The Miraculous Survival of an Exceptional Baby

The case reported by Ochoa-Ramirez and colleagues¹ in this issue brings new light to an exceptionally rare entity—anomalous origin of all the coronary arteries from the pulmonary (AOCAP)—that is usually considered incompatible with survival.^2–8 The literature on AOCAP was reviewed in detail by Heifetz and co-authors⁷ and, more recently, by Heusch and associates,⁸ who found 30 cases in 1997. The literature is marred by loose definition of the entity. We propose that AOCAP be defined as a cardiac condition in which 2 great vessels are present and the whole of the coronary circulation arises from the pulmonary artery, with any number of coronary ostia. Out of Heusch's 30 cases,⁸ 13 had complex associated anomalies (like common truncus arteriosus and pulmonary atresia) that significantly altered both the clinical presentation and the surgical implications. If those cases are excluded, 17 cases were reviewed by Heusch. For those 17 patients, the mean age at successful surgery or at death was 29.4 days. Only 2 patients had survived surgery at the time that their cases were published.^8,9

Prenatal and Postnatal Pathophysiology

After the age of about 45 days, the human embryonic heart develops a coronary circulation that enables the increased metabolic exchanges required by the compaction of the ventricular myocardium. In animal models, experiments that inhibit coronary embryonic formation have led to early death. However, the presence of AOCAP during fetal life would not be expected to significantly damage myocardial development or function, because the pulmonary pressure is at the systemic level and pulmonary oxygen content and pressure are perfectly adequate for the metabolic requirements of the myocardium. Similarly, the lower fetal body is nourished by pulmonary artery blood, through the ductus arteriosus. Normally, at birth, the pulmonary resistance falls and pulmonary pressure drops to a third or a quarter of the systemic pressure. In newborns who have AOCAP, the combination of low oxygen content and low perfusion pressure results in critical myocardial ischemia. Because all of the coronary arteries are subjected to the sudden onset of unfavorable hemodynamics, myocardial failure or shock ensues, with lethal consequences during the first few days or weeks of life. In the absence of other cardiac defects, the only variables that could play a vital role in averting early death are these:

• Absence of normal maturation of the pulmonary arterial bed (with persistent primary pulmonary hypertension);

• Severe elevation of the left ventricular end-diastolic pressure (leading to secondary pulmonary hypertension); and

• Persistent patency of a large ductus arteriosus (leading to secondary pulmonary hypertension, with increased coronary blood oxygen content).

In the presence of pulmonary hypertension of any of these types, the coronary circulation is essentially preserved. Although the coronary circulation carries unsaturated blood, as in d-transposition of the great vessels, this factor by itself does not cause ischemia, due to the unusual capacity of the myocardium to extract oxygen even at very low-tension regimens.

Unfortunately, in regard to the present case report,¹ we do not know exactly what factors played a role in this infant's early life; however, we are told that the clinical onset of heart failure was abrupt and delayed to around the 2nd month of life, which is not infrequent in AOCAP.^7,8 The authors may be correct in suggesting that a patent ductus occluded spontaneously at that stage, but it is likely that all 3 of the above factors mentioned contributed substantially to the timing of the crisis. In the literature, it is interesting to note that many of the reported patients who had undergone necropsy still had a patent ductus arteriosus.^7,8 It may be useful to emphasize again that the diagnosis of AOCAP—and in general the diagnosis of anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) —is founded upon the classic association of the following symptoms and signs in a newborn:

• New onset of tachypnea, around 1 to 6 weeks after birth;

• New onset of difficulty with feeding (easy fatigability);

• Unexplained distress and crying at nursing, an effort-angina equivalent;

• Paleness, duskiness, and cold perspiration;

• New onset of cardiomegaly (by radiologic or echocardiographic assay), with or without a new murmur of mitral insufficiency;

• Electrocardiographic signs of ischemia (ST-T changes, but not new Q waves as in ALCAPA¹⁰);

• Elevation of cardiac enzymes at the onset of the presenting crisis.

Positive echocardiographic visualization of the coronary origin¹¹ may be difficult, but the lack of normal aortic origin is highly suggestive evidence in this clinical context. Angiographic visualization of the coronary anatomy (demonstration that no coronary arteries originate from the aortic root and that the whole coronary circulation arises from the pulmonary artery) is mandatory and urgent in such a scenario. In 1983, Keeton and co-authors³ first reported the in vivo diagnosis of AOCAP by angiography, but surgical treatment in the sporadic cases that eventually were reported appeared to be marred by a high surgical mortality rate.^7–9 In 1994, Urcelay's group⁹ first reported the survival of 2 infants (aged 3 and 6 months) who had undergone surgical reimplantation for AOCAP.

