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Heart FailureDecember 2016Summary reviewed August 2026

A Heart Pill Improved Pumping Power and Shrank Heart Size in Heart Failure Patients

Patients with weak heart pumping took a twice-daily pill that directly strengthens heart muscle contractions. After 20 weeks, their hearts pumped more blood per beat, shrank in size, and showed lower levels of a stress hormone linked to heart failure. The treatment was well-tolerated with no increase in side effects.

What the trial was testing

The COSMIC-HF enrolled 544 patients with heart failure. The study was sponsored by Cytokinetics and tracked outcomes across the full group of patients who matched the trial's eligibility profile.

It was initial testing (phase 2). Trials at this stage are designed to produce evidence regulators and physicians can act on — not just observations to follow up later.

What the results showed

The pill increased stroke volume by 3.6 mL and reduced heart chamber size by 1.8 mm in patients with heart failure.

Lancet (London, England) · 2016 · NCT01786512

These findings — that hearts pumped more blood with each beat compared to placebo — were published in the Lancet (London, England) and represent the headline result of the study.

Researchers tracked outcomes across 544 patients enrolled in the trial. The result was consistent enough across the group that the team felt confident reporting it.

What this means for patients

For patients with heart failure, this result changes the calculus on what to ask their care team about. Whether it changes day-to-day care depends on factors like disease subtype, prior treatments, and where the patient is in their care journey.

What you can do now

This treatment improved how well the heart pumps and helped reduce dangerous heart enlargement. This was a mid-stage study and the pill is not yet FDA-approved. If you have heart failure, ask your doctor about clinical trials testing this medication or other treatments that strengthen heart muscle.

Eligibility for the treatments mentioned above depends on specific test results and clinical history. Bring this summary, the trial name, and your most recent labs or pathology report to your next visit.