Effectiveness of integrating delayed computed tomography angiography imaging for left atrial appendage thrombus exclusion into the care of patients undergoing ablation of atrial fibrillation

BACKGROUND

Computed tomography angiography (CTA) can identify and rule out left atrial appendage (LAA) thrombus when delayed imaging is also performed.

OBJECTIVE

In patients referred for CTA to evaluate pulmonary vein anatomy before the ablation of atrial fibrillation (AF) or left atrial flutter (LAFL), we sought to determine the effectiveness of a novel clinical protocol for integrating results of CTA delayed LAA imaging into preprocedure care.

METHODS

After making delayed imaging of the LAA part of our routine preablation CTA protocol, we integrated early reporting of preablation CTA LAA imaging results into clinical practice as part of a formal protocol in June 2013. We then analyzed the effectiveness of this protocol by evaluating 320 AF/LAFL ablation patients with CTA imaging during the time period 2012-2014.

RESULTS

In CTA patients with delayed LAA imaging, the sensitivity and negative predictive values for LAA thrombus using intracardiac echocardiography or transesophageal echocardiography (TEE) as the reference standard were both 100%. Intracardiac echocardiography during ablation confirmed the absence of thrombus in patients with negative CTA or negative TEE results. No patients with either negative CTA results or equivocal CTA results combined with negative TEE results had strokes or transient ischemic attacks. Overall, the need for TEE procedures decreased from 57.5% to 24.0% during the 3-year period because of the CTA protocol.

CONCLUSION

Clinical integration of CTA delayed LAA imaging into the care of patients having catheter ablation of AF or LAFL is feasible, safe, and effective. Such a protocol could be used broadly to improve patient care.

Survey of the therapeutic approach and efficacy of pentosan polysulfate for the prevention and treatment of equine osteoarthritis in veterinary practice in Australia

OBJECTIVE

To survey veterinary practitioners in Australia on how they administer pentosan polysulfate (PPS) to horses and their perceptions of the efficacy of PPS for: the prevention and treatment of osteoarthritis (OA), the treatment of OA when PPS is combined with other drugs, and the efficacy of PPS compared with other disease-modifying osteoarthritic drugs.

DESIGN

Practitioners were contacted by email, which contained a link to an online survey.

RESULTS

A total of 76 responses (34.5%) to the survey were received. Respondents most commonly used PPS as prophylactic therapy prior to competition (80.3%). As a prophylactic agent, PPS was considered by 48.2% of respondents to have high efficacy. The most common dose regimen for prevention and treatment of OA was 3 mg/kg, intramuscularly, once weekly for 4 weeks followed by monthly injections. Most respondents (78%) combined PPS with other drugs for treatment of OA. Intra-articular corticosteroids and hyaluronate (HA) was the most common drug combination used with PPS. PPS was preferred as a prophylactic agent when compared with HA (88.7% vs 11.3%). For treating OA, 83% of respondents considered a combination of PPS, HA and glucosamine to be more efficacious than PPS alone. However, the most common reason not to use this combination was cost (79.1%).

CONCLUSION

All respondents used PPS for prophylaxis and/or treatment of OA despite limited published scientific evidence proving its efficacy in horses. Further research is necessary to provide evidence of the clinical efficacy of PPS for the prevention and treatment of OA in horses.

Role of Cardiac MR Imaging in Cardiomyopathies

Cardiac MR imaging has made major inroads in the new millennium in the diagnosis and assessment of prognosis for patients with cardiomyopathies. Imaging of left and right ventricular structure and function and tissue characterization with late gadolinium enhancement (LGE) as well as T1 and T2 mapping enable accurate diagnosis of the underlying etiology. In the setting of coronary artery disease, either transmurality of LGE or contractile reserve in response to dobutamine can assess the likelihood of recovery of function after revascularization. The presence of scar reduces the likelihood of a response to medical therapy and to cardiac resynchronization therapy in heart failure. The presence and extent of LGE relate to overall cardiovascular outcome in cardiomyopathies. A major role for cardiac MR imaging in cardiomyopathies is to identify myocardial scar for diagnostic and prognostic purposes.

