Surgical management of tetralogy of Fallot with anomalous coronary artery.
Fifteen patients of tetralogy of Fallot with an anomalous left anterior descending coronary artery arising from the right coronary artery were operated during a period of 1982 and 1988. One patient died in the early post-operative period (6.6%). Two patients had a hemodynamically insignificant residual ventricular septal defect. Post-operative peak systolic pressure gradient between the right ventricle and pulmonary artery ranged from 10 mm Hg to 40 mm Hg (mean 24 mm Hg) in 4 patients. There was no incidence of inadvertent coronary artery division.
Anomalous origin of left anterior descending coronary artery (LAD) from right coronary artery (RCA) is the most common coronary arterial anomaly in tetralogy of Fallot (TOF). An anomalous coronary artery, which crosses the right ventricular outflow tract (RVOT) is vulnerable to injury during a right ventriculotomy and presents difficulties during RVOT reconstruction. We evaluate here our experience with this anomaly.
Two hundred and thirty two patients underwent intra-cardiac repair for TOF between 1982 and 1988. In 15 patients, (11 males and 4 females) the LAD was originated from the RCA (6.46%). Age of these patients ranged from 2.1 yrs to 8.3 yrs (mean 5.5 yrs) and their mean weight was 12.5 kg (9-20 kg). The diagnosis of TOF was established in all the patients with echocardiography, cardiac catheterisation and angiography. The additional associated anomalies were as shown in [Table - 1]. In only one 7-year-old patient anomalous coronary artery was identified preoperatively on angiography.
All patients underwent intra-cardiac repair of TOF with conventional cardiopulmonary bypass with moderate hypothermia and hemodilution. The anomalously coursing LAD was identified and protected. The approaches used were as shown in [Figure:1]. All transverse ventriculotomies were closed directly. All vertical ventriculotomies were closed with autologous pericardial patch. Transannular patch was required in 3 patients.
There was one early hospital death (6.6%). This patient died of multi-system failure following mediastinitis and septicaemia. Three patients required prolonged inotropic support. The period of follow up ranged from 11 months to 6 years (mean 3 yrs and 2 mths). All patients were subjected to echocardiography at follow up. The post-operative peak systolic pressure gradient across the RVOT ranged from 10 mm to 40 mm Hg (mean 24 nun Hg). In two there were residual ventricular septal defects (VSD) measuring 2 mm and 4 mm. Both were haemodynamically insignificant as revealed during cardiac catheterisation. Twelve patients had an incomplete Right Bundle Branch Block (RBBB) while in two, there was complete RBBB.
The grade of cardiac dysfunction in twelve patients was NYHA functional class I and in two patients class II.
Coronary artery anomalies are often associated with tetralogy of Fallot. Left anterior descending coronary artery arising from the right coronary artery and crossing the RVOT is the commonest of them with a reported incidences of 2-9%,,,. Intra-cardiac repair of TOF includes relief of the RVOT obstruction and VSD closure. This is often per formed through a vertical right ventriculotomy, which may be extended across the pulmonary annulus if necessary. An anomalous LAD crossing the RVOT is particularly vulnerable to injury if the conventional vertical incision is made. Inadvertent division of the coronary artery invariably results in serious myocardial ischaemia and death,. Various options are available.
1. If the patient is too small defer surgery till age 5-6 years when other options are available.
2. Palliate patient with temporary Blalock Taussig shunt.
3. Right atrial approach.
4. Tailored ventriculotomy parallel to the anomalous coronary artery either caulad or along with a cephalad incision.
5. Conduit placement between the right ventricle and pulmonary artery,.
6. Dissection and RVOT patching under the coronary artery.
7. A saphenous vein bypass to distal segment when the coronary artery has been inadvertently divided .
The choice of procedure used depends on several factors, viz. the age of the patient, pre operative diagnosis of the anomaly, the course and relationship of the anomalous coronary artery to the pulmonary annulus and the site and severity of the RVOT obstruction.
We have used the tailored ventriculotomy and the right atrial approach in all 15 patients. There was no inadvertent division of the coronary artery in any patient. Humes et al has used an RV-PA conduct in 8 of 20 patients of this anomaly. His mean age of repair in the conduit group, however, was 16.3 years and patch group 5.8 years. Our mean age of repair in all 15 patients was 5.5 years.
The problems of somatic growth, potential for obstruction and re-surgery mar the advantages of a conduct,. Further, the mortality and the post-surgery peak systolic right ventricular pressure to peak systolic left ventricular pressure ratio were not significantly different in the conduit and patch groups of Humes et al. The conduit may, however, be used in relatively older patients where the RVOT obstruction is too severe or coronary artery tortuosity and course preclude an RV approach.
It is controversial whether a pre-operative diagnosis of the anomalous coronary artery is necessary,,. It is no doubt an ideal situation to have a pre-operative delineation of the coronary arteries in all patients, but in the series of Humes et a1 only 2 of 12 patients in the patch group had a preoperative diagnosis of the anomaly. Their delineation is mandatory in the following situations:
1. Previous intra-pericardial surgery where the coronary artery anatomy is not obvious because of adhesions.
2. In infants, where total correction may be deferred to a later date when the option of a conduit repair is available.
We believe that close scrutiny is most essential at the time of surgery irrespective of the preoperative diagnosis of the anomaly. If a normal sized LAD is present in its normal course upto the apex, an anomalous coronary artery either superficial or intra-myocardial is unlikely. However, if the LAD is too small or absent in its normal location, then great care should be exercised during intra-cardiac repair and one of the options mentioned above may have to be used.
A tailored ventriculotomy parallel to the anomalous LAD has been most widely used1. It has been advised to keep the incision at least 1 cm away from the anomalous coronary artery1. The severity of the RVOT obstruction and the course and tortuosity of the anomalous LAD in relation to the pulmonary annulus should decide the site and number of ventriculotomies1. In seven patients, we used a double ventriculotomy with success (See [Figure:1]). The right atrial approach has been used for repair of all cases of TOF by some authors. A right atrial approach may be used, particularly, when a ventriculotomy is dangerous due to unfavourable coronary anatomy, or when the RVOT obstruction is discrete and low.
Intra-cardiac repair of TOF with anomalous LAD arising from the RCA can be successfully performed using various approaches mentioned above. A pre-operative delineation, though ideal, is mandatory in only specific instances. Close scrutiny and judicious approach are essential for a successful result.