Native Myocardial T1 as a Biomarker of Cardiac Structure in Non-Ischemic Cardiomyopathy

Efficacy of Native T1 Mapping for Patients With Non-Ischemic Cardiomyopathy and Ventricular Functional Mitral Regurgitation Undergoing Transcatheter Edge-to-Edge Repair

BACKGROUND

We investigated the efficacy of left ventricular (LV) myocardial damage by native T1mapping obtained with cardiac magnetic resonance (CMR) for patients undergoing transcatheter edge-to-edge repair (TEER).

METHODS AND RESULTS

We studied 40 symptomatic non-ischemic heart failure (HF) patients and ventricular functional mitral regurgitation (VFMR) undergoing TEER. LV myocardial damage was defined as the native T1Z-score, which was converted from native T1values obtained with CMR. The primary endpoint was defined as HF rehospitalization or cardiovascular death over 12 months after TEER. Multivariable Cox proportional hazards analysis showed that the native T1Z-score was the only independent parameter associated with cardiovascular events (hazard ratio 3.40; 95% confidential interval 1.51-7.67), and that patients with native T1Z-scores <2.41 experienced significantly fewer cardiovascular events than those with native T1Z-scores ≥2.41 (P=0.001). Moreover, the combination of a native T1Z-score <2.41 and more severe VFMR (effective regurgitant orifice area [EROA] ≥0.30 cm2) was associated with fewer cardiovascular events than a native T1Z-score ≥2.41 and less severe VFMR (EROA <0.30 cm2; P=0.002).

CONCLUSIONS

Assessment of baseline LV myocardial damage based on native T1Z-scores obtained with CMR without gadolinium-based contrast media is a valuable additional parameter for better management of HF patients and VFMR following TEER.

Additional value of T1 and T2 mapping techniques for early detection of myocardial involvement in scleroderma

BACKGROUND

We evaluated the prevalence of myocardial involvement by native T1 and T2 mapping, the diagnostic performance of mapping in addition to conventional Lake Louise Criteria (LLC), as well as correlations between mapping findings and clinical or conventional cardiovascular magnetic resonance (CMR) parameters in systemic sclerosis (SSc) patients.

METHODS

Fifty-five SSc patients (52.31 ± 13.24 years, 81.8% female) and 55 age- and sex-matched healthy subjects underwent clinical, bio-humoral assessment, and CMR. The imaging protocol included: T2-weighted, early post-contrast cine sequences, native T1 and T2 mapping by a segmental approach, and late gadolinium enhancement (LGE) technique.

RESULTS

Global myocardial T1 and T2 values were significantly higher in SSc patients than in healthy subjects. An increase in native T1 and/or T2 was present in the 62.1% of patients with normal conventional CMR techniques (negative LGE and T2-weighted images). Respectively, 13.5% and 59.6% of patients fulfilled original and updated LLC (overall agreement = 53.9%). Compared with patients with normal native T1, patients with increased T1 (40.0%) featured significantly higher left ventricular end-diastolic volume index and cardiac index, biventricular stroke volume indexes, and global heart T2 values, and more frequently had a history of digital ulcers. Biochemical and functional CMR parameters were comparable between patients with normal and increased T2 (61.8%).

CONCLUSION

T1 and T2 mapping are sensitive parameters that should be included in the routine clinical assessment of SSc patients for detecting early/subclinical myocardial involvement.

Early detection and serial monitoring during chemotherapy-radiation therapy: Using T1 and T2 mapping cardiac magnetic resonance imaging

Purpose

To confirm the ability of native T1 and T2 values in detecting and monitoring early myocardial injuries of chest radiotherapy in neoplasm patients.

Materials and methods

Fifteen participants received non-anthracycline chemotherapy and chest radiotherapy, and 30 age/gender-matched controls were enrolled in this prospective study. Cardiac magnetic resonance scans were performed within 2 days, 3 months, and 6 months after chest radiotherapy. Myocardial native T1 and T2 values were measured in irradiated and nonirradiated areas. Meanwhile, the parameters of left ventricular function and left ventricular myocardial strain were obtained.

