Discharge heart rate shows promise for predicting post-AMI mortality

An elevated heart rate upon hospital admission has been repeatedly linked to an increased risk of mortality for acute MI patients (AMI), making admission heart rate a key component of risk-stratification equations. But researchers recently found a patient’s heart rate at discharge was an even more powerful predictor of death over three years of follow-up, potentially offering an opportunity to update those algorithms.

Lead author Venkatesh Alapati, MD, and colleagues pooled patients from two prospective AMI registries encompassing 6,576 patients. After adjusting for demographic, psychosocial and clinical covariates, they found every increase of 10 beats per minute was associated with a 14 percent increased risk of death during follow-up. That was deemed a significantly stronger association than for admission heart rate, which was tied to a 5 percent increased risk of death per 10 bpm increase.

Notably, the use of beta-blockers modified the association of discharge heart rate and mortality. Those discharged with high heart rates but taking the medications had a 10 percent higher risk of death per 10 bpm increase, while those not taking beta-blockers showed a 35 percent increased risk of mortality for that magnitude of bpm difference.

“Although additional investigations are required, these findings suggest that discharge heart rate could improve risk stratification over admission heart rate, a measure included in available risk‐prediction indexes for shorter‐term mortality after AMI,” Alapati, a cardiology fellow at New York-Presbyterian Brooklyn Methodist Hospital, and co-authors wrote in the Journal of the American Heart Association.

“Whether the use of other heart rate-lowering medications or intensifying β‐blocker therapy to achieve lower heart rate targets could modify the observed association between discharge heart rate and mortality after AMI merits further study.”

The authors said theirs is the first study in a racially diverse U.S. population to report this association, and to find a stronger association with discharge heart rate versus admission heart rate. Patients included in the analysis were 60 years old on average. One-third were women and 24 percent of participants were black.

When compared to patients with discharge heart rates below 60 bpm, those with rates from 80 to 90 bpm and above 90 bpm had increased mortality risks of 41 and 50 percent, respectively.

Alapati and colleagues pointed out their conclusions stemmed from patients treated from 2003 to 2008 and may not be completely generalizable to current practice. Also, they were unable to analyze outcomes by the dose of beta-blocker administered or by type of beta-blocker.

“That the final in‐hospital heart rate emerged as a stronger risk factor for 3‐year mortality than admission heart rate among patients with AMI is unsurprising because this measure of autonomic tone and (patho)physiologic stress reflects the clinical evolution and impact of treatment of the index event throughout the hospitalization for those surviving to discharge,” Alapati et al. wrote.

“Although it is not possible herein to determine to what extent discharge heart rate is acting as a risk factor as opposed to a risk marker, the fact that discharge heart rate was robustly associated with mortality despite extensive adjustment supports the value of this readily obtained parameter for risk stratification.”