Fast 3D isotropic imaging of the aortic vessel wall by application of 2D spatially selective excitation and a new way of inversion recovery for black blood imaging.

PURPOSE: Aortic vessel wall imaging requires large coverage and a high spatial resolution, which makes it prohibitively time-consuming for clinical use. This work explores the feasibility of imaging the descending aorta in acceptable scan time, using two-dimensional (2D) spatially selective excitation and a new way of inversion recovery for black blood imaging. METHODS: The excitation pattern and field of view in a 3D gradient echo sequence are reduced in two dimensions, following the aorta's anisotropic geometry. Black blood contrast is obtained by partially inverting the blood's magnetization in the heart at the start of the cardiac cycle. Imaging is delayed until the inverted blood has filled the desired part of the aorta. The flip angle and delay are determined such that the blood signal is nulled upon arrival in the aorta. RESULTS: Experiments on eight volunteers showed that the descending aortic vessel wall could be imaged over more than 15 cm at a maximal resolution of 1.5 × 1.5 × 1.5 mm(3) in less than 5 min minimal scan time. CONCLUSION: This feasibility study demonstrates that time-efficient isotropic imaging of the descending aorta is possible by using 2D spatially selective excitation for motion artifact reduction and a new way of inversion recovery for black blood imaging.

Diagnostic accuracy of stress myocardial perfusion imaging compared to invasive coronary angiography with fractional flow reserve meta-analysis.

BACKGROUND: Hemodynamically significant coronary artery disease is an important indication for revascularization. Stress myocardial perfusion imaging is a noninvasive alternative to invasive fractional flow reserve for evaluating hemodynamically significant coronary artery disease. The aim was to determine the diagnostic accuracy of myocardial perfusion imaging by single-photon emission computed tomography, echocardiography, MRI, positron emission tomography, and computed tomography compared with invasive coronary angiography with fractional flow reserve for the diagnosis of hemodynamically significant coronary artery disease. METHODS AND RESULTS: The meta-analysis adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. PubMed, EMBASE, and Web of Science were searched until May 2014. Thirty-seven studies, reporting on 4721 vessels and 2048 patients, were included. Meta-analysis yielded pooled sensitivity, pooled specificity, pooled likelihood ratios (LR), pooled diagnostic odds ratio, and summary area under the receiver operating characteristic curve. The negative LR (NLR) was chosen as the primary outcome. At the vessel level, MRI (pooled NLR, 0.16; 95% confidence interval [CI], 0.13-0.21) was performed similar to computed tomography (pooled NLR, 0.22; 95% CI, 0.12-0.39) and positron emission tomography (pooled NLR, 0.15; 95% CI, 0.05-0.44), and better than single-photon emission computed tomography (pooled NLR, 0.47; 95% CI, 0.37-0.59). At the patient level, MRI (pooled NLR, 0.14; 95% CI, 0.10-0.18) performed similar to computed tomography (pooled NLR, 0.12; 95% CI, 0.04-0.33) and positron emission tomography (pooled NLR, 0.14; 95% CI, 0.02-0.87), and better than single-photon emission computed tomography (pooled NLR, 0.39; 95% CI, 0.27-0.55) and echocardiography (pooled NLR, 0.42; 95% CI, 0.30-0.59). CONCLUSIONS: Stress myocardial perfusion imaging with MRI, computed tomography, or positron emission tomography can accurately rule out hemodynamically significant coronary artery disease and can act as a gatekeeper for invasive revascularization. Single-photon emission computed tomography and echocardiography are less suited for this purpose.

Endogenous assessment of chronic myocardial infarction with T(1ρ)-mapping in patients.

