Noncardiac Surgery in Adult Congenital Heart Disease

General Issues

In acquired heart disease, the risks for adverse events related to noncardiac surgery depend on the urgency and type of procedure. In the American College of Cardiology/American Heart Association (ACC/AHA) guidelines, an emergency procedure is defined as one in which life or limb is threatened if surgery does not take place within less than 6 hours, and an urgent procedure requires surgery within 6 to 24 hours. There is usually little or no time for extended clinical evaluation; management strategy is dictated by the emergency. For matched patients, the risk attributed to any emergency surgery is greater than to a comparable elective procedure, and is often substantial. For example, the mortality risk of an emergency laparotomy is in the range of 15%, whereas the mortality rates for common major elective abdominal surgeries range from 1% to 4%.

Surgery should be postponed if possible in patients with major predictors of cardiovascular risk until the patient has been further evaluated and stabilized. These predictors include the following:

• Decompensated heart failure (New York Heart Association [NYHA] functional class IV or worsening/new-onset heart failure)

• Significant arrhythmias (high-grade atrioventricular block, symptomatic or newly recognized ventricular arrhythmias, symptomatic bradycardia, or supraventricular arrhythmias with ventricular response >100 beats per minute)

• Severe obstructive valvular disease (symptomatic or asymptomatic with definite evidence of severe stenosis)

• Unstable angina pectoris

• Myocardial infarction within the past 30 days and residual myocardial ischemia

For patients without such major predictors of risk, additional risk stratification should take into account the type of the proposed surgery . Surgical interventions can be broadly divided into those imparting low risk (<1% risk of a major adverse cardiac event [MACE]), intermediate risk (1% to 5% risk of a MACE), or high risk (>5% risk of a MACE). A MACE is defined as death or myocardial infarction within 30 days. Risk estimates for specific noncardiac surgeries are listed in Table 15.1 .

In the absence of major predictors of cardiovascular risk, low-surgical-risk procedures can be carried out without further risk stratification.

The patient’s functional capacity plays an important role in risk stratification. When exercise capacity is poor (<4 metabolic equivalents [MET]; inability to climb two flights of stairs or walk up a hill) or unknown, major cardiovascular predictors of risk and the nature of the surgical procedure are the main predictors of the rate of cardiac complications. When functional capacity is high (>10 MET), the prognosis of noncardiac surgery is excellent in spite of identified cardiovascular predictors of risk.

Several risk indices may be used to analyze the relationship between clinical characteristics and perioperative cardiac morbidity and mortality. Some of these are available as bedside risk calculators and can be downloaded as apps for smart phones or tablets (eg, http://www.riskcalculator.facs.org ). These risk calculators use data derived from the general population and have not been validated in the ACHD population. Nevertheless, all risk models support the importance of comorbid conditions in increasing risk. Common sense posits that this applies also to ACHD patients, in addition to risks that are unique to the ACHD population.

Comorbid Conditions

Comorbid conditions complicate perioperative cardiac management and increase the anesthetic risk. Added risk accrues from the following conditions:

• Obstructive or restrictive pulmonary disease, which places the patient at risk of perioperative respiratory complications. Lesions that are dependent on a low pulmonary vascular resistance, such as Ebstein anomaly, severe pulmonary regurgitation following repair of tetralogy of Fallot, Glenn shunt, and Fontan circulation, will in particular be adversely affected by hypoxemia, hypercapnia, and major acid-base disturbances. If significant pulmonary disease is suspected, preoperative lung-function testing including response to bronchodilators should be considered.

  Some ACHD patients will have restrictive lung physiology due to chest wall deformities and previous surgical interventions. Severity of restriction correlates with a surgical intervention at an early age and with the number of prior chest incisions, particularly if the patient has had both thoracotomy and sternotomy. Although pulmonary restriction may not significantly impair the ability to ventilate the patient intraoperatively, it may impair the ability to wean from the ventilator postoperatively.

• Diabetes mellitus , which increases the likelihood of significant coronary artery disease. Established protocols for management of diabetes mellitus exist in all surgical programs and need not differ in CHD patients.

• Renal dysfunction, which can complicate perioperative fluid management, especially in a patient with heart failure, and is not uncommon in ACHD patients. Serum creatinine was measured in 1102 patients attending one large ACHD clinic from 1999 to 2006 and glomerular filtration rate was calculated. Renal dysfunction was mild in 41% of patients and moderate or severe in 9%.