Quantification of LV function and mass by cardiovascular magnetic resonance: multi-center variability and consensus contours

BACKGROUND

High reproducibility of LV mass and volume measurement from cine cardiovascular magnetic resonance (CMR) has been shown within single centers. However, the extent to which contours may vary from center to center, due to different training protocols, is unknown. We aimed to quantify sources of variation between many centers, and provide a multi-center consensus ground truth dataset for benchmarking automated processing tools and facilitating training for new readers in CMR analysis.

METHODS

Seven independent expert readers, representing seven experienced CMR core laboratories, analyzed fifteen cine CMR data sets in accordance with their standard operating protocols and SCMR guidelines. Consensus contours were generated for each image according to a statistical optimization scheme that maximized contour placement agreement between readers.

RESULTS

Reader-consensus agreement was better than inter-reader agreement (end-diastolic volume 14.7 ml vs 15.2-28.4 ml; end-systolic volume 13.2 ml vs 14.0-21.5 ml; LV mass 17.5 g vs 20.2-34.5 g; ejection fraction 4.2 % vs 4.6-7.5 %). Compared with consensus contours, readers were very consistent (small variability across cases within each reader), but bias varied between readers due to differences in contouring protocols at each center. Although larger contour differences were found at the apex and base, the main effect on volume was due to small but consistent differences in the position of the contours in all regions of the LV.

CONCLUSIONS

A multi-center consensus dataset was established for the purposes of benchmarking and training. Achieving consensus on contour drawing protocol between centers before analysis, or bias correction after analysis, is required when collating multi-center results.

Effect of microvascular obstruction and intramyocardial hemorrhage by CMR on LV remodeling and outcomes after myocardial infarction: a systematic review and meta-analysis

The goal of this systematic analysis is to provide a comprehensive review of the current cardiac magnetic resonance data on microvascular obstruction (MVO) and intramyocardial hemorrhage (IMH). Data related to the association of MVO and IMH in patients with acute myocardial infarction (MI) with left ventricular (LV) function, volumes, adverse LV remodeling, and major adverse cardiac events (MACE) were critically analyzed. MVO is associated with a lower ejection fraction, increased ventricular volumes and infarct size, and a greater risk of MACE. Late MVO is shown to be a stronger prognostic marker for MACE and cardiac death, recurrent MI, congestive heart failure/heart failure hospitalization, and follow-up LV end-systolic volumes than early MVO. IMH is associated with LV remodeling and MACE on pooled analysis, but because of limited data and heterogeneity in study methodology, the effects of IMH on remodeling require further investigation.

Non-Cartesian balanced steady-state free precession pulse sequences for real-time cardiac MRI

PURPOSE

To develop a new spiral-in/out balanced steady-state free precession (bSSFP) pulse sequence for real-time cardiac MRI and compare it with radial and spiral-out techniques.

METHODS

Non-Cartesian sampling strategies are efficient and robust to motion and thus have important advantages for real-time bSSFP cine imaging. This study describes a new symmetric spiral-in/out sequence with intrinsic gradient moment compensation and SSFP refocusing at TE = TR/2. In vivo real-time cardiac imaging studies were performed to compare radial, spiral-out, and spiral-in/out bSSFP pulse sequences. Furthermore, phase-based fat/water separation taking advantage of the refocusing mechanism of the spiral-in/out bSSFP sequence was also studied.

RESULTS

The image quality of the spiral-out and spiral-in/out bSSFP sequences was improved with off-resonance and k-space trajectory correction. The spiral-in/out bSSFP sequence had the highest signal-to-noise ratio (SNR), contrast-to-noise ratio, and image quality ratings, with spiral-out bSSFP sequence second in each category and the radial bSSFP sequence third. The spiral-in/out bSSFP sequence provides separated fat and water images with no additional scan time.

