4.4 Cardiac arrhythmias and conduction disorders

Cardiac arrhythmias can disrupt the heart's normal rhythm, causing symptoms like palpitations and dizziness. These disorders stem from abnormalities in how the heart generates or conducts electrical impulses. Understanding the mechanisms behind arrhythmias is crucial for effective management and patient care.

Treatment for cardiac arrhythmias includes medications, cardioversion, and implantable devices. Nurses play a vital role in monitoring patients, administering treatments, and providing education. They help patients recognize symptoms, manage medications, and make necessary lifestyle changes to improve their heart health.

Cardiac Arrhythmias and Conduction Disorders

Mechanisms of cardiac arrhythmias

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• Abnormalities in impulse formation
  • Enhanced automaticity occurs when cardiac cells outside the sinoatrial node (SA node) spontaneously generate impulses (ectopic foci)
  • Triggered activity involves abnormal depolarizations during or immediately after a preceding action potential
    • Early afterdepolarizations (EADs) happen during phase 2 or 3 of the action potential (long QT syndrome)
    • Delayed afterdepolarizations (DADs) occur after complete repolarization (digitalis toxicity)
• Abnormalities in impulse conduction
  • Reentry happens when an impulse travels around an anatomical or functional obstacle and re-excites the same area (Wolff-Parkinson-White syndrome)
  • Conduction block prevents impulse propagation through the heart's conduction system (heart block)

Signs of cardiac arrhythmias

• Palpitations are sensations of a rapid, pounding, or fluttering heartbeat
• Dizziness or lightheadedness results from reduced cardiac output and cerebral perfusion
• Syncope is a sudden loss of consciousness due to insufficient blood flow to the brain (vasovagal syncope)
• Chest pain or discomfort may occur due to increased myocardial oxygen demand or reduced supply (angina)
• Shortness of breath happens when the heart cannot efficiently pump blood to meet the body's oxygen needs
• Fatigue or weakness develops as a result of decreased cardiac output and tissue perfusion

Management of cardiac arrhythmias

• Pharmacological management
  • Antiarrhythmic drugs
    • Class I drugs (quinidine) block sodium channels and slow conduction velocity
    • Class II drugs (metoprolol) are beta-blockers that reduce heart rate and contractility
    • Class III drugs (amiodarone) block potassium channels and prolong the action potential duration
    • Class IV drugs (verapamil) are calcium channel blockers that slow conduction and reduce contractility
  • Anticoagulants (warfarin) prevent thrombus formation in patients with atrial fibrillation
  • Electrolyte correction involves maintaining normal levels of potassium, magnesium, and calcium
• Non-pharmacological management
  • Cardioversion
    1. Electrical cardioversion delivers a synchronized shock to restore normal sinus rhythm
    2. Pharmacological cardioversion uses drugs (ibutilide) to convert arrhythmias to sinus rhythm
  • Ablation therapy
    • Radiofrequency ablation uses high-frequency electrical energy to destroy abnormal tissue (supraventricular tachycardia)
    • Cryoablation employs extreme cold to create scar tissue and block abnormal electrical pathways (atrial fibrillation)
  • Implantable devices
    • Pacemakers generate electrical impulses to maintain a normal heart rate (sick sinus syndrome)
    • Implantable cardioverter-defibrillators (ICDs) detect and treat life-threatening ventricular arrhythmias (ventricular tachycardia)
  • Lifestyle modifications include stress reduction techniques (meditation) and avoiding triggers (caffeine)

Nursing care for arrhythmias

• Assess and monitor vital signs to detect changes in heart rate, rhythm, and blood pressure
• Administer medications as prescribed and monitor for therapeutic effects and adverse reactions
• Monitor ECG and telemetry to identify arrhythmias and evaluate treatment effectiveness
• Ensure proper functioning of implantable devices through regular checks and patient education
• Provide emotional support and reassurance to alleviate anxiety and promote coping
• Assist with cardioversion or ablation procedures by preparing the patient and monitoring post-procedure
• Facilitate lifestyle modifications by providing resources and encouraging adherence
• Explain the nature of the arrhythmia and its treatment using simple, easy-to-understand language
• Teach about medications, their actions, side effects (bradycardia with beta-blockers), and importance of adherence
• Instruct on recognizing signs and symptoms of arrhythmia recurrence (palpitations, syncope) and when to seek medical attention
• Educate on proper use and care of implantable devices, including activity restrictions and follow-up appointments
• Encourage lifestyle modifications and stress reduction techniques (deep breathing, progressive muscle relaxation)
• Discuss the importance of regular follow-up appointments to monitor arrhythmia control and adjust treatment as needed