Risk and Fate of Cerebral Embolism After Transfemoral Aortic Valve Implantation A Prospective Pilot Study With Diffusion-Weighted Magnetic Resonance Imaging

OBJECTIVES: The aim of this study was prospective investigation of silent and clinically apparent cerebral embolic events and neurological impairment after transfemoral aortic valve implantation (TAVI). Transfemoral aortic valve implantation is a novel therapeutic approach for multimorbid patients with severe aortic stenosis. We investigated peri-interventional cerebral embolism with diffusion-weighted magnetic resonance imaging (DW-MRI) and its relationship to clinical and serologic parameters of brain injury.

METHODS: Cerebral DW-MRI was performed before, directly and 3 months after TAVI with the current third-generation self-expanding Corevalve (Medtronic, Minneapolis, Minnesota) prosthesis. At the timepoints of the serial MRI studies, focal neurological impairment was assessed according to the National Institutes of Health Stroke Scale (NIHSS), and serum concentration of neuron-specific enolase (NSE), a marker of the volume of brain tissue involved in an ischemic event, were determined.

RESULTS: Thirty patients were enrolled; 22 completed the imaging protocol. Three patients (10%) had new neurological findings after TAVI, of whom only 1 (3.6%) had a permanent neurological impairment. Of the 22 TAVI patients with complete imaging data, 16 (72.7%) had 75 new cerebral lesions after TAVI presumed to be embolic. The NIHSS and NSE were not correlated with DW-MRI lesions.

CONCLUSIONS: The incidence of clinically silent peri-interventional cerebral embolic lesions after TAVI is high. However, in this cohort of 30 patients, the incidence of persistent neurological impairment was low. (Incidence and Severity of Silent and Apparent Cerebral Embolism After Conventional and Minimal-invasive Transfemoral Aortic Valve Replacement; NCT00883285).

PMID: 20188503

Shorter Difference Between Myocardium and Blood Optimal Inversion Time Suggests Diffuse Fibrosis in Dilated Cardiomyopathy

PURPOSE: To find evidence of diffuse fibrosis in dilated cardiomyopathy (DCM) patients by comparing measurements on clinical late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) studies between DCM and healthy subjects.

METHODS: LGE-CMR and the Look-Locker images from 20 DCM patients and 17 healthy controls were analyzed. Blood signal-to-noise ratio (SNR), myocardium SNR, and blood-to-myocardium contrast-to-noise ratio (CNR) were measured on the LGE-CMR images. The optimal inversion time (TI) to null blood and myocardium was determined on the Look-Locker images. The postcontrast T(1) was estimated using a phantom study that correlated optimal TI and heart rate to T(1).

RESULTS: The blood SNR was lower, myocardium SNR was higher, and the blood-to-myocardium CNR was lower (6.6 +/- 0.7 vs. 10.3 +/- 0.9, P = 0.004) on DCM LGE-CMR images as compared to controls. The blood-myocardium optimal TI difference (DeltaTI) was lower (38 +/- 2 msec vs. 55 +/- 3 msec, P < 0.001) in DCM, and the estimated blood-myocardium T(1) difference (DeltaT(1)) (116 +/- 6 msec vs. 152 +/- 8 msec, P = 0.001) was also lower.

CONCLUSIONS: DCM patients have reduced blood-myocardium DeltaTI and DeltaT(1), and lower CNR as compared to controls, suggesting the presence of diffuse fibrosis. This may impact the interpretation of LGE data.

PMID: 19856417

Effect of Padding Duration on Radiation Dose and Image Interpretation in Prospectively ECG-Triggered Coronary CT Angiography

OBJECTIVES: Prospectively ECG-triggered coronary CT angiography images are acquired during a window in middiastole. Additional surrounding x-ray beam on time, or padding, can be variably set, and the increased padding results in additional available phases for analysis. The purpose of this study was to assess the effect of padding duration on image interpretability and its incident effect on radiation dose.

METHODS: We prospectively evaluated imaging of 886 patients undergoing consecutive prospectively ECG-triggered coronary CT angiographic examinations at three centers and compared the findings in patients stratified by padding duration. We assessed the effect of padding duration on image interpretability and radiation dose.

