Introduction Abnormal cardiac fibrosis predisposes to diastolic function, heart failure and adverse outcomes in patients with cardiovascular disease. Patients with atrial fibrillation (AF) are known to have excessive left ventricular (LV) fibrosis but contributing factors are poorly understood.

Purpose To investigate whether high heart rate predisposes to cardiac fibrosis in AF.

Methods We studied 215 patients with permanent AF (median (IQR) age 73 (51–88) years, 78% males) over a 2 year period from general practice and outpatient clinics. Exclusion criteria included age <50 years, ejection fraction <55%, recent CABG, severe airways disease, BP >160/90 mmHg, advanced renal dysfunction (table 1).

Integrated calibrated backscatter (cIB) was assessed using echocardiographic acoustic densitometry. LV cIB was calculated as an average of septal and posterior wall cIB values. A lower cIB reflects a higher degree of cardiac fibrosis. Predictive value of resting high heart rate for increased cardiac fibrosis was assessed using univariate linear regression and further multivariate linear regression after adjustment for age, gender, pulse pressure, history of diabetes, N-terminal pro brain natriuretic peptide (NT-pro-BNP) levels and E/E’ ratio.

Results Higher heart rate was associated with increased cardiac fibrosis on both univariate and multivariate analysis (p=0.05 and 0.02, respectively), but not gender, age, weight, pulse pressure, E/E’, or the presence of diabetes. Higher NT-pro-BNP levels were associated with less cardiac fibrosis (p=0.03 on multivariate analysis) (table 2).

Conclusion Raised resting heart rate in patients with permanent AF is associated with increased cardiac fibrosis. This highlights the need to optimise heart control in patients with permanent AF to minimise adverse remodelling in this patient population.