Transcript Fontan Circulation
Fontan Circulation
Leilani Mullis, MD George Sheplock, MD December 19, 2007
Fontan Circulation
• • • • • • • Fontan Procedure Fontan Physiology Patient Selection Post-Fontan Complications Fontan Outcomes Post-Fontan Pregnancy Anesthesia Implications
Fontan Procedure
• • • First described in 1971 by Francis Fontan It is used to treat complex congenital heart diseases when bi-ventricular repair is not possible: – Tricuspid atresia – Pulmonary atresia – Severe pulmonic stenosis – Single ventricle – Hypoplastic left or hypoplastic right heart The above conditions rely on one functional ventricle to maintain systemic and pulmonary circulations that are not connected in series but in parallel
Fontan Procedure
• • • A single ventricle parallel circuit creates 2 major disadvantages: – Systemic arterial desaturation at rest – Chronic volume overload to the ventricle Without surgical intervention, there is about a 90% mortality before age 1 A completion Fontan is the definitive palliative step in a series of surgeries used to improve oxygenation and cardiac function
How to achieve a Fontan Circuit
• • At birth, it is impossible to create a Fontan circulation: – PVR is elevated for several weeks – SVC and IVC veins and pulmonary arteries may be too small A staged approach allows the body to adapt progressively to the different hemodynamic conditions
How to achieve a Fontan Circuit
• Neonatal period – Achieve unrestricted flow from the heart to the aorta – Improve limited flow to the lungs – Achieve unrestricted blood return to the ventricle – The infant is allowed to grow for several months • Pulmonary vasculature will develop more • • • • PVR will stabilize The heart will be subjected to chronic volume overload Ventricular function may deteriorate Expect mild progressive desaturation of the infant
How to achieve a Fontan Circuit
Normal Heart Single Ventricle – BT Shunt http://www.cincinnatichildrens.org/health/heart-encyclopedia/anomalies/sv.htm
How to achieve a Fontan Circuit
• • At age 4-12 months – The superior vena cava will be connected to the pulmonary artery (Glenn) This will decrease the volume load to the heart – The patient will remain cyanotic as the desaturated blood from the IVC is still allowed to flow to the aorta
How to achieve a Fontan Circuit
Single Ventricle – BT Shunt Single Ventricle – Bidirectional Glenn http://www.cincinnatichildrens.org/health/heart-encyclopedia/anomalies/sv.htm
How to achieve a Fontan Circuit
• At 1-5 years of age – The Fontan circuit is completed by connecting the IVC to the pulmonary artery Single Ventricle – Bidirectional Glenn Single Ventricle – Completed Fontan http://www.cincinnatichildrens.org/health/heart-encyclopedia/anomalies/sv.htm
Fontan Modifications
Fontan surgical techniques: Classical atriopulmonary connection (A), Lateral tunnel (B), and extracardiac conduit (C) d'Udekem, Y. et al. Circulation 2007;116:I-157-I-164
Copyright ©2007 American Heart Association
Fontan Physiology
• • • The sub-pulmonary ventricle is bypassed Systemic venous return is diverted directly into the pulmonary arteries – Goal is to provide adequate pulmonary blood flow and cardiac output with minimal elevation in venous pressure Systemic and pulmonary venous returns are separated: – Cyanosis is relieved – Volume loading on the ventricle is significantly reduced
Patient Selection
• • • After a Fontan operation, the left atrial pressure and the transpulmonary gradient must be low in order for the repair to be successful Pre-op cardiac requirements: – Unobstructed ventricular inflow – Unobstructed ventricular outflow – Reasonable ventricular function Pre-op pulmonary requirements: – Good sized pulmonary arteries – Near normal pulmonary vascular resistance – Unobstructed pulmonary venous return
Fontan Circulation Complications
• Complications after Fontan repair are common and are related to: – Increased venous pressure – Increased venous congestion – Chronic low cardiac output
Fontan Circulation Complications
• • • • • • • • • • Early and late mortality Mild to moderate exercise intolerance Residual cardiomegaly Ventricular dysfunction Rhythm and conduction disturbances Hepatomegaly Lymphatic dysfunction with protein losing enteropathy Systemic venous thrombi Ascites Peripheral edema
Fontan Circulation Complications
• Ventricular Function – All post-Fontan hearts have a ventricle that is dilated, hypertophic and hypocontractile – Dysfunction may be caused by the congenital malformation itself, previous surgery or the abnormal hemodynamic changes encountered through the various stages of palliation
