Cardiac Arrhythmias

Arrhythmias (cardiac arrhythmias (HRS) (synonyms: abnormal heart rhythm; arrhythmia; arrhythmia cordis; arrhythmia; cardiac arrhythmia; cardiac stutter; irregular heart action; cardiac arrhythmia; arrhythmia of the heart; ICD-10-GM I49.9: Cardiac arrhythmia, unspecified) are changes in the normal sequence of the heartbeat. The normal sequence of action of the heart is due to rhythmic stimulation in the sinus node. This also necessitates normal conduction of excitation or conduction of stimulation. The normal heart action is regular with a pulse rate of 60-80 beats per minute (see “Pulse measurement” below). Cardiac arrhythmias are very common (almost everyone has cardiac arrhythmias at some time in their life) and have very different effects. Many types of cardiac arrhythmias are harmless. The most common type of arrhythmia is atrial fibrillation (VHF), which affects approximately 1,800,000 people in Germany. Cardiac arrhythmias are subdivided according to:

• Cause of disturbance:
  • Stimulation disorders (see “Classification” below).
  • Conduction disorders (see “Classification” below).
• Localization:
  • Supraventricular arrhythmias: Disorders originate from the atrium (see “Classification” below).
  • Ventricular arrhythmias: Disorders emanate from the cardiac ventricle (see “Classification” below).
• Heart rate/pulse rhythm:
  • Pulsus regularis (regular pulse).
    • Bradycardia (pl. bradycardia): < 60 beats per minute (bpm); bradycardic arrhythmias are:
      • Bradyarrhythmia absoluta (BAA; irregular pulse with heart rate less than 60 beats per minute).
      • Higher-grade, sinuatrial and atrioventricular blocks.
      • Carotid sinus syndrome (synonyms: hypersensitive carotid sinus syndrome (HCSS), hypersensitive carotid sinus syndrome).
      • If necessary, the sinus node syndrome in the sense of a bradycardia–tachycardia syndrome.
    • Tachycardia (pl. Tachycardias): > 100 beats/min; tachycardic arrhythmias are:
      • Supraventricular tachycardias.
      • Tachysystolic atrial fibrillation and atrial flutter
      • Ventricular extrasystoles (e.g., in acute myocardial infarction “warning arrhythmias”).
      • Ventricular tachycardia: (life-threatening) ventricular flutter and ventricular fibrillation.
  • Extrasystoles – extra beats with a regular basic rhythm.
    • In unspecified heart disease or digitalis intoxication (poisoning with a drug used for heart failure (cardiac insufficiency)).
  • Pulsus irregularis (arrhythmia) – can be divided into:
    • Respiratory arrhythmia – physiological increase in frequency during inspiration, it decreases again during expiration; normal finding, most pronounced in children and adolescents.
    • absolute arrhythmia (Arrhythmia absoluta) – cardiac arrhythmia, with complete irregularity of the pulse without dependence on respiration; occurs, for example, atrial fibrillation (VHF): depending on the pulse rate, this is divided into:
      • Bradyarrhythmia absoluta (BAA; pulse less than 60 beats per minute).
      • Normal-frequency absolute arrhythmia (pulse 60 to 100 beats per minute).
      • Tachyarrhythmia absoluta (TAA)

Causes of cardiac arrhythmias are:

• Congenital (cardiac vitias (congenital heart defects); accessory (supernumerary) pathways (WPW syndrome, AVNRT); ion channel disorders (Brugada syndrome, congenital long QT syndrome, LQTS); cardiomyopathies (heart muscle diseases).
• Acquired
  • Myocardial damage (heart muscle damage): e.g., after myocardial infarction (heart attack), hypertensive heart disease/hypertension (high blood pressure); myocarditis (heart muscle inflammation), pericarditis (pericardial inflammation); dilated cardiomyopathy (heart muscle disease).
  • Acute/chronic volume/pressure stress (hypertension, pulmonary embolism).
• Other (extracardiac) causes: e.g., hyperthyroidism (hyperthyroidism), electrolyte disturbances (potassium, magnesium, calcium), hypoxia, holiday heart syndrome (dysrhythmia triggered by alcohol), psychovegetative (anxiety, stress, fatigue), Roemheld syndrome (reflex cardiac symptoms caused by gas accumulation in the intestine and stomach), medications (see below “Cardiac dysrhythmia caused by medications”).

Automation centers are:

• Sinus node 60-80/min
• AV node 40-60/min
• Ventricular myocardium 20-40/min

A heterotopic (= ectopic) pacing disorder is said to occur when premature pacing occurs outside the sinus node (primary/active arrhythmia) (see classification below). If a cardiac arrhythmia shows a narrow ventricular complex (QRS width ≤ 120 ms) in the ECG (electrocardiogram), this is called narrow complex tachycardia. In this case, the ventricles (heart chambers) are excited antegrade (“directed forward”) via the AV node and His bundle, without intraventricular conduction delay (thigh block). These include the following cardiac arrhythmias:

• Sinus tachycardia
• Supraventricular tachycardia
• Atrial flutter
• Atrial fibrillation
• AV nodal re-entrant tachycardia

When a cardiac arrhythmia exhibits a wide ventricular complex (QRS width ≥ 120 ms) on the ECG (electrocardiogram), it is referred to as wide complex tachycardia. These include:

• Ventricular tachycardia (VT) Always assume VT sooner in an emergency. Notice: 12-lead ECG can never reliably distinguish VT from supraventricular tachycardia (SVT) in the presence of preexcitation or aberration.
• Right bundle branch block (RSB)
• Left thigh block (LSB)

Even heart-healthy individuals can develop cardiac arrhythmias for a variety of reasons (e.g., due to older age, caffeine consumption, alcohol consumption, drugs, physical exertion; stress). Cardiac arrhythmias can be a symptom of many diseases (see under “Differential diagnoses”). Course and prognosis: The course and prognosis of cardiac arrhythmias depend on the cause (see the individual cardiac arrhythmias under “Introduction”).