Results

There were no significant differences in left ventricular function, native T1, T2, and strain between patients and controls before chest radiotherapy. In 15 participants who were followed up for 6 months, there was a significant change only in left ventricular ejection fraction (LVEF) among baseline and the first follow-up (P = 0.021), while the adjusted P-value was higher than 0.05 after Bonferroni correction, as well as other parameters. Native T1 values were elevated at 3 and 6 months in irradiated areas compared with baseline (1,288.72 ± 66.59 ms vs. 1,212.51 ± 45.41 ms; 1,348.01 ± 54.16 ms vs. 1,212.51 ± 45.41 ms; P &lt; 0.001 for both). However, T2 values only changed at 3 months in irradiated areas compared with baseline (44.21 ± 3.35 ms vs. 39.14 ± 1.44 ms; P = 0.006). Neither the native T1 nor T2 values changed in nonirradiated areas during the follow-up period (all P &gt; 0.05). There were no significant differences in strain changes during the follow-up period (all P &gt; 0.05).

Conclusion

Native T1 and T2 values elevated at 3 months after chest radiotherapy, whereas LVEF showed no significant change during the 6-month follow-up.

T1 Mapping and Extracellular Volume Fraction in Dilated Cardiomyopathy: A Prognosis Study

OBJECTIVES

The aim of this study is to examine the prognostic value of T1 mapping and the extracellular volume (ECV) fraction in patients with dilated cardiomyopathy (DCM).

BACKGROUND

Patients with DCM with functional left ventricular remodeling have poorer prognoses. Noninvasive assessment of myocardial fibrosis using T1 mapping and the ECV fraction may improve risk stratification of patients with DCM; however, this has not yet been systematically evaluated.

METHODS

A total of 659 consecutive patients with DCM (498 men; 45 ± 15 years) who underwent cardiac magnetic resonance with T1 mapping and late gadolinium enhancement (LGE) imaging with a 1.5-T magnetic resonance scanner were enrolled in this study. Primary endpoints were cardiac-related death and heart transplantation. Secondary endpoints were hospitalization for heart failure, ventricular arrhythmias, and implantable cardioverter-defibrillator or cardiac resynchronization therapy implantation. Survival estimates were calculated by Kaplan-Meier curves with the log-rank test.

RESULTS

During a mean follow-up of 66.3 ± 20.9 months, 122 and 205 patients with DCM reached the primary and secondary endpoints, respectively. The presence of LGE had an association with both of the primary and secondary endpoints observed in the patients with DCM (both P < 0.001). The maximum native T1 (HR: 1.04; 95% CI: 1.02-1.09) and maximum ECV fraction (HR: 1.14; 95% CI: 1.08-1.21) had associations with the primary endpoints in the patients with positive LGE (both P < 0.001), whereas the mean native T1 (HR: 1.13; 95% CI: 1.10-1.36) and mean ECV fraction (HR: 1.32; 95% CI: 1.12-1.53) had the best associations in the patients with negative LGE (all P < 0.001).

CONCLUSIONS

T1 mapping and the ECV fraction had prognostic value in patients with DCM and were particularly important in patients with DCM without LGE. Using a combination of T1 mapping, ECV fraction, and LGE provided optimal risk stratification for patients with DCM.

Non-contrast cardiovascular magnetic resonance detection of myocardial fibrosis in Duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) leads to progressive cardiomyopathy. Detection of myocardial fibrosis with late gadolinium enhancement (LGE) by cardiovascular magnetic resonance (CMR) is critical for clinical management. Due to concerns of brain deposition of gadolinium, non-contrast methods for detecting and monitoring myocardial fibrosis would be beneficial.

OBJECTIVES

We hypothesized that native T1 mapping and/or circumferential (εcc) and longitudinal (εls) strain can detect myocardial fibrosis.

