Final answer:
Extra beats in the heart are often caused by impulses from ectopic foci, which can be activated by factors like ischemia or drug exposure and can lead to arrhythmias. These aberrations are monitored by an ECG.
Step-by-step explanation:
Skipped or extra beats in the heart are often a result of impulses originating from areas other than the sinoatrial (SA) node. These aberrant impulses can lead to what's known as ectopic beats. Normally, the SA node generates electrical signals that control the timing of the heart's beats.
However, when an ectopic focus, or ectopic pacemaker, becomes active, it may cause a premature contraction of the heart. Various factors including ischemia, drug exposure (such as caffeine or digitalis), and autonomic nervous system imbalances can stimulate these ectopic foci. While infrequent ectopic beats are not typically dangerous, frequent and chronic occurrences can progress to arrhythmias or fibrillation, which can be life-threatening. The electrical activity of the heart, including any abnormalities, is typically monitored through an electrocardiogram (ECG).