Massive Air Embolus Treated with Rheolytic Thrombectomy

Rupture of atherosclerotic plaque leading to exposure of highly thrombogenic material to the blood pool with subsequent thrombus formation is the principal mechanism associated with acute coronary syndromes.^1,2 Percutaneous coronary intervention (PCI) with distal embolization of thrombus is associated with an increased incidence of death, myocardial infarction (MI), abrupt closure, and emergency coronary artery bypass graft surgery.^3–5 Various pharmacologic, mechanical, and barrier strategies have been studied to avoid the adverse consequences related to PCI on lesions with visible thrombus. Unfortunately, the optimal treatment of thrombus-containing lesions is not yet defined.

Pharmacological thrombolysis, prolonged anticoagulation, and distal protection devices have limitations related to efficacy, complication rates and extended hospitalization.^6–10 One mechanical therapy that has shown promise for this challenging subset of lesions is rheolytic thrombectomy with the AngioJet (Possis Medical, Inc., Minneapolis, Minnesota) catheter. The AngioJet device is a catheter-based method for thrombus removal in which high-velocity saline jets are used to create a localized low-pressure zone at the distal catheter tip (Bernoulli effect), resulting in the maceration and removal of thrombus through an exhaust lumen. The use of rheolytic thrombectomy has been studied in thrombus-containing native coronaries as well as saphenous vein graft (SVG) lesions.^11,12 We report a case of a massive air embolus that occurred after activation of an AngioJet catheter in a thrombus-laden right coronary artery (RCA). The AngioJet catheter was then utilized to effectively aspirate the air embolus with restoration of coronary blood flow.

Case Report. A 68-year-old female presented to an outside hospital with a 3-day history of intermittent chest pressure which became persistent over a 3-hour period. Echocardiography on admission revealed > 2 mm ST-segment elevation in leads II, III, aVF and V4–6, with ST-segment depression in leads V1–3. She was treated with 2 doses of reteplase (10 units intravenously), aspirin 325 mg and unfractionated heparin. Her chest pain resolved with > 50% reduction in ST-segment elevation. The patient was transferred to our institution for further management.

On hospital day 2, the patient developed worsening chest pressure along with hypotension (87/57), and was taken for emergent coronary angiography. Cardiac catheterization revealed a normal left main and minimal disease in the left circumflex and left anterior descending artery. There was a 70% stenosis in a dominant mid-RCA associated with a large thrombus extending into the right posterior lateral branch which was occluded (Figure 1A).

Due to the significant thrombus burden and potential risk of distal embolization, the decision was made to use the AngioJet device prior to balloon angioplasty and stent placement. After a temporary transvenous pacemaker was placed in the apex of the right ventricle, an 8 Fr Judkins right 4.0 guiding catheter was used to engage the RCA. It was noted that when the guide was coaxially engaged and deep-seated in the RCA, flow was occluded with lack of contrast reflux and dampening of pressure. Eptifibitide was started, and heparin was administered to an activated clotting time (ACT) of 268 seconds. A 300 cm x 0.014 inch Balanced Performance Stabilizer wire (Cordis Corp., Miami, Florida) was used to cross the lesion. After the 4 Fr XMI AngioJet catheter was prepared, it was advanced across the lesion in the vessel and activated during slow pullback. After a 10-second pullback, contrast injection revealed a massive amount of air in the RCA with TIMI 0 flow (Figure 1B).

The AngioJet catheter was quickly reinserted down the RCA and activated in an attempt to aspirate the large air embolism column. After this second run, no residual air was noted in the RCA with TIMI 2–3 flow (Figure 1C).

A 3.0 x18 mm Velocity stent (Cordis) was subsequently deployed to 12 atm. Multiple injections of intracoronary adenosine were administered, with resultant TIMI 2–3 flow (Figure 1D). Due to mild hypotension, an intra-aortic balloon pump (IABP) was inserted and low-dose dopamine started.

