A contemporary approach to thrombolytic therapy for pulmonary embolism

Fibrinolysis for acute pulmonary embolism

Acute pulmonary embolism (PE) presents as a constellation of clinical syndromes with a variety of prognostic implications. Patients with acute PE who have normal systemic arterial blood pressure and no evidence of right ventricular (RV) dysfunction have an excellent prognosis with therapeutic anticoagulation alone. Normotensive acute PE patients with evidence of RV dysfunction are categorized as having submassive PE and comprise a population at intermediate risk for adverse events and early mortality. Patients with massive PE present with syncope, systemic arterial hypotension, cardiogenic shock, or cardiac arrest and have the highest risk for short-term mortality and adverse events. The majority of deaths from acute PE are due to RV pressure overload and subsequent RV failure. The goal of fibrinolysis in acute PE is to rapidly reduce RV afterload and avert impending hemodynamic collapse and death. Although generally considered to be a life-saving intervention in massive PE, fibrinolysis remains controversial for submassive PE. Successful administration of fibrinolytic therapy requires weighing benefit versus risk. Major bleeding, in particular intracranial hemorrhage, is the most feared complication of fibrinolysis. Alternatives to fibrinolysis for acute PE, including surgical embolectomy, catheter-assisted embolectomy, and inferior vena cava (IVC) filter insertion, should be considered when contraindications exist or when patients have failed to respond to an initial trial of fibrinolytic therapy. Patients with massive and submassive PE may be best served by rapid triage to specialized centers with experience in the administration of fibrinolytic therapy and the capacity to offer alternative advanced therapies such as surgical and catheter-assisted embolectomy.

Predictors of major hemorrhage following fibrinolysis for acute pulmonary embolism

One hundred four patients at Brigham and Women's Hospital who received alteplase for acute pulmonary embolism were evaluated. Major bleeding occurred in 20 patients (19.2%). The principal site of bleeding was unknown in 9 (45.0%), gastrointestinal in 6 (30.0%), retroperitoneal in 3 (15.0%), intracranial in 1 (5.0%), and splenic in 1 (5.0%). Independent predictors of major hemorrhage were the administration of catecholamines for systemic arterial hypotension (odds ratio [OR] 115, 95% confidence interval [CI] 9.4 to 1,410.9, p < 0.001), cancer (OR 16.0, 95% CI 3.2 to 80, p = 0.004), diabetes mellitus (OR 9.6, 95% CI 1.7 to 54, p = 0.010), and elevated international normalized ratio before fibrinolysis (OR 5.8, 95% CI 1.5 to 22, p = 0.012).

Monitoring manufacturing process yields, purity and stability of structural variants of PEGylated staphylokinase mutant SY161 by quantitative reverse-phase chromatography

Staphylokinase variant SY161 is a recombinant mutant of the Staphylococcus aureus polypeptide staphylokinase (Sak), and is currently in human clinical trials as a thrombolytic agent. The 15 kDa single chain SY161 protein is expressed as a soluble cytoplasmic product in E. coli with a single cysteine inserted near the N-terminus. The protein as extracted from E. coli is a mixture of both monomeric and intermolecularly disulfide crosslinked species. To improve protein purification yields SY161 is sulfitolyzed during the early stages of production, preventing disulfide formation. The protein is later modified during manufacturing to incorporate a single 5 kDa polyethylene glycol group on the single sulfhydryl sidechain. We have developed and qualified a reverse-phase chromatographic method to quantitate SY161 during product manufacturing. We discuss the use of the assay during manufacturing development to monitor fermentation yields, the SY161 PEGylation reaction, and as an in-process manufacturing control assay. The assay has been applied as a product purity and identity release assay and is suitable for use in assessing product structural integrity during stability testing. The assay has a linear range of quantitation for SY161 from at least 0.15 to 16 micro g, and is-in addition capable of detecting and quantitating protein de-PEGylation events and host cell-derived protein contaminants.

Major bleeding complications in cardiopulmonary resuscitation: the place of thrombolytic therapy in cardiac arrest due to massive pulmonary embolism

OBJECTIVE

Thrombolytic therapy in patients with massive pulmonary embolism (MPE) and prolonged cardiopulmonary resuscitation (CPR) is subject to debate. This study was performed to determine whether (1) thrombolytic treatment increases the risk of bleeding complications, (2) if the risk of bleeding is influenced by the duration of CPR and if (3) thrombolytic therapy improves outcome.

DESIGN

Retrospective cohort study.

SETTING

Emergency department of a tertiary care university hospital.

PATIENTS AND METHODS

Sixty-six patients with cardiac arrest (CA) due to MPE admitted between July 1993 and December 2001. Thirty-six patients received thrombolysis (TL) and were compared with 30 patients without thrombolytic therapy. Bleeding complications were assessed by clinical evidence or autopsy.

