- In longstanding unrepaired TOF, right ventricular hypertension induces fibrosis leading to RV systolic and diastolic dysfunctions and ventricular arrhythmias.
- Neonate with TOF should be carefully assessed by echo to see if the PS is so severe that ductal patency is needed. If this is the case, give PGE1 infusion and do early surgery.
- Cyanotic spells can occur in acyanotic TOF also.
- Treatment of cyanotic spells includes oxygen, volume expansion, sedation with morphine or ketamine and vasopressors like phenylephrine.
- Patients with relative anemia are at more risk of cerebrovascular accidents and hypercyanotic spells.
Interventional catheterization procedures
Palliation of cyanosis by RVOT stent placement or balloon valvuloplasty. This avoids need for BT shunt which may cause pulmonary artery distortion.
Coil embolization of aortopulmonary collaterals.
- Postoperative- For residual pulmonary artery obstruction- ballooning and stenting.
- This is done via median sternotomy.
- Atrial route- This is the preferred route. The VSD is closed by a Dacron patch. RVOT obstruction is resected. Atrial route was earlier done only for patients with coronaries crossing the RVOT. Now it is done for other patients also as it avoids the need for ventriculotomy.
- Right ventriculotomy- A vertical incision is made over the infundibulum. RVOT obstruction is relieved. VSD is closed by a Dacron patch. RVOT is patched with pericardium. If the pulmonary annulus is hypoplastic (Z score preoperatively and visual impression of the surgeon intraoperatively), the initial incision is extended onto the pulmonary artery. A transannular patch is placed. A monocusp pericardial valve may be placed to avoid pulmonary regurgitation.
- Combined atrial and transpulmonary approach- avoids need for ventriculotomy.
- AP collaterals- These are coiled prior to surgery to avoid steal phenomenon during cardiopulmonary bypass which causes neurologic sequelae. If it constitutes the sole blood supply to the lung, it should be incorporated into the final repair.
- Initial palliative BT shunt is not preferred due to PA distortion, ventricular volume loading and the surgical risks of an additional thoracotomy. Primary repair is directly done. But palliation may need to be done in severe PA hypoplasia and aberrant LAD form RCA.
- Blalock Thomas Taussig shunt and central shunt are used now. Waterston shunt and Potts shunt are not used now. Modified BTT shunt is the most commonly used one. It is done opposite to the side of the aortic arch. Shunt size in newborn is usually 3.5 to 4 mm.
- Early primary repair is not associated with higher incidence of early complications or late reintervention compared to late repair. Also, primary repair is not associated with more reintervention for residual obstruction compared to staged repair. Hence, early primary repair is preferred though repair in first 3 months of life increases intensive care morbidity.
- Hospital survival for repair is 100% even for early surgery. 20 year survival after primary repair is 98% for TOF with PS and slightly lower for TOF with primary atresia.
- In TOF with PS, after primary repair, at 2 years 25% needed reoperation usually for residual obstruction in RV or PA. The indication for reoperation in older patients is different and is residual VSD.
- Early repair may be associated with less long term incidence of arrhythmias, ventricular dysfunction and cognitive dysfunction.
Sudden death and arrhythmias
- Incidence of sudden death is 1.2% at 10 years, 2.2% at 20 years, 4% at 25 years and 6% at 30 years.
- Sudden death is not more in patients who underwent surgery before 80s.
- Ventricular arrhythmias are more in patients who undergo surgery at older age. These patients are predisposed to ventricular arrhythmias before surgery itself due to their older age and surgery does not decrease the chance of ventricular arrhythmias.
- Ventricular arrhythmias are more in patients with PR and in those with RV dilation.
- EP studies are not clearly shown to predict sudden death in patients with ventricular arrhythmias.
- Other predictors of sudden death are significant PR, sustained ventricular arrhythmias, QRS duration more than 180 msec and LV dysfunction.
- Other arrhythmias noted in the long term are sinus dysfunction, atrial flutter , atrial fibrillation and supraventricular tachycardia. The incidence of supraventricular tachycardia is 10% at 12 years after repair.
Residual defects and hemodynamic abnormalities
- Branch PA stenosis
- After shunt procedures.
- After RVOT patch, due to compression by the redundant patch.
- Treated by ballooning or stenting- the complications include aneurysms, stent migration and stent thrombosis.
- Redundant RVOT patch should be surgically revised.
- Membranous subaortic stenosis- uncommon late complication.
- Coronary to RV fistula
- Pulmonary regurgitation
- All patients have PR by echo.
- Some have audible PR.
- Pan-diastolic PR with end-diastolic velocity of 1 m/s indicates mild PR and good pulmonary valve anatomy.
- PR signal ending before the end of diastole indicates that pulmonary valve function is poor and that the RV is stiff. This occurs due to equalization of PA diastolic pressure and RV diastolic pressure in diastole itself.
- PR may occur due to increased pulmonary arterial impedance which is due to either stenosis of main or branch pulmonary arteries or elevated LA pressure due to causes like LV dysfunction. If branch PA stenosis is the cause of PR, it may be treated by interventional catheterization. If LV dysfunction is the cause of PR, it may decrease with treatment of the LV dysfunction.
- For significant PR, pulmonary valve replacement (homograft) will be needed.
- Tricuspid regurgitation
- Present in many.
- Not audible unless RV pressure is elevated.
- May need repair.
- Aortic dilation
- Aorta is dilated in TOF patients after repair. This dilation may progress.
- Avoid isometric exercise and high blood pressure.
- Serial monitoring for enlargement and development of AR is needed.
- Reduced exercise capacity is present in patients with PA stenosis, PR or RV dysfunction.
- Prophylaxis is needed in unoperated patients, palliated patients, in repaired patients for 6 months and in repaired patients with prosthetic valves.