Design: Multicentre international cohort with derivation and external validation
Population: 1101 patients with newly diagnosed transthyretin amyloid cardiomyopathy
Primary outcome: All-cause mortality and first heart failure hospitalisation
Effect: Composite MR grade HR 1.20 (1.07–1.36) for death, 1.21 (1.05–1.38) for HF admission; 21% graded severe vs 12–13% by guidelines

An international cohort of 1101 patients with newly diagnosed transthyretin amyloid cardiomyopathy (ATTR-CM), with core-laboratory echocardiography, derived and externally validated mitral regurgitation (MR) thresholds tied to outcome. It was published in Circulation on 13 October.

Over a median two years, 29% died and 22% were admitted with heart failure. Risk rose from a regurgitant volume of about 15 mL or a regurgitant fraction of 20%, and was high above 38 mL or 35%. These cut-offs are well below the usual guideline thresholds for severe MR. The composite scheme labelled 21% as severe, against 12 to 13% by guideline grading, and predicted death and admission better.

The explanation is the small, stiff ventricle with low forward flow: a modest regurgitant volume is a large share of a small stroke volume. Grading by standard criteria therefore underestimates the burden in these hearts. Whether intervening on MR earlier helps is untested.

Report regurgitant fraction, not only volume, in ATTR-CM; a fraction of 35% or more marked high risk.
Treat 'moderate' MR in amyloid hearts as prognostically heavier than in a normal-sized ventricle.
Use MR findings to inform follow-up intensity, not yet to time valve intervention.
Ask echocardiographers to quantify MR in every new ATTR-CM study.

Why it matters

Standard MR grading underestimates risk in restrictive, low-flow ventricles.

The statistics, in plain English

Hazard ratios of 1.20 for death and 1.21 for heart failure admission are per step of the composite MR grade after adjustment. The thresholds were derived in one group and checked in another, which makes them more trustworthy than single-cohort cut-offs.