CONCLUSIONS

In this study, a new spiral-in/out bSSFP sequence was developed and tested. The superiority of spiral bSSFP sequences over the radial bSSFP sequence in terms of SNR and reduced artifacts was demonstrated in real-time MRI of cardiac function without image acceleration.

Cardiac MRI assessment of myocardial perfusion

Coronary artery disease is the most common cause of mortality and morbidity around the globe. Assessment of myocardial perfusion to diagnose ischemia is commonly performed in symptomatic patients prior to referral for cardiac catheterization. Among other noninvasive imaging modalities, cardiac MRI (CMR) is emerging as a highly sensitive and specific test for myocardial ischemia and infarction. Resting perfusion on CMR is used to evaluate for microvascular obstruction, which is shown to predict adverse left ventricular remodeling and cardiac events after acute myocardial infarction. This article summarizes the current understanding of CMR perfusion.

Arterial spin labeling perfusion cardiovascular magnetic resonance of the calf in peripheral arterial disease: cuff occlusion hyperemia vs exercise

BACKGROUND

Assessment of calf muscle perfusion requires a physiological challenge. Exercise and cuff-occlusion hyperemia are commonly used methods, but it has been unclear if one is superior to the other. We hypothesized that post-occlusion calf muscle perfusion (Cuff) with pulsed arterial spin labeling (PASL) cardiovascular magnetic resonance (CMR) at 3 Tesla (T) would yield greater perfusion and improved reproducibility compared to exercise hyperemia in studies of peripheral arterial disease (PAD).

METHODS

Exercise and Cuff cohorts were independently recruited. PAD patients had an ankle brachial index (ABI) between 0.4-0.9. Controls (NL) had no risk factors and ABI 0.9-1.4. Subjects exercised until exhaustion (15 NL-Ex, 15 PAD-Ex) or had a thigh cuff inflated for 5 minutes (12 NL-Cuff, 11 PAD-Cuff). Peak exercise and average cuff (Cuff mean ) perfusion were compared. Six participants underwent both cuff and exercise testing. Reproducibility was tested in 8 Cuff subjects (5 NL, 3 PAD).

RESULTS

Controls had greater perfusion than PAD independent of stressor (NL-Ex 74 ± 21 vs. PAD-Ex 43 ± 10, p = 0.01; NL-Cuff mean 109 ± 39 vs. PAD-Cuff mean 34 ± 17 ml/min-100 g, p < 0.001). However, there was no difference between exercise and Cuff mean perfusion within groups (p > 0.6). Results were similar when the same subjects had the 2 stressors performed. Cuff mean had superior reproducibility (Cuff mean ICC 0.98 vs. Exercise ICC 0.87) and area under the receiver operating characteristic curve (Cuff mean 0.992 vs. Exercise 0.905).

CONCLUSIONS

Cuff hyperemia differentiates PAD patients from controls, as does exercise stress. Cuff mean and exercise calf perfusion values are similar. Cuff occlusion hyperemia has superior reproducibility and thus may be the preferred stressor.

Singular Value Decomposition Applied to Cardiac Strain from MR Imaging for Selection of Optimal Cardiac Resynchronization Therapy Candidates

PURPOSE

To use singular value decomposition (SVD) in heart failure (HF) to reveal primary spatiotemporal strain patterns in the left ventricle (LV), then develop and test a time-independent metric of cardiac dyssynchrony on the basis of the circumferential uniformity ratio estimate (CURE) computed with SVD (CURE-SVD) in both a canine model of HF with or without left bundle branch block (LBBB) and a clinical cohort referred for cardiac resynchronization therapy (CRT).

MATERIALS AND METHODS

The research was approved by the institutional review board and conformed with HIPAA requirements. All subjects provided informed consent. In both the canine model (n = 13) and the clinical cohort (80 CRT candidates; mean age, 65.2 years; range, 18.5-86.9 years), regional strains were derived by using cardiac magnetic resonance (MR) displacement encoding with stimulated echoes. CURE-SVD was compared with the standard CURE (averaged over systolic phases). Statistical methods included the Wilcoxon rank-sum test, Hodges-Lehmann estimator, Bland-Altman test, multivariable logistic regression, and receiver operating characteristic analysis.

