T1 Mapping in Characterizing Myocardial Disease: A Comprehensive Review

Assessment of the healing process after percutaneous implantation of a cardiovascular device: a systematic review

The healing process, occurring after intra-cardiac and intra-vascular device implantation, starts with fibrin condensation and attraction of inflammatory cells, followed by the formation of fibrous tissue that slowly covers the device. The duration of this process is variable and may be incomplete, which can lead to thrombus formation, dislodgement of the device or stenosis. To better understand this process and the neotissue formation, animal models were developed: small (rats and rabbits) and large (sheep, pigs, dogs and baboons) animal models for intra-vascular device implantation; sheep and pigs for intra-cardiac device implantation. After intra-vascular and intra-cardiac device implantation in these animal models, in vitro techniques, i.e. histology, which is the gold standard and scanning electron microscopy, were used to assess the device coverage, characterize the cell constitution and detect complications such as thrombosis. In humans, optical coherence tomography and intra-vascular ultrasounds are both invasive modalities used after stent implantation to assess the structure of the vessels, atheroma plaque and complications. Non-invasive techniques (computed tomography and magnetic resonance imaging) are in development in humans and animal models for tissue characterization (fibrosis), device remodeling evaluation and device implantation complications (thrombosis and stenosis). This review aims to (1) present the experimental models used to study this process on cardiac devices; (2) focus on the in vitro techniques and invasive modalities used currently in humans for intra-vascular and intra-cardiac devices and (3) assess the future developments of non-invasive techniques in animal models and humans for intra-cardiac devices.

Aortic stiffness is independently associated with interstitial myocardial fibrosis by native T1 and accelerated in the presence of chronic kidney disease

BACKGROUND

Patients with chronic kidney disease (CKD) have considerable cardiovascular morbidity and mortality. Aortic stiffness is an independent predictor of cardiovascular risk and related to left ventricular remodeling and heart failure. Myocardial fibrosis is the pathophysiological hallmark of the failing heart.

METHODS AND RESULTS

An observational study of consecutive CKD patients (n = 276) undergoing comprehensive clinical cardiovascular magnetic resonance imaging. The relationship between aortic stiffness, myocardial fibrosis, left ventricular remodeling and the severity of chronic kidney disease was examined. Compared to age-gender matched controls with no known kidney disease (n = 242), CKD patients had considerably higher myocardial native T1 and central aortic PWV (p ≪ 0.001), as well as abnormal diastolic relaxation by E/e' (mean) by echocardiography (p ≪ 0.01). A third of all patients had LGE, with similar proportions for the presence and the (ischaemic and non-ischaemic) pattern between the groups. PWV was strongly associated with and age, NT-proBNP and native T1 in both groups, but not with LGE presence or type; the associations were amplified in severe CKD stages. In multivariate analyses, PWV was independently associated with native T1 in both groups (p ≪ 0.01) with near two-fold increase in adjusted R2 in the presence of CKD (native T1 (10 ms) R2, B(95%CI) CKD vs. non-CKD 0.28, 0.2(0.15-0.25) vs. 0.18, 0.1(0.06-0.15), p ≪ 0.01).

CONCLUSIONS

Aortic stiffness and interstitial myocardial fibrosis are interrelated; this association is accelerated in the presence of CKD, but independent of LGE. Our findings reiterate the significant contribution of CKD-related factors to the pathophysiology of cardiovascular remodeling.

Cardiac dysfunction in cirrhosis: a 2-yr longitudinal follow-up study using advanced cardiac imaging

The temporal relationship between cirrhotic cardiomyopathy, progression of liver disease, and survival remains unknown. Our aim was to investigate the development of structural and functional cardiac changes over time with the progression of cirrhosis and outcome. Sixty-three cirrhotic outpatients (Child class: A = 9, B = 46, C = 8) and 14 healthy controls were included in this 2-yr longitudinal study. Advanced cardiac characteristics such as cardiac MRI with extracellular volume (ECV) quantification, speckle tracking echocardiography, and biomarkers were assessed at 0/6/12/18/24 mo. Patients were followed-up for a median of 30 mo with registration of acute decompensations (ADs), liver transplantations (LTs), and deaths. Patients who progressed, underwent LT or died had more pronounced cardiac dysfunction, structural myocardial changes, and left atrial enlargement. Conversely, limited cardiac deterioration was seen in patients who remained stable or improved in cirrhosis. During follow-up 25 patients developed AD, 4 underwent LT, and 20 died. Mean arterial pressure was the only cardiovascular parameter associated with death in a univariate analysis (P = 0.037), and the main predictors were model for end-stage liver disease and age. However, last-visit myocardial ECV was independently associated with the combined end point of LT/death (P = 0.001), and in patients with AD a low cardiac index was independently associated with death (P = 0.01). Cardiac function seems to deteriorate with the progression of cirrhosis and affects prognosis, especially in patients with AD. Conversely, patients with stable cirrhosis have limited progression in cardiac dysfunction over a 2-yr period with modest impact on survival. The results encourage careful cardiac monitoring in advanced cirrhosis.NEW & NOTEWORTHY For the first time, we have performed advanced cardiac imaging to investigate the development of cirrhotic cardiomyopathy over 2 years. We show that cardiac dysfunction deteriorates with progression of cirrhosis and may affect the prognosis in patients developing acute decompensation. Especially, structural myocardial abnormalities, left atrial enlargement, and a hypodynamic cardiac state seem of importance. Conversely, limited cardiac progression is seen in stable cirrhosis. These findings provide new insight into our understanding of cirrhotic cardiomyopathy.

Early detection of heart function abnormality by native T1: a comparison of two T1 quantification methods

Objective

To compare the robustness of native T1 mapping using mean and median pixel-wise quantification methods.

Methods

Fifty-seven consecutive patients without overt signs of heart failure were examined in clinical routine for suspicion of cardiomyopathy. MRI included the acquisition of native T1 maps by a motion-corrected modified Look-Locker inversion recovery sequence at 1.5 T. Heart function status according to four established volumetric left ventricular (LV) cardio MRI parameter thresholds was used for retrospective separation into subgroups of normal (n = 26) or abnormal heart function (n = 31). Statistical normality of pixel-wise T1 was tested on each myocardial segment and mean and median segmental T1 values were assessed.

Results

Segments with normally distributed pixel-wise T1 (57/58%) showed no difference between mean and median quantification in either patient group, while differences were highly significant (p < 0.001) for the respective 43/42% non-normally distributed segments. Heart function differentiation between two patient groups was significant in 14 myocardial segments (p < 0.001–0.040) by median quantification compared with six (p < 0.001–0.042) by using the mean. The differences by median quantification were observed between the native T1 values of the three coronary artery territories of normal heart function patients (p = 0.023) and insignificantly in the abnormal patients (p = 0.053).

Conclusion

Median quantification increases the robustness of myocardial native T1 definition, regardless of statistical normality of the data. Compared with the currently prevailing method of mean quantification, differentiation between LV segments and coronary artery territories is better and allows for earlier detection of heart function impairment.

Key Points

• Median pixel-wise quantification of native T1 maps is robust and can be applied regardless of the statistical distribution of data points.

