Genetic variants of HIF1α are associated with right ventricular fibrotic load in repaired tetralogy of Fallot patients: a cardiovascular magnetic resonance study

Myocardial Fibrosis in Congenital Heart Disease and the Role of MRI

Progress in the field of congenital heart surgery over the last century can only be described as revolutionary. Recent improvements in patient outcomes have been achieved through refinements in perioperative care. In the current and future eras, the preservation and restoration of myocardial health, beginning with the monitoring of tissue remodeling, will be central to improving cardiac outcomes. Visualization and quantification of fibrotic myocardial remodeling is one of the greatest assets that cardiac MRI brings to the field of cardiology, and its clinical use within the field of congenital heart disease (CHD) has been an area of particular interest in the last few decades. This review summarizes the physical underpinnings of myocardial tissue characterization in CHD, with an emphasis on T1 parametric mapping and late gadolinium enhancement. It describes methods and suggestions for obtaining images, extracting quantitative and qualitative data, and interpreting the results for children and adults with CHD. The tissue characterization observed in different lesions is used to examine the causes and pathomechanisms of fibrotic remodeling in this population. Similarly, the clinical consequences of elevated imaging biomarkers of fibrosis on patient health and outcomes are explored. Keywords: Pediatrics, MR Imaging, Cardiac, Heart, Congenital, Tissue Characterization, Congenital Heart Disease, Cardiac MRI, Parametric Mapping, Fibrosis, Late Gadolinium Enhancement © RSNA, 2023.

Patients with repaired tetralogy of Fallot and the HIF1A1744C/T variant have increased imaging markers of diffuse myocardial fibrosis

BACKGROUND

Right ventricular fibrotic remodeling has been identified pre- and postoperatively in patients with tetralogy of Fallot (ToF) and linked to adverse outcomes. Polymorphisms of hypoxia inducible factor-1-alpha (HIF1A) have been associated with the fibrotic burden by cardiac magnetic resonance (CMR) late gadolinium enhancement imaging. Their association with diffuse fibrotic myocardial remodeling is unknown. We sought to determine whether polymorphisms in HIF1A are related to CMR markers of diffuse myocardial fibrosis.

METHODS

Patients with repaired ToF who had undergone CMR with T1 mapping as well as whole genome sequencing were included. Myocardial native T1 was quantified using a modified Look-Locker inversion recovery sequence and measured in the left ventricular free wall, the interventricular septum, and the right ventricular free wall. Patients who had at least one functioning allele of HIF1A were compared to those who did not using the Mann Whitney U test for continuous variables and chi-square or the Fischer test for discrete variables.

RESULTS

46 patients had both CMR and whole genome sequencing. Only one HIF1A variant was identified in the cohort and present in 13 patients. There were no significant differences in demographics, surgical variables, right or left ventricular volumes or function between patients with and without the variant. Despite a trend towards a lower age at the time of CMR (11.3 vs 13.7 years; p = 0.07), patients with HIF1A variants had higher native T1 values (1094 vs. 1050; p = 0.027) in the right ventricular outflow tract myocardium, reflecting increased diffuse interstitial ventricular fibrosis in them.

CONCLUSION

Hypoxia-inducible factor is associated with imaging markers of increased diffuse right ventricular fibrosis late after repair of tetralogy of Fallot.

HIF-1α Pulmonary Phenotype Wide Association Study Unveils a Link to Inflammatory Airway Conditions

Despite experimental data linking HIF-1α dysfunction to inflammatory airway conditions, the effect of single nucleotide polymorphisms within the HIF1A gene on these conditions remains poorly understood. In the current study, we complete a phenotype wide association study to assess the link between SNPs with known disease associations and respiratory phenotypes. We report two SNPs of the HIF1A gene, the intronic rs79865957 and the missense rs41508050. In these positions the A and the T allele are significantly associated with allergic rhinitis and acute bronchitis and bronchiolitis, respectively. These findings further support the role of HIF-1α in inflammatory pulmonary conditions and may serve as a basis to refine our understanding of other HIF-1α associated phenotypes.

Late gadolinium enhancement in patients with Tetralogy of Fallot: A systematic review

PURPOSE

The aim of this study is to review the literature concerning myocardial late gadolinium enhancement (LGE) with cardiac magnetic resonance in patients with Tetralogy of Fallot (ToF), with regards to its prevalence, characteristics and clinical relevance.

METHODS

We performed a systematic search, aiming to retrieve original articles that evaluated LGE in ToF, running a search string on MEDLINE and EMBASE in November 2019 and November 2020. Papers were then selected by two independent, blinded readers based on title and abstract, and then on full-text reading, and articles which did not include LGE evaluation were excluded. From each included paper two readers extracted descriptive data concerning technical parameters of LGE acquisition, LGE description and clinical significance.

RESULTS

18 articles were eventually included in our review. The included studies observed that a higher amount of right ventricular LGE relates with higher right ventricular volumes, lower ejection fraction and a higher pulmonary regurgitant fraction, thus acting as a marker of progressive impairment of myocardial function. Moreover, LGE in ToF patients correlated with the onset of arrhythmias, and with serum biomarkers indicative of myocardial stress and fibrosis.

CONCLUSIONS

LGE could be used in the follow-up repaired ToF patients as its appraisal can provide information concerning cardiac dysfunction. Moreover, it may be ideal to aim towards a common framework for standardizing assessment and quantification of LGE in ToF patients.