A New Treatment for Severe Pulmonary Embolism
Percutaneous Rheolytic Thrombectomy
Background The rheolytic thrombectomy catheter has been specially designed to remove intravascular thrombus from coronary and peripheral arteries. It demonstrates a practical application of Bernoulli’s principle relating to a low-pressure zone in the region of a high-velocity jet. In this device, this effect is created by direct high-pressure saline jets located at the tip. Thrombus is drawn into this region and, because of the large pressure difference, undergoes mechanical thrombolysis due to the powerful mixing forces. The resulting microparticles are aspirated through the same catheter and removed from the body.
Methods and Results We report the use of this device in two patients presenting with severe pulmonary embolism and contraindications to thrombolytic therapy. The two procedures were successfully performed with an excellent immediate angiographic result at the site of the rheolytic thrombectomy. In both cases, the clinical improvement was maintained at follow-up with the same good angiographic result and a decrease to a normal level of the systolic pulmonary pressure.
Conclusions This preliminary results suggest that this easy technical method may be useful in the treatment of life-threatening pulmonary embolism in patients with absolute contraindications to thrombolytic therapy. A larger cohort of patients is necessary to determine whether this treatment should be proposed as an alternative to the use of fibrinolytics in selected patients.
The rheolytic thrombectomy catheter (RTC) device was designed to remove intravascular thrombus from coronary and peripheral arteries. The Angiojet thrombectomy catheter is a component of the Angiojet Thrombectomy System (Possis Medical Inc). This device and the principle of rheolytic thrombectomy have been previously described.1 Briefly, the 5F catheter shaft has a dual lumen: a high-pressure hypotube supplies pressurized sterile saline to the catheter tip while the other larger lumen is used for evacuation of thrombus debris and guide wire passage. The catheter delivers high-velocity jets of saline that carry away adjacent thrombus, pulling it into the catheter tip and breaking up the thrombus. The clot particles are propelled through the length of the exhaust lumen of the catheter. The fluid removed (a mixture of ≈50% saline and ≈50% blood/thrombotic debris) is pumped from the catheter to a collection bag, where the volume of fluid provides an estimate of blood loss. In theory, this method could be useful in situations in which intravascular thrombus is life threatening in patients who are at increased risk of bleeding complications with thrombolytic therapy, a scenario that commonly occurs in the setting of pulmonary embolism.
We report the first use of this device in two patients presenting with severe symptomatic pulmonary embolism and contraindications to thrombolytic therapy.
A 72-year-old man was initially admitted to another hospital 10 days earlier because of left hemiparesis associated with shortness of breath. He was transferred to our cardiology unit for further care. At admission, he reported recent bouts of dyspnea and near-syncope activity. Physical examination showed normal vital signs, no persisting neurological deficit, and normal cardiac and pulmonary auscultation. The ECG demonstrated atrial flutter with a slow ventricular response. The chest radiograph was normal. A cardioembolic cause of his stroke possibly related to his arrhythmia was suspected, and a transesophageal echocardiogram revealed a huge thrombus in the right inferior pulmonary artery. This was confirmed by pulmonary angiography (Fig 1A⇓) and was associated with systolic pulmonary hypertension (45 mm Hg). Because of the clinical and hemodynamic consequences of such a large pulmonary embolism, thrombolytic therapy was suggested for this patient; however, a subsequent computed tomography scan of the brain showed a hemorrhagic infarct, and thrombolytic therapy was thus contraindicated. We proposed to the patient the use of this new technique, which to our knowledge had not been previously reported for this indication. Right heart catheterization and pulmonary angiography were performed through an 8F sheath placed in the right femoral vein after angiographic confirmation of the absence of thrombi in the venous system. The patient was already receiving intravenous heparin, which was not interrupted. An 8F Judkins right coronary guiding catheter was positioned in the right pulmonary artery just proximal to the thrombus. This was used to support the 5F RTC. Multiple passes of this device into the thrombus were performed. During each pass, the probe was moved slowly over a duration of 30 seconds. The guiding catheter was used to redirect the probe in different directions in the pulmonary artery, and in different parts of the clots, through the use of fluoroscopic and angiographic guidance with hand injections of small amounts of contrast media. During the procedure, which lasted 30 minutes, the patient remained asymptomatic and hemodynamically stable. We collect 600 mL of blood/saline mixture. The immediate angiographic result was excellent: no additional clots were observed in the pulmonary tree (Fig 1B⇓). The pulmonary pressure remained unchanged.
The patient remained asymptomatic and was discharged 8 days later on Coumadin. On the systematic angiographic control 1 month later, the pulmonary tree remained totally free of thrombus (Fig 1C⇑) and the systolic pulmonary pressure had returned to normal (27 mm Hg).
