Patel V; Critoph CH; Finlay MC; Mist B; Lambiase PD; Elliott PM.

American Journal of Cardiology. 113(6):1011-7, 2014 Mar 15.

Abstract
Recovery in heart rate (HR) after exercise is a measure of autonomic
function and a prognostic indicator in cardiovascular disease. The aim of
this study was to characterize heart rate recovery (HRR) and to determine
its relation to cardiac function and morphology in patients with
hypertrophic cardiomyopathy (HC).
We studied 18 healthy volunteers and 41
individuals with HC. All patients underwent clinical assessment and
transthoracic echocardiography. Continuous beat-by-beat assessment of HR
was obtained during and after cardiopulmonary exercise testing using
finger plethysmography. HRR and power spectral densities were calculated
on 3 minutes of continuous RR recordings.
Absolute HRR was lower in
patients than that in controls at 1, 2, and 3 minutes (25.7 +/- 8.4 vs
35.3 +/- 11.0 beats/min, p <0.001; 36.8 +/- 9.4 vs 53.6 +/- 13.2
beats/min, p <0.001; 41.2 +/- 12.2 vs 62.1 +/- 14.5 beats/min, p <0.001,
respectively). HRR remained lower in patients at 2 and 3 minutes after
normalization to peak HR. After normalization to the difference in HR
between peak exercise and rest, HRR was significantly impaired in
individuals with obstructive HC at 3 minutes compared with controls. HR at
3 minutes correlated with peak left ventricular outflow tract gradient (B
0.154 beats/min/mm Hg, confidence interval 0.010 to 0.299, p = 0.037) and
remained a significant predictor of HRR after multivariable analysis.
Spectral analysis showed a trend toward an increased low-frequency to
high-frequency ratio in patients (p = 0.08) suggesting sympathetic
predominance.
In conclusion, HRR is impaired in HC and correlates with the
severity of left ventricular outflow tract gradient. Prospective studies
of the prognostic implications of impaired HRR in HC are warranted.