Severe isolated mitral stenosis: are we facing different phenotypes?

Funding Acknowledgements

Type of funding sources: None.

Introduction

Rheumatic mitral valve stenosis (MS) causes progressive left atrial (LA) fibrosis and functional impairment, pulmonary artery systolic hypertension and right ventricular (RV) dysfunction.

Purpose

The aim of the study was the evaluate the different characteristics between high gradients (HG) and low gradient (LG) MS and, within the LG group those with high (LG-HF) or low flow (LG-LF). Moreover, we wanted to evaluate if there was any difference in overall complications and atrial fibrillation (AF) incidence.

Methods

A total of 147 patients with isolated severe MS were retrospectively enrolled from the institutional echo database.  Echocardiograms were read offline and clinical information were obtained from patients` records. Patients were divided into a group with HG (31 patients, mean MS gradient > 10 mmHg) and LG (116 patients, mean MS gradient ≤ 10 mmHg). The group of LG was then divided in low flow (Stroke volume index (SVi) ≤ 35 ml/m2, LF-LG: 68 patients) and in high flow (SVi > 35 ml/m2, HF-LG: 48 patients).

Results

The HG group was younger, although the difference did not reach statistical significance, higher percent of males (45% M vs 22% F, p = 0.02), higher heart rate (HR), left atrial volume, higher tricuspid regurgitation velocity (TVR) and derived pulmonary artery systolic pressure (PASP), RV fractional area changes (RV FAC) but similar RV longitudinal contraction. Moreover, the HG group had more severe MS calculated according to PHT.  The group of LG was divided according to SVi:  LF-LG group compare to HG-MS had higher percent of females (45% F vs 13% M, p < 0.001), similar AF (43% vs 32%, p = ns) and pre surgical complications (19% vs 16%, p = ns). LF-LG group had smaller LA systolic volume (117 ± 51 51 ml vs 148.6 ± 38 ml, p < 0.0001), lower LV-S` (5.3 ± 1.4 vs 6 ± 1.6 cm/s, p = 0.004), lower TRV (2.47 ± 0.5 vs 3.24 ± 0.7 m/s, p < 0.0001), higher TAPSE/PASP (0.64 ± 0.3  vs 0.45 ± 0.29, p < 0.001), lower RV S` (9.79 ± 2.01m/s vs 11.25 ± 3.1 m/s, p = 0.01), higher RVFAC (38.5 ± 9.6% vs 30.9 ± 9.2%, p = 0.0005). The group of LG-LF had also less severe MS (1.3 ± 0.6 cm2 vs 1.15 ± 0.3 cm2, p < 0.01).

Conclusion

Patients with HG MS were those with worst left ventricular involvement, higher PASP and lower RV function. The LF-LG MS were older, and more females were included and even though they had smaller LA, lower values of PASP they had significantly higher percent of AF and similar pre surgical complications.  It could be speculated that LF-LG severe MS patients could be a different phenotype of the disease.