• Median quantification is more sensitive to early heart function abnormality compared with mean quantification.

• The new method yields significant native T1 value differentiation between the three coronary artery territories.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06364-9) contains supplementary material, which is available to authorized users.

Native T1 and ECV of Noninfarcted Myocardium and Outcome in Patients With Coronary Artery Disease

BACKGROUND

Coronary artery disease (CAD) remains the major cause of cardiac morbidity and mortality worldwide, despite the advances in treatment with coronary revascularization and modern antiremodeling therapy. Risk stratification in CAD patients is primarily based on left ventricular volumes, ejection fraction (LVEF), risk scores, and the presence and extent of late gadolinium enhancement (LGE). The prognostic role of T1 mapping in noninfarcted myocardium in CAD patients has not yet been determined.

OBJECTIVES

This study sought to examine prognostic significance of native T1 mapping of noninfarcted myocardium in patients with CAD.

METHODS

A prospective, observational, multicenter longitudinal study of consecutive patients undergoing routine cardiac magnetic resonance imaging with T1 mapping and LGE. The primary endpoint was all-cause mortality. Major adverse cardiocerebrovascular events (MACCE) (cardiac mortality, nonfatal acute coronary syndrome, stroke, and appropriate device discharge) are also reported.

RESULTS

A total of 34 deaths and 71 MACCE (n = 665, males n = 424, median age [interquartile range] 57 [22] years; 64%; median follow-up period of 17 [11] months) were observed. Native T1 and extracellular volume were univariate predictors of outcome. Native T1 and LGE were stronger predictors of survival and MACCE compared with extracellular volume, LVEF, cardiac volumes, and clinical scores (p < 0.001). Native T1 of noninfarcted myocardium was the sole independent predictor of all-cause mortality (chi-square = 21.7; p < 0.001), which was accentuated in the absence of LGE or LVEF ≤35%. For MACCE, native T1 and LGE extent were joint independent predictors (chi-square = 25.6; p < 0.001).

CONCLUSIONS

Characterization of noninfarcted myocardium by native T1 is an important predictor of outcome in CAD patients, over and above the traditional risk stratifiers. The current study's results provide a basis for a novel risk stratification model in CAD based on a complementary assessment of noninfarcted myocardium and post-infarction scar, by native T1 mapping and LGE, respectively.

Liver MR relaxometry at 3T - segmental normal T1 and T2* values in patients without focal or diffuse liver disease and in patients with increased liver fat and elevated liver stiffness

Magnetic resonance (MR) T₁ and T₂* mapping allows quantification of liver relaxation times for non-invasive characterization of diffuse liver disease. We hypothesized that liver relaxation times are not only influenced by liver fibrosis, inflammation and fat, but also by air in liver segments adjacent to the lung – especially in MR imaging at 3T. A total of 161 study participants were recruited, while 6 patients had to be excluded due to claustrophobia or technically uninterpretable MR elastography. Resulting study population consisted of 12 healthy volunteers and 143 patients who prospectively underwent multiparametric MR imaging at 3T. Of those 143 patients, 79 had normal liver stiffness in MR elastography (shear modulus <2.8 kPa, indicating absence of fibrosis) and normal proton density fat fraction (PDFF < 10%, indicating absence of steatosis), defined as reference population. T₁ relaxation times in these patients were significantly shorter in liver segments adjacent to the lung than in those not adjacent to the lung (p < 0.001, mean of differences 33 ms). In liver segments not adjacent to the lung, T₁ allowed to differentiate significantly between the reference population and patients with steatosis and/or fibrosis (p ≤ 0.011), while there was no significant difference of T₁ between the reference population and healthy volunteers. In conclusion, we propose to measure T₁ relaxation times in liver segments not adjacent to the lung. Otherwise, we recommend taking into account slightly shorter T₁ values in liver segments adjacent to the lung.

Myocardial native-T1 times are elevated as a function of hypertrophy, HbA1c, and heart rate in diabetic adults without diffuse fibrosis

PURPOSE

Cardiac native-T1 times have correlated to extracellular volume fraction in patients with confirmed fibrosis. However, whether other factors that can occur either alongside or independently of fibrosis including increased intracellular water volume, altered magnetization transfer (MT), or glycation of hemoglobin, lengthen T1 times in the absence of fibrosis remains unclear. The current study examined whether native-T1 times are elevated in hypertrophic diabetics with elevated hemoglobin A1C (HbA1c) without diffuse fibrosis.

METHODS

Native-T1 times were quantified in 27 diabetic and 10 healthy adults using a modified Look-Locker imaging (MOLLI) sequence at 1.5 T. The MT ratio (MTR) was quantified using dual flip angle cine balanced steady-state free precession. Gadolinium (0.2 mmol/kg Gd-DTPA) was administered as a bolus and post-contrast T1-times were quantified after 15 min. Means were compared using a two-tailed student's t-test, while correlations were assessed using Pearson's correlations.

RESULTS

While left ventricular volumes, ejection fraction, and cardiac output were similar between groups, left ventricular mass and mass-to-volume ratio (MVR) were significantly higher in diabetic adults. Mean ECV (0.25 ± 0.02 Healthy vs. 0.25 ± 0.03 Diabetic, P = 0.47) and MTR (125 ± 16% Healthy vs. 125 ± 9% Diabetic, P = 0.97) were similar, however native-T1 times were significantly higher in diabetics (1016 ± 21 ms Healthy vs. 1056 ± 31 ms Diabetic, P = 0.00051). Global native-T1 times correlated with MVR (ρ = 0.43, P = 0.008) and plasma HbA1c levels (ρ = 0.43, P = 0.0088) but not ECV (ρ = 0.06, P = 0.73). Septal native-T1 times correlated with septal wall thickness (ρ = 0.50, P = 0.001).

CONCLUSION

In diabetic adults with normal ECV values, elevated native-T1 times may reflect increased intracellular water volume and changes secondary to increased hemoglobin glycation.

T1 reactivity as an imaging biomarker in myocardial tissue characterization discriminating normal, ischemic and infarcted myocardium

To demonstrate the potential for differentiating normal and diseased myocardium without Gadolinium using rest and stress T1-mapping. Patients undergoing 1.5T magnetic resonance imaging (MRI) as part of clinical work-up due to suspicion of coronary artery disease (CAD) were included. Adenosine stress perfusion MRI and late gadolinium enhancement (LGE) imaging were performed to identify ischemic and infarcted myocardium. Patients were retrospectively categorized into an ischemic, infarct and control group based on conventional acquisitions. Patient with both ischemic and infarcted myocardium were excluded. A total of 64 patients were included: ten with myocardial ischemia, 15 with myocardial infarction, and 39 controls. A native Modified Look-Locker Inversion Recovery (MOLLI) T1-mapping acquisition was performed at rest and stress. Pixel-wise myocardial T1-maps were acquired in short-axis view with inline motion-correction. Short-axis T1-maps were manually contoured using conservative septal sampling. Regions of interest were sampled in ischemic and infarcted areas detected on perfusion and LGE images. T1 reactivity was calculated as the percentage difference in T1 values between rest and stress. Remote myocardium was defined as myocardium without defects in the ischemic and infarcted group whereas normal myocardium is found in the control group only. Native T1-values were significantly higher in infarcted myocardium in rest and stress [median 1044 ms (interquartile range (IQR) 985–1076) and 1053 ms (IQR 989–1088)] compared to ischemic myocardium [median 961 ms (IQR 939–988) and 958 ms (IQR 945–988)]. T1-reactivity was significantly lower in ischemic and infarcted myocardium [median 0.00% (IQR − 0.18 to 0.16) and 0.41% (IQR 0.09–0.86)] compared to remote myocardium [median 3.54% (IQR 1.48–5.78) and 3.21% (IQR 1.95–4.79)]. Rest-stress T1-mapping is able to distinguish between normal, ischemic, infarcted and remote myocardium using native T1-values and T1-reactivity, and holds potential as an imaging biomarker for tissue characterization in MRI.

