Complications
Hypercyanotic spells present with dyspnoea and severe cyanosis.
They result from contraction of the infundibular musculature creating increased right ventricular outflow tract obstruction and increased shunting of de-oxygenated blood from the right ventricle across the ventricular septal defect to the systemic circulation.
Treatment of hypercyanotic spells is targeted towards relaxing the pulmonary obstruction and increasing systemic vascular resistance to increase the blood flow through the pulmonary circulation.
Preoperatively, patients with TOF have a ventricular septal defect (VSD), which allows communication of venous blood in the right heart with the systemic circulation. Normally, a thrombus in the venous circulation that embolises will be trapped in the pulmonary vasculature. However, the VSD provides communication such that a thrombus can paradoxically cross the VSD and lodge in an arterial bed, causing ischaemia.
Patients with known communication between the right and left cardiac chambers should have precautions taken when using intravenous catheters, as an air bubble in the intravenous tubing can embolise to the systemic circulation, causing end-organ ischaemia.
Prophylactic anticoagulation is not commonly given to patients with TOF. However, the possibility of venous thrombi should be carefully considered and treated aggressively if identified.
A single-centre study of 100 consecutive adult patients with TOF repaired in childhood who underwent cardiac magnetic resonance imaging found poor right ventricular and left ventricular systolic function to be independent risk factors for impaired clinical status.[45]
While short-term results of surgical repair are good, the long-term results are limited by the development of arrhythmias.
A retrospective analysis of 66 patients undergoing surgical repair of TOF between 1960 and 1993 found 28% to have no ventricular arrhythmias, 51% to have minor ventricular arrhythmias, 10.5% to have non-sustained ventricular tachycardia, and 9% to have sustained ventricular tachycardia or ventricular fibrillation.[41]
Serial ECGs have been performed to monitor the width of the QRS complex as an arrhythmogenic risk factor.[42] If the QRS complex is noted to widen, further electrophysiological evaluation may be necessary. Some experts recommend periodic Holter monitors to screen for arrhythmia. Exercise testing is used by some clinicians.
Ventricular arrhythmias may be managed with anti-arrhythmic drugs, transcatheter or surgical ablation, and/or implantation of an implantable cardioverter-defibrillator.[43]
In the past decade, atrial arrhythmias have been increasingly recognised as a common long-term morbidity in repaired TOF. One retrospective study of adults with TOF repaired in childhood found that one third of patients had documented atrial arrhythmias, including sinus node dysfunction, atrial fibrillation, atrial flutter, and supraventricular tachycardia.[44]
Atrial arrhythmias are treated with transcatheter ablation or surgical ablation at the time of pulmonary valve replacement.[43]
Sudden cardiac death from ventricular tachycardia or ventricular fibrillation is the most common cardiac cause of death in patients with repaired TOF.[37]
It is believed to be associated with progressive right ventricular failure.
Ten years after surgery, the risk of sudden cardiac death increased from 0.06% per year to 0.2% per year.[38]
One retrospective analysis of patients undergoing surgical repair in 1 state in the US between 1958 and 1996 found that 11 out of 445 patients with repaired TOF died of sudden cardiac death.[39]
One retrospective study of 793 adult patients who underwent surgical repair for TOF in childhood at 6 different institutions found moderate to severe pulmonary regurgitation in 100% of patients who died of sudden cardiac death.[40]
Some patients with minimal pulmonary stenosis may have symptoms of heart failure. Furosemide is the most commonly used diuretic for symptoms of congestive heart disease. Care should be taken, as over-diuresis may precipitate hypercyanotic spells.
Congestive heart failure is not a commonly recognised long-term complication of surgically repaired TOF.
One single-centre study of 100 adults with TOF surgically repaired in childhood found 48% to be in New York Heart Association (NYHA) class I, 40% in class II, and 12% in class III.[45]
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