Congenital heart defects

Patient with defect size > 6.5mm almost always require surgical closure. Failure to thrive with signs of left ventricular failure (i.e. fatigue with feeding) and significant left to right shunt leading to recurrent chest infections are also indications for surgical closure. Medical therapy in moderate to large defects is usually started to improve symptoms before surgery. Percutaneous device closure is not done in cases of associated anomalies such as aortic valve prolapse and insufficiency which commonly occur in supracristal VSD, due to long term risk of endocarditis.

Apical rumble reflects increased flow through mitral valve due to left to right shunting.

Eisenmenger syndrome is an end result of chronic, large left to right shunt. It is a consequence of the pathologic changes caused by chronically increased pulmonary artery pressure leading to increased pulmonary vascular resistance (PVR) so that the shunt becomes bidirectional or reversed. Correction of underlying cardiac disorder is contraindicated once eisenmenger syndrome is established.

Anesthetic management of a patient with ventricular septal defect is tailored to minimize the excessive reduction in PVR and increase in systemic vascular resistance, in order to reduce the magnitude of shunt. Oxygen and low Paco2, both are potent pulmonary vasodilator and therefore, not optimal for defects with high pulmonary flow.

Tetralogy of Fallot is a cyanotic congenital heart disease characterized by ventricular septal defect with right to left shunt, right ventricular hypertrophy, infundibular pulmonary stenosis and overriding to aorta. Chest X-rays shows classic boot-shaped heart or “coeur en sabot” appearance.

Patient is having an episode of hypercyanotic “Spell” characterized by paroxysmal cyanosis and hyperpnoea which can be initiated by crying, feeding or defecation. These events causes increase in oxygen demand and hypoxemia which results in decrease in SVR. These episodes usually resolve spontaneously but can be progressive and fatal in rare cases. Episodes can be terminated by intravenous beta-blocker. Inj. Phenylephrine increases SVR, while Inj. Sodium bicarbonate corrects peripheral metabolic acidosis with return to normal SVR.

The murmur is due to RVOT obstruction and length and volume of the murmur vary inversely with the degree of obstruction to antegrade pulmonary blood flow. In patients with TOF, VSD is non-restrictive and does not produce a murmur. Aortopulmonary collateral vessels produces continuous murmur best heard at the back.

Patients with history of hypercyanotic spells are particularly vulnerable during induction and emergence of anesthesia. Endogenous catecholamines induces infundibular muscle spasm and can precipitate spell. There is a increased need of preoperative sedation and postoperative analgesia to minimize catecholamine release. Although, anesthetic agents which increase sympathetic discharge such as ketamine and pancuronium are often used for induction of cyanotic patients, should be used with caution in patients with frequent episodes of hypercyanotic spells.

Diagnostic catheterization in TOF is required in cases of associated lesion like anomalous origin of left anterior descending artery from right coronary artery and to delineate pulmonary blood supply and presence of collateral vessels. Blalock-Taussig shunt is palliative procedure for intensely cyanotic TOF patients and involves direct anastomosis of subclavian artery with a branch of ipsilateral pulmonary artery. It helps in increasing pulmonary artery size and improved haemodynamics following complete repair. Chronic hypoxia leads to polycythemia in TOF patients which can cause renal, cerebral and pulmonary thrombosis.

Tetralogy of fallot is most commonly associated with Digeorge Syndrome and chromosome 22q11 deletion. Down’s sysdrome is most commonly associated with atrio-ventricular canal defect.