Comparison of Multidetector-Row Computed Tomography to Echocardiography and Fluoroscopy for Evaluation of Patients with Mechanical Prosthetic Valve Obstruction

OBJECTIVES: For evaluation of prosthetic heart valve obstruction echocardiography and fluoroscopy provide primarily functional information, but may not unequivocally establish the cause of dysfunction. Our objective was to evaluate whether multidetector-row computed tomographic (MDCT) imaging could detect the morphologic substrate for such functional abnormalities.

METHODS: Thirteen patients with 15 prosthetic valves, in whom prosthetic valve obstruction was suspected from echocardiography or fluoroscopy, but no sufficient cause could be found, underwent electrocardiographically gated multidetector-row computed tomography. MDCT data were retrospectively reconstructed at every 10% of the electrocardiographic interval and analyzed using multiplanar reformatting in anatomically adapted planes. MDCT images were evaluated for morphologic prosthetic and periprosthetic abnormalities.

RESULTS: Results could be compared to intraoperative findings or autopsy in 7 patients. Multidetector-row computed tomography disclosed a morphologic substrate for obstruction in 8 of 13 patients. MDCT findings compatible with obstruction were confirmed at surgery or autopsy in 6 patients. In a seventh patient, incomplete leaflet closure found with multidetector-row computed tomography was confirmed at surgery. The most commonly identified causes for obstruction were subprosthetic tissue (6 patients) and abnormal anatomic orientation (3 patients). Despite an indication for surgery, 2 patients were not operated on due to recurrent bacteremias and prohibitive co-morbidity. Multidetector-row computed tomography detected leaflet motion restriction in 7 patients compared to 4 by fluoroscopy. Confirmation of leaflet restriction was available in 5 patients. Multidetector-row computed tomography missed a periprosthetic leak.

CONCLUSIONS: In conclusion, this initial experience demonstrates that multidetector-row computed tomography can identify causes of prosthetic valve obstruction that constitute indications for surgery, but are missed at echocardiography or fluoroscopy.

PMID: 19801036

Quantification of Functional Mitral Regurgitation by Real-Time 3D Echocardiography: Comparison With 3D Velocity-Encoded Cardiac Magnetic Resonance

OBJECTIVES: The aim of this study was to evaluate feasibility and accuracy of real-time 3-dimensional (3D) echocardiography for quantification of mitral regurgitation (MR), in a head-to-head comparison with velocity-encoded cardiac magnetic resonance (VE-CMR). Background: Accurate grading of MR severity is crucial for appropriate patient management but remains challenging. VE-CMR with 3D three-directionalacquisition has been recently proposed as the reference method.

METHODS: A total of 64 patients with functional MR were included. A VE-CMR acquisition was applied to quantify mitral regurgitant volume (Rvol). Color Doppler 3D echocardiography was applied for direct measurement, in “en face” view, of mitral effective regurgitant orifice area (EROA); Rvol was subsequently calculated as EROA multiplied by the velocity-time integral of the regurgitant jet on the continuous-wave Doppler. To assess the relative potential error of the conventional approach, color Doppler 2-dimensional (2D) echocardiography was performed: vena contracta width was measured in the 4-chamber view and EROA calculated as circular (EROA-4CH); EROA was also calculated as elliptical (EROA-elliptical), measuring vena contracta also in the 2-chamber view. From these 2D measurements of EROA, the Rvols were also calculated.

RESULTS: The EROA measured by 3D echocardiography was significantly higher than EROA-4CH (p < 0.001) and EROA-elliptical (p < 0.001), with a significant bias between these measurements (0.10 cm² and 0.06 cm², respectively). Rvol measured by 3D echocardiography showed excellent correlation with Rvol measured by CMR (r = 0.94), without a significant difference between these techniques (mean difference = –0.08 ml/beat). Conversely, 2D echocardiographic approach from the 4-chamber view significantly underestimated Rvol (p = 0.006) as compared with CMR (mean difference = 2.9 ml/beat). The 2D elliptical approach demonstrated a better agreement with CMR (mean difference = –1.6 ml/beat, p = 0.04).