Myocardial fibrosis by late gadolinium enhancement cardiovascular magnetic resonance in myotonic muscular dystrophy type 1: highly prevalent but not associated with surface conduction abnormality

BACKGROUND

Conduction disease and arrhythmias represent a major cause of mortality in myotonic muscular dystrophy type 1 (MMD1). Permanent pacemaker (PPM) implantation is the cornerstone of therapy to reduce cardiovascular mortality in MMD1. Cardiovascular magnetic resonance (CMR) studies demonstrate a high prevalence of myocardial fibrosis in MMD1, however the association between CMR myocardial fibrosis with late gadolinium enhancement (CMR-LGE) and surface conduction abnormality is not well established in MMD1. We investigated whether myocardial fibrosis by CMR-LGE is associated with surface conduction abnormalities meeting criteria for PPM implantation according to current guidelines in a cohort of patients with genetically confirmed MMD1.

METHODS

Patients with genetically confirmed MMD1 were retrospectively evaluated. 12-lead electrocardiography (ECG) performed within 6 months of CMR was necessary for inclusion. The severity and extent of MMD1 was quantified using a validated Muscular Impairment Rating Scale (MIRS). Based on current guidelines for device-based therapy of cardiac rhythm abnormalities, we defined surface conduction abnormality as the presence of ECG alterations meeting criteria for PPM implant (class I or II indications): PR interval > 200 ms (type I atrioventricular (AV) block) and/or mono or bifascicular block (QRS > 120 ms), or evidence of advanced AV block. Balanced steady-state free precession sequences (bSSFP) were used for assessment of left ventricular (LV) volumes and ejection fraction. MOdified Look-Locker Inversion Recovery (MOLLI) acquisition schemes were used to acquire T1 maps. Patients' charts were reviewed up to 12 months post-CMR for occurrence of PPM implantation.

RESULTS

Fifty-two patients (38% male, 41 ± 14 years) were included. Overall, 31 (60%) patients had a surface conduction abnormality and 22 (42%) demonstrated midwall myocardial fibrosis by CMR-LGE. After a median of 57 days from CMR exam, 15 patients (29%) underwent PPM implantation. Subjects with vs. without surface conduction abnormality had significantly longer disease length (15.5 vs. 7.8 years, p = 0.015) and higher disease severity on the MIRS scale (p = 0.041). High prevalence of myocardial fibrosis by CMR-LGE was detected in subjects with and without surface conduction abnormality with no significant difference between the two cohorts (42% vs. 43%, p = 0.999). By multivariate logistic regression analysis, disease length was the only independent variable associated with surface conduction abnormality (OR 1.071, 95%CI 1.003-1.144, p = 0.040); while CMR-LGE was not associated with conduction abnormality (ρ = - 0.009, p = 0.949).

CONCLUSIONS

Myocardial fibrosis by CMR-LGE is highly prevalent in MMD1 but not related to surface conduction abnormality meeting current guideline criteria for PPM implantation .

Evaluation of myocardial fibrosis in diabetes with cardiac magnetic resonance T1-mapping: Correlation with the high-level hemoglobin A1c

AIM

The aim of the study was to assess the extracellular volume fraction (ECV) in type 2 diabetes mellitus (T2DM) patients with different level of hemoglobin A1c (HbA1c) by cardiac magnetic resonance (CMR), and the ability of HbA1c to predict myocardial fibrosis.

METHODS

In total, 80 T2DM patients and 20 age- and sex-matched controls were prospective enrolled and underwent CMR to obtain ECV value and LV function parameters. We divided all patients into a group of HbA1c < 7.0% and a group of HbA1c ≥ 7.0%.

RESULTS

In the higher HbA1c group the ECV value (all p < 0.001) was higher than both lower HbA1c group (36.23% vs. 32.19%, p < 0.001) and controls (36.23% vs. 29.73%, p < 0.001). HbA1c was positively associated (β = 0.36, p = 0.004) with ECV, and it was also an independent predictor of myocardial fibrosis (OR = 2.00, P = 0.014). The ROC analysis showed that 7.1% was the optimal cutoff value of HbA1c that predicted the risk of myocardial fibrosis with high diagnostic accuracy (area under the curve = 0.78).

CONCLUSION

T1 mapping provided myocardial fibrosis information in T2DM patients. HbA1c is positively correlated with myocardial fibrosis and can be an independently predictor of myocardial fibrosis, which may be helpful for the clinical decision-making of blood glucose control.

Diabetic cardiomyopathy - A comprehensive updated review

Diabetes causes cardiomyopathy and increases the risk of heart failure independent of hypertension and coronary heart disease. This condition called "Diabetic Cardiomyopathy" (DCM) is becoming a well- known clinical entity. Recently, there has been substantial research exploring its molecular mechanisms, structural and functional changes, and possible development of therapeutic approaches for the prevention and treatment of DCM. This review summarizes the recent advancements to better understand fundamental molecular abnormalities that promote this cardiomyopathy and novel therapies for future research. Additionally, different diagnostic modalities, up to date screening tests to guide clinicians with early diagnosis and available current treatment options has been outlined.

CXCR4 Antagonism Reduces Cardiac Fibrosis and Improves Cardiac Performance in Dilated Cardiomyopathy

Background: Myocardial fibrosis is a key pathologic finding in the failing heart and is implicated as a cause of increased ventricular stiffness and susceptibility to ventricular arrhythmia. Neurohormonal mediators such as aldosterone and angiotensin II are known to cause fibrosis in experimental models, however, clinical evidence for the reversal of fibrosis with relevant antagonists is limited. Recent studies suggest that inflammatory mediators may contribute to fibrosis. In dilated cardiomyopathy the mechanism for myocardial fibrosis is unclear and its implications on systolic function are not known. Methods and Results: We studied the effect of a highly selective antagonist of SDF-1/CXCR4 signaling, AMD3100, on the development of cardiac fibrosis and cardiac function in mice with dilated cardiomyopathy due to cardiac-specific transgenic overexpression of the stress-kinase, Mst1. AMD3100 significantly attenuated the progression of myocardial fibrosis and this was accompanied by significant improvements in diastolic and systolic performance as evaluated in isolated Langendorff perfused hearts. AMD3100 reduced BNP mRNA expression but did not alter the expression of Ca²⁺ handling genes. CXCR4 antagonism also reduced the abundance of splenic CD4⁺ T cells. Conclusion: This study demonstrates that CXCR4 pathway contributes to pathogenesis of cardiac fibrosis in dilated cardiomyopathy, and it represents a new potential therapeutic target in heart failure. The data also demonstrate that anti-fibrotic strategies can improve systolic performance.

