Related Experiment Videos
Modeling triggered cardiac activity: an analysis of the interactions between potassium blockade, rhythm pauses, and
W J Gibb1, M B Wagner, M D Lesh
1Cardiovascular Research Institute, University of California, San Francisco/Berkeley, USA.
Abstract:
It is known that under certain conditions, a combination of potassium channel blockade, sympathetic nervous activity, and pauses in sinus rhythm can increase the occurrence of cardiac arrhythmias. Although the arrhythmogenic interactions of these three factors are not completely understood, it is believed that the associated arrhythmias may be initiated by afterpotentials via a process that we refer to as propagated triggered activity. Using a two-cell computational model of ventricular action potential kinetics, we simulate nonuniform potassium blockade, sympathetic nervous activity, and pauses in sinus rhythm under conditions of hypokalemia. Under these conditions, the two-cell model suggests that (1) the arrhythmogenic interactions of potassium blockade and sympathetic nervous activity are highly dependent on heart rate; (2) triggered activity induced by potassium blockade would most likely occur during a pause in sinus rhythm; (3) during a sufficiently large pause in sinus rhythm, potassium blockade can induce triggered activity at normal levels of sympathetic activity; and (4) potassium blockade can increase the probability of triggered activity only if heart rate falls within a critical range. We also show that during pauses in sinus rhythm, two-cell triggering interactions between potassium blockade and sympathetic activity closely parallel the parametric displacement of the dynamic instability underlying the afterpotentials. Our results indicate that the behavior of the triggering mechanism studied here is consistent with that of pause-induced arrhythmias.
Insights
Potassium channel blockade and sympathetic activity can trigger cardiac arrhythmias, especially during heart rate pauses. This study models how these factors interact to cause dangerous heart rhythms.
Area of Science:
- Cardiology
- Computational Biology
- Electrophysiology
Background:
- Cardiac arrhythmias can be triggered by a combination of potassium channel blockade, sympathetic nervous system activity, and sinus rhythm pauses.
- The precise mechanisms of these arrhythmogenic interactions, potentially involving afterpotentials and propagated triggered activity, are not fully understood.
Purpose of the Study:
- To investigate the arrhythmogenic interactions between potassium channel blockade, sympathetic nervous activity, and sinus rhythm pauses using a computational model.
- To elucidate the conditions under which these factors induce triggered activity and contribute to cardiac arrhythmias.
Main Methods:
- A two-cell computational model simulating ventricular action potential kinetics was employed.
- Simulations were conducted under conditions of hypokalemia, incorporating nonuniform potassium blockade, sympathetic nervous activity, and sinus rhythm pauses.
Main Results:
- Arrhythmogenic interactions between potassium blockade and sympathetic activity are highly heart rate-dependent.
- Potassium blockade-induced triggered activity is most likely during sinus rhythm pauses.
- Sufficiently long pauses can induce triggered activity even with normal sympathetic activity.
- Potassium blockade increases triggered activity probability within a critical heart rate range.
Conclusions:
- The study's findings align with mechanisms underlying pause-induced arrhythmias.
- Computational modeling provides insights into the dynamic instability of afterpotentials contributing to triggered activity.
- Understanding these interactions is crucial for managing cardiac arrhythmia risk.