pulmonary disorders
Pulmonary Embolism (PE)
Rapid Reduction of Clot Burden
Clot elimination by means of embolectomy or dissolution with IV or catheter-based thrombolytic therapy should be considered for acute pulmonary embolism associated with hypotension that does not resolve after fluid resuscitation (high-risk/massive PE). Patients who are hypotensive and require vasopressor therapy are obvious candidates. Patients with a systolic blood pressure < 90 mm Hg or a decrease from baseline value in systolic blood pressure > 40 mm Hg that lasts at least 15 minutes despite fluid challenge are hemodynamically compromised and are also candidates. Although only anticoagulation is generally recommended for patients with mild RV dysfunction (based on clinical, ECG, or echocardiographic findings), thrombolytic therapy or embolectomy may be needed when RV compromise and/or hypoxemia is severe even when hypotension is not present, particularly when deterioration is likely as suggested by an increase in heart rate or decrease in oxygen saturation or blood pressure. Systemic thrombolytic therapy withalteplase(tissueplasminogenactivator [tPA]) offers a noninvasive way to rapidly restore pulmonary blood flow, but long-term benefits do not clearly outweigh the risk of hemorrhage in some patients. Experts agree that systemic thrombolytic therapy should be given to patients with hemodynamic compromise if there are no contraindications, particularly when other means of rapidly reducing clot burden are not readily available. Although no prospective randomized trial of systemic thrombolytic therapy has shown improved survival in patients with intermediate-risk/submassive PE, some experts recommend thrombolytics, particularly when patients also have numerous or large clots; very severe RV dysfunction; marked tachycardia; significant hypoxemia; other concomitant findings such as residual clot in the leg, positive troponin values, and/or elevated BNP values; and there are no active contraindications to its administration. Others reserve thrombolytic therapy only for patients with high-risk (massive) PE. Absolute contraindicationsto thrombolytics include Prior hemorrhagic stroke Ischemic stroke within 1 year Active external or internal bleeding from any source Intracranial injury or surgery within 2 months Intracranial tumor Certain surgeries within the previous weeks Relative contraindicationsinclude Age > 75 years Recent surgery (≤ 10 days) Hemorrhagic diathesis (as in hepatic insufficiency) Pregnancy Recent punctures of large noncompressible veins (eg, subclavian vein) Recent femoral artery catheterization (eg, ≤ 10 days) Peptic ulcer disease or other conditions that increase the risk of bleeding Severe hypertension (systolic blood pressure > 180 mm Hg or diastolic blood pressure > 110 mm Hg) Head trauma from PE-induced syncope, even if brain CT is normal Except for concurrent intracerebral hemorrhage, thrombolytic therapy is sometimes given to patients with high-risk (massive) PE who have "absolute contraindications" to such therapy if, without intervention, death is otherwise anticipated. In patients with relative contraindications, the decision to give systemic thrombolytics depends on individual patient factors. In the United States,alteplase(tPA) is used for systemic thrombolysis. Streptokinase and urokinase are no longer used for acute PE. In the United States, when systemic thrombolytics are given,heparinis usually stopped after the initial loading dose. However, in Europe,heparinis often continued, and there is no clear determination as to which method is preferred. The bleeding risk should be considered. Bleeding, if it occurs, can be reversed with cryoprecipitate or fresh frozen plasma. Accessible vascular access sites that are bleeding can be compressed. The potential for bleeding after systemic thrombolysis has led to increased implementation of catheter-directed thrombolysis, because much lower doses of thrombolytic agents are used. Catheter-directed PE therapy (thrombolytics, embolectomy) uses catheter placement in the pulmonary arteries for disruption, removal, and/or lysis of clot. Indications for its use are evolving in patients who are high risk and those at intermediate high risk. In catheter-directed PE thrombolytic therapy, the pulmonary arteries are accessed via a typical pulmonary arteriography procedure, and thrombolytics are delivered directly to large proximal emboli via the catheter. The most widely studied technique uses high-frequency, low-power ultrasonography. Ultrasonography accelerates thrombolysis by disaggregating fibrin strands and increasing permeability of lytic drug into the clot. Studies to date are limited to mainly single-arm studies and registries. One randomized controlled trial, the ULTIMA study, demonstrated that the use of catheter-directed thrombolytics in patients with proximal clot and evidence of RV strain leads to an improved RV/LV ratio at 24 hours compared with anticoagulation alone ( Rapid reduction in clot burden references ). However, there was no difference between the groups in RV function, RV/LV ratio at 90 days, or 90-day mortality ( Mechanical disruption, or removal of the thrombus via suction embolectomy without thrombolysis, is becoming more widely used. Mechanisms of clot removal include direct aspiration or fragmentation with aspiration. Devices for this purpose differ by size of catheter and method of embolectomy. If the use of thrombolysis is contraindicated, catheter-directed suction embolectomy may be considered and, depending on local resources and expertise, tried before surgical embolectomy. Data on the use of suction embolectomy devices are limited to patients at intermediate high risk or high risk who participated in single-arm studies and registries ( Rapid reduction in clot burden references ). Randomized controlled trials to help determine appropriate use of these devices in patients with PE are ongoing. Surgical embolectomyis reserved for patients with PE who are hypotensive despite supportive measures (persistent systolic blood pressure≤90 mm Hg after fluid therapy and oxygen or if vasopressor therapy is required) or on the verge of cardiac or respiratory arrest. Surgical embolectomy can be considered if use of thrombolysis is contraindicated, although catheter-directed suction embolectomy may be tried first. As with catheter-based thrombosis/clot extraction, the decision to proceed with embolectomy and the choice of technique depend on local resources and expertise. Surgical embolectomy as a management strategy for acute PE is decreasing in frequency as catheter-based percutaneous techniques become more widely available. Extracorporeal membrane oxygenation (ECMO) has been used increasingly in catastrophic acute pulmonary embolism when thrombolysis is contraindicated or failed. ECMO may serve as a bridge to surgical embolectomy or catheter-directed therapy, or it may buy time for improvement with anticoagulation alone. 1.Kucher N, Boekstegers P, Müller OJ, et al. Randomized, controlled trial of ultrasound-assisted catheter-directed thrombolysis for acute intermediate-risk pulmonary embolism.Circulation2014;129(4):479-486. doi:10.1161/CIRCULATIONAHA.113.005544 2.Hountras P, Bull TM. Advanced therapies for pulmonary embolism.Curr Opin Pulm Med2020;26(5):397-405. doi:10.1097/MCP.0000000000000714 