SECTION XIV - Single Ventricles

Part I - Background Information

Anatomy

Patients with single ventricles either have an "anatomically" single ventricle made up of a single pouch of indeterminate origin or, more commonly, have a "functionally" single ventricle with one well-formed ventricle accompanied by a second underdeveloped or rudimentary ventricle. The atrium can be situs solitus, inversus or ambiguous. The atrioventricular valves guarding the inlet of the univentricular heart can consist of either two separate valves (double inlet left ventricle [DILV], double inlet right ventricle [DIRV]) one patent valve and one atretic valve (tricuspid atresia [TA], mitral atresia [MA]) or of a common type (unbalanced AV septal defect). The well-developed ventricular chamber can be of the left ventricular type with an anterosuperior right ventricular pouch or less commonly, of a right ventricular type with a posterior left ventricular pouch (DIRV). The ventriculo-arterial connection can be concordant or discordant, or the great arteries can arise from the same ventricle and be patent or stenotic (209,210).

 
Part II - History and Management of Unoperated Patients

Patients with an "ideal" anatomy (i.e. a functionally single morphological left ventricle) with a "well balanced" circulation (i.e. some degree of pulmonic stenosis to avoid excessive pulmonary blood flow) may achieve late survival with good ventricular function, exercise capacity and minimal symptoms (211). The prognosis of all patients with unoperated univentricular hearts, however, is poor with a median survival of 14 years (death rate of 4.8% per year) with the majority being symptomatic with cyanosis and exercise intolerance (212).

 
Part III - Diagnostic Workup

An initial diagnostic workup should:

• Assess the anatomy and document the situs of the atria, status of the inlet AV valves (number, patency and presence or absence of straddling), morphology of the main ventricular chamber as well as position and patency of the great arteries.
• Document the etiology of cyanosis (decreased pulmonary blood flow, arteriovenous mixing or pulmonary hypertension) and assesses pulmonary resistance.
• Identify other factors affecting the clinical condition of the patient (see complications and clinical sequelae of cyanotic heart disease).

The diagnostic workup should include at a minimum:

• A thorough clinical assessment.
• ECG.
• Chest x-ray.
• Echo Doppler evaluation by an appropriately trained individual.
• Oximetry at rest, and perhaps with exertion (if the saturation at rest is more than 90%).
• CBC, ferritin, clotting profile, renal function and uric acid (See Management of Cyanotic Patients Section XVI).

The diagnostic workup may require:

• TEE to visualize the anatomy in terms of atrial situs, AV connections, ventricular type and great arteries connections as well as patency. (Caution should be exercised with sedation).
• MRI to visualize the anatomy, assess ventricular sizes and function, and evaluate associated lesions.
• Nuclear angiography to quantitate ventricular function.
• Cardiopulmonary testing to evaluate functional capacity objectively, the degree and basis for exertional limitation, and exercise desaturation.
• Heart catheterization to determine pulmonary artery pressures and resistances if these have not been adequately defined by other investigations.

 
Part IV - Indications for Intervention

Significant functional limitation, resting saturation < 90%, dilated (volume overloaded) systemic ventricle, and paradoxical embolism.

 
Part V - Interventional Options

Aortopulmonary shunt. Rarely done as the sole intervention any more.

Bi-directional Glenn. Usually performed in infancy as a staged procedure before the Fontan procedure (1 ventricle repair) or performed as a "definitive palliation" when patients are too high risk for Fontan surgery. It provides a controlled source of pulmonary blood flow while volume unloading the systemic ventricle (213).

Bi-directional Glenn + additional pulmonary blood flow. An additional source of pulmonary blood flow via the pulmonary artery through a pulmonary artery band or native pulmonary stenosis, or through a Blalock-Taussig shunt is sometimes added in conjunction with a bi-directional Glenn procedure in order to increase oxygen saturation at the expense of an increased volume load on the systemic ventricle (214).