RESULTS

In the canine model, the median difference in CURE-SVD (range, 0-1) for LBBB-HF group versus narrow-QRS-HF group (-0.40; 95% confidence interval [CI]: -0.79, -0.31) was similar to that for CURE (-0.43; 95% CI: -0.72, -0.34]). In 80 CRT candidates, CURE-SVD and CURE were highly correlated (r = 0.90; P < .0001). The multivariable model for CRT response with CURE-SVD demonstrated excellent performance without the need for time averaging over cardiac phases (area under the receiver operating characteristic curve = 0.96, P < .0001).

CONCLUSION

SVD of circumferential strain in HF identifies primary LV spatiotemporal contraction patterns with minimal user input, while the time-independent CURE-SVD parameter has excellent performance in a canine model of dyssynchrony and is strongly associated with CRT response in patients with HF.

Increased extracellular volume and altered mechanics are associated with LVH in hypertensive heart disease, not hypertension alone

OBJECTIVES

The goal of this study was to assess the relationship among extracellular volume (ECV), native T1, and systolic strain in hypertensive patients with left ventricular hypertrophy (HTN LVH), hypertensive patients without LVH (HTN non-LVH), and normotensive controls.

BACKGROUND

Diffuse myocardial fibrosis in HTN LVH patients, as reflected by increased ECV and native T1, may be an underlying mechanism contributing to increased cardiovascular risk compared with HTN non-LVH subjects and controls. Furthermore, increased diffuse fibrosis in HTN LVH subjects may be associated with reduced peak systolic and early diastolic strain rate compared with the other 2 groups.

METHODS

T1 mapping was performed in 20 HTN LVH (mean age, 55 ± 11 years), 23 HTN non-LVH (mean age, 61 ± 12 years), and 22 control subjects (mean age, 54 ± 7 years) on a Siemens 1.5-T Avanto (Siemens Healthcare, Erlangen, Germany) using a previously validated modified look-locker inversion-recovery pulse sequence. T1 was measured pre-contrast and 10, 15, and 20 min after injection of 0.15 mmol/kg gadopentetate dimeglumine, and the mean ECV and native T1 were determined for each subject. Measurement of circumferential strain parameters were performed using cine displacement encoding with stimulated echoes.

RESULTS

HTN LVH subjects had higher native T1 compared with controls (p < 0.05). HTN LVH subjects had higher ECV compared with HTN non-LVH subjects and controls (p < 0.05). Peak systolic circumferential strain and early diastolic strain rates were reduced in HTN LVH subjects compared with HTN non-LVH subjects and controls (p < 0.05). Increased levels of ECV and native T1 were associated with reduced peak systolic and early diastolic circumferential strain rate across all subjects.

CONCLUSIONS

HTN LVH patients had higher ECV, longer native T1 and associated reduction in peak systolic circumferential strain, and early diastolic strain rate compared with HTN non-LVH and control subjects. Measurement of ECV and native T1 provide a noninvasive assessment of diffuse fibrosis in hypertensive heart disease.

Simplifying cardiovascular magnetic resonance pulse sequence terminology

We propose a set of simplified terms to describe applied Cardiovascular Magnetic Resonance (CMR) pulse sequence techniques in clinical reports, scientific articles and societal guidelines or recommendations. Rather than using various technical details in clinical reports, the description of the technical approach should be based on the purpose of the pulse sequence. In scientific papers or other technical work, this should be followed by a more detailed description of the pulse sequence and settings. The use of a unified set of widely understood terms would facilitate the communication between referring physicians and CMR readers by increasing the clarity of CMR reports and thus improve overall patient care. Applied in research articles, its use would facilitate non-expert readers' understanding of the methodology used and its clinical meaning.

