Author: Melissa Colizza MD - CHU Saint-Justine, Montreal, Quebec
A 2-year-old boy with Shone’s complex, mild hypoplasia of the left ventricle, moderate mitral stenosis and moderate aortic regurgitation status-post balloon valvuloplasty of severe aortic valve stenosis is undergoing an elective Ross-Konno procedure and mitral valve repair. Which of the following factors is MOST likely associated with increased morbidity and mortality after biventricular repair of a borderline left heart disease?
Borderline left heart disease falls along the spectrum of hypoplastic left heart syndrome. It is characterized by the size of left-sided heart structures (aortic valve, mitral valve, LV end-diastolic volume) with z-scores of -2 to -5, as well as the presence of endocardial fibroelastosis (EFE).
The single ventricle pathway continues to have substantial mortality and morbidity including Fontan circulation failure with cyanosis and/or ventricular dysfunction as well as end-organ dysfunction, such as Fontan-associated liver disease, protein-losing enteropathy, plastic bronchitis and lymphatic dysfunction. In the past two decades, there has been increasing interest and development of surgical techniques to establish a two-ventricle circulation in patients who traditionally would have been palliated via the single-ventricle pathway. Currently, there is no consensus whether a “bad two-ventricle” repair is better than a “good single-ventricle” circulation, as long-term comparison data is unavailable.
In recent years, there have been increasing efforts to establish objective anatomic, physiologic, and hemodynamic criteria that could predict which patients with borderline left heart disease would be amenable to recruitment procedures to increase blood flow to the ventricle in order to stimulate growth and then allow for biventricular repair. Strategies to increase blood flow to the left ventricle include creating a fenestrated atrial septal defect, adding an additional source of pulmonary blood flow via a shunt, and resection of EFE tissue. Subsequent surgical decision making on whether to attempt biventricular repair depends on a comprehensive assessment based on multiple characteristics of the left heart structures and function including the following: 1) the size and structure of the mitral valve and its apparatus, 2) the size and function of the aortic valve, 3) the end-diastolic volume and pressure of the LV, 4) the apex-forming status of the LV, 5) the presence of EFE, and 6) the underlying anatomy of the congenital heart defect.
Although no single factor has been shown to predict the success or failure of biventricular conversion, there are some data that can inform the decision making process. A retrospective single-institution study assessing outcomes of 51 patients undergoing biventricular repair over a period of thirteen years from 2003-2015 by Herrin et al concluded that a pre-operative left ventricular end-diastolic pressure (LVEDP) ≥ 13mmHg and post-operative right ventricular systolic pressure (RVSP) ≥ three-quarters of the systemic systolic pressure, as well as the presence of ≥ moderate EFE, were associated with an increased likelihood of death, transplant or conversion to single ventricle physiology. Data from cardiac magneting resonance (CMR) imaging studies can also be of prognostic value. A CMR study of 32 patients with single ventricles undergoing biventricular repair concluded that a left ventricular end diastolic volume ≥ 45ml/m2 in hypoplastic left heart variants or ≥30ml/m2 in patients with double outlet right ventricle or atrioventricular canal defect were associated with a greater likelihood of success (Banka et al). These elements illustrate that, while size matters, it is the overall capacity of the left-sided circulation to accommodate a full cardiac output at low filling pressures that allows for a successful biventricular repair. In the event of a failed repair that results in diastolic dysfunction, left atrial hypertension and subsequent pulmonary hypertension, patients could become ineligible for conversion to single-ventricle physiology or for heart transplantation.
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