Late Repair and Reoperations in Adult Congenital Heart Disease

Cyanosis

Cyanosis in CHD patients has been shown to be an independent predictor of early mortality after cardiac surgery because of the combined effects on hemostasis as well as renal and ventricular function. Secondary erythrocytosis and the preceding hyperviscosity are well established in patients with CHD and are thought to be major contributors to the coagulation abnormalities often observed in these patients. In addition, chronic cyanosis leads to the development of profuse acquired collateral vessels that are friable and difficult to coagulate. Difficulties in perioperative hemostasis associated with chronic cyanosis may be compounded by extensive suture lines and often long bypass times, leading to decreased platelet activity, a reduction in the number of platelets, and, with fibrinolysis, the consumption of coagulation factors.

The following measures are taken to assist in postoperative hemostasis:

• Administration of aminocaproic and transexamic acid

• Meticulous hemostasis during sternotomy and dissection

• Administration of platelets, fresh frozen plasma, and cryoprecipitate guided by laboratory estimation (It is important that these products are available immediately after protamine administration.)

• Use of continuous ultrafiltration during cardiopulmonary bypass and modified ultrafiltration after the completion of cardiopulmonary bypass, along with a cell saver to raise the hematocrit

• Use of fibrin glue for application to suture lines

Prudence in achieving hemostasis is particularly important in the cyanotic population because they often do not have normal cardiac reserve and postoperative bleeding can lead to hemodynamic instability and compromise outcome. The importance of meticulous postoperative surgical hemostasis therefore cannot be overemphasized for these patients.

Renal dysfunction is a well-recognized complication of long-standing cyanotic CHD. The most prominent feature of cyanotic nephropathy is glomerular damage. Risk factors for postoperative acute renal failure in cyanotic patients are the existence of preoperative glomerulopathy, longer cardiopulmonary bypass time, and surgery on complex cardiac lesions, which predisposes to low cardiac output postoperatively. Therefore renal status in cyanotic patients should influence the surgical plan and renal function should be studied preoperatively with glomerular filtration rate (GFR) calculation, 24-hour urine collection, and, if necessary, a renal scan. Moreover, the maintenance of adequate cardiac output and hence renal blood flow and meticulous fluid balance postoperatively is essential to reduce the risk of postoperative renal failure.

Patients with chronic cyanosis also have an increased propensity to postoperative dysfunction due to myocardial injury.

This propensity to myocardial injury is multifactorial:

• The cyanotic patient is more sensitive to the damaging effects of free oxygen radicals.

• The acquired collateral circulation may involve the coronary arterial tree and result in washout of a cardioplegic solution.

• Increased pulmonary venous return may lead to ventricular distention.

• The presence of ventricular hypertrophy adds to difficulties in providing adequate myocardial preservation.

These difficulties are overcome by the more frequent administration of a cardioplegic solution, appropriate venting of the heart to prevent overdistention and, in selected cases, the use of low-flow hypothermic cardiopulmonary bypass.

Ventricular Hypertrophy

Ventricular hypertrophy in complex CHD may involve the left or right ventricle (RV), the latter in some cases being the systemic ventricle. In either case, low cardiac output may be experienced postoperatively due to poor ventricular compliance. A relationship between myocardial injury and restricted RV physiology has been demonstrated in children undergoing repair of tetralogy of Fallot (TOF).

Cardiac Arrhythmias

Cardiac arrhythmias, both ventricular and supraventricular , may occur before and late after the correction of CHD. Any postoperative arrhythmias may be responsible for the sudden onset of severe low-cardiac-output states. These may be supraventricular, ventricular, or bradyarrhythmias, the last due to temporary malfunction of the sinoatrial or atrial ventricular node. Arrhythmias must be evaluated immediately and treated promptly. The surgeon must ensure the presence of functioning atrial and ventricular pacing wires to assist in arrhythmia management. Atrial arrhythmias occurring late postoperatively are being linked to increased morbidity and mortality. The efficacy of ablation as an adjunct to surgical repair has been demonstrated in both the Ebstein anomaly and atrial septal defect. Although the majority of secundum atrial septal defects are amenable to transcatheter device closure, adult patients older than 40 years of age with preoperative flutter or fibrillation should be considered for concomitant arrhythmia intervention at the time of closure of an atrial septal defect by device or conventional surgery.

