Teaching the "hybrid approach": a novel swine model of muscular ventricular septal defect

Pediatric interventional cardiology: 2009

PURPOSE OF REVIEW

Pediatric interventional cardiology has evolved quite dramatically over the past few decades and now, in 2009, the published literature continues to evolve new percutaneous strategies for managing patients with congenital heart disease, both simple and complex. Our goal for this review was to highlight new techniques and the new devices available to the pediatric interventional cardiologist, and to review the outcomes from past endeavors.

RECENT FINDINGS

Manuscripts published in the past year continue to demonstrate innovation; indicating an exciting and increasing experience of transcatheter treatment of septal communications using either new occluder devices or novel techniques. Bioabsorbable devices and percutaneously implanted valves are leading examples of technological improvements and creativity that will ultimately improve patient outcomes while minimizing invasiveness. Reports on procedural outcomes show technically safe early follow-up, with promising mid-term and long-term results for balloon valvuloplasty, balloon atrial septostomy and pulmonary artery stent implantation. As well, fetal and hybrid interventions have become important new arenas for the pediatric interventionist.

SUMMARY

Pediatric interventions have grown far beyond the early stages of the 1980s as mid-term and long-term outcome data are being reported, and many previously insurmountable hurdles have been overcome by developing new strategies and devices.

Right ventricular remodeling in restrictive ventricular septal defect

Restrictive ventricular septal defect (rVSD) presents with little/no hemodynamic aberrations despite a patent septal defect. Clinically, these patients are observed with the hope that the defect will functionally close over time without the need for surgical repair and development of heart failure. Without evidence supporting a definitive therapeutic strategy, rVSD patients may have increased risk of a poor outcome. We tested the hypothesis that rVSD results in subclinical RV diastolic dysfunction and molecular remodeling. Five pigs underwent surgical rVSD creation. Echocardiography, hemodynamics, myocyte contractility experiments, and proteomics/Western blot were performed 6-weeks post-rVSD and in controls. *p<0.05. LV and RV hemodynamics in rVSD were comparable to controls. The tricuspid valve early/late diastolic inflow velocity ratio (TV E/A ratio) decreased from 1.6+/-0.05 in controls to 1.0+/-0.08* in rVSD, indicating RV diastolic dysfunction. rVSD RV myocytes showed abnormalities in contraction (departure velocity (Vd) -51%*, Vd time +55%*) and relaxation (return velocity (Vr) -50%*, Vr time +62%*). Mitochondrial proteins (fatty acid, TCA cycle) increased 2-fold*, indicating heightened RV work. Desmin protein upregulated 285%* in rVSD RV myocardium, suggesting cytoskeletal remodeling. rVSD causes RV diastolic dysfunction, myocyte functional impairment, and mitochondrial/cytoskeletal protein upregulation in our model. Desmin upregulation may hinder sarcomeric organization/relaxation, representing a key subclinical early marker for future RV dysfunction. TV E/A measurements are a non-invasive modality to assess rVSD patients for diastolic dysfunction. Translational research applications may lead to fundamental changes in the clinical management of rVSD by providing evidence for early repair of the defect.