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How are congenital heart lesions repaired?
Repair or palliation of congenital heart disease attempts to establish normal physiology but cannot usually establish normal cardiovascular anatomy. Surgery may result in residual defects or in short- or long-term sequelae. True anatomic repair, in which further surgery is not antici-pated, occurs in ligation of a PDA or suture closure of an ASD. Closure of a simple VSD, resection of a coarctation of the aorta with end-to-end anastomosis, or the arterial switch operation for correction of TGA also result in nor-mal anatomy, but tend to result in late sequelae in some patients. Lesions in which anatomic repair is attempted but will result in residual lesions or requires use of prosthetic materials are repairs of TOF, atrioventricular canal defects, obstructive valvular lesions, any lesion requiring the inser-tion of a conduit between the ventricle and respective artery (usually the right ventricle and pulmonary artery), and any valve replacement.
In patients where anatomic repair is not feasible, surgi-cal correction is aimed at trying to establish normal cardio-vascular physiology. The initial repair of TGA by the Mustard or Senning operation results in redirection of blood flow at the atrial level (atrial switch). Pulmonary venous blood is directed to the aorta and systemic venous blood is directed to the pulmonary artery. This group of lesions also includes all patients whose cardiac malfor-mation results in only one functional ventricle that supports the systemic circulation. This heterogeneous group of lesions requires several staged surgical interven-tions until the final Fontan operation, which results in sep-aration of the two circulations without a pulmonary ventricle.
One of the most common sequelae following congenital heart surgery is rhythm abnormalities. Supraventricular dysrhythmias are the most common of these and can be life-threatening under certain conditions (e.g., atrial flutter in the post-Fontan patient). Supraventricular dysrhythmias are associated with a 2–8% incidence of sudden death. They are particularly common following repairs with extensive atrial suture lines and/or elevated atrial pressures. Atrial dysrhythmias may be tachycardias or bradycardias. They are often refractory to medical therapy and may require ablation or pacemaker insertion. Following the Senning or Mustard repair only 20–40% of patients are in sinus rhythm 5–10 years following surgery. Following Fontan repairs, performed with direct atrial to pulmonary anastomosis, there is at least a 30% incidence of atrial dysrhythmias. Newer surgical approaches, utilizing either a lateral tunnel or extracardiac conduits, diminish the incidence of late rhythm abnormalities. Atrial dys-rhythmias are also seen in 5–10% of patients following repair of a secundum ASD, particularly when repair is carried out at an older age.
Ventricular dysrhythmias, although less common in the postoperative patient, are frequently more significant since they may indicate an underlying residual defect and may be the harbinger of sudden death. The etiologies for development of ventricular premature beats include right ventriculotomy and/or resection, elevated intracavi-tary pressure associated with valvular stenosis, and cardiomyopathies with decreased diastolic function. The latter occurs following surgery if there was subopti-mal myocardial preservation during the procedure or when pressure and volume overload of the ventricle was present for a long time prior to corrective surgery, particularly if associated with a high hematocrit. On occa-sion, the stress of anesthesia and surgery may unmask an underlying rhythm disturbance. New ventricular extrasystoles observed during anesthesia in a patient with previous TOF repair should be brought to the cardiolo-gist’s attention so that appropriate follow-up can occur. TOF repair has the highest association of ventricular dys-rhythmias and sudden death occurring long after surgical repair, particularly in patients operated later in life or in earlier series. These patients may require implantation of a cardioverting defibrillator (AICD) to prevent this com-plication.
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