Mitral TEER clips hold benefits at 1 year in patients with atrial SMR

An analysis of the EXPANDed patient-level pooled cohort presented at HFSA 2024 demonstrates clinical benefits in patients with atrial secondary mitral regurgitation (SMR) at 1 year following a mitral transcatheter edge-to-edge repair (TEER) procedure using newer-generation clip devices. These included a significant reduction in MR and substantial improvements in patient-reported outcomes.

From 3.8 percent of patients with atrial SMR having an MR grade ≤1+ per independent echocardiography core laboratory assessment at baseline, the proportion increased to 95.2 percent 1 year after TEER.

The improvement in functional capacity, as evidenced by a shift in New York Heart Association (NYHA) functional classes, was also significant. The proportion of patients with atrial SMR categorized into class I or II increased from 26.2 percent at baseline to 79.5 percent at 1 year. [HFSA 2024, abstract P2424]

Quality of life, measured using the Kansas City Cardiomyopathy Questionnaire overall summary (KCCQ-OS) scores, improved by 19 points from baseline to 1 year after TEER (p<0.001). “This is considered a clinically significant improvement,” said lead author Professor Mark Ricciardi, Chair of Cardiology at the NorthShore University HealthSystem in Evanston, Illinois, US.

“Importantly, the all-cause mortality rate was low at 9 percent after 1 year. This compares favourably with other patients with SMR in the EXPANDed cohort and patients in previous clinical trials of SMR,” stated Ricciardi.

Outcomes comparable to ‘all SMR’ patients

The EXPANDed cohort was examined to study the characteristics and outcomes of patients with atrial SMR (n=160), defined as SMR with a history of atrial fibrillation (AF) and a left ventricular (LV) ejection fraction ≥45 percent, along with evidence of left atrial (LA) enlargement based on cutoffs for LA volume and/or diameter parameters.

On average, patients in the atrial SMR subgroup had 1.4 clips implanted, the same as in the overall SMR cohort ('all SMR'; n=967). Acute procedural success rates were high in both patient groups (97.5 percent vs 95.8 percent), with no procedural deaths.

For the comparison of outcomes at 1 year, the proportions of patients in the all SMR cohort with an MR grade of ≤1+ and in NYHA class I or II were 94.3 percent and 77.9 percent, respectively. The improvement in KCCQ-OS scores from baseline (19 points; p<0.001) was identical to the atrial SMR subgroup.

The magnitude of reduction in annualized HF hospitalization rates after the procedure was similar between atrial SMR patients and all SMR patients (56 percent vs 60 percent reduction).

All-cause mortality may represent a slight discrepancy, as the Kaplan-Meier 1-year estimates were 9 percent for atrial SMR patients vs 15.7 percent for all SMR patients.

Few single-leaflet device attachment events were reported at 1 year, with one event occurring in the atrial SMR subgroup (0.6 percent vs 0.5 percent in all SMR).

EXPAND and EXPAND G4

EXPANDed was established by pooling patient-level data from two global, prospective, single-arm, post-market observational studies, EXPAND and EXPAND G4, which collected safety and effectiveness data on third- and fourth-generation clip devices, respectively, in the real world. [JACC Cardiovasc Interv 2023;16:589-602; JACC Cardiovasc Interv 2023;16:2600-2610]

Atrial SMR, which has emerged as a topic of interest, is characterized by a dilated left atrium and mitral annulus with preserved LV systolic function. [J Am Coll Cardiol 2011;58:1474-1481] However, the exact definition of atrial SMR is not consistent across studies, and the presence of AF may not be a prerequisite for an atrial SMR diagnosis. [JAMA Netw Open 2024;7:e2428032]

The definition of atrial SMR in the current analysis follows a previous analysis of EXPAND alone. [JACC Cardiovasc Interv 2022;15:1723-1730]