Letter by Phillips Regarding Article, “Comparison of the Profiles of Postoperative Systemic Hemodynamics and Oxygen Transport in Neonates After the Hybrid or the Norwood Procedure: A Pilot Study”
To the Editor:
I want to compliment Li et al on a very unique study1 evaluating oxygen consumption and delivery during the first 72 hours postoperatively in patients with hypoplastic left heart syndrome treated by either the Norwood procedure (n=13) or the hybrid procedure (n=6). The study design was excellent; however, it is my opinion that there are several problems with the study and the conclusions drawn by the authors.
The hybrid procedure, which is generally used by most centers, involves placement of bilateral branch pulmonary artery bands and a stent in the patent ductus arteriosus either by a transpulmonary approach2 (Columbus) or percutaneous approach3 (Giessen). The need for augmentation of antegrade perfusion through arch intervention in the catheterization laboratory or for a reverse Blalock-Taussig shunt occurs in only 10% of the patients.4 A reverse Blalock-Taussig shunt in a patient with no retrograde arch issues may lead to differential perfusion, unnecessary volume load, and diastolic steal.
The study by Li et al1 was nonrandomized, with 2 hybrid procedure patients each weighing <2.7 kg, 1 of whom was not a Norwood candidate and 1 of whom was a transplant candidate. The remaining 3 patients in the hybrid procedure group should be considered comparable for analysis. Li et al conclude that the hands-off approach to postoperative management of patients undergoing the hybrid procedure may be inappropriate in patients with diminished myocardial function, as milrinone and phenoxybenzamine were routinely used in Norwood procedure patients but not hybrid procedure patients, and they may lead to a higher systemic vascular resistance. The data do not support this observation, however; 4 hybrid procedure patients received milrinone and 1 received phenoxybenzamine. The data for length of intubation seem confusing. The authors1 that state extubation for patients undergoing the hybrid procedure was between 1 to 8 days (median 6 days) and for patients undergoing the Norwood procedure was 4 to 16 days (median 7 days); however, duration of intubation was longer for the Norwood group (11±6 days versus 5±2 days; P=0.026). In the “Columbus experience,” 82% of patients were extubated and started on enteral feeds within 24 hours.5
There is an incredible variability in the Qp:Qs for the hybrid procedure patients postoperatively, with range of 0.36 to 5.7. Values were between 2 to 3 in 17% of measurements and >3 in 11% of measurements. This variability indicates variability in the tightness of the bands on the pulmonary arteries, with many bands too loose to adequately control pulmonary blood flow. By comparison, the Norwood patients had a Qp:/QS ranging from 0.3 to 3.3, with a value >2 in only 5% of measurements. The 50% failure rate (ie, death or need for transplant) in the hybrid procedure group may be related to inadequate banding. The authors hypothesize that myocardial dysfunction may be related to an acute pressure load to an already volume-loaded single right ventricle. In this study, however, a combination of loose bands and a reverse Blalock-Taussig shunt adds an unnecessary volume load on the heart.
Li et al1 placed a reverse Blalock-Taussig shunt during their hybrid procedure, which is unnecessary in my opinion. Also, it stresses the single right ventricle, especially in light of loose bands, and may account for the poor clinical results and the oxygen consumption data obtained in this study.
Li J, Zhang G, Benson L, Holtby H, Cai S, Humpl T, Van Arsdell GS, Redington AN, Caldarone CA. Comparison of the profiles of postoperative systemic hemodynamics and oxygen transport in neonates after the hybrid or the Norwood procedure: a pilot study. Circulation. 2007; 116 (suppl I): I-179–I-187.
Akintuerk H, Michel-Behnke I, Valeske K, Mueller M, Thul J, Bauer J, Hagel KJ, Kreuder J, Schranz D. Stenting of the arterial duct and banding of the pulmonary arteries: basis for combined Norwood stage I and II repair in hypoplastic left heart. Circulation. 2002; 105: 1099–1103.
Cheatham J. Hybrid stage I palliation for HLHS: transcatheter approach for retrograde aortic arch stenosis. Presented at the International Symposium on the Hybrid Approach to Congenital Heart Disease; June 27, 2007; Columbus, Ohio.
Galantowicz M, Cheatham JP, Phillips A, Cua Clifford CL, Hoffman TM, Hill SL, Rodeman R. The hybrid approach for the management of hypoplastic left heart syndrome: intermediate results after the learning curve (poster). Presented at the 2007 Society of Thoracic Surgeons annual meeting; January 30, 2007; San Diego, Calif.