Bicuspid Aortic Valve: Four-Dimensional MR Evaluation of Ascending Aortic Systolic Flow Patterns

OBJECTIVES: To use time-resolved three-dimensional phase-contrast magnetic resonance (MR) imaging, also called four-dimensional flow MR imaging, to evaluate systolic blood flow patterns in the ascending aorta that may predispose patients with a bicuspid aortic valve (BAV) to aneurysm.

METHODS: The HIPAA-compliant protocol received institutional review board approval, and informed consent was obtained. Four-dimensional flow MR imaging was used to assess blood flow in the thoracic aorta of 53 individuals: 20 patients with a BAV, 25 patient with a tricuspid aortic valve (TAV), and eight healthy volunteers. The Fisher exact test was used to evaluate the significance of flow patterns differences.

RESULTS: Nested helical flow was seen at peak systole in the ascending aorta of 15 of 20 patients with a BAV but in none of the healthy volunteers or patients with a TAV. This flow pattern was seen both in patients with a BAV with a dilated ascending aorta (n=6) and in those with a normal ascending aorta (n=9), was seen in the absence of aortic stenosis (n=5), and was associated with eccentric systolic flow jets in all cases. Fusion of right and left leaflets gave rise to right-handed helical flow and right-anterior flow jets (n=11), whereas right and noncoronary fusion gave rise to left-handed helical flow with left –posterior flow jets (n=4).

CONCLUSIONS: Four-dimensional flow MR imaging showed abnormal helical systolic flow in the ascending aorta of patients with a BAV, including those without aneurysm or aortic stenosis. Identification and characterization of eccentric flow jets in these patients may help identify those at risk for development of ascending aortic aneurysm.

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Review of Journal of Cardiovascular Magnetic Resonance 2009

There were 56 articles published in the Journal of Cardiovascular Magnetic Resonance in 2009. The editors were impressed with the high quality of the submissions, of which our acceptance rate was about 40%. In accordance with open-access publishing, the articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. We have therefore chosen to briefly summarise the papers in this article for quick reference for our readers in broad areas of interest, which we feel will be useful to practitioners of cardiovascular magnetic resonance (CMR). In some cases where it is considered useful, the articles are also put into the wider context with a short narrative and recent CMR references. It has been a privilege to serve as the Editor of the JCMR this past year. I hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication.

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Image Fusion of Coronary CT Angiography and Cardiac Perfusion MRI: A Pilot Study

OBJECTIVES: To develop a tool for the image fusion of computed tomography coronary angiography (CTCA) and cardiac magnetic resonance imaging (CMR).

METHODS: Surface representations and volume-rendered images from fused CTCA/CMR data of five patients with significant coronary artery disease (CAD) on CTCA and perfusion deficits on CMR were generated using a newly developed software prototype. The spatial relationship of significant coronary artery stenosis at CTCA and myocardial defects at CMR was evaluated.

RESULTS: Registration of CTCA and CMR images was possible in all patients. The comprehensive three-dimensional visualisation of fused CTCA and CMR data accurately demonstrated the relationship between coronary artery stenoses and myocardial defects in all patients.

CONCLUSIONS: The introduced tool enables image fusion of CTCA and CMR data sets and allows for correct superposition of the coronary arteries derived from CTCA onto the corresponding myocardial segments derived from CMR. The method facilitates the comprehensive assessment of the functionally relevant CAD by the exact allocation of culprit coronary stenoses to corresponding myocardial defects at a low radiation dose.

PMID: 20204639

Mitral Cerclage Annuloplasty, A Novel Transcatheter Treatment for Secondary Mitral Valve Regurgitation: Initial Results in Swine

OBJECTIVES: We developed and tested a novel transcatheter circumferential annuloplasty technique to reduce mitral regurgitation in porcine ischemic cardiomyopathy. Catheter-based annuloplasty for secondary mitral regurgitation exploits the proximity of the coronary sinus to the mitral annulus, but is limited by anatomic variants and coronary artery entrapment.

METHODS: The procedure, “cerclage annuloplasty,” is guided by magnetic resonance imaging (MRI) roadmaps fused with live X-ray. A coronary sinus guidewire traverses a short segment of the basal septal myocardium to re-enter the right heart where it is exchanged for a suture. Tension is applied interactively during imaging and secured with a locking device.