IABP support was continued for 24 hours, along with intravenous inotropic support. The patient was diuresed and started on a beta-blocker and an ACE-inhibitor. A postprocedure echocardiogram revealed an ejection fraction of 20–25%, with inferior wall hypokinesis, an akinetic apex and mild mitral regurgitation. Her discharge medications included aspirin, atenolol, captopril, clopidogrel, furosemide, fluvastatin and insulin. The patient was readmitted 3 months later with chest pain. Subsequent cardiac catheterization revealed her RCA stent to be patent with TIMI 3 flow, and her ejection fraction had improved to 40%.

Discussion. The incidence of air embolism during diagnostic cardiac catheterization and PCI is reported at a rate of 0.84% and 0.24%, respectively.¹³ Although there is no optimal technique to restore blood flow after blockage by air emboli, treatment options include manual aspiration or forcefully injecting saline, with auxiliary supportive measures like 100% oxygen or an IABP. To our knowledge, this is the first case report utilizing rheolytic thrombectomy for the treatment of air emboli.

The AngioJet rheolytic thrombectomy system is a catheterbased method for thrombus removal in which high-velocity saline jets create a localized low-pressure zone at the distal catheter tip, resulting in the maceration and removal of thrombus through an exhaust lumen. The Vein Graft AngioJet Study (VeGAS 1) pilot study demonstrated the safety and feasibility of AngioJet thrombectomy in native coronary arteries and SVGs in a registry of 87 lesions with angiographic evidence of thrombus.¹¹ The VeGAS 2 trial was a multicenter study that randomized patients to either AngioJet thrombectomy (n = 179) or intracoronary infusion of urokinase (n = 167) for coronary arteries or SVGs with angiographic evidence of thrombus.¹² Although there was no difference in the primary endpoint of major adverse cardiac events (MACE) at 30 days, the AngioJet catheter was associated with a higher procedural success rate, less in-hospital MI and greater freedom from MACE at 1 year. The only randomized trial assessing the AngioJet catheter in acute MI patients undergoing primary PCI demonstrated increased MACE and infarct size in the AngioJet arm.¹⁴ However, the possible benefit of rheolytic therapy in the subset of MI patients with a large thrombus burden could not be determined from this study.

Several complications have been reported with the AngioJet catheter. Bradycardia and heart block requiring temporary pacing are common, reported to occur in 20–26% of cases and likely due to the release of adenosine from hemolyzed red blood cells.^11,12 Other reported adverse events include non-Q-wave MI (10%), distal embolization (3%), perforation (especially in arteries 11,12 It is interesting to speculate as to the source of such a massive air embolism down the coronary artery in our patient. Although we cannot exclude the possibility of inadvertent injection of a large volume of air into the RCA, we did not observe air injection at any time during the procedure. All injections from the manifold were performed under fluoroscopy. An alternative possibility is that air was entrained from a partially open Tuohy-Borst valve during activation of the AngioJet catheter. Several times during the procedure, we noted significant dampening of our 8 Fr JR4 guiding catheter when it was coaxial to the vessel. Activation of the AngioJet while withdrawing the device may have caused the guide to become deeply engaged, potentially creating a vacuum and entraining air from the valve.

As the AngioJet creates a localized low-pressure zone at thedistal catheter tip, thrombus is rapidly evacuated through the effluent lumen in an isovolumic manner (fluid instilled = fluid and blood removed). In situations where an occlusive guide without side holes is engaged in the coronary artery, it is plausible that air may be entrained from the Tuohy-Borst valve (as a result of a “vacuum effect”) during activation of the AngioJet catheter. In other words, an exclusive communication between the coronary lumen and guiding catheter could be the source of air introduction into the coronary artery. To our knowledge, this is the first reported case of such a potential complication. Use of a guiding catheter that is nonocclusive or with side holes to ensure continuous blood flow from the central aorta may help avoid entrainment of air into the coronary artery during activation of the AngioJet thrombectomy catheter. In the event of such a complication, the AngioJet catheter can be implemented to aspirate coronary air emboli.

References

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