What is the approach to differential diagnosis, diagnostics, and management of palpitations?

Palpitations: Differential Diagnosis, Diagnostics, and Management

Differential Diagnosis

The differential diagnosis of palpitations fundamentally depends on whether the rhythm is regular or irregular, as this distinction changes the entire diagnostic approach. 1

Regular Palpitations

• Paroxysmal supraventricular tachycardia (PSVT) with sudden onset and termination most commonly indicates AVNRT or AVRT, particularly in younger patients 1, 2
• Sinus tachycardia accelerates and terminates gradually (non-paroxysmal), often triggered by stressors like infection, volume loss, caffeine, nicotine, or medications 1
• Ventricular tachycardia presents with sudden onset/offset and may be associated with presyncope or syncope 1
• Atrial flutter with regular ventricular response 1

Irregular Palpitations

• Premature depolarizations (atrial or ventricular) described as pauses followed by strong heartbeats 1
• Atrial fibrillation 1
• Multifocal atrial tachycardia, most common in patients with pulmonary disease 1

High-Risk Arrhythmias Requiring Immediate Recognition

• Wolff-Parkinson-White syndrome (pre-excitation with arrhythmias) carries potential for lethal arrhythmias 1, 2
• Wide complex tachycardia of unknown origin 1, 2
• Inherited arrhythmia syndromes including long QT syndrome, Brugada syndrome, CPVT, and subtle cardiomyopathies 1

Diagnostic Approach

Initial Evaluation (All Patients)

Obtain a 12-lead ECG immediately to identify the rhythm, look for pre-excitation, and determine if the tachycardia is regular or irregular. 2 This single test guides all subsequent management and risk stratification.

Critical History Elements

• Pattern characterization: number of episodes, duration, frequency, mode of onset, and triggers 1, 2
• Regular vs irregular: This is the most important distinction 1, 2
• Sudden onset/termination suggests AVNRT or AVRT 1
• Response to vagal maneuvers: termination suggests re-entrant tachycardia involving AV nodal tissue 1, 2
• Associated symptoms: syncope (occurs in ~15% of SVT patients), presyncope, chest discomfort, dyspnea, or polyuria 1
• Precipitating factors: caffeine, alcohol, nicotine, recreational drugs, exercise 1
• Family history: sudden cardiac death, inherited heart disease, or premature deaths are red flags 1

Physical Examination During Tachycardia

• Look for irregular cannon A waves and irregular variation in S1 intensity, though physical exam rarely leads to definitive diagnosis 1
• Assess for hemodynamic instability requiring immediate intervention 1

Laboratory Testing

Order targeted blood tests based on clinical assessment rather than comprehensive routine panels, as extensive laboratory testing has been shown to be not useful. 3

Selective Laboratory Tests (Based on Clinical Suspicion)

• Thyroid-stimulating hormone to rule out hyperthyroidism 3
• Complete blood count to assess for anemia 3
• Serum electrolytes including calcium and magnesium to identify disturbances triggering arrhythmias 3
• Fasting blood glucose or glycohemoglobin to identify hypoglycemia or diabetes 3
• BNP and high-sensitivity troponin may be considered if cardiac cause is suspected, though usefulness is uncertain 3

Cardiac Monitoring Strategy

The choice of monitoring depends entirely on symptom frequency:

Frequent Symptoms (Several Episodes Per Week)

• 24-48 hour Holter monitor is appropriate for frequent or sustained palpitations 1, 3, 2

Infrequent Symptoms (Less Than Weekly)

• Event recorder or external loop recorder is more useful than 24-hour recording 1, 3
• Patch recorders or mobile cardiac outpatient telemetry for sporadic episodes 3

Rare Symptoms (Fewer Than Two Episodes Per Month)

• Implantable loop recorder for recurrent unexplained palpitations with severe symptoms or hemodynamic instability 1, 3

Additional Diagnostic Testing

Echocardiography

• Obtain echocardiography in all patients with documented sustained SVT to exclude structural heart disease 1
• Consider if there is clinical suspicion of structural abnormalities, valvular disease, or cardiomyopathy 1, 3

Exercise Stress Testing

• Indicated when arrhythmia is clearly triggered by exertion 1
• Useful for palpitations during or after exercise 3

Electrophysiological Study

• Indicated in patients with ischemic heart disease when initial evaluation suggests arrhythmic cause 1
• Should be considered in patients with bundle branch block when non-invasive tests fail 1
• May be performed in patients with syncope preceded by sudden brief palpitations when other tests fail 1
• Not recommended in patients with normal ECG, no heart disease, and no palpitations 1

Management

Immediate Management Based on Clinical Presentation

Hemodynamically Unstable Patients

• Obtain at minimum a monitor strip before DC cardioversion 1
• Do not delay immediate therapy to obtain 12-lead ECG if there is hemodynamic instability 1

Stable Patients Without ECG Documentation

If surface ECG is normal and history suggests premature extra beats:

• Review and eliminate precipitating factors: excessive caffeine, alcohol, nicotine, recreational drugs 1
• Screen for hyperthyroidism 1
• Reassure that benign extrasystoles are often manifest at rest and decrease with exercise 1

If symptoms indicate paroxysmal arrhythmia and resting ECG gives no clue:

• Teach vagal maneuvers 1
• Beta-blocker may be prescribed empirically provided significant bradycardia (<50 bpm) has been excluded 1
• Do NOT initiate class I or class III antiarrhythmic drugs without documented arrhythmia due to proarrhythmia risk 1

Indications for Specialist Referral

Refer immediately for the following:

• All patients with Wolff-Parkinson-White syndrome due to potential for lethal arrhythmias 1, 2
• Wide complex tachycardia of unknown origin 1, 2
• Severe symptoms during palpitations including syncope or dyspnea 1
• Drug resistance or intolerance in narrow complex tachycardias 1
• Patients desiring to be free of drug therapy 1

Special Considerations

Tachycardia-Mediated Cardiomyopathy

• SVT that persists for weeks to months with fast ventricular response can lead to cardiomyopathy 1, 2
• This emphasizes the importance of timely diagnosis and treatment

Family Screening

• First-degree relatives of sudden death victims should undergo cardiac evaluation when autopsy is unavailable or normal 1
• Up to 50% of families with sudden arrhythmic death syndrome have an inheritable disorder 1
• Screening should include personal/family history, 12-lead ECG with high precordial leads, 24-hour ambulatory ECG, exercise stress test, and echocardiography or cardiac MRI 1

Common Pitfalls to Avoid

• Never start class I or III antiarrhythmics empirically without documented arrhythmia 1
• Do not order comprehensive laboratory panels routinely as they are not useful 3
• Do not use ATP testing to select patients for pacing due to lack of correlation with spontaneous syncope 1
• Do not dismiss syncope with palpitations as it occurs in 15% of SVT patients and may indicate rapid rates or structural disease 1, 2