Serial cardiovascular magnetic resonance feature tracking indicates early worsening of cardiac function in Fontan patients

The utility of novel STE parameters in echocardiographic assessment of single ventricle after Fontan palliation

Background and aims of the study A functionally single ventricle (FSV) refers to a group of congenital heart defects that are not amenable for biventricular correction. The Fontan operation is utilized as surgical treatment for most of FSV patients. The evaluation of FSV function is extremely difficult due to its unique pathophysiology. This study aimed to explore the efficacy of speckle tracking echocardiography (STE) parameters measured at rest and during exercise for comprehensive assessment of univentricular heart.

METHODS

We enrolled 37 patients with a functionally single ventricle after the Fontan operation, hospitalized in the Department of Congenital Heart Defects between years 2019 and 2021.The echocardiographic stress tests were performed in the Echocardiography Laboratory of the Congenital Heart Defects Department. The study was conducted on a bicycle ergometer in a semi-recumbent position. The parameters obtained by speckle tracking echocardiography (STE): the longitudinal strain of the FSV free wall (Ɛ) and the longitudinal strain of myocardial layers: subendocardial, medial and subepicardial were analyzed. A transmural longitudinal strain gradient (TG) was calculated as the difference between longitudinal deformation of the subendocardial and subepicardial layers. Current results of cardiac magnetic resonance imaging (CMR) and cardio-pulmonary test (CPET) were also incorporated. Demographic data, past interventions, pharmacological treatment and comorbidities were extracted from medical records.

RESULTS

Ɛ at rest and during exercise were not related to the parameters of physical capacity obtained on CPET nor to the CMR results. The transmural strain gradient was dependent on physical performance parameter- peak oxygen uptake- and related to the FSV ejection fraction calculated by magnetic resonance imaging.

CONCLUSIONS

The transmural strain gradient and FSV free wall strain are readily measurable and suitable for evaluating single ventricle function. The TG is positively correlated with peak oxygen uptake during the cardiopulmonary test and with the ejection fraction derived from cardiac magnetic resonance imaging. The applicability of these findings in patients undergoing the Fontan procedure warrants further exploration.

Wall motion assessment by feature tracking in pediatric patients with coronary anomalies undergoing dobutamine stress CMR

Background

Left ventricular (LV) wall motion assessment is an important adjunct in addition to perfusion defects in assessing ischemic changes. This study aims to investigate the feasibility and utility of performing feature tracking (FT) in pediatric patients with coronary anomalies undergoing dobutamine stress CMR to assess wall motion abnormalities (WMA) and perfusion defects.

Method

This is a retrospective study where 10 patients with an inducible first-pass perfusion (FPP) defect and 10 without were selected. Global LV circumferential strain/strain rate (GCS/GCSR) was measured at rest and at peak stress (systole and diastole) using a commercially available feature tracking software. Peak GCS and GCSR were compared to indexed wall motion score (WMSI) between groups with and without FPP defect and in subjects with and without WMA.

Results

The median age of patients was 13.5 years (Q1, 11 years; Q3, 15 years). Five subjects had qualitatively WMA at peak stress. A moderate correlation of GCS with WMSI at peak stress (0.48, p = 0.026) and a significant difference between GCS at rest and stress in patients with no inducible WMA (p = 0.007) were seen. No significant difference was noted in GCS between rest and stress in patients with WMA (p = 0.13). There was a larger absolute GCS/GCSR at peak stress in subjects with no inducible FPP defect or WMA.

Conclusion

Smaller absolute GCS and a lack of significant change in GCS at peak stress in those with inducible WMA or perfusion defect are suggestive of compromised LV deformation in subjects with inducible WMA. Given these findings, GCS derived from CMR-FT may be used to objectively assess WMA in pediatric patients undergoing stress CMR.

Cardiac output drop reflects circulatory attrition after Fontan completion: serial cardiac magnetic resonance study

Aims

Cardiac magnetic resonance (CMR) imaging is a main diagnostic tool in the follow-up of Fontan patients. However, the value of serial CMR for the evaluation of Fontan attrition is unknown. The aim of this prospective study of serial CMR is to describe the analysis of time-dependent evolution of blood flow distribution, ventricular volumes, and function in patients after Fontan completion.

