Ananth Kidambi

Reference values for healthy human myocardium using a T1 mapping methodology: results from the International T1 Multicenter cardiovascular magnetic resonance study

BackgroundT1 mapping is a robust and highly reproducible application to quantify myocardial relaxation of longitudinal magnetisation. Available T1 mapping methods are presently site and vendor specific, with variable accuracy and precision of T1 values between the systems and sequences. We assessed the transferability of a T1 mapping method and determined the reference values of healthy human myocardium in a multicenter setting.MethodsHealthy subjects (n = 102; mean age 41 years (range 17–83), male, n = 53 (52%)), with no previous medical history, and normotensive low risk subjects (n=113) referred for clinical cardiovascular magnetic resonance (CMR) were examined. Further inclusion criteria for all were absence of regular medication and subsequently normal findings of routine CMR. All subjects underwent T1 mapping using a uniform imaging set-up (modified Look- Locker inversion recovery, MOLLI, using scheme 3(3)3(3)5)) on 1.5 Tesla (T) and 3 T Philips scanners. Native T1-maps were acquired in a single midventricular short axis slice and repeated 20 minutes following gadobutrol. Reference values were obtained for native T1 and gadolinium-based partition coefficients, λ and extracellular volume fraction (ECV) in a core lab using standardized postprocessing.ResultsIn healthy controls, mean native T1 values were 950 ± 21 msec at 1.5 T and 1052 ± 23 at 3 T. λ and ECV values were 0.44 ± 0.06 and 0.25 ± 0.04 at 1.5 T, and 0.44 ± 0.07 and 0.26 ± 0.04 at 3 T, respectively. There were no significant differences between healthy controls and low risk subjects in routine CMR parameters and T1 values. The entire cohort showed no correlation between age, gender and native T1. Cross-center comparisons of mean values showed no significant difference for any of the T1 indices at any field strength. There were considerable regional differences in segmental T1 values. λ and ECV were found to be dose dependent. There was excellent inter- and intraobserver reproducibility for measurement of native septal T1.ConclusionWe show transferability for a unifying T1 mapping methodology in a multicenter setting. We provide reference ranges for T1 values in healthy human myocardium, which can be applied across participating sites.

MR Imaging of Cardiac Tumors and Masses: A Review of Methods and Clinical Applications

Cardiac masses are usually first detected at echocardiography. In their further evaluation, cardiac magnetic resonance (MR) imaging has become a highly valuable technique. MR imaging offers incremental value owing to its larger field of view, superior tissue contrast, versatility in image planes, and unique ability to enable discrimination of different tissue characteristics, such as water and fat content, which give rise to particular signal patterns with T1- and T2-weighted techniques. With contrast material-enhanced MR imaging, additional tissue properties such as vascularity and fibrosis can be demonstrated. MR imaging can therefore contribute to the diagnosis of a cardiac mass as well as be used to detail its relationship to other cardiac and extracardiac structures. These assessments are important to plan therapy, such as surgical intervention. In addition, serial MR studies can be used to monitor tumor regression after surgery or chemotherapy. Primary cardiac tumors are very rare; metastases and pseudotumors (eg, thrombus) are much more common. This article provides an overview of cardiac masses and reviews the optimal MR imaging techniques for their assessment.

Relationship between Myocardial Edema and Regional Myocardial Function after Reperfused Acute Myocardial Infarction: An MR Imaging Study

PURPOSE To compare the relationship of myocardial edema and corresponding contractile function over time in patients with reperfused acute myocardial infarction (AMI). MATERIALS AND METHODS This study was approved by the regional ethics committee; all patients gave written informed consent. Thirty-nine patients (34 men; mean age, 57 years; age range, 35-73 years) underwent T2-weighted, tagging, and late gadolinium enhancement magnetic resonance imaging at three time points after primary percutaneous coronary intervention for ST-elevation AMI. Circumferential strain, T2-weighted signal intensity, and volume of infarct zones, peri-infarct zones, and remote myocardium were measured. Patients were stratified by presence or absence of peri-infarct edema, defined as areas with T2-weighted signal intensity of two or more standard deviations above that of remote myocardium. Statistical analysis was performed with repeated-measures analysis of variance with post hoc Bonferroni correction. RESULTS Edematous peri-infarct myocardium had attenuated strain compared with remote myocardium at day 2 (-0.137 vs -0.226, P < .001), day 30 (-0.188 vs -0.240, P < .01), and day 90 (-0.207 vs -0.241, P = .01). Nonedematous peri-infarct myocardium had similar (P > .05) strain to remote myocardium at all time points. Strain improved in edematous peri-infarct myocardium at day 30 (P = .02) and day 90 (P < .01), closely mirroring resolution of intensity and volume of edema. Decreased strain correlated with edema volume (r = 0.30, P = .01) and normalized edema signal intensity (r = 0.28, P < .01). In eight patients with fully transmural infarction, infarct zone strain improved between day 2 and day 90 (P = .02). CONCLUSION Improvement of strain in peri-infarct myocardium closely follows regression of myocardial edema. Volume of edema and intensity of signal on T2-weighted images relate to functional recovery after reperfused AMI.

