Most everyone from time to time feels the heart " skip a beat ", this is called a palpitation. These irregular beats can be due to excessive caffeine intake, physical or emotional stress, metabolic disorders, or they can be idiopathic in nature. Occasional palpitations do not indicate cardiac disease.
A more serious situation exist if the occasional skipped beat turns into a more frequent change in the heart's normal rhythm. This is called an arrhythmia (dysrythmia). Arrhythmia's can originate from the atria or ventricles of the myocardium. Most atrial disturbances are less problematic and cause less harm to the myocardium. Ventricular arrhythmia's, on the other hand, can be fatal. These are most often caused by electrolyte imbalances in the blood like hypokalemia or hyperkalemia. Fatal rythmn disturbances may also be due to heart disease like CAD, coronary artery disease.
Examples of atrial arrythmia's are AF (atrial fibrillation), and PAT (premature atrial contractions). Examples of deadly ventricular dysrhythmia's are VT (ventricular tachycardia), and VF (ventricular fibrillation).