APCU25CR13 Eccentric mitral regurgitation jet in posterior leaflet prolapse mimicking moderate MR: a diagnostic pitfall myxomatous mitral valve with tangential jet a rare occurance

Background Mitral valve prolapse (MVP) is the leading cause of primary mitral regurgitation (MR). Accurate assessment of MR severity is essential for appropriate management and surgical timing. However, eccentric MR jets remain a well-recognized diagnostic challenge. Reliance on color Doppler jet area alone may underestimate severity due to the Coand&noentity259; effect, particularly when jets are tangential or wall-hugging. Case reports play an important role in highlighting such diagnostic pitfalls with direct implications for clinical decision-making.Case Presentation A 54-year-old man, active smoker with hypertension and dyslipidemia, presented with non-ST elevation myocardial infarction (NSTEMI, TIMI 3) and ventricular bigeminy secondary to hypokalemia. He had a significant family history of sudden cardiac death. Symptoms resolved following standard medical therapy and electrolyte correction.Transthoracic echocardiography (TTE) demonstrated posterior mitral leaflet prolapse with a highly eccentric anteriorly directed jet hugging the left atrial wall. Initial color Doppler evaluation suggested moderate MR. However, multiparametric assessment incorporating vena contracta width, regurgitant volume, and the absence of chamber remodeling—confirmed only mild MR in the context of a myxomatous mitral valve.Discussion This case highlights a classic diagnostic pitfall where posterior mitral valve leaflet (PMVL) prolapse produces an anterior eccentric MR jet. The Coand&noentity259; effect causes the jet to adhere to the atrial wall, leading to dispersion and apparent reduction in jet area on TTE. In addition, aneurysmal changes of the PMVL may alter jet direction and obscure the regurgitant orifice, further complicating severity assessment. Transesophageal echocardiography (TEE) and multiparametric evaluation including vena contracta, proximal isovelocity surface area (PISA), and pulmonary vein flow are essential when there is discordance between clinical presentation and TTE findings. Accurate grading of MR is critical, as underestimation may delay surgical referral and worsen prognosis, while overestimation may lead to unnecessary intervention.Conclusion Eccentric MR jets from posterior leaflet prolapse can mimic moderate MR if assessment relies solely on jet area. A multiparametric echocardiographic approach is vital to avoid misclassification. TEE should be pursued in cases of diagnostic uncertainty. Early recognition of this pitfall ensures accurate grading, appropriate management, and optimal long-term outcomes in patients with MVP.