Extracellular Volume Imaging Research Articles

Half-Dose versus Single-Dose Gadobutrol for Extracellular Volume Measurements in Cardiac Magnetic Resonance.

Cardiac magnetic resonance (CMR) imaging with gadolinium-based contrast agents offers unique non-invasive insights into cardiac tissue composition. Myocardial extracellular volume (ECV) has evolved as an objective and robust parameter with broad diagnostic and prognostic implications. For the gadolinium compound gadobutrol, the recommended dose for cardiac imaging, including ECV measurements, is 0.1 mmol/kg (single dose). This dose was optimized for late enhancement imaging, a measure of focal fibrosis. Whether a lower dose is sufficient for ECV measurements is unknown. We aim to evaluate the accuracy of ECV measurements using a half dose of 0.05 mmol/kg gadobutrol compared to the standard single dose of 0.1 mmol/kg. From a contemporary trial (NCT04747366, registered 10 February 2021), a total of 25 examinations with available T1 mapping before and after 0.05 and 0.1 mmol/kg gadobutrol were analyzed. ECV values were calculated automatically from pre- and post-contrast T1 relaxation times. T1 and ECV Measurements were performed in the midventricular septum. ECV values after 0.05 and 0.1 mmol/kg gadobutrol were correlated (R2 = 0.920, p < 0.001). ECV values after 0.05 mmol/kg had a bias of +0.9% (95%-CI [0.4; 1.4], p = 0.002) compared to 0.1 mmol/kg gadobutrol, with limits of agreement from -1.5 to 3.3%. CMR with a half dose of 0.05 mmol/kg gadobutrol overestimated ECV by 0.9% compared with a full dose of 0.1 mmol/kg, necessitating adjustment of normal values when using half-dose ECV imaging.

Abstract 15635: Myocardial Function Index Predicts Mortality in Amyloid Light Chain Cardiomyopathy

Introduction: Cardiovascular disease remains the leading cause of morbidity and mortality in patients with amyloid light chain (AL) amyloidosis. Current prognostic evaluation in AL cardiomyopathy (AL-CM) largely relies upon disparate proxy measurements to assess mortality. With respect to observed myocardial volume changes between systole and diastole, we describe a single measurement derived from cardiac MRI (CMR) to assess mortality of AL-CM. Methods: A cohort of 129 consecutive patients with AL-CM undergoing CMR with amyloid protocol from the years 2001 - 1997 was reviewed. Myocardial volume change at end systole and end diastole was assessed by disc summation with CMR. The myocardial function index (MFI) was calculated by consolidating blood pool and myocardial volume measures as confluent components of myocardial function utilizing operator tracings. The association of MFI and death was assessed with adjusted hazard ratios (HR) derived by a Cox model. Results: Data at time of CMR was reviewed. The mean age was 60 ±10; 68% subjects were female. Median survival from CMR was 47 months. Mean LVEF was assessed by echocardiography to be 55% ± 12. Mean calculated MFI was 19.8% ±7. Univariate analysis suggested MFI is strongly associated with death (HR 0.004; 95%CI 0.00002-0.0838; p = 0.0003). A multivariate analysis re-demonstrated the strong predictive value of MFI when controlled for age (HR 0.006; 95%CI 0.00003 - 0.1156; p = 0.0006). Conclusion: MFI strongly correlates with mortality in AL-CM. In contrast to previously described assessments of ventricular function (extracellular volume imaging, myocardial perfusion imaging, and myocardial contraction fraction), MFI is easily derived from CMR and considers blood pool and myocardial volumes as confluent components of myocardial function. Further studies are needed to assess MFI amongst patients with varying etiologies of heart failure.

Quantitative assessment of disease severity of primary sclerosing cholangitis with T1 mapping and extracellular volume imaging.

