Anomalous origin of the Left Coronary Artery from the Pulmonary Artery (ALCAPA) is a rare congenital anomaly first described by ABBOTT (1908), with a reported incidence of one in 300,000 live births and accounting for 0.25% of congenital heart diseases 1. Mortality is high in untreated infants and only a few survive to an older age. We report a case of adult-type ALCAPA managed at our institution.
An asymptomatic 15 year old male was evaluated for an incidentally detected continuous murmur over the left third intercostal space parasternally. Clinical examination was otherwise unremarkable. The chest x-ray and electrocardiogram were normal. Colour doppler echocardiography revealed an anomalous LCA draining into the pulmonary artery with left to right shunting. Cardiac catheterization and angiocardiography confirmed the diagnosis of ALCAPA and demonstrated excellent collaterals from the RCA.
Surgery was performed under cardiopulmonary bypass. Due to profuse collateral flow into the LCA even after the aorta was cross-clamped, probably from non-coronary collaterals, cardioplegic arrest of the heart was not possible. The pulmonary artery was opened and brisk back-flow of arterial blood from the anomalous LCA orifice was found. The anomalous opening was sutured from within the pulmonary artery. There was no ischaemic episode following ligation. Post operative course was uneventful.
ALCAPA is a developmental anomaly of the coronary system, explained embryologically by abnormal septation of the concotruncus resulting in the left coronary artery (LCA) being committed to the pulmonary artery (PA), or by involution of the aortic coronary bud with persistence of the pulmonary bud which connects with the developing epicardial vessels.
Although rare, its clinical importance stems from the high mortality in infancy when untreated. No single center has reported a significant number of cases of ALCAPA, but around 300 patients who had undergone investigations and treatment for ALCAPA have been reported worldwide.
The pathophysiologic effects of this condition are directly related to the adequacy of perfusion of the left ventricular myocardium. This in turn depends on the inflow to the LCA from collaterals and the "steal" from LCA to the PA depending on pulmonary vascular resistance (PVR).
Soon after birth, resistance of the pulmonary vasculature is high permitting antegrade flow from the PA to LCA, which perfuses the left ventricle. As PVR falls in the following weeks, flow from the PA to LCA stops, and LV perfusion is totally dependent on collaterals to LCA. If they are poorly developed, death ensues unless immediate surgery is performed. In some cases, collaterals enlarge and after an initial period of LV decompensation, improvement and survival into adulthood occurs - the so called adult type of ALCAPA.
This group that survive the crises of infancy is by no means `normal'. The pulmonary circuit acts as a low resistance siphon, and the collateral flow uses the LCA only as a conduit into the pulmonary circulation, thus bypassing the LV myocardium. This `coronary' steal may cause overt or occult LV ischaemia as well as LV diastolic overload from left to right shunting. The RCA, in accomodating the increased flow from the aorta, becomes dilated, tortuous and thin walled. This increases the risk of thromboembolism and rarely the thin RCA may rupture suddenly.
Do all of these patients need surgery ? The answer to this question has varied with the times. Today with technologic advances in perfusion and surgery, few would argue with the decision to operate on the sick neonate with LV dilatation and failure, ischaemia or infarction2.
Regarding the subgroup of older children and adults with ALCAPA, recommendations for surgery have however been based more on logical reasoning and persuasive arguments than on an objective analysis of the facts.
All of the potential risks of adult type ALCAPA mentioned earlier, along with an observed additional risk of unexplained sudden death 3, have been cited as reasons to advocate surgical correction soon after establishment of the diagnosis.
However, there are no studies comparing operated patients with those managed medically. The oldest reported patient4 lived to age 64 without any symptoms and many patients are first diagnosed on `routine' medical examination.
The surgeon's problem does not end there. Many different operative procedures have been tried for ALCAPA and to choose the most appropriate one for the patient is important. In the past, palliative operations 5 including pulmonary artery banding, aorto-pulmonary anastomosis, internal thoracic artery implantation and pericardial poudrage with de-epicardialization were attempted. Today, definitive correction is the aim. The two accepted corrective procedures for ALCAPA are ligation of the anomalous LCA or reconstruction of a double coronary artery system.
Controversy surrounds the use of simple ligation of the anomalous LCA 6. Though associated with a uniformly poor outcome when performed in infancy, it is considerably safer in the child who has developed adequate LCA collaterals. Of 38 older patients identified in the literature who underwent LCA ligation only one mortality (2.6%) was found. Also, the procedure corrects the altered physiology, which in these patients is mainly related to the pulmonary artery run-off of LCA blood flow. It is a simple operation and may even be performed without cardio-pulmonary bypass.
Conceptually, the idea of a two-coronary artery system is appealing. This can be established in many ways 5 - direct reimplantation of the anomalous LCA into the aorta, aorto-LCA saphenous vein graft, LCA conduits using left common carotid artery, subclavian artery or left internal thoracic artery or by an intrapulmonary tunnel (Takeuchi operation).
The argument that LCA ligation leaves a single coronary artery system which endangers survival is unconvincing. The two widely quoted studies in this regard 7,8 report no statistically significant difference in survival of patients undergoing simple LCA ligation versus two coronary reconstruction. Again, theoretically, in view of varying long term patency rates of grafts to coronary arteries, it appears that occlusion or stenosis may develop in the arterial conduit as well as in the native RCA; thus irrespective of the number of channels there is still a risk of later obstruction with ischaemia.
There is yet another disturbing point. Moodie and co-workers 7 found that three years after saphenous vein grafting, a marked reduction in size of the intercoronary collaterals from the RCA occurred. Late obstruction of such grafts could then be potentially very serious, as the patient is left with the equivalent of left main coronary artery disease.
Our patient underwent simple ligation of the LCA as extensive collateral flow was demonstratable intra-operatively. Another of our patients, a 35 year old female, refused surgery and is under periodic observation. She has had no symptoms or signs attributable to ALCAPA in the past 15 years. Both patients had their diagnoses made almost accidentally while being examined for other complaints. Complete evaluation including ECG, echocardiography, Thallium perfusion scans, cardiac catheterization and angiocardiography showed no evidence of LV ischaemia and dysfunction.
Patients of this type may do well, even in the long term, without surgery, or with simple LCA ligation alone. Analysis of previously reported cases in the literature also supports such a contention. Although two coronary reconstruction may be technically safe, there is no necessity for such a complex operation when simple LCA ligation will suffice.
**Return to Home****To Heart Surgeon's Page****To Heart Breaker's Page****To Hearty Soul's Page**