Worldwide variation in cardiovascular magnetic resonance practice models.

INTRODUCTION: The use of cardiovascular magnetic resonance (CMR) for diagnosis and management of a broad range of cardiac and vascular conditions has quickly expanded worldwide. It is essential to understand how CMR is utilized in different regions around the world and the potential practice differences between high-volume and low-volume centers. METHODS: CMR practitioners and developers from around the world were electronically surveyed by the Society for Cardiovascular Magnetic Resonance (SCMR) twice, requesting data from 2017. Both surveys were carefully merged, and the data were curated professionally by a data expert using cross-references in key questions and the specific media access control IP address. According to the United Nations classification, responses were analyzed by region and country and interpreted in the context of practice volumes and demography. RESULTS: From 70 countries and regions, 1092 individual responses were included. CMR was performed more often in academic (695/1014, 69%) and hospital settings (522/606, 86%), with adult cardiologists being the primary referring providers (680/818, 83%). Evaluation of cardiomyopathy was the top indication in high-volume and low-volume centers (p = 0.06). High-volume centers were significantly more likely to list evaluation of ischemic heart disease (e.g., stress CMR) as a primary indicator compared to low-volume centers (p < 0.001), while viability assessment was more commonly listed as a primary referral reason in low-volume centers (p = 0.001). Both developed and developing countries noted cost and competing technologies as top barriers to CMR growth. Access to scanners was listed as the most common barrier in developed countries (30% of responders), while lack of training (22% of responders) was the most common barrier in developing countries. CONCLUSION: This is the most extensive global assessment of CMR practice to date and provides insights from different regions worldwide. We identified CMR as heavily hospital-based, with referral volumes driven primarily by adult cardiology. Indications for CMR utilization varied by center volume. Efforts to improve the adoption and utilization of CMR should include growth beyond the traditional academic, hospital-based location and an emphasis on cardiomyopathy and viability assessment in community centers.

An international multicenter comparison of time-SLIP unenhanced MR angiography and contrast-enhanced CT angiography for assessing renal artery stenosis: the renal artery contrast-free trial.

OBJECTIVE: The unenhanced MR angiography (MRA) technique time-spatial labeling inversion pulse (time-SLIP) may provide a safe alternative for evaluating the renal arteries for stenosis. This international multicenter trial tested the hypothesis that time-SLIP unenhanced MRA is accurate and robust for assessing the renal arteries for stenosis in comparison with contrast-enhanced CT angiography (CTA). SUBJECTS AND METHODS: Four centers (United States, Europe, Asia) enrolled 75 patients (average age ± SD, 58 ± 13 years; 41 [55%] men and 34 [45%] women). Each patient underwent abdominal contrast-enhanced CTA and abdominal unenhanced MRA using time-SLIP with balanced steady-state free precession. All images were visually assessed for quality (arterial signal intensity) and for the absence or presence of renal artery stenosis (≤ 50% or > 50% stenosis, respectively). In addition, for arteries with any visible disease, the severity of the stenosis was quantified. Two blinded readers evaluated each study. No arteries were excluded from analysis. RESULTS: Unenhanced MRA image quality was excellent for 56 of 75 patients (75%) and good for 16 of 75 patients (21%). CTA was used as the reference standard and showed that 23 of 161 renal arteries (14.3%) had stenosis > 50%. Unenhanced MRA correctly classified 17 of the 23 renal arteries with > 50% stenosis and correctly classified 128 of the 138 renal arteries as not having disease (≤ 50% stenosis) to yield a sensitivity of 74%, specificity of 93%, and accuracy of 90% (χ(2) = 0.56; p = 0.45, no statistically significant difference). Of the 16 misclassified arteries, only three had a clinically relevant misclassification (CTA ≥ 70% stenosis and unenhanced MRA ≤ 50% stenosis or unenhanced MRA ≥ 70% stenosis and CTA ≤ 50% stenosis). On average, measured stenotic severity (n = 28 arteries) was similar for unenhanced MRA (64% ± 17%) and CTA (62% ± 16%) (p = 0.51). CONCLUSION: Compared with contrast-enhanced CTA, the unenhanced MRA technique time-SLIP shows promise for assessing the renal arteries for stenosis. The unenhanced MRA technique time-SLIP may provide a safe alternative for evaluating the renal arteries for stenosis.