Non-invasive evaluation of the relationship between electrical and structural cardiac abnormalities in patients with myotonic dystrophy type 1

BACKGROUND

Cardiac involvement in myotonic dystrophy type 1 (MD1) includes conduction disease, arrhythmias, and left-ventricular (LV) systolic dysfunction leading to an increased sudden cardiac death risk. An understanding of the interplay between electrical and structural myocardial changes could improve the prediction of adverse cardiac events. We aimed to explore the relationship between signs of cardiomyopathy by conventional and advanced cardiovascular magnetic resonance (CMR), and electrical abnormalities in MD1.

METHODS

Fifty-seven MD1 patients (43 ± 13 years, 46% male) and 15 matched controls (41 ± 7 years, 53% male) underwent CMR including cine-imaging with feature-tracking strain analysis, late gadolinium enhancement (LGE), and native/post-contrast T1-mapping with extracellular volume calculation. Standard 12-lead and long-term ECG monitoring were performed as screening for rhythm and/or conduction abnormalities.

RESULTS

Abnormal ECGs were recorded in 40% of MD1; a pathologic CMR was found in 44%: 21% had an impaired LV-EF and 32% showed non-ischemic LGE. When looking at MD1 patients with available long-term ECG monitoring (n = 39), those with atrial fibrillation (Afib)/flutter(Afl) episodes had lower LV-EF (52 ± 7 vs. 60 ± 5%, p = 0.002), lower global longitudinal strain (- 17 ± 3 vs. - 20 ± 3%, p = 0.034), a trend to lower left atrial emptying fraction (LA-EF) (44 ± 14 vs. 55 ± 8%, p = 0.08), and higher prevalence of LGE (88% vs. 23%, p = 0.001) with an intramural (75% vs. 23%, p = 0.01) and septal (63% vs. 13%, p = 0.009) pattern. In a model including LV-EF (OR 0.8, 95% CI 0.7-1.0, p = NS) and LGE presence (OR 14.8, 95% CI 1.4-159.0, p = 0.026), only LGE was independently associated with the occurrence of Afib/Afl episodes.

CONCLUSION

Myocardial abnormalities depicted by non-ischemic LGE-CMR were the only independent predictor for the occurrence of Afib/Afl on ECG monitoring, previously shown to predict adverse cardiac events in MD1.

Reference range determination for imaging biomarkers: Myocardial T1

BACKGROUND

Imaging biomarkers, such as the T₁ relaxation time of the myocardium using MRI, can be valuable in cardiac medicine if they are properly validated. Consensus statements recommend that for myocardial T₁ , each investigator should establish a reference range.

PURPOSE

To describe a statistically valid method for determining and reporting the reference range in each center, which simultaneously minimizes the twin risks of undersampling, leading to a uselessly uncertain range, and oversampling, which exposes volunteers to unnecessary scanning and wastes resources.

STUDY TYPE

Cohort.

POPULATION

In all, 278 normal human subjects without cardiac disease from two cardiac MR centers.

FIELD STRENGTH/SEQUENCE

1.5 T and 3 T; Modified Look-Locker Inversion recovery sequence.

ASSESSMENT

The T₁ relaxation time was estimated from multiple samples of tissue magnetization after inversion. A valid method for calculating a reference range was used.

STATISTICAL TESTS

Shapiro-Wilk test for normality; Tukey robust approach for identification of outliers; reference range calculation with confidence intervals.

RESULTS

Reference ranges for measurement of myocardial T₁ were calculated, with confidence intervals, enabling comparison with clinically important differences. At 3 T: 1129 to 1301 msec at site 1 (n = 21) and 1160 to 1309 msec at site 2 (n = 59), and at 1.5 T at site 2: 933 to 1020 msec (male, n = 130) and 965 to 1054 msec (female, n = 68). The 3 T reference range from site 1 was successfully benchmarked against the 3 T reference range at site 2.

DATA CONCLUSION

Myocardial T₁ reference ranges can be properly characterized, enabling clinical comparison to a valid reference range with known confidence intervals, using methodology similar to that described in this report.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2019;50:771-778.

T1 and extracellular volume fraction mapping in cardiac magnetic resonance: estimation of accuracy and precision of a novel algorithm

Magnetic resonance imaging is effective for non-invasive detection of myocardial diseases by extracellular volume fraction (ECV) estimation. A new methodology for T1 and ECV mapping is tested in this work, comparing results with other well-consolidated methods. The associated level of uncertainty for data was also estimated, to assess the reliability of the technique. A phantom with known T1 values was used for reference, and 60 subjects (40 controls, 20 diseased patients) were examined, using the modified look-locker inversion-recovery (MOLLI) method. Obtained T1 data were studied in terms of accuracy (difference with reference T1), paired comparisons with other methods, and Gamma-tool analysis with tolerances criteria of 4.21 mm for distance-to-agreement, and between 2%-5% for T1 difference. Accuracy and precision of the T1 mapping was analysed by phantom measurements, and the uncertainty of the ECV was estimated by T1 error propagation. Differences (in paired comparisons) of T1 datasets were not significant neither for statistical tests, nor for Bland-Altman analysis. T1 accuracy was between  -12% and  -1% across methods, slightly better for the tested method (mean accuracy in the T1 range of interest better than 2%). The Gamma analysis confirm slightly better results for the tested method than other methodologies. The new method improves the computational efficiency by a factor of 25 (at least), revealing to be also more suitable for Big Data-related applications.

Imaging and Impact of Myocardial Fibrosis in Aortic Stenosis

Aortic stenosis is characterized both by progressive valve narrowing and the left ventricular remodeling response that ensues. The only effective treatment is aortic valve replacement, which is usually recommended in patients with severe stenosis and evidence of left ventricular decompensation. At present, left ventricular decompensation is most frequently identified by the development of typical symptoms or a marked reduction in left ventricular ejection fraction <50%. However, there is growing interest in using the assessment of myocardial fibrosis as an earlier and more objective marker of left ventricular decompensation, particularly in asymptomatic patients, where guidelines currently rely on nonrandomized data and expert consensus. Myocardial fibrosis has major functional consequences, is the key pathological process driving left ventricular decompensation, and can be divided into 2 categories. Replacement fibrosis is irreversible and identified using late gadolinium enhancement on cardiac magnetic resonance, while diffuse fibrosis occurs earlier, is potentially reversible, and can be quantified with cardiac magnetic resonance T1 mapping techniques. There is a substantial body of observational data in this field, but there is now a need for randomized clinical trials of myocardial imaging in aortic stenosis to optimize patient management. This review will discuss the role that myocardial fibrosis plays in aortic stenosis, how it can be imaged, and how these approaches might be used to track myocardial health and improve the timing of aortic valve replacement.