Consequence of Cerebral Embolism After Transcatheter Aortic Valve Implantation Compared With Contemporary Surgical Aortic Valve Replacement Effect on Health-Related Quality of Life

Background—Incidence of cerebral microinfarcts is higher after transcatheter aortic valve implantation (TAVI) compared with surgical aortic valve replacement (SAVR). It is unknown whether these lesions persist and what direct impact they have on health-related quality of life. The objective was to identify predictors of cerebral microinfarction and measure their effect on health-related quality of life during 6 months after TAVI when compared with SAVR. Methods and Results—Cerebral MRI was conducted at baseline, post procedure, and 6 months using diffusion-weighted imaging. Health-related quality of life was measured at baseline, 30 days, and 6 months with short form-12 health outcomes and EuroQol 5 dimensions questionnaires. One hundred eleven patients (TAVI, n=71; SAVR, n=40) were studied. The incidence (54 [77%] versus 17 [43%]; P=0.001) and number (3.4±4.9 versus 1.2±1.8; P=0.001) of new microinfarcts were greater after TAVI than after SAVR. The total volume per microinfarct was smaller in TAVI than in SAVR (0.23±0.24 versus 0.76±1.8 mL; P=0.04). The strongest associations for microinfarction were: TAVI (arch atheroma grade: r=0.46; P=0.0001) and SAVR (concomitant coronary artery bypass grafting: r=−0.33; P=0.03). Physical component score in TAVI increased after 30 days (32.1±6.6 versus 38.9±7.0; P<0.0001) and 6 months (40.4±9.3; P<0.0001); the improvement occurred later in SAVR (baseline: 34.9±10.6; 30 days: 35.9±10.2; 6 months: 42.8±11.2; P<0.001). After TAVI, there were no differences in the short form-12 health outcome scores according to the presence or size of new cerebral infarction. Conclusions—Cerebral microinfarctions are more common after TAVI compared with SAVR but seem to have no negative effect on early (30 days) or medium term (6 months) health-related quality of life. Aortic atheroma (TAVI) and concomitant coronary artery bypass grafting (SAVR) are independent risk factors for cerebral microinfarction.

Susceptibility-weighted cardiovascular magnetic resonance in comparison to T2 and T2 star imaging for detection of intramyocardial hemorrhage following acute myocardial infarction at 3 Tesla

BackgroundIntramyocardial hemorrhage (IMH) identified by cardiovascular magnetic resonance (CMR) is an established prognostic marker following acute myocardial infarction (AMI). Detection of IMH by T2-weighted or T2 star CMR can be limited by long breath hold times and sensitivity to artefacts, especially at 3T. We compared the image quality and diagnostic ability of susceptibility-weighted magnetic resonance imaging (SW MRI) with T2-weighted and T2 star CMR to detect IMH at 3T.MethodsForty-nine patients (42 males; mean age 58 years, range 35-76) underwent 3T cardiovascular magnetic resonance (CMR) 2 days following re-perfused AMI. T2-weighted, T2 star and SW MRI images were obtained. Signal and contrast measurements were compared between the three methods and diagnostic accuracy of SW MRI was assessed against T2w images by 2 independent, blinded observers. Image quality was rated on a 4-point scale from 1 (unusable) to 4 (excellent).ResultsOf 49 patients, IMH was detected in 20 (41%) by SW MRI, 21 (43%) by T2-weighted and 17 (34%) by T2 star imaging (p =ns). Compared to T2-weighted imaging, SW MRI had sensitivity of 93% and specificity of 86%. SW MRI had similar inter-observer reliability to T2-weighted imaging (κ =0.90 and κ =0.88 respectively); both had higher reliability than T2 star (κ =0.53). Breath hold times were shorter for SW MRI (4 seconds vs. 16 seconds) with improved image quality rating (3.8 ± 0.4, 3.3 ± 1.0, 2.8 ± 1.1 respectively; p < 0.01).ConclusionsSW MRI is an accurate and reproducible way to detect IMH at 3T. The technique offers considerably shorter breath hold times than T2-weighted and T2 star imaging, and higher image quality scores.

