Case Report
A 53 year old male with a past medical history of high-grade glioma and
recent brain surgery presented to ED after a syncopal episode. His head
computed tomography (CT) was negative for intracranial hemorrhage or
infarct. Simultaneous Chest CT- PE protocol (2 mm slices) noted large
saddle pulmonary embolism with significant clot burden (Figure 1a, b).
It revealed a “snake like” thrombus in the right atrium suggesting
free floating clot with significant right heart (RH) strain (Figure 2a,
b). The N-terminal pro-B-type natriuretic peptide (NT-proBNP) was 832
pg/mL (Ref Range: <=300 pg/mL), and Troponin I 0.91 ng/mL (Ref
Range: 0.00 - 0.03 ng/mL). Bilateral lower extremities venous Doppler’s
reported acute vein thrombosis in the left popliteal vein. The patient
was transferred to the intensive care unit (ICU) with a heart rate (HR)
of 127 beats/min, systolic blood pressure of 120 mmHg, and peripheral
capillary oxygen saturation (SpO2) of 92% on 6 liters
of oxygen in a non-rebreather. Full anticoagulation with unfractionated
Heparin was started. The use of thrombolysis was precluded given his
neurological status. Interventional radiology and cardiothoracic surgery
(CTS) were consulted for possible mechanical thrombectomy of pulmonary
embolism and clot in the right atrium (RA).
The patient was sedated and monitored by cardiovascular anesthesia.
Additional venous and arterial 6 Fr vascular sheaths were inserted to
anticipate any urgent transition to extracorporeal membrane oxygenation
(ECMO). Through a right common femoral vein approach, a catheter was
advanced into the inferior vena cava (IVC). IVCgram demonstrated clot
extending from the IVC into the RA (Figure 3a, b). Given the potential
risk of dislodging clot that could increase the PA pressure, the
Triever20 catheter (Inari Medical Inc., Irvine, CA, USA) was inserted
for mechanical thrombectomy. Suction thrombectomy was performed at the
level of the IVC confluence and RA under fluoroscopic guidance. Moderate
amount of clot was aspirated (Figure 4) and resolution was confirmed
with a follow up cavogram. The main PA was accessed using a 6 Fr, 100 cm
Vert catheter. The initial main PA pressure was elevated (46/13 mmHg,
mean of 38 mmHg). Pulmonary angiography demonstrated extensive saddle
embolism (Figure 5a, b, c). Next, the Triever20 catheter was advanced to
the left PA and a large amount of clot was retrieved from the segmental
branches with minimal residual thrombus. The self-expanding nitinol
disks of the device were not required given the results obtained with
aspiration. The same intervention was repeated in the main and right PA
with improvement of PA pressures (28/ 9 mmHg, mean 14mmHg) and oxygen
demand. The blood loss was approximately 150 cc and there was no change
in the hemoglobin monitored throughout and after the procedure.
Follow-up chest CT-PE protocol demonstrated decreased clot burden in the
RA and PA without visualization of right heart strain (Figure 6a, b).
Subsequent TTE reported no definite RA thrombus. Walking oxygen
assessment showed resting Sp02 of 96% and walking Sp02 100% on room
air. Four days later after the procedure, the patient was discharged on
long term Apixaban.
Discussion
RiHT are classified as type A Thrombi, those serpiginous, highly mobile,
and with high mortality. Type B Thrombi are less mobile, pedunculated,
broad base, and have better prognosis. And type C is an intermediate in
all characteristics. (7). The association of free floating-right heart
thrombi and massive pulmonary embolism (PE) has an incidence of 4-18%
(1). It is a life-threatening condition that requires emergent diagnosis
and treatment with reported fatal outcomes up to 21% in 14 days (8).
Thrombi that are adherent to the RA or right ventricle (RV) wall usually
have a more benign prognosis (8). However, free-floating, “snake-like”
thrombi are uncommon and usually associated with massive unstable
pulmonary embolism (9, 10). Some studies have reported the clot in
transit as a predictor of poor outcome (11). There are no evidence-based
guidelines for treatment of pulmonary embolism complicated by
free-floating RH thrombus (12).
In a retrospective analysis of 177 cases of right heart thromboembolism
and pulmonary embolism in 98% of the cases, the mortality rate
associated with no therapy, anticoagulation therapy, surgical
embolectomy, and thrombolysis was 100.0%, 28.6%, 23.8%, and 11.3%,
respectively (13). One year later the European Cooperative Study
reported a mortality rate of 60% for anticoagulated patients; 40% for
those treated with thrombolytics; and 27% for those submitted to
surgical procedures, which suggested the surgical approach to be the
most effective (8). Although, some small case series of RiHT type A
showed thrombolytic therapy with a favorable outcome in relation to
mortality (7), some controversy has arisen with systemic thrombolysis in
the treatment of giant right atrial thrombosis and clot fragmentation,
with subsequent fatal results related to the development of cardiogenic
shock (14). Until 2017, there was no studies that clearly determined
which patients with PE and RiHT would benefit from reperfusion treatment
(15). With this purpose, the Registro Informatizado de la Enfermedad
Trombo Embolica (RIETE) Registry compared the outcome during the first
month after treatment of standard anticoagulation therapy (heparin)
against reperfusion treatment (including thrombolysis or cardiac
surgery). The study did not show differences in survival among patients
who received standard anticoagulation compared with the reperfusion
therapy (15). They concluded that reperfusion therapies might be
reserved for patients who have acute symptomatic pulmonary embolism,
associated hypotension, or shock irrespective of the presence or absence
of coexisting RiHT (15).
Few reports of percutaneous treatment of free-floating thrombus in the
right atrium and PE has been published, and their results have been
promising. In these cases, several types of catheters were used in which
they also included direct AngioVac and IVC filters, or a Cook
intravascular retrieval. (16, 17, 18, 19).
FlowTriever System, an FDA approved device for treatment of PE, allows
it to be maneuvered into the pulmonary segmental branches and to
aspirate central and more distal pulmonary clot. It permits the use of
contrast injections through a coaxial system which enables us to monitor
the progress of the intervention. In the multicenter single-arm FLARE
(FlowTriever Pulmonary Embolectomy Clinical Study), presented in 2018 on
106 patients with intermediate-risk PE who underwent catheter
embolectomy using the FlowTriever catheter, they found the system safe
and effective. There was a significant improvement in RV/LV ratio and
minimal major bleeding. Potential advantages included immediate thrombus
removal, absence of thrombolytic complications, and reduced need for
post-procedural critical care (20).
This report highlights the effectiveness of FlowTriver for mechanical
thrombectomy of RiHT and PE in this case. Limitations described for
AngioJet or AngioVac as dysrhythmias, or difficult maneuverability were
not found (6). Additionally, its use showed a rapid normalization of PA
pressure and Sp02. This method allowed removal of the clot in a high
risk patient who exhibited contraindications to thrombolysis. Indigo
CAT (Penumbra) device has been evolving to larger diameters which can be
manipulated at a more segmental level and it is a very useful
alternative for pulmonary embolism however, the use on Right, has not
been reported.