High-risk plaque in the superficial femoral artery of people with peripheral artery disease: prevalence and associated clinical characteristics

OBJECTIVE

We used magnetic resonance imaging (MRI) to study the prevalence and associated clinical characteristics of high-risk plaque (defined as presence of lipid-rich necrotic core [LRNC] and intraplaque hemorrhage) in the superficial femoral arteries (SFA) among people with peripheral artery disease (PAD).

BACKGROUND

The prevalence and clinical characteristics associated with high-risk plaque in the SFA are unknown.

METHODS

Three-hundred-three participants with PAD underwent MRI of the proximal SFA using a 1.5 T S platform. Twelve contiguous 2.5 mm cross-sectional images were obtained.

RESULTS

LRNC was present in 68 (22.4%) participants. Only one had intra-plaque hemorrhage. After adjusting for age and sex, smoking prevalence was higher among adults with LRNC than among those without LRNC (35.9% vs. 21.4%, p = 0.02). Among participants with vs. without LRNC there were no differences in mean percent lumen area (31% vs. 33%, p = 0.42), normalized mean wall area (0.71 vs. 0.70, p = 0.67) or maximum wall area (0.96 vs. 0.92, p = 0.54) in the SFA. Among participants with LRNC, cross-sectional images containing LRNC had a smaller percent lumen area (33% ± 1% vs. 39% ± 1%, p < 0.001), greater normalized mean wall thickness (0.25 ± 0.01 vs. 0.22 ± 0.01, p < 0.001), and greater normalized maximum wall thickness (0.41 ± 0.01 vs. 0.31 ± 0.01, p < 0.001), compared to cross-sectional images without LRNC.

CONCLUSIONS

Fewer than 25% of adults with PAD had high-risk plaque in the proximal SFA using MRI. Smoking was the only clinical characteristic associated with presence of LRNC. Further study is needed to determine the prognostic significance of LRNC in the SFA.

CLINICAL TRIAL REGISTRATION-URL

http://www.clinicaltrials.gov. Unique identifier: NCT00520312.

Collateral vessel number, plaque burden, and functional decline in peripheral artery disease

Associations of collateral vessels and lower extremity plaque with functional decline are unknown. Among people with peripheral artery disease (PAD), we determined whether greater superficial femoral artery (SFA) plaque burden combined with fewer lower extremity collateral vessels was associated with faster functional decline, compared to less plaque and/or more numerous collateral vessels. A total of 226 participants with ankle-brachial index (ABI) <1.00 underwent magnetic resonance imaging of lower extremity collateral vessels and cross-sectional imaging of the proximal SFA. Participants were categorized as follows: Group 1 (best), maximum plaque area < median and collateral vessel number ≥6 (median); Group 2, maximum plaque area < median and collateral vessel number <6; Group 3, maximum plaque area > median and collateral vessel number ≥6; Group 4 (worst), maximum plaque area > median and collateral vessel number <6. Functional measures were performed at baseline and annually for 2 years. Analyses adjust for age, sex, race, comorbidities, and other confounders. Annual changes in usual-paced walking velocity were: Group 1, +0.01 m/s; Group 2, -0.02 m/s; Group 3, -0.01 m/s; Group 4, -0.05 m/s (p-trend=0.008). Group 4 had greater decline than Group 1 (p<0.001), Group 2 (p=0.029), and Group 3 (p=0.010). Similar trends were observed for fastest-paced 4-meter walking velocity (p-trend=0.018). Results were not substantially changed when analyses were repeated with additional adjustment for ABI. However, there were no associations of SFA plaque burden and collateral vessel number with decline in 6-minute walk. In summary, a larger SFA plaque burden combined with fewer collateral vessels is associated with a faster decline in usual and fastest-paced walking velocity in PAD.

Coronary microvascular dysfunction in women: an overview of diagnostic strategies

Coronary microvascular dysfunction (CMD) also known as syndrome X, is characterized by typical anginal symptoms, evidence of myocardial ischemia on non-invasive testing and normal to minimal coronary disease on coronary angiography. It has a female preponderance and has been detected in up to 50% of women presenting with chest pain symptoms. Definitive diagnosis of CMD is critical as recent evidence suggests that women with this condition are at increased risk of cardiovascular events in the future. Invasive coronary reactivity testing on coronary angiography is considered to be the 'gold standard' for diagnosis of CMD. Non-invasive imaging techniques such as PET and cardiac magnetic resonance hold promise for detection of CMD in the future.

