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.