What are the important artificial heart valve emergencies?

What are the important artificial heart valve emergencies?

While most of the natural heart valve emergencies are due leaks, artificial heart valve emergencies can be due to leaks or narrowing. Most common artificial heart valve emergency is due to clot formation in a mechanical heart valve. This can cause narrowing of the valve orifice, leakage of the valve, or both. Clot formation in an artificial heart valve is most likely during the first three months after the surgery for implantation of the valve. This is the period during which the valve gets covered with body’s own cells, after which risk of clot formation is lesser. Clot formation can be minimized to a large extent by meticulous management of the dosing of medications used to prevent clot formation.

Persons with clot formation in the artificial heart valve can have severe breathlessness due to collection of fluid in the lungs, a fall in blood pressure or paralysis due to migration of blood clots to the brain. Though very small clots can be treated by adjusting the dose of medications to prevent clot formation and medications which can dissolve the clots, most may need surgery. Moreover clot dissolving treatment also carries the risk of the dissolved clot fragments migrating to vital structures like the brain. This could lead to a massive fatal stroke. In case of mechanical heart valves, the risk of clot formation is present lifelong and hence medications to prevent clot formation are needed lifelong.

Clot formation in an artificial heart valve can be documented by echocardiography (ultrasound imaging of the heart), live X-ray imaging for valve movements (fluoroscopy) and computed tomography (CT). CT may be useful in differentiating clots from growth of cells into the valve. Obstruction to the valve increases the pressure gradient across it, which can be documented by a special ultrasound technique known as Doppler echocardiogram.

Sudden leaks in the artificial heart valves can occur due to failure of the stiches used to retain the valves and following infections of the valve. A rocking movement of an unstable artificial valve may be noted on live X-ray imaging (fluoroscopy). If the person is having fever, infection of the artificial heart valve has to be suspected.

Echocardiogram may show evidence of the infection, though it is often difficult to see in mechanical heart valves. Blood culture test which grows the infecting organism in an artificial external medium is useful in identifying the organism as well as in guiding appropriate medical treatment. Occasionally  positron emission tomography (PET) may be needed in a case of suspected artificial heart valve infection when the echocardiogram is not contributory. PET scan will show increased uptake of the radioactive tracer in the region of the infected valve.

Leak in an artificial heart valve can also be due to a stuck valve. A clot between the artificial valve leaflet and the cage can cause a stuck valve. In a stuck valve, the leaflets are fixed in a partially open position, producing severe leak. This can be identified by echocardiography and fluoroscopy if the leaflets are radio opaque. Sometimes the valve leaflets are made of non-radio opaque material and are not visible on fluoroscopy.

Other rare causes of leaks in artificial heart valves are strut fracture with leaflet escape and perforation of the artificial valve leaflets. These occur due to degradation of the material used for manufacturing the artificial valve. Fluoroscopy and CT scan may be useful in identifying these complications which may not be evident on echocardiography.

In case of bioprosthetic (biological) valves, both leaks and narrowing can be due to degeneration of the valve in the long run. Degeneration is more likely in younger individuals because of higher blood flow velocities. That is why bioprosthetic valves are considered more often in older persons and mechanical valves in younger individuals.