San Diego, CA
Hospital and Institute Affiliations
UC San Diego Health
Pulmonary, Critical Care, and Pulmonary Vascular Disease
Which patients diagnosed with acute pulmonary embolism (PE) should be evaluated for chronic thromboembolic pulmonary hypertension (CTEPH)?
The expectation for a patient following a pulmonary embolism (PE) should be to return to their pre-PE baseline. If they have shortness of breath that is worse than at baseline, evaluation of their dyspnea is warranted and chronic thromboembolic pulmonary hypertension (CTEPH) and chronic thromboembolic disease should be high on the differential diagnosis.
What is the pathophysiology underlying the evolution of PE to CTEPH? What clinical factors can be addressed to decrease the odds of persistent perfusion defects post-PE?
After an acute PE, patients receive anticoagulation therapy, but even if this is adequate approximately 30% of patients will have persistent perfusion defects at 6 months.There are a number of factors that can have an impact on whether or not anticoagulation therapy resolves a patient’s perfusion or persistent perfusion defects. Some clinical factors in an acute PE include the initial size of the thrombus, a delay in the initiation of anticoagulation therapy, or the presence of right ventricular (RV) strain at diagnosis.These factors, in addition to factors such as chronic inflammation and impaired fibrinolysis, may also influence whether a clot resolves or persists.
What is your general diagnostic algorithm when addressing persistent dyspnea post-PE?
Following an acute PE, I see patients at my follow-up clinic 3 to 6 months after beginning anticoagulation therapy. By 3 months, the expectation is that most of the resolution that is going to occur has occurred.By that time, patients should be back to their pre-baseline level of functioning and should not have any worsening dyspnea compared with baseline. If they have persistent dyspnea, they should continue to take an anticoagulant and the etiology of the dyspnea should be evaluated.Persistent perfusion defects should be high in the differential diagnosis, so I would obtain a ventilation/perfusion scan to screen for resolution of the PE. If defects persist, I would perform transthoracic echocardiography and potentially a right-heart catheterization and pulmonary angiogram.
Once the diagnosis of CTEPH is established, the patient needs to be referred to a center that specializes in the surgical treatment of patients with chronic thromboembolic disease.
One of my research interests is determining the physiologic etiology of dyspnea in patients following PE. Currently, a standard ventilation perfusion scan requires radiation to screen patients who are dyspneic following a PE.
We are working on a protocol that uses cardiopulmonary exercise testing to look for changes in dead space ventilation and O2 pulse, which can be used as a surrogate for stroke volume, to assess whether or not there are physiologic fingerprints of perfusion defects present following anticoagulation.
What are the challenges associated with differentiating CTEPH from massive PE?
The challenge is that the presentation of both CTEPH and massive PE can be similar. RV failure, no matter what the etiology, presents in a similar fashion. So the patients with either can have shortness of breath, chest pain, or even syncope.Hemoptysis can be seen in a similar percentage of patients with acute PE and CTEPH, although the etiology is different. In acute PE, it tends to be capillary bleeding in an area of pulmonary infarction, whereas in CTEPH it is bleeding from bronchial artery collateral vessels.When we are seeing patients with signs of RV failure and evidence of a pulmonary artery clot, we should ask ourselves whether this is due to acute PE or acute-on-chronic pulmonary emboli.
And some of the features that can differentiate acute PE from acute chronic pulmonary emboli are the presence of bronchial artery collateral vessels, the presence of right ventricular hypertrophy, and a very high RV systolic pressure on echocardiogram, which tells you that the RV has had time to remodel and generate that high pressure.
Can you discuss radiographic CT features that assist the pulmonologist in diagnosing CTEPH?
There are some differences on computed tomography (CT) scan in the appearance of a chronic clot compared with an acute clot. These include pouch defects, in which large bulky clots occlude the entire vessel with no flow to distal segments. Thuere may be thickening of the pulmonary artery that occurs eccentrically along the pulmonary artery wall, rather than the typical donut-hole, in which there is an acute clot in the middle of a pulmonary artery with contrast flowing around it. Yo can see a mosaic perfusion pattern on the CT lung window, although that is nonspecific for CTEPH.Those are the things I look for when I’m looking at a CT scan and evaluating a patient who presents with a massive PE. I perform those tests before placing an Ekosonic Endovascular System (EKOS) catheter or considering thrombolysis.
Disclosures: Dr Fernandes has disclosed receiving consulting fee from Bayer pharmaceuticals and research funding from Actelion.