Heart palpitations occur when the normal rhythm of the heart becomes abnormal. Normally, the top two chambers of the heart, called the atria, deliver blood to the bottom two chambers of the heart, called the ventricles, which pump the blood out to the body. Then the cycle repeats. Any different rhythm, such as the atria beating out of synchronization from the ventricles, or a very rapid or very slow heart beat is considered to be an arrhythmia. Treating an arrhythmia may mean fixing an underlying condition, such as high acid or carbon dioxide in the blood. Anti-arrhythmic drugs may also be given.
Class I Antiarrhythmics
The heart utilizes electrical currents to maintain a stable rhythm. Part of the mechanism involved in creating these currents uses charged minerals called electrolytes such as sodium, potassium and calcium to generate electrical impulses. Class I anti-arrhythmics treat palpitations by inhibiting tiny channels on heart cells involved in transferring sodium. This has the effect of slowing conduction down. Examples include disopyramide, flecainide, procainamide, propafenone and quinidine.
Class II Antiarrhythmics
Class II agents inhibit part of the nervous system responsible for fight or flight reactions, called the sympathetic nervous system. They stop hormones such as adrenalin from binding to the heart and increasing its rate and level of excitement. These drugs are called beta-blockers, and include such agents as atenolol, propranolol, metoprolol and esmolol.
Class III Antiarrhythmics
Class III agents treat palpitations similarly to class I agents in that they slow the electrical activity of the heart. They bind to potassium channels, however, instead of sodium channels. Examples include amiodarone, ibutilide and dofetilide.
Class IV Antiarrhythmics
Class IV agents work by slowing down conduction in the major electrical pacemakers of the heart, called the sinoatrial and atrioventricular nodes. These areas of the heart regulate how quickly the heart beats and if they do not function correctly they can propagate abnormal rhythms. They work by binding to calcium channels. Examples include verapamil and diltiazem.
Other Agents
Other agents exist that do not fit into the four-class classification system. These drugs have uses for specific types of palpitations. Examples include adenosine, digoxin and magnesium.
References
- "Basic and Clinical Pharmacology"; Bertram Katzung, Susan Masters, and Anthony Trevor; 11th Ed 2009
- "Hurst's the Heart"; Valentin Fuster, Robert O'Rourke, Richard Walsh, and Philip Poole-Wilson; 12th Ed 2007
