When Problems Arise With Prosthetic Heart Valves, Multimodality Imaging Is Needed, Say European Guidelines

Echocardiography should be the first tool used to evaluate potential dysfunction of a prosthetic heart valve, but other imaging modalities may be needed to get a clearer picture of the problem and the best way to manage it, according to new European guidelines.

 “The contribution of multimodality imaging is even more important in this subset of patients with prosthetic valves because the etiologies are more diverse and more complex than in native valves,” Philippe Pibarot, DVM, PhD (Québec Heart and Lung Institute and Laval University, Quebec, Canada), one of the guideline authors, told TCTMD. A high gradient across a native valve generally means there is stenosis, he said, but a high gradient across a prosthetic valve could be due to valve dysfunction or patient-prosthesis mismatch.

Imaging beyond transthoracic echo (TTE) is not always needed but if there is any suspicion of dysfunction, the threshold to use transesophageal echo (TEE) or another non-echocardiographic imaging modality “should be relatively low, because those prosthetic valve complications could be catastrophic if you don’t detect them in time,” said Pibarot.

Cinefluoroscopy, multidetector CT, cardiac MRI, and—to a lesser extent—nuclear imaging all have complementary roles to play, according to the guidance from the European Association of Cardiovascular Imaging, a branch of the European Society of Cardiology. The lead author is Patrizio Lancellotti, MD (University of Liège Hospital, Belgium).

The document, which was published online May 3, 2016, ahead of print in the European Heart Journal – Cardiovascular Imaging, covers heart-valve replacements with mechanical prostheses and bioprostheses. Transcatheter valves are not discussed because they will be the subject of separate guidelines expected sometime this year, Pibarot said. He noted, however, there will be substantial overlap in terms of basic principles, concepts, methods, and relevant parameters.

William Zoghbi, MD (Houston Methodist DeBakey Heart & Vascular Center, Houston, TX), who chaired the writing group that drafted 2009 guidelines on using echo to evaluate prosthetic valves, said the new guidance is comprehensive. “It addresses most of the situations that clinicians would be faced with and the echocardiographer would be faced with,” he told TCTMD.

In addition to expanding the scope to include non-echo modalities, he said, the document emphasizes some of the known limitations of echo, particularly when used in the aortic position for mechanical prostheses.

Homing in on the Problem

Although relatively rare, valve dysfunction does occur with prosthetic valves in the forms of structural valve deterioration or nonstructural problems not related to the valve itself, including dehiscence or entrapment of the occluder by pannus, tissue, or suture. Thrombus is the most common cause of obstruction for mechanical prostheses and less frequently affects bioprosthetic valves.

It is crucial to determine the exact cause of the problem to be able to determine the best way to address it, the authors say. These new guidelines, which include descriptions of valve types and the function and characteristics of each, provide detailed descriptions as to how the various imaging modalities can be used to do just that.

The authors recommend 2D TTE for first-line imaging of prosthetic heart valves and for routine follow-up, but note that both TTE and TEE are needed for a complete evaluation of a patient with suspected dysfunction. Additional information about thrombus formation, pannus, and prosthetic valve dehiscence can be gleaned from 3D TEE.

Although not employed for routine evaluation of prosthetic heart valves, Pibarot said modalities other than echo can be useful for the following situations:

• Cinefluoroscopy for evaluating disc mobility of mechanical valves
• Cardiac CT for visualization of calcification and degeneration of bioprostheses, pannus formation, and presence of thrombus and assessment of the movement of occluders and discs in mechanical valves
• Cardiac MRI for the assessment of valve function and regurgitation

Nuclear imaging currently has limited utility, but it has been used in cases of suspected infective endocarditis, Pibarot said.

An important feature of the guidelines, he said, are a series of tables providing parameters, criteria, and algorithms that can be used to help clinicians identify obstruction and regurgitation, particularly involving the aortic and mitral valves. It is in these areas where the recommendations diverge somewhat from the earlier 2009 document.

New parameters have been introduced and additional weight has been placed on others based on the findings of more recent studies. Previously, for example, Doppler velocity index was the main parameter examined when evaluating valve stenosis, whereas the current guidelines place more of an emphasis on valve morphology and mobility and changes in Doppler echo parameters during follow-up, said Pibarot.

But an important message, “is that both for stenosis and regurgitation, it’s extremely important to use a multiparameter, integrative approach,” he added. “There is not one single parameter that is perfect. . . . If you rely on one parameter, you’re going to have misdiagnosis.”

Reduced Leaflet Motion and Subclinical Valve Thrombosis

One area that does not get much coverage in the guidelines is the problem of reduced leaflet motion and subclinical valve thrombosis, an issue that came to light late last year in a publication in the New England Journal of Medicine.

Pibarot said those data were released when the current guidelines were already nearly finalized and, thus, could not be included. There probably would have been more discussion of that issue included if the data had been reported earlier, he said.

The current guidelines do, however, mention that CT could be useful for assessing valve thickening and subclinical thrombosis, he pointed out.

But he added that more recent data suggest that the prevalence of reduced leaflet motion reported in the NEJM paper was high and discordant with what is seen clinically. So perhaps CT is too sensitive, Pibarot said, and might be better used as a screening tool that can be used to trigger additional evaluations with TEE. Then if the TEE provides abnormal results, anticoagulation can be considered, he said.

Related Stories:

• New Findings on Bioprosthetic Valve Thrombosis Have Implications for Surveillance, Research
• Reduced Leaflet Motion in Bioprosthetic Aortic Valves Not Uncommon But Remedied by Anticoagulation