Molecular imaging of the cardiac extracellular matrix

In almost all cardiac diseases, an increase in extracellular matrix (ECM) deposition or fibrosis occurs, mostly consisting of collagen I. Whereas replacement fibrosis follows cardiomyocyte loss in myocardial infarction, reactive fibrosis is triggered by myocardial stress or inflammatory mediators and often results in ventricular stiffening, functional deterioration, and development of heart failure. Given the importance of ECM deposition in cardiac disease, ECM imaging could be a valuable clinical tool. Molecular imaging of ECM may help understand pathology, evaluate impact of novel therapy, and may eventually find a role in predicting the extent of ECM expansion and development of personalized treatment. In the current review, we provide an overview of ECM imaging including the assessment of ECM volume and molecular targeting of key players involved in ECM deposition and degradation. The targets comprise myofibroblasts, intracardiac renin-angiotensin axis, matrix metalloproteinases, and matricellular proteins.

Adenosine stress cardiovascular magnetic resonance with variable-density spiral pulse sequences accurately detects coronary artery disease: initial clinical evaluation

BACKGROUND

Adenosine stress cardiovascular magnetic resonance perfusion imaging can be limited by motion-induced dark-rim artifacts, which may be mistaken for true perfusion abnormalities. A high-resolution variable-density spiral pulse sequence with a novel density compensation strategy has been shown to reduce dark-rim artifacts in first-pass perfusion imaging. We aimed to assess the clinical performance of adenosine stress cardiovascular magnetic resonance using this new perfusion sequence to detect obstructive coronary artery disease.

METHODS AND RESULTS

Cardiovascular magnetic resonance perfusion imaging was performed during adenosine stress (140 μg/kg per minute) and at rest on a Siemens 1.5-T Avanto scanner in 41 subjects with chest pain scheduled for coronary angiography. Perfusion images were acquired during injection of 0.1 mmol/kg Gadolinium-diethylenetriaminepentacetate at 3 short-axis locations using a saturation recovery interleaved variable-density spiral pulse sequence. Significant stenosis was defined as >50% by quantitative coronary angiography. Two blinded reviewers evaluated the perfusion images for the presence of adenosine-induced perfusion abnormalities and assessed image quality using a 5-point scale (1 [poor] to 5 [excellent]). The prevalence of obstructive coronary artery disease by quantitative coronary angiography was 68%. The average sensitivity, specificity, and accuracy were 89%, 85%, and 88%, respectively, with a positive predictive value and negative predictive value of 93% and 79%, respectively. The average image quality score was 4.4±0.7, with only 1 study with more than mild dark-rim artifacts. There was good inter-reader reliability with a κ statistic of 0.67.

CONCLUSIONS

Spiral adenosine stress cardiovascular magnetic resonance results in high diagnostic accuracy for the detection of obstructive coronary artery disease with excellent image quality and minimal dark-rim artifacts.

Noncontrast peripheral MRA with spiral echo train imaging

PURPOSE

To develop a spin echo train sequence with spiral readout gradients with improved artery-vein contrast for noncontrast angiography.

THEORY

Venous T2 becomes shorter as the echo spacing is increased in echo train sequences, improving contrast. Spiral acquisitions, due to their data collection efficiency, facilitate long echo spacings without increasing scan times.

METHODS

Bloch equation simulations were performed to determine optimal sequence parameters, and the sequence was applied in five volunteers. In two volunteers, the sequence was performed with a range of echo times and echo spacings to compare with the theoretical contrast behavior. A Cartesian version of the sequence was used to compare contrast appearance with the spiral sequence. Additionally, spiral parallel imaging was optionally used to improve image resolution.

