Clinical Characteristics, Hemodynamic Profile, and Outcomes in Patients With Low‐Gradient and High‐Gradient Severe Mitral Stenosis: Influence of Flow Status

Background In severe mitral stenosis (MS), flow‐status was recently recognized as potentially impactful in some patients with low transmitral gradients. Methods We studied 172 patients with isolated rheumatic MS with mitral valve area ≤1.5 cm 2 . Mean gradients <10 mm Hg and ≥10 mm Hg were considered low gradient and high gradient, respectively. Similarly, stroke volume index <35 mL/m 2 was considered low flow (LF) and ≥35 mL/m 2 was considered normal flow (NF). We compared clinical and echocardiographic characteristics including noninvasively determined net atrioventricular compliance, effective arterial elastance, end‐systolic elastance, right ventricular function, and a composite outcome of all‐cause mortality, heart failure hospitalization, mitral valve intervention, and stroke or transient ischemic attack. Results Forty‐three (25.0%) patients had NF low‐gradient MS, 60 (34.9%) had LF low‐gradient MS, 26 (15.1%) had NF high‐gradient MS, and 43 (25.0%) had LF high‐gradient MS. Patients with LF status were more symptomatic ( P =0.008) and had lower atrioventricular compliance (LF 4.37±1.52 mL/mm Hg; NF 5.44±1.50 mL/mm Hg; P <0.001). Despite lower left ventricular ejection fraction (LF 51.9±12.1%; NF 61.0±5.3%; P <0.001), they had similar end‐systolic elastance ( P =0.106) with increased arterial elastance (LF 2.64±0.80 mm Hg/mL; NF 1.70±0.44 mm Hg/mL; P <0.001), and more right ventricular dysfunction (LF 79.6%; NF 36.2%; P <0.001). Subdividing patients with low flow into LF low‐gradient and LF high‐gradient subgroups showed similar findings, suggesting that LF status, rather than transmitral gradient, was linked to these findings. LF status was associated with poorer event‐free survival (LF, 5.46 years [95% CI, 4.05–6.87]; NF, 7.44 years [95% CI, 6.17–8.72]; P =0.001) whereas there was no association between mean gradient and outcomes ( P =0.284). Conclusions Patients with LF severe MS demonstrated a characteristic pattern of echocardiographic abnormalities and poorer outcomes regardless of transmitral gradients.