Annika Schuhbaeck

A method to determine suitable fluoroscopic projections for transcatheter aortic valve implantation by computed tomography.

BACKGROUND In transcatheter aortic valve implantation (TAVI), optimal selection of fluoroscopic projections that permit orthogonal visualization of the aortic valve plane is important but may be difficult to achieve. OBJECTIVE We developed and validated a simple method to predict suitable fluoroscopic projections on the basis of cardiac CT datasets. METHODS In 75 consecutive patients that underwent TAVI, angulations in which a 35-mm thick maximum intensity projection would render all aortic valve calcium into 1 plane were determined by manual interaction with contrast-enhanced dual-source CT datasets. TAVI operators used the predicted angulation for the first aortic angiogram and performed additional aortic angiograms if no satisfactory view of the aortic valve plane was obtained. Predicted angulations were compared with the angulation used for valve implantation. Radiation exposure and contrast use was compared between patients with accurate prediction of fluoroscopic angulations by CT and patients in whom CT failed to predict a suitable view. RESULTS The mean difference between the predicted angulation according to CT and the angulation used for implantation was 3 ± 6 degrees. CT predicted a suitable angulation (<5-degree deviation) in 63 of 75 cases (84%). The mean number of aortic angiograms acquired in patients with correct prediction (1.02 ± 0.1) was significantly lower than in patients with incorrect prediction of the implantation angle by CT (3.0 ± 1.7; P < 0.001). Contrast agent required for the entire TAVI procedure was lower in patients with correct prediction (72 ± 36 mL vs 106 ± 39 mL; P = 0.001). CONCLUSION CT permits prediction of suitable angulations for TAVI in most cases.

Automated Quantitative Plaque Burden from Coronary CT Angiography Noninvasively Predicts Hemodynamic Significance by using Fractional Flow Reserve in Intermediate Coronary Lesions

PURPOSE To evaluate the utility of multiple automated plaque measurements from coronary computed tomographic (CT) angiography in determining hemodynamic significance by using invasive fractional flow reserve (FFR) in patients with intermediate coronary stenosis. MATERIALS AND METHODS The study was approved by the institutional review board. All patients provided written informed consent. Fifty-six intermediate lesions (with 30%-69% diameter stenosis) in 56 consecutive patients (mean age, 62 years; range, 46-88 years), who subsequently underwent invasive coronary angiography with assessment of FFR (values ≤0.80 were considered hemodynamically significant) were analyzed at coronary CT angiography. Coronary CT angiography images were quantitatively analyzed with automated software to obtain the following measurements: volume and burden (plaque volume × 100 per vessel volume) of total, calcified, and noncalcified plaque; low-attenuation (<30 HU) noncalcified plaque; diameter stenosis; remodeling index; contrast attenuation difference (maximum percent difference in attenuation per unit area with respect to the proximal reference cross section); and lesion length. Logistic regression adjusted for potential confounding factors, receiver operating characteristics, and integrated discrimination improvement were used for statistical analysis. RESULTS FFR was 0.80 or less in 21 (38%) of the 56 lesions. Compared with nonischemic lesions, ischemic lesions had greater diameter stenosis (65% vs 52%, P = .02) and total (49% vs 37%, P = .0003), noncalcified (44% vs 33%, P = .0004), and low-attenuation noncalcified (9% vs 4%, P < .0001) plaque burden. Calcified plaque and remodeling index were not significantly different. In multivariable analysis, only total, noncalcified, and low-attenuation noncalcified plaque burden were significant predictors of ischemia (P < .015). For predicting ischemia, the area under the receiver operating characteristics curve was 0.83 for total plaque burden versus 0.68 for stenosis (P = .04). CONCLUSION Compared with stenosis grading, automatic quantification of total, noncalcified, and low-attenuation noncalcified plaque burden substantially improves determination of lesion-specific hemodynamic significance by FFR in patients with intermediate coronary lesions.

