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. Author manuscript; available in PMC: 2021 Jun 1.
Published in final edited form as: Heart Rhythm. 2020 Feb 15;17(6):1025–1033. doi: 10.1016/j.hrthm.2020.02.007

Figure 3. Chronotropic reserve is impaired in aged rats.

Figure 3.

A, In vivo dobutamine stress was used to determine the chronotropic reserve in young and aged animals; Representative ECG recordings (B) and quantification of β-adrenergic-induced heart rate (HR) increase (C, circle: baseline and square: dobutamine-induced HR response); D, β-adrenergic responsiveness in both groups; E, HR recovery time after maximal effect of dobutamine. Data are expressed as individual values (before-after, C) and mean ± SEM. Paired (C) and unpaired Student’s t-test (D). Double-exponential fit of HR decay phase was used. ***P<0.01 vs. baseline and *P<0.05 vs. young females.