Anti-Anginals

Chapter 23: Antianginal Drugs

Introduction

• Discussion on the importance of early medical intervention in heart attacks.

• Mention of health plan considerations like emergency room visits, emphasizing the timeliness of treatment to minimize heart damage and improve outcomes.

Pathophysiology of Angina

Oxygen Supply and Demand

• When the oxygen and nutrient supply in the blood is insufficient, the heart muscle experiences ischemia, leading to sensations of ‘aching’ or chest pain.

• A reduction in the supply-demand ratio (e.g., during physical exertion or emotional stress) results in angina.

• The accumulation of lactic acid from anaerobic metabolism during ischemic episodes is a significant contributor to heart pain and discomfort.

• Medications aim to alleviate angina pain by:

  • Increasing blood flow to the myocardium.

  • Decreasing myocardial oxygen demand.

Ischemia

• Definition: Ischemia refers to inadequate blood supply to an organ, which leads to an insufficient oxygen supply.

• Ischemic Heart Disease:

  • Recognized as a primary cause of mortality worldwide.

  • Usually results from atherosclerosis, a condition characterized by plaque buildup.

  • Can lead to myocardial infarction (MI), defined as necrosis of cardiac tissue due to complete blockage of the coronary arteries.

  • Highlight the critical importance of restoring blood flow immediately to prevent disability or death from cardiac events.

Atherosclerosis

Formation of Plaque and Thrombus

• The process involves the deposition of platelets and fibrin on arterial plaque, initiating the formation of a thrombus (blood clot).

• The presence of a thrombus can lead to partial or complete occlusion of the arterial lumen, exacerbating ischemic conditions.

Treatment Protocols

MONA Protocol for Cardiac Care

• Emergency setup for cardiac catheterization follows the MONA protocol, which consists of:

  • Morphine (for pain relief).

  • Oxygen (to increase tissue oxygenation).

  • Nitroglycerin (to dilate coronary arteries and improve blood flow).

  • Aspirin (to prevent further clot formation).

• Cardiac catheterization is considered the gold standard if available and may involve procedures like angioplasty and stent placement.

• Additional medications that may be used include clopidogrel, aspirin (ASA), bivalirudin, and thrombolytics if necessary.

• Long-term management strategies may include the use of statins, beta-blockers, and nitrates for controlling symptoms and preventing future cardiac events.

Classes of Antianginal Medications

Primary Classes

1. Nitrates and Nitrites:

2. Beta Blockers:

3. Calcium Channel Blockers (CCBs):

Therapeutic Objectives of Antianginals

• Key goals include:

  • Minimizing the frequency and intensity of angina attacks.

  • Improving the functional capacity of patients with minimal adverse effects.

  • Preventing or delaying the occurrence of myocardial infarction (MI).

Nitrates

Available Forms

• Various formulations including sublingual tablets, chewable tablets, oral capsules, intravenous (IV) solutions, transdermal patches, ointments, and translingual sprays.

• Sublingual and intravenous forms bypass the first-pass metabolic effect, providing rapid action.

Mechanism of Action

• Nitrates are potent vasodilators that relax smooth muscle in blood vessels, with a primary effect on veins but also extensible to coronary arteries.

• They increase oxygen delivery to ischemic myocardial tissue, forming the cornerstone of angina treatment.

Types of Nitrates

• Rapid-acting agents are utilized for acute anginal attacks (e.g., sublingual tablets).

• Long-acting agents are prescribed to prevent anginal episodes (e.g., isosorbide dinitrate, isosorbide mononitrate).

Adverse Effects of Nitrates

• Common adverse effects include headaches (typically diminish with continued use), reflex tachycardia, and postural hypotension.

• Tolerance may develop over time; nitrate-free periods are recommended to maintain effectiveness.

Contraindications for Nitrates

• Contraindicated in patients with known drug allergies, severe anemia, closed-angle glaucoma, hypotension, severe head injury, and those taking certain erectile dysfunction medications (sildenafil, tadalafil, vardenafil) due to the risk of severe hypotension.

Beta Blockers

Indications and Benefits

• Indicated for multiple cardiovascular conditions, including:

  • Angina, myocardial infarction (MI), dysrhythmias, hypertension, migraines, and performance anxiety (stage fright).

• These medications reduce heart rate and myocardial oxygen demand, contributing to improved survival rates post-MI.

Mechanism of Action

• Cardioselective beta-blockers selectively block beta1 adrenergic receptors, enhancing oxygen delivery to the heart and counteracting the negative impacts of catecholamines.

Contraindications and Cautions

• Use with caution in patients with bronchial asthma, diabetes, and peripheral vascular disease to avoid exacerbating these conditions.

Adverse Effects

• Possible cardiovascular effects include bradycardia and hypotension.

• Metabolic side effects may include hyperglycemia and hypoglycemia.

• Common CNS effects involve dizziness, fatigue, and impotence.

Calcium Channel Blockers (CCBs)

Indications and Mechanism

• Frequently prescribed for chronic stable angina, hypertension, and certain dysrhythmias.

• Mechanism of action involves slowing calcium influx into muscle cells, promoting vascular relaxation and enhanced coronary blood flow.

• They cause peripheral vasodilation, effectively reducing the workload on the heart.

Contraindications

• Known drug allergies, acute MI, heart block without a pacemaker, and hypotension.

Adverse Effects

• Common side effects related to therapeutic effects interfere with blood pressure regulation include hypotension, tachycardia, and constipation.

Miscellaneous Antianginals

Ranolazine

• The precise mechanism of action remains largely unknown, but it is notably recognized for prolonging the QT interval.

• Typically reserved for patients who do not adequately respond to other standard therapies.

Nursing Implications

General Considerations

• A complete health history should be gathered before administering antianginals to identify any potential contraindications.

• Vigilant monitoring of vital signs, particularly blood pressure and heart rate, is crucial during treatment.

• Patients should be educated on potential drug interactions and the importance of reporting any adverse effects experienced.

Specific Instructions for Patients

• Patients should be instructed to report symptoms such as blurred vision, persistent headache, dry mouth, fainting, weight changes, and pulse irregularities promptly.

• Emphasis should be placed on safety, particularly regarding the avoidance of alcohol and thermal hazards due to the vasodilating properties of these medications.

• Proper use of medications, specifically sublingual nitroglycerin, should be thoroughly communicated to ensure effectiveness during acute episodes of angina.