RESULTS: We found 2 feasible suture pathways from the great cardiac vein across the interventricular septum to create cerclage. Right ventricular septal re-entry required shorter fluoroscopy times than right atrial re-entry, which entailed a longer intramyocardial traversal but did not cross the tricuspid valve. Graded tension progressively reduced septal-lateral annular diameter, but not end-systolic elastance or regional myocardial function. A simple arch-like device protected entrapped coronary arteries from compression even during supratherapeutic tension. Cerclage reduced mitral regurgitation fraction (from 22.8 +/- 12.7% to 7.2 +/- 4.4%, p = 0.04) by slice tracking velocity-encoded MRI. Flexible cerclage reduced annular size but preserved annular motion. Cerclage also displaced the posterior annulus toward the papillary muscles. Cerclage introduced reciprocal constraint to the left ventricular outflow tract and mitral annulus that enhanced leaflet coaptation. A sample of human coronary venograms and computed tomography angiograms suggested that most have suitable venous anatomy for cerclage.

CONCLUSIONS: Transcatheter mitral cerclage annuloplasty acutely reduces mitral regurgitation in porcine ischemic cardiomyopathy. Entrapped coronary arteries can be protected. MRI provided insight into the mechanism of cerclage action.

PMID: 19660696

Combined Dyssynchrony and Scar Imaging With Cardiac Magnetic Resonance Imaging Predicts Clinical Response and Long-Term Prognosis Following Cardiac Resynchronization Therapy

OBJECTIVES: Cardiac resynchronization therapy (CRT) is advocated in advanced heart failure; however, patient selection remains challenging. We examined the utility of multi-sequential cardiac magnetic resonance imaging (CMR) in predicting outcome after CRT.

METHODS: We performed multi-sequential CMR on 40 subjects with cardiomyopathy and advanced heart failure, despite optimized medical therapy. All patients had been recommended for CRT according to accepted clinical guidelines. Patients were defined by CMR as likely responders if they had significant mechanical dyssynchrony (≥65 ms delay between septal and posterolateral wall contraction on cine imaging), and no transmural scarring of the anteroseptal or posterolateral wall on delayed contrast-enhanced imaging. Clinical composite score was recorded at baseline and 6 months post-CRT.

RESULTS: Long-term follow-up (transplant-free survival) was 497 ± 55 days post-CRT. A clinical response was achieved in 19/26 (73%) of the CMR-predicted responders and 2/12 (17%) of the CMR-predicted non-responders (P < 0.01, χ²). The sensitivity of CMR for prediction of clinical response to CRT was 90%, with a specificity of 59%. Transplant-free survival post-CRT was achieved in 88% of the CMR-predicted responders and 58% of the CMR-predicted non-responders (P < 0.05, Kaplan–Meier survival analysis).

CONCLUSIONS: Multi-sequential CMR identifies patients with severe cardiomyopathy who will respond to CRT with a favourable long-term prognosis.

PMID: 20190262

Right Ventricular Involvement in Acute Left Ventricular Myocardial Infarction: Prognostic Implications of MRI Findings

OBJECTIVE. The purpose of this study was to investigate the prevalence and prognostic importance of the cardiac MRI finding of right ventricular involvement in patients with acute ST-segment elevation myocardial infarction (MI).

METHODS. Fifty patients (41 men, nine women; mean age, 58 ± 11 years) with first-ST-segment elevation MI underwent 1.5-T cardiac MRI immediately after successful percutaneous coronary intervention. The cardiac MRI protocol included steady-state free precession cine sequences for functional assessment of the left, right, and both ventricles and inversion recovery FLASH delayed enhancement sequences after contrast administration for the quantification of myocardial damage. The prevalence of right ventricular involvement detected with ECG and echocardiography was compared with the prevalence detected with cardiac MRI, which was the reference standard. Patients underwent follow-up for 32 ± 8 months.

RESULTS. Right ventricular involvement was diagnosed with cardiac MRI in 27 patients (54%): 14 of 30 patients (47%) with inferior ST-segment elevation MI and 13 of 20 patients (65%) with anterior ST-segment elevation MI. ECG and echocardiographic findings showed only moderate agreement with cardiac MRI findings in the detection of right ventricular involvement in inferior acute MI (kappa = 0.38). Patients with right ventricular involvement in anterior ST-segment elevation MI had larger infarcts (delayed enhancement, 25.9% ± 14.5% vs 11.4% ± 10.1%; p = 0.030), lower left ventricular ejection fraction (34.3% ± 8.2% vs 45.2% ± 9.5%; p < 0.015), and lower right ventricular ejection fraction (39.8% ± 6.6% vs 54.9% ± 8.8%; p < 0.001) than those without right ventricular involvement. In a multivariate logistic regression model, right ventricular involvement was a strong independent predictor (odds ratio, 15.8; 95% CI, 4–63%) of major cardiac adverse events.

