Fibrinolysis For Mechanical Prosthetic Valve Thrombosis
Abstracts & Commentary
Synopsis: Although fibrinolytic therapy was highly successful for thrombosis of prosthetic mechanical heart valves, a high complication rate limits its use to nonsurgical candidates.
Sources: Roudaut R, et al. J Am Coll Cardiol. 2003;41: 653-658; Alpert JS. J Am Coll Cardiol. 2003;41:659-660.
The current role of fibrinolysis therapy for mechanical prosthetic valve thrombosis remains controversial. Thus, investigators from Pessac, France, and San Diego, Calif, retrospectively reviewed their experience with 127 episodes of prosthetic valve thrombosis in 110 patients treated with fibrinolytic agents between 1978 and 2001. They noted that the use of fibrinolytic agents has decreased over the past decade, possibly because the increased use of transesophageal echocardiography has increased the accuracy of the diagnosis and has increased the number of patients excluded because of large atrial clots. Bileaflet mitral valves were most frequently affected, and 91% of all thrombosed valves were obstructed. Almost half were documented to be on inadequate anticoagulation. About 20% of cases were heralded by systemic emboli, but most presented with symptoms of heart failure. Approximately one-third of the patients initially received 1 of 3 agents: streptokinase, urokinase, or recombinant tissue plasminogen activator (rt PA), followed by heparin. Therapy was continued until echocardiography or cinefluoroscopy became normal. Complete success was noted in 71%; seventeen percent experienced marked clinical improvement, but incomplete recovery of valve function; and in 12%, therapy failed. Success rates were higher for aortic vs mitral prostheses. One-third of patients required the use of 2 fibrinolytic agents. As a first agent either streptokinase or rt PA were superior to urokinase, and after combination therapy those given streptokinase first had considerably more success—86% vs 68% for rt PA first and 59% for urokinase first (P = .045). In one-quarter of patients complications were observed: major bleeding in 5%, systemic embolism in 15%, and death in 12%. The mortality was higher in patients with more severe heart failure. About 20% of patients required surgery for incomplete results. Roudaut and colleagues concluded that although fibrinolytic therapy was highly successful for thrombosis of prosthetic mechanical heart valves, a high complication rate limits its use to nonsurgical candidates.
Comment by Michael H. Crawford, MD
The results of this observational data base study suggest that fibrinolytic therapy for thrombosed mechanical prosthetic valves is still controversial. The major competing therapy is surgical thrombectomy or valve replacement. Results from observational surgical reports suggest that the overall mortality is similar (10-20%) and higher (up to 50%) in critically ill patients. However, the rate of systemic emboli is much higher with fibrinolytic therapy. Thus, it would appear that the risk of emboli may be acceptable in critically ill patients at high risk for surgery but not in stable patients at lower risk for surgery. This conclusion is supported in the accompanying editorial by Alpert.
Several caveats are discussed by Roudaut et al. The success of fibrinolysis was higher in aortic prostheses vs mitral, which could influence decisions in difficult cases. Also, without presenting any data, they suggest that fibrinolysis should be first choice in right heart prosthetic valves, presumably because the sequelae of emboli to the lungs is less important clinically. Although Alpert agrees with this recommendation, it would have been nice to see some supportive data. In addition, Roudaut et al make much of the great value of transesophageal echocardiography in the last decade. In particular, they point to the elimination of patients for fibrinolytic therapy with large atrial clots, presumably because they are hard to dissolve and the risk for emboli may be higher. Although this makes some sense, and no one would question the overall value of this new endocardiographic technology, no supportive data are presented. Finally, Roudaut et al point to an almost 20% recurrence rate over a mean of 2 years as another reason to favor surgery. However, since the majority of prosthetic valve thromboses are caused by inadequate anticoagulation, it is not clear how surgery solves this problem. Some patients may have structural problems with the valve (pannus, etc) that could predispose to recurrent thrombus. It may be better to try to identify such patients by transesophageal echo before surgical referral.
Dr. Crawford is Professor of Medicine, Mayo Medical School; Consultant in Cardiovascular Diseases, and Director of Research, Mayo Clinic, Scottsdale, AZ.
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