. Author manuscript; available in PMC: 2019 Jan 1.

Published in final edited form as: J Mol Cell Cardiol. 2017 Nov 17;114:175–184. doi: 10.1016/j.yjmcc.2017.11.011

Table 1.

Effects of decreasing heart rate on the performance of ex vivo mouse working heart

Heart Rate (bpm)	LVP max (mmHg)	LVP min (mmHg)	+dP/dt max (mmHg)	−dP/dt max (mmHg)	Stroke Volume (μL/mg)
480	73.38±0.71	5.33±0.39	3527.64±109.04	−3011.12±75.40	0.173±0.006
420	75.86±1.17	4.38±0.33^*	3669.39±99.90^*	−3159.48±68.37^*	0.202±0.005^*
360	79.65±1.55^#	4.44±0.30^*	3745.55±103.68^*	−3288.97±73.71	0.218±0.006^*
263.8±11.1 (No pacing)	79.21±2.71^*	5.23±0.49^#^&	2925.12±115.46^*^#^&	−2446.35±97.65^*^#^&	0.188±0.009^&

Cardiac function increased when the paced heart rate was decreased from 480 to 420 and 360 bpm as shown by increased LVP max, +/−dP/dt and stroke volume, and decreased LVP min. At heart rate of ~260 bpm in the absence of external pacing, the contractile functions decreased, reflecting a negative impact of this further lowered heart rate on the force-frequency relationship of cardiac muscle. The test was done at 10 mmHg preload and 55 mmHg afterload.

Values are presented as mean ± SE. N = 7 hearts.

P<0.05 vs. 480;

P<0.05 vs. 420;

P<0.05 vs. 360 bpm in paired Student’s t test.