Comparison of quantitative atherosclerotic plaque burden from coronary CT angiography in patients with first acute coronary syndrome and stable coronary artery disease

BACKGROUND Coronary CTA allows characterization of non-calcified and calcified plaque and identification of high-risk plaque features. OBJECTIVE We aimed to quantitatively characterize and compare coronary plaque burden from CTA in patients with a first acute coronary syndrome (ACS) and controls with stable coronary artery disease. MATERIALS AND METHODS We retrospectively analyzed consecutive patients with non-ST-segment elevation myocardial infarction (NSTEMI) or unstable angina with a first ACS, who underwent CTA as part of their initial workup before invasive coronary angiography and age- and gender-matched controls with stable chest pain; controls also underwent CTA with subsequent invasive angiography (total n = 28). Culprit arteries were identified in ACS patients. Coronary arteries were analyzed by automated software to quantify calcified plaque (CP), noncalcified plaque (NCP), and low-density NCP (LD-NCP, attenuation <30 Hounsfield units) volumes, and corresponding burden (plaque volume × 100%/vessel volume), stenosis, remodeling index, contrast density difference (maximum percent difference in attenuation/cross-sectional area from proximal cross-section), and plaque length. RESULTS ACS patients had fewer lesions (median, 1), with higher total NCP and LD-NCP burdens (NCP: 57.4% vs 41.5%; LD-NCP: 12.5% vs 8%; P ≤ .04), higher maximal stenoses (85.6% vs 53.0%; P = .003) and contrast density differences (46.1 vs 16.3%; P < .006). Per-patient CP burden was not different between ACS and controls. NCP and LD-NCP plaque burden was higher in culprit vs nonculprit arteries (NCP: 57.8% vs 9.5%; LD-NCP: 8.4% vs 0.6%; P ≤ .0003); CP was not significantly different. Culprit arteries had increased plaque lengths, remodeling indices, stenoses, and contrast density differences (46.1% vs 10.9%; P ≤ .001). CONCLUSION Noninvasive quantitative coronary artery analysis identified several differences for ACS, both on per-patient and per-vessel basis, including increased NCP, LD-NCP burden, and contrast density difference.

Non-invasive prediction of hemodynamically significant coronary artery stenoses by contrast density difference in coronary CT angiography

OBJECTIVES Coronary computed tomography angiography (CTA) allows the detection of obstructive coronary artery disease. However, its ability to predict the hemodynamic significance of stenoses is limited. We assessed differences in plaque characteristics and contrast density difference between hemodynamically significant and non-significant stenoses, as defined by invasive fractional flow reserve (FFR). METHODS Lesion characteristics of 59 consecutive patients (72 lesions) in whom invasive FFR was performed in at least one coronary artery with moderate to high-grade stenoses in coronary CTA were evaluated by two experienced readers. Coronary CTA data sets were acquired on a second-generation dual-source CT scanner using retrospectively ECG-gated spiral acquisition or prospectively ECG-triggered axial acquisition mode. Plaque volume and composition (non-calcified, calcified), remodeling index as well as contrast density difference (defined as the percentage decline in luminal CT attenuation/cross-sectional area over the lesion) were assessed using a semi-automatic software tool (Autoplaq). Additionally, the transluminal attenuation gradient (defined as the linear regression coefficient between intraluminal CT attenuation and length from the ostium) was determined. Differences in lesion characteristics between hemodynamically significant (invasively measured FFR ≤0.80) and non-significant lesions (FFR >0.80) were determined. RESULTS Mean patient age was 64±11 years with 44 males (75%). 21 out of 72 coronary artery lesions (29%) were hemodynamically significant according to invasive FFR. Mean invasive FFR was 0.66±0.12 vs. 0.91±0.05 for hemodynamically significant versus non-significant lesions. Hemodynamically significant lesions showed a significantly greater percentage of non-calcified plaque compared to non-hemodynamically relevant lesions (51.3±15.3% vs. 43.6±16.5%, p=0.021). Contrast density difference was significantly increased in hemodynamically relevant lesions (26.0±20.2% vs. 16.6±10.9% for non-significant lesions; p=0.013). At a threshold of ≥24%, the contrast density difference predicted hemodynamically significant lesions with a specificity of 75%, sensitivity of 33%, PPV of 35% and NPV of 73%. The transluminal attenuation gradient showed no significant difference between hemodynamically significant and non-significant lesions (-1.4±1.4HU/mm vs. -1.1±1.3HU/mm, p=n.s.). CONCLUSIONS Quantitative contrast density difference across coronary lesions in coronary CTA data sets may be applied as a non-invasive tool to identify hemodynamically significant stenoses.