Late effects of pediatric hematopoietic stem cell transplantation on left ventricular function, aortic stiffness and myocardial tissue characteristics

BACKGROUND

Pediatric hematopoietic stem cell transplantation (HSCT) recipients are at increased risk of cardiovascular disease later in life. As HSCT survival has significantly improved, with a growing number of HSCT indications, tailored screening strategies for HSCT-related late effects are warranted. Little is known regarding the value of cardiovascular magnetic resonance (CMR) for early identification of high-risk patients after HSCT, before symptomatic cardiovascular disease manifests. This study aimed to assess CMR-derived left ventricular (LV) systolic and diastolic function, aortic stiffness and myocardial tissue characteristics in young adults who received HSCT during childhood.

METHODS

Sixteen patients (22.1 ± 1.5 years) treated with HSCT during childhood and 16 healthy controls (22.1 ± 1.8 years) underwent 3 T CMR. LV systolic and diastolic function were measured as LV ejection fraction (LVEF), the ratio of transmitral early and late peak filling rate (E/A), the estimated LV filling pressure (E/Ea) and global longitudinal and circumferential systolic strain and diastolic strain rates, using balanced steady-state free precession cine CMR and 2D velocity-encoded CMR over the mitral valve. Aortic stiffness, myocardial fibrosis and steatosis were assessed with 2D velocity-encoded CMR, native T1 mapping and proton CMR spectroscopy (1H-CMRS), respectively.

RESULTS

In the patient compared to the control group, E/Ea (9.92 ± 3.42 vs. 7.24 ± 2.29, P = 0.004) was higher, LVEF (54 ± 6% vs. 58 ± 5%, P = 0.055) and global longitudinal strain (GLS) ( -20.7 ± 3.5% vs. -22.9 ± 3.0%, P = 0.063) tended to be lower, while aortic pulse wave velocity (4.40 ± 0.26 vs. 4.29 ± 0.29 m/s, P = 0.29), native T1 (1211 ± 36 vs. 1227 ± 28 ms, P = 0.16) and myocardial triglyceride content (0.47 ± 0.18 vs. 0.50 ± 0.13%, P = 0.202) were comparable. There were no differences between patients and controls in E/A (2.76 ± 0.92 vs. 2.97 ± 0.91, P = 0.60) and diastolic strain rates.

CONCLUSION

In young adults who received HSCT during childhood, LV diastolic function was decreased (higher estimated LV filling pressure) and LV systolic function (LVEF and GLS) tended to be reduced as compared to healthy controls, whereas no concomitant differences were found in aortic stiffness and myocardial tissue characteristics. When using CMR, assessment of LV diastolic function in particular is important for early detection of patients at risk of HSCT-related cardiovascular disease, which may warrant closer surveillance.

Young patient with hantavirus-induced myocarditis detected by comprehensive cardiac magnetic resonance assessment

Background

We report a case of hantavirus-induced myocarditis in a young adult. Hantavirus showed a rapid increase of infections in the year 2017. Only scarce data is available about potential myocardial involvement in hantavirus infections. With ECG and echocardiography providing often inconclusive results, a multiparametric cardiac magnetic resonance protocol with distinct myocardial tissue characterization seems to be the adequate tool for detecting even slight myocardial alterations.

Case presentation

This case started with the presentation of young adult suffering from headache and abdominal pain. Thrombocytes were decreased, creatinine was elevated, and there was massive proteinuria. Puumala virus IgG ELISA turned out to be positive, and specific antibodies (IgG and IgM) could be detected in the serum, and confirmed by immunoassay. The patient was admitted to the nephrology department for supportive therapy. Few days later, the patient reported chest pain and dyspnea. High sensitivity troponin I rose up to 0.32 μg/l (normal range below 0.04 μg/l) with an increase of the creatinkinase to 319 U/l (normal max. 190 U/l), no dynamic ECG changes could be observed. Echocardiography revealed a normal left ventricular function without regional wall motion abnormalities, no pericardial effusion or valve abnormalities, coronary artery disease could be excluded by computed tomography. A multiparametric cardiac magnetic resonance protocol including recent mapping techniques confirmed myocardial involvement induced by acute hantavirus infection. In the next few weeks, the patient’s state of health rapidly improved and symptoms of chest pain and dyspnea disappeared. Follow up multiparametric CMR exam showed substantial decrease of the previously observed myocardial alterations during acute hantavirus infection suggesting myocardial healing.

Conclusions

This case demonstrates that a CMR protocol including recent mapping techniques and established late gadolinium enhancement technique is an adequate non-invasive tool for both 1) initial detection, and 2) follow up of patients with hantavirus-induced myocarditis, which might be more common than previously known.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3658-8) contains supplementary material, which is available to authorized users.

The Added Value of Cardiac Magnetic Resonance in Muscular Dystrophies

Muscular dystrophies (MD) represent a heterogeneous group of rare genetic diseases that often lead to significant weakness due to progressive muscle degeneration. In many forms of MD, cardiac manifestations including heart failure, atrial and ventricular arrhythmias and conduction abnormalities can occur and may be a predominant feature of the disease. Cardiac magnetic resonance (CMR) can assess cardiac anatomy, global and regional ventricular function, volumes and mass as well as presence of myocardial inflammation, infiltration or fibrosis. The role for cardiac MRI has been well-established in a wide range of muscular dystrophies related cardiomyopathies. CMR is a more sensitive technique than echocardiography for early diagnosis of cardiac involvement. It has also great potential to improve the prediction of long-term outcome, particularly the development of heart failure and arrhythmic events; however it still has to be validated by longitudinal studies including large populations. This review will outline the utility of CMR in patients with muscular dystrophies for assessment of myocardial involvement, risk stratification, and in guiding therapeutic management.

Estimation of myocardial fibrosis in humans with dual energy CT

BACKGROUND

The current clinical standard for in vivo imaging of myocardial fibrosis is contrast-enhanced cardiac magnetic resonance (CMR). We sought to validate a novel non-contrast dual energy computed tomography (DECT) method to estimate myocardial fibrosis in patients undergoing CMR with contrast.

METHODS

All subjects underwent non-contrast, prospectively-triggered cardiac DECT on a single source scanner with interleaved acquisition between tube voltages of 80 and 140 kVp. Monochromatic images were reconstructed at 11 energies spanning 40-140 keV; a region of interest (ROI) was drawn in the mid-inferoseptal segment, recording mean attenuation value in the ROI, at each energy level. Comparison was made to data from single energy (70 keV) image data. Linear discriminant analysis (LDA) was performed to compare the predictive capability of single vs. multi-energy inferoseptal segment CT attenuation on myocardial fibrosis by both visually assessed LGE (absent/present fibrosis) and CMR T1 mapping-derived myocardial extracellular volume fraction (ECV).

