What diagnostic tests should be done for a patient presenting with palpitations and syncope?

Diagnostic Testing for Palpitations and Syncope

For a patient presenting with both palpitations and syncope, immediately obtain a detailed history, physical examination with orthostatic vital signs, and a 12-lead ECG—this triad is mandatory and establishes the diagnosis in 23-50% of cases while determining whether urgent cardiac evaluation or hospital admission is needed. 1

Mandatory Initial Tests (Perform on All Patients)

History Taking

• Document the exact position during syncope (supine suggests cardiac cause; standing suggests reflex or orthostatic) 1
• Assess activity at onset—exertional syncope is high-risk and mandates cardiac evaluation 1
• Determine if palpitations occurred before syncope, which strongly suggests an arrhythmic cause [1, @15@]
• Identify triggers: warm crowded places or prolonged standing suggest vasovagal; urination, defecation, or cough suggest situational syncope [@15@]
• Assess for warning symptoms: nausea, diaphoresis, blurred vision, and dizziness favor vasovagal syncope, while brief or absent prodrome suggests cardiac syncope [1, @15@]
• Obtain family history of sudden cardiac death or inherited arrhythmia syndromes 1
• Review all medications, particularly antihypertensives, diuretics, vasodilators, and QT-prolonging agents [@14@]

Physical Examination

• Measure orthostatic vital signs in lying, sitting, and standing positions—orthostatic hypotension is defined as systolic BP drop ≥20 mmHg or to <90 mmHg [@15@]
• Perform complete cardiovascular examination assessing for murmurs, gallops, rubs, and irregular rhythm 1
• Perform carotid sinus massage in patients >40 years (positive if asystole >3 seconds or systolic BP drop >50 mmHg), unless contraindicated by history of TIA or stroke [@15@, 2]

12-Lead ECG

• Assess for QT prolongation (long QT syndrome) [@15@]
• Look for conduction abnormalities including bundle branch blocks, bifascicular block, sinus bradycardia, or AV blocks [3, @15@]
• Identify Brugada pattern, pre-excitation (Wolff-Parkinson-White), or signs of ischemia/prior MI [@15@, 4]
• Check for ventricular hypertrophy patterns suggesting hypertrophic cardiomyopathy 4

Risk Stratification Determines Next Steps

High-Risk Features Requiring Hospital Admission and Urgent Cardiac Evaluation

• Age >60-65 years [1, @15@]
• Known structural heart disease or heart failure (95% sensitivity for cardiac syncope) [@14@]
• Syncope during exertion or in supine position 1
• Palpitations immediately before syncope [@15@]
• Brief or absent prodrome 1
• Abnormal cardiac examination or ECG [1, @15@]
• Family history of sudden cardiac death or inherited cardiac conditions 1

Low-Risk Features Suggesting Outpatient Management

• Age <45 years 1
• Syncope only when standing 1
• Clear prodromal symptoms (nausea, diaphoresis, blurred vision) 1
• Normal physical examination and ECG 1
• Specific situational triggers 1

Additional Testing Based on Initial Evaluation

For High-Risk Patients or Suspected Cardiac Syncope

Continuous Cardiac Telemetry Monitoring

• Initiate immediately for patients with abnormal ECG, palpitations before syncope, or high-risk features [@18@]
• Monitoring longer than 24 hours is not likely to increase yield for most patients [@18@]

Transthoracic Echocardiography

• Order immediately when structural heart disease is suspected based on abnormal cardiac examination, abnormal ECG, syncope during exertion, or family history of sudden cardiac death 1, 2
• Mandatory for evaluation of valvular disease, cardiomyopathy, or ventricular function [@15@]

Exercise Stress Testing

• Mandatory for syncope during or immediately after exertion to screen for hypertrophic cardiomyopathy, anomalous coronary arteries, and exercise-induced arrhythmias [2, @15@]

Prolonged ECG Monitoring

• Select monitoring device based on symptom frequency: 1
  • Holter monitor (24-48 hours) for daily symptoms
  • External loop recorder (30 days) for weekly symptoms
  • Implantable loop recorder for monthly or less frequent symptoms

Electrophysiological Study (EPS)

• Indicated in patients with ischemic heart disease when initial evaluation suggests arrhythmic cause 3
• Consider in patients with bundle branch block when non-invasive tests fail to make diagnosis 3
• May be performed in patients with syncope preceded by sudden brief palpitations when other tests are non-diagnostic 3

For Suspected Orthostatic Hypotension

Orthostatic Challenge Testing

• Perform lying-to-standing test (active standing) or tilt table testing 3
• Measure BP at 0-30 seconds (initial OH), 30 seconds-3 minutes (classical OH), and 3-30 minutes (delayed progressive OH) 3

Tilt-Table Testing

• Consider for recurrent unexplained syncope in young patients without heart disease when reflex mechanism is suspected [@15@]
• Can confirm vasovagal syncope when history is suggestive but not diagnostic [@14@]

Laboratory Testing (Targeted, Not Routine)

Do NOT order comprehensive laboratory panels without specific indications 1

Order targeted tests only when clinically indicated:

• Hemoglobin/hematocrit if volume depletion or blood loss suspected 1
• Electrolytes, BUN, creatinine if dehydration suspected 1
• BNP and high-sensitivity troponin if cardiac cause suspected (usefulness uncertain) 1
• Pregnancy test in women of childbearing age [@18@]

Tests NOT Recommended

Brain Imaging (CT/MRI)

• Not recommended routinely for syncope evaluation—diagnostic yield only 0.24% for MRI and 1% for CT 1
• Only order if focal neurological findings or head injury present 1

EEG

• Not recommended routinely—diagnostic yield only 0.7% 1
• Only order if seizure suspected based on prolonged unconsciousness (>1 minute), lateral tongue biting, or post-event confusion 2

Carotid Artery Imaging

• Not recommended routinely—diagnostic yield only 0.5% 1
• Do not order without focal neurological findings 1

ATP/Adenosine Testing

• Low predictive value—no correlation between ATP-induced AV block and spontaneous syncope documented by implantable loop recorder 3

Critical Pitfalls to Avoid

• Do not dismiss cardiac causes based on the presence of a situational trigger—palpitations before syncope mandate arrhythmic evaluation regardless of triggers 2
• Do not overlook medication effects, particularly in elderly patients on multiple vasoactive drugs [2, @14@]
• Do not order brain imaging, EEG, or carotid ultrasound without specific neurological indications 1
• Do not perform comprehensive laboratory testing without clinical suspicion 1
• Do not use tilt-table testing as a first-line diagnostic test due to high false-positive and false-negative rates 2