17.5 Class IV: Calcium Channel Blockers
4 min read•june 18, 2024
are crucial medications for managing heart rhythm disorders. They work by blocking calcium entry into heart cells, slowing conduction and reducing contractility. This helps control rapid heart rates in conditions like and .
These drugs also dilate coronary arteries, improving blood flow to the heart. While effective for treating dysrhythmias, they can cause side effects like low blood pressure and slow heart rate. Proper monitoring and patient education are essential for safe and effective use of calcium channel blockers.
Calcium Channel Blockers for Dysrhythmias
Mechanisms of calcium channel blockers
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- Block in cardiac muscle cells
- Reduce calcium influx during depolarization, which is necessary for muscle contraction
- Decrease intracellular calcium concentration, leading to reduced contractility ()
- Disrupt , affecting the heart's ability to contract
- Slow conduction through the
- Prolong AV nodal , preventing rapid impulse transmission
- Decrease ventricular rate in atrial fibrillation and flutter (SVT)
- Dilate coronary arteries
- Improve coronary blood flow, increasing oxygen supply to the heart muscle (myocardium)
- Reduce myocardial oxygen demand by decreasing cardiac workload
- Decrease contractility and oxygen consumption
- Reduce afterload (resistance against which the heart must pump) and preload (volume of blood in the ventricles at the end of diastole)
- Beneficial in by reducing outflow tract obstruction and improving diastolic function
Effects of calcium channel blockers
- Therapeutic uses
- Supraventricular tachycardias (SVT)
- Atrial fibrillation and flutter, characterized by rapid and irregular atrial contractions
- (AVNRT), caused by a reentry circuit within the AV node
- , chest pain caused by insufficient blood flow to the heart muscle
- Hypertrophic cardiomyopathy, a genetic disorder causing thickening of the heart muscle
- Supraventricular tachycardias (SVT)
- Effects
- Slow ventricular rate in SVT, improving cardiac function and reducing symptoms
- Reduce myocardial oxygen demand, alleviating angina symptoms
- Improve coronary blood flow, enhancing oxygen supply to the heart muscle
- Decrease outflow tract obstruction in hypertrophic cardiomyopathy, improving cardiac output
- Exert a , reducing the force of heart contractions
- Potential side effects
- (low blood pressure) due to and reduced contractility
- (slow heart rate) and (impaired conduction) due to AV node suppression
- (swelling) due to vasodilation and fluid retention
- Constipation due to smooth muscle relaxation in the gastrointestinal tract
- Dizziness and headache due to vasodilation and hypotension
Cardiac electrophysiology and calcium channel blockers
- play a crucial role in generating and propagating cardiac action potentials
- Calcium channel blockers primarily affect the plateau phase of the
- These medications influence both chronotropic (heart rate) and inotropic (contractility) effects
- Calcium channel blockers also act on , leading to vasodilation and reduced peripheral resistance
Nursing considerations for administration
- Assess baseline vital signs and cardiac rhythm to establish a reference point
- Monitor blood pressure and heart rate closely
- Report significant changes to the healthcare provider, as they may indicate the need for dose adjustment or intervention
- Administer medication as prescribed
- Use caution in patients with heart failure or conduction disorders, as they may be more sensitive to the effects of calcium channel blockers
- Observe for signs of heart block or
- Prepare for if necessary, to maintain adequate heart rate and cardiac output
- Educate patients on potential side effects and when to seek medical attention
- Encourage medication adherence and regular follow-up appointments to ensure optimal treatment outcomes
Patient education for calcium channel blockers
- Explain the purpose and mechanism of action of the prescribed
- Use simple terms and analogies to help the patient understand how the medication works (slowing down the heart's electrical system)
- Instruct the patient on proper dosage, timing, and administration of the medication
- Emphasize the importance of taking the medication as directed to maintain consistent therapeutic levels
- Discuss common side effects and how to manage them
- Advise when to contact the healthcare provider for concerning symptoms (severe dizziness, fainting, or persistent edema)
- Encourage lifestyle modifications to support heart health
- Regular exercise (walking), stress management (meditation), and a heart-healthy diet (low in saturated fat and sodium)
- Stress the importance of regular follow-up appointments and monitoring
- Discuss the need for periodic blood tests and ECGs to assess the effectiveness and safety of the medication
- Provide written materials and resources for additional information and support
- Include contact information for the healthcare team and emergency services to ensure prompt assistance if needed
Key Terms to Review (34)
Angina Pectoris: Angina pectoris is a type of chest pain or discomfort that occurs when the heart muscle does not receive enough oxygen-rich blood. It is a common symptom of coronary artery disease and can be triggered by physical exertion, emotional stress, or other factors that increase the heart's demand for oxygen.
