Value of Relative Myocardial Perfusion at MRI for Fractional Flow Reserve-Defined Ischemia: A Pilot Study.

OBJECTIVE. Correcting the perfusion in areas distal to coronary stenosis (risk) according to that of normal (remote) areas defines the relative myocardial perfusion index, which is similar to the fractional flow reserve (FFR) concept. The aim of this study was to assess the value of relative myocardial perfusion by MRI in predicting lesion-specific inducible ischemia as defined by FFR. MATERIALS AND METHODS. Forty-six patients (33 men and 13 women; mean [± SD] age, 61 ± 9 years) who underwent adenosine perfusion MRI and FFR measurement distal to 49 coronary artery stenoses during coronary angiography were retrospectively evaluated. Subendocardial time-enhancement maximal upslopes, normalized by the respective left ventricle cavity upslopes, were obtained in risk and remote subendocardium during adenosine and rest MRI perfusion and were correlated to the FFR values. RESULTS. The mean FFR value was 0.84 ± 0.09 (range, 0.60-0.98) and was less than or equal to 0.80 in 31% of stenoses (n = 15). The relative subendocardial perfusion index (risk-to-remote upslopes) during hyperemia showed better correlations with the FFR value (r = 0.59) than the uncorrected risk perfusion parameters (i.e., both the upslope during hyperemia and the perfusion reserve index [stress-to-rest upslopes]; r = 0.27 and 0.29, respectively). A cutoff value of 0.84 of the relative subendocardial perfusion index had an ROC AUC of 0.88 to predict stenosis at an FFR of less than or equal to 0.80. CONCLUSION. Using adenosine perfusion MRI, the relative myocardial perfusion index enabled the best prediction of FFR-defined lesion-specific myocardial ischemia. This index could be used to noninvasively determine the need for revascularization of known coronary stenoses.

Diagnostic performance of quantitative coronary computed tomography angiography and quantitative coronary angiography to predict hemodynamic significance of intermediate-grade stenoses.

Fractional flow reserve (FFR) during invasive coronary angiography has become an established tool for guiding treatment. However, only one-third of intermediate-grade coronary artery stenosis (ICAS) are hemodynamically significant and require coronary revascularization. Additionally, the severity of stenosis visually established by coronary computed tomography angiography (CCTA) does not reliably correlate with the functional severity. Therefore, additional angiographic morphologic descriptors affecting hemodynamic significance are required. To evaluate quantitative stenosis analysis and plaque descriptors by CCTA in predicting the hemodynamic significance of ICAS and to compare it with quantitative catheter coronary angiography (QCA). QCA was performed in 65 patients (mean age 63 ± 9 years; 47 men) with 76 ICAS (40-70%) on CCTA. Plaque descriptors were determined including circumferential extent of calcification, plaque composition, minimal lumen diameter (MLD) and area, diameter stenosis percentage (Ds %), area stenosis percentage and stenosis length on CCTA. MLD and Ds % were also analyzed on QCA. FFR was measured on 52 ICAS lesions on CCTA and QCA. The diagnostic values of the best CCTA and QCA descriptors were calculated for ICAS with FFR ≤ 0.80. Of the 76 ICAS on CCTA, 52 (68%) had a Ds % between 40 and 70% on QCA. Significant intertechnique correlations were found between CCTA and QCA for MLD and Ds % (p < 0.001). In 17 (33%) of the 52 ICAS lesions on QCA, FFR values were ≤ 0.80. Calcification circumference extent (p = 0.50) and plaque composition assessment (p = 0.59) did not correlate with the hemodynamic significance. Best predictors for FFR ≤ 0.80 stenosis were ≤ 1.35 mm MLD (82% sensitivity, 66% specificity), and ≤ 2.3 mm(²) minimal lumen area (88% sensitivity, 60% specificity) on CCTA, and ≤ 1.1 mm MLD (59% sensitivity, 77% specificity) on QCA. Quantitative CCTA and QCA poorly predict hemodynamic significance of ICAS, though CCTA seems to have a better sensitivity than QCA. In this range of stenoses, additional functional evaluation is required.

On the inappropriateness of noninvasive multidetector computed tomography coronary angiography to trigger coronary revascularization: a comparison with invasive angiography.

