Chronotropic incompetence and its relation to exercise intolerance in hypertrophic cardiomyopathy.
BACKGROUND
Diminished functional capacity is common in hypertrophic cardiomyopathy (HCM), although the underlying mechanisms are complicated. We studied the prevalence of chronotropic incompetence and its relation to exercise intolerance in patients with HCM.


METHODS
Cardiopulmonary exercise testing was performed in 68 patients with HCM (age 44.8 ± 14.6 years, 45 males). Chronotropic incompetence was defined by chronotropic index (heart rate reserve)/(220-age-resting heart rate) and exercise capacity was assessed by peak oxygen consumption (peak Vo(2)).


RESULTS
Chronotropic incompetence was present in 50% of the patients and was associated with higher NYHA class, history of atrial fibrillation, higher fibrosis burden on cardiac MRI, and treatment with β-blockers, amiodarone and warfarin. On univariate analysis, male gender, age, NYHA class, maximal wall thickness, left atrial diameter, peak early diastolic myocardial velocity of the lateral mitral annulus, history of atrial fibrillation, presence of left ventricular outflow tract obstruction (LVOTO) at rest, and treatment with beta-blockers were related to peak Vo(2). Peak heart rate during exercise, heart rate reserve, chronotropic index, and peak systolic blood pressure were also related to peak Vo(2). On multivariate analysis male gender, atrial fibrillation, presence of LVOTO and heart rate reserve were independent predictors of exercise capacity (R(2) = 76.7%). A cutoff of 62 bpm for the heart rate reserve showed a negative predictive value of 100% in predicting patients with a peak Vo(2) <80%.


CONCLUSIONS
Blunted heart rate response to exercise is common in HCM and represents an important determinant of exercise capacity.
Efthimiadis
Georgios K
GK
Cardiomyopathies Laboratory, First Cardiology Department, AHEPA Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece. efthymos@med.auth.gr
Giannakoulas
Georgios
G
Parcharidou
Despina G
DG
Pagourelias
Efstathios D
ED
Kouidi
Evangelia J
EJ
Spanos
Georgios
G
Kamperidis
Vasileios
V
Gavrielides
Stavros
S
Karvounis
Haralambos
H
Styliadis
Ioannis
I
Parcharidis
Georgios E
GE
D000328:Adult; D002312:Cardiomyopathy, Hypertrophic / Q000175:diagnosis* / Q000503:physiopathology*; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies