Background
Despite successful repair of tetralogy of Fallot (TOF), the life expectancy for these patients remains lower than in the general population. This is mainly due to free pulmonary regurgitation (PR). The importance of maintaining a competent valve has been emphasized, but the optimal timing for intervention remains to be established. The purposes of this study were in a pig model to investigate the consequences of the duration of free PR on RV, and the reversibility of these changes after percutaneous pulmonary valve replacement.
Methods
Thirtysix farm pigs were divided into four groups (A, B, C and D) of nine pigs. At baseline group A, B and C had a percutaneous stent inserted into the pulmonary annulus to create free PR. After 4, 8 and 12 weeks, respectively, group A, B and C underwent percutaneous valve replacement. In order to allow remodelling of RV, the pigs were observed for four weeks after valve insertion before euthanasia. To examine RV function, MRI was performed before stent insertion, before valve replacement, and before euthanasia. Group D served as controls and underwent five MRI examinations: at baseline as well as after four, eight, twelve and sixteen weeks.
Results
When comparing the group D with group A, B & C, RVEDV and RVESV were found to gradually increase over time. Furthermore, these volumes normalised after valve replacement in group A and B, but remains increased in the group C. Similar, RVEF was normal after valve replacement in group A and B, but impaired in the group the long-term free PR compared to the controls.
Conclusion
Better timing of valve replacement in patients with free PR after TOF repair is of outermost clinical relevance. This study examined the impact of free PR on RV in a pig model. Despite the relative short duration of the volume overload, the RV underwent irreversible changes. This may be explained by the fact that, in contrast to TOF, the RV is not hypertrophic. The study showed that RV tolerates volume overload from free PR for a certain time, but too late intervention will cause irreversible deterioration of the ventricular function. Thus, the model may serve to identify predictors, e.g. tissue-Doppler measurements or natriuretic peptides, for RV function after valve replacement and thereby optimise timing of intervention.
Surgical Pulmonary Valve Replacement Due to Failed Percutaneous Pulmonary Valve Intervention in a Patient After Correction of Fallot’s Tetralogy: Surgery Remains the Standard
