Abstract
The population of adults with congenital heart disease is large and growing. This group has a high rate of health resource utilization, including hospital admissions. It is predicted that this will only continue to grow as more individuals with moderate and complex congenital heart disease age into middle and late adulthood. Adult congenital heart disease (ACHD) patients hospitalized in the intensive care unit require coordinated, multidisciplinary care, ideally from a care team with experience in congenital heart disease. ACHD patients have a distinct set of hemodynamic, physiologic, and social needs that should be considered in their ongoing care. In addition to their high risk of cardiac complications, such as heart failure and arrhythmia, they are also at increased risk of noncardiac complications, such as liver and kidney disease. This chapter summarizes the unique challenges faced by providers caring for this population and offers recommendations for treatment based on the currently available data.
Key Words
congenital heart disease, heart failure, arrhythmia, aging, emergency cardiac care
Intensive care unit (ICU) admissions are not uncommon in adult congenital heart disease (ACHD) patients. Much of the growing population of individuals with congenital defects will require cardiac care throughout their adult lives, including a substantial portion who will need intensive cardiac care. Consistent with the increase in the number of adults living with congenital heart disease (CHD), there has been a significant increase in the number of ACHD hospitalizations in the United States, including hospitalizations to the ICU. In one population-based Canadian study, 16% of ACHD patients required ICU admission over a 4-year period. Even patients considered to have undergone “complete repair” have a high rate of long-term cardiac complications, including arrhythmias, heart failure, and the need for reoperation. This is particularly true for those with moderate or complex disease, who require more interventions and have worse outcomes.
It has been said that adults are not large children. Although adult and pediatric patients with CHD share common anatomy and physiology, there are also key differences between these two populations. Unique features of adults include the presence of medical comorbidities and a higher percentage of redo surgeries that pose greater risk. Adults with CHD also have different physiologic and social factors that set them apart from children with CHD. Providers often struggle to apply data obtained from pediatric CHD populations to their adult patients or to extrapolate from studies performed in adults with acquired heart disease as opposed to CHD.
Systems of care for hospitalized ACHD patients vary by city, with no agreement as to which model is best. Many young adults with CHD continue to receive their care, including ICU care, at pediatric hospitals. Alternatively, many adults are found in adult cardiac care, either through deliberate transition to an adult ACHD program or by establishing care with a non-ACHD adult cardiologist. Specialized ACHD care has been associated with decreased mortality, and the location of care is especially important for ACHD patients in the ICU, who require a team that is experienced in the management of both CHD and non-CHD aspects of their care. Such combined expertise may be best found in either an adult or pediatric ICU, depending on the region.
Common Reasons for Intensive Care Unit Admission in Adult Congenital Heart Disease
The most common indications for ICU admission in ACHD patients are postoperative care, followed by heart failure and arrhythmias. Many ACHD patients undergo cardiac reoperations, which are associated with a higher risk of morbidity and mortality than primary repairs. A postoperative admission to the ICU may be as short as 24 hours in an uncomplicated postoperative patient or longer in patients who are slow to wean off the ventilator, have ongoing hemodynamic or respiratory compromise, or have significant bradyarrhythmias or tachyarrhythmias.
Published mortality rates for ACHD patients undergoing surgery are low; however, at least one in five patients has a major adverse event, including stroke, renal failure, and prolonged ventilation. Arrhythmias are the most common type of postoperative cardiac complication. Our ability to predict which ACHD patients are at highest risk of postoperative complications is limited, although it is an area of active investigation. It seems that pediatric risk scores are of reasonable predictive value for assessing surgical risk in adults, and existing ICU risk scores can also be used with some success.
Heart failure is another common indication for ICU admission and is on the rise. Although many ACHD patients with heart failure can be successfully managed on a medical floor or cardiac step-down unit, some will require ICU admission. At our institution the most common indications for ICU admission in a heart failure patient are the need for inotropes, unstable respiratory status (e.g., a patient requiring biphasic positive airway pressure or intubation), or unstable supraventricular or ventricular arrhythmias.
Less commonly, pregnant ACHD patients may be admitted to the ICU for labor and delivery (e.g., a woman with severe left ventricular outflow tract obstruction). These patients require complex, coordinated team-based care with input from high-risk obstetrics, ACHD, critical care, electrophysiology, and obstetric and cardiac anesthesia.