Recent Trends and Potential Drivers of Non-invasive Cardiovascular Imaging Use in the United States of America and England.

Background: Non-invasive Cardiovascular imaging (NICI), including cardiovascular magnetic resonance (CMR) imaging provides important information to guide the management of patients with cardiovascular conditions. Current rates of NICI use and potential policy determinants in the United States of America (US) and England remain unexplored. Methods: We compared NICI activity in the US (Medicare fee-for-service, 2011-2015) and England (National Health Service, 2012-2016). We reviewed recommendations related to CMR from Clinical Practice Guidelines, Appropriate Use Criteria (AUC), and Choosing Wisely. We then categorized recommendations according to whether CMR was the only recommended NICI technique (substitutable indications). Reimbursement policies in both settings were systematically collated and reviewed using publicly available information. Results: The 2015 rate of NICI activity in the US was 3.1 times higher than in England (31,055 vs. 9,916 per 100,000 beneficiaries). The proportion of CMR of all NICI was small in both jurisdictions, but nuclear cardiac imaging was more frequent in the US in absolute and relative terms. American and European CPGs were similar, both in terms of number of recommendations and proportions of indications where CMR was not the only recommended NICI technique (substitutable indications). Reimbursement schemes for NICI activity differed for physicians and hospitals between the two settings. Conclusions: Fee-for-service physician compensation in the US for NICI may contribute to higher NICI activity compared to England where physicians are salaried. Reimbursement arrangements for the performance of the test may contribute to the higher proportion of nuclear cardiac imaging out of the total NICI activity. Differences in CPG recommendations appear not to explain the variation in NICI activity between the US and England.

Performance of delayed-enhancement magnetic resonance imaging with gadoversetamide contrast for the detection and assessment of myocardial infarction: an international, multicenter, double-blinded, randomized trial.

BACKGROUND: The identification and assessment of myocardial infarction (MI) are important for therapeutic and prognostic purposes, yet current recommended diagnostic strategies have significant limitations. We prospectively tested the performance of delayed-enhancement magnetic resonance imaging (MRI) with gadolinium-based contrast for the detection of MI in an international, multicenter trial. METHODS AND RESULTS: Patients with their first MI were enrolled in an acute (< or = 16 days after MI; n=282) or chronic (17 days to 6 months; n=284) arm and then randomized to 1 of 4 doses of gadoversetamide: 0.05, 0.1, 0.2, or 0.3 mmol/kg. Standard delayed-enhancement MRI was performed before contrast (control) and 10 and 30 minutes after gadoversetamide. For blinded analysis, precontrast and postcontrast MRIs were randomized and then scored for enhanced regions by 3 independent readers not associated with the study. The infarct-related artery perfusion territory was scored from x-ray angiograms separately. In total, 566 scans were performed in 26 centers using commercially available scanners from all major US/European vendors. All scans were included in the analysis. The sensitivity of MRI for detecting MI increased with rising dose of gadoversetamide (P<0.0001), reaching 99% (acute) and 94% (chronic) after contrast compared with 11% before contrast. Likewise, the accuracy of MRI for identifying MI location (compared with infarct-related artery perfusion territory) increased with rising dose of gadoversetamide (P<0.0001), reaching 99% (acute) and 91% (chronic) after contrast compared with 9% before contrast. For gadoversetamide doses > or = 0.2 mmol/kg, 10- and 30-minute images provided equal performance, and peak creatine kinase-MB levels correlated with MRI infarct size (P<0.0001). CONCLUSIONS: Gadoversetamide-enhanced MRI using doses of > or = 0.2 mmol/kg is effective in the detection and assessment of both acute and chronic MI. This study represents the first multicenter trial designed to evaluate an imaging approach for detecting MI.

Rapid detection of myocardial infarction by subsecond, free-breathing delayed contrast-enhancement cardiovascular magnetic resonance.