Non-invasive measurement of coronary plaque from coronary CT angiography and its clinical implications

Coronary CT angiography (CTA) is increasingly used worldwide for direct, non-invasive evaluation of the coronary arteries. Advances in computed tomography (CT) technology over the last decade have enabled such reliable imaging of the coronary arteries. Beyond arterial stenosis, coronary CTA also permits assessment of atherosclerotic plaque (including plaque burden) and coronary artery remodeling, previously only achievable through invasive means. It has been shown that coronary plaque volumes for non-calcified and mixed plaques and the arterial remodeling index, correlate closely with invasive intravascular ultrasound. Several studies have also shown a strong relationship of adverse plaque features imaged by coronary CTA with acute coronary syndrome, all-cause death, major adverse cardiovascular events and myocardial ischemia. The aim of this review is to summarize current methods for quantitative measurement of atherosclerotic plaque features from coronary CTA and to discuss their clinical implications.

Relationship Between Quantitative Adverse Plaque Features From Coronary Computed Tomography Angiography and Downstream Impaired Myocardial Flow Reserve by 13N-Ammonia Positron Emission Tomography A Pilot Study

Background—We investigated the relationship of quantitative plaque features from coronary computed tomography (CT) angiography and coronary vascular dysfunction by impaired myocardial flow reserve (MFR) by 13N-Ammonia positron emission tomography (PET). Methods and Results—Fifty-one patients (32 men, 62.4±9.5 years) underwent combined rest–stress 13N-ammonia PET and CT angiography scans by hybrid PET/CT. Regional MFR was measured from PET. From CT angiography, 153 arteries were evaluated by semiautomated software, computing arterial noncalcified plaque (NCP), low-density NCP (NCP<30 HU), calcified and total plaque volumes, and corresponding plaque burden (plaque volumex100%/vessel volume), stenosis, remodeling index, contrast density difference (maximum difference in luminal attenuation per unit area in the lesion), and plaque length. Quantitative stenosis, plaque burden, and myocardial mass were combined by boosted ensemble machine-learning algorithm into a composite risk score to predict impaired MFR (MFR⩽2.0) by PET in each artery. Nineteen patients had impaired regional MFR in at least 1 territory (41/153 vessels). Patients with impaired regional MFR had higher arterial NCP (32.4% versus 17.2%), low-density NCP (7% versus 4%), and total plaque burden (37% versus 19.3%, P<0.02). In multivariable analysis with 10-fold cross-validation, NCP burden was the most significant predictor of impaired MFR (odds ratio, 1.35; P=0.021 for all). For prediction of impaired MFR with 10-fold cross-validation, receiver operating characteristics area under the curve for the composite score was 0.83 (95% confidence interval, 0.79–0.91) greater than for quantitative stenosis (0.66, 95% confidence interval, 0.57–0.76, P=0.005). Conclusions—Compared with stenosis, arterial NCP burden and a composite score combining quantitative stenosis and plaque burden from CT angiography significantly improves identification of downstream regional vascular dysfunction.

Relationship of epicardial fat volume from noncontrast CT with impaired myocardial flow reserve by positron emission tomography

BACKGROUND Impaired myocardial flow reserve (MFR) is a marker of coronary vascular dysfunction with prognostic significance. OBJECTIVES We aimed to investigate the relationship between epicardial fat volume (EFV) measured from noncontrast CT and impaired MFR derived from rest-stress Rb-82 positron emission tomography (PET). METHODS We retrospectively studied 85 consecutive patients without known coronary artery disease who underwent rest-stress Rb-82 myocardial PET/CT and were subsequently referred for invasive coronary angiography. EFV was computed from noncontrast CT by validated software and indexed to body surface area (EFVi, cm3/m2). Global stress and rest MFR were automatically derived from PET. Patient age, sex, cardiovascular risk factors, coronary calcium score (CCS), and EFVi were combined by boosted ensemble machine learning algorithm into a novel composite risk score, using 10-fold cross-validation, to predict impaired global MFR (MFR ≤2.0) by PET. RESULTS Patients with impaired MFR (44 of 85; 52%) were older (71 vs. 65 years; P = .03) and had higher frequency of CCS (≥400; P = .02) with significantly higher EFVi (63.1 ± 20.4 vs. 51.3 ± 14.1 cm3/m2; P = .003). On multivariate logistic regression (with age, sex, number of risk factors, CCS, and EFVi), EFVi was the only independent predictor of impaired MFR (odds ratio, 7.39; P = .02). The machine learning composite risk score significantly improved risk reclassification of impaired MFR compared to CCS or EFVi alone (integrated discrimination improvement = 0.19; P = .007 and IDI = 0.22; P = .002, respectively). CONCLUSIONS Increased EFVi and composite risk score combining EFVi and CCS significantly improve identification of impaired global MFR by PET.

