Comparing global and local control of cardiac alternans

Under normal conditions, the action potential duration (APD) of cardiac cells should be equal. But in a heart with cardiac alternans, APD alternates between short and long values beat-to-beat, which can lead to life-threatening arrhythmias. Previous results have shown that constant diastolic (DI) pacing can prevent the formation of alternans, although constant and consistent DI pacing is difficult to achieve in practical applications.

Using a 1D numerical model of human ventricular tissue, Thakare et al. compared the performance of constant DI pacing to constant tricuspid regurgitation (TR) pacing, which is electrocardiogram (ECG)-based and easier to use. Examining the two protocols using cables with different lengths of strips of cardiac cells, they found that constant TR pacing exhibits better control of alternans in longer cables.

Both methods electrically stimulate cardiac cells after a certain interval following an APD. The interval in constant DI pacing is determined with local information from a single cell, whereas in constant TR pacing the interval is determined from the global electrical activity of the entire cable.

The authors found that both protocols can control alternans better than the traditional basic cycle length-based control mechanism, and constant TR pacing can prevent earlier onsets of alternans in longer cables, possibly due to its consideration of spatial inhomogeneity inside the cable. A more comprehensive understanding of the performance disparity between the two protocols will require further experimental studies.

Author Sanket Thakare said that the team plans to next use a 2D model with spatial heterogeneities to assess the effects of ECG lead placements on alternans control with constant TR pacing, as this study placed ECG leads only at the cable ends.

Source: “Global versus Local Control of Cardiac Alternans in a 1D Numerical Model of Human Ventricular Tissue,” by Sanket Thakare, Joseph Mathew, Sharon Zlochiver, Xiaopeng Zhao, and Elena G. Tolkacheva, Chaos (2020). The article can be accessed at https://doi.org/10.1063/5.0005432 .