Assess the relationship between liver T1 relaxation time and extracellular volume (ECV) fraction and the disease severity of primary sclerosing cholangitis (PSC). This retrospective study included 93 patients with PSC and 66 healthy patients in the control group. T1 relaxation times were measured in the right and left lobe, as well as in the area of stricture. T1PSC and ECVPSC were calculated by averaging T1 and ECV of both lobes and stricture site. T1 and ECV were compared between the two groups and according to PSC phenotypes and severity based on Mayo Risk Score (MRS). We also examined the relationship between T1 and ECV with non-invasive measures of fibrosis such as Fibrosis-4 index (FIB-4) and liver stiffness measurement (LSM) by transient elastography. Mean liver T1 (774 ± 111ms, p < 0.001) and liver ECV (0.40 ± 0.14, p < 0.05) were significantly higher with both large-duct and small-duct-type PSC which may lack classic imaging findings on MRCP compared to the control group (p < 0.001). T1PSC and ECVPSC showed weak-moderate correlation with LSM, FIB-4, and MRS (p < 0.05). Cut-off values of liver T1 to detect patients in low-risk and high-risk MRS groups were 677ms (AUC: 0.68, sensitivity: 76%, specificity: 53%, p = 0.03) and 743ms (AUC: 0.83, sensitivity: 79%, specificity: 76%, p < 0.001), respectively. T1 relaxation time and ECV fraction can be used for quantitative assessment of disease severity in patients with PSC.

Systolic-to-diastolic myocardial volume ratio as a novel imaging marker of cardiomyopathy

BackgroundIn patients with normal left ventricular ejection fraction, it may be difficult to distinguish between the normal and diseased heart. Novel assessments of ventricular function, such as extracellular volume imaging, myocardial perfusion imaging and myocardial contraction fraction are emerging to better assess disease burden in these cases. This study endeavored to determine whether the ratio of myocardial volume in systole to myocardial volume in diastole (MVs/MVd), differs between normal hearts and those with disease states characterized by normal ejection fraction. MethodConsecutive patients from 2008 to 2018 with hypertrophic cardiomyopathy (HCM), cardiac amyloidosis, and heart failure with preserved ejection fraction (HFpEF) who underwent cardiac magnetic resonance imaging (MRI) were selected for inclusion, along with a sex- and age-matched cohort of normal volunteers who also underwent cardiac MRI. Manual tracings were performed on each MRI to calculate MVs/MVd, which was then compared across subgroups. ResultsIncluded were 50 patients with HCM, 50 patients with cardiac amyloidosis, 26 patients with HFpEF, and 30 normal subjects. Age was 54.1 years (SD 16.7); mean MVs/MVd was 0.88 (SD 0.04) in the normal subgroup, 1.03 (SD 0.06) in HCM patients, 1.03 (SD 0.06) in cardiac amyloidosis patients, and 0.97 (SD 0.02) in HFpEF patients, with all pathology subgroups different from the normal subgroup (p < .0001 for each). The ratio of MVs/MVd discriminated diseased from normal with c statistic 0.989 (p < .001). ConclusionsThis study suggests that a novel and easily-captured metric of ventricular function, MVs/MVd, can differentiate normal ventricular function from multiple cardiomyopathies with normal ejection fractions.

Acute impact of an endurance race on cardiac function and biomarkers of myocardial injury in triathletes with and without myocardial fibrosis.

