QRS duration in Fontan circulation in adults: A predictor of aerobic capacity

BACKGROUND:The univentricular circulation after a Fontan procedure is characterized by an abnormal cardiorespiratory response being attributable to an inability to increase stroke volume during exercise. In congenital heart disease a broad QRS complex has been related to increased intracardiac volume and mass being associated with poor ventricular function and prognosis. OBJECTIVES:This study investigated the relation between the width of the QRS complex and parameters of cardiorespiratory response in adult patients after a Fontan procedure. METHODS:Clinical data and parameters of cardiorespiratory function of 56 patients (15 women, 41 men, mean age 23.7+/-6.4 years, mean age at operation 10.0+/-7.5 years) were related to the width of the QRS complex. RESULTS:In the whole group the mean QRS duration was 115+/-23 ms. A QRS complex >or= 120 ms was present in 23 patients. These patients were characterized by significantly older age at operation (13.0+/-9.3 versus 7.9+/-5.1; p<0.05). Compared to individuals with smaller QRS complexes they showed a decreased oxygen uptake (PeakVO(2): 21.6+/-5.2 versus 27.7+/-6.6 ml/kg/min; p<0.001), work rate (1.6+/-0.5 versus 2.0+/-0.5 W/kg, p<0.05), maximum blood pressure (p<0.001) and increase in blood pressure (p<0.05). Univariate analysis showed a significant correlation between PeakVO(2) and several other parameters of cardiorespiratory exercise testing (work rate,O(2)-pulse, increase in heart rate and blood pressure, maximum heart rate and blood pressure), maximum enddiastolic diameter of the systemic ventricle, age at operation. Multivariate regression analysis identified QRS duration as the only independent predictor of PeakVO(2) (p=0.05). CONCLUSION:In a Fontan circulation a broad QRS complex is a negative predictor of cardiorespiratory function. Early Fontan operation may be beneficial in terms of exercise capacity.