Methods and results

In this prospective single-centre study, between 2012 and 2022, 281 CMR examinations were performed in 88 Fontan patients with distribution of blood flows, measurements of ventricular volumes, and ejection fraction. Linear mixed model regression for repeated measurements was used to analyse changes of measurements across serial CMR examinations. During a time interval of 10 years, the median number of CMR per patient was 3 (range 1-5). Indexed flow of ascending aorta, caval veins, and pulmonary arteries decreased significantly across serial CMR examinations. Although a decrease of mean indexed aortic flow (3.03 ± 0.10 L/min/m2 at first CMR vs. 2.36 ± 0.14 L/min/m2 at fourth CMR, P < 0.001) was observed, ejection fraction did not decline (50 ± 1% at first CMR vs. 54 ± 2% at fourth CMR, P = 0.070). Indexed ventricular volumes did not differ significantly across serial CMR examinations.

Conclusion

The decrease of indexed aortic and cavopulmonary flows reflects the attrition of univentricular circulation and can be detected by means of serial CMR. Ventricular systolic dysfunction does not contribute significantly to this attrition. In order to detect significant change of indexed aortic flow, we recommend performing serial CMR as routine practice in the Fontan population.

Myocardial strain-curve deformation patterns after Fontan operation

Myocardial deformation analysis by cardiac MRI (CMR) yielding global circumferential and longitudinal strain (GCS and GLS) is an increasingly utilized method to accurately quantify systolic function and predict clinical events in patients with Fontan circulation. The purpose of this study was to use principal component analysis (PCA) to investigate myocardial temporal deformation patterns derived from strain-time curves to learn about latent strain features beyond peak values. We conducted the study with specific attention to dominant single left or right ventricle (SLV and SRV) morphologies. Methods and Results: Patients remote from Fontan operation who underwent follow-up CMR were analyzed for standard volumetric and function hemodynamics including myocardial deformation parameters including GCS and GLS. We applied PCA to investigate in an unbiased fashion the strain-time curve morphology and to calculate patient specific shape scores. All variables were subjected to single variable Cox regression analysis to detect composite clinical outcome including death, heart transplant, protein losing enteropathy and plastic bronchitis. A total of 122 patients, (SLV = 67, SRV = 55) with a mean age of 12.7 years underwent comprehensive CMR analysis. The PCA revealed 3 primary modes of strain-curve variation regardless of single ventricle morphology and type of strain investigated. Principle components (PCs) described changes in (1) strain-time curve amplitude, (2) time-to-peak strain, and (3) post-systolic slope of the strain-time curve. Considering only SLV patients, GCS was only CMR variable predictive of clinical events (HR 1.46, p = 0.020). In the SRV group, significant CMR predictors of clinical events were derived indexed end-diastolic (HR 1.02, p = 0.023) and end-systolic (HR 1.03, p = 0.022) volumes, GCS (HR 1.91, p = 0.003) and its related first component score (HR 1.20, p = 0.005), GLS (HR 1.32, p = 0.029) and its third component score (HR 1.58, p = 0.017). CMR derived global strain measures are sensitive markers of clinical outcomes in patients with Fontan circulation, particularly in patients with the SRV morphology. Myocardial strain-time curve morphology specific to SLV and SRV patients inspired by unbiased PCA technique can further aid with predicting clinical outcomes.

Opportunities and short-comings of the axolotl salamander heart as a model system of human single ventricle and excessive trabeculation

Few experimental model systems are available for the rare congenital heart diseases of double inlet left ventricle (DILV), a subgroup of univentricular hearts, and excessive trabeculation (ET), or noncompaction. Here, we explore the heart of the axolotl salamander (Ambystoma mexicanum, Shaw 1789) as model system of these diseases. Using micro-echocardiography, we assessed the form and function of the heart of the axolotl, an amphibian, and compared this to human DILV (n = 3). The main finding was that both in the axolotl and DILV, blood flows of disparate oxygen saturation can stay separated in a single ventricle. In the axolotl there is a solitary ventricular inlet and outlet, whereas in DILV there are two separate inlets and outlets. Axolotls had a lower resting heart rate compared to DILV (22 vs. 72 beats per minute), lower ejection fraction (47 vs. 58%), and their oxygen consumption at rest was higher than peak oxygen consumption in DILV (30 vs. 17 ml min^-1 kg^-1). Concerning the ventricular myocardial organization, histology showed trabeculations in ET (n = 5) are much closer to the normal human setting than to the axolotl setting. We conclude that the axolotl heart resembles some aspects of DILV and ET albeit substantial species differences exist.

