ACS in patients with acute chest pain, especially in those with coronary artery disease and thus may be helpful to guide further management in patients at intermediate risk for ACS.

Quantitative assessment of left atrial volume by electrocardiographic-gated contrast-enhanced multidetector computed tomography

BACKGROUND

Left atrial (LA) volume is a predictor of cardiovascular events. Information on LA volume is available on contrast-enhanced electrocardiogram (EGC)-gated multidetector computed tomography (MDCT) scans.

OBJECTIVE

To assess interobserver and intraobserver reproducibility of 3-dimensional threshold-based volume (3DTV) and 2-dimensional (2D) measurements for the assessment of LA volumes with contrast-enhanced cardiac 64-slice MDCT.

METHODS

Contrast-enhanced 64-slice MDCT (0.6-mm slice thickness, 120 kVp, 850 mAseff) was performed in 96 consecutive subjects (mean age 52 years; 48% women) as a subset of the Rule Out Myocardial Infarction using Computer Assisted Tomography trial. Two observers independently measured maximal (LAV(max)) and minimal (LAV(min)) LA volumes with (1) a modified Simpson's method (3DTV) based on delineation of LA areas in axial slices and (2) estimated LA volumes typically used in 2D echocardiography (area length and prolate ellipse). Interobserver and intraobserver reproducibility for each method as well as correlations between the methods were calculated.

RESULTS

Interobserver (n = 96) and intraobserver (n = 20) variability was significantly lower for 3DTV (8%) than for area length (13%; P < 0.001) or prolate ellipse (16%; P < 0.001). 2D-based measurements rendered significantly lower LA volumes than did 3DTV (area length: -17% and -22%; prolate ellipse: -43% and -46% for LAV(max) and LAV(min), respectively; P < 0.001 for all). By 3DTV, mean LA volume was 90.4 +/- 24.5 mL for LAV(max) and 52.5 +/- 17.6 mL for LAV(min).

CONCLUSION

ECG-gated contrast-enhanced cardiac MDCT offers volumetric assessment of LA volume with excellent reproducibility without additional contrast administration or radiation exposure. 3D measures of LA volume are more reproducible and render larger volumes than 2D-derived estimates, typically used in echocardiography.

CT angiography: front line for acute coronary syndromes now?

See article on page 1386