OBJECTIVES: Our purpose was to evaluate the appropriateness of multidetector computed tomography angiography (MDCTA) as an anatomical standard for decision making in patients with known or suspected coronary artery disease. BACKGROUND: Although correlative studies between MDCTA and coronary angiography (CA) show good agreement, MDCTA visualizes plaque burden and calcifications well before luminal dimensions are encroached. METHODS: Pressure-derived fractional flow reserve (FFR) was obtained in 81 patients (116 vessels) who underwent both CA and MDCTA. Segments were visually graded for stenosis severity as: G0 = normal, G1 = nonobstructive (<50% diameter reduction), and G2 = obstructive (> or =50% diameter reduction). RESULTS: Concordance between segmental severity scores by MDCTA and CA was good (k = 0.74; 95% confidence interval: 0.56 to 0.92). Diagnostic performance of MDCTA for detection of functionally significant stenosis based on FFR was low (sensitivity 79%; specificity 64%; positive likelihood ratio 2.2; negative likelihood ratio 0.3). Revascularization was considered appropriate in the presence of reduced FFR (< or =0.75). Decision making based on MDCTA guidance would result in revascularization in the absence of ischemia in 22% of patients (18 of 81) and inappropriate deferral in 7% (6 of 81), while revascularization in the absence of ischemia would be 16% (13 of 81) and inappropriate deferral 12% (10 of 81) with decisions guided by CA. Combined evaluation of stenosis severity using both anatomy (with either CA or MDCTA) and function (with FFR) yields the highest proportion of appropriate decisions: 90% and 91%, respectively (p = 0.0001 vs. CA only, p = 0.0001 vs. MDCTA only). CONCLUSIONS: Similar to CA, anatomical assessment of coronary stenosis severity by MDCTA does not reliably predict its functional significance.

Type 2 diabetes is associated with more advanced coronary atherosclerosis on multislice computed tomography and virtual histology intravascular ultrasound.

BACKGROUND: Data on coronary plaque observations on multi-slice computed tomography (MSCT) in patients with type 2 diabetes are scarce. METHODS AND RESULTS: In total, 60 patients (19 with diabetes) underwent 64-slice MSCT, followed by conventional coronary angiography with intravascular ultrasound (IVUS). Non-invasively, the extent of coronary atherosclerosis and 3 plaque types (non-calcified, calcified, mixed) were visually evaluated on MSCT. Invasively, plaque burden was assessed on gray-scale IVUS. Plaque composition was evaluated on virtual histology intravascular ultrasound (VH IVUS). Concerning geometrical plaque data, diabetic patients showed more plaques on MSCT (7.1 +/- 3.2 vs 4.9 +/- 3.2 in non-diabetic patients, P = .01). On gray-scale IVUS, diabetes was associated with a larger plaque burden (48.7 +/- 10.7% vs 40.0 +/- 12.1%, P = .003). Concerning plaque composition, diabetes was associated with more calcified plaques on MSCT (52% vs 24%). Relatively more fibrocalcific plaques in diabetic patients (29% versus 9%) were observed on VH IVUS. Moreover, these plaques contained more necrotic core (10.8 +/- 5.9% vs 8.6 +/- 5.2%, P = .01). CONCLUSION: A higher plaque extent and more calcified lesions were observed in diabetic patients on MSCT. The findings were confirmed on gray-scale and VH IVUS. Thus, MSCT may potentially be used to explore patterns of coronary atherosclerosis in diabetic patients.

Multidetector computed tomography angiography for assessment of in-stent restenosis: meta-analysis of diagnostic performance.