Adult Congenital Heart Disease Patient in the Intensive Care Unit: Systems Factors
Patients with moderate to complex ACHD require coordinated, multidisciplinary care when in the ICU. It is now clear that there are specific systems-level challenges facing providers and hospital systems caring for these patients. First, like many complex medical populations, patients with ACHD have a high rate of health resource utilization (HRU). ICU care is an important contributor to HRU and one that is anticipated to grow over time as the population ages. The costs and degree of HRU are higher for complex patients as opposed to those with simple lesions. Several risk factors for HRU at either pediatric or adult hospitals have been identified in ACHD, including admissions with greater surgical complexity, emergency admissions, heart failure or renal failure, and patient factors such as government insurance, DiGeorge syndrome, and depression.
As mentioned earlier, ACHD patients may receive care in a variety of locations, and whether ACHD patients are better cared for at an adult or a pediatric hospital is a source of ongoing controversy. Despite their age, ACHD patients constitute a small but not insignificant proportion of admissions at pediatric hospitals. This proportion has grown commensurately with the size of the ACHD population. Adult cardiac surgeries are frequently performed at children’s hospitals with good results. Surgical mortality appears to be lower when ACHD surgery is performed by a congenital heart surgeon, although this may be at an adult or a pediatric hospital. In either location it is essential that there is familiarity and experience with CHD at all levels of patient care. The surgical team, anesthesiologists, intensivists, subspecialists, and nurses all play an important role in caring for these patients. In addition, the ACHD provider, when available, has an essential role in following patients throughout the system and helping to guide their care.
Finally, loss to follow-up is a major issue in the ACHD population, and some patients who are lost to follow-up may represent to the medical system at the time of ICU admission. In these cases it is imperative that the ICU team attempt to identify a CHD provider who can assist in the patient’s management and also help facilitate their long-term care, including transfer to the care of an appropriate outpatient ACHD provider.
Adult Congenital Heart Disease Patient in the Intensive Care Unit: Unique Physiologic Factors
Comorbidities Not Related to Congenital Heart Disease
There are several extracardiac features that make the ACHD patient unique in the ICU ( Box 76.1 ) and more vulnerable to unforeseen complications. These noncardiac comorbidities are more prevalent in adults than in the pediatric CHD population and can jeopardize optimal management. These include renal and hepatic problems, as well as acquired cardiac conditions and chronic lung disease. All should be seriously considered as potential risk factors by the intensivist.
Central Venous Access
Anatomic features can complicate central line placement (e.g., persistent left superior vena cava).
Placement of a central line across a Glenn anastomosis into the pulmonary arteries carries a risk of thrombosis and should be avoided when possible.
Positive Pressure Ventilation
The use of positive pressure ventilation may decrease preload, and therefore cardiac output, in patients with a Fontan circulation.
There is a high frequency of chronic lung disease, especially restrictive disease, in adults with repaired CHD.
Inotropes
Patients with systemic right ventricles or a Fontan repair may not have the expected response to inotropes. Attention should be paid to other factors, such as preload, pulmonary vascular resistance, and chronotropic response, which also have an important hemodynamic impact.
Thrombosis Risk
Some patients with ACHD, such as those with Fontan palliation or Eisenmenger syndrome, are at increased risk of thrombosis. Eisenmenger syndrome also carries an increased risk of bleeding, and therefore decisions about anticoagulation should be undertaken in consultation with a CHD specialist.
Hepatic Dysfunction
Hepatic dysfunction and even cirrhosis can develop in Fontan patients and in those with chronically elevated right heart pressures and resultant hepatic dysfunction. Providers should have a low threshold for screening for hepatic dysfunction and manage patients appropriately.
Renal Dysfunction
Thirty percent to 50% of ACHD patients have significantly impaired renal function, which may not always manifest as a significantly elevated serum creatinine level. Patients with cyanotic heart disease are at especially high risk.
ACHD, Adult congenital heart disease; CDH, congenital heart disease.
Chronic renal dysfunction is more common in ACHD patients than in the general population, presumably because of abnormal cardiac physiology and its impact on renal perfusion, as well as factors such as nephrotoxic medications, chronic hypoxia, and neurohormonal abnormalities. One study found that significant renal dysfunction was 18 times higher in noncyanotic ACHD patients and 35 times higher in cyanotic ACHD patients than in the general population, whereas another suggested that 30% to 50% of ACHD patients have significantly impaired renal function. The presence of renal dysfunction, either subclinical or clinical, can complicate ICU management and is a predictor of adverse outcomes. Additionally, cardiopulmonary bypass is associated with acute kidney injury and is a frequent contributing factor in renal dysfunction in ACHD patients in the ICU. Providers caring for ACHD patients should be mindful of the impact of selected therapies on renal perfusion and take renal function into account when selecting medications and interventions.