METHODS

156 CMRs with gadolinium were performed in 66 DMD boys and included: (1) left ventricular ejection fraction (LVEF), (2) LGE, (3) native T1 mapping and myocardial tagging (εcc-tag measured using harmonic phase analysis). LGE was graded as: (1) presence/absence by segment, slice, and globally; (2) global severity from 0 (no LGE) to 4 (severe); (3) percent LGE using full width half maximum (FWHM). εls and εcc measured using feature tracking. Regression models to predict LGE included native T1 and either εcc-tag or εls and εcc measured at each segment, slice, and globally.

RESULTS

Mean age and LVEF at first CMR were 14 years and 54%, respectively. Global εls and εcc strongly predicted presence or absence of LGE (OR 2.6 [1.1, 6.0], p = 0.029, and OR 2.3 [1.0, 5.1], p = 0.049, respectively) while global native T1 did not. Global εcc, εls, and native T1 predicted global severity score (OR 2.6 [1.4, 4.8], p = 0.002, OR 2.6 [1.4, 6.0], p = 0.002, and OR 1.8 [1.1, 3.1], p = 0.025, respectively). εls correlated with change in LGE by severity score (n = 33, 3.8 [1.0, 14.2], p = 0.048) and εcc-tag correlated with change in percent LGE by FWHM (n = 34, OR 0.2 [0.1, 0.9], p = 0.01).

CONCLUSIONS

Pre-contrast sequences predict presence and severity of LGE, with εls and εcc being more predictive in most models, but there was not an observable advantage over using LVEF as a predictor. Change in LGE was predicted by εls (global severity score) and εcc-tag (FWHM). While statistically significant, our results suggest these sequences are currently not a replacement for LGE and may only have utility in a very limited subset of DMD patients.

Cardiac extracellular volume fraction in cats with preclinical hypertrophic cardiomyopathy

Background

Cardiac magnetic resonance imaging (CMR) allows for detection of fibrosis in hypertrophic cardiomyopathy (HCM) by quantification of the extracellular volume fraction (ECV).

Hypothesis/Objectives

To quantify native T1 mapping and ECV in cats. We hypothesize that native T1 mapping and ECV will be significantly increased in HCM cats compared with healthy cats.

Animals

Seventeen healthy and 12 preclinical HCM, age‐matched, client‐owned cats.

Methods

Prospective observational study. Tests performed included indirect blood pressure, CBC, biochemical analysis including total thyroid, urinalysis, transthoracic echocardiogram, and CMR. Cats were considered healthy if all tests were within normal limits and a diagnosis of HCM was determined by the presence of left ventricular concentric hypertrophy ≥6 mm on echocardiography.

Results

There were statistically significant differences in LV mass (healthy = 5.87 g, HCM = 10.3 g, P < .0001), native T1 mapping (healthy = 1122 ms, HCM = 1209 ms, P = .004), and ECV (healthy = 26.0%, HCM = 32.6%, P < .0001). Variables of diastolic function including deceleration time of early diastolic transmitral flow (DTE), ratio between peak velocity of early diastolic transmitral flow and peak velocity of late diastolic transmitral flow (E : A), and peak velocity of late diastolic transmitral flow (A wave) were significantly correlated with ECV (DTE; r = 0.73 P = .007, E : A; r = −0.75 P = .004, A wave; r = 0.76 P = .004).

Conclusions and Clinical Importance

Quantitative assessment of cardiac ECV is feasible and can provide additional information not available using echocardiography.

Free-breathing simultaneous myocardial T1 and T2 mapping with whole left ventricle coverage

PURPOSE

To develop a free-breathing sequence, that is, Multislice Joint T₁ -T₂ , for simultaneous measurement of myocardial T₁ and T₂ for multiple slices to achieve whole left-ventricular coverage.

METHODS

Multislice Joint T₁ -T₂ adopts slice-interleaved acquisition to collect 10 single-shot electrocardiogram-triggered images for each slice prepared by saturation and T₂ preparation to simultaneously estimate myocardial T₁ and T₂ and achieve whole left-ventricular coverage. Prospective slice-tracking using a respiratory navigator and retrospective image registration are used to reduce through-plane and in-plane motion, respectively. Multislice Joint T₁ -T₂ was validated through numerical simulations and phantom and in vivo experiments, and compared with saturation-recovery single-shot acquisition and T₂ -prepared balanced Steady-State Free Precession (T₂ -prep SSFP) sequences.