BACKGROUND: Multi-detector computed tomography angiography (MDCTA)of the coronary arteries after stenting has been evaluated in multiple studies.The purpose of this study was to perform a structured review and meta-analysis of the diagnostic performance of MDCTA for the detection of in-stent restenosis in the coronary arteries. METHODS: A Pubmed and manual search of the literature on in-stent restenosis (ISR) detected on MDCTA compared with conventional coronary angiography (CA) was performed. Bivariate summary receiver operating curve (SROC) analysis, with calculation of summary estimates was done on a stent and patient basis. In addition, the influence of study characteristics on diagnostic performance and number of non-assessable segments (NAP) was investigated with logistic meta-regression. RESULTS: Fourteen studies were included. On a stent basis, Pooled sensitivity and specificity were 0.82(0.72-0.89) and 0.91 (0.83-0.96). Pooled negative likelihood ratio and positive likelihood ratio were 0.20 (0.13-0.32) and 9.34 (4.68-18.62) respectively. The exclusion of non-assessable stents and the strut thickness of the stents had an influence on the diagnostic performance. The proportion of non-assessable stents was influenced by the number of detectors, stent diameter, strut thickness and the use of an edge-enhancing kernel. CONCLUSION: The sensitivity of MDTCA for the detection of in-stent stenosis is insufficient to use this test to select patients for further invasive testing as with this strategy around 20% of the patients with in-stent stenosis would be missed. Further improvement of scanner technology is needed before it can be recommended as a triage instrument in practice. In addition, the number of non-assessable stents is also high.

Evaluation of plaque characteristics in acute coronary syndromes: non-invasive assessment with multi-slice computed tomography and invasive evaluation with intravascular ultrasound radiofrequency data analysis.

AIMS: Atherosclerotic plaque characteristics play an important role in the development of coronary events. We investigated coronary plaque characteristics on multi-slice computed tomography (MSCT) and virtual histology intravascular ultrasound (VH IVUS) in patients with acute coronary syndromes (ACS) and stable coronary artery disease (CAD). METHODS AND RESULTS: Fifty patients (25 with ACS, 25 with stable CAD) underwent 64-slice MSCT followed by VH IVUS in 48 (96%) patients. In ACS patients, 32% of plaques were non-calcified on MSCT and 59% were mixed [corresponding odds ratio (95% confidence intervals): 3.9 (1.6-9.5), P = 0.003 and 3.4 (1.6-6.9), P = 0.001, respectively]. In patients with stable CAD, completely calcified lesions were more prevalent (61%). On VH IVUS, the percentage of necrotic core was higher in the plaques of ACS patients (11.16 +/- 6.07 vs. 9.08 +/- 4.62% in stable CAD, P = 0.02). In addition, thin cap fibroatheroma was more prevalent in ACS patients (32 vs. 3% in patients with stable CAD, P < 0.001) and was most frequently observed in mixed plaques on MSCT. Plaque composition both on MSCT and VH IVUS was identical between culprit and non-culprit vessels of ACS patients. CONCLUSION: On MSCT, differences in plaque characterization were demonstrated between patients with ACS and stable CAD. Plaques of ACS patients showed features of vulnerability to rupture on VH IVUS. Potentially, MSCT may be useful for non-invasive identification of atherosclerotic plaque patterns associated with higher risk.

Head-to-head comparison of coronary plaque evaluation between multislice computed tomography and intravascular ultrasound radiofrequency data analysis.

OBJECTIVES: The purpose of this study was to perform a head-to-head comparison of plaque observations with multislice computed tomography (MSCT) to virtual histology intravascular ultrasound (VH IVUS). BACKGROUND: The VH IVUS allows in vivo coronary plaque characterization with high spatial resolution. Noninvasively, plaques may be evaluated with MSCT, but limited data are available. METHODS: A total of 50 patients underwent 64-slice MSCT followed by VH IVUS. The Agatston score was evaluated on MSCT in coronary segments where IVUS was performed. Plaques were classified on MSCT as noncalcified, mixed, and calcified. Four plaque components (fibrotic, fibro-fatty, and necrotic core tissues and dense calcium) were identified on VH IVUS, and the presence of thin-cap fibroatheroma was evaluated. RESULTS: A moderate correlation was observed between the Agatston score and calcium volume on VH IVUS (r = 0.69, p < 0.0001). In total, 168 coronary plaques were evaluated (48 [29%] noncalcified, 71 [42%] mixed, 49 [29%] calcified). As compared with calcified plaques, noncalcified plaques contained more fibrotic (60.90 +/- 9.21% vs. 54.60 +/- 8.33%, p = 0.001) and fibro-fatty tissues (28.11 +/- 13.03% vs. 21.37 +/- 9.75%, p = 0.006) on VH IVUS. Mixed and calcified plaques contained more dense calcium (7.61 +/- 8.94% vs. 2.68 +/- 3.01%, p = 0.001; 10.18 +/- 6.71% vs. 2.68 +/- 3.01%, p < 0.0001, respectively). Thin-cap fibroatheromas were most frequently observed in mixed plaques as compared with noncalcified and calcified plaques (32%, 13%, 8%, p = 0.002, respectively). CONCLUSIONS: A good correlation was observed between calcium quantification on MSCT and VH IVUS. In addition, plaque classification on MSCT paralleled relative plaque composition on VH IVUS, although VH IVUS provided more precise plaque characterization. Mixed plaques on MSCT were associated with high-risk features on VH IVUS.