Serial Assessment of Right Ventricular Deformation in Patients With Hypoplastic Left Heart Syndrome: A Cardiovascular Magnetic Resonance Feature Tracking Study

Background As right ventricular dysfunction is a major cause of adverse outcome in patients with hypoplastic left heart syndrome, the aim was to assess right ventricular function and deformation after Fontan completion by performing 2-dimensional cardiovascular magnetic resonance feature tracking in serial cardiovascular magnetic resonance studies. Methods and Results Cardiovascular magnetic resonance examinations of 108 patients with hypoplastic left heart syndrome (female: 31) were analyzed. Short-axis cine images were used for right ventricular volumetry. Two-dimensional cardiovascular magnetic resonance feature tracking was performed using long-axis and short-axis cine images to measure myocardial global longitudinal, circumferential, and radial strain. All patients had at least 2 cardiovascular magnetic resonance examinations after Fontan completion and 41 patients had 3 examinations. Global strain values and right ventricular ejection fraction decreased from the first to the third examination with a significant decline in global longitudinal strain from the first examination to the second examination (median, first, and third quartile: -18.8%, [-20.5;-16.5] versus -16.9%, [-19.3;-14.7]) and from the first to the third examination in 41 patients (-18.6%, [-20.9;-15.7] versus -15.8%, [-18.7;-12.6]; P-values <0.004). Right ventricular ejection fraction decreased significantly from the first to the third examination (55.4%, [49.8;59.3] versus 50.2%, [45.0;55.9]; P<0.002) and from the second to the third examination (53.8%, [47.2;58.7] versus 50.2%, [45.0;55.9]; P<0.0002). Conclusions Serial assessment of cardiovascular magnetic resonance studies in patients with hypoplastic left heart syndrome after Fontan completion demonstrates a significant reduction in global strain values and right ventricular ejection fraction at follow-up. The significant reduction in global longitudinal strain between the first 2 examinations with non-significant changes in right ventricular ejection fraction suggest that global longitudinal strain measured by 2-dimensional cardiovascular magnetic resonance feature tracking might be a superior technique for the detection of changes in myocardial function.

Role of cardiac magnetic resonance strain analysis in patients with hypoplastic left heart syndrome in evaluating right ventricular (dys)function: a systematic review

OBJECTIVES

Right ventricular dysfunction predicts death in patients with hypoplastic left heart syndrome (HLHS), but differences in morphology and loading conditions make calculation of the ejection fraction (EF), a challenging measure of its function. Our goal was to evaluate how strain measurements with cardiac magnetic resonance feature tracking could be used to evaluate right ventricular function in patients with HLHS.

METHODS

A systematic search of the literature was performed by 2 independent researchers using the terms 'population', 'intervention', 'comparison', 'outcome' and 'time criteria'. PubMed and the Ovid database were searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

Our review included 8 studies with 608 participants with ventricular strain values obtained using cardiac magnetic resonance feature tracking. After stage I palliation, global strain was reduced in patients after a hybrid procedure and a right ventricle-to-pulmonary artery conduit compared with a modified Blalock-Taussig shunt despite similar EFs. Global longitudinal strain did not differ between stage II and stage III (Fontan) palliation. Fontan patients had significantly impaired global longitudinal and circumferential strain compared to the left ventricular strain of the controls. Studies of Fontan patients that included patients with HLHS who were part of a cohort with a single right ventricle showed impaired global circumferential strain compared with the cohort with a single left ventricle, with controls, and over time. In this group, impaired global circumferential strain was associated with major adverse cardiac events.