RESULTS: The mean patient age was 56 +/- 12 years, and 58% of the patients were men. The median heart rate was 55 beats/min (interquartile range, 50-61 beats/min). Padding duration was 0, 1-99, and 100-150 milliseconds for 268, 482, and 136 patients, respectively, with no difference in image interpretability rate between groups (per patient, 98.8%, 97.3%, and 97.1%; per artery, 99.2%, 99.2%, and 99.1%). The groups differed in median radiation dose (2.3 mSv [interquartile range, 1.5-3.2 mSv]; 3.8 mSv [interquartile range, 2.3-4.7 mSv]; 5.5 mSv [interquartile range, 3.8-6.1 mSv]; p < 0.001). Independent of patient and scan parameters, increased padding was associated with greater radiation dose (45% increase per 100-millisecond increase in padding, p < 0.001).

CONCLUSIONS: In a large multicenter study of coronary CT angiography of patients with excellent heart rate control, the use of minimal padding was associated with a substantial reduction in radiation dose with preserved image interpretability. Use of no or reduced padding should be considered in dose-reduction strategies.

PMID: 20308494

Transapical Aortic Valve Implantation in 100 Consecutive Patients: Comparison to Propensity-Matched Conventional Aortic Valve Replacement

OBJECTIVES: To evaluate the outcome of transapical aortic valve implantation (TA-AVI) in comparison to conventional surgery.

METHODS: One hundred consecutive high-risk patients with symptomatic aortic valve stenosis received TA-AVI using the Edwards SAPIEN™ pericardial xenograft between February 2006 and January 2008. Patient age was 82.7 ± 5 years, 77 were females, logistic EuroSCORE predicted risk of mortality was 29.4 ± 13% and Society Thoracic Surgeons score risk for mortality was 15.2 ± 8.3%. Propensity score analysis was used to identify a control group of patients that underwent conventional aortic valve replacement (C-AVR).

RESULTS: Transapical aortic valve implantation was performed successfully in 97 patients, whereas three patients required early conversion. There were no new onset neurological events in the TA-AVI group and early extubation was performed in 82 patients. Echocardiography revealed good valve function with low transvalvular gradients in all patients. Thirty-day survival was 90 ± 3 vs. 85 ± 4% for TA-AVI vs. C-AVR, and 1-year survival was 73 ± 4 vs. 69 ± 5% (P = 0.55).

CONCLUSIONS: Transapical aortic valve implantation is a safe, minimally invasive, and off-pump technique to treat high-risk patients with aortic stenosis. Results of the initial 100 patients are good and compare favourably to conventional surgery.

PMID: 20233788

Microvascular Obstruction Remains a Portent of Adverse Remodeling in Optimally-Treated Patients with Left Ventricular Systolic Dysfunction After Acute Myocardial Infarction

OBJECTIVES: Microvascular obstruction (MO) is associated with large acute myocardial infarction (AMI) and lower left ventricular (LV) ejection fraction, and predicts greater remodeling, but whether this effect is abolished by contemporary anti-remodeling therapies is subject to debate. We examined the influence of several infarct characteristics, including MO, on LV remodeling in an optimally-treated post-AMI cohort, using contrast-enhanced cardiac magnetic resonance (ceCMR).

METHODS: 100 patients (mean age 58.9±12 years, 77% male) underwent ceCMR at baseline (~4 days), 12 and 24 weeks. The effects on LV remodeling (i.e. change in LV end-systolic volume index [LVESVi]) of infarct site, transmurality, endocardial extent, and the presence of early and late MO were analyzed.

RESULTS: Mean baseline infarct volume index decreased from 34.0 (21.2) mL/m2 to 20.9 (12.9) mL/m2 at 24 weeks (p<0.001). Infarct site had no influence on remodeling, but greater baseline infarct transmurality (r=0.47, p<0.001) and endocardial extent (r=0.26, p<0.01) were associated with higher LVESVi. Early MO was seen in 69 (69%) of patients and persisted, as late MO, in 56 (56%). Patients with late MO underwent significantly greater remodeling than those without MO (LVESVi +4.1 [13.4] vs. -7.0 [12.7] mL/m2 respectively, p=0.001); those with early MO only displayed an intermediate LVESVi (-4.9 [13.0] mL/m2). Importantly, late MO was seen frequently despite optimal coronary blood flow having been restored at angiography.

