By Jeffrey Zimmet, MD, PhD
Associate Professor of Medicine, University of California, San Francisco; Director, Cardiac Catheterization Laboratory San Francisco VA Medical Center
Dr. Zimmet reports no financial relationships relevant to this field of study.
SOURCES: Leetmaa T, et al. Early aortic transcatheter heart valve thrombosis: Diagnostic value of contrast-enhanced multidetector computed tomography. Circ Cardiovasc Interv 2015;8:e001596.
Latib A, et al. Treatment and clinical outcomes of transcatheter heart valve thrombosis. Circ Cardiovasc Interv 2015;8:e001779.
Several years ago, before we began performing transcatheter aortic valve replacement (TAVR) at our own institution, one of my patients came for a 1-month follow-up visit after having TAVR elsewhere. We were alarmed to discover that his transvalvular gradients had quadrupled since his procedure. Ultimately, we hit upon case reports of early transcatheter aortic valve thrombosis, and began systemic anticoagulation. Now, two new reports in shed new light on this phenomenon.
In the study by Leetmaa et al, a series of 140 patients receiving the Edwards Sapien valve at a single center underwent multidetector CT 1-3 months after TAVR. Valve thrombosis was identified in five patients, which was 4% of the sample. Four of the five patients were asymptomatic, and in these patients echocardiography showed no structural abnormality and no abnormal gradients. Three of the five had ejection fractions below 35%, and two did not receive the standard post-TAVR dual antiplatelet therapy. No structural issues (underexpansion, non-circularity) were noted with the valves in the affected patients.
Latib et al looked at retrospective data from 4266 patients undergoing transcatheter aortic valve replacement at 12 centers between 2008 and 2013. Thrombosis events were defined as: 1) valve dysfunction secondary to thrombosis diagnosed based on response to anticoagulation therapy or imaging, or 2) mobile mass detected on the valve suspicious for thrombus in the absence of infection, irrespective of dysfunction. By these criteria, 26 (0.61%) valve thromboses were reported, of which 20 came from the Edwards Sapien/Sapien XT cohort and six from the Medtronic CoreValve cohort. Seventeen patients (65%) presented with exertional dyspnea, while eight (31%) had no specific symptoms. Only one of the patients had discontinued the recommended antiplatelet regimen.
Echocardiography demonstrated increased transvalvular gradients in the majority (92% had mean gradients > 20 mm Hg), with an average mean gradient of 40.5 mmHg. Thickened leaflets or thrombotic apposition of leaflets was seen by echo in 77% of cases, while only six (23%) showed a thrombotic mass. None of the identified patients had stroke or other evidence of thromboembolic phenomena. Of the 26 identified patients, 23 were treated with systemic anticoagulation. This resulted in a significant decrease of the trans-valve gradient or disappearance of the thrombotic mass in all 23 patients.
The authors concluded the following:
- Valve thrombosis occurred in 0.61% of TAVR patients in this registry. Patients most often presented with dyspnea and increased transvalvular gradient.
- All thrombosis cases occurred within 2 years from transcatheter aortic valve implantation and were not associated with discontinuation of antiplatelet therapy.
- Thrombosis should be suspected in cases of premature valve dysfunction, even if a thrombotic mass is not clearly detected.
- Anticoagulation resulted in restoration of normal valve function within 2 months of treatment, and should be considered the treatment of choice when transcatheter valve thrombosis is suspected.
With TAVR now making its way into the mainstream of treatment options for patients with severe aortic stenosis, we are seeing increasing numbers of patients who have undergone this procedure in all settings, and, therefore, we need to be aware of less-common complications. The CT study demonstrates that valve thrombosis may be more common than earlier thought, although the meaning of asymptomatic thrombus formation without valve dysfunction is far from clear. There are no data to guide us when presented with evidence of an asymptomatic thrombosis. While CT may be more sensitive than echo for detection of such issues, CT is not indicated as a routine screening tool post-TAVR.
On the other hand, the registry study highlights only the subset of valve thrombosis events that came to clinical attention, and here the advice is more clear. Dual antiplatelet therapy, although recommended as a standard therapy, is not fully effective at preventing this outcome. Transcatheter valve thrombosis should be considered in all cases of transcatheter valve dysfunction and should be treated with anticoagulation — in most cases with vitamin K antagonists. Echocardiography will usually show increased gradients, but may not reveal any structural abnormality. Advice from experienced valve centers should be sought in equivocal cases.