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SECTION XI - Complete Transposition of the Great Arteries
Part l - Background Information
Definition: There is atrioventricular concordance and ventriculoarterial discordance - i.e. the right atrium connects to the morphological right ventricle which gives rise to the aorta and the left atrium connects to the morphological left ventricle which gives rise to the pulmonary artery.
Approximately 2/3 of patients have no major associated abnormalities ("simple" transposition). Approximately 1/3 have associated abnormalities ("complex" transposition). The most common associated abnormalities are VSD and pulmonary/subpulmonary stenosis.
Part II - History and Management
Unoperated (simple) transposition is a lethal condition with 90% mortality in the first year of life. Thus nearly all patients seen as adults will have had intervention.
The most common surgical procedure in patients who are currently adults is the atrial switch operation in the form of a Mustard or a Senning procedure. Blood is redirected at the atrial level using a baffle (Mustard operation) or atrial flaps (Senning operation), achieving physiological correction, but the right ventricle continues to support the systemic circulation.
Now, the atrial switch operation has been supplanted by the arterial switch operation (Jatene), but few of these patients have yet become adults. Blood is redirected at the great artery level by switching the aorta and pulmonary arteries such that the left ventricle supports the systemic circulation. The coronary arteries are translocated to the neo-aorta (formerly the pulmonary artery). The tissue loss in the sinuses of the neo-pulmonary artery is made good with a pericardial patch.
In a small proportion of patients (<10%) who have VSD and pulmonary/subpulmonary stenosis, a Rastelli operation will have been done. Blood is redirected at the ventricular level (with the left ventricular outflow tunnelled to the aorta) and a valved conduit is placed from the right ventricle to the aorta. The left ventricle supports the systemic circulation.
Rarely, in patients with a large VSD and established pulmonary vascular disease, a palliative atrial switch operation will have been done to improve oxygenation. This is an atrial switch operation but the VSD is left open (or enlarged). These patients resemble Eisenmenger VSDs and should be managed as such. (See Eisenmenger Section XV).
Part III - Investigational Recommendations in Operated Patients
Since most patients will have had an operation, investigations are directed towards post-operative sequelae and will vary according to the type of operation performed.
All patients should have at a minimum:
- A thorough clinical assessment.
- ECG.
- Chest x-ray.
- Oximetry at rest and possibly with exercise.
- Echo-Doppler examination by an appropriately trained individual to detect baffle obstruction or baffle leak, AV valve regurgitation, and to assess systemic ventricular function and subpulmonary obstruction.
- A Holter monitor because of the high prevalence of sick sinus syndrome and atrial arrhythmias and possible ventricular arrhythmias in older patients.
- TEE if there is inadequate visualization of the intra-atrial baffle on the TTE.
- Nuclear cardiology assessment of myocardial perfusion (if ischemia is suspected), or of ventricular function. Radionuclide angiography and MRI usually report better RV function than does echocardiography.
- MRI to evaluate baffle function (obstruction or leakage) and ventricular volumes, shapes and function.
- Heart catheterization including coronary angiography if there are doubts about additional lesions, and if surgical re-intervention is planned; or if adequate assessment of the hemodynamics is not obtained by non-invasive means.
- Exercise testing to evaluate functional capacity (including) heart rate and blood pressure response, and to assess whether arrhythmias may be provoked.
- Echo-Doppler examination by an appropriately trained individual to assess right ventricular outflow tract obstruction (the most common problem), ventricular function, neo-aortic root dilation, possible neo-aortic valve regurgitation, and coronary ostial status (although the last may be difficult to see in adults).
- Exercise stress testing periodically because of possible coronary ischemia due to reimplantation of the coronary arteries.
- Holter monitoring if arrhythmia is suspected. (The long- term outcome following the arterial switch is unknown, but arrhythmias appear to be substantially less common than after the atrial switch operation).
- Nuclear cardiology assessment of myocardial perfusion periodically because coronary ischemia is possible due to reimplantation or redirection of the coronary arteries.
- Coronary arteriography if ischemia is documented on non-invasive testing.
- Complete heart catheterization if adequate assessment of the hemodynamics is not obtained by non-invasive means or additional lesions are suspected.
- MRI to assess right ventricular outflow tract obstruction.
- Echo-Doppler examination by an appropriately trained individual to assess right ventricle-to-pulmonary artery conduit stenosis/regurgitation, subaortic stenosis, aortic regurgitation, ventricular function and AV valve regurgitation. Assessment of the conduit gradient may be difficult but it is usually possible to measure the right ventricular systolic pressure from the tricuspid regurgitation jet and this may be a useful surrogate in the absence of pulmonary hypertension.
- MRI to assess the issues above.
- Heart catheterization to determine the severity of conduit stenosis or regurgitation and the status of the distal pulmonary arteries if inadequate information is obtained from non-invasive testing and surgery is contemplated.
- Echo-Doppler examination by an appropriately trained individual to detect baffle obstruction or baffle leak, AV valve regurgitation and to assess systemic ventricular function.
