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Published on: October 6, 2022
Treating a 20 mm Hg gradient alleviates myocardial hypertrophy in experimental aortic coarctation
David C Wendell1, Ingeborg Friehs2, Margaret M Samyn3
1Department of Biomedical Engineering, Marquette University and Medical College of Wisconsin, Milwaukee, Wisconsin; Division of Cardiology, Department of Medicine, Duke University Medical Center, Duke Cardiovascular Magnetic Resonance Center, Durham, North Carolina.
Insights
Coarctation of the aorta (CoA) in rabbits led to elevated left ventricular (LV) mass. Even after correction, LV function showed trends toward hyperdynamic states, suggesting the 20 mm Hg gradient guideline may be appropriate.
Area of Science:
- Cardiovascular Research
- Pediatric Cardiology
- Medical Imaging
Background:
- Children with coarctation of the aorta (CoA) often exhibit left ventricular (LV) remodeling and hyperdynamic function due to increased afterload.
- Existing literature suggests that a 20 mm Hg blood pressure gradient (BPG) treatment guideline may not prevent irreversible vascular changes.
Purpose of the Study:
- To investigate LV remodeling and function in a rabbit model of CoA following surgical correction.
- To evaluate the impact of a clinically relevant BPG on LV structure and hemodynamics post-CoA repair.
Main Methods:
- Rabbits underwent induced CoA at 10 weeks, with either permanent or dissolvable sutures to model untreated and corrected CoA.
- Cardiac function was assessed at 32 weeks using magnetic resonance imaging (MRI), quantifying LV volume, ejection fraction (EF), and mass.
Main Results:
- LV mass was significantly elevated in untreated CoA rabbits compared to controls and corrected CoA rabbits.
- A trend towards increased EF and stroke volume was observed in CoA rabbits, supported by increased aortic flow.
- Quantified indices suggested a persistent hyperdynamic LV state post-correction, though not statistically significant compared to controls.
Conclusions:
- The study indicates that a 20 mm Hg BPG may be a reasonable treatment target from the LV's perspective, as it did not lead to statistically significant adverse LV remodeling or hyperdynamic function post-correction.
- Further research is needed to fully understand long-term LV adaptation after CoA correction within this BPG.
Background:
Children with coarctation of the aorta (CoA) can have a hyperdynamic and remodeled left ventricle (LV) from increased afterload. Literature from an experimental model suggests the putative 20 mm Hg blood pressure gradient (BPG) treatment guideline frequently implemented in CoA studies may permit irreversible vascular changes. LV remodeling from pressure overload has been studied, but data are limited following correction and using a clinically representative BPG.
Materials And Methods:
Rabbits underwent CoA at 10 weeks to induce a 20 mm Hg BPG using permanent or dissolvable suture thereby replicating untreated and corrected CoA, respectively. Cardiac function was evaluated at 32 weeks by magnetic resonance imaging using a spoiled cine GRE sequence (TR/TE/FA 8/2.9/20), 14 × 14-cm FOV, and 3-mm slice thickness. Images (20 frames/cycle) were acquired in 6-8 short axis views from the apex to the mitral valve annulus. LV volume, ejection fraction (EF), and mass were quantified.
Results:
LV mass was elevated for CoA (5.2 ± 0.55 g) versus control (3.6 ± 0.16 g) and corrected (4.0 ± 0.44 g) rabbits, resulting in increased LV mass/volume ratio for CoA rabbits. A trend toward increased EF and stroke volume was observed but did not reach significance. Elevated EF by volumetric analysis in CoA rabbits was supported by concomitant increases in total aortic flow by phase-contrast magnetic resonance imaging.
Conclusions:
The indices quantified trended toward a persistent hyperdynamic LV despite correction, but differences were not statistically significant versus control rabbits. These findings suggest the current putative 20 mm Hg BPG for treatment may be reasonable from the LV's perspective.
