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Applied Physiology to the Contemporary
Management of the Neonate with Hypoplastic Left
Heart Syndrome
Fernando Antibas Atik
Cleveland Clinic Foundation - Cleveland, Ohio - USA
Mailing Address:
The surgical treatment of hypoplastic left heart
syndrome is still a challenge. Few selected large volume
centers that adoptedprotocols focused on understanding
of post-Norwood pathophysiology have reduced their
mortality rates to around 15%. The inherent inefficacy
of the parallel circulation in Norwood operation lends
itself to problems related to postoperative management
of these patients crucially revolving around keeping a
balance between systemic blood flow (Qs) and pulmonary
blood flow (Qp). This paper describesthe physiology of
the Norwood principle, the importance of an adequate
hemodynamic assessment, to guide the different
postoperative management options.
Hypoplastic left heart syndrome (HLHS) constitutes
a spectrum of cardiac anomalies that result in
underdevelopment of left-sided heart structures. It is
characterized by aortic atresia or severe stenosis with
hypoplasia orabsence of the left ventricle1. Coarctation of
the aorta is usually the most frequent associated anomaly
and it may impede retrograde blood flow to a diminutive
ascending aorta. Postnatal survival is dependent on the
ductus arteriosus patency and shunting at atrial level.
The natural history is almost universally lethal in the
first month of life2.
The past decade experienced enormousimprovements
in the surgical treatment of HLHS. Several current
available surgical alternatives have been extensively
explored (Table 1). Although multi-institutional studies3
using intention to treat based analyses have demonstrated
higher intermediate term survival for patients entered
into heart transplantation4, the latter has become less
or equally important than the staged palliative surgicalapproach. Reasons include shortage of available
donors, post-transplant morbidity and limited long-term
survival5,6. Most importantly, there have been significant
improvements in the surgical palliation, originally
7. The progressive decline
in the surgical mortality is a result of multidisciplinary
protocols incorporated to the practice of pediatric
cardiac surgery8. Despite the initialprohibitive mortality
rates, mastering of surgical and anesthetic techniques
and the development of safer cardiopulmonary bypass
with adequate myocardial and cerebral protection have
made feasible the application of the Norwood principle
to HLHS.
Nevertheless, most pediatric heart centers still face
poor results in the treatment of this complex malformation.
Few selected large volume centersthat adopted protocols
focused on understanding of post-Norwood physiology
have reduced their mortality rates to around 10 to
15%. Greater emphasis is being demanded to achieve
the task of further reduction in this figure that, most would
agree, can be obtained by addressing the directives listed
on Table 2.
This review article describes the physiologic principles
that guide the modernsurgical treatment of the neonate
with HLHS.
Congenital left heart lesions, Congenital heart disease,
cyanotic, Univentricular heart, Neonate, Postoperative care
Table 1 – Current surgical alternative options in
hypoplastic left heart syndrome
Heart transplantation
Norwood procedure and modifications
• Cardiopulmonary bypass options
Deep hypothermic circulatory arrestHypothermic bypass with selective regional perfusion
• Type of arch reconstruction technique
No patch
• Source of pulmonary blood flow
Modified Blalock-Taussig shunt
Right ventricle to pulmonary artery conduit
Stenting of the arterial duct and banding of the pulmonary arteries

Arquivos Brasileiros de Cardiologia - Volume 87, Nº 3, September 2006
Fernando Antibas Atik
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