• Hematologic considerations. As a response to chronic hypoxemia, cyanotic patients have secondary erythrocytosis. The associated reduced plasma volume and other factors lead to a relative deficiency in vitamin K–dependent clotting factors, fibrinogen, and platelets. As a consequence such patients are at increased perioperative risk of both thrombosis and bleeding. Preoperative phlebotomy is inappropriate unless there are extreme symptoms of hyperviscosity because it promotes iron deficiency with microcytosis and is an independent risk factor for stroke, thrombosis, and hemoptysis. Hydration prior to surgery to compensate for the fasting state is particularly important in patients with secondary erythrocytosis to forestall dehydration-mediated exacerbation of hyperviscosity.

• Hepatic dysfunction. Patients with severe pulmonary regurgitation following repair of tetralogy of Fallot, with Fontan palliation for single ventricle and with severe forms of Ebstein anomaly are likely to have sustained elevation of systemic venous pressure, hepatic congestion, and other manifestations of right heart failure. Although they have differing anatomic diagnoses, hepatic dysfunction is common to all. The Mayo End-stage Liver Disease (MELD) score predicts short-term survival in cirrhosis, modified as the MELD-XI score to account for warfarin use. MELD-XI scores were retrospectively evaluated in a cohort of 96 ACHD patients with a previous Fontan procedure (73 were >18 years of age) and compared with control patients with cirrhosis due to hepatitis C. Fontan patients exhibited a distribution of MELD-XI scores similar to patients with established liver cirrhosis due to hepatitis C infection.

Adult Congenital Heart Disease: Specific Risks

Certain defects, pathophysiologic sequelae, and prior therapies unique to or often seen in the ACHD patient increase risk at noncardiac surgery in addition to the risks defined by the usual comorbid conditions previously discussed. These risks should also be considered during preoperative workup and perioperative management.

• Pulmonary hypertension (PH). Pulmonary arterial hypertension (PAH) due to chronic systemic-to-pulmonary shunts is a major perioperative risk factor, although not as difficult to manage as idiopathic PAH. PAH associated with CHD can be divided into four subgroups :

  • 1.

    Eisenmenger syndrome (see the section Cyanotic CHD )

  • 2.

    PAH associated with moderate to large systemic-to-pulmonary shunts (see the section Systemic-to-pulmonary shunt ).

  • 3.

    PAH with small/coincidental defects

  • 4.

    PAH after correction of the inciting defect

• In groups 3 and 4, the clinical picture is similar to that found in idiopathic PAH. In addition, ACHD patients can have PH due to left heart disease, because of valvular disease (regurgitant systemic AV valve, aortic regurgitation, or stenosis) or a failing systemic ventricle. Management is critically dependent on the underlying cause(s). For example, a patient with a longstanding left-to-right shunt and PAH may respond to pulmonary vasodilators, whereas a patient with a failing systemic ventricle and PH may need inotropic support or systemic afterload reduction and would likely deteriorate if given a pulmonary vasodilator.

• Cyanotic CHD and other situations in which the Qp:Qs is dependent on the ratio of pulmonary to systemic vascular resistance. The anesthesiologist should target the patient’s room air saturation at rest rather than “normal” oxygen saturation. Neuraxial (spinal and epidural) and general anesthetic agents can dramatically alter the ratio of pulmonary to systemic vascular resistance. Manipulations directed toward augmenting systemic arterial saturation may exacerbate an existing shunt or increase the pulmonary blood flow at the expense of systemic oxygen delivery. The balance of resistances and informed consideration of the hemodynamic consequences of possible anesthetic interventions should be reviewed with an ACHD cardiologist.

• Systemic ventricular dysfunction is managed by applying considerations similar to those applied in acquired dilated cardiomyopathy. Strategies may include inotropic support and/or afterload reduction that is attained pharmacologically or by virtue of the chosen anesthetic technique, for example, epidural anesthesia.

• Severe obstructive valvular disease or conduit obstruction. In patients with severe outflow tract stenosis and noncompliant ventricles, rapid volume infusion may result in an inordinate rise in filling pressure, provoking pulmonary edema or right-sided heart failure. Loss of sinus rhythm and synchronized presystolic atrial contraction may lead to a fall in cardiac output because of reduced presystolic ventricular filling. Blood flow through a stenotic orifice is relatively fixed, hence profound bradycardia will lower cardiac output more than otherwise anticipated. Hypovolemia or venodilation will lead to a fall in preload not easily tolerated by a hypertrophied, pressure-loaded, noncompliant ventricle. To address these issues, relief of severe outflow tract obstruction should be considered before elective surgery, unless the expected risk of the cardiac repair exceeds the risk of adverse events during noncardiac surgery.

