Pulmonary artery stenosis is one of the most common complications after arterial switch operation in patients affected by transposition of great arteries. Reference Fricke, Buratto and Weintraub1 Nowadays, mid-term results of arterial switch operation are excellent, but many patients require reintervention. In particular, reported incidence of significant pulmonary artery stenosis ranges from 3.8 to 28%. Reference Ruys, van der Bosch and Cuypers2
The mechanism of pulmonary artery stenosis is related to the Lecompte manouvre, that stretches the branch pulmonary artery while moving the pulmonary artery bifurcation anterior to the aortic root. Stent implantation is a feasible and effective option for the treatment of pulmonary artery stenosis with a low complication rate. Reference Zablah and Morgan3
Nevertheless, pulmonary artery stenting in arterial switch operation patients presents a particular and unique higher risk. The position of the reimplanted coronary arteries in proximity of branch pulmonary artery exposes this population of patients to a greater risk of coronary arteries compression during pulmonary artery stenting procedure. Reference Lee, Shahbah and El-Said4,Reference Van Gameren, Witsenburg and Takkenberg5,Reference Hamzeh, El-Said and Moore6,Reference Morgan, Pushparajah and Narayan7
We present the case of a patient with transposition of great arteries and pulmonary branch stenosis after arterial switch operation, where coronary artery compression was avoided by balloon testing the landing zone of the left pulmonary artery stent.
Case report
A 15-year-old girl, 97 kg, affected by transposition of great arteries with usual pattern of coronary arteries and aortic valve stenosis was referred to our catheterisation laboratory for bilateral pulmonary artery stenosis. At 4 days of life, she underwent arterial switch operation with a 10 mm Goretex conduit interposition between the right ventricle and the pulmonary arteries. At the age of 4 years, the Goretex conduit was explanted, and the right ventricular outflow tract was reconstructed with a homograft patch. Despite asymptomatic, the transthoracic echocardiogram and the subsequent angio-MRI revealed severe bilateral pulmonary artery stenosis with right ventricular hypertension and hypertrophy.
The case was discussed collegially, and the decision was to perform a catheterisation with pulmonary artery stenting. Under general anaesthesia, a routine diagnostic catheterisation was performed, and bilateral pulmonary artery stenosis was confirmed, particularly of the left PA (Fig. 1). The right ventricle pressure was 2/3 the systemic pressure, and the peak systolic gradient of right pulmonary artery and left pulmonary artery were 25 and 35 mmHg, respectively. At aortography, aortic root was slightly dilated and the proximal part of the left coronary artery seemed very close to the left pulmonary artery origin.
Figure 1. Angiography of the left PA.
Suspecting the proximity of the stents' landing zone to the reimplanted coronary arteries, we decided to test them by inflating two balloon-in-balloon balloons 16 mm × 40 mm (NuMed, Inc., Hopkinton, NY, USA) in both pulmonary arteries. The size of balloons was decided on the basis of distal diameter of both Pas (15 mm) and was mimicking future final stent diameter. Simultaneously, an aortography was running. The aortography and the following selective coronarography clearly demonstrated the compression of the left coronary artery by the balloon inflated in the left pulmonary artery (Fig. 2). At EKG was detected a ST segment depression that promptly disappeared after balloon deflation.
Figure 2. Selective coronarography demonstrated the compression of the left coronary artery by the balloon inflated in the LPA.
The procedure was then aborted. and the patient was referred to surgery.
Discussion
Significant pulmonary artery stenosis is common after arterial switch operation in transposition of great arteries and exposes patients to unbalanced flow towards the lungs, right ventricle work overload, increasing the risk of right ventricle dysfunction and arrhythmia. Reference Fricke, Buratto and Weintraub1 In this setting, pulmonary artery stenosis balloon dilation is often not effective as the mechanism of stenosis is related to the distortion and stretching of the pulmonary artery after Lecompte manoeuvre. For this reason, stenting is considered the procedure of choice in selected cases, especially because many stents can be dilated until an adult diameter. However, this procedure presents a high complication rate in this population due to the proximity of the neo-aortic root, reimplanted coronary arteries, and pulmonary arteries, leading to risk of coronary compression, aortopulmonary fistula, and aortic root distortion. Reference Zablah and Morgan3,Reference Lee, Shahbah and El-Said4,Reference Van Gameren, Witsenburg and Takkenberg5,Reference Hamzeh, El-Said and Moore6
There are few studies focusing on catheter-based intervention in patients with transposition of great artery after arterial switch operation and Lecompte manoeuvre and the results are variable.
Some reports Reference Michalak, Moll and Bobczak- Budlewska8,Reference Nellis, Turek, Aldoss, Atkins and Ng9 described the use of balloon angioplasty for pulmonary artery stenosis after arterial switch operation with no reported adverse events but procedural data and early and mid-terms results are lacking.
Only a recently published report Reference Lee, Shahbah and El-Said4 analysed the results of percutaneous treatment on pulmonary artery stenosis after arterial switch operation. Lee et al described 37 catheterisation procedures performed in 29 patients, which included angioplasty and/or stenting of pulmonary artery. The reported incidence of major complications was 14% (five patients) and included three aortopulmonary fistulae and one coronary compression, all described during stent positioning or dilatation. In addition, they described six (16%) intended stent procedures, which were aborted because of a high risk of coronary compression. In every examined case, the compression of reimplanted left coronary artery was due to the proximity to the pulmonary arteries. They highly recommended to routinely perform coronarography and 3D rotational aortography with or without sizing balloon for the evaluation of the proximity of coronary arteries and pulmonary stents landing zones.
The importance of a detailed morphological work-up using MRI or multislice CT to understand the anatomical substrate was also highlighted in a multicentre study about pulmonary artery stenting in CHD, and this is particularly important in detecting the relationship between pulmonary artery and coronary arteries. Reference Van Gameren, Witsenburg and Takkenberg5 This case report highlights the importance of routinely performed coronary compression testing as a pre-stenting evaluation to identify patients with complex anatomy who are not candidates for stent implantation. Our patient was corrected with arterial switch operation and right ventricle to pulmonary artery conduit which might have contributed to modify the spatial arrangement between the coronaries and the pulmonary arteries.
This simple test can help in the patient selection and avoid coronary compression, which can be a life-threatening complication requiring urgent coronary stenting with concerning long-term outcome.
In conclusion, our case report underlines the possibility of introducing the coronary compression testing as a routine test before pulmonary arteries stenting in patients at high risk for stenting complication due to complex anatomies.
