Chronotropic incompentence and functional capacity in chronic heart failure: no role of β-blockers and β-blocker dose.
OBJECTIVE
To assess the effect of chronotropic incompetence on functional capacity in chronic heart failure (CHF) patients, as evaluated as NYHA and peak oxygen consumption (pVO(2) ), focusing on the presence and dose of β-blocker treatment.


METHODS
Nine hundred and sixty-seven consecutive CHF patients were evaluated, 328 of whom were discarded because they failed to meet the study criteria. Of the 639 analyzed, 90 were not treated with β-blockers whereas the other 549 were. The latter were further subdivided in high (n = 184) and low (n = 365) β-blockers daily dose group in accordance with an arbitrary cut-off of 25 mg for carvedilol and of 5 mg for bisoprolol. Failure to achieve 80% of the percentage of maximum age predicted peak heart rate (%Max PHR) or of HR reserve (%HRR) constituted chronotropic incompetence.


RESULTS
No differences were found in NYHA or pVO2 between patients with and without β-blockers and, similarly, between high and low β-blocker dose groups. Twenty and sixty-nine percent of not β-blocked patients showed chronotropic incompetence according to %Max PHR and %HRR, respectively, whereas this prevalence rose to 61% and 84% in those on β-blocker therapy. Patients taking β-blockers without chronotropic incompetence, as inferable from both %Max PHR and %HRR, showed higher NYHA and pVO2 regardless of drug dose, whereas, in not β-blocked patients, only %HRR revealed a difference in functional capacity. At multivariable analysis, HR increase during exercise (ΔHR) was the variable most strongly associated to pVO2 (β: 0.572; SE: 0.008; P < 0.0001) and NYHA class (β: -0.499; SE: 0.001; P < 0.0001).


CONCLUSIONS
ΔHR is a powerful predictor of CHF severity regardless of the presence of β-blocker therapy and of β-blocker daily dose.
Magrì
Damiano
D
U.O. Cardiologia, S. Andrea Hospital, Sapienza University, Rome, Italy.
Palermo
Pietro
P
Cauti
Filippo M
FM
Contini
Mauro
M
Farina
Stefania
S
Cattadori
Gaia
G
Apostolo
Anna
A
Salvioni
Elisabetta
E
Magini
Alessandra
A
Vignati
Carlo
C
Alimento
Marina
M
Sciomer
Susanna
S
Bussotti
Maurizio
M
Agostoni
Piergiuseppe
P
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage* / Q000627:therapeutic use*; D000368:Aged; D017298:Bisoprolol / Q000008:administration & dosage / Q000627:therapeutic use; D002227:Carbazoles / Q000008:administration & dosage / Q000627:therapeutic use; D000077261:Carvedilol; D002908:Chronic Disease; D004305:Dose-Response Relationship, Drug; D004452:Echocardiography; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D011412:Propanolamines / Q000008:administration & dosage / Q000627:therapeutic use; D016277:Ventricular Function, Left / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D002227:Carbazoles; D011412:Propanolamines; D000077261:Carvedilol; D017298:Bisoprolol