RESULTS

The multi-energy CT/LDA approach performed better than a single energy approach to discriminate among LGE-CMR classes of present/absence myocardial fibrosis severity, demonstrating correct classification rates of 89% and 71%, respectively. The multi-energy CT/LDA approach also performed better in correctly discriminating normal from elevated ECV, doing so in 89% of patients vs. correct distinction of normal/elevated ECV in only 70% using the single energy approach.

CONCLUSIONS

Non-contrast cardiac DECT with multi-energy analysis better classifies myocardial fibrosis and extracellular volume compared to what is feasible with non-contrast single energy cardiac CT. These data support further evaluation of this approach to noninvasively assess myocardial fibrosis.

Noninvasive Cardiovascular Imaging: Emergence of a Powerful Tool for Early Identification of Cardiovascular Risk in People Living With HIV

Antiretroviral therapy (ART) has been pivotal in prolonging the lifespan of people living with HIV (PLWH). However, this also simultaneously increases their risk of cardiovascular disease (CVD) either related to ART, aging, hypertension, immunosenescence, inflammation, immune activation, or other comorbidities. Although the use of risk markers has greatly enhanced the field of cardiovascular (CV) medicine and improved the prognosis and early diagnosis in the general population, this strategy has not been clearly elucidated in PLWH. Developing accurate risk algorithms for PLWH requires an innate understanding of mechanistic factors influencing their risks. Early identification of CV risk will significantly enhance the prospects of PLWH living longer and relatively healthily. Herein, we discuss the use of multimodality noninvasive CV imaging as robust markers for ameliorating CV risk. The ability to prognosticate CV risk and hence prevent CV events in PLWH would represent an important advance in CV medicine, allowing precise detection and early institution of preventative strategies. Using novel CV imaging modalities and strategies would have a positive impact on precision medicine in this patient cohort.

Free-breathing, non-ECG, continuous myocardial T1 mapping with cardiovascular magnetic resonance multitasking

PURPOSE

To evaluate the accuracy and repeatability of a free-breathing, non-electrocardiogram (ECG), continuous myocardial T₁ and extracellular volume (ECV) mapping technique adapted from the Multitasking framework.

METHODS

The Multitasking framework is adapted to quantify both myocardial native T₁ and ECV with a free-breathing, non-ECG, continuous acquisition T₁ mapping method. We acquire interleaved high-spatial resolution image data and high-temporal resolution auxiliary data following inversion-recovery pulses at set intervals and perform low-rank tensor imaging to reconstruct images at 344 inversion times, 20 cardiac phases, and 6 respiratory phases. The accuracy and repeatability of Multitasking T₁ mapping in generating native T₁ and ECV maps are compared with conventional techniques in a phantom, a simulation, 12 healthy subjects, and 10 acute myocardial infarction patients.

RESULTS

In phantoms, Multitasking T₁ mapping correlated strongly with the gold-standard spin-echo inversion recovery (R² = 0.99). A simulation study demonstrated that Multitasking T₁ mapping has similar myocardial sharpness to the fully sampled ground truth. In vivo native T₁ and ECV values from Multitasking T₁ mapping agree well with conventional MOLLI values and show good repeatability for native T₁ and ECV mapping for 60 seconds, 30 seconds, or 15 seconds of data. Multitasking native T₁ and ECV in myocardial infarction patients correlate positively with values from MOLLI.

CONCLUSION

Multitasking T₁ mapping can quantify native T₁ and ECV in the myocardium with free-breathing, non-ECG, continuous scans with good image quality and good repeatability in vivo in healthy subjects, and correlation with MOLLI T₁ and ECV in acute myocardial infarction patients.

Real-time Triggered RAdial Single-Shot Inversion recovery for arrhythmia-insensitive myocardial T1 mapping: motion phantom validation and in vivo comparison

PURPOSE

Cardiac T₁ mapping has become an increasingly important imaging technique, contributing novel diagnostic options. However, currently utilized methods are often associated with accuracy problems because of heart rate variations and cardiac arrhythmia, limiting their value in clinical routine. This study aimed to introduce an improved arrhythmia-related robust T₁ mapping sequence called RT-TRASSI (real-time Triggered RAdial Single-Shot Inversion recovery).

METHODS

All measurements were performed on a 3.0T whole-body imaging system. A real-time feedback algorithm for arrhythmia detection was implemented into the previously described pulse sequence. A programmable motion phantom was constructed and measurements with different simulated arrhythmias arranged. T₁ mapping accuracy and susceptibility to artifacts were analyzed. In addition, in vivo measurements and comparisons with 3 prevailing T₁ mapping sequences (MOLLI, ShMOLLI, and SASHA) were carried out to investigate the occurrence of artifacts.

RESULTS

In the motion phantom measurements, RT-TRASSI showed excellent agreement with predetermined reference T₁ values. Percentage scattering of the T₁ values ranged from -0.6% to +1.9% in sinus rhythm and -1.0% to +3.1% for high-grade arrhythmias. In vivo, RT-TRASSI showed diagnostic image quality with only 6% of the acquired T₁ maps including image artifacts. In contrast, more than 40% of the T₁ maps acquired with MOLLI, ShMOLLI, or SASHA included motion artifacts.

CONCLUSION

Accuracy issues because of heart rate variability and arrhythmia are a prevailing problem in current cardiac T₁ mapping techniques. With RT-TRASSI, artifacts can be minimized because of the short acquisition time and effective real-time feedback, avoiding potential data acquisition during systolic heart phase.

Risk Stratification of Sudden Cardiac Death in Patients with Heart Failure: An update

Heart failure (HF) is a complex clinical syndrome in which structural/functional myocardial abnormalities result in symptoms and signs of hypoperfusion and/or pulmonary or systemic congestion at rest or during exercise. More than 80% of deaths in patients with HF recognize a cardiovascular cause, with most being either sudden cardiac death (SCD) or death caused by progressive pump failure. Risk stratification of SCD in patients with HF and preserved (HFpEF) or reduced ejection fraction (HFrEF) represents a clinical challenge. This review will give an update of current strategies for SCD risk stratification in both HFrEF and HFpEF.

Cardiac magnetic resonance T1 mapping. Part 2: Diagnostic potential and applications

Non-invasive identification and differentiation of myocardial diseases represents the primary objectives of cardiac magnetic resonance (CMR) longitudinal relaxation time (T1) and extracellular volume (ECV) mapping. Given the fact that myocardial T1 and ECV values overlap throughout and within left ventricular phenotypes, a central issue to be addressed is whether and to what extent myocardial T1 and ECV mapping provides additional or superior diagnostic information to standard CMR imaging, and whether native T1 mapping could be employed as a non-contrast alternative to late gadolinium enhancement (LE) imaging. The present review aims to summarize physiological and pathophysiological alterations in native T1 and ECV values and summarized myocardial T1 and ECV alterations associated with cardiac diseases to support the translation of research findings into routine CMR imaging.