RESULTS

Phantom T₁ and T₂ from Multislice Joint T₁ -T₂ had good accuracy and precision, and were insensitive to heart rate. Multislice Joint T₁ -T₂ yielded T₁ and T₂ maps of nine left-ventricular slices in 1.4 minutes. The mean left-ventricular T₁ difference between saturation-recovery single-shot acquisition and Multislice Joint T₁ -T₂ across healthy subjects and patients was 191 ms (1564 ± 60 ms versus 1373 ± 50 ms; P < .05) and 111 ms (1535 ± 49 ms vs 1423 ± 49 ms; P < .05), respectively. The mean difference in left-ventricular T₂ between T₂ -prep SSFP and Multislice Joint T₁ -T₂ across healthy subjects and patients was -6.3 ms (42.4 ± 1.4 ms vs 48.7 ± 2.5; P < .05) and -5.7 ms (41.6 ± 2.5 ms vs 47.3 ± 2.7; P < .05), respectively.

CONCLUSION

Multislice Joint T₁ -T₂ enables quantification of whole left-ventricular T₁ and T₂ during free breathing within a clinically feasible scan time of less than 2 minutes.

Current evidence on the diagnostic and prognostic role of native T1 mapping in heart diseases

Tissue characterization represents a prerogative of cardiac magnetic resonance. Beside late gadolinium enhancement, native T1 mapping (nT1m) reveals tissue composition. It could represent a useful tool for example when contrast medium can't be administrated. The present review summarises current evidence about nT1m in main heart diseases.

Associations of B-type natriuretic peptide (BNP) and dialysis vintage with CMRI-derived cardiac indices in stable hemodialysis patients with a preserved left ventricular ejection fraction

To assess left ventricular myocardial native T1/T2 values and systolic strain and their associations with B-type natriuretic peptide (BNP) and dialysis vintage in hemodialysis (HD) patients with a preserved left ventricular ejection fraction (LVEF). Forty-three HD patients with end-stage renal disease (ESRD) but a preserved LVEF (≥ 50%) and 28 healthy volunteers were enrolled. BNP was measured at the time of cardiac magnetic resonance (CMR) measurements. Global native T1 and T2 values were significantly higher in the HD patients (native T1: 1056 ± 32 ms vs. 1006 ± 25 ms, p < 0.001; T2: 50 ± 3 ms vs. 46 ± 2 ms, p < 0.001) than in the controls. The mean peak global circumferential strain (GCS) and global longitudinal strain (GLS) were both significantly reduced in the HD patients compared with the controls (GCS: - 13 ± 3 vs. - 16 ± 3, p < 0.001; GLS: - 12 ± 4 vs. - 15 ± 3, p = 0.001). In the HD patients, the global native T1 value showed a positive correlation with the global T2 value (r = 0.311, p = 0.042) and significant correlations with GCS (r = 0.564, p < 0.001) and GLS (r = 0.359, p = 0.018). Significant positive correlations were found between lg BNP levels and T2 values (r = 0.569, p < 0.0001) and the left atrial volume index (LAVI) (r = 0.536, p = 0.012). GLS showed significant positive correlations with the LVMI (r = 0.354, p = 0.020) and dialysis vintage (p = 0.026; r = - 0.339) in the HD patients. HD patients with a preserved LVEF have increased native T1/T2 values and decreased strain compared to controls. T2 values and the LVAI were positively associated with BNP in HD patients.

Characterization of interstitial diffuse fibrosis patterns using texture analysis of myocardial native T1 mapping

Background

The pattern of myocardial fibrosis differs significantly between different cardiomyopathies. Fibrosis in hypertrophic cardiomyopathy (HCM) is characteristically as patchy and regional but in dilated cardiomyopathy (DCM) as diffuse and global. We sought to investigate if texture analyses on myocardial native T₁ mapping can differentiate between fibrosis patterns in patients with HCM and DCM.

