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J Thorac Cardiovasc Surg 2008;135:691-693
© 2008 The American Association for Thoracic Surgery
Brief Communication |
a Department of Medicine, Division of Cardiology, Stanford University, Stanford, Calif
b Department of Cardiothoracic Surgery, Stanford University, Stanford, Calif
c Sections of Cardiology, VA Palo Alto HCS, Palo Alto, Calif
d Cardiothoracic Surgery, VA Palo Alto HCS, Palo Alto, Calif
Received for publication September 13, 2007; accepted for publication November 15, 2007. * Address for reprints: John Giacomini, MD, Cardiovascular Medicine, Stanford University School of Medicine, 300 Pasteur Dr, Falk CVRB, Stanford, CA 94305. (Email: giacominijohn{at}yahoo.com).
Although valve thrombosis is infrequent, patients with prosthetic valves have a lifelong risk of this complication. Because operative mortality can be significant, thrombolysis has emerged as an alternative therapy for high-risk surgical patients.1-3
Recent reports have included the use of tissue-type plasminogen activator because of the unavailability of other agents4,5; however, the application of thrombolysis may be limited by increased risks of thrombus dislodgment, distal embolization,1 and hemorrhagic complications.3
Rapid infusion of thrombolytic agents has also been associated with higher complication rates.4,5 By determining the lowest effective infusion dosage, the infusion rate and duration can be set to minimize risks of thromboembolism and hemorrhage. To our knowledge, there are no data on the lowest effective dosing regimen for specific patient subsets. It is likely that patients who are hemodynamically unstable require rapid lysis, and current recommended protocols3 are indicated. For patients who are hemodynamically stable, however, a slower rate of infusion may be warranted. We present a case of prosthetic valve thrombosis successfully treated with a low-dose regimen of recombinant tissue-type plasminogen activator (rtPA, 1 mg/h without bolus), such as is typically used for peripheral artery bypass graft occlusions. Such an approach for treatment of prosthetic valve thrombosis has not been reported previously.
A 55-year-old woman with a mechanical aortic valve prosthesis (St Jude 19 mm; St Jude Medical Inc, Minneapolis, Minn) was seen for two days of exertional chest pain associated with nausea and diaphoresis. Two weeks before her admission, without seeking medical advice, the patient discontinued her warfarin sodium therapy. Physical examination revealed normal vital signs. Results of cardiopulmonary examination were unremarkable except for muffled aortic prosthetic valve sounds. Electrocardiography revealed normal sinus rhythm and left ventricular hypertrophy with strain.
Transthoracic echocardiography suggested restricted motion of aortic prosthetic leaflets, with turbulent flow on color flow Doppler scan. Continuous-wave Doppler echocardiography confirmed severe obstruction, with peak and mean gradients of 158 mm Hg and 86 mm Hg, respectively (
Figure 1, A). There was mild aortic insufficiency. No obvious thrombus was seen. The left ventricle was normal in size, with normal systolic function and normal wall thickness. Fluoroscopy revealed decreased excursion of both aortic prosthetic leaflets (
Figure 2, A;
Video 1). The patient was admitted to the coronary care unit. Because of the patient's relative hemodynamic stability and the risk of reoperation, a trial of thrombolysis was elected. Both streptokinase and urokinase were unavailable at our institution and other nearby hospitals. We therefore chose a regimen of rtPA to achieve gradual lysis at the lowest effective dose and thus minimize thromboembolic and hemorrhagic complications. A regimen designed for lysis of peripheral artery bypass graft occlusions was initiated. Specifically, a continuous intravenous infusion of rtPA (1 mg/mL) was begun at a rate of 1 mg/h. A bolus was not given. A fixed-dose heparin infusion of 300 units/h (3 u/[kg · h]) was initiated.
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After her initial presentation for prosthetic valve thrombosis, the patient was admitted for psychiatric evaluations on two separate occasions, which occurred 4 and 11 months later. Echocardiography at that time revealed normal prosthetic valve function. The mean gradients on echocardiograms performed during these admissions were 23 and 26 mm Hg, respectively (Figure 1, C). Unfortunately, the patient died shortly thereafter from complications related to diabetes.
Although this experience is limited to a single case, a low-dose rt-PA regimen with longer infusion duration is a promising approach for patients who are in hemodynamically stable condition and do not require rapid lysis. There may be a lower complication rate because of the significantly lower infusion rate, despite longer infusion duration. Patients should be monitored closely for adequate lysis. This includes daily echocardiography and laboratory evaluations (D-dimer, activated partial thromboplastin time, and fibrinogen). Fluoroscopy should be used to confirm leaflet motion. Further investigation is necessary to evaluate the short- and long-term efficacy and safety of this treatment strategy.
Supplementary data
Supplementary data associated with this article can be found in the online version, at doi:10.1016/j.jtcvs.2007.11.012
References
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  F. M. Caceres-Loriga, H. Perez-Lopez, and K. Morlans-Hernandez Prosthetic valve thrombosis: a regimen of treatment with low-dose and longer-course using recombinant tissue-type plasminogen activator is a promising protocol. J. Thorac. Cardiovasc. Surg., October 1, 2008; 136(4): 1104 - 1105. [Full Text] [PDF]
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