Accurate and robust systolic myocardial T1 mapping using saturation recovery with individualized delay time: comparison with diastolic T1 mapping

T₁ mapping data are generally acquired in patients' diastolic phase, wherein their myocardium is the thinnest in the cardiac cycle. However, the analysis of the thin myocardium may cause errors in image registrations and settings related to the region of interest. In this study, we validated systolic T₁ mapping using the saturation recovery with individualized delay time (SR-IDT) method and compared it with conventional diastolic T₁ mapping. Both diastolic and systolic T₁ mappings were performed in the mid-ventricular plane in 10 healthy volunteers (35 ± 9 years, 9 males) and 29 consecutive patients with cardiac diseases (68 ± 14 years, 19 males). Comparison of the myocardial T₁ value at diastole and systole was performed with both the Pearson correlation coefficient (r) and the Bland-Altman analysis. Additionally, the systolic myocardial T₁ value was compared between the volunteers and patients by using Tukey's test. Pearson correlation analysis demonstrated a strong positive correlation between diastolic and systolic T₁ values (r = 0.88, P < 0.001). The Bland-Altman plot suggested that left ventricular T₁ values in the diastole and systole showed high agreement (mean difference and 95% limits of agreement = 17 ± 104 ms). Further, systolic T₁ values with SR-IDT in patients in the late gadolinium enhancement (LGE) group were significantly higher than those in the control group (1585 ± 118 ms vs 1469 ± 69 ms; P = 0.024). Therefore, the proposed systolic T₁ mapping with the SR-IDT, which was validated with respect to the conventional diastolic method, is a useful clinical tool for the quantitative characterization of the myocardium.

Myocardial extracellular volume quantified by magnetic resonance is increased in cirrhosis and related to poor outcome

BACKGROUND & AIMS

The underlying pathogenesis of cirrhotic cardiomyopathy remains unclear. Structural myocardial changes including diffuse fibrosis may be involved and can be accurately assessed by cardiac MRI (CMR) with quantification of the extracellular volume (ECV).This is the first application of this technique in patients with cirrhosis. We aimed to investigate the presence of diffuse myocardial fibrosis and to determine the relation to disease severity, cardiac function and outcome.

METHODS

A prospective study including 52 cirrhotic patients and 10 healthy controls. All patients underwent CMR with ECV quantification, tissue Doppler echocardiography, and biochemical assessments. Patients were followed up for a median of 25 months with registration of death and liver transplantation (LT).

RESULTS

Myocardial ECV was higher in the patients compared with healthy controls (31.2 ± 6 vs 27.4 ± 3%, P = .04). Furthermore, ECV increased across the Child Pugh A/B/C classes (26.9 ± 4/31.5 ± 5/34.4 ± 6%, P = .02). Four-teen patients experienced the composite end-point of death/LT during follow-up and these patients had higher ECV (33.2 ± 4 vs 30.4 ± 6%, P = .04). In a univariate Cox regression analysis ECV was associated with poor transplant-free survival (HR 3.6 [1.1-11.6]; P = .03). However, MELD and CRP remained the strongest predictors in a multivariate analysis. ECV correlated with cardiac index (r = 0.44, P = .001), CRP (r = 0.46, P = .001), proANP (r = 0.50, P < .001), and proBNP (r = 0.40, P = .005).

CONCLUSIONS

Myocardial ECV is increased in patients with cirrhosis and seems related to disease severity and transplant-free survival. These changes most likely reflect subclinical diffuse myocardial fibrosis and may represent a structural element of cirrhotic cardiomyopathy.

Histogram Analysis of Native T1 Mapping and Its Relationship to Left Ventricular Late Gadolinium Enhancement, Hypertrophy, and Segmental Myocardial Mechanics in Patients With Hypertrophic Cardiomyopathy

BACKGROUND

The use of native T₁ mapping for evaluation of hypertrophic cardiomyopathy (HCM) is being explored, and its combination with histogram analysis may benefit the accuracy of such assessments.

PURPOSE

To investigate the relationship of segmental left ventricular wall thickness (LVWT), myocardial fibrosis, and strain parameters with segmental histogram parameters of native T₁ mapping in HCM patients.

STUDY TYPE

Retrospective.

SUBJECTS

Ninety-three HCM patients without previous cardiovascular diseases were included.

FIELD STRENGTH/SEQUENCE

3.0T cardiac MR. Steady-state free precession cine imaging, modified Look-Locker inversion recovery, phase-sensitive inversion recovery.

ASSESSMENT

Images were assessed by three experienced radiologists.

STATISTICAL TESTS

Mann-Whitney U-tests, area under the curve (AUC), Spearman's rank correlation, intraclass correlation coefficient, and Bland-Altman test were used for statistical analysis.

RESULTS

A higher LVWT value correlated with higher means, minimums, 10^th /25^th /50^th /75^th /90^th percentiles, maximums, kurtosis, entropy, and lower SD and energy of T₁ mapping (P < 0.05 for all), with the correlation being stronger for entropy and energy (Spearman's rho = 0.439 and -0.413, respectively) than other parameters. Late gadolinium enhancement positive (LGE+) segments exhibited higher mean, minimum, 10^th /25^th /50^th /75^th /90^th percentiles, maximum, entropy, and lower energy of T₁ times than late gadolinium enhancement negative (LGE-) segments (P < 0.001 for all). Impaired strain function parameters (peak thickening and thickening rate in radial, circumferential, and longitudinal directions) demonstrated a weak correlation with higher entropy (P < 0.001 for all) and lower energy (P < 0.001 for all).

DATA CONCLUSION

Histogram parameters of native T₁ mapping provide more information than mean T₁ times alone. Among these parameters, entropy and energy may correlate better with LVWT, myocardial late gadolinium enhancement, and strain parameters than mean T₁ times in HCM patients.

LEVEL OF EVIDENCE

2 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;49:668-677.

Clinical application and technical considerations of T1 & T2(*) mapping in cardiac, liver, and renal imaging

Pathological tissue alterations due to disease processes such as fibrosis, edema and infiltrative disease can be non-invasively visualized and quantified by MRI using T₁ and T₂ relaxation properties. Pixel-wise mapping of T₁ and T₂ image sequences enable direct quantification of T₁, T₂(*), and extracellular volume values of the target organ of interest. Tissue characterization based on T₁ and T₂(*) mapping is currently making the transition from a research tool to a clinical modality, as clinical usefulness has been established for several diseases such as myocarditis, amyloidosis, Anderson-Fabry and iron deposition. Other potential clinical applications besides the heart include, quantification of steatosis, cirrhosis, hepatic siderosis and renal fibrosis. Here, we provide an overview of potential clinical applications of T₁ andT₂(*) mapping for imaging of cardiac, liver and renal disease. Furthermore, we give an overview of important technical considerations necessary for clinical implementation of quantitative parametric imaging, involving data acquisition, data analysis, quality assessment, and interpretation. In order to achieve clinical implementation of these techniques, standardization of T₁ and T₂(*) mapping methodology and validation of impact on clinical decision making is needed.

