Cardiac MRI T2* in Liver Transplant Candidates: Application and Performance of a Novel Imaging Technique to Identify Patients at Risk for Poor Posttransplant Cardiac Outcomes.

BACKGROUND: In end-stage liver disease, alterations in iron metabolism can lead to iron overload and development of iron overload cardiomyopathy. In liver transplant candidates, evaluation for cardiac iron overload and dysfunction can help to identify candidates at increased risk for peritransplant morbidity and mortality, though recommendations for pretransplant evaluation of cardiac iron overload are not standardized. Cardiac Magnetic Resonance Imaging T2* (CMRI-T2*) is a validated method to quantify cardiac iron deposition, with normal T2* value of 20 ms or greater. In this study, we sought to identify the incidence and predictors of iron overload by CMRI-T2* and to evaluate the impact of cardiac and iron overload on morbidity and mortality after liver transplantation. METHODS: In this retrospective single-center cohort study, all liver transplant candidates who underwent a pretransplant CMRI-T2* between January 1, 2008, and June 30, 2016, were included to analyze the association between clinical characteristics and low T2* using logistic regression. RESULTS: One hundred seventy-nine liver transplant candidates who received CMRI-T2* were included. Median age was 57 years, 73.2% were male, and 47.6% were white. 49.7% had hepatitis C and 2.8% had hemochromatosis. Median Model for End-Stage Liver Disease score was 25. 65.2% were Child-Pugh C. In multivariable logistic regression, T2* less than 20 ms (n = 35) was associated with Model for End-Stage Liver Disease score of 25 or greater (odds ratio [OR], 3.65; P = 0.007), Child-Pugh C (OR, 3.42; P = 0.03), and echocardiographic systolic ejection fraction less than 65% (OR, 2.24; P = 0.01). Posttransplant heart failure occurred exclusively in recipients with T2* less than 15 ms. Survival was worse in T2* 10 to 14.9 versus T2* of 20 ms or greater (hazard ratio, 3.85; P = 0.003), but not for 15 to 19.9 versus T2* of 20 ms or greater. CONCLUSIONS: Severity of liver disease and systolic dysfunction is associated with T2* less than 20 ms, though there was no difference in posttransplant outcomes between T2* 15 to 19.9 and T2* 20 ms or greater, suggesting that individuals with T2* of 15 ms or greater may be suitable transplant candidates. CMRI-T2* is an additional diagnostic tool in evaluating transplant candidates at high risk for posttransplant cardiac complications.

Cardiac Magnetic Resonance Evaluation of Left Ventricular Myocardial Strain in Pulmonary Hypertension.

RATIONALE AND OBJECTIVES: We investigated the feasibility of detecting left ventricular (LV) cardiac magnetic resonance (CMR) strain abnormalities using feature-tracking in patients with pulmonary hypertension (PH). MATERIALS AND METHODS: CMR was performed in 16 patients with all groups of PH and in 13 controls. Global and regional peak circumferential strains (%) (which have been shown to be robust by CMR), peak diastolic strain rate (%/s), and dyssynchrony index (ms) were quantified with feature-tracking software. Ventricular function and volumes were calculated from CMR, and right heart pressures were measured with catheterization. RESULTS: Left ventricular ejection fraction (LVEF) was similar in patients (60.2% ± 11.0%) and controls (61.9% ± 4.5%), P = .150. Global LV peak circumferential strain was significantly different in patients compared to controls, -16.7 ± 2.8% vs -19.9 ± 1.8%, respectively (P = .001). The greatest difference in strain was seen in the LV septum, -11.6 ± 4.3% in patients vs -16.7 ± 4.0% in controls (P < .001). There was a significant association between septal strain and right ventricular end-diastolic volume index (P = .047) in patients with PH; however, there were no associations with pulmonary artery pressures or right ventricular ejection fraction. CONCLUSIONS: Feature-tracking CMR can detect LV strain abnormalities in patients with PH and preserved or mildly depressed LVEF, with greatest abnormality in the septum. The association between septal strain and right ventricular end-diastolic volume index suggests that ventricular interdependence may be a mechanism of LV dysfunction in PH. Feature-tracking CMR may be useful for identification of LV dysfunction before LVEF significantly declines in patients with PH. The feasibility of detecting LV strain abnormalities in patients with PH shown by this study paves the way for a variety of future investigations into the applications of LV strain in this patient population.

Highly-accelerated self-gated free-breathing 3D cardiac cine MRI: validation in assessment of left ventricular function.

OBJECTIVE: This work presents a highly-accelerated, self-gated, free-breathing 3D cardiac cine MRI method for cardiac function assessment. MATERIALS AND METHODS: A golden-ratio profile based variable-density, pseudo-random, Cartesian undersampling scheme was implemented for continuous 3D data acquisition. Respiratory self-gating was achieved by deriving motion signal from the acquired MRI data. A multi-coil compressed sensing technique was employed to reconstruct 4D images (3D+time). 3D cardiac cine imaging with self-gating was compared to bellows gating and the clinical standard breath-held 2D cine imaging for evaluation of self-gating accuracy, image quality, and cardiac function in eight volunteers. Reproducibility of 3D imaging was assessed. RESULTS: Self-gated 3D imaging provided an image quality score of 3.4 ± 0.7 vs 4.0 ± 0 with the 2D method (p = 0.06). It determined left ventricular end-systolic volume as 42.4 ± 11.5 mL, end-diastolic volume as 111.1 ± 24.7 mL, and ejection fraction as 62.0 ± 3.1%, which were comparable to the 2D method, with bias ± 1.96 × SD of -0.8 ± 7.5 mL (p = 0.90), 2.6 ± 3.3 mL (p = 0.84) and 1.4 ± 6.4% (p = 0.45), respectively. CONCLUSION: The proposed 3D cardiac cine imaging method enables reliable respiratory self-gating performance with good reproducibility, and provides comparable image quality and functional measurements to 2D imaging, suggesting that self-gated, free-breathing 3D cardiac cine MRI framework is promising for improved patient comfort and cardiac MRI scan efficiency.