- A Holter monitor because of the high prevalence of sick sinus syndrome and atrial arrhythmias.
- CBC, ferritin, clotting profile, renal function and uric acid (See Management of Cyanotic Patients Section XVI).
Part IV - Indications for Re-intervention
The following situations may warrant re-intervention following the atrial switch procedure:
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The following situations may warrant intervention following an arterial switch procedure:
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The following situations may warrant re-intervention following the Rastelli procedure:
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Part V - Surgical/Interventional Options
| Patients who require re-intervention should be treated by ACHD cardiologists and congenital heart surgeons with appropriate experience. | ||
The following are possible intervention strategies:
- Surgery may be necessary for baffle stenosis or leakage in patients with an atrial switch procedure. Balloon dilation of SVC or IVC stenosis is an option but success is limited in adults. Pathway obstruction is less common after the Senning operation than after the Mustard operation and is usually amenable to balloon dilation. SVC stenosis is usually benign, unlike IVC stenosis which may be life threatening. Stent insertion may be considered for SVC or IVC stenosis.
- Patients with an atrial switch procedure and severe systemic (tricuspid) AV valve regurgitation may need valve replacement if systemic ventricular function is adequate or possibly PA banding to improve tricuspid regurgitation by altering septal geometry.
- Patients with severe systemic (right) ventricular dysfunction and/or severe systemic (tricuspid) AV valve regurgitation following an atrial switch procedure may require consideration of heart transplantation. A conversion procedure to an arterial switch following retraining of the left ventricle with a pulmonary artery band may be considered but this is experimental with little data available in adults (169-172).
- Patients who have had an arterial switch operation may require coronary artery bypass grafting (preferably with arterial conduits) for myocardial ischemia.
- Patients who have had an arterial switch operation may require augmentation of the right ventricular outflow tract for outflow tract obstruction.
- Patients who have had a Rastelli operation will need conduit replacement at some time.
- Patients who have had a Rastelli operation may need left ventricle-to-aorta baffle revision because of obstruction.
- Patients who have had a palliative atrial switch operation may require consideration of heart-lung transplantation.
- The role of afterload reduction with ACE inhibitors or -blockers to preserve systemic right ventricular function is as yet unknown but a major trial to address this question will soon be underway. In the meanwhile, many patients are being treated empirically with ACE inhibitors.
Part VI - Surgical/Interventional Outcomes
The overall survival of patients who have had an atrial switch procedure is approximately 65% at 25 years, with increased likelihood of survival with later year of operation. Patients who have "simple" transposition have a better survival (80% at 25 years) than those with "complex" transposition (45% at 25 years). Causes of death include sudden unexpected (presumed arrhythmic) death, heart failure and baffle obstruction.
The long-term survival data following the arterial switch is just beginning to emerge (169). Neo-aortic root dilation, neo-aortic valve regurgitation, right ventricular outflow tract obstruction and coronary artery stenosis/occlusion are recognized complications.
Following the Rastelli operation repeated conduit changes will be necessary and there is a risk of deteriorating ventricular function. Sustained monomorphic ventricular tachycardia and supraventricular tachycardias may occur.
Patients who have had a palliative atrial switch probably have a prognosis similar to Eisenmenger VSD but specific information is lacking. Quality of life is generally improved for a time, however.
Part VII - Arrhythmia
Atrial flutter (intra-atrial re-entry) occurs in 20% of atrial switch patients by age 20 and progressive sinus node dysfunction and/or junctional rhythm is seen in half of the patients by that time (156,160,161, 173,174).
Transvenous pacemaker insertion for symptomatic bradycardia or anti-tachycardia pacing for some atrial arrhythmias may be required. In patients with an atrial switch operation, transvenous pacing leads must traverse the upper limb of the atrial switch to enter the morphological left atrium and/or left ventricle. Active fixation is required.
| Transvenous pacing for bradyarrhythmias following intra-atrial repair for transposition can be done when needed (15-20% of adult patients) by experts. Baffle leak must be ruled out by TEE before transvenous pacemaker insertion to reduce the risk of paradoxical embolism and morphological assessment of the systemic venous pathway should be done to rule out a stenotic systemic channel. Epicardial leads are a good alternative when venous access is troublesome. | ||
Trans-catheter ablation procedures for intra-atrial re-entry tachycardia/atrial flutter and AV nodal re-entry is feasible, with an initial rate of success in these pts of 60-70% (175). Ablation in these patients is more complex and associated with a lower cure rate both because of the complex anatomy and the previous surgical scars; ablation should be undertaken by an electrophysiologist with appropriate training/experience in this population.
Part VIII - Pregnancy
Pregnancy in women with a normal functional class following atrial switch operation is usually well tolerated. Worsening of systemic right ventricular function during or shortly after pregnancy, however, is reported in about 10% of patients (176,177). ACE inhibitors should be stopped before pregnancy occurs.
Part IX - Follow Up
| All patients should have regular cardiology follow up by an ACHD cardiologist. Endocarditis prophylaxis is recommended. | ||