What is the appropriate evaluation and treatment for a patient experiencing palpitations, considering potential underlying conditions such as hyperthyroidism, anemia, or cardiovascular disease?

Evaluation and Management of Palpitations

Initial Diagnostic Approach

Obtain a 12-lead ECG immediately to identify the rhythm, look for pre-excitation patterns, and determine if the tachycardia is regular or irregular, as this distinction fundamentally changes the entire diagnostic approach. 1

Critical History Elements

• Pattern characterization: Document onset and termination (sudden vs gradual), duration, frequency, and response to vagal maneuvers 1
• Associated symptoms: Specifically ask about syncope, presyncope, chest discomfort, dyspnea, or polyuria (occurs in ~15% of SVT patients) 1
• Precipitating factors: Identify triggers including exercise, emotional stress, caffeine, alcohol, nicotine, medications, or recreational drugs 1, 2
• Medication review: Screen for QT-prolonging drugs, stimulants (including cocaine and amphetamines), supplements, and over-the-counter medications 2

Physical Examination Priorities

• During tachycardia: Look for irregular cannon A waves and irregular variation in S1 intensity, which strongly suggests ventricular origin 1
• Cardiovascular assessment: Evaluate heart rate regularity, blood pressure, jugular venous pressure, murmurs, and signs of heart failure 2

ECG Interpretation and Immediate Actions

Pre-excitation Patterns

• Pre-excitation with regular palpitations: Suggests AVRT and requires immediate electrophysiology referral 1
• Pre-excitation with irregular palpitations: Strongly suggests atrial fibrillation with accessory pathway—this requires immediate electrophysiological evaluation due to risk of sudden death 1

Rhythm Classification

• Regular rhythm with sudden onset/offset: Most commonly indicates AVNRT or AVRT, particularly in younger patients 1, 2
• Regular rhythm with gradual onset/termination: Suggests sinus tachycardia triggered by infection, volume loss, caffeine, or medications 1
• Irregular rhythm: Consider atrial fibrillation, multifocal atrial tachycardia, or frequent premature contractions 1, 2
• Wide complex tachycardia: May represent VT or SVT with aberrancy; look for AV dissociation or fusion complexes diagnostic of VT 1

Mandatory Laboratory Testing

Obtain thyroid function tests for first episode of AF, when ventricular rate is difficult to control, or when AF recurs unexpectedly after cardioversion. 2 Thyroid disease is a common non-cardiac cause that must be excluded in all patients with palpitations. 1

Ambulatory Monitoring Strategy

For Daily Palpitations

• 24-48 hour Holter monitoring is appropriate when symptoms occur daily 1

For Less Frequent Palpitations

• Event or loop recorders have superior diagnostic yield and are more cost-effective for symptoms occurring several times per week 1
• Implantable loop recorder: Consider if symptoms occur less than twice monthly and are associated with severe symptoms or hemodynamic instability 1

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

Echocardiography Indications

Order echocardiography when: 1

• Documented sustained SVT is present (to exclude structural heart disease)
• Clinical suspicion exists for valvular aortic stenosis, hypertrophic cardiomyopathy, or tachycardia-mediated cardiomyopathy
• Physical examination suggests structural abnormalities

Immediate Specialist Referral Criteria

Refer immediately to cardiac electrophysiology for: 1

• All patients with Wolff-Parkinson-White syndrome (due to potential for lethal arrhythmias)
• Severe symptoms during palpitations (syncope or dyspnea)
• Wide complex tachycardia of unknown origin documented on any rhythm strip
• Narrow complex tachycardia with drug resistance or intolerance
• Patients desiring to be free of drug therapy 2

Empiric Medical Therapy

A beta-blocker may be prescribed empirically while awaiting monitoring results, but only after excluding significant bradycardia (<50 bpm). 1 Patients should be taught vagal maneuvers (Valsalva, carotid massage) to perform during episodes. 1

Critical Pitfalls to Avoid

• Never start Class I or III antiarrhythmic drugs without documented arrhythmia due to significant proarrhythmic risk 1
• Do not rely on automatic ECG analysis systems, as they are unreliable and commonly suggest incorrect diagnoses 1
• Do not dismiss syncope occurring with palpitations—this indicates potential hemodynamic significance requiring urgent evaluation 1, 2
• Do not order comprehensive laboratory panels routinely—targeted testing based on clinical suspicion is more appropriate 1

Underlying Conditions to Exclude

Cardiac Causes

• Structural heart disease: Valvular disease, hypertrophic cardiomyopathy, congestive heart failure 2
• Ischemic heart disease: Consider stress testing if palpitations are clearly triggered by exertion 1
• Tachycardia-mediated cardiomyopathy: Can occur when SVT persists for weeks to months with fast ventricular response 1

Non-Cardiac Causes

• Hyperthyroidism: Mandatory screening with thyroid function tests 2, 1
• Anemia: Creates increased myocardial oxygen demand and can precipitate functional angina 2
• Medications and substances: Stimulants, QT-prolonging drugs, alcohol 2, 1
• Dehydration: Leading to compensatory tachycardia 1

Special Populations

Hypertrophic Cardiomyopathy

Patients require 24-48 hour ambulatory monitoring every 1-2 years as part of periodic follow-up, with extended monitoring if additional AF risk factors are present (left atrial dilatation, advanced age, NYHA class III-IV). 1