An increasingly quoted statistic in recent times is the statement that there are now more adults alive with congenital heart disease than there are children. This reflects the fact that paediatric and neonatal cardiac surgery outcomes have transformed the natural history of these conditions. Fifty years ago, 85 per cent of all complex congenital heart conditions were lethal in childhood, whereas now over 85 per cent would be expected to survive into adulthood.
However, this survival does not come without cost, and many patients will have residual lesions or develop new problems related to their underlying condition and previous surgery. Consequently, the area of adult congenital heart disease (sometimes also known as ‘grown-up congenital heart disease’ (GUCH)) has become a rapidly expanding field with the need for surgical as well as expert cardiology care. The indications for surgery in these patients can be broadly divided into three categories:
1. Newly diagnosed congenital heart disease in adulthood. These are most commonly atrial septal defects (ASDs), partial atrio-ventricular septal defects (AVSDs) or lesser degrees of coarctation that have never presented during childhood and are picked up due to the development of symptoms or a chance finding on examination. Alternatively, progression of known lesions from childhood such as a dysplastic aortic valve may become clinically significant later in life and require a first intervention in adulthood.
2. The residua and sequelae of procedures performed during childhood. This is by far the largest group and includes replacing conduits and valves placed during childhood due to degeneration or outgrowth. It also includes the progression of pulmonary regurgitation following repair of Fallot’s tetralogy leading to the need for pulmonary valve replacement (see below) or the progression of left ventricular outflow tract stenosis after the Rastelli procedure. Residual lesions include residual ASDs following childhood repair or valvar regurgitation after AVSD repair.
3. Problems arising from the natural history of the underlying conditions or previous procedures. This includes such conditions as ascending aortic dilatation in pulmonary atresia/tetralogy of Fallot and in the post-Ross procedure and right atrial dilatation following the Fontan procedure necessitating conversion to total cavo-pulmonary connection.
A summary of the frequency of ACHD procedures is shown in Table 25.1.
|Pulmonary valve replacement||25–38%|
|Aortic valve replacement/Ross||5–7%|
|Sinus venosus ASD||6–8%|
|Ebstein’s tricuspid repair/replacement||4–5%|
|Reoperation on Mustard/Senning||2–4%|
|Palliative procedures – shunts and Glenn||3%|
Special Considerations in ACHD Surgery
The median age for these procedures is still in the mid-twenties; thus, although there are increasing numbers of older patients, this is still mainly a population of young adults. Consequently, the choice of valve replacements and conduits has to reflect both the need for longevity and the expectations of young adults, particularly women and the issues of pregnancy. In terms of the procedures themselves, over 70 per cent are re-operations with the attendant risks of redo – sternotomy and possible need for femoral bypass. Patients may also already have undergone multiple previous procedures, which can make surgery technically difficult with densely adherent structures and stiff and calcified old conduits and patchwork. Previous homografts can become densely calcified and adherent to the chest wall (Figure 25.1), making sternotomy hazardous. This highlights the importance of protective measures taken at the original procedure, such as the placement of membranes behind the sternum and partial closure of the pericardium.
Drug compliance and lifestyle are important considerations, as is the risk that bioprosthetic valves are likely to last for shorter periods due to active use. Thus, there is a strong focus on valve repair and reconstruction where possible.
Pulmonary Valve Replacement
The commonest procedure in ACHD surgery is pulmonary valve replacement in adults who underwent repair of tetralogy of Fallot in childhood. Most patients would have received a trans-annular patch, laying open the pulmonary valve at the time of initial repair. The pulmonary regurgitation is well tolerated throughout childhood, but the chronic volume load leads to progressive right ventricular dilatation, which, in turn, leads to exercise intolerance as the ventricle becomes less compliant with age and distension (Figure 25.2). There has been increasing concern that pulmonary valve replacement is being performed too late and that irreversible right ventricular injury can occur from allowing dilatation to go unchecked. A similar lesson has been learnt to that of aortic valve replacement in regurgitant disease, in that valve replacement is recommended based on ventricular dimensions rather than necessarily awaiting for symptoms. Measuring the absolute volume of the RV can be difficult due to its asymmetrical shape, but MRI has now provided accurate volume measurement. Valve replacement can now be recommended based on volumes reaching 140 to 150 mL/m2 and/or evidence of reduced VO2,max on exercise testing. As further studies come to light, even these figures are being questioned, and replacement at a volume of 120 mL/m2 has been suggested, with all RVs in this group returning to normal dimension during follow-up. Similar studies have also focused on right ventricular end-systolic volume, suggesting 85 mL/m2 as a discriminant value. Tricuspid regurgitation is less common and usually is secondary to right ventricular dilatation. It usually can be successfully treated with annuloplasty with or without a valve ring at time of pulmonary valve replacement.