Ventricular Afterload and Ventricular Work in Fontan Circulation

Abstract

Background-Recent studies have indicated that there are inherent limitations associated with Fontan physiology.However, there have been no quantitative analyses of the effects of right heart bypass on ventricular afterload, hydraulic power, and resultant overall hemodynamics. Methods and Results-During routine cardiac catheterization, aortic impedance and ventricular hydraulic power were determined, both at rest and under increased ventricular work induced by dobutamine, in 17 patients with Fontan circulation, 15 patients with a single ventricle whose pulmonary circulation was maintained only by Blalock-Taussig shunts, and 13 patients who had normal 2-ventricle circulation. Both vascular resistance (nonpulsatile load on the ventricle) and pulsatile components of ventricular afterload (represented by low-frequency impedance) were significantly higher in the Fontan group than in the other groups (PϽ0.01), and this was associated with decreased cardiac output in the Fontan patients. In addition, hydraulic power cost per unit forward flow was 40% lower in the 2-ventricle circulation than in the single-ventricle circulation, suggesting lower ventricular efficiency in single-ventricle circulation attributable to the lack of a pulmonary ventricle. Furthermore, in the Fontan group, ␤-adrenergic reserve was markedly decreased because of a limited preload reserve. Conclusions-Fontan physiology is associated with disadvantageous ventricular power and afterload profiles and has limited ventricular reserve capacity. Thus, to improve the long-term prognosis of patients after Fontan surgery, future research should be conducted into medical interventions that can overcome these limitations inherent in Fontan circulation.

Arterial Hemodynamics in Patients After Kawasaki Disease

“…Previous reports have confirmed the validity of this method for measurement of instantaneous aortic volume flow. 13,15 Data were digitalized at 500 Hz on a personal computer and stored for subsequent offline analysis. Blood samples taken at the level of the inferior vena cava were obtained via the catheter and were centrifuged.…”

“…9 -11 Aortic input impedance integrates functional and structural changes in systemic vascular properties, providing comprehensive information about the state of the vascular bed that includes both frequency-independent static (resistance) and frequency-dependent dynamic (stiffness and wave reflection) components. 12,13 In the present study, we examined aortic input impedance to test our hypothesis that arterial hemodynamics are abnormal after KD.…”

Fontan “Ten Commandments” Revisited and Revised

“…This criterion, although arbitrary by itself, has been even more inappropriately applied to univentricular hearts, despite the fact that studies have shown that peak systolic gradients \20 mm Hg can cause significant diastolic dysfunction [23,41] [37]. Is it reasonable, therefore, to accept any arch gradient in a univentricular heart, which is already exposed to increased afterload [32,38]?…”

Management of the Fontan circulation in the adult patient

“…In the palliated univentricular circulation, the systemic circulation is pulsatile and the pulmonary circulation is not, the circulations run in series and the non-pulsatile pulmonary circulation causes a large reflective wave of resistance leading to an increased afterload. (6) In order to overcome this afterload the single ventricle hypertrophies.…”

“…(86)(87)(88) By adult life the gains in ventricular function are largely lost with around a third of reported patients having moderate or severe ventricular function. (89) There are many plausible theories as to why late ventricular function occurs, with increasing systemic vascular resistance, due to abnormal vascular tone, (90) endothelial dysfunction, (91)(92)(93) and the abnormal resistances encountered by the pulmonary and systemic circulations running in series (6) all probably playing a part. The onset of significant valvular incompetence and the onset of atrial arrhythmias are both poorly tolerated.…”