Hepatic dysfunction is also common in ACHD patients, especially those with the Fontan circulation. In addition to being a risk factor for surgical mortality, hepatic dysfunction can impact hemodynamics and the clearance of certain medications. All patients with Fontan physiology and those with passive venous congestion of the liver should be considered to be at high risk for liver disease and managed appropriately (e.g., Ebstein anomaly, repaired tetralogy of Fallot with pulmonic regurgitation).
Other common adult comorbidities with impact on ICU management include obstructive sleep apnea, acquired heart disease such as coronary artery disease (CAD), and chronic lung disease. Nearly half of ACHD patients have impaired lung function. Approximately 30% of ACHD patients have moderate to severe respiratory impairment. Restrictive lung disease is particularly common in those with previous chest surgery. This has important implications for ventilation strategies and for ventilator weaning.
Systemic Right Ventricle
Patients with a systemic right ventricle (RV) (congenitally corrected transposition of the great arteries or d-transposition of the great arteries after an atrial switch procedure) constitute a small but important part of the ACHD population. Patients with a hypoplastic left heart are another group of survivors with systemic RV, in whom many of these same issues may be faced.
Important anatomic and physiologic differences between the systemic morphologic RV and the systemic morphologic left ventricle (LV) have implications not only for the long-term risk of RV failure and arrhythmia but also for ICU management. Due to differences in myocardial geometry, atrioventricular valve structure, and papillary muscles, the RV as a systemic pump is inferior to the morphologic LV.
Importantly, a systemic RV may not respond to inotropy in the same manner as a systemic LV, as evidenced by the fact that stroke volume fails to augment with dobutamine stress, particularly in those with an atrial switch palliation. It has been hypothesized that this is due to the rigid atrial baffle that alters preload as opposed to some factor intrinsic to the systemic RV because a similar impairment is not seen in those with congenitally corrected transposition. Theoretically, atrial switch patients can compensate for the inability to augment stroke volume by increasing heart rate, but this may also be limited in those with chronotropic incompetence or chronic pacing, both of which are common.
Myocardial dysfunction leading to clinical heart failure is a common presentation in individuals with a systemic RV. Unfortunately, data are lacking regarding the efficacy of conventional heart failure therapy for the failing RV. In the absence of specific data, many providers use similar therapies for the failing RV as they do for the failing LV. This is discussed in further detail later.
Fontan Circulation
The Fontan pathways for single ventricle palliation have created a growing cohort of patients who are aging into adulthood and experiencing complications. These include Fontan pathway obstruction, single-ventricle dysfunction, atrioventricular valve regurgitation, arrhythmias, cyanosis, protein-losing enteropathy, and liver dysfunction, among others. As this population ages, we anticipate that ICU admission will become increasingly common. Specific issues that are pertinent to the Fontan patient in the ICU include vascular access, the importance of preload and low pulmonary vascular resistance (PVR), and the response to inotropes.
Because the systemic venous return is directly anastomosed to the pulmonary arteries (bidirectional Glenn shunt), placement of a central line via the SVC into the Glenn shunt or pulmonary arteries should be avoided if possible given the theoretical risk of catheter-associated thrombosis and Fontan obstruction. Alternate forms of venous access, such as a midline catheter, are preferable in Fontan patients. In someone with a classic atriopulmonary Fontan connection, interpretation of a central venous waveform, measured pressure, or quantification of output should be done with the unique Fontan physiology in mind.
Mechanical ventilation also presents unique challenges in the Fontan patient. Normal negative intrathoracic pressure during spontaneous inhalation is a key contributor to pulmonary blood flow, and therefore to ventricular preload, in Fontan patients. The hemodynamic benefit of spontaneous breathing was first recognized by Fontan after his initial procedures. As estimated by magnetic resonance blood tagging, 30% of systemic venous pathway flow is respiratory dependent, with inspiration being one of the highest periods of Fontan flow. Therefore positive pressure ventilation may have a deleterious impact on lung perfusion, ventricular preload, and cardiac output. This is evidenced by the fact that the cardiac index increases significantly when patients are extubated after the Fontan procedure. Early extubation is now considered the optimal management strategy after initial Fontan palliation, and avoidance of positive pressure ventilation is recommended whenever possible. Recognizing that mechanical ventilation is sometimes unavoidable, we recommend the use of low-pressure strategies, such as avoidance of positive end-expiratory pressure, as well as careful attention to preload and contractility during the period that the patient is ventilated.