Predicting Persistent Left Ventricular Dysfunction Following Myocardial Infarction: The PREDICTS Study.

BACKGROUND: Persistent severe left ventricular (LV) systolic dysfunction after myocardial infarction (MI) is associated with increased mortality and is a class I indication for implantation of a cardioverter-defibrillator. OBJECTIVES: This study developed models and assessed independent predictors of LV recovery to >35% and ≥50% after 90-day follow-up in patients presenting with acute MI and severe LV dysfunction. METHODS: Our multicenter prospective observational study enrolled participants with ejection fraction (EF) of ≤35% at the time of MI (n = 231). Predictors for EF recovery to >35% and ≥50% were identified after multivariate modeling and validated in a separate cohort (n = 236). RESULTS: In the PREDICTS (PREDiction of ICd Treatment Study) study, 43% of patients had persistent EF ≤35%, 31% had an EF of 36% to 49%, and 26% had an EF ≥50%. The model that best predicted recovery of EF to >35% included EF at presentation, length of stay, prior MI, lateral wall motion abnormality at presentation, and peak troponin. The model that best predicted recovery of EF to ≥50% included EF at presentation, peak troponin, prior MI, and presentation with ventricular fibrillation or cardiac arrest. After predictors were transformed into point scores, the lowest point scores predicted a 9% and 4% probability of EF recovery to >35% and ≥50%, respectively, whereas profiles with the highest point scores predicted an 87% and 49% probability of EF recovery to >35% and ≥50%, respectively. CONCLUSIONS: In patients with severe systolic dysfunction following acute MI with an EF ≤35%, 57% had EF recovery to >35%. A model using clinical variables present at the time of MI can help predict EF recovery.

Accuracy and Usability of a Self-Administered 6-Minute Walk Test Smartphone Application.

BACKGROUND: The 6-minute walk test (6MWT) independently predicts congestive heart failure severity, death, and heart failure hospitalizations, but must be administered in clinic by qualified staff on a premeasured course. As part of the Health eHeart Study, we sought to develop and validate a self-administered 6MWT mobile application (SA-6MWTapp) for independent use at home by patients. METHODS AND RESULTS: We performed a validation study of an SA-6MWTapp in 103 participants. In phase 1 (n=52), we developed a distance-estimation algorithm for the SA-6MWTapp by comparing step counts from an Actigraph and measured distance on a premeasured 6MWT course with step counts and estimated distance obtained simultaneously from our SA-6MWTapp (best estimation algorithm, r=0.89 [95% confidence interval 0.78-0.99]). In phase 2, 32 participants (including those with congestive heart failure and pulmonary hypertension) used the SA-6MWTapp independently in clinic, and the distance estimated by the SA-6MWTapp was compared with the measured distance (r=0.83 [95% confidence interval 0.79-0.92]). In phase 3, 19 patients with congestive heart failure and pulmonary hypertension consecutively enrolled from clinic performed 3.2±1 SA-6MWTapp tests per week at home over 2 weeks. Distances estimated from the SA-6MWTapp during home 6MWTs were highly repeatable (coefficient of variation =4.6%) and correlated with in-clinic-measured distance (r=0.88 [95% confidence interval 0.87-0.89]). Usability surveys performed during the second (in-clinic) and third (at-home) phases demonstrated that the SA-6MWTapp was simple and easy to use independently. CONCLUSIONS: An SA-6MWTapp is easy to use and yields accurate repeatable measurements in the clinic and at home.

Relation of C-reactive protein to abdominal adiposity.

Inflammation is a crucial element in the development of cardiovascular disease. Serum measurements of inflammation through high-sensitivity C-reactive protein (hsCRP) can lead to improved risk stratification of patients for risk for hard cardiovascular events. There is evidence that anthropomorphic measurements of obesity are important determinants of systemic inflammation. Online databases (e.g., PubMed and Medline) were searched for original research reports published in English from June 1990 to June 2009 examining the relations between hsCRP; anthropomorphic measurements of obesity including body mass index, waist-to-hip ratio, waist circumference, and visceral adiposity; and cardiovascular disease. When possible, correlation coefficients were used to compare data among studies. Measurements of abdominal obesity are associated with systemic inflammation as measured by hsCRP (r = 0.40 to 0.61). The association between hsCRP and abdominal adiposity persists when taking into account body mass index. Elevation of hsCRP might be reversible with weight loss and exercise. In conclusion, clinical measurements of abdominal adiposity readily provide data elucidating the systemic inflammatory state of patients and can help guide intensity of lifestyle modifications, thus leading to reduction of this inflammation.