Effects of sublingual nitroglycerin on coronary lumen diameter and number of visualized septal branches on 64-MDCT angiography.

OBJECTIVE: This article describes the influence of sublingual nitroglycerin spray on the lumen diameter, number of side branches visualized, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) of the coronary arteries with MDCT angiography. SUBJECTS AND METHODS: Forty-two patients were prospectively included in this study: 21 were examined without sublingual nitroglycerin (group A), and 21 were examined after the administration of sublingual nitroglycerin (group B). CT angiography was performed using a 64-MDCT scanner. Two blinded observers quantitatively assessed lumen diameter and volume in the left anterior descending artery (LAD) and the right coronary artery (RCA). The number of septal branches was counted. The SNR and CNR in the LAD and RCA were calculated in both groups. The number of clinical side effects was evaluated. RESULTS: The lumen diameters and the average volumes were significantly larger in group B than in group A. The number of septal branches visualized in group B was significantly higher than in group A. No statistically significant difference in SNR and CNR between the groups was shown. The number of side effects in the two groups was not significantly different. CONCLUSION: Sublingual nitroglycerin spray significantly dilates the coronary arteries and allows more septal branches to be visualized at coronary CT angiography without diminishing image quality or increasing the number of side effects.

Detection of non-ST-elevation myocardial infarction and unstable angina in the acute setting: meta-analysis of diagnostic performance of multi-detector computed tomographic angiography.

BACKGROUND: Multi-detector computed tomography angiography (MDCTA) has been increasingly used in the evaluation of the coronary arteries. The purpose of this study was to review the literature on the diagnostic performance of MDCTA in the acute setting, for the detection of non-ST-elevation myocardial infarction (NSTEMI) and unstable angina pectoris (UAP). METHODS: A Pubmed and manual search of the literature published between January 2000 and June 2007 was performed. Studies were included that compared MDCTA with clinical outcome and/or CA in patients with acute chest pain, presenting at the emergency department. More specifically, studies that only included patients with initially negative cardiac enzymes suspected of having NSTEMI or UAP were included. Summary estimates of diagnostic odds ratio (DOR), sensitivity and specificity, negative (NLR) and positive likelihood ratio (PLR) were calculated on a patient basis. Random-effects models and summary receiver operating curve (SROC) analysis were used to assess the diagnostic performance of MDCTA with 4 detectors or more. The proportion of non assessable scans (NAP) on MDCTA was also evaluated. In addition, the influence of study characteristics of each study on diagnostic performance and NAP was investigated with multivariable logistic regression. RESULTS: Nine studies totalling 566 patients, were included in the meta-analysis: one randomised trial and eight prospective cohort studies. Five studies on 64-detector MDCTA and 4 studies on MDCTA with less than 64 detectors were included (32 detectors n = 1, 16 detectors n = 2, 16 and 4 detectors n = 1). Pooled DOR was 131.81 (95%CI, 50.90-341.31). The pooled sensitivity and specificity were 0.95 (95%CI, 0.90-0.98) and 0.90 (95%CI, 0.87-0.93). The pooled NLR and PLR were 0.12 (95%CI, 0.06-0.21) and 8,60 (95%CI, 5.03-14,69).The results of the logistic regressions showed that none of the investigated variables had influence on the diagnostic performance or NAP CONCLUSION: MDCTA of the coronary arteries performs good to excellent in the diagnosis of coronary artery disease in the acute setting and it can be used for early exclusion of NSTEMI or UAP in patients in the emergency department.

Diagnostic performance of multidetector CT angiography for assessment of coronary artery disease: meta-analysis.

