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Address correspondence to Emile Bacha, MD, Columbia University College of Physicians and Surgeons, Congenital and Pediatric Cardiac Surgery, Morgan Stanley Children's Hospital of New York-Presbyterian (CHONY), 3959 Broadway, CHN-274, New York, NY 10032
Given late outcomes of patients with tetralogy of Fallot repaired in the 1970s and 1980s, as well as a better understanding of the late deleterious effects of pulmonary regurgitation, there is a tendency toward preservation of the pulmonary valve function during primary repair of tetralogy of Fallot. The bar keeps moving downward, to include smaller and more dysmorphic pulmonary valves. This article reviews some useful indications and techniques for valve-sparing options, including intraoperative balloon dilation and cusp reconstruction using a patch. Just like other valve repair techniques, no one technique can be applied uniformly, and surgeons must master a wide armamentarium of techniques.
Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease beyond 1 week of age. It has an incidence of 0.19 to 0.26 per 1,000 live births. Neonates are often asymptomatic, and depending on the degree of right ventricular outflow tract obstruction (RVOTO) and size of pulmonary arteries (PA), present with symptoms after several months of age. However, they can also be symptomatic at birth, even presenting with ductal-dependent physiology. Every repair of TOF entails, by definition, a procedure performed on the TOF, pulmonary valve, and/or PAs. The spectrum of residual hemodynamic impairment is highly variable, as variable of TOF's phenotypic expression, and can lead to severe pulmonary stenosis (PS) on the one end of the spectrum to free pulmonary regurgitation (PR) on the other end of the spectrum. There is general agreement that avoiding either end is important, with a “Holy Grail” type of goal of no residual PS or PR. This article reviews the basic steps of TOF repair and focuses on valve-sparing options.
As a rule, any symptomatic patient with TOF is repaired, provided the anatomy is clear and there are no contraindications to cardiopulmonary bypass. The role for palliative aorto-pulmonary shunts in TOF with PA has become limited to a small subset of neonates and infants, such as those with anomalous left anterior descending coronary crossing the right ventricular outflow tract (RVOT), significant extra-cardiac anomalies, etc. In our experience, a shunt has as much morbidity associated with it than primary repair. While no prospective randomized series of TOF repair versus palliation shunt exist, several series have demonstrated the safety of the primary repair approach. Our own data demonstrated a small survival advantage for primary repair, although at the cost of a higher need for redo surgical PA plasties (catheter-based balloon angioplasty rates were similar). Thus, even symptomatic neonates with TOF usually undergo primary repair, and it is our belief that it is specifically the small and frail neonates that benefit from complete repair (and hence restored biventricular physiology post-operatively), as opposed to shunt. Repair of neonatal TOF is not fundamentally different from repair at an older age. It is important to note that residual branch PA stenosis is very poorly tolerated in the neonatal period, especially if a transannular patch was performed.
Surgical repair of TOF is otherwise performed electively, typically at around 3 to 9 months of age. Standard cardiopulmonary bypass techniques with moderate hypothermia are usually used. Intraoperative transesophageal echocardiogram (TEE) is performed to assess the anatomy and adequacy of the repair. Using cardioplegic cardiac arrest, the right atrium is opened and the intracardiac anatomy is inspected. Depending on the severity of the accompanying stenoses, the main pulmonary artery (MPA) and/or the RVOT are opened. Some surgeons are reluctant to make an incision in the RVOT, preferring to divide obstructing muscle bundles though the tricuspid valve and the pulmonary valve. Either technique has its opponents and proponents; it is impossible to discern a survival advantage associated with either. The pulmonary valve is inspected and the effective orifice is sized. It is important to realize that the effective orifice and the cuspal anatomy are only very loosely related to the z score, which only describes the annular diameter. Based on the diameter of the pulmonary annulus and the anatomy of the cusps, a decision is made whether to preserve the annulus or perform a transannular patch (z score of -2 is sometimes used as the cut-off). The ventricular septal defect (VSD) is exposed either through the MPA, the infundibular incision, or a right atrial incision. The VSD is usually patched with a synthetic patch or glutaraldehyde-treated autologous pericardium. The MPA or RVOT incisions are patched, using patches as well. An atrial communication, unless it is large, is left patent (2 to 3 mm) to provide a pop-off mechanism in case of postoperative right ventricular (RV) dysfunction. Inotropic support is sometimes required perioperatively. Once the VSD is adequately closed, the post-operative course depends on the degree of RV dysfunction (usually temporary; 24 to 48 hours), the status of the RVOT with respect to PR or residual PA, and any residual branch PA stenosis. It is also important to know that residual VSDs are very poorly tolerated, specifically in TOF patients, because their ventricles were pressure-loaded before surgery, and the ventricles do not tolerate the volume loading that accompanies a residual VSD. Such a patient should be promptly returned to the operating room for closure of the residual VSD.
TOF anatomy has a wide range of individual variability. Associated PA narrowing is addressed during the same operation. Mortality for standard TOF surgery is very low (1.3% in recent Society of Thoracic Surgeon's congenital database analysis
). Potential complications that are specific to TOF surgery include RV dysfunction (usually limited), atrioventricular block (<3%), junctional ectopic tachycardia (JET) (<5%), patch dehiscence with residual VSD, and residual RVOT obstruction.
Pulmonary Valve Preservation in TOF Surgery: The Scope of the Problem
Initial TOF repair in the 1960s and 1970s were mostly performed with large transannular RVOT patches.
