eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiology

Single Ventricle: Follow-up

Author: Alvin J Chin, MD, Professor of Pediatrics, Division of Cardiology, The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine
Contributor Information and Disclosures

Updated: Jul 15, 2009

Follow-up

Further Inpatient Care

• Admit patients with single ventricles for testing and surgical intervention.

Further Outpatient Care

• Following each stage of surgical reconstruction, echocardiographic and Doppler evaluation of hemodynamic adequacy should be performed.
• After the Fontan operation, monitor for hepatic and biliary dysfunction (ie, measure prothrombin time [PT], gammaglutamyltranspeptidase [GGT], and factor VIII),²² supraventricular arrhythmias (Holter monitoring), short stature, and protein-losing enteropathy (monitor total protein and albumin levels). If possible, perform morphologic assessment of the systemic and pulmonary venous pathways and the pulmonary artery architecture, as well as measurement of cardiac index, using MRI or cardiac catheterization.
• Should effusive complications, which are common in the early period after a Fontan procedure, recur months or years later, a comprehensive search for a surgically correctable cause should be undertaken. Examples of such correctable etiologies are late-onset pulmonary venous obstruction and thrombosis of the left pulmonary artery.
• Only after mechanical obstructions are ruled out should a classic protein-losing enteropathy workup be initiated.

Inpatient & Outpatient Medications

• The medical treatment of postoperative patients with supraventricular arrhythmias is frequently complex because many patients who have undergone a Fontan operation have sinus node dysfunction and can only be safely administered antiarrhythmic agents if a pacemaker is placed first. Surgical therapy for atrial tachyarrhythmias appears to be preferred over medical therapy.
• Various "maintenance drug regimens" are empirically used for patients who have undergone a Fontan operation. These include the following:
  • No medications
  • Furosemide
  • Spironolactone
  • ACE inhibitor
  • Sildenafil
  • Digoxin
  • Warfarin (for the first 3 mo after fenestrated Fontan)
  • Combinations of the above medications

Transfer

• Transfer may be required for further diagnostic evaluation and surgical intervention.

