Discussion
Pulmonary embolism represents the third leading cause of cardiovascular mortality. The technological landscape for management of acute intermediate and high-risk PE is rapidly evolving. Patients with large PE and RV strain, even if normotensive, are at high risk of in-hospital and latent mortality (3).
The current American Heart Association (AHA) Guidelines has a Class IIa recommendation for treating patients with intermediate high-risk PE (biological markers positive, enlarged RV on echocardiography, and SBP of more than 90 mmHg) and high-risk PE (SBP less than 90 mmHg, enlarged RV, and shock) (4). Although aggressive intervention including systemic and catheter directed thrombolysis has been recommended in patients with high and intermediate high-risk PE and hemodynamic compromise, this approach remains controversial in hemodynamically stable patients (5).
The presence of mobile RHT with high-risk PE associated with RV dysfunction carries increased early mortality beyond the presence of PE alone. The presence of RHT at the time of acute PE was found to predict all-cause death, PE-related death, and recurrent venous thromboembolism, particularly in patients without hemodynamic compromise (6). However, there is no consensus regarding the optimal treatment for this difficult clinical situation.
Rose P. et al and colleagues analyzed 177 cases of right heart thromboembolism (1). Pulmonary thromboembolism was present in 98% of the cases. The treatments administered were none (9%), anticoagulation therapy (35.0%), surgical procedure (35.6%), or thrombolytic therapy (19.8%). The overall mortality rate was 27.1%. The mortality rate associated with no therapy, anticoagulation therapy, surgical embolectomy, and thrombolysis was 100.0%, 28.6%, 23.8%, and 11.3%, respectively. They concluded that age and gender were not associated with mortality rate, but thrombolytic therapy was associated with an improved survival rate (p < 0.05) when compared either to anticoagulation therapy or surgery.
The three patterns of RHT have been described. Type A thrombus are morphologically serpiginous, highly mobile, and associated with deep vein thrombosis and PE. It is
hypothesized that these clots embolize from large veins and are captured in-transit within the right heart. Type B thrombi are nonmobile and are believed to form in situ in association
with underlying cardiac abnormalities while type C thrombi elicit intermediate characteristics of both type A and type B (7). Our patient presented a serpiginous thrombus moving
through the tricuspid valve to the right ventricle compatible with a type A thrombus.
In view of the reported high mortality, the coexistence of high-risk PE in conjunction with RHT is regarded as a medical emergency and requires immediate treatment. Contemporary treatment modalities for high-risk PE vary, ranging between anticoagulation alone, systemic thrombolysis, CDT, and surgical pulmonary embolectomy. However, the optimal management of PE associated RHT remains unclear due to the low number of cases and the lack of randomized controlled trials.
Surgical Pulmonary embolectomy with exploration of the right heart chambers and pulmonary arteries under cardiopulmonary bypass is another treatment option (8). However, it is not immediately available in many centers and it carries the risk of general anesthesia, cardiopulmonary bypass, and the inability to remove coexisting pulmonary emboli beyond the main pulmonary arteries. It should be considered particularly for cases in which thrombolysis is contraindicated or ineffective. On the other hand, systemic thrombolysis carries a 22% risk of major hemorrhage including a 3% risk of intracranial hemorrhage as well as a high risk for fragmentation and distal embolization when used for large mobile thrombus leading to recurrent PE (9).
Emerging catheter-directed therapies for RHT and high- risk PE include percutaneous catheter-directed thrombolysis or ultrasound accelerated catheter directed thrombolysis (UACDT); mechanical thrombectomy using fragmentation and a capture device; and endovascular aspiration of the clot directly from within the atrium, ventricle, or pulmonary arteries (10,11). These methods are also promising in patients with RHT with some successful cases reported (12,13). However, there is still a lack of general availability and expertise.
The emergence of UACDT as a method of local thrombolytic delivery provides another possible treatment modality. The ultrasound waves accelerate the fibrinolytic process by enhancing catheter directed thrombolysis. This in turn reduces the treatment time and total thrombolytic dose resulting in less risk of bleeding (14). Shammas et al. reported successful EKOS use with complete resolution of the thrombus 24 hours later as evidenced by echocardiogram (15).
The presence of a right heart thrombus is rare, and it is unlikely that a randomized trial with two or three different treatment arms would be performed in the near future. Thus, choice of therapy is based on the physician’s discretion and clinical judgment and based on availability and patient factors that often preclude the development of one-size-fits-all treatment algorithms. In this case, a favorable course with complete thrombus dissolution and right ventricle function recovery was observed with EKOS Acoustic Pulse Thrombolysis.