Methods

We prospectively acquired native myocardial T₁ mapping images for 321 subjects (55±15 years, 70% male): 65 control, 116 HCM, and 140 DCM patients. To quantify different fibrosis patterns, four sets of texture descriptors were used to extract 152 texture features from native T₁ maps. Seven features were sequentially selected to identify HCM- and DCM-specific patterns in 70% of data (training dataset). Pattern reproducibility and generalizability were tested on the rest of data (testing dataset) using support vector machines (SVM) and regression models.

Results

Pattern-derived texture features were capable to identify subjects in HCM, DCM, and controls cohorts with 202/237(85.2%) accuracy of all subjects in the training dataset using 10-fold cross-validation on SVM (AUC = 0.93, 0.93, and 0.93 for controls, HCM and DCM, respectively), while pattern-independent global native T₁ mapping was poorly capable to identify those subjects with 121/237(51.1%) accuracy (AUC = 0.78, 0.51, and 0.74) (P<0.001 for all). The pattern-derived features were reproducible with excellent intra- and inter-observer reliability and generalizable on the testing dataset with 75/84(89.3%) accuracy.

Conclusion

Texture analysis of myocardial native T₁ mapping can characterize fibrosis patterns in HCM and DCM patients and provides additional information beyond average native T₁ values.

Clinical Importance of Myocardial T2 Mapping and Texture Analysis

Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) is valuable for diagnosis and assessment of the severity of various myocardial diseases owing to its potential to visualize myocardial scars. T₁ mapping is complementary to LGE because it can quantify the degree of myocardial fibrosis or edema. As such, T₁-weighted imaging techniques, including LGE using an inversion recovery sequence, contribute to cardiac MRI. T₂-weighted imaging is widely used to characterize the tissue of many organs. T₂-weighted imaging is used in cardiac MRI to identify myocardial edema related to chest pain, acute myocardial diseases, or severe myocardial injuries. However, it is difficult to determine the presence and extent of myocardial edema because of the low contrast between normal and diseased myocardium and image artifacts of T₂-weighted images and the lack of an established method to quantify the images. T₂ mapping quantifies myocardial T₂ values and help identify myocardial edema. The T₂ values are significantly related to the clinical symptoms or severity of nonischemic cardiomyopathy. Texture analysis is a postprocessing method to quantify tissue alterations that are reflected in the T₂-weighted images. Texture analysis provides a variety of parameters, such as skewness, entropy, and grey-scale non-uniformity, without the need for additional sequences. The abnormal signal intensity on T₂-weighted images or T₂ values may correspond to not only myocardial edema but also other tissue alterations. In this review, the techniques of cardiac T₂ mapping and texture analysis and their clinical relevance are described.

Automated Myocardial T2 and Extracellular Volume Quantification in Cardiac MRI Using Transfer Learning-based Myocardium Segmentation

Purpose

To assess the performance of an automated myocardial T2 and extracellular volume (ECV) quantification method using transfer learning of a fully convolutional neural network (CNN) pretrained to segment the myocardium on T1 mapping images.

Materials and Methods

A single CNN previously trained and tested using 11 550 manually segmented native T1-weighted images was used to segment the myocardium for automated myocardial T2 and ECV quantification. Reference measurements from 1525 manually processed T2 maps and 1525 ECV maps (from 305 patients) were used to evaluate the performance of the pretrained network. Correlation coefficient (R) and Bland-Altman analysis were used to assess agreement between automated and reference values on per-patient, per-slice, and per-segment analyses. Furthermore, transfer learning effectiveness in the CNN was evaluated by comparing its performance to four CNNs trained using manually segmented T2-weighted and postcontrast T1-weighted images and initialized using random-weights or weights of the pretrained CNN.