Complications

• Pleural effusions, pericardial effusions, ascites
  • Long considered the most agonizing early postoperative complication after completion Fontan, thoracic and abdominal effusions often persisted for weeks and frequently impaired cardiac output. Before the early 1990s, these complications threatened to preclude the application of Fontan's principle to the vast majority of patients with single ventricle.
  • Although the molecular and cellular basis of this complication remains a mystery, surgeons have begun using various less-than-complete Fontan operations as their final stage.²³ The partial hepatic vein exclusion variation used by Lecompte and then by Norwood has largely been abandoned because more than 80% of patients developed intrahepatic venous collaterals that resulted in increasing right-to-left shunts.
  • Hence, the less-than-complete Fontan operation most widely used since the late 1990s is the fenestrated Fontan operation proposed by Laks. Effusive complications are greatly reduced following the fenestrated Fontan (lateral tunnel or extracardiac conduit). However, arterial oxygen saturation is usually in the high 80s or low 90s, rather than the mid 90s seen after nonfenestrated Fontan.
• Atrial tachyarrhythmias
  • This is the most prevalent of the numerous late complications following the various modifications of the Fontan operation and may be the heralding sign of hemodynamic deterioration. The basis for this complication is probably multifactorial,²⁴ and its treatment can be complex because of the frequent coexistence of sinus node dysfunction. Surgical therapy appears to be superior to medical therapy.²⁵
  • Current hypotheses for the etiology of the sinus node dysfunction center on surgical trauma to portions of the sinus node region or its blood supply.
  • As an alternative to the hemi-Fontan operation, use of the so-called bidirectional Glenn operation, followed subsequently by extracardiac conduit²⁶ (rather than the lateral tunnel) placement, has failed to reduce the frequency of sinus node dysfunction. This may be because the demarcation of the sinus node region is not macroscopically evident; thus, attempts to avoid it (such as the bidirectional Glenn) may have been unsuccessful.
  • Because the onset of atrial tachyarrhythmia episodes is frequently preceded, if not invariably preceded, by months or years of atrial bradycardia, prophylactic atrial pacing may possibly postpone the emergence of these arrhythmias. Because of the technical challenges of atrial pacing in infants, this proposal has not yet been the subject of a randomized clinical trial.
• Hepatic and biliary dysfunction^22,27
  • Liver dysfunction may actually be the underlying etiology for several of the complications listed below (eg, thromboembolism, varices and other venous-to-venous collaterals, thrombocytopenia)
  • Biliary sludge is the most common finding on gallbladder ultrasonography.
  • Elevated factor VIII, prolonged PT, and elevated GGT are the most sensitive indicators. 
• Thromboembolism
  • Venous, but not arterial, thrombosis occurs in nearly 10% of survivors of the fenestrated Fontan operation. The cause of this complication is unknown. Sites can include the pulmonary arteries and the cerebral veins.²⁸ Subnormal cardiac output, subnormal intracardiac pulsatility of blood flow, and altered hepatic production of components of endogenous thrombolytic pathways have all been proposed as possible etiologies. Hepatic dysfunction, as measured by prothrombin time and galactose elimination half-life, is the rule.
  • Thrombi have been observed in both the pulmonary venous side of the "lateral tunnel" baffle and the systemic venous side. The presence of a fenestration allows thrombi in the systemic venous circulation to gain access to the systemic arterial circulation.
  • Aspirin is often prescribed as prophylaxis for venous thrombosis following fenestrated Fontan, but it appears to be ineffective in this setting. Warfarin and Lovenox have not gained wide acceptance for prophylaxis in children with Fontan circulation.
• Protein-losing enteropathy
  • Manifesting as diarrhea, poor appetite, or sometimes simply as growth failure, protein-losing enteropathy occurs in at least 10% of long-term survivors of nonfenestrated Fontan procedures.
  • The cause of this usually devastating complication is unknown. For those with little or no fenestration, fenestration creation (or dilation and stenting) appears to be the most consistently successful palliation, with the improvement sometimes lasting longer than a decade. Atrial pacing has succeeded in at least 2 cases.²⁹ Other proposed remedies, including steroids and heparin, have succeeded in individual cases but have more numerous adverse effects such as osteopenia. Reduction of both CD4+ and CD8+ T lymphocytes is observed; disproportionate reduction of the CD4+ subset results in a reversal of the CD4+/CD8+ ratio. Immunoglobulin G (IgG) levels and, to a lesser extent, immunoglobulin A (IgA) levels are diminished.³⁰
  • Not observed in the pre-1980 era (when Fontan-type operations were rarely performed), protein-losing enteropathy is thus a result of surgically created cavopulmonary/atriopulmonary circulatory arrangements and is not merely a result of being born with a single ventricle heart.
• Persistent discrete or long-segment narrowing of the left pulmonary artery
  • In the program of staged surgery to reach a fenestrated Fontan, distortions of the left pulmonary artery are frequently difficult to entirely abolish, even at the time of the final stage.
  • The importance of identifying cases of Fontan-to-one-lung circulation³¹ lies in their vulnerability to the hemodynamic consequences of ipsilateral pulmonary insults. Moreover, 50% of patients with Fontan-to-one-lung circulation develop protein-losing enteropathy, arguing strongly that protein-losing enteropathy is a sequela of Fontan hemodynamics.³²
• Formation of venous collaterals and varices
  • Patients with single ventricle and the coexistence of interrupted inferior vena cava still have hepatic venous blood that drains to the pulmonary venous side of the circulation after a Kawashima variation of the Fontan procedure.
  • Collaterals can occasionally form, allowing venous blood from the upper part of the body to eventually reach the pulmonary venous side of the circulation in this subset of patients with single ventricle, as well as in others.
  • The increased right-to-left shunt can be identified by monitoring either pulse oximetry or hemoglobin levels. 
  • Bronchial wall varices have been observed, possibly due to high superior vena cava pressure.
  • Esophageal varices occur in patients with hepatic dysfunction and portal hypertension.
• Low exercise capacity³³
  • Although individual exceptions have been observed, the exercise capacity of patients who survive the Fontan procedure, even those with fenestrated variants, is subnormal.
  • The resting cardiac index is about 70-80% of normal. Disadvantageous ejection efficiency is present, combined with elevated pulsatile and nonpulsatile components of ventricular afterload.⁵
• Short stature
  • This is observed in patients who survive the Fontan operation even in the absence of documented protein-losing enteropathy.
  • The molecular and cellular basis of this complication is unknown; however, low bone-specific alkaline phosphatase appears to increase when cardiac index is augmented. This suggests that reduced osteoblastic function from subnormal bone perfusion may be the culprit.¹⁷
  • Whether exogenous growth hormone ameliorates the subnormal growth (but with acceptable incidence of adverse effects) is not known.
• Formation of pulmonary arteriovenous malformations
  • This complication of the hemi-Fontan operation and its variants appears to largely resolve after the performance of a less-than-complete Fontan operation (of the lateral tunnel, extracardiac conduit, or hepatic vein exclusion varieties).
  • Contrast echocardiography appears to be a highly sensitive method of identifying pulmonary arteriovenous malformations.³⁴
• Plastic bronchitis³⁵
  • This is characterized by the development of mucinous bronchial casts.
  • Palliation by fenestration creation has been reported.³⁶
• Formation of systemic-to-pulmonary arterial collaterals
  • Systemic artery-to-pulmonary artery collaterals can carry as much as 40% of the total ventricular output.
  • Whether this is due to the arterial desaturation caused by the fenestration is not yet known.³⁷
• Thrombocytopenia³⁸ : Whether this is due to deficient thrombopoietin, which is provided by the liver as well as by the kidney, is not yet known.³⁹

Prognosis

• More than one half of patients should survive 20 years. Patients with even moderate atrioventricular valve regurgitation have a demonstrably poorer outcome.

Patient Education

• Because the outcome of various modifications of Fontan operation includes a monotonically increasing prevalence of serious sequelae, discussion with families about prognoses are necessarily lengthy.
• If the initial identification of single ventricle is made in utero, then the possibility of pregnancy termination may also be introduced to family members.
• Finally, the family should confront the possibility that cardiac transplantation may eventually be needed, even if the staged approach to achieve a fenestrated Fontan is the initial strategy adopted.

Miscellaneous

Medicolegal Pitfalls

• Failure to recognize symptoms and signs of coexistent arch obstruction
• Failure to recognize inadequately relieved subaortic stenosis, aortic stenosis, or both

Special Concerns

• Although treatments for single ventricle (which, as stated earlier in this article, does not include the entity of hypoplastic left heart syndrome) have been refined over the last 30 years, they have not convincingly improved upon the limited palliations offered before 1971. Because of this, extra caution is advised in the initial discussions with the family.
  • Unlike hypoplastic left heart syndrome, in which the staged approach to reach a cavopulmonary circulation is clearly superior to performing only the first stage (Norwood procedure), the vast majority of patients with single ventricle have a morphologic left ventricle (LV), do not present in extremis, and are relatively stable over many years once initial palliation, including a systemic–to–pulmonary arterial shunt, is completed and a pulmonary/systemic flow ratio of between 1.5 and 2.0 is achieved.
  • Whether the cavopulmonary circulation matches or surpasses this quality of life over a 30-year period is still an open question.⁴⁰ The long-term effect of a mean systemic venous pressure greater than 10 mm Hg is unknown in the pediatric population.

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