ABSTRACT
Despite the significant progress in the fields of electrocardiology and cardiac biomechanics, theoretic limitations still exist and many problems on mechanism underlying the electrical changes of the heart still remain to be solved. Based on the fact that experimental studies deeply rely on the microscopic and quantitative information, and the electrical changes and mechanical activities of the heart have long been treated as two individual processes, dynamic forces generated in the whole spring-loading system during the cardiac contraction and relaxation were discussed first from a macroscopic view. Next, the temporal co-relationship between the electrical and mechanical processes after “excitation-contraction coupling” was particularly identified, which indicated that the intertwined electrical and mechanical activities, in their nature, are integrated parts of a same process. Finally, once all the electrical and mechanical “gating” mechanisms were taken into consideration, the electrical changes of the heart could be classified into three different phases: the preceding excitation formation and conduction, the myogenic changes during ventricular contraction, and the complete restoration of the heart both mechanically and electrically during active relaxation.