Ventricular preload is an important determinant of cardiac output in Fontan patients. Preload is determined by the transpulmonary gradient and by flow through a Fontan fenestration, if present. PVR is also an important determinant of cardiac output in Fontan patients. Even small increases in PVR can result in a decrease in ventricular preload and hence cardiac output. Therefore ICU providers caring for Fontan patients should be attentive to PVR and avoid factors that cause it to increase when possible.
Inotropes fail to increase the stroke volume output of a Fontan patient to the same degree that they do in a patient with a two-ventricle circulation. This finding is probably because preload is a more important determinant of cardiac output than contractility in the majority of Fontan patients. The exception to this is the patient with severely impaired ventricular function, who may benefit from inotropy. It is important to note that increasing heart rate may also not be an effective mechanism to increase cardiac output, at least not by atrial pacing.
Common Management Concerns in Adult Congenital Heart Disease Patients
Central Venous Access
Central venous access is commonly used to guide management in ICU patients. ACHD patients may have abnormal venous anatomy, such as a left-sided SVC, which may necessitate the use of imaging guidance for line placement (e.g., persistent left SVC, present in approximately 1% of individuals with CHD). Venous obstruction can be an issue in patients who have had prior invasive procedures. Finally, as mentioned earlier, patients with Glenn shunts (e.g., Fontan) have a direct connection between the SVC and the pulmonary arteries. Placing a catheter in the Glenn shunt or pulmonary arteries is generally not recommended due to the theoretical risk of thrombosis and Fontan obstruction in this relatively low-flow system.
Right Ventricular Dysfunction
RV dysfunction is common among ACHD patients and occurs in patients with a systemic LV as well as those with a systemic RV. Subpulmonic RV dysfunction is frequently seen postoperatively and can be associated with clinical RV failure in some patients. RV failure can occur after either left- or right-sided congenital heart surgery and is associated with a high mortality in the ACHD population. Preoperative RV dysfunction, cardiopulmonary bypass time of longer than 150 minutes, and postoperative supraventricular tachycardia have been identified as important risk factors for RV failure in ACHD patients. For example, a patient with Ebstein anomaly and seemingly normal preoperative RV systolic function may exhibit very poor systolic function postoperatively, even jeopardizing LV filling as a result. Although subpulmonic right ventricular assistant devices are an enticing option for these patients, the data in ACHD are extremely limited at this time.
Acute Arrhythmias
Arrhythmias are the most common cause of hospital admission in ACHD. ACHD patients are at risk of arrhythmias for a variety of reasons, including complex anatomy, surgical scars, and abnormal hemodynamics. Age is also an important factor. The prevalence of arrhythmias in tetralogy of Fallot, for example, increases sharply in older patients. Hence the frequency of ICU admission for arrhythmias is likely to increase as the population ages.
Atrial arrhythmias commonly seen in the ACHD population include intraatrial reentrant tachycardia, atrial flutter, and atrial fibrillation. In general, CHD patients benefit from a rhythm control strategy for atrial arrhythmias, as opposed to the rate control strategy, which is widely employed in the management of adult atrial fibrillation. This can be performed with medications (most commonly amiodarone in the ICU) and/or cardioversion. In some cases adenosine may be useful to break atrial arrhythmias or determine cause. Providers using amiodarone should be mindful of the high frequency of liver dysfunction in CHD patients, especially those after Fontan palliation.
Some patients with atrial arrhythmias, particularly those after Fontan palliation, may deteriorate rapidly if sinus rhythm is not restored. Early cardioversion should be seriously considered, with a low threshold for transesophageal echocardiography beforehand. ACHD patients have a higher than expected risk for thromboembolic complications. Transesophageal echocardiography may not be anatomically straightforward, particularly in a systemic RV or Fontan patient. Therefore in certain instances expeditious cardioversion in response to a new rhythm may be preferable to waiting. Ablation may be appropriate for the management of atrial arrhythmias in some patients, although it is generally performed in stable patients, as opposed to those requiring ICU care. Consultation with an electrophysiologist experienced in CHD is recommended to determine the optimal management strategy.