Aortic annulus eccentricity before and after transcatheter aortic valve implantation: Comparison of balloon-expandable and self-expanding prostheses

INTRODUCTION The geometry of the aortic annulus and implanted transcatheter aortic valve prosthesis might influence valve function. We investigated the influence of valve type and aortic valve calcification on post-implant geometry of catheter-based aortic valve prostheses. METHODS Eighty consecutive patients with severe aortic valve stenosis (mean age 82 ± 6 years) underwent computed tomography before and after TAVI. Aortic annulus diameters were determined. Influence of prosthesis type and degree of aortic valve calcification on post-implant eccentricity were analysed. RESULTS Aortic annulus eccentricity was reduced in patients after TAVI (0.21 ± 0.06 vs. 0.08 ± 0.06, p<0.0001). Post-TAVI eccentricity was significantly lower in 65 patients following implantation of a balloon-expandable prosthesis as compared to 15 patients who received a self-expanding prosthesis (0.06 ± 0.05 vs. 0.15 ± 0.07, p<0.0001), even though the extent of aortic valve calcification was not different. After TAVI, patients with a higher calcium amount retained a significantly higher eccentricity compared to patients with lower amounts of calcium. CONCLUSIONS Patients undergoing TAVI with a balloon-expandable prosthesis show a more circular shape of the implanted prosthesis as compared to patients with a self-expanding prosthesis. Eccentricity of the deployed prosthesis is affected by the extent of aortic valve calcification.

Prediction of fluoroscopic angulations for transcatheter aortic valve implantation by CT angiography: influence on procedural parameters.

Aims Repeated angiograms to achieve an exactly orthogonal visualization of the aortic valve plane can substantially contribute to the total contrast amount required for transcatheter aortic valve implantation (TAVI). We investigated whether pre-procedural identification of an optimal fluoroscopic projection by cardiac computed tomography (CT) can significantly reduce the amount of a procedure-related contrast agent compared with angiographic determination of suitable angulations. Methods and results Eighty consecutive patients (81 ± 5 years, 55% male) with symptomatic severe aortic valve stenosis and normal renal function who underwent cardiac CT prior to TAVI were prospectively randomized. In 40 patients, a CT-predicted suitable angulation was used for the first aortic angiogram (CT cohort); in the other 40 patients, the first aortogram was acquired at LAO 10°/cranial 10 (angiography cohort). Additional aortograms were performed if no satisfactory view of the aortic valve plane was obtained. The number of aortograms needed to achieve a satisfactory fluoroscopic projection (1.2 ± 0.6 vs. 3.2 ± 1.7; P < 0.001) and the total amount of contrast agent per TAVI procedure were significantly lower in the CT cohort (95 ± 21 vs. 125 ± 36 mL; P < 0.001). Incidence of acute kidney injury was not significantly different. There was no significant difference regarding radiation dose, time of procedure, degree of post-procedural aortic regurgitation, complications and 30-day mortality between the cohorts. Conclusion Pre-procedural identification of a suitable fluoroscopic projection by cardiac CT significantly reduces a procedural contrast agent volume required for TAVI.

MULTICENTER EVALUATION OF DUAL SOURCE CT CORONARY ANGIOGRAPHY IN PATIENTS WITH INTERMEDIATE LIKELIHOOD OF CORONARY ARTERY STENOSES (MEDIC): ACCURACY FOR THE DETECTION OF INDIVIDUALS WITH SIGNIFICANT CORONARY ARTERY STENOSES

Methods: In 6 international sites, 415 patients (30 to 80 years), scheduled for invasive coronary angiography due to suspected CAD, with intermediate likelihood of coronary stenoses (34% 73% based on age, gender, symptoms) were studied with dual source CT (DSCT) coronary angiography. Patients with renal failure, atrial fibrillation, or Agatston score >800 were excluded. Coronary CT angiography was performed without administration of beta blockers, using DSCT (Definition, Siemens Healthcare) in spiral mode, ECG-based tube current modulation and 100 kV tube voltage for patients < 90kg. Contrast agent (iopromide, Ultravist 370, Bayer Healthcare, 6 ml/s) was injected for duration of data acquisition, but at least 10 seconds. CT and quantitative coronary angiography (QCA) were evaluated in independent core laboratories. Stenoses > 50% lumen reduction in CT were correlated to QCA on a per-patient basis.