AimsThe aim of this study was to investigate the occurrence of myocardial injury and cardiac dysfunction after an endurance race by biomarkers and cardiac magnetic resonance in triathletes with and without myocardial fibrosis.Methods and resultsThirty asymptomatic male triathletes (45 ± 10 years) with over 10 training hours per week and 55 ± 8 ml/kg per minute maximal oxygen uptake during exercise testing were studied before (baseline) and 2.4 ± 1.1 hours post-race. Baseline cardiac magnetic resonance included cine, T1/T2, late gadolinium enhancement (LGE) and extracellular volume imaging. Post-race non-contrast cardiac magnetic resonance included cine and T1/T2 mapping. Non-ischaemic myocardial fibrosis was present in 10 triathletes (LGE+) whereas 20 had no fibrosis (LGE–). At baseline, LGE + triathletes had higher peak exercise systolic blood pressure with 222 ± 21 mmHg compared to LGE– triathletes (192 ± 30 mmHg, P < 0.01). Post-race troponin T and creatine kinase MB were similarly increased in both groups, but there was no change in T2 and T1 from baseline to post-race with 54 ± 3 ms versus 53 ± 3 ms (P = 0.797) and 989 ± 21 ms versus 989 ± 28 ms (P = 0.926), respectively. However, post-race left atrial ejection fraction was significantly lower in LGE + triathletes compared to LGE– triathletes (53 ± 6% vs. 59 ± 6%, P < 0.05). Furthermore, baseline atrial peak filling rates were lower in LGE – triathletes (121 ± 30 ml/s/m2) compared to LGE + triathletes (161 ± 34 ml/s/m2, P < 0.01). Post-race atrial peak filling rates increased in LGE– triathletes to 163 ± 46 ml/s/m2, P < 0.001), but not in LGE + triathletes (169 ± 50ml/s/m2, P = 0.747).ConclusionDespite post-race troponin T release, we did not find detectable myocardial oedema by cardiac magnetic resonance. However, the unfavourable blood pressure response during exercise testing seemed to be associated with post-race cardiac dysfunction, which could explain the occurrence of myocardial fibrosis in triathletes.

Study on diagnostic value of extracellular volume imaging by magnetic resonance imaging for liver fibrosis of hepatitis B

Objective: To investigate the diagnostic value of extracellular volume (ECV) imaging by magnetic resonance imaging for liver fibrosis of hepatitis B. Methods: A retrospective analysis was recruited in patients with chronic hepatitis B, who underwent liver surgery from April to October 2017 for pathological evaluation of liver tissues, and all patients underwent Gd-EOB-DTPA-enhanced T1 mapping to calculate the liver ECV score. The correlation between ECV and staging of hepatic fibrosis and inflammatory activity were compared to clarify the diagnostic value of staging of fibrosis. Results: 66 patients were enrolled in this study. Concerning the staging of liver fibrosis, there were 13, 4, 13, 10, and 26 cases with F0, F1, F2, F3 and F4 stages, respectively. ECV values had high interobserver consistency (correlation coefficient 0.860). The ECV difference between different stages of liver fibrosis was statistically significant (F = 15.02, P < 0.001). There was a significant positive correlation between ECV and fibrosis stage (r = 0.622, P < 0.001), and weak correlation with inflammatory activity (r = 0.332, P = 0.007). Fibrosis staging was an independent factor influencing ECV (P < 0.001). The area under the receiver operator characteristic curve for the diagnosis of liver fibrosis staging F≥1, F≥3 and F4 were 0.760, 0.846 and 0.873, respectively. The diagnostic sensitivity and specificity were 64.15%, 92.31%, 77.78%, 80.00% and 88.46, 72.50%, respectively. Conclusion: MRI-ECV imaging has great value for staging hepatic fibrosis of hepatitis B, and it can provide an effective method for diagnosis, staging, and evaluating the curative effect of fibrosis.

Asymptomatic Cocaine Abuse - Myocardial Tissue Characterization Using Cardiac Biomarkers and Cardiovascular Magnetic Resonance Imaging.

Use of cocaine is widespread and associated with several cardiovascular diseases. Recent CMR studies indicate frequent myocardial scar/fibrosis in asymptomatic cocaine abusers (CA).Methods and Results:This study used a combination of advanced CMR tissue characterization techniques, including late gadolinium enhancement (LGE) for focal, and extracellular volume (ECV) imaging for diffuse myocardial injury/fibrosis, with circulating biomarkers for a comprehensive characterization of myocardial injury. We included 20 cardiac asymptomatic CA and a control group of 20 healthy volunteers. The comprehensive assessment included physical examination, resting ECG, exercise ECG, cardiac biomarkers, transthoracic echocardiogram and CMR. We did not find significant differences between CA and controls either in functional CMR parameters such as LVEDVi, LVESVi, LVEF, LV mass index, or in global myocardial ECV. Neither CA nor controls had evidence of myocardial edema on T2-weighted CMR, but 8 CA (40%), and none of the controls had focal myocardial scar (P<0.01). Interestingly, CA with focal myocardial scar on LGE had significantly higher high-sensitivity troponin I (hs-TNI) compared with CA without focal scar (median, 1.7 ng/L; IQR, 1.3-2.5 ng/L vs. 0.6 ng/L; 0.4-1.3 ng/L; P<0.01). Focal myocardial injury in terms of subtle LGE in 40% of asymptomatic CA was associated with higher hs-TNI. Comprehensive assessment including advanced ECV imaging indicates a focal rather than diffuse pattern of myocardial involvement in asymptomatic CA.