RESULTS

In vivo, artery-vein contrast properties followed the general shape predicted by simulations, and good results were obtained in all stations. Compared with a Cartesian implementation, the spiral sequence had superior artery-vein contrast, better spatial resolution (1.2 mm(2) versus 1.5 mm(2) ), and was acquired in less time (1.4 min versus 7.5 min).

CONCLUSION

The spiral spin echo train sequence can be used for flow-independent angiography to generate three-dimensional angiograms of the periphery quickly and without the use of contrast agents.

Advances in parametric mapping with CMR imaging

Cardiac magnetic resonance imaging (CMR) is well established and considered the gold standard for assessing myocardial volumes and function, and for quantifying myocardial fibrosis in both ischemic and nonischemic heart disease. Recent developments in CMR imaging techniques are enabling clinically-feasible rapid parametric mapping of myocardial perfusion and magnetic relaxation properties (T1, T2, and T2* relaxation times) that are further expanding the range of unique tissue parameters that can be assessed using CMR. To generate a parametric map of perfusion or relaxation times, multiple images of the same region of the myocardium are acquired with different sensitivity to the parameter of interest, and the signal intensities of these images are fit to a model which describes the underlying physiology or relaxation parameters. The parametric map is an image of the fitted perfusion parameters or relaxation times. Parametric mapping requires acquisition of multiple images typically within a breath-hold and thus requires specialized rapid acquisition techniques. Quantitative perfusion imaging techniques can more accurately determine the extent of myocardial ischemia in coronary artery disease and provide the opportunity to evaluate microvascular disease with CMR. T1 mapping techniques performed both with and without contrast are enabling quantification of diffuse myocardial fibrosis and myocardial infiltration. Myocardial edema and inflammation can be evaluated using T2 mapping techniques. T2* mapping provides an assessment of myocardial iron-overload and myocardial hemorrhage. There is a growing body of evidence for the clinical utility of quantitative assessment of perfusion and relaxation times, although current techniques still have some important limitations. This article will review the current imaging technologies for parametric mapping, emerging applications, current limitations, and potential of CMR parametric mapping of the myocardium. The specific focus will be the assessment and quantification of myocardial perfusion and magnetic relaxation times.

Impact of mechanical activation, scar, and electrical timing on cardiac resynchronization therapy response and clinical outcomes

OBJECTIVES

Using cardiac magnetic resonance (CMR), we sought to evaluate the relative influences of mechanical, electrical, and scar properties at the left ventricular lead position (LVLP) on cardiac resynchronization therapy (CRT) response and clinical events.

BACKGROUND

CMR cine displacement encoding with stimulated echoes (DENSE) provides high-quality strain for overall dyssynchrony (circumferential uniformity ratio estimate [CURE] 0 to 1) and timing of onset of circumferential contraction at the LVLP. CMR DENSE, late gadolinium enhancement, and electrical timing together could improve upon other imaging modalities for evaluating the optimal LVLP.

METHODS

Patients had complete CMR studies and echocardiography before CRT. CRT response was defined as a 15% reduction in left ventricular end-systolic volume. Electrical activation was assessed as the time from QRS onset to LVLP electrogram (QLV). Patients were then followed for clinical events.

RESULTS

In 75 patients, multivariable logistic modeling accurately identified the 40 patients (53%) with CRT response (area under the curve: 0.95 [p < 0.0001]) based on CURE (odds ratio [OR]: 2.59/0.1 decrease), delayed circumferential contraction onset at LVLP (OR: 6.55), absent LVLP scar (OR: 14.9), and QLV (OR: 1.31/10 ms increase). The 33% of patients with CURE <0.70, absence of LVLP scar, and delayed LVLP contraction onset had a 100% response rate, whereas those with CURE ≥0.70 had a 0% CRT response rate and a 12-fold increased risk of death; the remaining patients had a mixed response profile.

CONCLUSIONS

Mechanical, electrical, and scar properties at the LVLP together with CMR mechanical dyssynchrony are strongly associated with echocardiographic CRT response and clinical events after CRT. Modeling these findings holds promise for improving CRT outcomes.