What are the important prosthetic valve emergencies?

What are the important prosthetic valve emergencies?

While most of the native valve emergencies are due regurgitations, prosthetic valve emergencies can be due to regurgitations or stenosis. Most common prosthetic valve emergency is due to prosthetic valve thrombosis in a mechanical prosthetic valve. This can cause acute stenosis, regurgitation or both. Prosthetic valve thrombosis and thromboembolism are most likely during the first three months after the surgery for implantation of the valve. This is the period during which the valve gets endothelialized, after which risk of thrombosis is lesser. Thrombotic complications can be minimized to a large extent by meticulous anticoagulation management.

Patients with prosthetic valve thrombosis may present with acute dyspnea due to pulmonary edema, cardiogenic shock or neurological deficits due to embolic episodes. Though cases with very small thrombi may respond to anticoagulation optimization and intravenous thrombolysis, most will need surgery. Moreover, thrombolysis also carries the risk of massive thromboembolism which could result in a major stroke which may even end up fatally. In case of mechanical valve, the risk of thrombosis is present lifelong. Prosthetic valve thrombosis can be documented by echocardiography, fluoroscopy for valve movements and computed tomography (CT) [1]. CT may be useful in differentiating pannus from thrombus in a chronic case. Pannus is tissue ingrowth into the prosthetic valve and has higher density than thrombus. It can also elevate the transprosthetic valve gradient on Doppler echocardiography.

Acute prosthetic valve related regurgitation can be due to suture failure or dehiscence following infective endocarditis. An unstable prosthetic valve can show an abnormal rocking movement on fluoroscopy. This produces paravalvular regurgitation, which can be progressive. Regurgitation in endocarditis of bioprosthetic valve can also be valvular. Infective endocarditis can be suspected if the person is febrile. Though difficult due to acoustic shadowing, vegetations may be seen on the prosthetic valves. Blood culture will identify the organism in prosthetic valve endocarditis and guide antibiotic therapy. Positron emission tomography (PET) is an important investigation in a case of suspected infective endocarditis when the echocardiogram is not contributory. PET scan will show increased uptake in the region of the valve in infective endocarditis.

Regurgitation in prosthetic valve can also be due to a stuck valve. A thrombus between the prosthetic 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 regurgitation. 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 prosthetic valve regurgitation are strut fracture with leaflet escape [2] and perforation of the prosthetic valve leaflets. These occur due to degradation of the material used for manufacturing the prosthetic valve. Fluoroscopy and CT scan may be useful in identifying these complications which may not be evident on echocardiography.

In case of bioprosthetic valves, both regurgitation and stenosis can be due to degeneration of the valve in the long run. Degeneration is more likely in younger individuals because of higher hemodynamic stress. That is why bioprosthetic valves are considered more often in older persons and mechanical valves in younger individuals. A rare case of bioprosthetic valve regurgitation due to valve perforation resulting from the use of an automated suture technique has also been reported [3].

References

1. Dangas GD, Weitz JI, Giustino G, Makkar R, Mehran R. Prosthetic Heart Valve Thrombosis. J Am Coll Cardiol. 2016 Dec 20;68(24):2670-2689. doi: 10.1016/j.jacc.2016.09.958. PMID: 27978952.
2. Uchino G, Yoshida H, Sakoda N, Hattori S, Kawabata T, Saiki M, Fujita Y, Yunoki K, Hisamochi K, Mine Y. Outlet strut fracture and leaflet escape of Bjork-Shiley convexo-concave valve. Gen Thorac Cardiovasc Surg. 2017 Jun;65(6):358-360. doi: 10.1007/s11748-016-0667-7. Epub 2016 Jun 3. PMID: 27259859.
3. Arunachalam K, Potakamuri L, Sortino A, Gopalakrishnan P, Anreddy S. A Rare Etiology for Bioprosthetic Aortic Valve Regurgitation. CASE (Phila). 2020 Jul 23;4(5):452-457. doi: 10.1016/j.case.2020.06.008. PMID: 33117948; PMCID: PMC7581638.