Thrombosis Risk in Patients With Mitral Paravalvular Leak: A New Phenomenon in Mechanical Prosthetic Valves

Mitral regurgitation modifies left atrial (LA) hemodynamics, potentially reducing thrombus formation through the "washout effect." However, the role of paravalvular leaks (PVLs) in thrombus formation remains unclear. In this study we examined the development of thrombosis in patients with mild-moderate and severe mitral PVL.

This single-centre retrospective study included 357 patients with mechanical mitral valves with mild-moderate and severe PVL. The primary outcome was the presence of thrombus at the edge of the PVL jet, detected using transesophageal echocardiography. Forty-three patients had thrombus at the edge of the regurgitant jet on the LA side. Echocardiographic, clinical, and biochemical data were analyzed.

Patients were categorized into severe (n = 247) and mild to moderate (n = 110) PVL groups (mean age, 59.7 ± 10.54 years). Severe PVL was associated with lower low-density lipoprotein cholesterol and hemoglobin, as well as higher C-reactive protein and lactate dehydrogenase levels (P < 0.001). Echocardiographic findings included larger defect size and higher gradients in severe PVL cases (P < 0.001). Thrombus at the PVL jet edge was more frequent in the severe PVL group (16.1% vs 2.7%; P < 0.001). Spontaneous echo contrast in the LA appendage was more common in patients with mild-moderate PVL (39.1% vs 25.9%; P = 0.026). LA spontaneous echo contrast was significantly present (7.2%) in the mild-moderate group but absent in the severe PVL group (P < 0.001). LA wall thrombus was absent in patients with severe PVL.

Despite severe mitral regurgitation, localized stasis at the PVL jet edge might promote thrombus formation on the prosthetic valves. This highlights a distinct mechanism that warrants further investigation for tailored management.