CHA 2 DS 2 -VASc score is not applicable in this population, and providers should not use it to predict risk of stroke in patients with moderate or complex CHD. Additionally, providers should understand that there are CHD-specific factors that increase the risk of bleeding in this population, such as liver dysfunction, renal dysfunction, and cyanosis. Although vitamin K antagonist therapy is the traditional anticoagulant used in CHD patients, we anticipate that direct oral anticoagulants (DOACs) will be used with increasing frequency in the coming years. At the current time there is an overall lack of data about DOAC use in ACHD, although the preliminary data appear promising.
Some patients with CHD are also at risk for bradyarrhythmias and heart block, such as those with l-transposition of the great arteries or atrioventricular septal defects. Dysfunction of the sinus and/or atrioventricular node is common in ACHD patients, particularly after surgery. Patients may require temporary and/or permanent pacemaker implantation to maintain hemodynamic stability or alleviate symptoms. Consultation with an electrophysiologist experienced in CHD is recommended because some patients may have issues with access and/or physiology that necessitate the use of nonstandard protocols for pacemaker implantation. Examples include an atrial switch patient with superior venous baffle stenosis who requires concurrent baffle stenting or a single-ventricle patient who requires an epicardial device for ventricular pacing.
Although sudden death is a recognized feature of ACHD, new presentations of sustained ventricular tachycardia (VT) are uncommon. Nonsustained VT occurs fairly frequently, however. Predisposing factors for VT in this population include prior ventriculotomy repair (such as the older patient with tetralogy of Fallot) and ventricular dysfunction. Scar-related VT may be amenable to catheter ablation, whereas VT related to underlying ventricular dysfunction is more challenging to treat.
Heart Failure
The prevalence of heart failure in ACHD has risen dramatically over the last few decades, reflective of an aging and increasing complex ACHD population. Heart failure is one of the most common causes of death in ACHD patients, constituting approximately 25% of all deaths. As discussed earlier, patients with a systemic RV and those with a single-ventricle circulation are at especially high risk of developing heart failure. Other ACHD patients, such as those with valvar disease, pulmonary hypertension, or ventricular dysfunction after repair of tetralogy of Fallot, may also commonly develop heart failure.
Manifestations of heart failure in the ACHD patient are often different than in the non-ACHD patient, leading to improper recognition and/or treatment. A classic example is the Fontan patient, who may present with “heart failure” of a variety of clinical phenotypes. Some failing Fontan patients present with a reduced ejection fraction, elevated filling pressures, low cardiac output, and high systemic vascular resistance (SVR), similar to the typical adult patient with systolic heart failure. Yet other “failing” Fontan patients present with signs of right-sided heart failure in the setting of preserved ejection fraction and normal filling pressures. These different phenotypes require markedly different treatment strategies.
The neurohormonal changes in ACHD heart failure are similar to those in non-ACHD heart failure, suggesting that similar treatment paradigms may apply. Unfortunately, the use of traditional chronic heart failure treatment strategies, such as angiotensin-converting enzyme inhibitors, beta-blockers, and spironolactone, is currently limited by lack of data and/or efficacy in the ACHD population. Large heart failure trials have tended to exclude individuals with CHD, and CHD-specific studies have often been retrospective or underpowered or have failed to show a benefit. Similarly, therapies for acute heart failure have not been validated in the ACHD population. In the absence of evidence-based therapies, providers caring for ACHD patients with heart failure typically use standard therapies that have been validated in non–CHD-associated heart failure while also trying to be mindful of unique aspects of the ACHD patient.
In contrast to patients with non–CHD-associated heart failure, ACHD-associated heart failure may be related to residual hemodynamic lesions, which can be treated with catheter-based therapy. Common examples include baffle leaks or stenosis in patients after an atrial switch procedure, pulmonary valve stenosis and/or regurgitation in a patient with repaired tetralogy of Fallot, or branch pulmonary artery stenosis in a patient with Fontan circulation ( Table 76.1 ). Because of the unique hemodynamic factors in individuals with CHD, intensive care providers caring for ACHD patients with heart failure should obtain early consultation from a provider with specific training in CHD. Depending on the setting, this provider could be a trained ACHD provider, a pediatric cardiologist or CHD surgeon, or an interventional cardiologist with experience in CHD.