Results

T2 and ECV measurements using the pretrained CNN strongly correlated with reference values in per-patient (T2: R = 0.88, 95% confidence interval [CI]: 0.85, 0.91; ECV: R = 0.91, 95% CI: 0.89, 0.93), per-slice (T2: R = 0.83, 95% CI: 0.81, 0.85; ECV: R = 0.84, 95% CI: 0.82, 0.86), and per-segment (T2: R = 0.75, 95% CI: 0.74, 0.77; ECV: R = 0.76, 95% CI: 0.75, 0.77) analyses. In Bland-Altman analysis, the automatic and reference values were in good agreement in per-patient (T2: 0.3 msec ± 2.9; ECV: -0.3% ± 1.7), per-slice (T2: 0.1 msec ± 4.6; ECV: -0.3% ± 2.5), and per-segment (T2: 0.0 msec ± 6.5; ECV: -0.4% ± 3.5) analyses. The performance of the pretrained network was comparable to networks refined or trained from scratch using additional manually segmented images.

Conclusion

Transfer learning extends the utility of pretrained CNN-based automated native T1 mapping analysis to T2 and ECV mapping without compromising performance. Supplemental material is available for this article. © RSNA, 2020.

Measurement reproducibility of slice-interleaved T1 and T2 mapping sequences over 20 months: A single center study

BACKGROUND

Quantifying reproducibility of native T1 and T2 mapping over a long period (> 1 year) is necessary to assess whether changes in T1 and T2 over repeated sessions in a longitudinal study are associated with variability due to underlying tissue composition or technical confounders.

OBJECTIVES

To carry out a single-center phantom study to 1) investigate measurement reproducibility of slice-interleaved T1 (STONE) and T2 mapping over 20 months, 2) quantify sources of variability, and 3) compare reproducibility and measurements against reference spin-echo measurements.

METHODS

MR imaging was performed on a 1.5 Tesla Philips Achieva scanner every 2-3 weeks over 20 months using the T1MES phantom. In each session, slice-interleaved T1 and T2 mapping was repeated 3 times for 5 slices, and maps were reconstructed using both 2-parameter and 3-parameter fit models. Reproducibility between sessions, and repeatability between repetitions and slices were evaluated using coefficients of variation (CV). Different sources of variability were quantified using variance decomposition analysis. The slice-interleaved measurement was compared to the spin-echo reference and MOLLI.

RESULTS

Slice-interleaved T1 had excellent reproducibility and repeatability with a CV < 2%. The main sources of T1 variability were temperature in 2-parameter maps, and slice in 3-parameter maps. Superior between-session reproducibility to the spin-echo T1 was shown in 2-parameter maps, and similar reproducibility in 3-parameter maps. Superior reproducibility to MOLLI T1 was also shown. Similar measurements to the spin-echo T1 were observed with linear regression slopes of 0.94-0.99, but slight underestimation. Slice-interleaved T2 showed good reproducibility and repeatability with a CV < 7%. The main source of T2 variability was slice location/orientation. Between-session reproducibility was lower than the spin-echo T2 reference and showed good measurement agreement with linear regression slopes of 0.78-1.06.

CONCLUSIONS

Slice-interleaved T1 and T2 mapping sequences yield excellent long-term reproducibility over 20 months.

Cardiac profile of the Czech population of Duchenne muscular dystrophy patients: a cardiovascular magnetic resonance study with T1 mapping

BACKGROUND

The progressive cardiomyopathy that develops in boys with Duchenne and Becker muscular dystrophy (DMD/BMD) is presumed to be a secondary consequence of the fibrosis within the myocardium. There are only limited data on using parametric imaging in these patients. The purpose of this study was to assess native T1 and extracellular volume (ECV) values in DMD patients.

METHODS

The Czech population of males with DMD/BMD was screened. All eligible patients fulfilling the inclusion criteria were included. Forty nine males underwent cardiac magnetic resonance (MR) examination including T1 native and post-contrast mapping measurements. One DMD patient and all BMD patients were excluded from statistical analysis. Three groups were compared - Group D1 - DMD patients without late gadolinium enhancement (LGE) (n = 23), Group D2 - DMD patients with LGE (n = 20), and Group C - gender matched controls (n = 13).

