LETTERS TO THE EDITOR
Reply
Ann T. Tong, MD, FACC,
Raymond Roudaut, MD,
Mehmet Özkan, MD,
Alex Sagie, MD,
Maie S.A. Shahid, MD,
Sergio C. Pontes, Jr, MD,
Francesc Carreras, MD,
Steven E. Girard, MD, FACC,
Samir Arnaout, MD,
Raymond F. Stainback, MD, FACC,
Ravi Thadani, MD, MPH,
William A. Zoghbi, MD, FACC* on behalf of the PRO–TEE Registry Investigators
* Baylor College of Medicine, 6550 Fannin, SM677, Houston, Texas 77030 (Email: wzoghbi{at}bcm.tmc.edu).
We appreciate Dr. Lengyel's interest in our PRO-TEE study regarding thrombolysis of prosthetic valve thrombosis (PVT) (1). In this international registry, thrombus burden was found to be the best predictor of complications in addition to a previous history of stroke. A thrombus area of 0.8 cm2 identified a threshold beyond which complications increased, irrespective of functional class. Thus, thrombolysis is safest in patients with thrombi  0.8 cm2 and no previous stroke. In patients with larger thrombi, recommendation of thrombolysis versus repeat surgery depends on the relative risk of each modality in a particular patient (1).
Dr. Lengyel proposes to use thrombolysis in all patients with PVT, irrespective of thrombus size and functional class. This is mostly based on a series of prosthetic valves reported by Lengyel and Vándor (2) where 43 cases underwent thrombolysis and 20 underwent surgery. Mortality rate was lower with thrombolysis (2 of 43 or 5% vs. 6 of 20 or 30%). However, patients were selected to undergo surgery as opposed to thrombolysis if they had a left atrial thrombus, if they presented with a stroke, or if they failed thrombolysis. This selection most likely contributed to the higher mortality rate of the small surgical group and to the lower mortality of the thrombolysis group. Furthermore, it is difficult to negate the relation of thrombus burden to complications of thrombolysis in that study because thrombus length was measured in only 3 of the 30 cases of obstructed valves. In the "nonobstructed" valves, the majority of which were in New York Heart Association functional class I and II, the thrombus length was generally small. Thrombus area was not measured. We disagree with the statement that thrombus burden cannot be measured with transesophageal echocardiography (TEE) when the valve is obstructed. Indeed, this was feasible in the PRO-TEE study where we found that thrombus area was a better discriminator than thrombus length in predicting complications. Whether three-dimensional echocardiography during TEE further refines the quantitation of thrombus burden and the risk of thrombolysis remains to be determined.
Dr. Lengyel also relates that recent experience with thrombolysis (1996 to 2003) shows a lower incidence of embolic phenomena (4%) and death rate (2.5%) compared to earlier experience. These complication rates are quite low compared to most reported series, including Dr. Lengyel's (1–3). While the exact reasons for this difference may not be readily apparent, imaging with TEE prior to management decision and avoidance of patients at high risk with large thrombi are likely contributing factors. In fact, in PRO-TEE, the use of thrombolysis irrespective of thrombus size in some centers provided a wide range of thrombus burden and allowed the evaluation of the relation of thrombus size to complications. The complication rate observed in PRO-TEE (embolic rate: 14%; death rate: 5.6%) was similar to reported series not using TEE to guide therapy, pointing to less selection bias.
Thus, we maintain that TEE is essential in the management of patients with suspected PVT. The PRO-TEE registry, although retrospective, identified for the first time the threshold of a "small clot" beyond which risk of complications increases with thrombolysis. Thrombolysis has the least complications with thrombi 0.8 cm2 and no previous stroke. In these patients, thrombolysis in our opinion should be a first-line therapy, regardless of functional class, unless contraindications are present. With larger thrombi, risk of complications appears to be incremental. Although thrombolysis is not an absolute contraindication in patients with larger thrombi, the choice of thrombolysis versus repeat surgery in these patients depends on the relative risk of each modality in a particular patient and institution. These recommendations await further validation in a prospective multicenter trial.
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References
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1. Tong AT, Roudaut R, Özkan M, et al. the Prosthetic Valve Thrombolysis-Role of Transesophageal Echocardiography (PRO-TEE) registry investigators Transesophageal echocardiography improves risk assessment of thrombolysis of prosthetic valve thrombosis: results of the international PRO-TEE registry J Am Coll Cardiol 2004;43:77-84.[Abstract/Free Full Text]
2. Lengyel M, Vándor L. The role of thrombolysis in the management of left-sided prosthetic valve thrombosis: a study of 85 cases diagnosed by transesophageal echocardiography J Heart Valve Dis 2001;10:636-649.[Web of Science][Medline]
3. Roudaut R, Lafitte S, Roudaut MF, et al. Fibrinolysis of mechanical prosthetic valve thrombosis: a single-center study of 127 cases J Am Coll Cardiol 2003;41:659-660.[Free Full Text]
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