PURPOSE: To review the literature on the diagnostic performance of multidetector computed tomographic (CT) angiography for assessment of symptomatic coronary artery disease, with conventional coronary angiography as the reference standard. MATERIALS AND METHODS: A PubMed and manual search of the literature published between January 1998 and May 2006 on use of multidetector CT angiography compared with coronary angiography in patients with symptomatic coronary artery disease was performed. Summary estimates of diagnostic odds ratio, sensitivity, and specificity were calculated. Random-effects models were used to compare the diagnostic performance of four-, 16-, and 64-detector CT angiographic units, and the proportion of nonassessable coronary arterial segments was evaluated. RESULTS: Fifty-four studies were included in the meta-analysis: 22 studies with four-detector CT angiography, 26 with 16-detector CT angiography, and six with 64-detector CT angiography. The pooled sensitivity and specificity for detecting a greater than 50% stenosis per segment were 0.93 (95% confidence interval [CI]: 0.88, 0.97) and 0.96 (95% CI: 0.96, 0.97) for 64-detector CT angiography, 0.83 (95% CI: 0.76, 0.90) and 0.96 (95% CI: 0.95, 0.97) for 16-detector CT angiography, and 0.84 (95% CI: 0.81, 0.88) and 0.93 (95% CI: 0.91, 0.95) for four-detector CT angiography, respectively. Results of regression analysis indicated that the diagnostic performance significantly improved with the newer generations of multidetector CT scanners (64- and 16-detector vs four-detector units), adjusted for exclusion of nonassessable segments, and contrast agent concentration used (P < .05). Simultaneously, the nonassessable proportion of segments significantly decreased with the newer generations of multidetector CT scanners, adjusted for heart rate, prevalence of significant disease, and mean age. CONCLUSION: With the newer generations of multidetector CT scanners, the diagnostic performance for the assessment of coronary artery disease has significantly improved, and the proportion of nonassessable segments has decreased.

What does the clinical cardiologist need from noninvasive cardiac imaging: is it time to adjust practices to meet evolving demands?

With the recent emergence of multidetector computed tomography angiography, coronary anatomy can now be assessed noninvasively. Until this advancement, functional noninvasive imaging used to serve as a gatekeeper that governed access to invasive diagnosis by coronary angiography and subsequent therapy. In the current era the threshold for access to coronary anatomy will be lowered. Functional noninvasive imaging will often come second, while anatomy is known already. If appropriate use of revascularization procedures is to be promoted, functional evaluation shall play an even greater role than before as a guide for selection of therapy. In subjects screened while the atherosclerotic disease is still at a preclinical stage, the ability to image plaque activity in the absence of flow-limiting stenosis will be essential in our attempts to prevent sudden ischemic cardiac death and unheralded myocardial infarction. In patients with advanced age and extensive obstructive disease, the diagnostic performance of functional testing will have to be raised by shifting from "per-patient" to "per-vessel" accuracy. Reengineering of currently available methods or the development of novel technologies that provide an integrative evaluation of anatomy and function will be necessary. With the availability of an increasing number of imaging options, it is anticipated that the emphasis will be placed more than ever on cost-effectiveness on a population basis, as well as on segmental predictive accuracy in the individual subject.

A simple method to estimate cardiac function during routine multi-row detector CT exams.

Cardiac dysfunction may be suggested at computed tomography (CT) exams by the presence of morphological abnormalities such as cardiac enlargement and thickening of the pulmonary interlobular septa. However, these morphological signs are non specific. We evaluated whether right-to-left cardiac transit time of contrast during single-level timing scans could predict the cardiac output and ejection fraction. In a consecutive group of 100 patients referred for body CT, a preliminary single-level study was used to measure the right-to-left ventricular transit time of intravenously injected contrast medium. In all these patients, the cardiac index (cardiac output corrected for body surface area, CI) and ejection fraction (EF) were calculated using cardiac magnetic resonance imaging (CMR). Data of the first half (50 patients, group A) were used to establish a method and concept to predict the cardiac index and ejection fraction with CT. The method was validated in the next half (50 patients, group B) by comparing the predicted CT results with those obtained with CMR. There was a good correlation of the observed CI with CMR and observed transit time on CT in group B (P < 0.05; R(2) 0.70 ). Functional CT estimates of CI and EF in group B correlated well with the CMR results for CI and EF (P < 0.05; R(2) 0.66 for CI and P < 0.05; R(2) 0.49 for EF). The presence of a right-to-left ventricular transit time of more than 10.5 s indicated cardiac dysfunction with a specificity and positive predictive value of 100%. Right-to-left transit time obtained during routine body CT exams can provide valuable physiological information on global cardiac function.