Atrial Fibrillation: Atrial fibrillation is an irregular and often rapid heart rate that can increase the risk of stroke, heart failure, and other heart-related complications. It occurs when the upper chambers of the heart (the atria) quiver instead of beating effectively, leading to an irregular and sometimes rapid heartbeat.
Atrial fibrillation with rapid ventricular response: Atrial fibrillation with rapid ventricular response (AFib with RVR) is a condition where the atria beat irregularly and frequently, leading to a fast heart rate in the ventricles. This can result in poor blood flow and increased risk of stroke.
Atrial Flutter: Atrial flutter is a type of cardiac arrhythmia characterized by a rapid, regular, and organized electrical activity in the atria of the heart. It is a common dysrhythmia that is closely related to the topics of introduction to dysrhythmias, as well as the various antiarrhythmic drug classes covered in this chapter.
AV Nodal Reentrant Tachycardia: AV nodal reentrant tachycardia is a type of supraventricular tachycardia (SVT) characterized by a reentrant circuit involving the atrioventricular (AV) node. This abnormal heart rhythm is caused by a circular electrical impulse that repeatedly travels through the AV node, leading to a rapid and regular heartbeat.
AV node: The atrioventricular (AV) node is a critical component of the heart's electrical conduction system, responsible for coordinating the contraction of the atria and ventricles. It serves as a relay station, receiving electrical impulses from the atria and transmitting them to the ventricles, ensuring the proper timing and sequence of heart contractions.
Bradycardia: Bradycardia is a slower than normal heart rate, typically defined as fewer than 60 beats per minute in adults. It can be a sign of an underlying health issue or a side effect of certain medications.
Bradycardia: Bradycardia is a condition characterized by an abnormally slow heart rate, typically less than 60 beats per minute. This term is relevant in the context of various cardiovascular and pharmacological topics, as it can be a side effect or complication associated with certain medications and disease states.
Calan SR: Calan SR is a sustained-release formulation of verapamil, a calcium channel blocker used to manage hypertension, angina, and certain types of dysrhythmias. It works by inhibiting the influx of calcium ions into cardiac and smooth muscle cells.
Calcium channel blocker: Calcium channel blockers are medications that inhibit the movement of calcium ions through calcium channels, primarily in the heart and blood vessels. They are used to manage hypertension, angina, and certain dysrhythmias.
Calcium Channel Blockers: Calcium channel blockers are a class of medications that work by inhibiting the movement of calcium ions across cell membranes, particularly in the heart and blood vessels. This mechanism of action makes them useful in the management of various cardiovascular conditions, including dysrhythmias, hypertension, and angina.
Cardiac Action Potential: The cardiac action potential is the electrical signal that initiates and coordinates the contraction of the heart muscle. It is the fundamental process that drives the rhythmic pumping of the heart, which is essential for circulating blood throughout the body.
Cardizem: Cardizem is a brand name for diltiazem, a calcium channel blocker used to treat hypertension, angina, and certain types of arrhythmias. It works by relaxing the muscles of your heart and blood vessels.
Cartia XT: Cartia XT is a brand name for diltiazem, a calcium channel blocker used to treat hypertension and control angina. It works by relaxing the muscles of the heart and blood vessels.
Chronotropic Effect: The chronotropic effect refers to the influence of a drug or substance on the rate and rhythm of the heart. It specifically describes the ability of a compound to increase or decrease the heart rate, thereby altering cardiac contractility and output.
Dilt XR: Dilt XR is an extended-release formulation of diltiazem, a calcium channel blocker used to treat hypertension and control certain types of arrhythmias. It works by relaxing the muscles of the heart and blood vessels.
Diltiazem: Diltiazem is a calcium channel blocker used to treat hypertension, angina, and certain types of arrhythmias. It works by relaxing the muscles of your heart and blood vessels.
Excitation-Contraction Coupling: Excitation-contraction coupling is the process by which an electrical signal, or action potential, triggers the mechanical contraction of a muscle fiber. This coupling of electrical and mechanical events is essential for the proper functioning of skeletal, cardiac, and smooth muscles throughout the body.