Abstract 14921: Right Ventricular Extracellular Volume Fraction by Magnetic Resonance T1 Mapping in Pulmonary Hypertension and Heart Failure

Introduction: Current cardiac magnetic resonance (CMR) T1 mapping techniques such as Modified Look-Locker inversion recovery (MOLLI) imaging have limited resolution, but the Accelerated and Navigator-Gated Look-Locker Imaging for Cardiac T1 Estimation (ANGIE) is a novel CMR sequence with spatial resolution suitable for T1 mapping of the thin-walled RV. Hypothesis: In pulmonary hypertension (PH) and heart failure (HF), RV extracellular volume (ECV) fraction (as a surrogate measure for RV fibrosis) is a unique parameter describing RV structure that tends to increase with increasing RV size and declining RV function. Methods: Patients with either World Health Organization group 1 or group 4 pulmonary hypertension (PH) or heart failure with reduced ejection fraction (HFrEF) were recruited to undergo contrast-enhanced CMR. RV and LV ECV fractions were determined using pre-contrast and post-contrast T1 mapping using ANGIE (RV and LV) and MOLLI (LV). Results: 22 patients (41% female, median age 61 years old, IQR 51-70 years old) were enrolled, including n=12 with PH and n=10 with HFrEF. ANGIE ECV imaging was of high quality (Figure). A multivariable linear model with RVEF and RVEDVI as independent variables and RVECV as the outcome variable showed independent associations for RVEF and RVEDVI with RVECV (R 2 =0.553) (Table), consistent with a complex relationship involving RV function, dilation, and fibrosis. Conclusions: Pre- and post-contrast ANGIE imaging provides high-resolution ECV determination for the thin-walled RV. RV fibrosis increases with increasing RV size and decreasing overall RV function. Further studies of RVECV in PH and HFrEF are indicated.

Diffuse Myocardial Fibrosis and Inflammation in Rheumatoid Arthritis: Insights From CMR T1 Mapping

ObjectivesThe goal of this study was to assess the diffuse myocardial fibrosis and edema in rheumatoid arthritis (RA) using multiparametric cardiac magnetic resonance (CMR) and the association of myocardial T1 and extracellular volume (ECV) with disease activity, duration, and cardiac function. BackgroundRA is a connective tissue disorder, with frequent cardiovascular disease. Myocardial inflammation and diffuse fibrosis can be detected noninvasively by using native T1 mapping and ECV quantification on CMR. MethodsThirty-nine RA patients (28 women; mean age 50 ± 12 years) and 39 matched control subjects (28 women; mean age 49 ± 12 years) underwent CMR at 1.5-T, including cine, tagging, T2-weighted, native T1 mapping (shortened modified Look-Locker inversion recovery), late gadolinium enhancement (LGE), and ECV imaging. ResultsFocal fibrosis on LGE was found in 46% of RA patients compared with none of the control subjects. Patients with RA had larger areas of focal myocardial edema (10% vs. 0%), higher native T1 values (973 ± 27 ms vs. 961 ± 18 ms; p = 0.03), larger areas of involvement as detected by native T1 >990 ms (35% vs. 2%; p < 0.001), and expansion of ECV (30.3 ± 3.4% vs. 27.9 ± 2.0%; p < 0.001) compared with control subjects. Left ventricular volumes, mass, and ejection fraction were similar between RA patients and control subjects. Peak systolic circumferential strain (–16.9 ± 1.3 vs. –18.7 ± 1.2; p < 0.001) and peak diastolic circumferential strain rate (83 ± 21 s–1 vs. 112 ± 20 s–1; p < 0.001) were impaired in RA patients. Myocardial T1 and ECV were correlated with myocardial strain and RA disease activity. ConclusionsSubclinical cardiovascular disease is frequent in RA, including focal and diffuse myocardial fibrosis and inflammation, which are associated with impaired strain and RA disease activity. CMR T1 mapping provides potential added value as a biomarker for disease monitoring and study of therapies aimed at reducing diffuse myocardial fibrosis in RA.

