What a general cardiologist should know about adult congenital heart disease

Introduction

Congenital heart disease (CHD) comprises structural abnormalities of the heart and/or large vessels. Congenital heart defects are the most common birth defects, which are diagnosed in 0.9% of new-borns [1]. The anatomical complexity of these lesions covers a wide spectrum of severity, from very mild (for example, isolated small atrial or ventricular septal defects) to highly complex (for example, univentricular hearts). Thanks to progress in medical, interventional, and surgical treatment, the survival of CHD patients has improved and >90% of them now grow into adulthood. This has resulted in a fast-expanding adult CHD (ACHD) community which now surpasses the paediatric CHD population [2] in most developed countries.

Although the management of patients with milder lesions looks straightforward, complication-free outcome is, unfortunately, not always the case. General cardiologists must be aware of this and need to recognise the very complex status in which some patients end up. Being prepared, essentially through acquiring some basic knowledge of these lesions, their outcome and the associated complexity, is of utmost importance and is the main purpose of this paper.

Specific characteristics of ACHD

Much more pronounced than in acquired cardiovascular disease, most CHD lesions will display some degree of both haemodynamic and electrical abnormalities which mutually interact. Moreover, patients who had surgery in childhood should never be considered as “corrected”, but as “repaired”. Several CHD patients still have residual lesions or sequelae from previous interventions. These may lead to an increased risk for arrhythmia and/or heart failure which requires a specific patient-tailored therapeutic approach. In contrast to acquired heart disease, strong evidence to guide treatment in these settings is often lacking, and strategies validated by large clinical trials in acquired cardiac disease can often not be simply translated to the ACHD setting.

Since ACHD patients are much younger than the average patient seen by general cardiologists, specific aspects related to young age come into play. These include contraception, pregnancy, recurrence risk for offspring, participation in sports, insurance issues and employment. In general, ACHD patients should be considered as suffering from a chronic disease process.

We would like to propose “The Eight Commandments” for the general cardiologist to take into account when dealing with ACHD patients. We provide a brief explanation and some typical examples for each of them.

Table 1. The Eight Commandments in ACHD.

1. Track the medical history
2. Be aware of the outcome
3. Look for the expected
4. Be prepared for the unexpected
5. Use the right imaging technique
6. Deal with emergencies in the right way
7. Understand and discuss the implications and impact of pregnancy with your patients
8. Seek expert opinion

1. Track the medical history

Obtaining details from medical, interventional and surgical records in ACHD patients is crucial in order to understand the underlying anatomical defect(s), current symptoms and clinical findings.

Examples:

• A patient who underwent a left Blalock-Taussig shunt (a shunt between the left subclavian artery and the left pulmonary artery to improve pulmonary blood flow) in childhood may develop hypoplasia of the left subclavian artery whereby blood pressure measurement in the left arm becomes unreliable.
• Cyanosis in patients with Eisenmenger syndrome due to a patent ductus arteriosus will not be detected when checking oxygen saturation in the fingers. Related to the location of the shunt, cyanosis should be checked in the lower limbs (toes).
• Patients with complete transposition of the great arteries will have very different clinical outcomes depending on the type of repair: atrial versus arterial switch procedures.  

2. Be aware of the outcome

Given the young age of the population, long-term outcome data for many ACHD lesions are scarce. This sometimes makes it difficult to counsel these patients properly about their future perspectives, including the setting of family planning, insurance issues, and professional activities.

Fortunately, for some lesions, such as aortic coarctation, longer-term outcome data are available. Aortic coarctation is commonly regarded as “mild” but might have important consequences in adulthood. The most common ones are related to poorly controlled arterial hypertension. Aneurysm formation at the coarctation site is another complication that might occur even without symptoms and hence requires proper imaging for detection [3,4].

3 & 4. Look for the expected and be prepared for the unexpected

Some CHD lesions are frequently associated with other congenital abnormalities. Knowledge of both the associated lesions and the haemodynamic consequences of the primary lesion is important.

Examples of associated lesions:

• Aortic coarctation and bicuspid aortic valve: more than 50% of coarctation patients also have a bicuspid aortic valve. This needs to be checked and managed accordingly.
• Sinus venosus atrial septal defects are frequently associated with abnormal return of one or more pulmonary veins; therefore, awareness is needed.

Examples of the haemodynamic consequences of the primary lesion are:

Pre-repair

• Supra-tricuspid valve left-to-right shunts lead to a volume and pressure load of the right heart.
• Infra-tricuspid valve left-to-right shunts lead to volume load of the left heart and pressure load of the right heart.
• Patients with a congenitally corrected transposition of the great arteries (ccTGA or L-TGA) have a systemic right ventricle and are at risk of developing heart failure, severe tricuspid (systemic atrioventricular!) valve dysfunction, and arrhythmias; the risk of developing complete atrioventricular block is increased.
• Aortic valve regurgitation in patients with an outlet ventricular septal defect (VSD) is often caused by leaflet prolapse and needs to be checked.

Post-repair

• Patients with a subaortic obstruction (membrane) who had repair in childhood may develop aortic valve regurgitation and/or recurrence of the obstruction.
• Patients with congenital pulmonary valve stenosis which required balloon dilatation in childhood are at risk of residual pulmonary valve regurgitation and/or pulmonary trunk dilatation.
• In patients with a complete atrioventricular septal defect who had a common atrioventricular valve before repair, a persistent residual cleft in the anterior leaflet of the mitral valve remains present even after repair.
• Pulmonary arterial hypertension may occur, even long after repair of shunt lesions.
• Patients who had repair for tetralogy of Fallot (the most common cyanogenic heart defect) are at risk for a number of residual problems and sequelae, including residual (supra)pulmonary stenosis, pulmonary valve regurgitation (especially after transannular patch plasty), right ventricular dysfunction, right heart failure, residual VSD, aortic root enlargement, aortic valve regurgitation, prosthetic valve dysfunction, and left ventricle dysfunction.