RESULTS

Major bleeding complications appear to occur more frequently in patients treated with thrombolytics (9/36 (25%) vs. 3/30 (10%)) even though the difference was statistically not significant (P=0.15). It appears that CPR duration >10 min has no adverse impact on major bleeding complications. No difference in the rate of major bleeding complications between thrombolyzed patients who had a CPR duration of </=10 or >10 min could be observed (2/8 (25%) vs. 7/28 (25%), P=0.99). In thrombolyzed patients a return of spontaneous circulation could be achieved more frequently (24/36 (67%) vs.13/30 (43%) in controls, P=0.06) and survival after 24 h was higher (19/36 (53%) vs. 7/30 (23%), P=0.01). Survival to discharge was also higher in the TL group (7/36 (19%) vs. 2/30 (7%)), but not statistically significant (P=0.15).

CONCLUSION

Although severe bleeding complications tend to occur more frequently in patients undergoing TL, the benefit of this treatment might outweigh the risk of bleeding.

Venous thromboembolism guidebook

This venous thromboembolism guidebook incorporates evolving contemporary concepts in diagnosis and management of pulmonary embolism (PE) and deep venous thrombosis (DVT) into a user-friendly menu. The purpose of this document is to provide a literature-based review of the current clinical approach to venous thromboembolism and up-to-date references for further study in this important topic.

High dose and short-term streptokinase infusion in patients with pulmonary embolism: prospective with seven-year follow-up trial

BACKGROUND

High dose and short-term streptokinase infusion has proved to improve survival among few patients with pulmonary embolism and cardiogenic shock, without increasing hemorrhagic complications. However its efficacy and safety in terms of long follow-up and in major number of patients requires to be established.

METHODS

Patients with pulmonary embolism proved through high probability V/Q lung scan, suggestive echocardiogram, or deep venous thrombosis were enrolled. All were assigned to receive 1,500,000 IU in one-hour streptokinase infusion. The primary end point was efficacy and safety of streptokinase regimen in terms of pulmonary arterial hypertension, right ventricular dysfunction, perfusion abnormalities, recurrence, mortality and hemorrhagic complications. In long-term follow-up, we assessed functional class, recurrence, chronic pulmonary arterial hypertension, postthrombotic-syndrome and mortality.

RESULTS

A total of 40 consecutive patients (47.3+/-15.3 years of age) with large or massive pulmonary embolism were enrolled. In 35 patients high dose and short-term streptokinase regimen reversed acute pulmonary arterial hypertension, clinical and echocardiographic evidence of right ventricular dysfunction and improved pulmonary perfusion without increasing hemorrhagic complications. In acute phase 5 patients died, necropsy study performed in 4 patients showed massive pulmonary embolism and right ventricular myocardial infarction, without significant coronary arterial obstruction. Risk factors for mortality and recurrence were: right ventricular global hypokinesis (p<0.0001), 6 hours or over between onset symptoms and streptokinase regimen (p=0.02), severe systolic pulmonary arterial hypertension (p=0.001) right ventricular hypokinesis (p=0.001), hypoxemia (p=0.02) and right ventricular acute myocardial infarction (p<0.0001). Right ventricular hypokinesis (p=0.02) was the only independent risk factor for recurrence. In a seven-year follow-up of the original 35 patients who survived in acute phase, 2 patients were lost and 33 are alive, in functional class I, without recurrence or chronic pulmonary arterial hypertension.

CONCLUSIONS

Our report indicates that among properly selected high-risk PE patients, short-term streptokinase infusion is effective and safe.

Unsolved issues in the treatment of pulmonary embolism

The three most controversial and unsolved issues in the treatment of pulmonary embolism (PE) are: (1) the role of thrombolysis, (2) the role of low molecular weight heparin and length of hospital stay, and (3) the optimal duration of anticoagulation. The trend is to use thrombolysis more frequently, to administer low molecular weight heparin and shorten the hospitalization duration in low-risk patients, and to give prolonged courses of anticoagulation with warfarin. PE thrombolysis appears most beneficial in patients at high risk of adverse clinical outcomes in whom the potential hazards of bleeding can be justified by the danger of conservative management with anticoagulation alone. With respect to utilizing low molecular weight heparin as a way of shortening the duration of hospitalization, there are no data to warrant this approach. The current FDA mandate for symptomatic PE patients is to administer intravenous unfractionated heparin administered as a bridge to therapeutic warfarin. Finally, the optimal duration of anticoagulation following acute PE remains mired in controversy. Despite the high rate of recurrent venous thrombosis after discontinuation of anticoagulation, there are currently insufficient data to recommend indefinite warfarin therapy.