Ability of extracellular volume imaging to serially measure infarct size compared to LGE within six months after acute myocardial infarction

Background T1 mapping and extracellular volume (ECV) imaging are promising tools to quantify increased extracellular distribution volume of contrast media after myocardial damage. We evaluated the ability of ECV imaging to measure infarct size compared to late gadolinium enhancement (LGE) after acute myocardial infarction (AMI). Additionally, the amount of cellular damage was serially measured by ECV imaging.

Comparison of short and long axis T1 and ECV maps in patients with myocarditis

Background T1 mapping and ECV imaging are promising diagnostic tools in patients with suspected myocarditis. However, there are currently no data on the potential influence of slice orientation on the derived T1 and ECV values. Thus, we compared global myocardial T1 and ECV values between slices with short and long axis orientation. Methods This study included 50 patients with clinically suspected myocarditis, who underwent CMR at 1.5 Tesla. T1 quantification was performed on three short (basis, center, apex) and on three long axis slices (2-, 3- and 4-chamber orientation), respectively. The modified Look-Locker inversionrecovery (MOLLI) sequence was used before and 15 minutes after administration of 0.075 mmol/kg GadoliniumBOPTA. Native T1, post-contrast T1 and extracellular volume (ECV) maps were calculated using a dedicated plug-in written for the OsiriX software. Mean native and post-contrast T1 as well as ECV were obtained from the three short and long axes, respectively. Results There were significantly lower median native myocardial T1 values on long axis slices (1079 (1040-1130.0)) compared to short axis slices (1103 (1069-1140); p=0.0026). However, there were no significant differences in postcontrast myocardial T1 values (median 554 (505-596) vs. 555 (509-601); p=0.2299) or ECV (median 30 (27-33) vs. 29 (26-33); p=0.6063) between short and long axis slices, respectively. Conclusions Slice orientation could be a potential confounding factor for the assessment of native global myocardial T1 values in myocarditis. Possible explanations for this finding include technical issues, such as variations in throughplane motion or partial-volume effects related to slice orientation, but also the heterogeneity of myocardial injury in myocarditis. However, our data indicate that global myocardial ECV values could be less sensitive to slice orientation.

CMR in Patients With Severe Myocarditis: Diagnostic Value of Quantitative Tissue Markers Including Extracellular Volume Imaging

ObjectivesThis study evaluated the accuracy of T2, T1, and extracellular volume (ECV) quantification as novel quantitative tissue markers in comparison with standard “Lake-Louise” cardiac magnetic resonance (CMR) criteria to diagnose myocarditis. BackgroundNovel approaches using T2 and T1 mapping may overcome the limitations of signal intensity-based parameters, which would potentially result in a better diagnostic accuracy compared with standard CMR techniques in suspected myocarditis. MethodsCMR was performed in 104 patients with myocarditis and 21 control subjects at 1.5-T. Patients with myocarditis underwent CMR 2 weeks (interquartile range: 1 to 7 weeks) after presentation with new-onset heart failure (n = 66) or acute chest pain (n = 38). T2 and T1 mapping were implemented into a standard protocol including T2-weighted (T2w), early gadolinium enhancement (EGE) CMR, and late gadolinium enhancement (LGE) CMR. T2 quantification was performed using a free-breathing, navigator-gated multiecho sequence. T1 quantification was performed using the modified Look-Locker inversion recovery sequence before and after administration of 0.075 mmol/kg gadobenate dimeglumine. T2, T1, and ECV maps were generated using a plug-in for the OsiriX software (Pixmeo, Bernex, Switzerland) to calculate mean global myocardial T2, T1, and ECV values. ResultsThe diagnostic accuracies of conventional CMR were 70% (95% confidence interval [CI]: 61% to 77%) for T2w CMR, 59% (95% CI: 56% to 73%) for EGE, and 67% (95% CI: 59% to 75%) for LGE. The diagnostic accuracies of mapping techniques were 63% (95% CI: 53% to 73%) for myocardial T2, 69% (95% CI: 60% to 76%) for native myocardial T1, and 76% (95% CI: 68% to 82%) for global myocardial ECV. The diagnostic accuracy of CMR was significantly improved to 90% (95% CI: 84% to 95%) by a stepwise approach, using the presence of LGE and myocardial ECV ≥27% as diagnostic criteria, compared with 79% (95% CI: 71% to 85%; p = 0.0043) for the Lake-Louise criteria. ConclusionsIn patients with clinical evidence for subacute, severe myocarditis, ECV quantification with LGE imaging significantly improved the diagnostic accuracy of CMR compared with standard Lake-Louise criteria.