Detection of Recent Myocardial Infarction Using Native T1 Mapping in a Swine Model: A Validation Study

Late gadolinium enhancement (LGE) imaging is the currently the gold standard for in-vivo detection of myocardial infarction. However, gadolinium contrast administration is contraindicated in patients with renal insufficiency. We aim to evaluate the diagnostic sensitivity and specificity of this contrast-free MRI technique, native T1 mapping, in detecting recent myocardial infarction versus a reference histological gold standard. Ten pigs underwent CMR at 2 weeks after induced MI. The infarct size and transmural extent of MI was calculated using native T1 maps and LGE images. Histological validation was performed using triphenyl tetrazolium chloride (TTC) staining in the corresponding ex-vivo slices. The infarct size and transmural extent of myocardial infarction assessed by T1 mapping correlated well with that assessed by LGE and TTC images. Using TTC staining as the reference, T1 mapping demonstrated underestimation of infarct size and transmural extent of infarction. Additionally, there was a slight but not significant difference found in the diagnostic performance between the native T1 maps and LGE images for the location of MI. Our study shows that native T1 mapping is feasible alternative method to the LGE technique for the assessment of the size, transmural extent, and location of MI in patients who cannot receive gadolinium contrast.

Iron overload cardiomyopathy: from diagnosis to management

PURPOSE OF REVIEW

Iron overload cardiomyopathy (IOC) is an important predictor of prognosis in a significant number of patients with hereditary hemochromatosis and hematologic diseases. Its prevalence is increasing because of improved treatment strategies, which significantly improve life expectancy. We will review diagnosis, treatment, and recent findings in the field.

RECENT FINDINGS

The development of preclinical translational disease models during the last years have helped our understanding of specific disease pathophysiological pathways that might eventually change the outcomes of these patients.

SUMMARY

IOC is an overlooked disease because of the progressive silent disease pattern and the lack of physicians' expertise. It mainly affects patients with hemochromatosis and hematologic diseases and its prevalence is expected to increase with the improvement in life expectancy of hematologic disorders. Early diagnosis of IOC in patients at risk by means of biochemical parameters and cardiac imaging can lead to early treatment and improved prognosis. The mainstay of treatment of IOC is conventional heart failure treatment, combined with phlebotomies or iron chelation in the context of anemia. The development of preclinical models has provided a comprehensive look into specific pathophysiological pathways with potential treatment strategies that must be sustained by future randomized trials.

T2 , T1ρ and TRAFF4 detect early regenerative changes in mouse ischemic skeletal muscle

The identification of areas with regenerative potential in ischemic tissues would allow the targeting of treatments supporting tissue recovery. The regeneration process involves the activation of several cellular and molecular responses which could be detected using magnetic resonance imaging (MRI). However, to date, magnetic resonance (MR) relaxation parameters have received little attention in the diagnosis and follow-up of limb ischemia. The purpose of this study was to evaluate the feasibility of different MRI relaxation and diffusion tensor imaging parameters in the detection of areas showing early signs of regeneration in ischemic mouse skeletal muscles. T₂ and T_1ρ relaxation time constants, together with T_RAFFn , T₁ and diffusion tensor imaging, were evaluated to differentiate areas of regeneration in a mouse hind limb ischemia model before and 0, 1, 4, 7, 14 and 30 days after ischemia. All the measured relaxation times were longer in the areas of early regeneration compared with normal muscle tissue. The relaxation times increased after ischemia in the ischemic muscles, reaching a maximum at 4-7 days after occlusion, coinciding with the appearance of early signs of regeneration. Fractional anisotropy decreased significantly (p < 0.05) on days 1-4, whereas mean diffusivity, λ₁ and λ₂ decreased later, starting at day 7 after ischemia compared with the pre-operational time point. The percentages of areas with different tissue morphologies were determined based on histological analysis of the ischemic muscle cross-sections, and correlations between the percentages obtained and different relaxation times were calculated. The highest correlation between relaxation times and histology was achieved with T₂ , T_1ρ and T_RAFF4 (R² = 0.96, R² = 0.92 and R² = 0.84, respectively, p < 0.01)_. Early regenerative changes were visible using T₂ , T_1ρ and T_RAFF4 MR relaxation time constants in skeletal muscle after ischemia. These markers could potentially be used for the identification of targets for therapies supporting muscle regeneration after ischemic injury.

Three-dimensional Cardiomyocytes Structure Revealed By Diffusion Tensor Imaging and Its Validation Using a Tissue-Clearing Technique

We characterized the microstructural response of the myocardium to cardiovascular disease using diffusion tensor imaging (DTI) and performed histological validation by intact, un-sectioned, three-dimensional (3D) histology using a tissue-clearing technique. The approach was validated in normal (n = 7) and ischemic (n = 8) heart failure model mice. Whole heart fiber tracking using DTI in fixed ex-vivo mouse hearts was performed, and the hearts were processed with the tissue-clearing technique. Cardiomyocytes orientation was quantified on both DTI and 3D histology. Helix angle (HA) and global HA transmurality (HAT) were calculated, and the DTI findings were confirmed with 3D histology. Global HAT was significantly reduced in the ischemic group (DTI: 0.79 ± 0.13°/% transmural depth [TD] and 3D histology: 0.84 ± 0.26°/%TD) compared with controls (DTI: 1.31 ± 0.20°/%TD and 3D histology: 1.36 ± 0.27°/%TD, all p < 0.001). On direct comparison of DTI with 3D histology for the quantitative assessment of cardiomyocytes orientation, significant correlations were observed in both per-sample (R2 = 0.803) and per-segment analyses (R2 = 0.872). We demonstrated the capability and accuracy of DTI for mapping cardiomyocytes orientation by comparison with the intact 3D histology acquired by tissue-clearing technique. DTI is a promising tool for the noninvasive characterization of cardiomyocytes architecture.

Diastolic Dysfunction in Individuals With Human Immunodeficiency Virus Infection: Literature Review, Rationale and Design of the Characterizing Heart Function on Antiretroviral Therapy (CHART) Study

Antiretroviral therapy (ART) has been associated with a shift in the epidemiology of human immunodeficiency virus (HIV)-associated cardiomyopathy from a phenotype of primarily left ventricular (LV) systolic dysfunction to LV diastolic dysfunction (DD). Patients with HIV receiving ART have higher rates of DD compared with age-matched control subjects and develop DD at a younger age. However, little is known about the natural history and pathogenesis of DD in virally suppressed HIV-infected patients. Current evidence suggests that immune processes modulate the risk for cardiac involvement in HIV-infected persons. Ongoing inflammation appears to have myocardial effects, and accelerated myocardial fibrosis appears to be a key mediator of HIV-induced DD. The Characterizing Heart Function on Antiretroviral Therapy (CHART) study aims to systematically investigate determinants, mechanisms, and consequences of DD in HIV-infected patients. We will compare ART-treated virally suppressed HIV-infected individuals with and without DD and HIV- individuals with DD regarding (1) systemic inflammation, myocardial stress, and subclinical myocardial necrosis as indicated by circulating biomarkers; (2) immune system activation as indicated by cell surface receptors; (3) myocardial fibrosis according to cardiac magnetic resonance examination; (4) markers of fibrosis and remodeling, oxidative stress, and hypercoagulability; (5) left atrial function according to echocardiographic examination; (6) myocardial stress and subclinical necrosis as indicated by circulating biomarkers; (7) proteomic and metabolic profiles; and (8) phenotype signatures derived from clinical, biomarker, and imaging data.