It must be emphasized that in AOCAP, unlike ALCAPA, the origin of all the coronary arteries from the pulmonary artery prevents the establishment of collateral circulation, which is an aggravating factor in an already critical setting, in terms of the availability both of compensatory functional mechanisms and of larger coronary vessels for surgical repair.

The high reported surgical mortality rate⁸ (75% in the uncomplicated cases reviewed by Heusch's group⁸) imposes the need for a critical review of indications, timing, and techniques of surgical intervention. Although the ominous prognosis of AOCAP in its natural course clearly establishes the need for early firm diagnosis and intervention, it may be useful to stress that priority should be given to the urgency of the intervention within the context of the complexity of the individual case. Apparently, only direct reimplantation of the coronary artery or arteries can be consistently effective in these newborns;^7–9 the interposed grafting procedures are unreliable and a source of postoperative complications.^7,8 Typically, only surgeons at centers that specialize in the switch procedure (of transposition of the great vessels) are qualified for such interventions. In the absence of a specialized center for neonatal coronary surgery, the surgeon should first consider a palliative, simple, and reliable treatment. Palliation by pulmonary banding above the ectopic coronary ostia (a simple and widely available procedure) could be lifesaving, while ensuring the presence of favorable pressure in the coronary artery or arteries, in the expectation of eventual corrective surgery. Obviously, such an option will have to be evaluated in a series of patients that could not likely be collected by any single center. We have promoted the need for a multicenter database of coronary anomalies of unusual kind and severity,¹² and we have recently inaugurated one at the Texas Heart Institute.¹³

The complexity of the coronary surgical anatomy in AOCAP is such that one must consider multiple details, but especially the number of ostia and the topographic location of the proximal ectopic trunks. About 50% of patients with AOCAP have single coronary ostium,⁸ and this creates great difficulties at the outset in mobilizing the coronary cuff and pedicle for surgical transfer in direct reimplantation procedures: kinking and tension could lead to proximal coronary stenosis. As frequently observed in cases of transposition of the great arteries¹⁴—or of ectopic origin of a coronary artery from the opposite sinus of Valsalva with an interarterial course¹⁵—an intramural course (intussusception) of the proximal, ectopic coronary trunk is possible, and this feature would critically complicate the transfer procedure in AOCAP. Unfortunately, the literature is not attentive to this issue, which could be an important reason for some of the high surgical mortality. Most of the reported cases of single coronary artery in AOCAP featured origin from the right pulmonary sinus with a course of the left main trunk between the aorta and the pulmonary artery,^7,8 which is a typical scenario for intussusception. Additionally, the origin of one or both of the coronary arteries from the anterior non-facing sinus¹⁴ has the potential for generating surgical difficulties, while impeding the mobilization of the proximal coronary pedicle.

Bypass coronary surgery, by means of any conduit, is not an appealing technique in the small coronary vessels (about 1 mm in diameter) typically described in newborns who have AOCAP.^8,12 This situation is different from that in patients with ALCAPA, in whom an older age, a larger body size, and the presence of coronary collateral circulation (in part fistulous) with runoff into the pulmonary artery, leading to ectasia, favor surgical intervention. Any kind of surgical conduit (intra- or extrapulmonary) is a quite technically unreliable solution in AOCAP, for it leads to frequent stenosis both of the coronary itself and of the aortic or pulmonary roots, and likely contributes to the surgical mortality rates.

The major message of the present case,¹ as of the 2 previously reported successful interventions,⁹ is that surgical treatment can be life-saving in these unfortunate infants, not only in the short term, but in the long term. In particular, the ominous, poor left ventricular performance of the preoperative state essentially dissolves, with full recovery of left ventricular function, in a manner similar to the dramatic improvement observed after successful surgery for ALCAPA. Indeed, AOCAP, like ALCAPA, seems to feature a type of left ventricular dysfunction that is due more to hibernation than to irreversible infarction (both of them probably occur in any single case, to different degrees).^16,17 Most probably, we should recognize that infantile hearts are also likely to use circulating and resident stem cells for spontaneous regeneration of myocardium, more extensively than do adult hearts with acute myocardial infarction.¹⁸

Paolo Angelini, MD
Texas Heart Institute and St. Luke's Episcopal Hospital, Houston