Single bolus versus split dose gadolinium administration in extra-cellular volume calculation at 3 Tesla

BackgroundDiffuse myocardial fibrosis may be quantified with cardiovascular magnetic resonance (CMR) by calculating extra-cellular volume (ECV) from native and post-contrast T1 values. Accurate ECV calculation is dependent upon the contrast agent having reached equilibrium within tissue compartments. Previous studies have used infusion or single bolus injections of contrast to calculate ECV. In clinical practice however, split dose contrast injection is commonly used as part of stress/rest perfusion studies. In this study we sought to assess the effects of split dose versus single bolus contrast administration on ECV calculation.MethodsTen healthy volunteers and five patients ( 4 ischaemic heart disease, 1 hypertrophic cardiomyopathy) were studied on a 3.0 Tesla (Philips Achieva TX) MR system and underwent two (patients) or three (volunteers) separate CMR studies over a mean of 12 and 30 days respectively. Volunteers underwent one single bolus contrast study (Gadovist 0.15mmol/kg). In two further studies, contrast was given in two boluses (0.075mmol/kg per bolus) as part of a clinical adenosine stress/rest perfusion protocol, boluses were separated by 12 minutes. Patients underwent one bolus and one stress perfusion study only. T1 maps were acquired pre contrast and 15 minutes following the single bolus or second contrast injection.ResultsECV agreed between bolus and split dose contrast administration (coefficient of variability 5.04%, bias 0.009, 95% CI −3.754 to 3.772, r2 = 0.973, p = 0.001)). Inter-study agreement with split dose administration was good (coefficient of variability, 5.67%, bias −0.018, 95% CI −4.045 to 4.009, r2 = 0.766, p > 0.001).ConclusionECV quantification using split dose contrast administration is reproducible and agrees well with previously validated methods in healthy volunteers, as well as abnormal and remote myocardium in patients. This suggests that clinical perfusion CMR studies may incorporate assessment of tissue composition by ECV based on T1 mapping.

Myocardial Extracellular Volume Estimation by CMR Predicts Functional Recovery Following Acute MI

Objectives In the setting of reperfused acute myocardial infarction (AMI), the authors sought to compare prediction of contractile recovery by infarct extracellular volume (ECV), as measured by T1-mapping cardiac magnetic resonance (CMR), with late gadolinium enhancement (LGE) transmural extent. Background The transmural extent of myocardial infarction as assessed by LGE CMR is a strong predictor of functional recovery, but accuracy of the technique may be reduced in AMI. ECV mapping by CMR can provide a continuous measure associated with the severity of tissue damage within infarcted myocardium. Methods Thirty-nine patients underwent acute (day 2) and convalescent (3 months) CMR scans following AMI. Cine imaging, tissue tagging, T2-weighted imaging, modified Look-Locker inversion T1 mapping natively and 15 min post–gadolinium-contrast administration, and LGE imaging were performed. The ability of acute infarct ECV and acute transmural extent of LGE to predict convalescent wall motion, ejection fraction (EF), and strain were compared per-segment and per-patient. Results Per-segment, acute ECV and LGE transmural extent were associated with convalescent wall motion score (p < 0.01; p < 0.01, respectively). ECV had higher accuracy than LGE extent to predict improved wall motion (area under receiver-operating characteristics curve 0.77 vs. 0.66; p = 0.02). Infarct ECV ≤0.5 had sensitivity 81% and specificity 65% for prediction of improvement in segmental function; LGE transmural extent ≤0.5 had sensitivity 61% and specificity 71%. Per-patient, ECV and LGE correlated with convalescent wall motion score (r = 0.45; p < 0.01; r = 0.41; p = 0.02, respectively) and convalescent EF (p < 0.01; p = 0.04). ECV and LGE extent were not significantly correlated (r = 0.34; p = 0.07). In multivariable linear regression analysis, acute infarct ECV was independently associated with convalescent infarct strain and EF (p = 0.03; p = 0.04), whereas LGE was not (p = 0.29; p = 0.24). Conclusions Acute infarct ECV in reperfused AMI can complement LGE assessment as an additional predictor of regional and global LV functional recovery that is independent of transmural extent of infarction.

