Heart palpitations may be caused by several underlying factors. Sometimes, caffeine intake, emotional stress, or sudden physical exertion can stimulate a brief period of abnormally fast heartbeats. In these cases, the palpitation feeling is temporary and does not return unless the stimulus is repeated. This type of irregularity, or arrhythmia (ah-RITH-mee-ah), generally requires no additional treatment or special attention. However, heart palpitations may also indicate a more serious heart condition deserving medical consideration. For example, an irritable area in the lower ventricular (ven-TRIK-you-lar) pumping chamber may occasionally generate extra beats. The resulting premature ventricular contractions, or PVC (P-V-C), may be detected as missed beat or as a flip-flop feeling in the chest. Although isolated episodes are usually harmless, frequent P.V.C. disturbances can develop into more serious arrhythmias. Other types of rhythm disturbances can be quite critical, such as in either atrial (AY-tree-ul) or ventricular fibrillation (fib-rih-LAY-shun). In these situations, the heart's chambers quiver rather than beating fully, preventing the heart from pumping blood properly. If the problem exists in the upper atrial chambers, the unpumped blood may pool and clot. This may be dangerous, since such a clot can break loose, travel to the brain, and cause a stroke. If the fibrillation arises in the lower ventricular chambers, the heart may stop beating completely, resulting in death. However, if detected in time, both atrial and ventricular fibrillation can be effectively converted into normal rhythms with various medical techniques, depending on the specific problem. If you're concerned about your heart's rhythm, or have questions about heart palpitations, contact a healthcare provider.