Systolic and diastolic function of the univentricular heart

Abstract

Current surgical palliation for the patient with functional single ventricle provides long-term survival for the majority of patients. Nevertheless, because of the increased hemodynamic load, cardiac reserve is intrinsically reduced by these interventions. Preservation of ventricular systolic and diastolic function is therefore particularly important for this patient population. This article reviews the published data concerning ventricular systolic and diastolic function in patients after early palliation with pulmonary artery banding or aortopulmonary shunts and after superior and total cavopulmonary anastomoses. There are significant intrinsic limitations to the applicability of these data, since they are invariably limited to descriptive studies of the outcome for a constantly evolving treatment strategy. The majority of these studies involve patients managed according to a management scheme that has now been abandoned. Until the pulmonary and systemic circulations are separated, a volume load is imposed on the ventricle that carries a long-term risk of progressive loss of myocardial contractility. As in the case with other forms of ventricular volume loading, the risk for and the pace of deterioration is proportional to the magnitude of the volume overload. This observation, coupled with the demonstration that the superior cavopulmonary anastomosis can be successfully performed by 6 months of age, has resulted in dramatic reduction in the duration of volume overload to which these patients are generally exposed. Despite the reduced incidence of impaired myocardial contractility that has been realized, the total cavopulmonary anastomosis circulation still imposes an increased workload on the single ventricle. Data on late outcome in patients managed with early volume-reduction therapy are not yet available. Although there is considerable concern about the relative durability of single ventricles of right ventricular morphology, the available data on this issue are contradictory. The energy requirements to fill the heart are particularly critical in patients who have previously undergone a Fontan operation because of the absence of a pulmonary pumping chamber. Compared to systolic function, the diastolic ventricular and myocardial outcome in these patients has been evaluated much less frequently and generally by less reliable methodologies. The utility of noninvasive techniques in the measurement of relaxation and compliance in single ventricle hearts is unproven and highly suspect, particularly when compounded by chronic volume overload or acute preload reduction. The available data do not document a verifiable impairment in ventricular or myocardial compliance, although there are suggestive data indicating that impaired relaxation may be present. Again, late outcome with regard to diastolic function are not yet available in the patients who have been treated according to present day management practices.