Calcium channel blockers, or CCBs, are drugs that affect the cardiovascular system. CCBs affect heart muscles, and the smooth muscle of arteries and smaller arterioles. CCBs act on cellular calcium channels, which are gate-like channels within the wall of a cell, opening and closing, allowing calcium ions to flow into the cell. Calcium communication in the cell regulates muscle contraction. When calcium ions are allowed to flow into cells, muscular contraction occurs. CCBs block gated calcium channels, thereby preventing calcium ions from entering cells.
Reducing Muscular Contraction
One of the main functions of calcium channel blockers is to cause arteries and arterioles to dilate and relax, thus reducing pressure in the artery. Increased blood pressure is a result of narrowing contractions of the arterial wall. Arteries may also narrow as a result of arterial disease. When these contractions are lessened due to vasodilation, blood pressure drops. CCBs allow oxygenated blood, carried by arteries, to more effectively reach tissue. Calcium channel blockers relax the artery wall, reducing arterial stress. CCBs reduce the amount of force with which the heart contracts, by blocking the flow of calcium to the heart muscle, according to "Pharmacology for Nursing Care." Because of CCBs' vasodilating effects, and their ability to reduce muscular contraction, they can be used to treat aneurysms, angina, high blood pressure and Raynaud's phenomenon or disease.
Slowing the Heart
Calcium channel blockers slow the heart by acting on the heart's pacemaker, the sinoatrial, or SA, node. In the heart, the SA node becomes more active as a result of calcium entering through the gated cellular channels. According to Richard Lehne, when the flow of calcium to the SA node is blocked, the heart slows down due to the reduction in SA node signaling.
Regulating Heart Rhythm
The beating heart is regulated by communication from the SA node, through to the atrioventricular, or AV, node. The AV node is involved in regulating the heart muscle's ventricular contraction. Calcium channel blockers regulate the heart's rhythms by preventing calcium ions from stimulating the heart via the conduction path from the SA node to the AV node. This reduces the contraction rate of the ventricles. CCBs can quiet the AV node, thus helping to reduce any irregular contractions of the heart. Cardiac dysrhythmia, also known as arrhythmia, is an abnormal rhythm of the heart and is treatable using CCBs.
References
- National Institute of Arthritis and Musculoskeletal and Skin Diseases: Raynaud's Phenomenon
- "Pharmacology for Nursing Care"; Richard A. Lehne, Ph.D.; 2007
- "Understanding Pathophysiology"; Sue E. Huether, R.N., Ph.D., Kathryn L. McCance, R.N., Ph. D.; 2008
- National Heart Lung and Blood Institute Diseases and Conditions Index: How is an Aneurysm Treated?
- "Biology"; Robert J. Brooker, Eric P. Widmaier, Linda E. Graham, and Peter D. Stiling; 2008