1 ventricle repair. Especially when the rudimentary pulmonary ventricle is < 30% of its normal volume, the Fontan procedure will allow systemic venous return to enter directly into the pulmonary circulation, bypassing the pulmonic ventricle or outlet chamber (see Fontan section XIII).

1½ ventricle repair. Sometimes when the rudimentary pulmonic ventricle is between 30-80% of its normal volume, the IVC blood flow will be permitted to return to the pulmonary circulation via the pulmonic ventricle whereas the SVC blood will return directly to the pulmonary circulation via a bi-directional Glenn procedure (215).

2 ventricles repair. In some instances, when the pulmonic ventricle is > 80% of its normal volume, a biventricular repair or ventricular septation may be feasible. Straddling of the AV valves and transposition of the great arteries may complicate this type of repair.

Transplantation. Heart transplantation for ventricular failure or heart and lung transplantation for ventricular failure with pulmonary hypertension should be considered when the patient is symptomatic and further palliation/repair is not possible.

 
Part VI - Interventional Outcomes

Aortopulmonary shunt. Of the patients that survived to adulthood, there is at best a 50% survival at 20 years follow up (216,217). Systemic ventricular dilation and failure, as well as the development of arrhythmias (mainly atrial fibrillation/flutter), occur commonly.

Bi-directional Glenn. There is a 50% survival at 20 years follow up (217,218). Progressive cyanosis may be due to a greater contribution of IVC blood flow compared to SVC blood flow with somatic growth (as seen in childhood) or, as is typical in adults, from the development of pulmonary arteriovenous fistulae.

Bi-directional Glenn + additional pulmonary blood flow. No long-term studies are available. By increasing volume loading on the systemic ventricle the additional pulmonary blood flow may confer an actual survival disadvantage in these patients (212).

1 ventricle repair. There is an 81% survival at 10 years for "the perfect" Fontan candidate (204) compared to 60% survival at 10 years for all Fontan patients (205). Complications after a Fontan procedure include atrial arrhythmias, thrombus formation, protein losing enteropathy [especially if the Fontan procedure was performed in adults (219)] as well as systemic ventricular failure and progressive AV valve regurgitation. (see Fontan section XIII)

1½ ventricle repair. No long-term studies are available. The main long-term complication of a bi-directional Glenn procedure, namely progressive formation of pulmonary AV fistulae, has not been documented at 4 years follow up following a 1½ ventricular repair (220).

2 ventricle repair. A complex biventricular repair (needing valved conduit or complex intraventricular tunnel) may not be preferable in the short or intermediate term to a simple 1 or 1½ ventricular repair (221).

Transplantation. The outcome of heart transplantation in adult patients with congenital heart disease approaches that of adult patients without congenital heart problems with a 1-year survival of 79% and a 5 year survival of 60% (222). Outcome of heart and lung transplant is less with a 1 year survival of 60-80% and a 10 year survival of 30% (223,224).

 
Part VII - Arrhythmias

Shunt. Patients palliated with an aortopulmonary shunt will develop significantly more atrial fibrillation or flutter at 30 years follow up than patients palliated with a cavopulmonary shunt (35% vs. 15%). Progressive systemic ventricular dysfunction has been linked to the development of atrial arrhythmias (217).

1 ventricle repair. See Fontan section XIII.

 
Part VIII - Pregnancy

Shunt. Pregnancy is often well tolerated in a single ventricle patient with good functional class, good ventricular function and an oxygen saturation > 85%. (See Management of Cyanotic Patients Section XVI). The risk of paradoxical emboli in these patients is high and meticulous attention should be paid to avoid deep venous thrombosis in these patients.

1 ventricle repair. See Fontan section XIII.

 
Part IX - Follow Up

Yearly follow up by an ACHD cardiologist is recommended. Yearly clinical visit to follow functional status and oxygen saturation as well as a yearly echocardiography to assess systemic ventricular function, semilunar valve stenosis and AV valve regurgitation should be performed. CBC, ferritin, clotting profile, renal function and uric acid should be obtained on a yearly basis as well (See Management of Cyanotic Patients Section XVI). Endocarditis prophylaxis is recommended.