RESULTS

Compared to controls, both DMD groups had prolonged T1 native relaxation time. These results are concordant in all 6 segments as well as in global values (1041 ± 31 ms and 1043 ± 37 ms vs. 983 ± 15 ms, both p < 0.05). Group D2 had significantly increased global ECV (0.28 ± 0.044 vs. 0.243 ± 0.013, p < 0.05) and segmental ECV in inferolateral and anterolateral segments in comparison with controls. The results were also significant after adjustment for subjects' age.

CONCLUSION

DMD males had increased native T1 relaxation time independent of the presence or absence of myocardial fibrosis. Cardiac MR may provide clinically useful information even without contrast media administration.

Comparison of native myocardial T1 and T2 mapping at 1.5T and 3T in healthy volunteers : Reference values and clinical implications

Background

Myocardial native T1 and T2 mapping are promising techniques for quantitative assessment of diffuse myocardial pathologies; however, due to conflicting data regarding normal values, routine clinical implementation of this method is still challenging.

Methods

To evaluate this situation during daily clinical practice the characteristics of normal values obtained in 60 healthy volunteers who underwent magnetic resonance imaging (MRI) scans on 1.5T and 3T scanners were studied. The T1 modified look-locker inversion recovery (MOLLI; 5(3)3; modified for higher heart rates) and T2 navigator gated black-blood prepared gradient-spin-echo (GraSE) sequences were used.

Results

While age and body mass index did not affect relaxation times, a gender and heart rate dependency was found showing higher T1 and T2 values in females, whereas at higher heart rates a prolongation of T1 and a shortening of T2 relaxation times was found. Particularly prone to artifacts were T2 measurements at 3T and the inferolateral wall. In the individual setting mean relaxation times for T1 were 995.8 ± 30.9 ms at 1.5T and 1183.8 ± 37.5 ms at 3T and 55.8 ± 2.8 ms at 1.5T and 51.6 ± 3 ms at 3T for T2 indicating a high dependency of reference values on MRI protocol when compared to the literature. Furthermore, as presumed mean T1 and T2 values correlated in the same individual.

Conclusions

The T1 and T2 relaxation times depend on physiological factors and especially on MRI protocols. Therefore, reference values should be validated individually in every radiological institution before implementing mapping protocols in daily clinical practice. Correlation of mean T1 and T2 values in the same proband at both field strengths indicates intraindividual reproducibility.

Increased myocardial native T1 relaxation time in patients with nonischemic dilated cardiomyopathy with complex ventricular arrhythmia

PURPOSE

To study the relationship between diffuse myocardial fibrosis and complex ventricular arrhythmias (ComVA) in patients with nonischemic dilated cardiomyopathy (NICM). We hypothesized that NICM patients with ComVA would have a higher native myocardial T1 time, suggesting more extensive myocardial diffuse fibrosis.

MATERIALS AND METHODS

We prospectively enrolled NICM patients with a history of ComVA (n = 50) and age-matched NICM patients without ComVA (n = 57). Imaging was performed at 1.5T with a protocol that included cine magnetic resonance imaging (MRI) for left ventricular (LV) function, late gadolinium enhancement (LGE) for focal scar, and native T1 mapping for diffuse fibrosis assessment.

RESULTS

Global native T1 time was significantly higher in patients with NICM with ComVA when compared to patients with NICM without ComVA (1131 ± 42 vs. 1107 ± 45 msec, P = 0.006), and this finding remained after excluding segments with scar on LGE (1124 ± 36 vs. 1102 ± 44 msec, P = 0.006). Native T1 was similar in NICM patients with and without the presence of LGE (1121 ± 39 vs. 1117 ± 48 msec, P = 0.68) and mildly correlated with LV end-diastolic volume index (r = 0.27, P = 0.005), LV end-systolic volume index (r = 0.24, P = 0.01), and LV ejection fraction (r = -0.28, P = 0.003). Native T1 value for each 10-msec increment was an independent predictor of ComVA (odds ratio 1.14, 95% confidence interval 1.03-1.25; P = 0.008) beyond LV function and LGE.

