Background
The echocardiographic diagnosis of anomalous left coronary artery from the pulmonary artery (ALCAPA) can be challenging. The aim of this study was to assess the hypothesis that diagnosis can be enhanced by using supplemental oxygen, which decreases pulmonary vascular resistance and increases retrograde flow from the coronary artery into the pulmonary artery.
Methods
Demographic, echocardiographic, and cardiac catheterization data were reviewed in patients presenting with ALCAPA from 1999 to 2007.
Results
Twenty-one patients (seven male; median age, 5 months) presented with ALCAPA. Nine underwent imaging with oxygen. Two of these nine (22%) had previous standard echocardiographic studies that missed the diagnosis. Cardiac catheterization was required for diagnosis of ALCAPA in 42% of patients who underwent standard echocardiography compared with 11% of patients who received supplemental oxygen in addition to standard echocardiography. The administration of oxygen caused no significant change in heart rate or cardiorespiratory support.
Conclusion
Transient oxygen administration is useful in the noninvasive diagnosis of ALCAPA.
Anomalous left coronary artery from the pulmonary artery (ALCAPA) occurs in one in 300,000 live births. When the left coronary artery arises from the low-pressure, deoxygenated pulmonary artery instead of the high-pressure, oxygenated aorta, the left ventricle may become inadequately perfused, and myocardial ischemia occurs. Age and severity of presentation depend on the development of collateral coronary circulation and on pulmonary vascular resistance. Infants who have not had an opportunity to develop collateral vessels typically present at 6 to 8 weeks of life, when pulmonary vascular resistance falls, with dilated, poorly functioning left ventricles and mitral valve regurgitation. These infants typically present with dyspnea, tachypnea, tachycardia, wheezing, cough, and occasionally secondary cyanosis. Electrocardiography is diagnostic for infarction in 80% of infants presenting with ALCAPA, demonstrating a QT pattern in leads I and aVL and the left precordial leads, with a Q wave of ≥4 mm and T-wave inversion. Echocardiographic features consistent with the diagnosis of ALCAPA include visualization of low velocity, diastolic flow in the pulmonary artery, dilation of the right coronary artery, and retrograde flow in the abnormal left coronary artery. Diagnosis can sometimes be achieved on the basis of echocardiography alone, but cardiac catheterization may be required for confirmation. Most infants presenting with ALCAPA are acutely ill with severe congestive heart failure, and cardiac catheterization carries higher risk in this patient population. In 2002 we made the observation that supplemental oxygen enhanced visualization of the diastolic flow into the main pulmonary artery from an anomalous left coronary, likely because of a decrease in pulmonary vascular resistance. Upon review of the literature, we did not encounter any reported experience with this technique. The aim of this review is to report our experience with the use of supplemental oxygen and to test our hypothesis that oxygen improves our ability to noninvasively diagnose ALCAPA.
Methods
Our echocardiographic database was queried for patients diagnosed with ALCAPA between January 1999 and December 2007. Age, body surface area, echocardiographic views, the use of oxygen, escalation of care, heart rate, and requirement for cardiac catheterization for diagnosis were retrospectively reviewed. Any infant presenting with a dilated left ventricle, echo-bright papillary muscles, and mitral valve regurgitation underwent intensive imaging of the coronary arteries according to our laboratory protocol. Beginning in 2002, transient oxygen was often used in patients with suspicion of ALCAPA at the discretion of the attending cardiologist. A complete echocardiographic study with special attention to coronary artery anatomy in the parasternal short-axis and long-axis views by two-dimensional imaging, as well as color and pulse-wave Doppler, was performed. Occasionally, a subcostal long-axis view was used if there were poor acoustic windows on parasternal views. An attending cardiologist would then be present at the bedside for additional imaging. Oxygen was administered by nasal cannula or endotracheal tube at 100% fractional inspired oxygen for 10 minutes. Additional coronary artery imaging was then performed. Echocardiographic findings raising the suspicion for ALCAPA include a prominent or large right coronary artery, diastolic flow in the main pulmonary artery, or reversal of flow in the left main, circumflex, or left anterior descending coronary artery. Enhancement of diastolic flow in the main pulmonary artery and/or reversal of flow in the left coronary system with supplemental oxygen was diagnostic for ALCAPA. The oxygen was quickly weaned at the end of the study. Heart rate and escalation of care, such as changes in ventilatory support or additional medical therapy, were noted from the medical record. The institutional review board approved this retrospective review with a waiver of informed consent.
Statistical Analysis
All values are given as medians. Wilcoxon’s signed rank test was used to compare continuous variables.
Results
Twenty-one patients (seven male; median age, 5 months; age range, 1.5 months to 16 years) were diagnosed with ALCAPA between 1999 and 2007. Twelve patients underwent conventional echocardiography. Nine patients were given 100% fractional inspired oxygen to assist in diagnosis ( Table 1 , Figure 1 ). Two of the nine patients (22%) diagnosed with ALCAPA while using supplemental oxygen had previous standard echocardiographic studies that missed the diagnosis. Among the 12 patients who did not receive supplemental oxygen, cardiac catheterization was required to confirm the diagnosis of ALCAPA in five patients (42%). Of the nine patients who were given oxygen during echocardiography, only one (11%) required cardiac catheterization for diagnostic confirmation. One additional patient underwent cardiac catheterization at the surgeon’s request to better assess a possible dual left anterior descending artery, but the diagnosis of ALCAPA was obvious by echocardiography while receiving oxygen. Thus, only 22% of patients using transient supplemental oxygen during echocardiography required cardiac catheterization for any purpose.
| Patient | Sex | Age at diagnosis | Supplemental oxygen | Cardiac catheterization | Surgery performed | Year of diagnosis |
|---|---|---|---|---|---|---|
| 1 | Male | 4 months 22 days | No | No | Yes | 1999 |
| 2 | Male | 1 year 2 months | No | Yes | Yes | 2000 |
| 3 | Male | 15 years 7 months | No | No | No | 2000 |
| 4 | Female | 1 month 22 days | No | Yes | Yes | 2001 |
| 5 | Female | 2 months 0 days | No | No | Yes | 2001 |
| 6 | Female | 2 months 14 days | No | No | Yes | 2001 |
| 7 | Female | 8 years 0 months | No | Yes | Yes | 2002 |
| 8 | Female | 7 months 7 days | No | Yes | Yes | 2002 |
| 9 | Female | 4 years 5 months | No | No | Yes | 2002 |
| 10 | Female | 6 months 1 day | Yes | No | Yes | 2002 |
| 11 | Male | 4 months 18 days | No | No | Yes | 2003 |
| 12 | Male | 5 months 0 days | No | Yes | Yes | 2003 |
| 13 | Female | 6 months 14 days | Yes | No | Yes | 2004 |
| 14 | Female | 4 months 24 days | Yes | Yes | Yes | 2004 |
| 15 | Male | 2 months 9 days | Yes | No | Yes | 2005 |
| 16 | Female | 1 month 16 days | Yes | No | Yes | 2006 |
| 17 | Female | 1 month 29 days | Yes | No | Yes | 2006 |
| 18 | Female | 2 months 2 days | Yes | No | Yes | 2006 |
| 19 | Male | 5 months 16 days | No | No | Yes | 2007 |
| 20 | Female | 16 years 9 months | Yes | No | No | 2007 |
| 21 | Female | 4 months 22 days | Yes | Yes | Yes | 2007 |
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