Predicting mortality in patients with non-ischemic dilative cardiomyopathy: Potential of extracellular volume imaging by cardiovascular magnetic resonance

Background Predicting mortality in patients with non-ischemic dilated cardiomyopathy (NIDCM) is currently demanding and requires complex models. Assessing the extracellular volume fraction (ECV) by T1-mapping cardiovascular magnetic resonance (CMR) is an attractive approach to quantify myocardial injury as a potential predictor of adverse events in these patients. This study evaluated ECV imaging by T1-mapping CMR in comparison with the established “Seattle Heart Failure Model” (SHFM; http://www.seattleheartfailuremodel.org). Methods This study included 50 patients with heart failure and reduced left ventricular (LV) ejection fraction due to non-ischemic cardiomyopathy. The SHFM was used to estimate 1, 2 and 5 year mortalities as well as life expectancy, respectively. T1 quantification was performed at 1.5 Tesla using the modified Look-Locker inversionrecovery (MOLLI) sequence on 3 short-axes before and 15 minutes after administration of 0.075 mmol/kg gadolinium-BOPTA. Global myocardial ECV was then calculated from native and post-contrast T1 maps generated by a dedicated plug-in written for the OsiriX software, respectively. Results Median predicted 1-, 2- and 5-year mortalities were 4% (interquartile range 2-6%), 7% (interquartile range 5-12%) and 16% (interquartile range 12-28%) in the study population, respectively. Median estimated life expectancy was 13 years (interquartile range 9-15 years). A significant correlation was found between global myocardial ECV and predicted 1- (r = 0.47; p < 0.001), 2- (r = 0.46; p < 0.001) and 5-year mortality (r = 0.46; p < 0.001), respectively. Furthermore, a significant inverse correlation was found between global myocardial ECV and predicted life expectancy (r = -0.37; p < 0.01). Conclusions Myocardial injury as quantified by ECV-imaging correlates well with predicted mortality and has great potential to improve risk stratification in patients with heart failure due to NIDCM. Funding

Extracellular volume imaging by T1 mapping cardiovascular magnetic resonance in patients with clinically suspected myocarditis