CONCLUSION. Right ventricular involvement in ST-segment elevation MI is detected more frequently with cardiac MRI than with ECG and echocardiography and is an independent prognostic indicator.

PMID: 20173133

High Resolution Myocardial Magnetic Resonance Stress Perfusion Imaging at 3T Using a 1M Contrast Agent

PMID: 19760241

Characteristics and Clinical Significance of Late Gadolinium Enhancement by Contrast-Enhanced Magnetic Resonance Imaging in Patients With Hypertrophic Cardiomyopathy

BACKGROUND: Myocardial late gadolinium enhancement (LGE) on contrast-enhanced magnetic resonance imaging (CE-MRI) of patients with hypertrophic cardiomyopathy (HCM) has been suggested to represent intramyocardial fibrosis and, as such, an adverse prognostic risk factor. We evaluated the characteristics of LGE on CE-MRI and explored whether LGE among patients with HCM was associated with genetic testing, severe symptoms, ventricular arrhythmias, or sudden cardiac death (SCD).

METHODS: Four hundred twenty-four patients with HCM (age 55+/-16 years [range 2 to 90], 41% females), without a history of septal ablation/myectomy, underwent CE-MRI (GE 1.5 Tesla). We evaluated the relation between LGE and HCM genes status, severity of symptoms, and the degree of ventricular ectopy on Holter ECG. Subsequent SCD and appropriate implanted cardioverter defibrillator (ICD) therapies were recorded during a mean follow-up of 43+/-14 months (range 16 to 94).

RESULTS: Two hundred thirty-nine patients (56%) had LGE on CE-MRI, ranging from 0.4% to 65% of the left ventricle. Gene-positive patients were more likely to have LGE (P<0.001). The frequencies of New York Heart Association class >3 dyspnea and angina class >or=3 were similar in patients with and without LGE (125 of 239 [52%] versus 94 of 185 [51%] and 24 of 239 [10%] versus 18 of 185 [10%], respectively, P=NS). LGE-positive patients were more likely to have episodes of nonsustained ventricular tachycardia (34 of 126 [27%] versus 8 of 94 [8.5%], P<0.001), had more episodes of nonsustained ventricular tachycardia per patient (4.5+/-12 versus 1.1+/-0.3, P=0.04), and had higher frequency of ventricular extrasystoles/24 hours (700+/-2080 versus 103+/-460, P=0.003). During follow-up, SCD occurred in 4 patients, and additional 4 patients received appropriate ICD discharges. All 8 patients were LGE positive (event rate of 0.94%/y, P=0.01 versus LGE negative). Two additional heart failure-related deaths were recorded among LGE-positive patients. Univariate associates of SCD or appropriate ICD discharge were positive LGE (P=0.002) and presence of nonsustained ventricular tachycardia (P=0.04). The association of LGE with events remained significant after controlling for other risk factors.

CONCLUSIONS: In patients with HCM, presence of LGE on CE-MRI was common and more prevalent among gene-positive patients. LGE was not associated with severe symptoms. However, LGE was strongly associated with surrogates of arrhythmia and remained a significant associate of subsequent SCD and/or ICD discharge after controlling for other variables. If replicated, LGE may be considered an important risk factor for sudden death in patients with HCM.

PMID: 19850699

Meta-analysis: Noninvasive Coronary Angiography Using Computed Tomography Versus Magnetic Resonance Imaging

OBJECTIVES: Two imaging techniques, multislice computed tomography (CT) and magnetic resonance imaging (MRI), have evolved for noninvasive coronary angiography. To compare CT and MRI for ruling out clinically significant coronary artery disease (CAD) in adults with suspected or known CAD.

METHODS: MEDLINE, EMBASE, and ISI Web of Science searches from inception through 2 June 2009 and bibliographies of reviews. Prospective English- or German-language studies that compared CT or MRI with conventional coronary angiography in all patients and included sufficient data for compilation of 2 × 2 tables. 2 investigators independently extracted patient and study characteristics; differences were resolved by consensus.

