Localized Bronchiectasis is a Definite Association of Coronaro-Bronchial Artery Fistula

Vascular anastomoses between the coronary arteries and the bronchial arteries were found in 22% of normal subjects and in about 48% of patients with significant coronary artery disease (CAD).1 These vascular anastomoses are congenital in origin, usually small and hemodynamically insignificant. Sizable coronaro-bronchial artery fistula (CBF) is rare. It is described in the literature as individual case reports in about a dozen cases.1–14 Because of the limited number of documented cases, the pathophysiology, natural history and clinical presentation remain unclear. The factors governing the opening and growth of these abnormal vascular channels are still uncertain. Case Report. An 81-year-old man had a long history of angina pectoris. Although the patient was a chronic smoker, he did not have any history of chest symptoms like wheezing attack, dyspnea at rest or copious sputum. Physical examination revealed essentially normal findings. A persantine myocardial tetrofosmin perfusion scan was subsequently performed. It showed an intermediate-sized, moderate reversible perfusion defect in the anteroseptal wall and a mild-to-moderate defect in the inferior wall. He presented again with acute coronary syndrome 6 months later. Electrocardiogram revealed T-wave inversion in V1-3 as well as in the inferior leads. However, the cardiac enzymes were not elevated. Coronary angiography showed that the left main artery had a tubular 30% stenosis. There was a 95% stenosis in the proximal left anterior descending artery (LAD). The mid left circumflex artery (CX) gave rise to a right atrial branch (RAB) approximately 1.7 mm in diameter which continued as a fistula running posteriorly toward the left lung base (Figure 1). The fistula joined the bronchial artery and finally drained into the inferior vena cava (IVC) (Figure 2). There was also a long, 50–60% lesion located distal to the fistula origin in the distal CX. The right coronary artery (RCA) was normal. Left ventriculography revealed impaired left ventricular function with moderate apical hypokinesia. Percutaneous coronary intervention (PCI) was performed on the culprit vessel 2 weeks later. The proximal LAD lesion was stented with a 3.0 x 28 mm Tetra stent (Guidant Corporation, Miami, Florida) deployed at 14 atmospheres. The post-operative course was uncomplicated. Subsequent high-resolution computed tomography (HRCT) of the thorax revealed mild bronchial wall thickening and dilatation compatible with bronchiectasis in the left lung base. There was also consolidation suggestive of recent infection in the area of the bronchiectasis (Figure 3). Chest x-ray showed mild cardiomegaly only, with a clear lung field. Lung function test was within normal limits. The patient remained asymptomatic through subsequent follow-up visits. He declined bronchoscopic examination and further staged procedure on the distal CX lesion. Discussion. Underdeveloped coronaro-bronchial artery vascular anastomoses remain closed because of the similarity in filling pressure in the coronary and bronchial circulation. These vascular anastomoses grow slowly and enlarge to become CBF when there is a considerable and persistent disturbance of the pressure equilibrium. CBF is associated with congenital heart diseases (CHD) like Tetralogy of Fallot (TOF) and pulmonary artery hypoplasia where there is a drop in the pressure in the pulmonary bed.12,13 By the same token, CBF is also associated with increased coronary filling pressure as in the case of supravalvular aortic stenosis.14 Occasionally, the blood flow could even be reversed. In severe CAD, the bronchial-to-coronary artery fistula has been reported to fill the distal coronary bed distal to the proximal obstruction.4,9 There are altogether 12 reported cases of CBF associated with non-CHD.2–11 The clinical characteristics are summarized in Table 1. Localized bronchiectasis is the most common associated condition, which is found in 8 out of the 12 patients (67%). It is interesting that this acquired condition in the lung clustered in a high frequency among patients with a congenitally present condition in a different organ, i.e., the heart. In bronchiectasis, the persistent bronchial wall infection and inflammation causes abnormal dilatation of the bronchial vessel, which results in retrograde filling of the pulmonary artery via the precapillary bronchial-pulmonary artery anastomoses. In 2 of the cases, the pulmonary angiogram failed to opacify the corresponding pulmonary arterioles, which might signify competitive flow from the bronchial circulation.2,3 This abnormal vasodilatation and shunting of blood significantly lower the resistance in the bronchial bed and stimulate the fistula growth. Chest pain is the most frequent presentation among the bronchiectasis patients (6 out of 8 cases). The chest pain is due to coronary steal phenomenon (3 cases), angina pectoris secondary to coronary atherosclerosis in other vessels (2 cases) and atypical chest pain (1 case). The second most common association is CAD, which is present in 4 of 12 cases (33%). Chest pain also represented the most frequent complaint (3 out of the 4 cases) in this category. Interestingly, two patients (17%) presented with recurrent hemoptysis. They were the only 2 cases that had reversed blood flow with bronchial-to-coronary artery fistula. Now the bronchial circulation is the high-pressure chamber. The abnormally dilated, thin wall vessels are prone to rupture and subsequent bleeding. The CX-to-left lower bronchial artery fistula is present in all cases (83%), except the 2 with reversed blood flow (bronchial-to-coronary fistula). The bronchiectasis involvement of the left lower lobe seems to be a prerequisite for the development of CBF. The CX overlies the posterior surface of the heart, which is in close proximity of the left lower lobe of the lung. The posterior pericardial reflection serves as the only point of entry to the heart from the left lower bronchial artery. The pathogenesis of CBF is probably multifactorial and the pressure disequilibrium theory is too simple to explain the pathophysiology. In bronchiectasis, the bronchioles have repeated attacks of infection and suppuration. The inflammatory cells, like polymorphs and monocytes, continue to produce and build up a high local concentration of vasogenic growth factors, which may also contribute to the fistula growth. These vasogenic growth factors act in a paracrine manner. The close proximity of the left lower bronchus and the CX explain why these 2 structures are always involved in CBF. The exact pathogenic mechanism is still uncertain. Most of the CBF remains clinically silent, so that we are actually looking at the tip of the iceberg. We can only detect its presence when it enlarges to a substantial size and causes symptoms. Coronary steal phenomenon is nowadays best treated by percutaneous methods like stent grafts6 or coil embolization.8 There are no data on the long-term prognosis of these treatment modalities. In the presence of concurrent severe CAD, coronary artery bypass graft plus surgical ligation of the fistula is the more definitive treatment.2 In recurrent hemoptysis, while we are performing bronchial artery embolization to stop bleeding, we are also running the risk of embolizing the coronary artery via the fistula.4,9 Alternatively, surgical ligation of the fistula and lobectomy of the bronchiectic segment15 is more definitive in the long run, especially when other troubling chest symptoms such as recurrent pulmonary infection are also present. Conclusion. CBF is a rare vascular anomaly secondary to the enlargement of the pre-existing vascular anastomosis between coronary and bronchial arteries. It probably occurs when there is a persistent disturbance of the pressure equilibrium involving either the coronary, bronchial or pulmonary circulation. Localized bronchiectasis is the most common associated condition among the CBF patients.

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