CONCLUSIONS

Cardiac magnetic resonance feature tracking can be used in patients with HLHS to evaluate RV strain and demonstrate differences between surgical strategies, over time and compared with controls. It could be used alongside clinical symptoms and EF values to detect ventricular dysfunction.

Quantification of Myocardial Deformation Applying CMR-Feature-Tracking-All About the Left Ventricle?

Purpose of Review

Cardiac magnetic resonance-feature-tracking (CMR-FT)-based deformation analyses are key tools of cardiovascular imaging and applications in heart failure (HF) diagnostics are expanding. In this review, we outline the current range of application with diagnostic and prognostic implications and provide perspectives on future trends of this technique.

Recent Findings

By applying CMR-FT in different cardiovascular diseases, increasing evidence proves CMR-FT-derived parameters as powerful diagnostic and prognostic imaging biomarkers within the HF continuum partly outperforming traditional clinical values like left ventricular ejection fraction. Importantly, HF diagnostics and deformation analyses by CMR-FT are feasible far beyond sole left ventricular performance evaluation underlining the holistic nature and accuracy of this imaging approach.

Summary

As an established and continuously evolving technique with strong prognostic implications, CMR-FT deformation analyses enable comprehensive cardiac performance quantification of all cardiac chambers.

Integrated Clinical and Magnetic Resonance Imaging Assessments Late After Fontan Operation

BACKGROUND

Several clinical and cardiac magnetic resonance (CMR)-derived parameters have been shown to be associated with death or heart transplant late after the Fontan operation.

OBJECTIVES

The objective of this study was to identify the relative importance and interactions of clinical and CMR-based parameters for risk stratification after the Fontan operation.

METHODS

Fontan patients were retrospectively reviewed. Clinical and CMR parameters were analyzed using univariable Cox regression. The primary endpoint was time to death or (listing for) heart transplant. To identify the patients at highest risk for the endpoint, classification and regression tree survival analysis was performed, including all significant variables from Cox regression.

RESULTS

The cohort consisted of 416 patients (62% male) with a median age of 16 years (25th, 75th percentiles: 11, 23 years). Over a median follow-up of 5.4 years (25th, 75th percentiles: 2.4, 10.0 years) after CMR, 57 patients (14%) reached the endpoint (46 deaths, 7 heart transplants, 4 heart transplant listings). Lower total indexed end-diastolic volume (EDV_i) was the strongest predictor of transplant-free survival. Among patients with dilated ventricles (EDV_i ≥156 ml/BSA^1.3), worse global circumferential strain (GCS) was the next most important predictor (73% vs. 44%). In patients with smaller ventricles (EDV_i <156 ml/BSA^1.3), New York Heart Association functional class ≥II was the next most important predictor (30% vs. 4%).

CONCLUSIONS

In this cohort of patients late after Fontan operation, increased ventricular dilation was the strongest independent predictor of death or transplant (listing). Patients with both ventricular dilation and worse GCS were at highest risk. These data highlight the value of integrating CMR and clinical parameters for risk stratification in this population.

Myocardial Fibrosis in Pediatric Patients With Ebstein's Anomaly

BACKGROUND

Left ventricular dysfunction in Ebstein's anomaly (EA) is associated with higher mortality. The health of the left ventricular myocardium in children and adolescents with EA has not been investigated in detail.

METHODS

Patients with unrepaired EA who had undergone cardiac magnetic resonance imaging including T1 mapping were retrospectively reviewed. Patients were compared with age- and sex-matched controls. EA severity index was calculated using volumetric measurements at end diastole ([right atrial+atrialized right ventricular volumes]/[functional right ventricular+left atrial+left ventricular volumes]). Global circumferential and radial strain and as well as strain rate were examined using cardiac magnetic resonance feature tracking.