RESULTS: 89 and 20 studies (comprising 7516 and 989 patients) assessed CT and MRI, respectively. Bivariate analysis of data yielded a mean sensitivity and specificity of 97.2% (95% CI, 96.2% to 98.0%) and 87.4% (CI, 84.5% to 89.8%) for CT and 87.1% (CI, 83.0% to 90.3%) and 70.3% (CI, 58.8% to 79.7%) for MRI. In studies that included only patients with suspected CAD, sensitivity and specificity of CT were 97.6% (CI, 96.1% to 98.5%) and 89.2% (CI, 86.0% to 91.8%). Covariate analysis yielded a significantly higher sensitivity for CT scanners with more than 16 rows (98.1% [CI, 97.0% to 99.0%]; P < 0.050) than for older-generation scanners (95.6% [CI, 94.0% to 97.0%]). Heart rates less than 60 beats/min during CT yielded significantly better values for sensitivity than did higher heart rates (P < 0.001). Few studies investigated coronary angiography with MRI. Only 5 studies were direct head-to-head comparisons of CT and MRI. Covariate analyses explained only part of the observed heterogeneity.

CONCLUSIONS: For ruling out CAD, CT is more accurate than MRI. Scanners with more than 16 rows improve sensitivity, as do slowed heart rates.

PMID: 16442907

The Year in Cardiac Imaging

No Abstract Available. See Link Below.

The Year in Cardiac Imaging 2009

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Natural History and Expansive Clinical Profile of Stress (Tako-Tsubo) Cardiomyopathy

OBJECTIVES: This study was designed to define more completely the clinical spectrum and consequences of stress cardiomyopathy (SC) beyond the acute event. Stress cardiomyopathy is a recently recognized condition characterized by transient cardiac dysfunction with ventricular ballooning.

METHODS: Clinical profile and outcome were prospectively assessed in 136 consecutive SC patients.

RESULTS: Patients were predominantly women (n = 130; 96%), but 6 were men (4%). Ages were 32 to 94 years (mean age 68 ± 13 years); 13 (10%) were 50 years of age. In 121 patients (89%), SC was precipitated by intensely stressful emotional (n = 64) or physical (n = 57) events, including 22 associated with sympathomimetic drugs or medical/surgical procedures; 15 other patients (11%) had no evident stress trigger. Twenty-five patients (18%) were taking beta-blockers at the time of SC events. Three diverse ventricular contraction patterns were defined by cardiovascular magnetic resonance (CMR) imaging, usually with rapid return to normal systolic function, although delayed >2 months in 5%. Right and/or left ventricular thrombi were identified in 5 patients (predominantly by CMR imaging), including 2 with embolic events. Three patients (2%) died in-hospital and 116 (85%) have survived, including 5% with nonfatal recurrent SC events. All-cause mortality during follow-up exceeded a matched general population (p = 0.016) with most deaths occurring in the first year.

CONCLUSIONS: In this large SC cohort, the clinical spectrum was heterogeneous with about one-third either male, 50 years of age, without a stress trigger, or with in-hospital death, nonfatal recurrence, embolic stroke, or delayed normalization of ejection fraction. Beta-blocking drugs were not absolutely protective and SC was a marker for increased noncardiac mortality. These data support expanded management and surveillance strategies including CMR imaging and consideration for anticoagulation.

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Multimodality Comparison of Quantitative Volumetric Analysis of the Right Ventricle

OBJECTIVES: We undertook volumetric analysis of the right ventricle (RV) by real-time 3-dimensional echocardiography (RT3DE), cardiac magnetic resonance (CMR), and cardiac computed tomography (CCT) on images obtained in RV-shaped phantoms and in patients with a wide range of RV geometry. Assessment of the RV by 2-dimensional (2D) echocardiography remains challenging due to its unique geometry and limitations of the current analysis techniques. RT3DE, CMR, and CCT, which can quantify RV volumes, promise to overcome the limitations of 2D echocardiography.

METHODS: Images were analyzed using RV Analysis software. Volumes measured in vitro were compared with the true volumes. The human protocol included 28 patients who underwent RT3DE, CMR, and CT on the same day. Volumetric analysis of CMR images was used as a reference, against which RT3DE and CCT measurements were compared using linear regression and Bland-Altman analyses. To determine the reproducibility of the volumetric analysis, repeated measurements were performed for all 3 imaging modalities in 11 patients.

RESULTS: The in vitro measurements showed that: 1) volumetric analysis of CMR images yielded the most accurate measurements; 2) CCT measurements showed slight (4%) but consistent overestimation; and 3) RT3DE measurements showed small underestimation, but considerably wider margins of error. In humans, both RT3DE and CCT measurements correlated highly with the CMR reference (r = 0.79 to 0.89) and showed the same trends of underestimation and overestimation noted in vitro. All interobserver and intraobserver variability values were <14%, with those of CMR being the highest.

CONCLUSIONS: Volumetric quantification of RV volume was performed on CMR, CCT, and RT3DE images. Eliminating analysis-related intermodality differences allowed fair comparisons and highlighted the unique limitations of each modality. Understanding these differences promises to aid in the functional assessment of the RV.