CONCLUSIONS: Quantification of EROA and Rvol of functional MR with 3D echocardiography is feasible and accurate as compared with VE-CMR; the currently recommended 2D echocardiographic approach significantly underestimates both EROA and Rvol.

PMID:

Stent Gap by 64-Detector Computed Tomographic Angiography: Relationship to In-Stent Restenosis, Fracture, and Overlap Failure

OBJECTIVES: The goal of this study was to define the frequency of stent gaps by 64-detector computed tomographic angiography (CTA) and their relation to in-stent restenosis (ISR), stent fracture (SF), and overlap failure (OF). Background: SF defined by catheter angiography or intravascular ultrasound has been implicated in ISR.

METHODS: A total of 292 consecutive patients, with 613 stents, who underwent CTA were evaluated for stent gaps associated with decreased Hounsfield units. Correlations with catheter coronary angiography (CCA) were available in 143 patients with 384 stents.

RESULTS: Stent gaps were noted in 16.9% by CTA and 1.0% by CCA. ISR by CCA was noted in 46.1% of the stent gaps (p < 0.001) as determined by CCA, and stent gaps by CTA accounted for 27.8% of the total ISR (p < 0.001). In univariate analysis, stent diameter ≥3 mm was the only CCA characteristic significantly associated with stent gaps (p = 0.002), but was not a significant predictor by multivariate analysis. Bifurcation stents, underlying calcification, stent type, location, post-dilation, and overlapping stents were not observed to be predisposing factors. Excessive tortuosity and lack of conformability were not associated with stent gaps; however, their frequency was insufficient to permit meaningful analysis.

CONCLUSIONS: Stent gap by CTA: 1) is associated with 28% of ISR, and ISR is found in 46% of stent gaps; 2) is associated with ≥3 mm stents by univariate (p = 0.002) but not by multivariate analysis; 3) is infrequently noted on catheter angiography; and 4) most likely represents SF in the setting of a single stent, and may represent SF or OF in overlapping stents.

PMID: 19909876

Coronary Computed Tomography Angiography with a Consistent Dose Below 1 mSv using Prospectively Electrocardiogram-Triggered High-Pitch Spiral Acquisition

OBJECTIVES: We evaluated the feasibility and image quality of a new scan mode for coronary computed tomography angiography (CTA) with an effective dose of less than 1 mSv.

METHODS: In 50 consecutive patients (body weight <100 kg, sinus rhythm <60 b.p.m. after pre-medication, coronary CTA was performed using a dual-source CT system with 2 x 128 x 0.6 mm collimation, 0.28 s rotation time, a pitch of 3.2 or 3.4, 100 kV tube voltage and current of 320 mA s. Data acquisition was prospectively triggered at 60% of the R-R interval and completed within one cardiac cycle. Image quality was evaluated using a four-point scale (1 = absence of any artefacts to 4 = uninterpretable).

RESULTS: In all 50 patients, imaging was successful. Mean duration of data acquisition was 258 +/- 20 ms. Mean dose-length product was 62 +/- 5 mGy cm, the effective dose was 0.87 +/- 0.07 mSv (0.78-0.99 mSv). Of the 742 coronary artery segments, 94% had an image quality score of 1, 5.0% a score of 2, 0.9% a score of 3, and 4 segments (0.5%) were “uninterpretable.”

CONCLUSIONS: In non-obese patients with a low and stable heart rate, prospectively ECG-triggered high-pitch spiral coronary CTA provides excellent image quality at a consistent dose below 1.0 mSv.

PMID: 19897497

Interventricular Mechanical Dyssynchrony: Quantification with Velocity-encoded MR Imaging

OBJECTIVES: To evaluate the performance of velocity-encoded (VENC) magnetic resonance (MR) imaging, as compared with pulsed-wave echocardiography (PW-ECHO), in the quantification of interventricular mechanical dyssynchrony (IVMD) as a predictor of response to cardiac resynchronization therapy (CRT).

