Correlation of heart rate variability with cardiac functional and metabolic variables in cyclists with training induced left ventricular hypertrophy

Objective-To examine the correlation between heart rate variability and lef t ventricular mass in cyclists with an athlete's heart. Methods-Left ventricular mass and diastolic function were determined at res t and myocardial high energy phosphates were quantified at rest and during atropine-dobutamine stress in 12 male cyclists and 10 control subjects, usi ng magnetic resonance techniques. Ambulatory 24 hour ECG recordings were ob tained, and time and frequency domain heart rate variability indices were c omputed. Results-In the cyclists, the mean of all RR intervals between normal beats (meanNN), the SD of the RR intervals, and their coefficient of variation we re significantly greater than in control subjects (p < 0.01, p < 0.01, and p < 0.05, respectively). For cyclists and control subjects, only meanNN cor related with left ventricular mass (r = 0.48, p = 0.038). The heart rate va riability indices that correlated with functional or metabolic variables we re: meanNN v E/A peak (the ratio of peak early and peak atrial filling rate ) (r = 0.48, p = 0.039); the root mean square of successive differences in RR intervals among successive normal beats v EIA area (ratio of peak early and peak atrial filling volume) (r = 0.48, p = 0.040); percentage of succes sive RR intervals differing by more than 50 ms v the phosphocreatine to ATP ratio at rest (r = 0.54, p = 0.017); and the SD of the average RR interval s during all five minute periods v the phosphocreatine to ATP ratio during stress (r = 0.60, p = 0.007). Conclusions-Highly trained cyclists have increased heart rate variability i ndices, reflecting increased cardiac vagal control compared with control su bjects. Left ventricular mass has no major influence on heart rate variabil ity, but heart rate variability is significantly correlated with high energ y phosphate metabolism and diastolic function.