Examining Outcomes After Transcatheter Pulmonary Valve Replacement
August 17, 2020
In February, pediatric cardiology researchers taking part in the multicenter Congenital Catheterization Collaborative Project on Outcomes-Quality Improvement (C3PO-QI) published findings in the Journal of the American College of Cardiology on aspects and outcomes of transcatheter pulmonary valve replacement (TPVR) in a cohort of 530 patients who underwent the procedure between 2014 and 2016. Study data were derived from the prospective C3PO-QI registry.
The objectives of the investigation were to better characterize and define the risks of serious adverse events (SAE), the likelihood of reintervention after TPVR, and quantify the levels of ionizing radiation patients are exposed to during TPVR procedures. While some prior studies have looked at adverse events in TPVR, this study is the first to examine radiation exposure parameters and the incidence of reinterventions.
Bryan H. Goldstein, MD, director of the cardiac catheterization laboratory (CCL) at UPMC Children’s Hospital of Pittsburgh, was the lead author of the study. Among other colleagues participating in the research was Jacqueline Kreutzer, MD, FACC, FSCAI, division chief of pediatric cardiology and co-director of the Heart Institute at UPMC Children’s.
Summary of Key Findings
In the last decade, the advent of TPVR has revolutionized pulmonary valve replacement (PVR) for patients who are appropriate candidates for the procedure. TPVR can reduce the number of open-heart procedures a patient is subjected to over a lifetime, and it can increase the time spent with normal pulmonary valve function by lowering the threshold for PVR.
However, like virtually all surgical and nonsurgical interventions, TPVR entails the risk of complications. A more robust knowledge of the types of risks and those most susceptible is at the heart of improving outcomes in TPVR, be it through procedural modifications and advancements or improved patient selection for the procedure. Goldstein et al. add to the TPVR evidence base in three primary areas. The length and detail of this study are extensive. The full findings of the published paper are available through the reference below. What follows is a summary of findings related to the main study objectives.
Adverse Events and Serious Adverse Events
TPVR is associated with a relatively high percentage of adverse events. Adverse events in this study were categorized from level 1 to level 5, with level 1 being none and level 5 being catastrophic. In this study cohort, 26% of patients experienced some form of adverse event, while the risk for serious adverse event (SAE; level 3-5) was 13%. Peri-procedural mortality risk in the study cohort was low, at 0.8%, and largely reflective of pre-existing conditions.
While direct comparisons between types of implants were not a part of this study, the findings did point to variability in adverse events depending upon the implant substrate – homograft, bioprosthesis, or native right ventricular outflow tract (RVOT). The risk of a SAE was highest in patients with a homograft conduit RVOT substrate. In the 226 cases where homograft was used, 18% experienced an SAE. Bioprosthesis and native cases experienced SAE at rates of 14% and 15%, respectively. This discrepancy reflected the inclusion of RVOT conduit injury as a SAE.
Radiation Exposure
Given the finite lifespan of pulmonary valve replacements, many patients may have multiple repeat procedures over their lifetime to replace implants that have reached the end of their functional capacity. Furthermore, given that the procedures in use today use x-ray guidance – which exposes patients to significantly more ionizing radiation than would otherwise be normal – understanding radiation dose in TPVR procedures is essential. This is particularly true in younger patients who are still developing physically, and also because these individuals are more likely to need future diagnostic and procedural imaging throughout their lifetime
Compared to other transcatheter procedures to treat congenital heart anomalies, TPVR procedures account for two times more radiation dose than the next highest-level procedure. In this study, the mean dose of radiation for TPVR was found to be 198 µGy-m2/kg. For comparison, the next highest level for an interventional cardiac procedure is balloon aortic valvuloplasty at 99 µGy-m2/kg.
Risk factors for receiving higher levels of radiation dose during TPVR procedure were shown to be:
- Older age
- Higher right ventricular pressure
- Use of 2 or more pre-TPV stents
- Presence of concomitant transcatheter intervention
Reintervention
Along with radiation exposure, this study is the first to examine the prevalence of reintervention after TPVR.
Analysis of the follow-up cohort of patients (a subset of the total study cohort consisting of complete follow-up individuals (68%) and partial follow-up individuals (84%)) found that 13.3% percent of patients had undergone a reintervention during the median follow-up period of one year from the date of their initial intervention.
Risk factors for reintervention were shown to include smaller patients, individuals with truncus arteriosus or pulmonary atresia and intact ventricular septum, a smaller baseline RVOT diameter, and a higher baseline RV-PA gradient.
Conclusion
While TPVR has established itself as a formidable, successful, and minimally invasive procedure for the treatment of congenital heart disease with RVOT dysfunction, it is not without significant risks for adverse events, exposure to ionizing radiation, and potential reintervention in the early follow-up period. Fortunately, mortality is an uncommon complication with TPVR. As Dr. Goldstein and colleagues write, future research and procedural advancements should address strategies and modifications to reduce radiation exposure to patients, limit and further study the nature of adverse events within certain patient populations, and address the high level of reinterventions through advances in technique and new implant technology, as well as through optimization of patient selection for TPVR.
Reference
Goldstein BH, et al. Adverse Events, Radiation Exposure, and Reinterventions Following Transcatheter Pulmonary Valve Replacement. J Am Coll Cardiol. 2020; 75: 363-376.
