B Suys, K De Groote, W De Caluwe, J Panzer, K Francois, T Bové, D Matthys,

H Verhaaren, D De Wolf.

Centre for congenital heart diseases Anna Blancquaert,

University Hospitals Ghent- Antwerp.

Left heart outflow abnormalities include aortic stenosis ( subaortic, valvar, supravalvar narrowing of the ascending aorta), coarctation or interruption of the aorta, and the hypoplastic left heart syndrome (HLHS). Hypertropic obstructive cardiomyopathy will not be discussed here.

The initial clinical symptoms but also the final treatment will depend on the severity of the stenosis or outflow obstruction, ductal dependency, and often more importantly the grade of hypoplasia of the left ventricle or the mitral valve apparatus. When an abnormality is found in the left heart or outflow, it is always important to check the other left cardiac structures and the aorta. This association of multiple left-sided obstructive lesions with coarctation has been referred to as Shone’s syndrome or complex, and constitutes a challenging group of lesions if treatment is required in infancy.

Often, newborns with mild or moderate left ventricle outflow obstructions will be asymptomatic; severe or critical obstructions however lead to obvious clinical symptoms immediately after birth or within a few days; mostly, ductal dependency then plays a major role. Therefore it is important to recognize an infant with low output heart failure resulting from left heart outflow obstruction, in order to start intravenous prostaglandins E1 immediately to provide sufficient systemic blood flow, a life saving decision. Every newborn with signs of heart failure, weak pulses even without a typical murmur should be monitored intensively and receive PGE1 as soon as possible, despite lacking a specific diagnosis.

During or after patient stabilization, the diagnostic work-out can start, consisting predominantly of a detailed echocardiographic examination. Here it is important to have a careful look at the respective outflow obstruction(s), but also at the other features of cardiac structure including aortic size, degree of eventual left ventricular hypoplasia, and the degree of eventual mitral hypoplasia. This is critical for further therapeutic decisions in case of critical aortic stenosis, where the alternatives to valvotomy resulting in a two-ventricle repair include cardiac transplantation in some countries, or a Norwood procedure. This is a two- or three-stage single ventricle repair in which the main pulmonary artery is anastomosed to the aorta with creation of a systemic-to-pulmonary shunt, followed later by a cavo-pulmonary connection (Fontan-type operation). Generally, the decision as to which approach to take must be made within the first hours or days of life.

In 1991, Rhodes et al. have demonstrated that the adverse effects of small inflow, outflow, and/or cavity size of the left ventricle are cumulative, and that clinical decisions should not be made based on left ventricular size alone. This resulted in the so-called Rhodes criteria, and the proposition of a discriminative score for survival. The equation for this score = 14,0 (BSA) + 0,943 (ROOTi) + 4,78 (LAR) + 0,157 (MVAi) – 12,03, including body surface area (BSA), the aortic root dimension indexed to body surface area (ROOTi), the ratio of the long-axis dimension of the LV to the long-axis dimension of the heart (LAR), and the indexed mitral valve area (MVAi) (1). A discriminating score of less than – 0,35 is predictive of death using a two-ventricle repair. More recent studies showed that this Rhodes score is not always completely applicable, for example in neonatal aortic arch obstruction with left heart hypoplasia. They proposed that two more parameters should be used to define ventricles adequate for biventricular repair, namely the presence of antegrade aortic flow and bidirectional shunting at the ductal level (2). Other authors proposed additional criteria precluding biventricular repair, a mitral annulus below 9 mm, a left to right ventricle end diastolic diameter ratio below 0,33 and a heart apex made by the right ventricle; other recent reports stated that these criteria should not always be followed very strictly because an initially “too small” anatomically normal left ventricle can grow when every cause of obstruction is relieved.

At the severe end of the left heart obstruction spectrum is HLHS with almost total absence of the left ventricle, hypoplasia of the ascending aorta, aortic valve atresia or severe stenosis, and mitral valve atresia or stenosis. Without surgical intervention, the condition is uniformly fatal and approximately 90% of patients die in the first month of life. In contrast to a few years ago, when besides the Norwood procedure or in some countries a neonatal transplantation the third option of “only supportive care” was frequently considered, some clinicians suggested recently that it is no longer acceptable for infants with this condition to be denied surgery. Refinements in operative technique and perioperative care are now largely responsible for an importantly improved outlook, with centres having survival up to 90 % for Norwood stage 1. However neonatal mortality in the subgroup of HLHS patients with intact or highly restrictive atrial septum remains high despite successful urgent septostomy (3) . In general, despite current advances, controversies continue to arise on the optimal treatment strategy for children with HLHS. 

References

1. Rhodes LA, Colan SD, Perry SB et al. Predictors of survival in neonates with critical aortic stenosis. Circulation 1991; 84: 2325-2335.

2. Tani LY, Minich LL, Pagotto LT et al. Left heart hypoplasia and neonatal aortic arch obstruction: is the Rhodes left ventricular adequacy score applicable? J Thorac Cardiovasc Surg 1999; 118: 81-6.

3. Vlahos AP, Lock JE, McElhinney DB et al. Hypoplastic left heart syndrome with intact or highly restrictive atrial septum. Outcome after neonatal transcatheter atrial septostomy. Circulation 2004; 109: 2326-2330.

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