This 74-year-old patient was admitted to the orthopedic department because of multiple trauma, including a fractured tibia, and he was immobilized with a cast. He had a history of ischemic heart disease, including coronary artery bypass graft surgery in 1984. Despite low-molecular-weight heparin treatment after immobilization, he suddenly developed chest pain in the right side and severe shortness of breath on day 9. His blood pressure was 110/70 mm Hg, and the heart rate was 80 bpm (on β-blockers). Cardiac examination showed signs of right ventricular failure with jugular venous distention. The ECG showed normal sinus rhythm, S1Q3 pattern, incomplete right bundle-branch block, and nonspecific repolarization changes. The chest radiograph showed an abnormally clear right lung and diffuse hypovascularity. He had severe hypoxemia (6,5 Kpa). Right heart catheterization revealed systolic pulmonary hypertension (51 mm Hg). Pulmonary angiography showed massive bilateral embolism resulting in the absence of flow to the right upper and middle lobes (Fig 2D⇓), as well as to the left lower lobe (Fig 2A⇓). As a result of the recent fracture, thrombolytic therapy was contraindicated, leading us to propose thrombectomy for this patient. We used the same technique described for patient 1. In patient 2, only the thrombus from the left inferior pulmonary artery was treated and successfully removed. Because the procedure time was considered to be long (30 min) and 600 mL of mixed saline/blood was retrieved, this procedure was interrupted to observe the clinical response despite thrombus remaining in the right pulmonary artery (Fig 2B⇓). The patient clinically improved after a 24-hour period and was subsequently discharged 8 days later on Coumadin.
At 1-month follow-up, the patient was in good condition, and we performed scintigraphic, hemodynamic, and angiographic studies. The systolic pulmonary pressure had returned to normal (21 mm Hg). Left pulmonary angiography and scintigraphy of the left lung were normal, showing no thrombus and no perfusion defect (Fig 2C⇑). Right pulmonary angiography showed persistence of the previously observed thrombus in the right lower pulmonary branch (Fig 2E⇑), with absence of flow in this area. Similar perfusion defect on scintigraphy was also noted.
Different percutaneous catheter-based methods of treating pulmonary thrombus have been previously described to overcome the contraindication of thrombolytics in patients with increased risk of bleeding complications; these include removing thrombus with an embolectomy device2 or mechanically breaking up or pulverizing the thrombus in situ.3 4 5 However, none of these methods are commonly used in clinical practice.
The RTC has been reported to remove thrombus from coronary arteries, saphenous vein grafts, peripheral arteries, dialysis fistulas, and a transjugular intrahepatic portosystemic stent shunt.6 7 8 To our knowledge, we report the first use of this device in human pulmonary arteries in patients with severe pulmonary embolism. The two procedures were easily and safely performed and were well tolerated by the patients. The angiographic and hemodynamic results, as well as clinical improvement, were significant.
Despite these very encouraging results, the results of our two patients do not allow us to answer several questions that might be raised about this new procedure. Due to the RCT design, the potential risk of perforation of a thin-walled pulmonary artery by the high-pressure saline jets should be minimal, and slow and careful advancement of the device should decrease the risk of mechanical perforation. The first case showed that a 10- to 15-day-old thrombus can be effectively extracted by the catheter, but the question of how old can a clot be before it no longer can be fragmented remains unanswered. Therefore, at the present time, the interest of assessing by angioscopy the fresh or organized nature of the thrombus is unknown. Our second case raises the concern of whether a spontaneous lysis could have led to the same outcome. In this patient with a bilateral embolism, only the thrombus of the left inferior pulmonary artery was removed because we were concerned about the amount of mixed blood/thrombus/saline solution in the collection bag (600 mL) after a 30-minute procedure. This case is of particular interest because the thrombosed right pulmonary artery was treated only with anticoagulants and thus served as a control. At the time of follow-up, the left pulmonary arteries were normal, whereas the right lower lobe pulmonary artery still contained obstructing thrombi. This suggests the efficacy of this technique and its advantage over anticoagulant therapy alone. Another device, using the principle of rheolytic thrombectomy (Hydrolyser-Cordis), is also under investigation,9 10 but concern has been raised about the ability of this device to clear thrombus from large vessels.8
This preliminary experience with RTC device suggests that this procedure is easy to use and may be useful in the treatment of life-threatening pulmonary embolism in patients with absolute contraindications to thrombolytic therapy. Further immediate and long-term evaluation in a larger cohort of patients is necessary to determine whether this mechanical treatment of severe pulmonary embolism could be useful as an alternative to fibrinolytics in selected patients.
The authors thank Richard Medeiros for his advice in editing of the manuscript.
- Received May 28, 1997.
- Revision received August 13, 1997.
- Accepted August 18, 1997.
- Copyright © 1997 by American Heart Association
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