From the Journals

Time to rethink bioprosthetic valve guidelines?

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Calling out the clot

Dr. Egbe and colleagues make a “provocative” case that it is the presence of thrombus on bioprosthetic valves, and not degeneration, that causes valve dysfunction, Clifford W. Barlow, MBBCh, DPhil, FRCS, of University Hospital Southampton (England) said in his invited commentary (J Thorac Cardiovasc Surg. 2016;152:978-80).

“This Expert Opinion is of particular interest because it relates to something commonly performed: conventional valve replacement,” Dr. Barlow said. Moreover, “BPVT is an under-recognized problem for which Dr. Egbe and colleagues concisely direct how future research should ascertain which diagnostic, preventive, and treatment strategies would improve long-term outcomes and avoid redo surgery.”

Dr. Egbe’s and colleagues’ recommendation of prolonged anticoagulation after bioprosthetic valve implantation complicates the selection of bioprosthetic valves – because cardiovascular surgeons frequently choose them to avoid anticoagulation, while accepting a higher risk of a reoperation because of valve degeneration, Dr. Barlow said.

And while Dr. Barlow noted this study found that porcine valves are not a predictor for BPVT, another Mayo Clinic study reported eight cases of BPVT, all in porcine valves (J Thorac Cardiovasc Surg. 2012;144:108-11). Nonetheless, the expert opinion by Dr. Egbe and colleagues is “relevant to much that is important – not only to improving outcomes with conventional valve replacement but also to these developing technologies,” Dr. Barlow said.



Recent findings on the incidence and pathophysiology of bioprosthetic valve thrombosis require revisiting existing guidelines against routine echocardiography in the first 5 years after bioprosthetic valve replacement and a longer course of anticoagulation therapy than the current standard of 3 months, investigators from the Mayo Clinic said in an expert opinion article in the October issue of the Journal of Thoracic and Cardiovascular Surgery (2016;152;975-8).

“The occurrence of BPVT is not restricted to surgically implanted bioprosthetic valves, but has also been observed after transcatheter aortic valve replacement (TAVR),” Dr. Egbe and colleagues said. They noted an association between BPVT and a lack of anticoagulation therapy in two earlier reports (N Engl J Med. 2015;373:2015-24; J Am Coll Cardiol. 2016;67:644-55). In their own study, 14 of 15 patients (93%) with diagnosed BPVT responded to anticoagulation therapy and avoided reoperation.

Dr. Egbe and coauthors did somewhat define the extent of the problem of misdiagnosis of BPVT. The diagnosis was considered in only 6 of 45 patients (13%) who had transesophageal echocardiography. “A significant proportion of the patients with BPVT were misdiagnosed as having structural failure and referred for reoperation,” Dr. Egbe and coauthors said. “This attests to the low level of awareness of the existence of BPVT and the lack of well-defined diagnostic criteria.”

They proposed a diagnostic model based on the echocardiography characteristics of three findings: a 50% increase in gradient within 5 years of implantation; increased cusp thickness; and abnormal cusp mobility. “The presence of all three echocardiographic features reliably diagnosed BPVT with a sensitivity of 72% and a specificity of 90%,” they said.

Their finding that 85% of BPVT cases occurred within 5 years of implantation flies in the face of clinical guidelines that state routine annual echocardiography is not recommended in that time frame (J Am So Echocardiogr. 2009;22;975-1014). But abnormal physical examination findings as a prerequisite for echocardiography may not be an effective method to diagnose BPVT. “In addition to transthoracic and transesophageal echocardiography, the use of other complementary imaging modalities, such as computed tomography, could be very effective in identifying subtle BPVT,” Dr. Egbe and colleagues said,

But preventing BPVT is more complicated. Clinical guidelines recommend anticoagulation of bioprosthetic valves for 3 months after implantation, but adhering to that guideline showed no protective effect against BPVT in their study, Dr. Egbe and coauthors said. Nor did antiplatelet therapy prove effective in preventing BPVT. However, a Danish study showed stopping anticoagulation within 6 months of surgical aortic valve replacement increased risk of thromboembolic complications and cardiovascular death (JAMA. 2012;308:2118-25). And the role of prosthesis type in BPVT “remains unclear.”

Dr. Egbe and coauthors acknowledged a number of questions persist with regard to BPVT in bioprosthetic valve dysfunction, including the true incidence, best screening method, risk factors, and the duration of anticoagulation, as well as the role of novel oral anticoagulants. “Answers to these questions will come from population-based prospective studies,” Dr. Egbe and colleagues said.

Dr. Egbe and his coauthors had no relationships to disclose.

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