CONCLUSIONS: Late MO on pre-discharge ceCMR remains an ominous predictor of adverse LV remodeling despite powerful anti-remodeling therapy, and may be useful in the risk-stratification of survivors of AMI.

PMID: 20348438

Coronary Plaque Imaging With 256-Slice Multidetector Computed Tomography: Interobserver Variability of Volumetric Lesion Parameters with Semiautomatic Plaque Analysis Software

OBJECTIVES: The purpose of this study was to evaluate the potential clinical value of coronary plaque imaging with a new generation CT scanner and the interobserver variability of coronary plaque assessment with a new semiautomatic plaque analysis application.

METHODS: Thirty-five isolated plaques of the left anterior descending coronary artery from 35 patients were evaluated with a new semiautomatic plaque analysis application. All patients were scanned with a 256-slice MDCT scanner (Brilliance iCT, Philips Healthcare, Cleveland OH, USA). Two independent observers evaluated lesion volume, maximum plaque burden, lesion CT number mean and standard deviation, and relative lesion composition.

RESULTS: We found 10 noncalcified, 16 mixed, and 9 calcified lesions in our study cohort. Relative interobserver bias and variability for lesion volume were -37%, -13%, -49%, -44% and 28%, 16%, 37%, and 90% for all, noncalcified, mixed, and calcified lesions, respectively. Absolute interobserver bias and variability for relative lesion composition were 1.2%, 0.5%, 1.5%, 1.3% and 3.3%, 4.5%, 7.0%, and 4.4% for all, noncalcified, mixed, and calcified lesions, respectively.

CONCLUSIONS: While mixed and calcified lesions demonstrated a high degree of lesion volume interobserver variability, noncalcified lesions had a lower degree of lesion volume interobserver variability. In addition, relative noncalcified lesion composition had a very low interobserver variability. Therefore, there may a role for MDCT in serial noncalcified plaque assessment with semiautomatic analysis software.

PMID: 20339922

Defining Left Ventricular Apex-to-Base Twist Mechanics Computed From High-Resolution 3D Echocardiography

OBJECTIVES: To compute left ventricular (LV) twist from 3-dimensional (3D) echocardiography. LV twist is a sensitive index of cardiac performance. Conventional 2-dimensional based methods of computing LV twist are cumbersome and subject to errors.

METHODS: We studied 10 adult open-chest pigs. The pre-load to the heart was altered by temporary controlled occlusion of the inferior vena cava, and myocardial ischemia was produced by ligating the left anterior descending coronary artery. Full-volume 3D loops were reconstructed by stitching of pyramidal volumes acquired from 7 consecutive heart beats with electrocardiography gating on a Philips IE33 system (Philips Medical Systems, Andover, Massachusetts) at baseline and other steady states. Polar coordinate data of the 3D images were entered into an envelope detection program implemented in MatLab (The MathWorks, Inc., Natick, Massachusetts), and speckle motion was tracked using nonrigid image registration with spline-based transformation parameterization. The 3D displacement field was obtained, and rotation at apical and basal planes was computed. LV twist was derived as the net difference of apical and basal rotation. Sonomicrometry data of cardiac motion were also acquired from crystals anchored to epicardium in apical and basal planes at all states.

RESULTS: The 3D dense tracking slightly overestimated the LV twist, but detected changes in LV twist at different states and showed good correlation (r = 0.89) when compared with sonomicrometry-derived twist at all steady states. In open chest pigs, peak cardiac twist was increased with reduction of pre-load from inferior vena cava occlusion from 6.25° ± 1.65° to 9.45° ± 1.95°. With myocardial ischemia from left anterior descending coronary artery ligation, twist was decreased to 4.90° ± 0.85° (r = 0.8759).

CONCLUSIONS: Despite lower spatiotemporal resolution of 3D echocardiography, LV twist and torsion can be computed accurately.

