What is the initial workup for a patient presenting with an irregular heartbeat?

Initial Workup for Irregular Heartbeat

The initial workup for a patient presenting with an irregular heartbeat should begin with a 12-lead ECG recording during the arrhythmia, which is essential for accurate diagnosis and guides subsequent management decisions. 1

Diagnostic Approach

Step 1: Initial Assessment

• A thorough medical history focusing on symptom pattern (onset, duration, frequency, triggers), associated symptoms (syncope, dyspnea, chest pain), and risk factors for arrhythmias should be obtained 1
• Physical examination may reveal irregular pulse, irregular jugular venous pulsations, and variation in the intensity of the first heart sound 1
• An irregular pulse should always raise suspicion of atrial fibrillation (AF), but an ECG recording is necessary for definitive diagnosis 1

Step 2: 12-Lead ECG

• A 12-lead ECG is the cornerstone of initial evaluation and should be performed during the arrhythmia if possible 1
• The ECG helps differentiate between:
  • Atrial fibrillation (characterized by "absolutely" irregular RR intervals, absence of distinct P waves, and variable atrial cycle length <200 ms) 1
  • Atrial flutter or atrial tachycardia (usually with longer atrial cycle lengths ≥200 ms) 1
  • Supraventricular tachycardia (SVT) with regular rhythm 1
  • Ventricular tachycardia (VT) versus SVT with aberrancy (wide QRS complexes) 1
  • Premature ventricular or atrial contractions 1

Step 3: Additional Initial Testing

• Echocardiography should be performed to assess for structural heart disease, valvular abnormalities, and cardiac function 1
• Laboratory tests should include:
  • Thyroid function tests (TSH) 1
  • Complete blood count 1
  • Serum electrolytes 1
  • Renal function (serum creatinine) 1
  • Blood glucose to screen for diabetes 1
  • Consider liver function tests in selected patients 1

Step 4: Extended Monitoring (if arrhythmia is not captured on initial ECG)

• For frequent episodes (several per week): 24-hour Holter monitoring 1
• For less frequent episodes: Event recorder or wearable loop recorder 1
• For rare but severe symptomatic episodes: Consider implantable loop recorder 1

Special Considerations

Wide Complex Tachycardias

• When a wide-complex tachycardia (QRS >120 ms) is detected, careful analysis is needed to distinguish VT from SVT with aberrant conduction 1
• The presence of AV dissociation or fusion complexes is diagnostic of VT 1
• ECG algorithms such as Brugada criteria or Vereckei algorithm may help differentiate VT from SVT 1

Specific Arrhythmia Patterns

• Regular SVTs with 1:1 AV relationship may represent AVNRT or AVRT and require careful analysis of P wave location relative to the QRS complex 1
• Irregular ventricular response suggests AF, multifocal atrial tachycardia, or atrial flutter with variable AV conduction 1
• When AF is associated with rapid ventricular response, the irregularity may be less obvious and can be misdiagnosed as regular SVT 1

Common Pitfalls to Avoid

• Failing to obtain an ECG during symptoms - encourage patients to seek medical attention when experiencing palpitations 1
• Misdiagnosing VT as SVT with aberrancy, which can lead to inappropriate treatment 1
• Not considering AF in patients with stroke or TIA - AF may manifest initially as an ischemic stroke 1
• Overlooking potentially reversible causes of arrhythmias such as hyperthyroidism, electrolyte abnormalities, or medication effects 1
• Not considering pre-excitation syndromes (WPW) in patients with palpitations, which may require referral to an electrophysiologist 1

When to Consider Referral to a Specialist

• Presence of a wide complex tachycardia of unknown origin 1
• Patients with drug-resistant or drug-intolerant narrow complex tachycardias 1
• All patients with pre-excitation (WPW syndrome) 1
• Patients with severe symptoms such as syncope or dyspnea during palpitations 1