Heart block is a problem that occurs with the heart's electrical system. This system controls the rate and rhythm of heartbeats. ("Rate" refers to the number of times your heart beats in a minute. "Rhythm" refers to the pattern of regular or irregular pulses produced when the heart beats over time.)
With each heartbeat, an electrical signal spreads across the heart from the upper to the lower chambers. As it travels, the signal causes the heart to contract and pump blood. This process repeats with each new heartbeat.
Heart block occurs if the electrical signal is slowed or disrupted as it moves from the upper to the lower chambers of the heart.