METHODS:  The study was approved by the local ethics committee, and all patients provided written informed consent. The study involved the examination of 45 patients (nine women, 36 men; median age, 60 years; interquartile age range, 47–69 years) with New York Heart Association class 2.0–3.0 heart failure and a reduced left ventricular ejection fraction (median, 25%; interquartile range, 21%–32%), with (n = 25) or without (n = 20) left bundle branch block. Aortic and pulmonary flow curves were constructed by using VENC MR imaging and PW-ECHO. IVMD was defined as the difference between the onset of aortic flow and the onset of pulmonary flow. Intraclass correlation coefficient, Spearman correlation coefficient, Bland-Altman, and Cohen κ analyses were used to assess agreement between observers and methods.

RESULTS: Inter- and intraobserver agreement regarding VENC MR imaging IVMD measurements was very good (intraclass r = 0.96, P < .001; mean bias, −3 msec ± 11 [standard deviation] and 0 msec ± 10, respectively). A strong correlation (Spearman r = 0.92, P < .001) and strong agreement (mean difference, −6 msec ± 16) were found between VENC MR imaging and PW-ECHO in the quantification of IVMD. Agreement between VENC MR imaging and PW-ECHO in the identification of potential responders to CRT was excellent (Cohen κ = 0.94).

CONCLUSIONS: VENC MR measurements of IVMD are equivalent to PW-ECHO measurements and can be used to identify potential responders to CRT.

PMID: 19703849

Prognostic Significance of Delayed-Enhancement Magnetic Resonance Imaging. Survival of 857 Patients With and Without Left Ventricular Dysfunction

OBJECTIVES:  Left ventricular ejection fraction is a powerful independent predictor of survival in cardiac patients, especially those with coronary artery disease. Delayed-enhancement magnetic resonance imaging (DE-MRI) can accurately identify irreversible myocardial injury with high spatial and contrast resolution. To date, relatively limited data are available on the prognostic value of DE-MRI, so we sought to determine whether DE-MRI findings independently predict survival.

METHODS:  The medical records of 857 consecutive patients who had complete cine and DE-MRI evaluation at a tertiary care center were reviewed regardless of whether the patients had coronary artery disease. The presence and extent of myocardial scar were evaluated qualitatively by a single experienced observer. The primary, composite end point was all-cause mortality or cardiac transplantation. Survival data were obtained from the Social Security Death Index.

RESULTS:  The median follow-up was 4.4 years; 252 patients (29%) reached one of the end points. Independent predictors of mortality or transplantation included congestive heart failure, ejection fraction, and age (P<0.0001 for each), as well as scar index (hazard ratio, 1.26; 95% confidence interval, 1.02 to 1.55; P=0.033). Similarly, in subsets of patients with or without coronary artery disease, scar index also independently predicted mortality or transplantation (hazard ratio, 1.33; 95% confidence interval, 1.05 to 1.68; P=0.018; and hazard ratio, 5.65; 95% confidence interval, 1.74 to 18.3; P=0.004, respectively). Cox regression analysis showed worse outcome in patients with any DE in addition to depressed left ventricular ejection fraction (<50%).

CONCLUSION:  The degree of DE detected by DE-MRI appears to strongly predict all-cause mortality or cardiac transplantation after adjustment for traditional, well-known prognosticators.

PMID: 19901193

Helical Prospective ECG-Gating in Cardiac Computed Tomography: Radiation Dose and Image Quality

OBJECTIVES: Helical prospective ECG-gating (pECG) may reduce radiation dose while maintaining the advantages of helical image acquisition for coronary computed tomography angiography (CCTA). Aim of this study was to evaluate helical pECG-gating in CCTA in regards to radiation dose and image quality.

METHODS: 86 patients undergoing 64-multislice CCTA were enrolled. pECG-gating was performed in patients with regular heart rates (HR) < 65 bpm; with the gating window set at 70-85% of the cardiac cycle. All patients received oral and some received additional IV beta-blockers to achieve HR < 65 bpm. In patients with higher or irregular HR, or for functional evaluation, retrospective ECG-gating (rECG) was performed. The average X-ray dose was estimated from the dose length product. Each arterial segment (modified AHA/ACC 17-segment-model) was evaluated on a 4-point image quality scale (4 = excellent; 3 = good, mild artefact; 2 = acceptable, some artefact, 1 = uninterpretable).