BACKGROUND: An ultrafast, delayed contrast-enhancement cardiovascular magnetic resonance technique that can acquire subsecond, "snapshot" images during free breathing (subsecond) is becoming widely available. This technique provides myocardial infarction (MI) imaging with complete left ventricular coverage in < 30 seconds. However, the accuracy of this technique is unknown. METHODS AND RESULTS: We prospectively compared subsecond imaging with routine breath-hold delayed contrast-enhancement cardiovascular magnetic resonance (standard) in consecutive patients. Two cohorts with unambiguous standards of truth were prespecified: (1) patients with documented prior MI (n=135) and (2) patients without MI and with low likelihood of coronary disease (lowest Framingham risk category; n=103). Scans were scored masked to identity and clinical information. Sensitivity, specificity, and accuracy of subsecond imaging for MI diagnosis were 87%, 96%, and 91%, respectively. Compared with the standard technique (98%, 100%, 99%), the subsecond technique had modestly reduced sensitivity (P=0.0001), but specificity was excellent. Missed infarcts were generally small or subendocardial (87%). Overall, regional transmural extent of infarction scores were highly concordant (2083/2294; 91%); however, 51 of 337 regions (15%) considered predominantly infarcted (> 50% transmural extent of infarction) by the standard technique were considered viable (< or = 25% transmural extent of infarction) by the subsecond technique. Quantitative analysis demonstrated moderately reduced contrast-to-noise ratios for subsecond imaging between infarct and remote myocardium (12.0+/-7.2 versus 20.1+/-6.6; P<0.0001) and infarct and left ventricular cavity (-2.5+/-2.7 versus 3.6+/-3.7; P<0.0001). CONCLUSIONS: MI can be rapidly detected by subsecond delayed contrast-enhancement cardiovascular magnetic resonance during free breathing with high accuracy. This technique could be considered the preferred approach in patients who are more acutely ill or unable to hold their breath. However, compared with standard imaging, sensitivity is mildly reduced, and the transmural extent of infarction may be underestimated.

Respiratory motion and cardiac arrhythmia effects on diagnostic accuracy of myocardial delayed-enhanced MR imaging in canines.

PURPOSE: To prospectively compare in canines the diagnostic accuracy for myocardial infarction (MI) of standard delayed-enhancement (DE) magnetic resonance (MR) imaging versus that of subsecond DE MR imaging with and without breath holding and/or cardiac arrhythmia, with histologic findings or absence of surgical creation of MI as the reference standard. MATERIALS AND METHODS: This study was approved by the Institutional Animal Care and Use Committee; 21 canines were imaged with one standard and two subsecond DE MR techniques in four conditions: condition 1, breath holding and steady gating; 2, non-breath holding and steady gating; 3, breath holding and irregular heart rhythm; and 4, non-breath holding and irregular heart rhythm. Images were randomized and scored for diagnostic accuracy, image quality, and observer confidence. Sensitivity, specificity, and diagnostic accuracy for MI detection were calculated for each technique and clinical condition separately. The chi(2), paired t, and McNemar tests were used for comparisons. RESULTS: Fifteen dogs had MIs. Among conditions 2-4, differences were not significant (P > .05); data were pooled and referred to as group B. Condition 1 was group A. Accuracy, image quality, and observer confidence, respectively, for standard DE MR imaging were 96%, 3.7 +/- 0.8, and 2.7 +/- 0.6 in group A but only 74%, 2.4 +/- 0.8, and 1.8 +/- 0.7 in group B (P < or = .004 for each). Corresponding scores for subsecond techniques were unaffected by respiratory motion and/or arrhythmia. Subsecond techniques had higher accuracy (82% and 86% vs 74%), better image quality (3.9 +/- 0.7 and 3.2 +/- 0.8 vs 2.4 +/- 0.8), and greater confidence (2.4 +/- 0.7 and 2.1 +/- 0.7 vs 1.8 +/- 0.7) (P < or = .0002 for each) than standard DE MR imaging. In group A, standard performed better than subsecond DE MR imaging. CONCLUSION: Standard DE MR imaging is appropriate for MI detection with breath holding and regular heart rhythm, while subsecond techniques are appropriate with an irregular heart rhythm and when breath holding is not possible.

Assessment of no-reflow regions using cardiac MRI.

