Frommelt PC, Hu C, Trachtenberg F, Baffa JM, Boruta RJ, Chowdhury S, Cnota JF, Dragulescu A, Levine JC, Lu J, Mercer-Rosa L, Miller TA, Shah A, Slesnick TC, Stapleton G, Stelter J, Wong P, Newburger JW.
Circ Cardiovasc Imaging. 2019 Feb;12(2):e007865. doi: 10.1161/CIRCIMAGING.118.007865.
Take Home Points:
- Shunt type has no significant impact on echocardiographic indices of right ventricle, neoaortic, and tricuspid valve size and function after the first palliation by 6 years of life.
- Decreases in RV function present in the RV to pulmonary artery shunt seen in the previous SVR trial were no longer present, suggesting ongoing RV remodeling with time.
- Future incorporation of this data with newer echo modalities, MRI results, and quality of life measures (self-reported or even exercise testing data as these patients get older) may give us even more beneficial data for this population.
Commentary from Dr. Jared Hershenson (Greater Washington DC), section editor of Pediatric Cardiology Journal Watch: This is the most recent update from the Pediatric Heart Network SVR trial comparing 549 infants with single RV anomalies randomly assigned to a modified Blalock-Taussig shunt (MBTS) or RV to pulmonary artery shunt (RVPAS) at 15 centers in North America. The goal was to determine if shunt type was associated with better clinical outcome. Previous SVR trial articles showed a better 1 year transplant free survival in the RVPAS group, but this survivor benefit was no longer present at 3 years of life. Similarly, the early improved RV ejection fraction (RVEF) in the RVPAS group diminished over time, and in fact, at 3 years, the RVEF was worse in the RVPAS compared to the MBTS group.
This surveillance time point included those patients who had an echocardiogram performed within 6 months of Fontan palliation and at 6 years of life. 2D and Doppler indices of RV size and function were assessed, as well as neoaortic and tricuspid valve size and function. Exclusions included patients who underwent cardiac transplantation, a few who had biventricular repair, and those that did not consent to the extension trial. The specific echocardiographic and core lab procedures were described in earlier reports and unchanged for this study.
241 studies were analyzed with 116 MBTS and 125 RVPAS; 208 of those at undergone a pre-Fontan echo and 228 also had an acceptable echo at 14 months. In the overall cohort at the 6 year compared to the pre-Fontan echo, RV systolic and diastolic volumes and indexed areas decreased significantly, and RVEF, FAC, and peak tricuspid annular systolic velocity increased significantly (Table 2). When compared to the 14 month study, 6 year RV systolic and diastolic volume was significantly decreased, but RVEF increased nonsignificantly (P=0.06). When comparing interval changes by group, RVEF and FAC increased significantly in the RVPAS group vs. the MBTS group (Figure 2). There was an increase in MPI by PW Doppler (and not by tissue Doppler) over time (14 month to post-Fontan), but no difference at 6 years between groups. However, the increase was only significant for the MBTS group when comparing pre-Fontan and 6 years.
Neoaortic annular areas were larger in MBTS vs. RVPAS, but both were significant large compared to normal (z-score 6.4 and 5.4 respectively). Greater than mild regurgitation was rare and similar between groups. There was a significant decrease in size when comparing the 14 month and 6 year studies (no difference from pre-Fontan to 6 years). Indexed tricuspid annular areas and z-scores were similar in both groups at 6 years. Greater than moderate TR occurred in 17% of subjects in each group. There was significant decrease in annular size between 14 months and 6 years, but no difference from pre-Fontan to 6 years.
The authors also evaluated the 14 month RVEF and the relationship to late death/transplant. There were 43 deaths/transplants in the 337 patients who had 14 month echocardiograms. Decreased RVEF (<40%) had a hazard ratio of 3.18 for death/transplant. Shunt type had no effect.
This study at 6 years of follow up shows no difference in outcomes (echocardiographic and clinical) between shunt groups. Based on changes at this time point vs. the earlier time point, RV remodeling has occurred resulting in equivocal RV systolic and diastolic function regardless of shunt type. There have been concerns about the RV ventriculotomy and resultant injury/scarring potentially affecting RV performance, but this was not seen by 6 years. Additionally, the RVPAS group showed a similar survival/transplant free rate to the MBTS group at 6 years, despite the initial lower death/transplant-free survival benefit up to stage 2, and then an increase in death until the Fontan, showing that there was some beneficial change that occurred with time particularly in this group. The study confirms the lack of significant neoaortic and tricuspid valve issues in this younger age cohort, even with the marked increase in annular size compared to normal patients. Additionally, RVEF < 40% at 14 months remains a significant risk factor for death/transplant. It is important to note that the RVPAS group had a significantly higher incidence of catheter-based interventions, and it is possible that the improved hemodynamics may have contributed to the improved RV function. Multiple required interventions may have a “familial” and quality of life affect that has not been assessed.
Limitations of the study were clearly delineated. RV function is very difficult to evaluate in general by echo, and in particular in those with a single RV. Rudimentary LV mechanical effects on the single RV were also not assessed (and typically cannot be when only using echocardiographic tools). The addition of newer echocardiographic modalities such as strain and 3D assessment of the tricuspid valve, as well as MRI data, may be very helpful moving forward. There is some discussion that MRI data will be included in the next follow up report as the patients reach 10-12 years of age.
An accompanying editorial provides an additional question that is important to consider. Are there outcomes besides RV function that should be assessed? Health related quality of life measures and a better assessment of functional status (patient and parental reporting as well as future exercise data as these patients get older and are able to be tested on a cycle ergometer or treadmill) may provide a better functional insight into how these patients are over time.
Table 2 (cut):