Correction of Hemitruncus in an Adult Patient Alleviated Pulmonary Arteriovenous Fistula in the Affected Lung

Introduction

Anomalous origin of the pulmonary artery from the aorta, which is also known as hemitruncus, is a rare congenital cardiac anomaly. In patients with hemitruncus, the affected lung is perfused at systemic pressure, and the remaining lung is exposed to the entire output of the right ventricle. The majority of these patients are treated surgically during infancy, and there is little information about hemitruncus diagnosed during adulthood.^1–3

Pulmonary arteriovenous fistula (PAVF) is known to develop due to the exclusion of hepatic venous blood or “hepatic factor (HF)” to the lung. ⁴ Surgical inclusion of hepatic venous blood in the pulmonary circulation can result in the resolution of PAVF.^5,6

We encountered an adult patient with right hemitruncus with pulmonary hypertension (PH) and a right PAVF. We successfully performed a definitive repair and follow-up selective contrast echocardiography showed substantial regression of the PAVF.

Case Report

A 36-year-old woman was referred to our institution for surgical intervention. She had suffered from hemoptysis during her teenage years, but her cardiac condition was not accurately assessed during that time. She visited another hospital with the chief complaints of chest discomfort and dyspnea on exertion. Enhanced computed tomography (CT) showed anomalous origin of the right pulmonary artery (RPA) from the ascending aorta (hemitruncus) (Figure 1A) and a small patent ductus arteriosus (PDA).

OPEN IN VIEWER

Figure 1.

Multidetector computed tomography showed anomalous origin of the right pulmonary artery from the aorta preoperatively (A) and the reconstructed right pulmonary artery using an artificial graft postoperatively (B).

Cardiac catheterization demonstrated that the pressure in the left pulmonary artery (LPA), the RPA, and the aorta were 77/13/45, 151/70/103, and 146/70/102 mm Hg, respectively. The pulmonary vascular resistance estimated by cardiac catheterization and magnetic resonance imaging was 8.5 WU/m². Selective contrast echocardiogram (agitated saline injection into the RPA) during cardiac catheterization demonstrated a moderate amount and prompt appearance of echo contrast in the left atrium. Echocardiogram demonstrated moderate mitral regurgitation (MR) (central regurgitation) with a left ventricle end-diastolic diameter (LVEDd) of 66 mm.

The patient was placed on cardiopulmonary bypass in the standard fashion, using ascending aortic and bicaval cannulation. Ligation and division of the PDA were performed, and then cardiac arrest was established and an atrial septal fenestration of 4 mm was created through a right atriotomy. Next, a woven Dacron graft (12 mm in diameter) was employed to connect the RPA and main pulmonary artery via an end-to-side anastomosis (5-0 polypropylene, double-stitch; Figure 2).

OPEN IN VIEWER

Figure 2.

Intraoperative photograph. The right pulmonary artery was divided and the aortic wall was repaired with a 5-0 polypropylene running suture (double-stitch) (A). A woven Dacron graft (12 mm in diameter) was employed to connect the RPA (B) and the main pulmonary artery (C and D) with a 5-0 polypropylene running suture (double-stitch).

Epoprostenol infusion and nitric oxide inhalation were discontinued on postoperative day 2 and 3, respectively. Tadalafil, macitentan, selexipag, aspirin, and warfarin were initiated during hospitalization. Right heart catheterization on postoperative day 27 demonstrated that the pressure in the LPA and RPA were 46/11/26 and 42/11/25 mm Hg, respectively. The pulmonary vascular resistance estimated by cardiac catheterization was 4.1 WU/m². The patient was discharged without major complications on postoperative day 32.

A thorough postoperative examination was performed 6 months after surgery. Enhanced CT (Figure 1B) and cardiac catheterization demonstrated unobstructed flow within the graft. The pressure in the LPA and RPA were 42/9/21 and 30/9/17, respectively. The pulmonary vascular resistance estimated by cardiac catheterization was 3.8 WU/m². Selective contrast echocardiogram showed no residual PAVF. Echocardiography demonstrated mild MR with LVEDd of 51 mm. A lung perfusion scan showed the ratio of right to left pulmonary blood flow had improved from 10.4% to 89.6% (predischarge) to 16.3% to 83.7% (6 months postsurgery). A lung perfusion scan revealed that the estimated shunt ratio ([wholebody – lung] / wholebody) had also improved from 11.2% (predischarge) to 5.0% (6 months postsurgery). The triple therapy (tadalafil, macitentan, and selexipag) is being continued at the time of this writing and we plan to discontinue these drugs sequentially after the next cardiac catheterization.

Discussion

Although the cause of diffuse PAVF is unknown, the absence of HF in pulmonary blood flow is believed to be a predisposing factor.^4–6 Usually, the initial symptom of PAVF is hypoxia. However, in a patient with right hemitruncus, the right lung is perfused with fully oxygenated blood, and the progression of PAVF never causes hypoxia. This feature might result in delayed diagnosis of PAVF. If the selective contrast echocardiography was performed routinely in patients with hemitruncus, it is possible that diffuse PAVF would be found more frequently.

We speculated that HF was consumed mostly by the left lung and was excluded from the right lung in patients with right hemitruncus. ⁶ Pulmonary arteriovenous fistula in this patient was not localized ⁷ but diffuse (undetectable by enhanced CT); therefore, we predicted that this diffuse PAVF could be acquired (not congenital PAVF) due to the lack of HF; therefore, this PAVF could be improved by inclusion of HV blood flow to the RPA by the definitive repair.

It may be argued that RPA banding (RPAB) may be less invasive than definitive repair. ⁸ The definitive repair of hemitruncus in adulthood is a high-risk procedure. To the best of our knowledge, definitive repair for hemitruncus complicating a PAVF has not been reported. However, the RPAB might result in a proximal pulmonary artery aneurysm and the right PAVF might not be cured. Several meetings were held and we explained to the patient and her family the benefit and risk of both definitive repair and RPAB in detail. After informed consent was obtained, a definitive repair was selected.

Preoperative pulmonary vascular resistance estimated by cardiac catheterization and magnetic resonance imaging was 8.5 WU/m². Therefore, in the strict sense, surgical intervention might have been contraindicated. However, in PH related to congenital heart disease in adults, no prospective studies have found a reliable hemodynamic cutoff to predict the reversibility of PH. ³ To manage the present patient, who had severe PH and to prevent a PH crisis, epoprostenol infusion and nitric oxide inhalation were administered intra- and postoperatively. Furthermore, the triple pharmacological therapy will be continued for a prolonged period. However, it must be noted that RPAB is definitely a useful surgical option for “irreversible” PH, especially with life-threatening hemoptysis. ⁸

We assumed that after the RPA reconstruction in the presence of PAVF, the right-to-left shunt could result in desaturation. However, the extent of desaturation could not be predicted in advance. Adult patients with hemitruncus will develop severe PH of the affected lung preoperatively.^1–3 In such cases, after the RPA reconstruction, the majority of the pulmonary blood flow can flow to the left lung. To prevent postoperative desaturation, we chose a slightly narrow graft (12 mm in diameter). In fact, the patient did not suffer from desaturation before the disappearance of PAVF postoperatively. If postoperative desaturation had become a problem, we planned to place an RPAB on the artificial graft.