CardioExchange Archive

CardioExchange’s John Ryan interviews Mehmet Özkan — lead author of a study, published in Circulation, of low-dose, slow-infusion t-PA in pregnant women with prosthetic valve thrombosis — and Patricia Casais, the lead author of the official editorial on the study.

THE STUDY

Twenty-four consecutive women who had 25 pregnancies and experienced 28 episodes of prosthetic valve thrombosis (PVT; 15 obstructive, 13 non-obstructive) received low-dose (25-mg) tissue plasminogen activator (t-PA) over the course of 6 hours. Thrombolytic therapy, under transesophageal echocardiography guidance, yielded complete thrombus lysis for all 28 PVT episodes. One patient had placental hemorrhage with preterm live birth at week 30, and one patient experienced minor bleeding. 

THE INTERVIEW

Ryan: Should these findings change clinical practice? 

Ozkan: Yes, we certainly think that our findings will change practice, and we suggest that thrombolysis should be used as first-line therapy for pregnant patients with mechanical valve thrombosis, especially in the U.S., where these patients usually end up undergoing surgery. We strongly encourage using our thrombolytic therapy protocol for such women, as we discussed in detail in our study. This may call for a change in guideline recommendations.

Casais: I think there is not yet enough evidence to recommend it as the therapy of choice. This paper is very promising, especially because it showed that thrombolytics are safe for the mother and the baby. In my opinion, the evaluation of its efficacy is more complicated, and given that it is closely related to the anticoagulant therapy after the thrombolysis, it might be difficult to assess. So what we mean by “successful thrombolysis” — and how and when to evaluate it — should be carefully defined (especially for a registry).

Ryan: If people start doing this, should we have some sort of international registry to track the experience?

Ozkan: Yes, we must have an international registry to track the experience with these patients. The cases are infrequent, and they receive variable treatments. It is virtually impossible for a single center to conduct a randomized study of these cases. The best treatment for these patients could be determined in international registry studies.

Casais: Definitely — an international registry is the most efficient way to get the information we need. Once we have that knowledge, we can assess whether this approach should change practice and become the therapy of choice for valve thrombosis in pregnancy. In addition, it would help to identify factors associated with good and poor outcomes.

Ryan: What kind of consent is necessary to provide this treatment?

Ozkan: To provide this treatment to a pregnant patient, we must obtain detailed thrombolytic therapy consent, including the risks to the mother and fetus. The consent form describing the risks to the mother could be the usual thrombolysis consent form for adults. However, the consent form describing the risks to the fetus should include short-term risks, such as fetal loss, and currently unknown long-term risks. Both parents need to give that consent.

Casais: The informed consent would need to state these points:

a. No standard therapy for valve thrombosis in pregnancy exists.

b. The approaches that might solve this complication are optimizing anticoagulant therapy, thrombolysis, and surgery — but each one of them has potential serious adverse outcomes (these should be specified). Not all of the approaches will be suitable for all patients.

c. Slow infusion of low-dose t-PA has been shown to be safe and efficacious in a series of patients, but more information is needed to identify the patients who would benefit the most from this treatment.

d. Prosthetic valve thrombosis is an infrequent complication, so it is difficult to evaluate which treatment is best in terms of safety and efficacy. An international registry would provide the data we need. Information in the registry must be confidential, of course, and meet other basic requirements.

JOIN THE DISCUSSION

Do you think thrombolytic therapy, as tested in this study, is ready for prime time? How do the new findings change your thinking?