Table 4.
Tonic block, % |
Use-Dependent Block, % |
|||
---|---|---|---|---|
Ventricular myocytes | Atrial myocytes | Ventricular myocytes | Atrial myocytes | |
Holding potential | ||||
−120 mV | 0.9 ± 3.3* | 4.1 ± 2.7† | 21 ± 5 | 32 ± 2‡ |
−110 mV | 0.6 ± 5.0* | 5.3 ± 2.1† | 31 ± 5 | 43 ± 5‡ |
−100 mV | 3.1 ± 6.4* | 6.8 ± 2.3† | 47 ± 6 | 56 ± 5‡ |
Values are means ± SD; n = 10 ventricular myocytes and 5 atrial myocytes. Trains of 50-ms pulses to −30 mV with 250 ms at holding potentials between pulses were used.
Not significantly different from zero (P > 0.3).
Significantly different from zero (P < 0.05). In both cell types, tonic block was not significantly dependent on holding potential (P > 0.3 by ANOVA).
Significantly different from the use-dependent block in ventricular cells at all holding potentials (P < 0.05). In both cell types, use-dependent steady-state block was significantly dependent on holding potential (P < 0.01 by single-factor ANOVA).