Relationship between noninvasive coronary angiography with multi-slice computed tomography and myocardial perfusion imaging.

OBJECTIVES: The aim of this study was to perform a head-to-head comparison between multi-slice computed tomography (MSCT) and myocardial perfusion imaging (MPI) in patients with an intermediate likelihood of coronary artery disease (CAD) and to compare non-invasive findings to invasive coronary angiography. BACKGROUND: Multi-slice computed tomography detects atherosclerosis, whereas MPI detects ischemia; how these 2 techniques compare in patients with an intermediate likelihood of CAD is unknown. METHODS: A total of 114 patients, mainly with intermediate likelihood of CAD, underwent both MSCT and MPI. The MSCT studies were classified as having no CAD, nonobstructive (<50% luminal narrowing) CAD, or obstructive CAD. Myocardial perfusion imaging examinations were classified as showing normal or abnormal (reversible and/or fixed defects). In a subset of 58 patients, invasive coronary angiography was performed. RESULTS: On the basis of the MSCT data, 41 patients (36%) were classified as having no CAD, of whom 90% had normal MPI. A total of 33 patients (29%) showed non-obstructive CAD, whereas at least 1 significant (> or =50% luminal narrowing) lesion was observed in the remaining 40 patients (35%). Only 45% of patients with an abnormal MSCT had abnormal MPI; even in patients with obstructive CAD on MSCT, 50% still had a normal MPI. In the subset of patients undergoing invasive angiography, the agreement with MSCT was excellent (90%). CONCLUSIONS: Myocardial perfusion imaging and MSCT provide different and complementary information on CAD, namely, detection of atherosclerosis versus detection of ischemia. As compared to invasive angiography, MSCT has a high accuracy for detecting CAD in patients with an intermediate likelihood of CAD.

Three-dimensional venography of the brain with a volumetric interpolated sequence.

Informed consent was obtained from all patients before participation; study was approved by institutional review board. Three-dimensional (3D) gradient-echo magnetic resonance sequences can be optimized for rapid acquisition through asymmetric k-space sampling and interpolation of image data. A T1-weighted volumetric interpolated brain examination sequence (acquisition time, 1 minute 24 seconds) was prospectively compared qualitatively and quantitatively with magnetization-prepared rapid acquisition gradient-echo sequence (acquisition time, 6 minutes 6 seconds) for venography of cerebral venous structures in 21 female and seven male consecutive patients (mean age, 52.9 years; range, 16-81 years). Although signal- and contrast-to-noise ratios were substantially lower for volumetric interpolated sequence, difference in the subjective quality of visualization of cerebral venous structures was not significant (P >.05). Volumetric interpolated brain examination seems promising as a more time-efficient alternative for 3D imaging of cerebral venous structures.

Coronary artery calcium scoring using ECG-gated multidetector CT: effect of individually optimized image-reconstruction windows on image quality and measurement reproducibility.

OBJECTIVE: We studied the effect of using individually optimized image-reconstruction windows on image quality and measurement reproducibility in coronary artery calcium scoring using ECG-gated multidetector CT (MDCT). SUBJECTS AND METHODS: In 50 patients, the coronary arteries were investigated twice with ECG-gated MDCT with 500-msec rotation time. Per scan, three sets of images were reconstructed, respectively, at an image-reconstruction window of 40%, 50%, and 60% of the R-R interval. Image quality was assessed, and the optimal image-reconstruction window per scan and per coronary territory was determined. The interscan variability of calcium mass measurements was calculated for different strategies (use of fixed image-reconstruction window [40%, 50%, or 60%] versus individually optimized image-reconstruction window). RESULTS: A significant improvement in image quality was obtained by selecting the best of three reconstructed data sets (mean image quality score, 4.4 vs 3.7; p < 0.001). Even with individually optimized image-reconstruction window values, we obtained high values for interscan variability (mean +/- SD, 27% +/- 22% vs 31% +/- 35% with a fixed image-reconstruction window). CONCLUSION: The use of individually optimized image-reconstruction windows leads to a significant improvement in image quality. However, interscan variability of calcium mass measurements remains high.