I experience brief, seconds‑long palpitations; what are the likely causes and appropriate diagnostic work‑up?

Brief Palpitations Lasting Seconds: Causes and Diagnostic Approach

For brief palpitations lasting only seconds, the most likely causes are premature atrial contractions (PACs) or premature ventricular contractions (PVCs), both of which are extremely common and typically benign in patients without structural heart disease. 1, 2

Most Likely Causes

Premature atrial contractions (PACs) occur in nearly all individuals and commonly present as brief "skipped beats" or extra beats lasting just seconds. 1, 2 These are often completely benign, particularly in the absence of structural heart disease. 3, 1

Premature ventricular contractions (PVCs) are similarly common, occurring in more than two-thirds of the population, and typically manifest as brief palpitations or a sensation of the heart "skipping." 2, 4 In patients with normal hearts, PVCs carry a benign prognosis. 4

Sinus tachycardia triggered by stressors (caffeine, nicotine, infection, volume loss, emotional stress) accelerates and terminates gradually rather than abruptly, but brief episodes can occur. 1

Critical Distinction: What Brief Duration Rules Out

The seconds-long duration makes sustained arrhythmias highly unlikely. Paroxysmal supraventricular tachycardia (PSVT) typically lasts minutes to hours with sudden onset and termination, not seconds. 1, 5 Similarly, atrial fibrillation episodes and ventricular tachycardia persist longer than a few seconds. 1

Essential Initial Workup

Obtain a 12-lead ECG immediately to identify baseline rhythm, look for pre-excitation patterns (Wolff-Parkinson-White syndrome), assess for conduction abnormalities, and detect any structural clues. 1, 5

Order baseline laboratory tests including:

• Thyroid function tests (TSH) to exclude hyperthyroidism, a common non-cardiac cause 1, 6
• Serum electrolytes, particularly potassium, which affects arrhythmia risk 1
• Complete blood count 1
• Renal function (creatinine, GFR) 1

Perform a focused history documenting:

• Frequency and total number of episodes to guide monitoring strategy 1
• Precipitants: alcohol, caffeine, sleep deprivation, emotional stress, exercise, large meals 1
• Associated symptoms: syncope, presyncope, chest pain, dyspnea, or polyuria (occurs in ~15% of SVT patients) 1, 5
• Medication and substance use: stimulants, over-the-counter medications, recreational drugs 1, 6

Physical examination should assess for:

• Irregular peripheral pulse and jugular venous pulsations suggesting atrial fibrillation 1
• Variability in first heart sound intensity 1
• Signs of structural heart disease, valvular disease, or heart failure 1

Ambulatory Monitoring Strategy

For daily palpitations: Use 24-48 hour Holter monitoring. 1

For symptoms occurring several times per week: Event recorders have superior diagnostic yield and are more cost-effective than Holter monitoring. 1, 6

For infrequent symptoms (less than twice monthly) with severe features: Consider an implantable loop recorder. 1

Critical principle: Monitoring must continue until symptoms occur while wearing the device—non-diagnostic monitoring should not be considered conclusive. 1

When to Escalate Urgently

Immediate evaluation is mandatory if:

• Syncope or presyncope accompanies palpitations 1
• Chest pain or dyspnea occurs with episodes 1
• Wide-complex tachycardia is documented on any rhythm strip 1
• Pre-excitation pattern (Wolff-Parkinson-White) is present on ECG with history of paroxysmal palpitations 1, 5
• Palpitations occur with exertion in patients with known structural heart disease (hypertrophic cardiomyopathy, aortic stenosis) 1

Echocardiography Indications

Order echocardiography when:

• Sustained SVT is documented, to exclude structural heart disease that cannot be detected by physical examination alone 1
• Clinical suspicion exists for valvular aortic stenosis, hypertrophic cardiomyopathy, or tachycardia-mediated cardiomyopathy 1

Empiric Medical Therapy

A beta-blocker may be prescribed empirically while awaiting monitoring results, but only after excluding significant bradycardia (<50 bpm). 1, 2 This can provide symptomatic relief for PACs or PVCs. 2

Never start Class I or III antiarrhythmic drugs without documented arrhythmia due to significant proarrhythmic risk. 1

Common Pitfalls to Avoid

• Do not rely on automatic ECG analysis systems—they are unreliable and commonly suggest incorrect diagnoses; always perform manual interpretation. 1, 5
• Do not dismiss brief palpitations in patients with structural heart disease—even short episodes warrant thorough evaluation. 1
• Do not order comprehensive laboratory panels routinely—focus on thyroid function, electrolytes, and renal function. 1
• Do not assume all brief palpitations are benign—correlation with symptoms during monitoring is essential. 1, 7

Special Populations

In athletes: First-degree AV block or Mobitz type I block that resolves during exercise requires no therapy if asymptomatic and without structural heart disease. 3, 1 However, Mobitz type II or third-degree AV block warrants comprehensive evaluation and possible pacemaker implantation. 3, 1