Background Assessing the extracellular volume fraction (ECV) by T1 mapping is a promising cardiovascular magnetic resonance (CMR) approach to quantify myocardial injury. This study evaluated ECV imaging by T1 mapping CMR in patients with clinically suspected myocarditis. Methods T1 mapping was implemented into a standard CMR protocol in 113 patients with clinically suspected myocarditis at 1.5 Tesla. T1 quantification was performed for ECV -calculation using the modified Look-Locker inversionrecovery (MOLLI) sequence on three short-axes before and 15 minutes after administration of 0.075 mmol/kg gadolinium BOPTA, respectively. Global left ventricular ECV was calculated from T1 maps generated with a dedicated plug-in written for the OsiriX software: relaxation rates (1/T1 = R1) were calculated for myocardium and blood pool. The difference in R1 between pre- and post contrast media was calculated as ΔR1. Myocardial ECV was then estimated using the formula: ECV = 1-hematocrit * (ΔR1myocardium/ΔR1blood pool). Figure 1 demonstrates an example for T1 maps pre- and post contrast media in comparison with standard black-blood T2 STIR and late gadolinium enhancement (LGE) images. Results The final study population consisted of 96 patients after exclusion of 17 patients with concomitant coronary artery disease or severe left ventricular hypertrophy. Current clinical and CMR criteria identified 64 (67 %) patients with myocarditis and 32 (33 %) patients without myocarditis in the final study population. Global ECV was significantly larger in patients with myocarditis compared to patients without myocarditis (35±6 vs. 30±5 %, p<0.0001). Furthermore, global ECV was significantly larger in patients with focal scar compared to patients without focal scar on LGE CMR (35±5 vs. 33±7 %, p<0.05). ROC analysis revealed a sensitivity of 73 % and a specificity 67 % to identify patients with myocarditis using a global ECV ≧ 32 % cutoff (AUC = 0.76, p<0.0001). Conclusions Patients with myocarditis are characterized by an increased global ECV. Assessing global ECV by T1 mapping has great potential to improve the diagnostic and prognostic impact of CMR in patients with clinically suspected myocarditis.

Extracellular volume MRI increases the detection of myocardial abnormalities beyond late gadolinium enhancement - initial findings

Background Late gadolinium enhancement (LGE) is excellent for identifying focal lesions in the myocardium (necrosis, fibrosis), but diffuse homogeneous abnormalities are not readily detectable. Quantitative measurement of the myocardial extracellular volume (ECV) fraction using MRI has recently been validated histologically, and implemented for parametric imaging in patients. We hypothesized that quantification of ECV using ECV imaging could detect focal lesions detected by LGE, and diffuse homogenous disturbances in the myocardial extracellular volume fraction which are not detectable by LGE. The objective of the study was to examine the diagnostic utility of ECV MRI for detecting myocardial tissue abnormalities compared to LGE. Methods

Extracellular volume imaging by magnetic resonance imaging provides insights into overt and sub-clinical myocardial pathology

Conventional late gadolinium enhancement (LGE) cardiac magnetic resonance can detect myocardial infarction and some forms of non-ischaemic myocardial fibrosis. However, quantitative imaging of extracellular volume fraction (ECV) may be able to detect subtle abnormalities such as diffuse fibrosis or post-infarct remodelling of remote myocardium. The aims were (1) to measure ECV in myocardial infarction and non-ischaemic myocardial fibrosis, (2) to determine whether ECV varies with age, and (3) to detect sub-clinical abnormalities in 'normal appearing' myocardium remote from regions of infarction. Cardiac magnetic resonance ECV imaging was performed in 126 patients with T1 mapping before and after injection of gadolinium contrast. Conventional LGE images were acquired for the left ventricle. In patients with a prior myocardial infarction, the infarct region had an ECV of 51 ± 8% which did not overlap with the remote 'normal appearing' myocardium that had an ECV of 27 ± 3% (P < 0.001, n = 36). In patients with non-ischaemic cardiomyopathy, the ECV of atypical LGE was 37 ± 6%, whereas the 'normal appearing' myocardium had an ECV of 26 ± 3% (P < 0.001, n = 30). The ECV of 'normal appearing' myocardium increased with age (r = 0.28, P = 0.01, n = 60). The ECV of 'normal appearing' myocardium remote from myocardial infarctions increased as left ventricular ejection fraction decreased (r = -0.50, P = 0.02). Extracellular volume fraction imaging can quantitatively characterize myocardial infarction, atypical diffuse fibrosis, and subtle myocardial abnormalities not clinically apparent on LGE images. Taken within the context of prior literature, these subtle ECV abnormalities are consistent with diffuse fibrosis related to age and changes remote from infarction.

Myocardial extracellular volume imaging by CMR quantitatively characterizes myocardial infarction and subclinical myocardial fibrosis

Imaging of fibrosis by cardiovascular magnetic resonance (CMR) is performed using late gadolinium enhancement (LGE). However, LGE imaging only visualizes relative differences between “normal” myocardium and fibrosis or infarction. Recent developments in T1 mapping have made it practical to quantitatively image the extracellular volume fraction (ECV).