 In addition to the aforementioned haemodynamic consequences, arrhythmias may also occur, both in patients with previous repair as in those without previous repair. The entire spectrum of rhythmic disorders (atrial/ventricular, bradycardia/tachycardia) is encountered in ACHD patients and requires special attention. The anatomy of the heart and vessels needs to be taken into account when invasive treatment is required. The underlying and potentially triggering haemodynamic problems need to be carefully explored and treated when needed [5].

A final aspect that needs specific attention is that a subset of CHD lesions may be part of an underlying genetic abnormality (both chromosomal and monogenetic). While this may be obvious and diagnosed in childhood, in many cases (especially when syndromic, such as Noonan syndrome [pulmonary valve stenosis] or Williams-Beuren syndrome [supravalvular aortic stenosis]), the genotype and phenotype may be more subtle. With advances in techniques for genetic testing, detection ratios have increased and referring patients for counselling and testing at adult age should be considered, especially in the setting of family planning [6].

5. Use the right imaging technique

Most CHD lesions require specific imaging techniques. Transthoracic echocardiography is the most commonly used imaging technique in the follow-up of CHD patients. However, to measure volumes and function of the right ventricle and to estimate the degree of left-to-right shunt, cardiac magnetic resonance imaging remains the gold standard. For atrial septal lesions, transoesophageal echocardiography is preferred. A computed tomography scan is recommended to visualise more anatomical details (e.g., implantation of coronary arteries after arterial switch repair).  

6. Deal with emergencies in the right way

ACHD patients are at increased risk for cardiovascular emergencies but may also present with common medical emergencies. They may not always – in some regions even mostly not – be admitted to a centre with sufficient ACHD expertise. General cardiologists need a basic knowledge of how to deal with these situations. Some important messages include:

• The more complex the congenital anomaly, the greater the risk of rapid haemodynamic and/or electrical deterioration and the higher the need for fast optimisation/restoration of haemodynamics and electricity.
• Do not trust a systemic right ventricle or a single ventricle as these rely on optimal haemodynamics with appropriate preload and afterload. Loss of atrial contraction for example may lead to rapid haemodynamic deterioration and hence requires timely and appropriate treatment.
• Many ACHD patients have a lifetime increased risk for endocarditis. In case of fever, be aware of (right-sided) endocarditis and be sure to take blood cultures prior to initiation of antibiotics.
• In case of right-to-left shunt, be aware of the risk of paradoxical embolism. This is especially relevant if patients need intravenous lines, in which case air filters can avoid air embolism. Induction for general anaesthesia may cause prompt afterload reduction with increasing right-to-left shunt leading to severe systemic desaturation.
• The more complex the congenital anomaly, the greater the need for seeking an expert opinion and immediate transfer to a tertiary care centre after haemodynamic stabilisation.

7. Understand and discuss the implications and impact of pregnancy with your patients

In addition to the need for proper and timely counselling of ACHD patients (women and men) about the recurrence risk when they contemplate pregnancy, women with CHD need to be counselled about the health risk the pregnancy itself may incur. Indeed, pregnancy imposes an important haemodynamic stress on the cardiovascular system and, in some cases, this will not be well tolerated. Haemodynamic changes develop even in the early stages of pregnancy (increased cardiac output, increased heart rate, etc.), but most problems will occur in the last trimester, during labour or in the post-partum period.

Assessment of the anatomic and functional status prior to pregnancy is essential. Medication needs to be carefully reviewed and, in some cases, switched prior to or shortly after conception. This is, for example, the case for angiotensin-converting enzyme inhibitors and vitamin K antagonists.

The pregnancy risk can be assessed based on the modified World Health Organization (WHO) classification system, according to which the management and the referral to tertiary centres should be considered [7]. Couples also need to be aware of impaired foetal outcome in some cases. Most importantly, parents-to-be need to be informed about their own outcome and the impact this may have on the upbringing of a child.

8. Seek expert opinion

The final and most important commandment in this list is to seek expert opinion whenever in doubt or when confronted with complex lesions with which general cardiologists have little experience. A shared care approach has proven benefits in many of these lesions. Referral of more complex cases to specialised ACHD centres is often the most appropriate approach. 

Conclusions

Within cardiology, ACHD patients are a relatively new but fast-growing group of patients with specific needs and concerns. Depending on the complexity of their condition, highly specialised care for these patients may or may not be required. This does not alter the fact that a number of patients – whether or not according to a shared care model – can also be followed by the general cardiologist. Moreover, patients with more complex lesions can also be presented to the general cardiologist, often in the setting of an urgent medical problem. Since someone who is prepared is better able to solve problems adequately, some basic knowledge is strongly recommended.

In ACHD we must assume that no patient can be considered "cured" and that new or residual problems can arise (also in the very long term). In this context, heart failure and arrhythmias are common problems that require a specific approach which often deviates from general cardiology. In addition, specific problems often occur in this young population, with which a general cardiologist is less familiar. Collaboration with and referral to specialised centres is essential in this context.