# Forward Flow in Patients With Heart Failure and Functional Mitral Regurgitation: The COAPT Trial

## TL;DR

This study shows that patients with heart failure and functional mitral regurgitation who have low forward flow benefit most from a specific heart repair procedure.

## Contribution

The study reveals that TEER provides the greatest absolute benefit for patients with the lowest baseline forward flow.

## Key findings

- Low baseline forward flow was linked to worse outcomes in patients receiving only medical therapy.
- TEER plus medical therapy reduced the primary outcome most in patients with the lowest forward flow.
- Forward flow did not significantly improve after TEER during the 2-year follow-up.

## Abstract

Heart failure (HF) is characterized by a reduction in forward cardiac output (forward flow), potentially worsened by functional mitral regurgitation (FMR). The impact of reduced forward flow in HF patients with FMR is uncertain, and the outcomes of mitral transcatheter edge-to-edge repair (TEER) according to forward flow levels have not been described.

This study assessed the change in baseline flow in patients with HF and FMR enrolled in the COAPT trial randomized to TEER plus guideline-directed medical therapy (GDMT) compared with GDMT alone. Patients were stratified into tertiles of baseline forward flow using the Doppler-derived stroke volume index. The primary outcome was the composite rate of death or HF hospitalization at 24 months. Clinical, echocardiographic, and outcome measures were assessed.

Among patients randomized to GDMT alone, the lowest baseline forward flow tertile was associated with worse outcomes (P = .04). In contrast, baseline forward flow tertile was not associated with outcomes among patients randomized to TEER + GDMT (P = .88). Patients in the lowest tertile treated with TEER + GDMT had the largest absolute reduction in the primary outcome (44.6% vs 75.7%; hazard ratio [HR], 0.43; 95% CI, 0.29-0.63), whereas patients in the highest tertile had the smallest absolute benefit after TEER (42.8% vs 57.9%; HR, 0.69; 95% CI, 0.45-1.04). However, the relative treatment effect was not different between tertiles (pinteraction = 0.32). Mean forward flow did not significantly increase during 2-year follow-up, and was similar between treatment groups at all time periods.

In the COAPT trial, lower baseline forward flow was associated with worse outcomes in medically managed patients, and those with low baseline forward flow derived the greatest absolute benefit from TEER. However, measured forward flow did not improve with TEER during the 2-year follow-up.