Elevated heart rate is associated with increased mortality and rejection in pediatric heart transplant recipients

Elevated heart rate is associated with adverse outcomes in patients with heart failure. Heart transplant recipients often have elevated heart rate; however, the long-term associations of elevated heart rate with clinical outcomes are unknown.

The records of all pediatric (≤21 years) heart transplant recipients at our institution were reviewed. Patients who died or lacked a clinic visit within 1 year following heart transplant were excluded, as were those with a permanent pacemaker. Heart rate was collected from outpatient electrocardiograms and converted to Z-scores using age-specific normative data. The cohort was divided into elevated and normal heart rate groups, with elevated heart rate defined as an average HR Z-score ≥95th percentile during the first post-transplant year. Outcomes, including survival, rejection, and cardiac allograft vasculopathy were compared between groups.

A total of 110 pediatric heart transplants were included (median age 11.4 years; 62% male). Thirty-six (33%) had an elevated heart rate. The elevated heart rate group was older (15.8 vs 6.1 years, p<0.001) and had shorter follow-up (3.0 vs 4.7 years, p = 0.007). Elevated heart rate was independently associated with increased risk of death (HR 5.44, 95% CI 1.47-20.2, p = 0.011) and a composite of death or rejection (HR 3.06, 95% CI 1.30-7.20, p = 0.010), but not cardiac allograft vasculopathy.

Among patients who survive the first year after pediatric heart transplantation, elevated heart rate during the first post-transplant year is independently associated with increased risk of mortality and rejection. Further work is necessary to determine whether pharmacologic modulation mitigates this risk.