Prosthetic heart valves are arguably one of the most crucial devices in keeping a patient suffering from cardio-illness alive. But these devices, which improve blood flow function, aren't without fault. In fact many run into problems after implementation and need to be evaluated.

For years now, cardiologists and surgeons have worked on criteria to review these devices to search for potential problems once they are inserted in a patient. The issue has always been coming to a consensus on how best to accomplish this task.

But a panel of international experts has developed a group of guidelines that have been endorsed by five major health organizations including the American Heart Association (Dallas) American College of Cardiology (Washington) European Association of Echocardiography (France) Japanese Society of Echocardiography (Osaka, Japan) and the Canadian Society of Echocardiography (Alberta, Canada).

The American Society of Echocardiography (Morrisville, North Carolina) also helped compile the report "Recommendations for Evaluation of Prosthetic Valves with Echocardiography and Doppler Ultrasound". A full version of the document will be available at www.asecho.org on Sept. 9.

One of the key points of the document is that echocardiography with doppler is the method of choice for the noninvasive evaluation of prosthetic valve function.

"These guidelines give us a more uniform way of looking at prosthetic valves," William Zoghbi, MD, of Methodist DeBakey Heart and Vascular Center (Houston) and a lead author of the article told Medical Device Daily. "Over the last 40 years, a large variety of prosthetic valves have been developed with the aim of improving blood flow function, increasing durability and reducing complications. Nevertheless, there is no ideal valve and all prosthetic valves are prone to dysfunction. The guidelines are critical to handling the evaluation of prosthetic valves and emphasize the importance of echocardiography."

The guidelines evaluate the following in the valve:

• The peak velocity and gradient of the valve;

• Mean pressure gradient;

• Velocity-time integral of the jet;

• Doppler velocity index when observing the valve.

"I think one of the problems that we saw was cardiologists not knowing when to call the artificial valve obstructive or not," Zoghbi said.

The term "obstructive heart defects" refers to an abnormality in the large vessels around the heart or in the heart valves that prevents blood from flowing freely. An obstructive heart defect creates high pressures in the heart and makes the heart work harder to pump the blood. The patient may be asymptomatic, but over time, a narrowed (stenotic) heart valve may become more thickened and result in increasing obstruction.

Another recommendation tells surgeons and cardiologist to be mindful of the size, height and body weight of the prosthetic valve in relation to the date of valve placement and its design. Additionally, imaging of the valve from multiple views is recommended with particular attention to motion leaflets or occluder, presence of calcification on the leaflets or abnormal echo densities on the various components of the prosthesis, along with valve sewing ring integrity and motion.

Zoghbi also said the guidelines offer considerations for the intraoperative patient, other techniques for assessing replacement heart valves and considerations for early vs. late complications of prosthetic valves.

"I think what this gives us finally is consensus. It offers us a more uniform way of looking at how we check the condition of prosthetic valves," Zoghbi told MDD. "Although physical examination can alert the clinician to the presence of significant prosthetic valve dysfunction, diagnostic methods are often needed to assess the function of the prosthesis."

To date more than 60,000 patients per year undergo heart valve replacement in the U.S. Replacement of diseased valves reduces the morbidity and mortality associated with native valvular disease but comes at the expense of risking complications unique to the implanted prosthetic device. Also more than 80 models of artificial valves have been introduced since 1950. Only a few prosthetic valves are either created from synthetic material (mechanical prosthesis) or fashioned from biological tissue (bioprosthesis).

Omar Ford, 404-262-5546;
omar.ford@ahcmedia.com