Chronotropic Incompetence Limits Aerobic Exercise Capacity in Patients Taking Beta-Blockers: Real-Life Observation of Consecutive Patients.
BACKGROUND
Chronotropic incompetence in patients taking beta-blockers is associated with poor prognosis; however, its impact on exercise capacity (EC) remains unclear.


METHODS
We analyzed data from consecutive patients taking beta-blockers referred for cardiopulmonary exercise testing to assess EC. Chronotropic incompetence was defined as chronotropic index (CI) ≤ 62%.


RESULTS
Among 140 patients all taking beta-blockers (age 61 ± 9.7 years; 73% males), 64% with heart failure, chronotropic incompetence was present in 80.7%. EC assessed as peak oxygen uptake was lower in the group with chronotropic incompetence, 18.3 ± 5.7 vs. 24.0 ± 5.3 mL/kg/min, p < 0.001. EC correlated positively with CI (β = 0.14, p < 0.001) and male gender (β = 5.12, p < 0.001), and negatively with age (β = -0.17, p < 0.001) and presence of heart failure (β = -3.35, p < 0.001). Beta-blocker dose was not associated with EC. Partial correlation attributable to CI accounted for more than one-third of the variance in EC explained by the model (adjusted R2 = 59.8%).


CONCLUSIONS
In patients taking beta-blockers, presence of chronotropic incompetence was associated with lower EC, regardless of the beta-blocker dose. CI accounted for more than one-third of EC variance explained by our model.
['Smarz|Krzysztof|K|0000-0001-9687-8691', 'Tysarowski|Maciej|M|', 'Zaborska|Beata|B|', 'Pilichowska-Paszkiet|Ewa|E|0000-0001-6572-9183', 'Sikora-Frac|Małgorzata|M|0000-0002-7011-7891', 'Budaj|Andrzej|A|', 'Jaxa-Chamiec|Tomasz|T|']
chronotropic incompetence exercise capacity exercise test chronotropic index oxygen uptake adrenergic beta antagonists