Ischemic myocardial injury can be broadly characterized as either reversible or irreversible. Within irreversibly injured (infarcted) regions microvascular perfusion can vary from nearly normal to nearly zero, even in the presence of an open infarct-related artery ('no-reflow'). Historically, non-invasive assessment of heterogeneous microvascular perfusion within myocardial infarcts has been problematic. More recently, however, contrast-enhanced MRI has emerged as a promising approach to the examination of these regions in patients with myocardial infarction. In this review we highlight a number of important animal and human studies of no-reflow regions examined using contrast-enhanced MRI. These studies provide evidence that contrast- enhanced MRI can accurately characterize the presence and spatial extent of no-reflow regions, discriminate between areas of necrosis with and without no-reflow, and provide clinically meaningful predictive information regarding left ventricular remodeling and patient outcome.

Acute myocardial infarction: safety of cardiac MR imaging after percutaneous revascularization with stents.

PURPOSE: To retrospectively determine the safety of cardiac magnetic resonance (MR) imaging performed early (<14 days) after coronary stent implantation in patients with acute myocardial infarction (AMI). MATERIALS AND METHODS: This HIPPA-compliant study was approved by the institutional review board; the informed consent requirement was waived. Consecutive patients with AMI who underwent cardiac MR imaging (study group) shortly after stent implantation (median, 3 days) were compared with control subjects who did not undergo MR imaging and were matched for clinical factors and angiographic extent of coronary disease. A 1.5-T MR imager was used to evaluate cine function, perfusion, and viability. Rates of death, nonfatal myocardial infarction, or revascularization 30 days and 6 months after stent implantation were compared with chi(2) analysis. RESULTS: The study group consisted of 66 patients (median age, 56 years; 17 women) with 97 stents, 38 (39%) of which were drug eluting. The control group included 124 patients (median age, 58 years; 23% women) with 197 stents, 21 (10.7%) of which were drug eluting. There was no significant (P = .13) difference in the combined end point of death, nonfatal myocardial infarction, or revascularization between the study (2.0% [95% confidence interval: 0.0%, 4.5%]) and control (6.5% [95% confidence interval: 1.6%, 11.3%]) groups at 30-day follow-up. The event-free survival rate at 6-month follow-up was 91% in the study group and 83.7% in the control group (P = .18). Considering the end points separately, there was no difference in the event rate at 30-day or 6-month follow-up between groups. No adverse cardiovascular events occurred in patients with drug-eluting stents who underwent MR imaging. CONCLUSION: Cardiac MR imaging performed shortly after AMI and percutaneous revascularization with bare metal or drug-eluting stents appears safe. The risk of adverse cardiovascular events is low and similar to that in patients who do not undergo MR imaging.

Apolipoprotein L-I is positively associated with hyperglycemia and plasma triglycerides in CAD patients with low HDL.

Apolipoprotein L-I (apoL-I) is present on a subset of HDL particles and is positively correlated with plasma triglycerides (TGs). We measured plasma apoL-I levels in coronary artery disease (CAD) subjects with low HDL who were enrolled in an angiographic CAD prevention trial. At baseline, apoL-I levels (n = 136; range, 2.2-64.1 mug/ml) were right skewed with a large degree of variability. Multivariate analysis for biological determinants of apoL-I revealed that the log of VLDL-TG (+0.17; P < 0.05) and hyperglycemia (HG; +0.26; P < 0.005) independently predicted apoL-I level. Hyperglycemic patients (n = 24) had mean apoL-I levels >50% higher than normoglycemic subjects (n = 112; 13.2 vs. 8.3 mug/ml, respectively; P < 0.001). No relationship between apoL-I level and change in CAD was found (r = 0.06, P = 0.49). Simvastatin-niacin therapy did not alter apoL-I levels (n = 34; P = 0.27), whereas antioxidant vitamins alone increased apoL-I by >50% (n = 36; P < 0.01). Genotyping of a known apoL-I polymorphism (Lys166Glu) did not independently account for any of the variability in apoL-I levels. In conclusion, we found TG and HG to be the strongest predictors of apoL-I within a dyslipidemic CAD population. These data provide further characterization of the novel HDL-associated apoL-I.