Heart Block: Heart block is a type of cardiac conduction disorder where there is an interruption or delay in the electrical impulses traveling from the atria to the ventricles, resulting in an abnormal heart rhythm. This term is particularly relevant in the context of dysrhythmias, as well as the mechanisms of action for various antiarrhythmic drug classes.
Hypertrophic Cardiomyopathy: Hypertrophic cardiomyopathy is a genetic disorder characterized by the thickening (hypertrophy) of the heart muscle, particularly the left ventricle. This abnormal growth can impair the heart's ability to pump blood effectively, leading to various cardiovascular complications. The term is particularly relevant in the context of calcium channel blockers and the management of hypertension and angina.
Hypotension: Hypotension is a medical condition characterized by an abnormally low blood pressure, where the systolic blood pressure falls below 90 mmHg and the diastolic blood pressure falls below 60 mmHg. This can have significant implications on the body's ability to circulate blood and deliver oxygen and nutrients to vital organs.
Inotropy: Inotropy refers to the ability of the heart to change the force or strength of its contractions. It is a key concept in the context of calcium channel blockers, a class of drugs that can influence the inotropic state of the heart.
L-type Calcium Channels: L-type calcium channels are a class of voltage-gated calcium channels that are primarily found in the cell membranes of cardiac muscle, smooth muscle, and certain endocrine cells. These channels play a crucial role in regulating calcium influx, which is essential for various physiological processes such as muscle contraction, hormone secretion, and signal transduction.
Negative Inotropic Effect: A negative inotropic effect refers to the reduction or decrease in the contractility or force of cardiac muscle contraction. This effect is particularly relevant in the context of calcium channel blockers, as they can exert a negative inotropic influence on the heart.
Peripheral Edema: Peripheral edema refers to the abnormal accumulation of fluid in the tissues, typically in the lower extremities such as the legs, ankles, and feet. This condition can occur due to various underlying medical conditions and can have implications in the context of calcium channel blockers and renal-associated fluid volume excess.
Refractory Period: The refractory period is a crucial concept in the context of electrical impulse conduction and the mechanisms of action of certain drug classes. It refers to the period of time following the generation of an action potential during which a cell or tissue is unable to respond to a new stimulus, even if that stimulus would normally be sufficient to elicit a response.
Supraventricular Tachycardia: Supraventricular tachycardia (SVT) is a type of abnormal heart rhythm that originates above the ventricles, typically in the atria or atrioventricular (AV) node. It is characterized by a rapid heart rate, often greater than 150 beats per minute, that can significantly impact the heart's ability to effectively pump blood throughout the body.
Taztia XT: Taztia XT is a brand name for diltiazem, a calcium channel blocker used to treat arrhythmias. It works by inhibiting the influx of calcium ions during cardiac muscle contraction, thus reducing heart rate and stabilizing heart rhythm.
Temporary Pacing: Temporary pacing is a medical procedure used to provide temporary electrical stimulation to the heart when the heart's natural pacemaker is not functioning properly. It is often used as a short-term solution to regulate the heart's rhythm and maintain adequate blood flow until a more permanent pacing solution can be implemented.
Tiazac: Tiazac is a brand name for diltiazem, a calcium channel blocker used to manage hypertension and treat certain types of arrhythmias. It works by inhibiting calcium ions from entering the heart muscle cells and blood vessel walls, leading to relaxation and reduced heart workload.
Vascular Smooth Muscle: Vascular smooth muscle refers to the specialized muscle tissue that lines the walls of blood vessels, responsible for regulating blood flow and pressure throughout the body. These smooth muscle cells are crucial in maintaining cardiovascular homeostasis and are a key component in the mechanism of action of calcium channel blockers, a class of drugs used to treat various cardiovascular conditions.
Vasodilation: Vasodilation refers to the widening or dilation of blood vessels, particularly the arteries and arterioles. This process leads to increased blood flow and reduced vascular resistance, which can have significant implications in various physiological and pharmacological contexts.
Verapamil: Verapamil is a calcium channel blocker used to treat hypertension, angina, and certain types of cardiac dysrhythmias. It works by inhibiting the influx of calcium ions into cardiac and smooth muscle cells, thereby reducing heart rate and dilating blood vessels.
Voltage-Gated Ion Channels: Voltage-gated ion channels are specialized transmembrane proteins that selectively allow the passage of specific ions, such as sodium, potassium, calcium, or chloride, across the cell membrane in response to changes in the membrane's electrical potential. These channels play a crucial role in various physiological processes, including nerve impulse propagation, muscle contraction, and cellular signaling.