BACKGROUND: Detection of cardiac fibrosis based on endogenous magnetic resonance (MR) characteristics of the myocardium would yield a measurement that can provide quantitative information, is independent of contrast agent concentration, renal function and timing. In ex vivo myocardial infarction (MI) tissue, it has been shown that a significantly higher T(1ρ) is found in the MI region, and studies in animal models of chronic MI showed the first in vivo evidence for the ability to detect myocardial fibrosis with native T(1ρ)-mapping. In this study we aimed to translate and validate T(1ρ)-mapping for endogenous detection of chronic MI in patients. METHODS: We first performed a study in a porcine animal model of chronic MI to validate the implementation of T(1ρ)-mapping on a clinical cardiovascular MR scanner and studied the correlation with histology. Subsequently a clinical protocol was developed, to assess the feasibility of scar tissue detection with native T(1ρ)-mapping in patients (n = 21) with chronic MI, and correlated with gold standard late gadolinium enhancement (LGE) CMR. Four T1ρ-weighted images were acquired using a spin-lock preparation pulse with varying duration (0, 13, 27, 45 ms) and an amplitude of 750 Hz, and a T(1ρ)-map was calculated. The resulting T(1ρ)-maps and LGE images were scored qualitatively for the presence and extent of myocardial scarring using the 17-segment AHA model. RESULTS: In the animal model (n = 9) a significantly higher T(1ρ) relaxation time was found in the infarct region (61 ± 11 ms), compared to healthy remote myocardium (36 ± 4 ms) . In patients a higher T(1ρ) relaxation time (79 ± 11 ms) was found in the infarct region than in remote myocardium (54 ± 6 ms). Overlap in the scoring of scar tissue on LGE images and T(1ρ)-maps was 74%. CONCLUSION: We have shown the feasibility of native T(1ρ)-mapping for detection of infarct area in patients with a chronic myocardial infarction. In the near future, improvements on the T(1ρ)-mapping sequence could provide a higher sensitivity and specificity. This endogenous method could be an alternative for LGE imaging, and provide additional quantitative information on myocardial tissue characteristics.

Cardiac magnetic resonance imaging findings and the risk of cardiovascular events in patients with recent myocardial infarction or suspected or known coronary artery disease: a systematic review of prognostic studies.

The goal of this study was to review the prognostic value of cardiac magnetic resonance (CMR) imaging findings for future cardiovascular events in patients with a recent myocardial infarction (MI) and patients with suspected or known coronary artery disease (CAD). Although the diagnostic value of CMR findings is established, the independent prognostic association with future cardiovascular events remains largely unclear. Studies published by February 2013, identified by systematic MEDLINE and EMBASE searches, were reviewed for associations between CMR findings (left ventricular ejection fraction [LVEF], wall motion abnormalities [WMA], abnormal myocardial perfusion, microvascular obstruction, late gadolinium enhancement, edema, and intramyocardial hemorrhage) and hard events (all-cause mortality, cardiac death, cardiac transplantation, and MI) or major adverse cardiovascular events (MACE) (hard events and other cardiovascular events defined by the authors of the evaluated papers). Fifty-six studies (n = 25,497) were evaluated. For patients with recent MI, too few patients were evaluated to establish associations between CMR findings and hard events. LVEF (range of adjusted hazard ratios [HRs]: 1.03 to 1.05 per % decrease) was independently associated with MACE. In patients with suspected or known CAD, WMA (adjusted HRs: 1.87 to 2.99), inducible perfusion defects (adjusted HRs: 3.02 to 7.77), LVEF (adjusted HRs: 0.72 to 0.82 per 10% increase), and infarction (adjusted HRs: 2.82 to 9.43) were independently associated with hard events, and the presence of inducible perfusion defects was associated with MACE (adjusted HRs: 1.76 to 3.21). The independent predictor of future cardiovascular events for patients with a recent MI was LVEF, and the predictors for patients with suspected or known CAD were WMA, inducible perfusion defects, LVEF, and presence of infarction.

Pre-hospital triage for primary angioplasty: direct referral to the intervention center versus interhospital transport.

OBJECTIVES: We sought to study the impact of direct referral to an intervention center after pre-hospital diagnosis of ST-segment elevation myocardial infarction (STEMI) on treatment intervals and outcome. BACKGROUND: Primary angioplasty has become the preferred reperfusion strategy in STEMI. Ambulance diagnosis and direct referral to an intervention center is an attractive treatment option that has not been studied extensively. METHODS: Consecutive pre-hospital patients with STEMI, who were referred to our intervention center for primary angioplasty between 2005 and 2007, were studied. After pre-hospital diagnosis, patients were either directly transported to our center or referred through a nonintervention center. The catheterization laboratory was activated before transport to the intervention center. RESULTS: Of the 581 patients referred, 454 (78%) came with direct transport and 127 (22%) through a nonintervention center. Direct transport was associated with a higher proportion of patients treated within the 90-min time window of the STEMI guidelines: 82% versus 23% (p < 0.01). Patients directly transported had a significantly shorter median symptom-to-balloon time of 149 min (Interquartile range: 118 to 197 min) versus 219 min (interquartile range: 178 to 315 min), p < 0.01, a higher post-procedural Thrombolysis In Myocardial Infarction (TIMI) flow grade 3 rate (92% vs. 84%; p = 0.03), and a lower 1-year mortality rate (7% vs. 13%; p = 0.03). Direct transport to the intervention center was independently associated with the symptom-to-balloon time, which in turn was an independent predictor of post-procedural TIMI flow grade 3, a strong prognosticator of outcome. CONCLUSIONS: After ambulance-based diagnosis of STEMI, direct transport to an intervention center with pre-hospital notification of the catheterization laboratory more than triples the proportion of patients treated within the time window of the guidelines. Time to balloon was an independent predictor of post-procedural TIMI flow grade 3, which underscores the need to reduce treatment delays.