RV dilation, RV diastolic dysfunction, RV fibrosis, tricuspid regurgitation (annular dilation, but sometimes due to damage to the tricuspid subvalvar apparatus during VSD closure or distortion by the patch), arrhythmias (risk of ventricular arrhythmias),
and, in late stages, LV dysfunction, are all recognized as late sequelae of chronic PR following TOF repair. Finally, the RVOT patch itself can act as an energy sink, especially when large and patulous.
Thus, virtually every surgeon would agree that pulmonary valve preservation is beneficial in this setting. The question is: At what price? In other words, in an ideal setting, one would have no regurgitation and no residual RVOT stenosis following TOF repair. Because this is rarely possible - except in ideal anatomic circumstances - how much residual PS is too much to leave behind, and how much PR is acceptable (keeping in mind that quantification of PR by TEE is questionable and provides a gross estimate only, in addition to the fact that RV restrictive physiology, often present after surgery, also plays a role in [minimizing] the degree of PR)?
A recent survey of the Society of Thoracic Surgeons Database
concluded by stating that “despite contemporary awareness of the late consequences of pulmonary insufficiency, ventriculotomy with transannular patch remains the most prevalent technique, both for primary repair and for repair following palliation.”
Surgical Options for Valve-Sparing TOF Surgery
In every case, one should always aim to completely relieve the subvalvar and supravalvar areas by:
Doing a complete infundibular muscle resection, including the area just under the annulus (either via limited infundibulotomy or via transatrial/transpulmonary).
Unless well-developed MPA, MPA longitudinal incision from annulus to exact midpoint of distal MPA/PA bifurcation, and patch augmentation.
There is often an under-appreciated element of supra-PS, with the sinotubular junction of the posterior sinus being narrowed. This can be dealt with either with a separate small patch or with partial-thickness incisions to the media of the vessel wall (without breaching the adventitia).
Choices for Valve-Sparing Options Depend on an Extensive Study of the Pulmonary Valve Anatomy
Carpentier's rule of studying a mitral valve for at least 5 minutes before beginning the repair should also be used here. The number of cusps, their thickness and length, the orientation of the commissures, the difference between the effective orifice at the cusp edge versus at the annulus are all important elements. One should always refer to a normalized chart of pulmonary annular sizes in relation to the patient's body surface area.
Commissurotomy ± Rigid Bougie Dilation
This is the simplest technique, and is used in cases of mild-to-moderate PA with little pulmonary valve dysplasia. As always, a pulmonary valve commissurotomy into the media layer is performed. Hegar dilators or balloons (see below) are serially inserted, aiming for 1 to 2 mm higher than the calculated normal pulmonary annular size.
Commissurotomy and Intraoperative Balloon Pulmonary Valve Dilation
Experience from percutaneous transcatheter balloon dilation of isolated pulmonary valve stenosis suggests that valve annuli grow over time. As opposed to Hegar dilation, a balloon can be introduced in a valve annulus at a diameter much smaller than the orifice, and dilation occurs in static position. There is radial transmission of stress. This potentially allows for remodeling and growth of the pulmonary annulus.
This technique is best reserved for moderate PS with moderate cusp dysplasia. After commissurotomy, the effective valve orifice is sized with a Hegar dilator (without dilation). Starting with a balloon 1 mm larger than the Hegar size that slipped through the valve easily, the balloon is inserted either via the infundibular incision or via the unopened RVOT transatrially and inflated by hand. The inflation is monitored visually, as one can see the stretching of the cusps and annulus. The balloons are gradually increased in size by 1-mm increments.
In an initial series of 37 patients with z scores between -2 and -4, evidence for annular growth over time was seen, with normalization of the pulmonary annular size in many patients.
As compared with a similar group that received transannular patches, a higher reintervention rate was seen because of residual PS (mostly managed via transcatheter balloon dilation) in the intraoperative balloon pulmonary valve dilation group. A subset of patients where this technique is also useful is those with anomalous coronary crossing the RVOT. This technique is also useful in patients with mild PS only,
The annulus and anterior cusp are divided as for a transannular patch, leaving equal cusp remnants on each side. The tethering of the anterior cusp to the MPA is left untouched to preserve hinge function of the newly created large anterior cusp. Native pericardium can be used as patch material, but also 0.1 mm polytetrafluoroethylene (PTFE) or extracellular matrix (ECM). The width of the patch is tailored according to the fraction of the Hegar dilator circumference exposed at the annulus during RVOT calibration. The patch is sutured to each cut cusp edge, leaving 1 to 2 mm protruding over the free edge of the valve. Caudally, it can be sutured at the level of the pulmonary annulus to the other “transannular” patch that covers the entire RVOT, or it can be sutured to the cut edge of the infundibulotomy. The 2d patch then covers the entire incision, from distal MPA to proximal RVOT.
The pulmonary valve anatomy has been neglected by congenital heart surgeons. z scores are simply normalized values of pulmonary annuli and do not reflect the degree of cusp dysplasia or effective orifice available. Thus, relying only on z scores can be misleading, and results in confounding statistics. z scores need to be taken into account, but intraoperative inspection of the valve is equally important. Congenital heart surgeons should start to think in terms of valve morphology, not only in terms of annular size, and pulmonary valve “repairs” should become as commonplace as mitral valve repairs, with every patient being a candidate for one technique or the other until proven otherwise.
Al Habib H.F.
contemporary patterns of management of tetralogy of Fallot: data from the Society of Thoracic Surgeons Database.