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 cm². Mean gradients <10 mm Hg and ≥10 mm Hg were considered low gradient and high gradient, respectively. Similarly, stroke volume index <35 mL/m² was considered low flow (LF) and ≥35 mL/m² 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.