How are cardiac muscle cells like dominoes?

Each cardiac muscle cell is connected to the cells around it via junctions. These junctions allow the transmission of electric charges (action potential) from cell to cell quickly.



Thus, as one cell contracts, the action potential that was within it moves to the next cell, causing it to contract as well, forming a domino-like effect.



The transmission of the electric impulse, however, is too fast that all cells contract at virtually the same time. So the whole heart muscle contracts all at once.How are cardiac muscle cells like dominoes?
Each one triggers the one next to it.