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Primary Percutaneous coronary Intervention by Magnetic Navigation Compared with Conventional Wire Technique

OBJECTIVES: Comparison of magnetic guidewire navigation in percutaneous coronary intervention (MPCI) vs. conventional percutaneous coronary intervention (CPCI) for the treatment of acute myocardial infarction.

METHODS: We compared 65 sequential patients (mean age 61 ± 15 years) undergoing primary MPCI with those of 405 patients undergoing CPCI (mean age 61 ± 13 years). The major endpoint was contrast media use. Technical success and procedural outcomes were evaluated. Clinical demographics and angiographic characteristics of the two groups were similar, except for fewer patients with previous coronary artery bypass grafting (CABG) and hypertension in the CPCI group and fewer patients with diabetes in the MPCI group.

RESULTS: The technical success rate was high in both the MPCI and CPCI groups (95.4 vs. 98%). There was significantly less contrast media usage in the MPCI compared with the CPCI group, median reduction of contrast media of 30 mL with an OR = 0.41 (0.21–0.81). Fluoroscopy times were significantly reduced for MPCI compared with CPCI, median reduction of 7.2 min with an OR = 0.42 (0.20–0.79).

CONCLUSIONS: This comparison indicates the feasibility and non-inferiority of magnetic navigation in performing primary PCI and suggests the possibility of reductions in contrast media use and fluoroscopy time compared with CPCI.

PMID: 20051425

Assessment of Left Atrial Volumes and Function in Orthotopic Heart Transplant Recipients by Dual-Source CT: Comparison With MRI

OBJECTIVES: To compare left atrial performance with dual-source CT (DSCT) with respect to magnetic resonance imaging (MRI) in orthotopic heart transplant recipients.

METHODS: Twenty-nine consecutive heart transplant recipients (27 male; mean age 64.1 +/- 13 years; mean time from transplantation 122.8 +/- 69.7 months) referred for exclusion of cardiac allograft vasculopathy underwent cardiac DSCT and MRI. Standard biatrial technique was employed in 13 subjects whereas 16 were transplanted after the bicaval technique. Axial 5-mm slice-thickness DSCT datasets reconstructed in 5% steps of the cardiac cycle and axial 5-mm SSFP-MRI images were analyzed. Two blinded readers manually traced left atrial contours in random order to estimate end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF). Parameters were compared with a paired sample Student t-test. Concordance correlation coefficient (CCC) was calculated to determine measurement agreement between techniques and observers.

RESULTS: Left atrial volumes were significantly higher with cardiac DSCT (EDV: 170.9 +/- 78.1 mL; ESV: 139.5 +/- 76.6 mL) than with MRI (EDV: 158.2 +/- 72.5 mL; ESV: 124.2 +/- 68.2 mL), whereas left atrial EF was lower with DSCT (EF: 20.8% +/- 7.5% vs. 23.6% +/- 7.7%) (P < 0.05). Measurement agreement between DSCT and MRI was excellent for all parameters (CCC >0.82). Individuals operated with the biatrial anastomosis technique presented significantly higher left atrial volumes and lower EF compared with subjects with bicaval anastomosis. Interobserver agreement was excellent for all parameters (CCC >0.80).

CONCLUSION: Even if DSCT slightly overestimates left atrial volumes with respect to MRI, results remain clinically valid. Bicaval surgical technique offers improved left atrial performance compared with standard biatrial anastomosis. DSCT may be used as a reliable tool to estimate left atrial parameters in orthotopic heart transplant recipients.

PMID: 20027119

Non-Invasive Assessment and Clinical Strategy of Stable Coronary Artery Disease by Magnetic Resonance Imaging, Multislice Computed Tomography and Myocardial Perfusion SPECT

Coronary multislice computed tomography (MSCT) angiography and magnetic resonance angiography (MRA) have emerged as new diagnostic techniques that allow direct visualization of the coronary artery. These new modalities have both advantages and disadvantages concerning radiation exposure, the use of contrast medium, ability of visualizing heavily calcified artery lumens, and spatial and temporal resolution. However, these modalities only provide anatomical information of the coronary artery. Functional assessment of the severity of coronary artery disease (CAD) is essential for the management of patients with known or suspected CAD in practical clinical settings. Myocardial perfusion single-photon emission computed tomography is thought to be the most suitable diagnostic procedure for the determination of therapeutic strategy when coronary MSCT and MRA show significant and also insignificant coronary artery lesions.

PMID: 19966503