Supraventricular Tachycardia

Supraventricular tachycardia can originate from the left or right atrium. Atrial fibrillation usually originates from the left atrium or the pulmonary veins and should be managed by surgical left atrial ablation (maze procedure) at the time of surgical intervention. Moreover, in the presence of a severely dilated left atrium and where there is a high probability of recurrent arrhythmia, closure of the atrial appendix is desirable. The majority of arrhythmias originating within the right atrium are represented mainly by reentrant circuits, which may be atrioventricular tachycardias, atrial tachycardias, or, more rarely, atrioventricular nodal reentry tachycardias. Our current thinking is that these should be treated by mapping and ablation in the catheterization laboratory before surgery. The advantage of such an approach is that catheter ablations may abort the need for targeting the arrhythmia at surgery and thereby reduce the bypass time and operative risk. It also reduces the risk of arrhythmia during induction and anesthesia.

Ventricular Tachycardia

When patients present with episodes of documented (or strongly suspected) ventricular tachycardia , they should undergo mapping and ablation, ideally before surgery. Reentry ventricular tachycardia can occur around the right ventricular outflow tract (RVOT) patch, the ventricular septal defect (VSD) patch, or among the scars commonly present in the RV free wall. If ventricular tachycardia cannot be induced by electrophysiological study, the site of the ventricular tachycardia can be assessed by pace mapping, following which an ablation line is made from the presumed site of tachycardia to a nonconductible area (e.g., the pulmonary valve in the case of an infundibular outflow tract patch or between a RV free wall scar and a RVOT patch). After surgery, a subgroup of patients who have poor right and/or left ventricular function with evidence of extensive ventricular fibrosis on gadolinium-enhanced cardiac magnetic resonance imaging (MRI) as well as a marked prolongation of QRS duration (>180 ms) should be considered for an implantable cardiac defibrillator (ICD). In addition, patients who had inducible ventricular tachycardia without successful ablation should be considered for an ICD. Moreover, there is a particular subgroup of patients who are better studied in terms of stratification of the risks of cardiac events: adult patients with operated TOF should undergo ICD implantation based on the Khairy score for arrhythmic sudden death. In cases of intermediate risk (Khairy score between 3 and 5), the authors’ opinion is that gadolinium enhancement on MRI should be taken in account.

Postoperative Lung Damage

Depending on the cardiac patient’s background, the lungs can be involved in abnormal processes that may lead to increased postoperative morbidity and mortality. These include the presence of parenchymal maladaptive remodeling, increased lung fibrosis, pulmonary hypertension, and reduced lung capacity. The degree of compromise is mainly dependent on the primary diagnosis, age at first reparative surgery, type of systemic-to-pulmonary shunt if present, and any structural thoracic abnormalities. In the light of these considerations, it is important to evaluate respiratory status with formal laboratory lung function studies and chest x-rays. In addition, a computed tomography (CT) scan will demonstrate parenchymal structure, the presence of interstitial lung disease, the presence of small collaterals, and the anteroposterior thoracic distance. Such information can help in estimating the respiratory support likely to be required postoperatively and reduce ventilation time, which is known to correlate with postoperative morbidity and mortality. Another common complication of cardiac surgery in adults with CHD is lung reperfusion injury. Cardiopulmonary bypass has been shown to initiate a systemic inflammatory response that can lead to pulmonary dysfunction ranging from subclinical functional changes to acute respiratory distress syndrome. Several potential therapeutic techniques have been applied such as the use of heparin-coated circuits and continuous hemofiltration. Additional care must be taken when surgery has resulted in increased pulmonary blood flow; meticulous fluid balance with maintenance of cardiac output is required in these patients.

Cardiac Catheterization

The invasive assessment of adults with CHD and the need for coronary angiography before surgery are dictated by the patient’s age, presence of risk factors, presence of angina or electrocardiographic evidence of ischemia, reduced ventricular function, and history of suspected or confirmed coronary artery disease. There has been a consensus for routine assessment with selective coronary scan for patients older than 40 years referred for CHD surgery. Ultrafast CT angiography is an alternative option that is particularly suitable for patients with very large aortic roots, in whom selective coronary cannulation may be challenging or risky.

Coronary arteriography may reveal:

• Τhe presence of atheromatous coronary artery disease.

• Αnomalous origin of the left anterior descending from the right coronary artery. It is particularly important to be aware of this anomaly in any reoperation involving the RVOT. Surgical adhesions may prevent identification of this vessel at the time of operation.

• Anomalous origin of the left coronary artery from the pulmonary trunk.

• Congenital coronary arteriovenous fistula, which may present with a continuous murmur in adulthood.

Left and right cardiac catheterization may show:

• Εlevated diastolic pressure in the right or left ventricle

• The presence of pulmonary hypertension and, in particular, its differentiation in pre- and postcapillary types

• The presence and clinical relevance of residual anomalous pulmonary venous return

Preoperative investigations are aimed at providing a complete understanding of a patient’s anatomic and pathophysiological status and allow precise and appropriate surgical planning.