Cardiac Arrhythmias

(For atrial fibrillation, see here)

Definition/diagnostic criteria

Cardiac arrhythmias encompass a range of conditions characterised by abnormal electrical activity in the heart, leading to irregular heartbeats. The diagnosis of specific arrhythmias is based on the evaluation of the heart’s electrical activity through an ECG along with clinical assessment. Arrhythmias can be classified into bradyarrhythmias (slow heart rate), tachyarrhythmias (fast heart rate), and premature beats. The specific diagnostic criteria vary for each type but fundamentally rely on deviations from normal ECG findings and heart rate thresholds.

Epidemiology

The prevalence of cardiac arrhythmias in the UK is challenging to quantify. However, conditions such as supraventricular tachycardia (SVT), ventricular tachycardia, and bradyarrhythmias are significant contributors to the overall burden of cardiac arrhythmias. These conditions affect both genders and are seen across all age groups, but the incidence increases with age.

Diagnosis

Clinical Features

Symptoms may vary widely, ranging from palpitations, syncope, or dizziness to being completely asymptomatic, detected incidentally during routine examinations or presenting acutely in an emergency. The clinical presentation depends on the type of arrhythmia and its impact on cardiac output.

Investigations

1. ECG: The cornerstone for diagnosing arrhythmias, providing information on heart rhythm, rate, and electrical conduction patterns. Specific ECG findings associated with arrhythmias include premature beats, tachycardia or bradycardia with abnormal P wave morphology, QRS complex abnormalities, and alterations in the PR or QT interval.
2. Ambulatory ECG monitoring (Holter monitoring): Used for patients with intermittent symptoms to capture arrhythmias occurring outside the clinical setting.
3. Exercise stress testing: Helps in diagnosing arrhythmias induced by physical activity.
4. Electrophysiological study: Invasive test performed to identify precise mechanisms and origins of arrhythmias, especially when intervention procedures like catheter ablation are considered.

Treatment

Management strategies for cardiac arrhythmias vary based on the type, severity, and symptoms. Treatment options include:

• Pharmacological therapy: Antiarrhythmic drugs are selected based on the type of arrhythmia, with considerations for side effects and patient-specific factors. Common choices include beta-blockers, calcium channel blockers, and specific antiarrhythmics like amiodarone or sotalol.
• Electrical cardioversion: Used in certain cases of tachyarrhythmias to restore normal rhythm.
• Pacemaker or implantable cardioverter-defibrillator (ICD): For significant bradyarrhythmias or to prevent sudden cardiac death in high-risk patients.
• Catheter ablation: A minimally invasive procedure aimed at destroying the abnormal heart tissue causing the arrhythmia.

Prognosis

The prognosis of cardiac arrhythmias varies significantly, depending on the type and severity of the arrhythmia, underlying heart condition, and effectiveness of treatment. While some arrhythmias may be benign, others, especially those associated with structural heart disease, can increase the risk of stroke, heart failure, or sudden cardiac death. Timely diagnosis and appropriate management are crucial for improving outcomes.