Ultrasound-Assisted Thrombolysis Effective in Higher-Risk Pulmonary Embolism

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Fixed low-dose, ultrasound-assisted, catheter-directed thrombolysis rapidly reverses hemodynamic impairment in patients with higher-risk pulmonary embolism, according to a study published online December 13, 2013, ahead of print in the European Heart Journal.

Nils Kucher, MD, of University Hospital Bern (Bern, Switzerland), and colleagues assessed the efficacy and safety of the strategy in 52 patients with high-risk (n = 14) or intermediate-risk (n = 38) pulmonary embolism treated at their institution between April 2010 and January 2013.

Ultrasound-assisted thrombolysis was performed using an endovascular device (EkoSonic Endovascular System EKOS, Bothell, WA) that uses high-frequency, low-power ultrasound to increase thrombus permeability and thrombolytic penetration. Simultaneously, the ultrasonic pressure waves force the thrombolytic agent (recombinant t-PA) deep into the pulmonary thrombus.

Hemodynamic Improvement

Mean treatment duration was 15.6 ± 2.7 hours in high-risk patients and 15.4 ± 1.2 hours in intermediate-risk patients (P = 0.12). Systolic, diastolic, and mean arterial blood pressure measurements were lower before and after ultrasound-assisted thrombolysis in high-risk patients compared with intermediate-risk patients (P < 0.01 for both time points), while mean heart rate did not differ between the 2 groups before and after treatment.

Mean pulmonary artery pressure decreased and cardiac index increased at 15 hours. Furthermore, echocardiographic right-to-left ventricular end diastolic dimension ratio (RV/LV) decreased at 24 hours (table 1).

Table 1. Hemodynamic and Echocardiographic Parameters

The mean decrease in pulmonary artery pressure was greater in patients with high-risk compared with intermediate-risk pulmonary embolism (-16 vs. -10 mmHg; P = 0.042). The presence of high-risk pulmonary embolism was the only predictor of improved pulmonary artery pressure. The increase in cardiac index, meanwhile, was similar in patients with high- and intermediate-risk pulmonary embolism (42% and 33% increase, respectively; P = 0.54). Patients with acute onset of symptoms (< 14 days) showed a trend toward a greater increase in mean cardiac index than patients with subacute or acute-on-chronic presentation (P = 0.054), but a similar decrease in mean pulmonary artery pressure (P = 0.23) after ultrasound-assisted thrombolysis.

Major nonfatal bleeding occurred in 2 patients (3.8%) and consisted of 1 intrathoracic bleed after CPR requiring transfusion and 1 intrapulmonary bleed requiring lobectomy. Additionally, 2 deaths occurred during hospitalization: 1 from cardiogenic shock and 1 from recurrent pulmonary embolism. No deaths occurred during follow-up, resulting in a 3-month mortality rate of 3.8%.

Alternative Needed

Currently no standardized local thrombolysis regimen exists for the treatment of pulmonary embolism, the study authors note, adding that there is “a great need for alternative revascularization strategies that are safer than systemic thrombolysis.” The rate of major bleeding complications after systemic thrombolysis has been reported to be as high as 20%, Dr. Kucher and colleagues write.

As to the greater hemodynamic improvement in patients with a symptom duration of less than14 days, they note that the study did not allow for assessment of the effect of symptom duration or delay in the initiation of treatment on hemodynamic parameters. Furthermore, the dose and duration of recombinant t-PA was arbitrary, they add.

More studies are needed to further define the role of ultrasound-assisted thrombolysis compared with anticoagulation alone and other revascularization strategies in the management of pulmonary embolism patients at increased risk, the authors conclude.

Study Details

Patients’ mean age was 65 ± 14 years. Catheters were inserted bilaterally in the majority of both high- and intermediate-risk patients. All received an IV bolus (80 units/kg) of unfractionated heparin at initial presentation. The catheter-delivered t-PA dose was 20 mg over 15 hours. Mean duration of stay in the intensive care or intermediate care unit was 3.7 ± 3.1days, with no difference between high-risk and intermediate-risk patients (P = 0.54).

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