Factors associated with false‐negative cardiovascular magnetic resonance perfusion studies: A Clinical evaluation of magnetic resonance imaging in coronary artery disease (CE‐MARC) substudy

To examine factors associated with false‐negative cardiovascular magnetic resonance (MR) perfusion studies within the large prospective Clinical Evaluation of MR imaging in Coronary artery disease (CE‐MARC) study population. Myocardial perfusion MR has excellent diagnostic accuracy to detect coronary heart disease (CHD). However, causes of false‐negative MR perfusion studies are not well understood.

Advances in cardiovascular magnetic resonance in ischaemic heart disease and non-ischaemic cardiomyopathies

In 2008, Heart published an overview of advances in cardiovascular magnetic resonance (CMR) and their clinical application.1 Since then, the evidence for the use of CMR both as a clinical and cardiovascular research tool has increased further. In 2010, the American College of Cardiology Foundation (ACCF), American Heart Association (AHA), American College of Radiology, and the Society for Cardiovascular Magnetic Resonance (SCMR) produced an expert consensus document that provided an up-to-date perspective on the current state of CMR and its clinical applications.2 Data from the large EuroCMR registry continue to demonstrate the impact of the clinical information gained by CMR on patient management, and more data regarding the prognostic impact of CMR have emerged across a spectrum of cardiovascular diseases.3 w1–4 Reflecting this growing body of evidence, recent European and North American practice guidelines have endorsed the use of CMR in several clinical scenarios, including chest pain and heart failure.4–7 w5 Standardisation of CMR training, protocols and reporting has progressed with several recommendation papers published over the past 5 years reflecting the increasing maturity of this imaging modality.w6–10 Finally, further technical advances and innovations have refined CMR methods and provided novel techniques. This article focuses on advances in CMR in ischaemic heart disease (IHD) and non-ischaemic cardiomyopathies, as well as touching on potential future applications. CMR produces high resolution images which can be acquired in any plane and allow the assessment of global and regional cardiac function, myocardial perfusion, myocardial viability, tissue characterisation, and proximal coronary anatomy. Here we summarise recent clinical evidence for the role of CMR in the assessment of IHD and further technical advances. ### Clinical validation of stress perfusion CMR The use of stress perfusion CMR as a first line diagnostic tool in patients with IHD has been the subject of several recent clinical studies and meta-analyses.8 , …

Reciprocal ECG change in reperfused ST-elevation myocardial infarction is associated with myocardial salvage and area at risk assessed by cardiovascular magnetic resonance

Objective ST-elevation acute myocardial infarction (STEMI) is frequently associated with reciprocal ST depression in contralateral ECG leads. The relevance of these changes is debated. This study examined whether reciprocal ECG changes in STEMI reflect larger myocardial area at risk (AAR) and/or infarct size. Design Patients were stratified by presence of reciprocal change on the presenting ECG, defined as ≥1 mm ST depression in ≥2 inferior leads for anterior STEMI, or ≥2 anterior leads for inferior STEMI. Infarcted tissue was defined on late enhancement and AAR on T2-weighted cardiovascular magnetic resonance (CMR). Setting Patients with reperfused first STEMI underwent CMR within 3 days of presentation. Main outcome measures In addition to AAR and infarct mass, myocardial salvage was calculated as (AAR mass—infarct mass) and salvage index as myocardial salvage/AAR mass. Results Thirty-five patients were analysed (n=35). Patients with reciprocal ECG changes (n=19) had higher AAR mass than those without (42 g vs 29 g, p<0.001), and higher myocardial salvage (27 g vs 9 g, p<0.001) and myocardial salvage index (61% vs 17%, p<0.001) but similar infarct size (16 g vs 20 g, p=0.3) and ejection fraction (43% vs 45%, p=0.5). Conclusions STEMI patients with reciprocal ECG changes have larger AAR, higher myocardial salvage and salvage index than those without. Reciprocal changes appear to be a marker of increased ischaemic myocardium at risk and indicate the potential for increased salvage with emergency revascularisation. Reciprocal changes showed no relationship to infarct size, which may be influenced by ischaemia time and other treatment factors.