What is the appropriate evaluation and management for a patient presenting with an intermittent split S2 (second heart sound)?

Evaluation and Management of Intermittent Split S2

An intermittent split S2 that varies with respiration is physiologically normal and requires no intervention, but you must perform a focused respiratory variation assessment and obtain echocardiography to exclude pathologic splitting patterns (fixed or reversed) that indicate serious underlying structural heart disease. 1, 2

Initial Bedside Assessment

Respiratory Variation Testing

• Listen at the pulmonic area (left upper sternal border) during normal breathing, then have the patient breathe deeply to accentuate the splitting 1, 3
• Normal (physiologic) splitting: S2 splits during inspiration and becomes single during expiration—this is benign and requires no further workup 3
• Fixed splitting: constant split interval throughout both inspiration and expiration without respiratory variation—this indicates right ventricular volume overload, classically from atrial septal defect 1, 3
• Reverse (paradoxical) splitting: S2 splits during expiration and becomes single during inspiration—this indicates delayed left ventricular systole from severe aortic stenosis, left bundle branch block, or other structural disease 1, 3

Critical Physical Examination Findings

• Assess carotid pulse character: a delayed, dampened upstroke (pulsus parvus et tardus) suggests severe aortic stenosis 1, 2
• Palpate for right ventricular lift at the left sternal border, which indicates right ventricular volume or pressure overload 1
• Listen for systolic murmurs: a late-peaking crescendo-decrescendo murmur at the right upper sternal border suggests aortic stenosis 2
• A soft or absent aortic component (A2) of S2 combined with other findings establishes high pre-test probability for severe aortic stenosis 1, 2

Diagnostic Workup

Echocardiography (First-Line Test)

Transthoracic echocardiography is the recommended first-line diagnostic test for evaluating any abnormal heart sound pattern 1, 2

The echocardiogram must assess:

• Left ventricular wall thickness, size, and systolic function 1
• Valvular structure and function, particularly aortic and pulmonic valves 1
• Right ventricular size and function 1
• Presence of intracardiac shunts, specifically atrial septal defect 1

Common Diagnostic Pitfall

If physical examination strongly suggests severe aortic stenosis but echocardiography shows only mild stenosis, the echocardiogram has likely underestimated disease severity—clinical findings should take precedence 2

Condition-Specific Management

Normal Physiologic Splitting

• A normally split S2 that varies with respiration reliably excludes severe aortic stenosis and requires no treatment 2
• No further cardiac workup needed if respiratory variation is clearly present and physical examination is otherwise normal 1, 2

Fixed Splitting (Atrial Septal Defect)

• Fixed splitting indicates right ventricular volume overload and mandates evaluation for intracardiac shunts 1, 3
• Look for right axis deviation and incomplete right bundle branch block on ECG 3
• Assess for right ventricular lift on examination 3
• Echocardiography will identify atrial septal defect or other structural causes 1, 3

Reverse Splitting (Severe Aortic Stenosis)

• Reverse splitting may indicate delayed left ventricular systole requiring investigation for structural heart disease or conduction abnormalities 1, 3
• In severe aortic stenosis, valve calcification prevents normal rapid closure, causing A2 to become soft or absent 2
• Aortic valve replacement must be considered in all patients with symptoms caused by severe aortic stenosis 1
• The disappearance of A2 is specific (though not sensitive) for severe aortic stenosis 2

Follow-Up Strategy

Surveillance Intervals for Aortic Stenosis

If aortic stenosis is identified, follow-up echocardiography intervals are: 1, 2

• Severe aortic stenosis: yearly
• Moderate aortic stenosis: every 1-2 years
• Mild aortic stenosis: every 3-5 years

Exercise Testing Considerations

• Exercise testing may be considered (Class IIb) in asymptomatic patients with aortic stenosis to elicit exercise-induced symptoms and abnormal blood pressure responses 1, 2
• Exercise testing should NOT be performed in symptomatic patients with aortic stenosis (Class III contraindication) 1, 2

Special Populations

Elderly Patients

• Advanced age alone is not a contraindication to valve surgery—valve replacement is technically possible at any age 1
• However, advanced cancer, permanent neurological defects from stroke or dementia, and severe deconditioning make cardiac surgery inappropriate 1
• If medications are needed, initiate at lower doses with slower titration due to altered pharmacokinetics and decreased renal/hepatic clearance 1

Pregnancy

• Increased blood volume and enhanced cardiac output can accentuate murmurs associated with stenotic valve lesions 2
• A soft grade 1-2 midsystolic murmur along the mid to upper left sternal edge is frequently normal during pregnancy 2
• The second heart sound may widen and appear fixed during later stages of pregnancy as a normal finding 2