Fontan Circulation Complications
• • Ventricular Function – During the first months after birth, the ventricle will always be volume overloaded • • • Ventricular dilation and spherical reconfiguration Cardiac overgrowth Eccentric hypertrophy After the Fontan completion, some normalization will occur
Fontan Circulation Complications
• • • • • Ventricular function evolves from being volume loaded and overstretched to overgrown and underloaded Systolic and diastolic dysfunction are common Reduced preload is the dominant factor contributing to poor ventricular function Inotropes, afterload reducers, vasodilators and B-blockers are generally ineffective Pulmonary vascular resistance will control cardiac output – Improving pulmonary blood flow will improve cardiac output
Fontan Circulation Complications
• Predisposition to atrial dysrhythmias – Up to 40% of patients 10 years post-op – Most commonly intra-atrial re-entry tachycardia or atypical atrial flutter – Survival depends on ventricular contractility and vascular resistance – Safest treatment is immediate DC cardioversion – Long term treatments include medication, ablation, pacemaker, Fontan take-down
Fontan Circulation Complications
• Predisposition to coagulopathies – Thrombosis is more likely in patients with low CO and venous stasis – Increased incidence of coagulation factor abnormalities because of hepatic congestion • • • Protein C Protein S ATIII deficiency – Anticoagulation of all patients is controversial
Fontan Outcomes
• • • Despite the abnormal circuit, most patients with a Fontan circulation can lead a nearly normal life, including mild to moderate sport activities More than 90% of hospital survivors are NYHA functional class I or II Patient’s remain slightly desaturated with values in the low 90s
Fontan Outcomes
• University of Melbourne – 305 consecutive Fontan operations between 1980-2000 – 10 hospital deaths (3%) none after 1990 – 20 year survival was 84% (257 pts in long term follow up) – Freedom from Fontan Failure was 70% at age 20
Fontan Outcomes
• University of Melbourne – Fontan failure was defined as: • • • • Death Fontan Take-down Transplantation NYHA functional class III or IV
Fontan Outcomes
• Boston Children’s Hospital – Intermediate-term follow up study – 220 pts aged 11 mo to 32 years – Lateral tunnel Fontan between 1987 - 1991 – 91% survival at 10 years – 87% Freedom from failure at 10 years
Post-Fontan Pregnancy
• • Normal pregnancy – 30-40% increase in CO by 24 weeks – 30-40% increase in circulating blood volume – Decreased SVR – Myocardial oxygen consumption increases 20% – Heart rate increases 15-20% Fontan patients may develop “right heart” failure symptoms – Atrial arrhythmias, peripheral edema, ascites – Increased risk of venous thrombosis/PE
Post-Fontan Pregnancy
• • • • Of 39 completed pregnancies reported in the literature, 16 patients experienced a decline in NYHA functional status Overt heart failure occurred in 4 patients Spontaneous abortion rate 50% (normal population 10-15%) Increased risk of premature delivery
Anesthetic Implications
• • • • • Multi-disciplinary pre-operative approach is mandatory SBE prophylaxis Anticoagulation Maintain adequate intravascular volume Ventilation – Spontaneous ventilation provides significantly increased pulmonary blood flow when compared to positive pressure ventilation – Avoid hypoxemia and hypercarbia (increase PVR) – If positive pressure ventilation is necessary, low rates, short inspiratory times, low PEEP and moderately elevated tidal volumes (~15/kg) are recommended
Review
• • • • The Fontan procedure is considered palliative and enables survival for several decades In a Fontan circulation, systemic venous return is diverted directly into the pulmonary arteries Complications after Fontan are related to increased venous pressure, increased venous congestion, and chronic low cardiac output Post-Fontan anesthetic goals include maintaining adequate preload and minimizing increases in pulmonary vascular resistance
References
• • • • • D’Udekem, Y., et al. The Fontan procedure: Contemporary techniques have improved long-term outcomes. Circulation. 2007. 116: I-157 – I-164 Gersony, D., et al. Management of the postoperative Fontan. Progress in Pediatric Cardiology. 2003. 17: 73-79 Gewillig, M. The Fontan Circulation. Heart. 2005. 91: 839-846 Redington, A. The physiology of the Fontan Circulation. Progress in Pediatric Cardiology. 2006. 22: 179-186 Walker, F. Pregnancy and the various forms of Fontan Circulation. Ed. Heart. 2007. 93: 152-154