Pulmonary balloon angioplasty for chronic thromboembolic pulmonary hypertension

Clinical presentation

Patients with CTEPH present with dyspnea and/or signs of right-sided heart failure. CTEPH may be suspected when there are persistent symptoms after 3 months of anticoagulation after an acute pulmonary embolus. This disease can be suspected from the history, including risk factors for hypercoagulable states, signs, and symptoms, along with ancillary testing, which includes electrocardiography (showing right ventricular strain pattern), chest radiography, pulmonary function testing, and echocardiography. Clues from these can raise the suspicion of the presence of CTEPH and exclude other causes of dyspnea.

Diagnosis and testing

If CTEPH is suspected, the next step is to perform ventilation–perfusion lung scintigraphy (V/Q scan). This test has a high sensitivity of detecting perfusion defects and a high negative predictive value, so CTEPH can be excluded if normal.

If the V/Q scan reveals perfusion defects, the next step would be to perform confirmatory testing, which includes pulmonary computed tomography angiography (CTA) and right heart catheterization with pulmonary angiography. Pulmonary CTA is effective in detecting thromboembolic material in the main and lobar segments of the pulmonary vasculature; however, it is less sensitive in detecting segmental and subsegmental lesions.

Perfusion single photon emission computed tomography (SPECT)/CTA is a more recent modality that integrates anatomic and perfusion data and provides additional data for diagnosis and procedural planning ( Fig. 30.1 ). Right heart catheterization is needed to measure baseline pulmonary pressures and pulmonary vascular resistance and directly image the pulmonary arteries with pulmonary angiography. Pulmonary angiography is highly sensitive in detecting segmental and subsegmental thromboembolic material, which is important for decision-making in treating CTEPH.

How to perform pulmonary angiography

• 1.

  Using a balloon wedge pressure catheter (Teleflex, Morrisville, NC) positioned in the right or left pulmonary artery, insert a regular 0.035″ guidewire and exchange the balloon wedge catheter for a 7F 145-cm pigtail.

• 2.

  Position the pigtail in the main left or right pulmonary artery. Connect the pigtail to a power injector and inject 60 cc (±10 cc) of contrast into each pulmonary artery.

• 3.

  In conventional biplane angiography, the left or right lung is placed in the isocenter with straight left ascending oblique (LAO) and anteroposterior (AP) projections at a 90-degree angle. Image acquisition is set to the digital subtraction angiography mode at a rate of four frames per second. The patient is asked to hold their breath, and contrast is injected. Cine acquisition should be set up to have a long enough duration to acquire the pulmonary flow in the arterial phase, followed by the levo-phase where pulmonary venous drainage flow can be assessed.

• 4.

  As an alternative, rotational angiography can be performed using a C-arm that is equipped with the capability and software to perform rotational image acquisition and image reconstruction. The right or left lung is again positioned in the isocenter. Contrast is injected while cine acquisition is performed with the C-arm rotating around the isocenter, obtaining a series of x-ray images. With this modality, contrast is injected at 12 to 14 cc/second, and image acquisition is initiated 2 seconds after the initiation of contrast delivery to adequately opacify the vasculature. The images are then reconstructed using special software into a three-dimensional pulmonary tree. Rotational angiography permits a more thorough assessment of overlapping vasculature and may assist in procedural planning and camera positioning during subsequent interventions.

Pulmonary angiographic images are then reviewed to look for lesions that commonly present as ostial narrowing, total occlusions, and hypoperfused arteries with poor microvascular blush and delayed venous return.

Case selection

Location and severity of lesions identified on CTA (for central lesions) and pulmonary angiography (for peripheral lesions) is key for the management of CTEPH. As a rule of thumb, the more distal the involvement of thromboembolic material in the pulmonary tree, particularly in segmental and subsegmental branches, the more challenging, higher-risk, and less successful surgical thromboembolectomy becomes. Therefore thromboembolic material involving the central vasculature is a favorable anatomy for surgical thromboembolectomy, and this is the treatment of choice. However, if the thromboembolic material involves the distal branches, then surgical resection becomes very challenging and often not feasible.

Pulmonary balloon angioplasty is used in patients with thromboembolic lesions in the distal pulmonary vessels that are not amenable for surgical resection. Angioplasty can also be offered in a hybrid procedure for patients who have central and peripheral thromboembolic involvement, whereby they undergo surgical resection of the central lesions and then are brought back for balloon pulmonary angioplasty of residual disease in the segmental and subsegmental territories.

Medical therapy is the first step if the patient has distal involvement and is not found to be a surgical candidate. Currently the only pharmacologic agent approved for CTEPH is riociguat, a soluble guanylate cyclase stimulator. This promotes pulmonary artery dilatation. Patients are given a trial of 6 to 8 weeks followed by a repeat right heart catheterization along with additional objective reassessment of exercise limitation. If no improvement is observed with medical therapy, pulmonary balloon angioplasty would be the next step.