(Cardiac) complexity needs interaction.

The heart exemplifies a complex system where electrical, mechanical, and biochemical processes interact dynamically. Understanding cardiac complexity requires exploring these interactions across multiple levels, from cellular dynamics to organ-wide behavior. This collection examines key interactions in cardiology, including excitation-contraction coupling, arrhythmia quantification, electromechanical modeling, and imaging advances. By integrating mathematical, computational, and clinical perspectives, researchers uncover novel insights into heart function and dysfunction. Progress in this field relies on interdisciplinary collaboration, emphasizing the vital role of human interaction in translating discoveries into improved diagnostics and treatments.