Phase-locked rhythms in periodically stimulated heart cell aggregates

Area of Science:

• Cardiology
• Computational Biology
• Biophysics

Background:

• Spontaneously beating aggregates of embryonic chick ventricular heart cells exhibit intrinsic rhythms.
• Understanding how external stimuli influence these cellular pacemakers is crucial for cardiac research.

Purpose of the Study:

• To investigate the effects of periodic current pulse stimulation on cardiac cell aggregates.
• To characterize the resulting rhythms and their relationship to clinical cardiac arrhythmias.
• To develop a predictive classification scheme for observed rhythms.

Main Methods:

• Injected periodic trains of current pulses into spontaneously beating embryonic chick ventricular heart cell aggregates.
• Varied stimulation frequencies around the intrinsic frequency of the cell aggregates.
• Observed and analyzed the resulting action potential patterns and rhythms.

Main Results:

• At frequencies near the intrinsic rate, a fixed latency between stimulus and action potential was observed (overdrive/underdrive).
• Higher stimulation frequencies led to dropped beats and complex rhythms analogous to Wenckebach phenomena.
• Complete suppression of action potentials and rhythms with escape beats were observed at specific frequencies.
• The observed rhythms closely resembled various clinical cardiac arrhythmias.

Conclusions:

• A simple classification scheme was developed to predict the order of rhythm appearance with changing stimulation frequencies.
• The study demonstrates that cardiac cell aggregates can model complex arrhythmias.
• The proposed scheme may be applicable to other biological oscillator systems.