PMID: 20223418

Reproducibility of Proximal Isovelocity Surface Area, Vena Contracta, and Regurgitant Jet Area for Assessment of Mitral Regurgitation Severity

OBJECTIVES: The aim of this study was to evaluate the interobserver agreement of proximal isovelocity surface area (PISA) and vena contracta (VC) for differentiating severe from nonsevere mitral regurgitation (MR). Recommendation for MR evaluation stresses the importance of VC width and effective regurgitant orifice area by PISA measurements. Reliable and accurate assessment of MR is important for clinical decision making regarding corrective surgery. We hypothesize that color Doppler-based quantitative measurements for classifying MR as severe versus nonsevere may be particularly susceptible to interobserver agreement.

METHODS: The PISA and VC measurements of 16 patients with MR were interpreted by 18 echocardiologists from 11 academic institutions. In addition, we obtained quantitative assessment of MR based on color flow Doppler jet area.

RESULTS: The overall interobserver agreement for grading MR as severe or nonsevere using qualitative and quantitative parameters was similar and suboptimal: 0.32 (95% confidence interval [CI]: 0.1 to 0.52) for jet area–based MR grade, 0.28 (95% CI: 0.11 to 0.45) for VC measurements, and 0.37 (95% CI: 0.16 to 0.58) for PISA measurements. Significant univariate predictors of substantial interobserver agreement for: 1) jet area–based MR grade was functional etiology (p = 0.039); 2) VC was central MR (p = 0.013) and identifiable effective regurgitant orifice (p = 0.049); and 3) PISA was presence of a central MR jet (p = 0.003), fixed proximal flow convergence (p = 0.025), and functional etiology (p = 0.049). Significant multivariate predictors of raw interobserver agreement 80% included: 1) for VC, identifiable effective regurgitant orifice (p = 0.035); and 2) for PISA, central regurgitant jet (p = 0.02).

CONCLUSIONS: The VC and PISA measurements for distinction of severe versus nonsevere MR are only modestly reliable and associated with suboptimal interobserver agreement. The presence of an identifiable effective regurgitant orifice improves reproducibility of VC and a central regurgitant jet predicts substantial agreement among multiple observers of PISA assessment.

PMID: 20223419

The Diagnostic Accuracy of 256-Row Computed Tomographic Angiography Compared With Invasive Coronary Angiography in Patients With Suspected Coronary Artery Disease

OBJECTIVES: To assess the diagnostic accuracy of 256-row computed tomographic angiography (CTA) in patients with suspected coronary artery disease (CAD). Non-invasive imaging of the coronary artery by CTA has increasingly been used in recent years. The accuracy of 256-row CTA has not yet been studied. We sought to assess the accuracy of 256-row CTA compared with invasive coronary angiography (ICA) in the diagnosis and assessment of CAD.

METHODS: We prospectively evaluated 104 consecutive individuals who accepted CTA and then underwent ICA. The presence of stenosis ≥50% was considered obstructive. The diagnostic accuracy of CTA for detecting obstructive stenosis was compared with that of ICA. The area under the receiver-operating-characteristic curve (AUC) was used to evaluate the diagnostic accuracy of CTA relative to ICA.

RESULTS: A total of 86 patients had obstructive CAD. The patient-based analysis of CTA for detecting stenosis ≥50% according to ICA revealed an AUC of 0.744 [95% confidence interval (CI), 0.572–0.916], with a sensitivity of 98.8%, a specificity of 50%, a positive predictive value (PPV) of 92.4%, and a negative predictive value (NPV) of 87.5%. The segment-based analysis revealed an AUC of 0.915 (95% CI, 0.847–0.982), with a sensitivity of 93.5%, a specificity of 95%, a PPV of 77.6%, and an NPV of 98.7%. The vessel-based analysis revealed an AUC of 0.887 (95% CI, 0.808–0.966), with a sensitivity of 94.3%, a specificity of 87.3%, a PPV of 82.7%, and an NPV of 95.9%.

CONCLUSIONS: 256-Row CTA is a highly sensitive test of CAD and has a high predictive value. 256-Row CTA may be a potential alternative

PMID: 20233790

Prognostic Implications of Left Ventricular Filling Pressure With Exercise

OBJECTIVES:  The estimation of left ventricular (LV) filling pressure from the ratio of transmitral and annular velocities (E/e’) after exercise echocardiography may identify diastolic dysfunction in patients who complain of exertional dyspnea. This study sought to determine the relative contributions of exercise E/e’ and ischemia to outcomes in patients referred for exercise echocardiography.

