News · Heart & Metabolic
How well the heart's upper chamber squeezed predicted deaths in amyloidosis; its size did not
Transthyretin amyloidosis stiffens the heart, and clinicians judge the upper chambers by how enlarged they look. Measuring 644 patients found the measurement everyone uses carried no signal.
- Worse squeezing of the upper chamber tracked more deaths and heart events.
- It also tracked more heart failure admissions and new irregular rhythms.
- Chamber size, the routine measurement, tracked none of those outcomes.
- The measure did not predict who benefited more from the drug being trialled.
- 644 patients within a trial, median age 77 and overwhelmingly male.
Every echocardiogram report carries a number for how big the heart’s upper left chamber is. Enlargement has been read for decades as the sign of a chamber under strain, and it appears on the report because it is easy to measure.
Whether it is the right thing to measure is a separate question, and one that rarely gets asked of a number that routine.
Why amyloidosis makes the upper chamber worth measuring
Transthyretin amyloidosis with heart involvement is a stiffening disease. A transport protein misfolds, deposits in the muscle, and the heart becomes a poor filler rather than a poor pumper.
Writing in JAMA Cardiology, researchers used the echocardiograms collected inside a drug trial, which gave them 655 patients assessed to a consistent standard with outcomes tracked afterwards. Previously the prognostic value of upper-chamber function in this disease had not been established at this scale.
They compared two things: how well the chamber squeezed, and how big it was.
What left atrial strain predicted
Patients whose upper chamber squeezed more weakly died more often and had more cardiovascular events.
The same measure tracked admissions for heart failure, and it tracked the development of atrial fibrillation, the irregular rhythm that so often accompanies this disease and complicates its management.
Each of those associations held after accounting for the other things that predict a bad course, so the measurement was carrying information of its own rather than restating disease severity.
What chamber volume predicted, which was nothing
Nothing.
Left atrial volume, the number that appears on every report, was not associated with death, with cardiovascular events, with heart failure admissions or with new atrial fibrillation.
That is the finding worth pausing on. It is not that size was a weaker predictor than function. In this population it was not a predictor at all.
Why a stiff atrium need not be an enlarged one
A chamber can be enlarged because it has been stretched over years and still contract reasonably. A chamber can be normal in size and barely move, which is what amyloid deposits produce: a wall too stiff to stretch and recoil.
In a disease whose whole mechanism is stiffening rather than dilating, it makes sense that the measure of stiffness carries the signal and the measure of dimension does not. What makes this more than a technical footnote is that clinical practice has it the other way round.
Why strain cannot say who vutrisiran helps
This measure predicted who did badly. It did not predict who benefited from treatment.
Strain at the outset did not modify the effect of the drug being trialled, which means it cannot be used to decide who to treat. A marker that tells you someone is in trouble without telling you what to do about it is useful for counseling and planning and not for selecting therapy.
Who the 644 amyloidosis patients were
Median age 77, and only about one in thirteen participants was female, with the large majority having the non-inherited form.
That skew is characteristic of this disease and it still limits the reach of the result. These were also trial participants, who are healthier and more closely monitored than the patients a clinic sees.
What an amyloidosis scan report could add today
The deposits can collect in organs such as the kidney and heart, and the cardiac form is being diagnosed far more often than it used to be as awareness and imaging improve.
The practical suggestion here is small and cheap: the information already exists in the echocardiogram being performed, and extracting the function measure rather than only the size measure would tell the clinician something the current report does not.
People also ask
What did the analysis find?
Among 644 patients (median age 77 years; 7.5% female; 88.4% wild-type disease), reservoir and contractile strain were independently associated with all-cause mortality and recurrent cardiovascular events (reservoir strain hazard ratio per 5% worsening 1.37; 95% CI, 1.13-1.68; P = .002), heart failure hospitalizations (1.66; 1.22-2.25; P = .001) and incident atrial fibrillation (1.30; 1.03-1.63; P = .03). Left atrial volume index was not associated with these outcomes.
What is transthyretin amyloidosis?
A condition in which a transport protein misfolds and deposits in tissues. When it accumulates in heart muscle the walls thicken and stiffen, so the heart fills poorly. It is increasingly recognized in older adults previously labeled as having heart failure of unclear cause.
What is left atrial strain?
A measure of how much the wall of the heart's upper left chamber stretches and recoils across the cardiac cycle, taken from an ultrasound. It reflects function rather than dimensions.
How is that different from volume index?
Volume index measures how big the chamber is, adjusted for body size. It is the standard number reported on every echocardiogram, and enlargement has long been treated as the marker of a struggling atrium.
Why does it matter that volume showed nothing?
Because it is what clinicians actually look at. If size carries no prognostic signal in this disease while function does, the routine report is recording the less informative of the two.
Did it identify who the drug helps?
No. Strain at the outset did not modify the treatment effect of vutrisiran, so it works as a prognostic marker rather than as a way of selecting patients for treatment. Those are different jobs.
What should a patient take from this?
Nothing to act on directly; which measurements to report is a decision for the cardiology team. This is general information rather than medical advice.