What is the diagnostic approach for a patient presenting with palpitations?

Diagnostic Approach to Palpitations

All patients presenting with palpitations require an immediate 12-lead ECG and a detailed history focusing on whether the rhythm is regular versus irregular, as this single distinction fundamentally determines the entire diagnostic pathway. 1, 2

Initial Clinical Assessment

Critical History Elements

The pattern characterization is crucial and must include: 3, 1

• Onset and termination: Sudden onset/offset with abrupt termination suggests AVNRT or AVRT, while gradual acceleration/deceleration indicates sinus tachycardia 1
• Duration and frequency of episodes 2
• Response to vagal maneuvers: Termination with Valsalva or carotid massage strongly suggests re-entrant tachycardia involving AV nodal tissue 1
• Precipitating factors: Stressors like infection, volume loss, caffeine, nicotine, or medications suggest sinus tachycardia 1
• Associated symptoms: Syncope (occurs in ~15% of SVT patients), presyncope, chest discomfort, dyspnea, or polyuria (from atrial natriuretic peptide release) 3, 1

Physical Examination Findings

Look specifically for: 3

• Irregular cannon A waves and irregular variation in S1 intensity during tachycardia (strongly suggests ventricular origin)
• Signs of structural heart disease or thyroid dysfunction 2

Immediate ECG Interpretation

The resting 12-lead ECG determines the next steps: 3, 2

• Pre-excitation present + history of paroxysmal regular palpitations: Presumptive diagnosis of AVRT; refer immediately to electrophysiology without further documentation attempts 3, 2
• Pre-excitation + irregular palpitations: Strongly suggests atrial fibrillation with accessory pathway; requires immediate electrophysiological evaluation due to risk of sudden death 3
• Wide complex tachycardia of unknown origin: Immediate specialist referral 1

Targeted Laboratory Testing

Avoid routine comprehensive laboratory panels—they are not useful and should not be ordered. 4 Instead, order tests based only on clinical suspicion: 4, 2

• Complete blood count: Only if anemia suspected 4
• Thyroid-stimulating hormone: Only if hyperthyroidism suspected 4
• Serum electrolytes (including calcium and magnesium): Only if electrolyte disturbance suspected 4
• Fasting glucose or HbA1c: Only if hypoglycemia or diabetes suspected 4
• BNP and high-sensitivity troponin: May be considered if cardiac cause suspected, though usefulness is uncertain 4

Cardiac Monitoring Strategy

The frequency of symptoms dictates monitoring choice: 4, 2

• Frequent/daily episodes: 24-48 hour Holter monitor 4, 2
• Weekly episodes: Event recorder, patch recorder, or mobile cardiac outpatient telemetry 4, 2
• Monthly or rare episodes: Implantable loop recorder 4, 2

For patients with frequent or sustained palpitations, 48-hour ambulatory ECG monitoring is recommended to identify the likely cause. 4, 2

Echocardiography Indications

Order echocardiography when: 3, 2

• Documented sustained SVT to exclude structural heart disease (which usually cannot be detected by physical examination alone) 3
• Clinical suspicion of structural abnormalities like valvular aortic stenosis, hypertrophic cardiomyopathy, or tachycardia-mediated cardiomyopathy 3, 2

Exercise Testing

Perform exercise stress testing only when palpitations are specifically triggered by exertion. 2

Mandatory Specialist Referral Criteria

Refer immediately to cardiac electrophysiology for: 3, 1, 2

• All patients with Wolff-Parkinson-White syndrome (pre-excitation + arrhythmias) due to potential for lethal arrhythmias 3, 1
• Wide complex tachycardia of unknown origin 1
• Severe symptoms during palpitations (syncope, dyspnea) 3, 1
• Narrow complex tachycardia with drug resistance or intolerance 3, 1
• Patients desiring to be free of drug therapy 1

Critical Pitfalls to Avoid

• Never start class I or III antiarrhythmics empirically without documented arrhythmia 1
• Never dismiss syncope occurring with palpitations—this requires immediate evaluation 1
• Do not order comprehensive laboratory panels routinely 4
• Do not rely on automatic ECG analysis systems—they are unreliable and commonly suggest incorrect diagnoses 3

Special Clinical Scenarios

Tachycardia-mediated cardiomyopathy can develop when SVT persists for weeks to months with fast ventricular response, emphasizing the critical importance of timely diagnosis and treatment. 1