CONCLUSION

NICM patients with ComVA have higher native T1 compared to NICM without any documented ComVA. Native myocardial T1 is independently associated with ComVA, after adjusting for LV function and LGE.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:779-786. In memoriam: The authors are grateful for Dr. Josephson's inspiring guidance and contributions to this study.

Biventricular mechanics in prediction of severe myocardial fibrosis in patients with dilated cardiomyopathy: CMR study

PURPOSE

The purpose of this study was to compare the ability of various parameters of myocardial mechanics to predict large amounts of biventricular fibrosis assessed via T1 mapping in patients with dilated cardiomyopathy (DCM).

MATERIAL

Cardiovascular magnetic resonance feature tracking analysis and T1 mapping were performed in 26 patients with DCM [mean age: 34.4±9.1years, 15 (57.6%) males]. The values of various parameters of myocardial mechanics at predicting advanced left-ventricle (LV) and right-ventricle (RV) fibrosis were compared using logistic regression analysis and receiver operating characteristic curve (ROC) analysis.

RESULTS

There were 7 (26.9%) patients with a large amount of LV fibrosis and 9 (34.6%) patients with severe RV fibrosis. ROC curve analysis revealed that the model of combined LV strain rates (AUC=0.902) offered superb ability at predicting large amounts of LV fibrosis. The models including RV strain rates (AUC=0.974), a combination of RV strains, strain rates and clinical parameters (AUC=0.993) as well as the RV radial strain rate alone model (AUC=0.961) yielded outstanding performance in discriminating large and small amounts of RV fibrosis. In multivariate analysis, the LV circumferential strain (LVCR) and RV radial (RVR) strain rate were the only independent predictors of large amounts of LV and RV fibrosis, respectively.

CONCLUSIONS

Indices of myocardial deformation, especially combined with clinical features, offered a superlative ability to differentiate high from low degrees of fibrosis in DCM patients. Among all analyzed parameters of myocardial mechanics, LVCR and RVR rate alone were the independent predictors of high degrees of LV and RV fibrosis, respectively.

Defining myocardial tissue abnormalities in end-stage renal failure with cardiac magnetic resonance imaging using native T1 mapping

Noninvasive quantification of myocardial fibrosis in end-stage renal disease is challenging. Gadolinium contrast agents previously used for cardiac magnetic resonance imaging (MRI) are contraindicated because of an association with nephrogenic systemic fibrosis. In other populations, increased myocardial native T1 times on cardiac MRI have been shown to be a surrogate marker of myocardial fibrosis. We applied this method to 33 incident hemodialysis patients and 28 age- and sex-matched healthy volunteers who underwent MRI at 3.0T. Native T1 relaxation times and feature tracking–derived global longitudinal strain as potential markers of fibrosis were compared and associated with cardiac biomarkers. Left ventricular mass indices were higher in the hemodialysis than the control group. Global, Septal and midseptal T1 times were all significantly higher in the hemodialysis group (global T1 hemodialysis 1171 ± 27 ms vs. 1154 ± 32 ms; septal T1 hemodialysis 1184 ± 29 ms vs. 1163 ± 30 ms; and midseptal T1 hemodialysis 1184 ± 34 ms vs. 1161 ± 29 ms). In the hemodialysis group, T1 times correlated with left ventricular mass indices. Septal T1 times correlated with troponin and electrocardiogram-corrected QT interval. The peak global longitudinal strain was significantly reduced in the hemodialysis group (hemodialysis -17.7±5.3% vs. -21.8±6.2%). For hemodialysis patients, the peak global longitudinal strain significantly correlated with left ventricular mass indices (R = 0.426), and a trend was seen for correlation with galectin-3, a biomarker of cardiac fibrosis. Thus, cardiac tissue properties of hemodialysis patients consistent with myocardial fibrosis can be determined noninvasively and associated with multiple structural and functional abnormalities.