Cardiovascular magnetic resonance parameters of atherosclerotic plaque burden improve discrimination of prior major adverse cardiovascular events.

AIMS: Patients with prior major cardiovascular or cerebrovascular events (MACE) are more likely to have future recurrent events independent of traditional cardiovascular disease risk factors. The purpose of this study was to determine if patients with traditional risk factors and prior MACE had increased cardiovascular magnetic resonance (CMR) plaque burden measures compared to patients with risk factors but no prior events. METHODS AND RESULTS: Black blood carotid and thoracic aorta images were obtained from 195 patients using a rapid extended coverage turbo spin echo sequence. CMR measures of plaque burden were obtained by tracing lumen and outer vessel wall contours. Patients with prior MACE had significantly higher MR plaque burden (wall thickness, wall area and normalized wall index) in carotids and thoracic aorta compared to those without prior MACE (Wall thickness carotids: 1.03 +/- 0.03 vs. 0.93+/- 0.03, p = 0.001; SD wall thickness carotids: 0.137 +/- 0.0008 vs. 0.102 +/- 0.0004, p < 0.001; wall thickness aorta: 1.63 +/- 0.10 vs. 1.50 +/- 0.04, p = 0.009; SD wall thickness aorta: 0.186 +/- 0.035 vs. 0.139 +/- 0.012, p = 0.009 respectively). Plaque burden (wall thickness) and plaque eccentricity (standard deviation of wall thickness) of carotid arteries were associated with prior MACE after adjustment for age, sex, and traditional risk factors. Area under ROC curve (AUC) for discriminating prior MACE improved by adding plaque eccentricity to models incorporating age, sex, and traditional CVD risk factors as model inputs (AUC = 0.79, p = 0.05). CONCLUSION: A greater plaque burden and plaque eccentricity is prevalent among patients with prior MACE.

Cross-sectional, prospective study of MRI reproducibility in the assessment of plaque burden of the carotid arteries and aorta.

BACKGROUND: The reliability of imaging techniques to assess early atherosclerosis remains unclear. We did a cross-sectional, prospective study to test reproducibility of MRI when imaging arteries, to assess risk of cardiovascular disease and correlations with age and sex. METHODS: Between January 2003 and December 2006 we performed black-blood MRI of both common carotid arteries and the thoracic descending aorta in patients with cardiovascular risk factors who were referred from clinics in New York, NY, USA. Mean wall area, wall thickness, lumen area, total vessel area, and ratio of the mean wall area to the mean total vessel area (WA/TVA) were manually measured. Reproducibility within and between readers was tested on subsets of images from randomly chosen patients. RESULTS: MRI was performed on 300 patients. Intrareader reproducibility, assessed in images from 20 patients, was high for all parameters (intraclass correlation coefficients >0.8), except WA/TVA ratio in the descending aorta. The inter-reader reproducibility, assessed in images from 187 patients, was acceptable (intraclass correlation coefficients >0.7) for the mean wall, lumen, and total vessel areas. Values for all MRI parameters in all vessels increased with increasing age for both sexes (all P <0.0005) but were always significantly higher in men than in women, except for aortic mean wall thickness and WA/TVA ratio in the carotid arteries. Mean wall area values correlated well between the carotid arteries and aorta, reflecting the systemic nature of atherosclerosis. CONCLUSIONS: Our findings support MRI as a reproducible measurement of plaque burden and demonstrate the systemic distribution of atherosclerosis.