  Analogous considerations apply to patients with severe ventricular inflow stenosis. In particular, tachycardia decreases diastolic ventricular filling time and is poorly tolerated. Also, in patients with mitral stenosis, PH can complicate the perioperative course.

  Obstructive valvular disease can sometimes be associated with increased bleeding tendency due to a form of acquired von Willebrand syndrome.

• Fontan physiology . The following factors contribute to cardiac output in patients with a Fontan circulation and are goals toward which management should be directed during noncardiac surgery:

  • Adequate central venous pressure

  • Low pulmonary vascular resistance

  • Atrioventricular synchrony

  • No outflow tract obstruction

  • Low afterload for the systemic ventricle

  • Adequate performance of the “pulmonary pump”

  Surgical and anesthetic techniques should be selected that will achieve as many of these goals as possible and they must continue to be considered in planning of the postoperative recovery and step-down care (see the section Perioperative Management ).

• Systemic-to-pulmonary shunt. Patients with simple unrestricted shunts and normal or low pulmonary vascular resistance will have a left-to-right shunt, and pulmonary blood flow will exceed systemic blood flow. High inspired oxygen concentrations lower pulmonary vascular resistance, which may convert a well-tolerated shunt such as a 2:1 shunt to a poorly tolerated 4:1 or 5:1 shunt. Conversely, a profound drop in systemic vascular resistance or a sudden elevation in pulmonary vascular resistance may lead to reversal of a left-to-right shunt leading to right-to-left shunting and systemic hypoxemia. Another mechanism for shunt reversal is the circumstance of a collapsed lung during a thoracotomy, which acutely raises pulmonary vascular resistance.

Adult Congenital Heart Disease Team

ACHD cardiologists, congenital heart surgeons, cardiac anesthesiologists, and critical care physicians form the ACHD team. This team regularly deals with ACHD patients and has a special understanding of the unique physiology of such patients. They must play a leadership role in providing care directly and also advising colleagues in the community how best to provide care for these patients. The need for such expertise is not limited to the OR but begins with preoperative assessment, planning, and optimization and extends to postoperative monitoring and pain management.

The ACHD team should be available as an “outreach team” for this special population, and when not providing direct management, can be called on to define physiologic parameters and goals during surgery and postoperative recovery, and to troubleshoot if unexpected and poorly understood problems arise. Not all ACHD patients who need noncardiac surgery will consent to referral to a tertiary care facility, nor will it be feasible in some cases to arrange transfer to such a facility for logistic reasons or by virtue of the urgency of the contemplated procedure. Nonetheless, such a transfer is the optimal strategy whenever feasible, in particular for patients with moderate and complex CHD.

In selected patients (ie, Fontan patients, cyanotic ACHD patients, patients with severe PH or obstructive valvular lesions, and patients with a systemic right ventricle), the congenital cardiac surgeon should be explicitly informed about the noncardiac surgical procedure in case cardiovascular complications occur perioperatively and the congenital cardiac surgeon needs to become urgently involved. In such patients, the congenital heart surgeon can also be called upon to advise and guide the colleague contemplating or performing noncardiac surgery.

Noncardiac Surgeon

A noncardiac surgeon may not have detailed knowledge of the congenital heart condition with which his or her patient presents. It is in the patient’s interest that the ACHD team brief the surgeon regarding the anatomy and physiology in the patient at hand, emphasizing anticipated differences in response to surgery in contrast to patients with acquired heart disease. This is even more important in patients undergoing intermediate or high-risk surgery (see Table 15.1 ) and in ACHD patients with high CHD-specific risk.

Operating Room Team

The anesthesiologist should act as the coordinator for perioperative care, and should help prepare the OR team for the specific challenges of the ACHD patient. The needed practice of meticulous de-airing of intravenous lines may not be routine for staff who prepare fluid sets (nurses, anesthesia technologists) but should be standard procedure for ACHD patients with known shunts and potential for paradoxic embolism.

Some patients, especially those with a Fontan circulation, will require caution with extremes of bed positioning (eg, steep Trendelenburg) and surgical approach (eg, pneumoperitoneum for laparoscopy). Some will have challenging vascular access, and some will require invasive monitoring lines for noncardiac procedures in which such lines would otherwise routinely not be needed. Some will have arrhythmia concerns that require, as a perioperative precaution, transcutaneous defibrillator pads that may not otherwise be available in a noncardiac OR.

ACHD patients often have unique psychosocial challenges because of a lifelong history of medical care that will be relevant to perioperative nursing care.