Single Ventricle Reconstruction Trial Norwood shunt size variation and association with post-operative outcomes
Presented By:
Luisa Raga, MD; Haleh Heydarian, MD; David Winlaw, MD; Huaiyu Zang, PhD; Nicholas Ollberding, PhD; Garick Hill, MD
Cincinnati Children's Hospital Medical Center
luisa.raga@cchmc.orgOverview:
Objective: Morbidity and mortality is highest following the Norwood procedure. The selected shunt size can affect the hemodynamics of the Norwood physiology. The Single Ventricle Reconstruction (SVR) trial randomized subjects with a single morphologic right ventricle undergoing a Norwood procedure to a modified Blalock–Taussig-Thomas shunt (MBTTS) or a right ventricle-to-pulmonary artery shunt (RVPAS). However, shunt size selection has not been well described in the literature and the impact on postoperative outcomes is not well described. Using data from the SVR trial, we sought to assess variation in shunt to patient size and the association of shunt size with postoperative outcomes.
Methods: The SVR public use dataset was queried. Pre-operative, intra-operative and post-operative data were extracted. Normalized shunt diameter (NSD) was calculated as shunt diameter (mm)/patient weight closest to Norwood (kg). Primary outcome was 30-day mortality after the Norwood procedure. Secondary outcomes were Intensive Care Unit (ICU) length of stay and survival to Glenn procedure. Logistic and ordinal regression models were used to evaluate the association of NSD with outcomes of interest.
Results: 544 patients were included with 5 patients excluded for ambiguous shunt crossover data. 529 patients were included in the multivariable analyses due to the missing covariates. The 30-day post-operative mortality was 11.4% (n = 62), survival to Glenn was 72.6% (n= 395) , the median of ICU length of stay was 14.00 (IQR: 9.00 to 27.75) and the median of Norwood's length of stay was [24.00 (16.00, 41.00)]. Median NSD1 was 1.12 mm/kg but ranged from 0.85 to 2.20 mm/kg for MBTTS. Median RVPAS NSD1 was 1.75 mm/kg and ranged from 0.96 to 3.61 mm/kg. No significant association between NSD1 or NDS2 and 30-day mortality in either the MBTTS ( NSD1 p = 0.238, NSD2 p = 0.786 ) or RVPAS (NSD1 p = 0.968, NSD2 p = 0.527 ) group. The odds of survival to Glenn procedure decreased with increasing NSD1 >1.5 mm/kg and NSD 2 > 20 mm/m2 in the MBTTS group, but not statistically significant (NSD1: OR = 0.28, 95% CI = 0.04 to 1.90, p = 0.191, NSD2: OR = 0.06, 95% CI = 0.002 to 1.45, p = 0.083 ) (Figure 2 and Figure 3). The odds of a longer ICU length of stay increased with increasing NSD1 >1.5 mm/kg in the MBTTS group (OR = 4.11, 95% CI = 1.25 to 13.49, p = 0.020) (Figure 2).Similarly, the odds of a longer Norwood length of stay increased with increasing NSD1 >1.5 mm/kg in the MBTS group (OR = 4.89, 95% CI = 1.41 to 16.90, p =0.012) (Figure 2).
Conclusion: Utilizing data from the SVR trial, we performed the first multicenter comparative analysis of Norwood shunt size. We identified significant variation in the normalized shunt diameter for both MBTTS and RVPAS. In the RVPAS group, there is a wider range of NSD1 and NSD2 associated with good outcomes when compared to MBTTS group. Larger shunt diameter normalized to patient weight is associated with increased post-operative length of stay for the MBTTS. While optimal shunt size determination will require further analysis, a MBTTS size of ≥1.5 mm/kg is associated with worse outcomes. 30-day mortality is an inadequate outcome in isolation to evaluate optimal shunt sizing due to low event rate. This may represent the ability to prolong life in situations of poor post-operative outcomes in which survival to Glenn is improbable.
Methods: The SVR public use dataset was queried. Pre-operative, intra-operative and post-operative data were extracted. Normalized shunt diameter (NSD) was calculated as shunt diameter (mm)/patient weight closest to Norwood (kg). Primary outcome was 30-day mortality after the Norwood procedure. Secondary outcomes were Intensive Care Unit (ICU) length of stay and survival to Glenn procedure. Logistic and ordinal regression models were used to evaluate the association of NSD with outcomes of interest.
Results: 544 patients were included with 5 patients excluded for ambiguous shunt crossover data. 529 patients were included in the multivariable analyses due to the missing covariates. The 30-day post-operative mortality was 11.4% (n = 62), survival to Glenn was 72.6% (n= 395) , the median of ICU length of stay was 14.00 (IQR: 9.00 to 27.75) and the median of Norwood's length of stay was [24.00 (16.00, 41.00)]. Median NSD1 was 1.12 mm/kg but ranged from 0.85 to 2.20 mm/kg for MBTTS. Median RVPAS NSD1 was 1.75 mm/kg and ranged from 0.96 to 3.61 mm/kg. No significant association between NSD1 or NDS2 and 30-day mortality in either the MBTTS ( NSD1 p = 0.238, NSD2 p = 0.786 ) or RVPAS (NSD1 p = 0.968, NSD2 p = 0.527 ) group. The odds of survival to Glenn procedure decreased with increasing NSD1 >1.5 mm/kg and NSD 2 > 20 mm/m2 in the MBTTS group, but not statistically significant (NSD1: OR = 0.28, 95% CI = 0.04 to 1.90, p = 0.191, NSD2: OR = 0.06, 95% CI = 0.002 to 1.45, p = 0.083 ) (Figure 2 and Figure 3). The odds of a longer ICU length of stay increased with increasing NSD1 >1.5 mm/kg in the MBTTS group (OR = 4.11, 95% CI = 1.25 to 13.49, p = 0.020) (Figure 2).Similarly, the odds of a longer Norwood length of stay increased with increasing NSD1 >1.5 mm/kg in the MBTS group (OR = 4.89, 95% CI = 1.41 to 16.90, p =0.012) (Figure 2).
Conclusion: Utilizing data from the SVR trial, we performed the first multicenter comparative analysis of Norwood shunt size. We identified significant variation in the normalized shunt diameter for both MBTTS and RVPAS. In the RVPAS group, there is a wider range of NSD1 and NSD2 associated with good outcomes when compared to MBTTS group. Larger shunt diameter normalized to patient weight is associated with increased post-operative length of stay for the MBTTS. While optimal shunt size determination will require further analysis, a MBTTS size of ≥1.5 mm/kg is associated with worse outcomes. 30-day mortality is an inadequate outcome in isolation to evaluate optimal shunt sizing due to low event rate. This may represent the ability to prolong life in situations of poor post-operative outcomes in which survival to Glenn is improbable.
