Key Points
- To characterize the initiation, velocity, and mechanisms of spontaneous and propagating sarcomere contractions in rat cardiac muscle following electrical stimulation.
- Measured sarcomere length via microscopic and laser diffraction techniques in isolated rat heart trabeculae superfused in Krebs-Henseleit solution at 21 °C.
- Evaluated spontaneous contraction propagation velocities and shortening across variable electrical stimulation trains (3–30 pulses at 2 Hz) and extracellular calcium concentrations (1.0–7.0 mM).
- Propagation velocity increased from 0 to 10 mm/s as stimulus train length increased from 3 to 30 pulses at 1.5 mM extracellular calcium, and from 0 to 15 mm/s as extracellular calcium increased from 1 to 7 mM.
- Increases in stimulus count and extracellular calcium augmented the magnitude of local sarcomere shortening, frequently triggering synchronized tissue contractions and arrhythmogenic activity.
Structured PICO
PPopulationRat cardiac trabeculae
IInterventionElectrical stimulation (varying number of stimuli, 3-30) and varying external calcium ion concentration (1 to 7 mM)
CComparatorDifferent levels of electrical stimulation and external calcium concentrations
OOutcomeVelocity of propagation of spontaneous contractions and extent of local sarcomere shorteningsurrogate
Spontaneous contractions in rat cardiac trabeculae propagate at velocities dependent on the number of stimuli and external calcium concentration, potentially leading to arrhythmias.