RESULTS: pECG-gating was applied in 57 patients, rECG-gating in 29 patients. There was no difference in age, gender, body mass index, scan length or tube output settings between both groups. HR in the pECG-group was 54.7 bpm (range, 43-64). The effective radiation dose was significantly lower for patients scanned with pECG-gating with mean 6.9 mSv +/- 1.9 (range, 2.9-10.7) compared to rECG with 16.9 mSv +/- 4.1 (P < 0.001), resulting in a mean dose reduction of 59.2%. For pECG-gating, out of 969 coronary segments, 99.3% were interpretable. Image quality was excellent in 90.2%, good in 7.8%, acceptable in 1.3% and non-interpretable in 0.7% (n = 7 segments).

CONCLUSIONS: For patients with steady heart rates <65 bpm, helical prospective ECG-gating can significantly lower the radiation dose while maintaining high image quality.

PMID: 19898955

Assessment of Coronary Plaque Progression in Coronary Computed Tomography Angiography Using a Semiquantitative Score

OBJECTIVES: We sought to describe the progression of coronary atherosclerotic plaque over time by computed tomography (CT) angiography stratified by plaque composition and its association with cardiovascular risk profiles. Background: Data on the progression of atherosclerosis stratified by plaque composition with the use of noninvasive assessment by CT are limited and hampered by high measurement variability.

METHODS: This analysis included patients who presented with acute chest pain to the emergency department but initially showed no evidence of acute coronary syndromes. All patients underwent contrast-enhanced 64-slice CT at baseline and after 2 years with the use of a similar protocol. CT datasets were coregistered and assessed for the presence of calcified and noncalcified plaque at 1 mm cross sections of the proximal 40 mm of each major coronary artery. Plaque progression over time and its association with risk factors were determined. Measurement reproducibility and correlation to plaque volume was performed in a subset of patients.

RESULTS: We included 69 patients (mean age 55 ± 12 years, 59% male patients) and compared 8,311 coregistered cross sections at baseline and follow-up. At baseline, any plaque, calcified plaque, and noncalcified were detected in 12.5%, 10.1%, and 2.4% of cross sections per patient, respectively. There was significant progression in the mean number of cross sections containing any plaque (16.5 ± 25.3 vs. 18.6 ± 25.5, p = 0.01) and noncalcified plaque (3.1 ± 5.8 vs. 4.4 ± 7.0, p = 0.04) but not calcified plaque (13.3 ± 23.1 vs. 14.2 ± 22.0, p = 0.2). In longitudinal regression analysis, the presence of baseline plaque, number of cardiovascular risk factors, and smoking were independently associated with plaque progression after adjustment for age, sex, and follow-up time interval. The semiquantitative score based on cross sections correlated closely with plaque volume progression (r = 0.75, p < 0.0001) and demonstrated an excellent intraobserver and interobserver agreement ( kappa= 0.95 and kappa= 0.93, respectively).

CONCLUSIONS: Coronary plaque burden of patients with acute chest pain significantly increases during the course of 2 years. Progression over time is dependent on plaque composition and cardiovascular risk profile. Larger studies are needed to confirm these results and to determine the effect of medical treatment on progression.

PMID: 19909929

Cardiac MR Elastography: Comparison with left ventricular pressure measurement

OBJECTIVES:  To compare magnetic resonance elastography (MRE) with ventricular pressure changes in an animal model.

METHODS:  Three pigs of different cardiac physiology (weight, 25 to 53 kg; heart rate, 61 to 93 bpm; left ventricular [LV] end-diastolic volume, 35 to 70 ml) were subjected to invasive LV pressure measurement by catheter and noninvasive cardiac MRE. Cardiac MRE was performed in a short-axis view of the heart and applying a 48.3-Hz shear-wave stimulus. Relative changes in LV-shear wave amplitudes during the cardiac cycle were analyzed. Correlation  coefficients between  wave  amplitudes  and  LV  pressure  as  well  as  between  wave  amplitudes  and  LV diameter were determined.

