Figure 4. Lidocaine reduced heart rate with preserved cardiac contractile function.

Mouse ex vivo working heart was pace at right atrium and perfused with Kreb’s solution containing 2.75 mM Ca²⁺. Comparisons of LV functions at 480 bpm or ~230 bpm in the absence of lidocaine, and at 120 bpm in the presence of 300 μM lidocaine showed that LVPmax and LVPmin did not change between the three conditions (A). Independent of lidocaine, the slower heart rates of ~260 and 120 bpm both decreased LV systolic and diastolic velocities (B), increased stroke volume (C), increased the time to develop peak pressure (TPT) and 50% of peak pressure (TP50) and the time for 50% (TR50) and 75% (TR75) relaxation (D) and elongated the total ejection time (ET) including both rapid and reduced ET (E). The only difference unique to 120 bpm in the presence of 300 μM lidocaine was the a longer TP50 (D). N=5 of each condition. Values are presented as mean ± SE. *P<0.05 vs. 480 bpm; ^#P<0.05 vs. ~230 bpm. Statistical analysis was performed using Student’s t test.