RESULTS

Twelve EA patients and an equal number of controls were included. Functional and atrialized right ventricular end-diastolic volumes were 84±15 and 21±13 mL/m², respectively. Late gadolinium enhancement, confined to the right ventricle, was found in 2 patients (16%). Left ventricular native T1 values and extracellular volume fractions were higher in patients compared with controls (1026±47 versus 956±40 ms, P=0.0004 and 28.5±3.4% versus 22.5±2.6%, P<0.001, respectively). Native T1 times correlated inversely with patients' age, body surface area, and O₂ saturations (r=-0.63, -0.62, and -0.91, respectively; P=0.02, P=0.02, and P<0.0001, respectively). EA severity index ranged between 0.15 and 0.94 and correlated with T1 values (r=0.76, P=0.003). Native T1 correlated with global circumferential strain (r=0.58, P=0.04) but not ejection fraction (EF). EA patients had reduced maximum oxygen uptake (Vo₂max). Vo₂max correlated inversely with T1 values (r=-0.79, P=0.01).

CONCLUSIONS

Children and adolescents with EA experience an abnormal degree of diffuse myocardial fibrosis. Its association with O₂ saturation points toward a role of hypoxemia in the pathogenesis of fibrosis. Larger and prospective studies are needed to evaluate the value of T1 mapping for risk stratification and monitoring in EA.

GDF-15 (Growth Differentiation Factor 15) Is Associated With Hospitalization and Mortality in Patients With a Fontan Circulation

Background We investigated serial serum levels of GDF-15 (growth differentiation factor 15) in Fontan patients and their relation to outcome. Methods and Results In this single-center prospective study of consecutive Fontan patients, serial serum GDF-15 measurement and clinical assessment was done at baseline (n=81) and after 2 years (n=51). The association between GDF-15 and the combined end point of all-cause mortality, heart transplant listing, and Fontan-related hospitalization was investigated. Median age at baseline was 21 years (interquartile range: 15-28 years). Median GDF-15 serum levels at baseline were 552 pg/mL (interquartile range: 453-729 pg/mL). GDF-15 serum levels correlated positively with age, age at Fontan initiation, New York Heart Association class, and serum levels of NT-proBNP (N-terminal pro-B-type natriuretic peptide) and ɣGT (γ-glutamyltransferase) and negatively with exercise capacity. During a median follow-up of 4.8 years (interquartile range: 3.3-5.5 years), the combined end point occurred in 30 patients (37%). Multivariate Cox regression showed that patients with the highest baseline GDF-15 (n=20, defined as the upper quartile) had a higher risk of hospitalization or death than the lowest 3 quartiles (hazard ratio [HR], 2.76; 95% CI, 1.27-6.00; P=0.011). After 2 years of follow-up, patients in whom serum level of GDF-15 increased to >70 pg/mL (n=13) had a higher risk of hospitalization or death than the lowest 3 quartiles (HR, 2.69; 95% CI, 1.03-6.99; P=0.043). Conclusions In Fontan patients, elevated serum levels of GDF-15 are associated with worse functional status and predict Fontan-related events. Furthermore, serial measurements showed that an increase in GDF-15 serum level was associated with increased risk for adverse outcome.

Imaging of complications following Fontan circulation in children - diagnosis and surveillance

The Fontan operation is performed for various cardiac lesions with single-ventricle physiology. The survival rate of Fontan patients is increasing for adolescents and young adults, with an expected 30-year survival of >80%. Medical health care providers including specialists in organ systems and pediatric radiologists need to improve their knowledge about the Fontan circulation and the various organ complications to monitor care. In this review the author explains the basic anatomical and functional features of Fontan palliation and gives an overview of the multiple long-term organ complications that might present in the pediatric population. These include decreased physical capacity, ventricular dysfunction, atrioventricular valve regurgitation and arrhythmia, as well as protein-losing enteropathy, plastic bronchitis, growth/bone composition disturbances, renal dysfunction, and the recently recognized and important liver fibrosis (Fontan-associated liver disease). Neuropsychological and behavioral deficits occur frequently. This review focuses on the key role of radiology in making the diagnosis of these complications, monitoring therapy and predicting outcomes in the pediatric age group. The author discusses how and when radiology is important in Fontan patients, as well as how new techniques enabling quantitative measures in imaging with US, MRI and CT are adapted for pediatric use, and how they contribute to urgently needed surveillance strategies.