RESULTS:  A relationship between MRE and LV pressure was observed in all three animals (R2  0.76). No correlation was observed between MRE and LV diameter (R2 [1] 0.15). Instead, shear wave amplitudes  decreased  102  ±  58  ms  earlier  than  LV  diameters  at  systole  and  amplitudes increased 175 ± 40 ms before LV dilatation at diastole. Amplitude ratios between diastole and systole ranged from 2.0 to 2.8, corresponding to LV pressure differences of 60 to 73 mmHg.

CONCLUSIONS:  Externally induced shear waves provide information reflecting intraventricular pressure changes which, if substantiated in further experiments, has potential to make cardiac MRE a unique noninvasive imaging modality for measuring pressure-volume function of the heart.

PMID: 19900266

Comparison of dual source computed tomography versus intravascular ultrasound for evaluation of coronary arteries at least one year after cardiac transplantation

OBJECTIVES: This study evaluated the ability of dual-source computed tomography (DSCT) to detect coronary allograft vasculopathy (CAV) in heart transplant recipients using intravascular ultrasound (IVUS) as the standard of reference.

METHODS: Thirty patients with heart transplants (81% men, mean age 40 years) underwent DSCT (330-ms gantry rotation, 2 x 64 x 0.6-mm collimation, 60- to 80-ml contrast agent, no additional beta blockers) before invasive coronary angiography including IVUS of 1 vessel. Detection of CAV by DSCT was qualitatively defined as the presence of any coronary plaque.

RESULTS: Mean heart rate during dual-source computed tomographic scanning was 80 +/- 14 beats/min. Four hundred fifty-nine segments with a vessel caliber >1.5 mm according to quantitative coronary angiography were evaluated in 30 patients. Of these, 96% were considered to have excellent or good image quality. IVUS detected CAV in 17 of 30 patients (57%) and in 41 of 110 coronary segments (37%). Compared to IVUS, sensitivity, specificity, positive and negative predictive values for the detection of CAV by DSCT were 85%, 84%, 76%, and 91%, respectively.

CONCLUSION: In conclusion, DSCT permits the investigation of transplant recipients concerning the presence of CAV with good image quality and high diagnostic accuracy.

PMID: 19892049

The Coronary Artery Calcium Score and Stress Myocardial Perfusion Imaging Provide Independent and Complementary Prediction of Cardiac Risk

OBJECTIVES: This study sought to examine the relationship between coronary artery calcium score (CACS) and single-photon emission computed tomography (SPECT) results for predicting the short- and long-term risk of cardiac events. Background: The CACS and SPECT results both provide important prognostic information. It is unclear whether integrating these tests will better predict patient outcome.

METHODS: We followed-up 1,126 generally asymptomatic subjects without previous cardiovascular disease who had a CACS and stress SPECT scan performed within a close time period (median 56 days). The median follow-up was 6.9 years. End points analyzed were total cardiac events and all-cause death/myocardial infarction (MI).

RESULTS: An abnormal SPECT result increased with increasing CACS from <1% (CACS≤10) to 29% (CACS >400) (p < 0.001). Total cardiac events and death/MI also increased with increasing CACS and abnormal SPECT results (p < 0.001). In subjects with a normal SPECT result, CACS added incremental prognostic information, with a 3.55-fold relative increase for any cardiac event (2.75-fold for death/MI) when the CACS was severe (>400) versus minimal (≤10). Separation of the survival curves occurred at 3 years after initial testing for all cardiac events and at 5 years for death/MI.

CONCLUSIONS: The CACS and SPECT findings are independent and complementary predictors of short- and long-term cardiac events. Despite a normal SPECT result, a severe CACS identifies subjects at high long-term cardiac risk. After a normal SPECT result, our findings support performing a CACS in patients who are at intermediate or high clinical risk for coronary artery disease to better define those who will have a high long-term risk for adverse cardiac events.

PMID:

Factors Affecting Sensitivity and Specificity of Diagnostic Testing: Dobutamine Stress Echocardiography

OBJECTIVES: Clinical characteristics of patients, angiographic referral bias, and several technical factors may all affect the reported diagnostic accuracy of tests. The aim of this study was to assess their influence on the diagnostic accuracy of dobutamine stress echocardiography (DSE).

