Temporary restriction of right ventricle-pulmonary artery conduit flow using haemostatic clips following Norwood I reconstruction: potential for improved outcomes

Abstract

Improved outcomes of the Norwood procedure in hypoplastic left heart syndrome have been achieved by the manipulation of the pulmonary:systemic flow ratio (Qp:Qs) in the early post-operative period, with focus on improving systemic perfusion. As an extension of this Qp:Qs-limiting strategy, we evolved a novel surgical technique to achieve transient flow restriction in the right ventricle-pulmonary artery (RV-PA) conduit for the first 48 h, using haemostatic clips, in a cohort of patients and compared the early outcomes with a non-clipped cohort. Clips were subsequently removed at 48 h at the time of definitive chest closure. We performed RV-PA shunt flow clipping in 37 patients; 75 historical controls had not received clips. Groups were matched for weight, size of ascending aorta, anatomy and circulatory arrest times. Thirty-day mortality was lower in the clipped cohort (2 of 37; 5.4%) versus the unclipped cohort (10 of 75; 13.3%). The minimum blood lactate levels within the first 24 h post-surgery in the unclipped group were significantly higher (P = 0.049), with a significantly lower Qp:Qs in the first 6 h in the clipped patients. These data suggest that limiting Qp:Qs in the early post-operative period following the Norwood procedure may help in the post-operative management of these difficult patients. These results warrant further study.

Figure 1:

Intra-operative photographs of RV–PA conduit showing insertion of the unclipped (A) or clipped (B, arrowheads) conduit (*) to the right pulmonary artery. Also shown at the top of the images is the innominate artery shunt for CPB arterial return. (C) Minimum 24-h arterial blood lactate levels in unclipped versus clipped patients. The box and whisker plots show the median values for blood lactate (bold horizontal line within boxes) as well as the 95% range (whiskers). Outliers are indicated by circles. Many more outliers with higher lactate values are seen in the unclipped cohort of patients; this was statistically significant (the Kruskal–Wallis rank-sum test). (D) Values for the Qp:Qs ratio for unclipped (group 1; blue) and clipped (group 2; green) patients. The mean ± SEM for each 6-h time interval epoch post-Norwood I is shown. The Qp:Qs ratio was significantly lower (P < 0.05; Kruskal–Wallis) for clipped patients during epoch 1 (first 6 h) and epoch 10 (55–60 h). Epoch 10 is after clip removal (red arrow). By epoch 11, values for Qp:Qs in the clipped cohort increase again.