What causes tachycardia?

Causes of Tachycardia

Tachycardia results from physiological responses to systemic stressors, pathological cardiac conditions, exogenous substances, or intrinsic cardiac electrical abnormalities that must be systematically identified and addressed. 1

Physiological and Pathological Triggers

Common Reversible Causes

The most frequent causes of physiological sinus tachycardia include:

• Infection with fever – inflammatory mediators and increased metabolic demands drive heart rate elevation 2, 1
• Dehydration – reduced intravascular volume triggers compensatory tachycardia 2, 1
• Anemia – decreased oxygen-carrying capacity necessitates increased cardiac output 2, 1
• Heart failure – compensatory sympathetic activation attempts to maintain cardiac output 2, 1
• Hyperthyroidism – excess thyroid hormone directly increases sinus node automaticity 2, 1
• Pain – sympathetic nervous system activation produces tachycardia 1

Exogenous Substances

Multiple substances directly stimulate cardiac rate:

• Caffeine – though epidemiologic studies show no connection between caffeine consumption and arrhythmia development in most patients 3, it remains a commonly cited trigger
• Illicit stimulants (amphetamines, cocaine, cannabis) – directly activate sympathetic pathways 2, 1
• Beta-agonist medications (albuterol, salmeterol) – stimulate cardiac beta-receptors 2, 1
• Other medications – aminophylline, atropine, catecholamines 1
• Alcohol – moderate to heavy use associates with atrial fibrillation development, particularly with binge consumption ("holiday heart") 3
• Energy drinks – loaded with caffeine, sugar, and stimulant chemicals; case reports describe arrhythmias and sudden death, particularly with exercise 3
• Anticancer treatments – particularly anthracycline compounds 1

Critical pitfall: Do not routinely advise patients with arrhythmias to eliminate caffeine, as literature does not support this restriction for standard coffee or tea consumption 3. However, strongly recommend limiting or avoiding energy drinks 3.

Intrinsic Cardiac Electrical Abnormalities

Inappropriate Sinus Tachycardia (IST)

IST is a diagnosis of exclusion characterized by:

• Unexplained resting heart rate >100 bpm and average 24-hour rate >90 bpm 2, 1
• Associated debilitating symptoms: weakness, fatigue, lightheadedness, uncomfortable heart racing sensations 2
• Proposed mechanisms: dysautonomia, neurohormonal dysregulation, intrinsic sinus node hyperactivity 2, 1
• Predominantly affects females (90%) with mean age 38 years 4

Essential distinction: IST must be differentiated from postural orthostatic tachycardia syndrome (POTS), as treatment to suppress sinus rate may cause severe orthostatic hypotension in POTS patients 2, 4. POTS patients have predominant symptoms with postural change and rapid heart rate increase >30 bpm within 10 minutes of standing 5.

Supraventricular Tachycardias

Reentrant mechanisms produce:

• Atrioventricular nodal re-entrant tachycardia 1, 6
• Atrioventricular re-entrant tachycardia 1, 6
• Atrial tachycardia 1
• Atrial flutter 1
• Sinus node reentry tachycardia 2, 1

These arrhythmias typically occur without structurally abnormal hearts 6.

Neurological and Autonomic Factors

• Anxiety disorders – important trigger often associated with IST; patients may have co-existing anxiety requiring treatment 2, 4
• Autonomic dysfunction – can precipitate tachyarrhythmias 1
• Emotional stress – common cause requiring behavioral interventions 4

Diagnostic pitfall: Diagnosis is often delayed due to misdiagnosis as anxiety or panic disorder 6. Patient history is crucial, and Holter monitoring or event recorders are usually necessary to capture the arrhythmia 6.

Metabolic and Electrolyte Disturbances

• Acid-base disturbances – alter cardiac electrophysiology 1
• Electrolyte abnormalities – particularly when accompanied by ST depression 4

Structural Heart Disease

• Cardiomyopathies – can cause both supraventricular and ventricular tachycardias 1

Systematic Diagnostic Approach

When evaluating tachycardia, the American Heart Association recommends:

1. Distinguish supraventricular from ventricular origins 1
2. Identify regular versus irregular rhythm 1
3. Determine narrow versus wide QRS complex 1
4. Evaluate for underlying structural heart disease 1
5. Rule out secondary causes: hyperthyroidism, anemia, dehydration 2, 1

The American Heart Association mandates evaluation for and treatment of reversible causes as a Class I recommendation in all patients with suspected IST 2, emphasizing that correcting underlying pathology resolves tachycardia in physiological cases 2.