METHODS: The medical literature from 1991 to 2006 was searched for diagnostic studies using DSE and meta-analysis was applied to the 62 studies thus retrieved, including 6881 patients. These studies were analyzed for patient characteristics, angiographic referral bias, and several technical factors.

RESULTS: The sensitivity of DSE was significantly related to the inclusion of patients with prior myocardial infarctions (0.834 vs 0.740, P < .01) and defining the results of DSE as already positive in case of resting wall motion abnormalities rather than obligatory myocardial ischemia (0.786 vs 0.864, P < .01). Specificity tended to be lower when patients with resting wall motion abnormalities were included in a study (0.812 vs 0.877, P < .10). The presence of referral bias adversely affected the specificity of DSE (0.771 vs 0.842, P < .01).

CONCLUSIONS: This analysis suggests that the reported sensitivity of DSE is likely higher and the specificity lower than expected in routine clinical practice because of the inappropriate inclusion of patients with prior myocardial infarctions, the definition of positive results on DSE, and the negative influence of referral bias. However, in the patient subset that will be sent to coronary angiography, the opposite results can be expected.

PMID: 19766453

Noninvasive Coronary Angiography by 320-Row Computed Tomography with Lower Radiation Exposure and Maintained Diagnostic Accuracy: Comparison of Results with Cardiac Catheterization in a Head-to-Head Pilot Investigation

OBJECTIVE: Noninvasive coronary angiography with the use of multislice computed tomography (CT) scanners is feasible with high sensitivity and negative predictive value; however, the radiation exposure associated with this technique is rather high. We evaluated coronary angiography using whole-heart 320-row CT, which avoids exposure-intensive overscanning and overranging.

METHODS: A total of 30 consecutive patients with suspected coronary artery disease referred for clinically indicated conventional coronary angiography (CCA) were included in this prospective intention-to-diagnose study. CT was performed with the use of up to 320 simultaneous detector rows before same-day CCA, which, together with quantitative analysis, served as the reference standard.

RESULTS: The per-patient sensitivity and specificity for CT compared with CCA were 100% (95% confidence interval [CI], 72 to 100) and 94% (95% CI, 73 to 100), respectively. Per-vessel versus per-segment sensitivity and specificity were 89% (95% CI, 62 to 98) and 96% (95% CI, 90 to 99) versus 78% (95% CI, 56 to 91) and 98% (95% CI, 96 to 99), respectively. Interobserver agreement between the 2 readers was significantly better for CCA (97% of 121 coronary arteries) than for CT (90%; P=0.04). Percent diameter stenosis determined with the use of CT showed good correlation with CCA (P<0.001, R=0.81) without significant underestimation or overestimation (-3.1+/-24.4%; P=0.08). Intraindividual comparison of CT with CCA revealed a significantly smaller effective radiation dose (median, 4.2 versus 8.5 mSv; P<0.05) and amount of contrast agent required (median, 80 versus 111 mL; P<0.001) for 320-row CT. The majority of patients (87%) indicated that they would prefer CT over CCA for future diagnostic imaging (P<0.001).

CONCLUSIONS: CT with the use of emerging technology has the potential to significantly reduce the radiation dose and amount of contrast agent required compared with CCA while maintaining high diagnostic accuracy.

PMID: 19704093

Imaging of the Unstable Plaque: How Far Have We Got?

Rupture of unstable plaques may lead to myocardial infarction or stroke and is the leading cause of morbidity and mortality in western countries. Thus, there is a clear need for identifying these vulnerable plaques before the rupture occurs. Atherosclerotic plaques are a challenging imaging target as they are small and move rapidly, especially in the coronary tree. Many of the currently available imaging tools for clinical use still provide minimal information about the biological characteristics of plaques, because they are limited with respect to spatial and temporal resolution. Moreover, many of these imaging tools are invasive. The new generation of imaging modalities such as magnetic resonance imaging, nuclear imaging such as positron emission tomographyand single photon emission computed tomography, computed tomography, fluorescence imaging, intravascular ultrasound, and optical coherence tomography offer opportunities to overcome some of these limitations.

This review discusses the potential of these techniques for imaging the unstable plaque.

PMID: 19833636