METHODS:  Rest and exercise E/e’ were obtained in 522 patients referred for exercise echocardiography, who were followed for cardiovascular death and hospitalization over a median of 13.2 months. Exercise E/e’ >2 SD from normal was used to denote raised LV filling pressure with stress (n=75), and ischemia (n=250) was identified by inducible wall motion abnormalities.

RESULTS: There were 65 cardiovascular hospitalizations during the follow-up period. Survival analysis showed patients without ischemia and with normal exercise E/e’ to have a better prognosis than those with ischemia, with or without raised exercise E/e’ (P=0.003) and the outcomes of patients with isolated raised exercise E/e’ and isolated ischemia to be similar. Exercise E/e’ was most valuable in patients with normal resting E/e’; those with elevation with exercise had a worse outcome than those with normal exercise E/e’ (P=0.014). Exercise capacity (hazard ratio, 0.893; P=0.008), exercise wall motion score index (hazard ratio, 1.507; P<0.001), and exercise E/e’ >14.5 (hazard ratio, 2.988; P=0.002) were independent predictors of outcome. The addition of exercise E/e’ to exercise capacity and wall motion score index resulted in an increment in model power to predict adverse outcome (P=0.006).

CONCLUSIONS:  Exercise E/e’ is associated with cardiovascular hospitalization, independent of and incremental to inducible ischemia.

PMID: 20233862

Low-Density Lipoprotein and Noncalcified Coronary Plaque Composition in Patients With Newly Diagnosed Coronary Artery Disease on Computed Tomographic Angiography

OBJECTIVES: We sought to determine significant relations between atherogenic lipoproteins and the contribution of calcified plaque (CP), mixed plaque (MP), and noncalcified plaque (NCP) to the total plaque (TP) burden in patients without previous coronary artery disease.

METHODS: From 823 adult patients without previously established coronary artery disease (52% receiving statin therapy, 34% asymptomatic) but with visible coronary plaque on coronary computed tomographic angiography, we obtained segmental CP, MP, NCP, and TP counts from contrast-enhanced, electrocardiographic-gated computed tomography. Multivariate linear regression analysis was used to determine the associations of clinical factors and lipoprotein levels to CP, MP, and NCP counts and CP/TP, MP/TP, and NCP/TP count ratios.

RESULTS: Age, male gender, diabetes, smoking, and statin therapy were significantly associated with the CP count (p <0.001, p <0.001, p = 0.049, p = 0.016, and p = 0.003, respectively). Low-density lipoprotein (LDL) cholesterol was significantly associated with MP and NCP counts (all p values <0.002). LDL cholesterol was also the only variable to demonstrate significant concurrent relations with CP/TP, MP/TP, and NCP/TP ratios, including an inverse association with CP/TP (p = 0.008) and a positive association with MP/TP (p = 0.032). Analyses using non-high-density lipoprotein cholesterol in place of LDL cholesterol yielded similar results.

CONCLUSIONS: In conclusion, among the traditional clinical factors used to estimate cardiovascular event risk, LDL cholesterol is associated with an increased MP and NCP burden and is the sole variable that independently predicted relative predominance of CP, MP, and NCP, suggesting a potentially important role for lipoprotein levels in modulating the type of detectable coronary arterial plaque.

PMID: 20211316

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.

PMID:

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.

PMID:

CT of Left Ventricular Assist Devices

Left ventricular assist devices (LVADs) have become an increasingly beneficial option for patients with heart failure, especially in light of the insufficient availability of donor hearts. LVADs have been used effectively in end-stage heart failure as a bridge to heart transplantation, as destination therapy for those ineligible for transplantation, or as a bridge to myocardial recovery. Presently, a wide variety of LVADs are being used therapeutically. Four different LVADs have been used at the authors’ institution. The records of 42 patients who underwent implantation of 46 total LVADs during a 17-month period were reviewed; in 23 of these patients, computed tomography of the device was performed. Increased use of LVADs necessitates understanding of the normal positioning of a variety of these devices and recognition of potential complications, which include inflow and outflow cannula complications, postoperative hemorrhage, pericardial tamponade, thrombus formation, aortic valve stenosis, aortic valve insufficiency, right-sided heart failure, and infection.

PMID: 20228327

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