What are the characteristic physical examination findings in hypertrophic obstructive cardiomyopathy (HOCM)?

Physical Examination Findings in Hypertrophic Obstructive Cardiomyopathy

The classic physical examination findings in HOCM include a harsh crescendo-decrescendo systolic murmur best heard at the lower left sternal border that increases with Valsalva and standing, a prominent laterally displaced apical impulse (often bifid or trifid), a brisk bifid carotid pulse (pulsus bisferiens), and a fourth heart sound (S4). 1

Cardiac Auscultation

Systolic Murmur Characteristics

• The hallmark is a harsh crescendo-decrescendo systolic ejection murmur best heard at the lower left sternal border and apex, caused by systolic anterior motion (SAM) of the mitral valve producing left ventricular outflow tract obstruction 1
• The murmur is typically late-onset in systole, reflecting the dynamic nature of obstruction that develops as the ventricle empties 2, 3
• A separate late systolic murmur may be heard at the apex, representing posteriorly directed mitral regurgitation from SAM-related leaflet malcoaptation 1

Dynamic Response to Provocative Maneuvers

• Valsalva maneuver (strain phase): The murmur becomes louder as reduced venous return decreases left ventricular cavity size, bringing the hypertrophied septum and mitral valve closer together (65% sensitivity, 96% specificity) 4, 5
• Standing from squatting: The murmur increases markedly as the rapid drop in preload and afterload accentuates dynamic obstruction (95% sensitivity, 85% specificity for squatting decreasing the murmur) 1, 4, 5
• Squatting from standing: The murmur diminishes as increased venous return and afterload expand the left ventricular cavity and relieve obstruction 4, 5
• Isometric handgrip exercise: The murmur decreases because the rise in afterload enlarges the left ventricular cavity, lowering the outflow gradient 5
• Post-premature ventricular contraction beat: The gradient spikes dramatically (Brockenbrough-Braunwald-Morrow sign) due to heightened contractility after the compensatory pause 5

Additional Auscultatory Findings

• Fourth heart sound (S4) is commonly present, reflecting a noncompliant, hypertrophied left ventricle with impaired diastolic filling 1
• Second heart sound (S2) is often abnormal, with delayed aortic component or paradoxical splitting in severe obstruction 2
• Non-ejection systolic clicks may occur due to inequality of mitral chordae tendineae length secondary to asymmetric hypertrophy 2

Precordial Palpation

Point of Maximal Impulse

• A prominent apical impulse is usually present, shifted laterally and either bifid or trifid in character 1
• The bifid impulse reflects the forceful atrial contraction against a stiff ventricle followed by ventricular systole 1

Arterial Pulse Examination

Carotid Pulse Characteristics

• A brisk, bifid carotid upstroke (pulsus bisferiens or "spike-and-dome" pattern) is characteristic, reflecting rapid early ejection followed by mid-systolic obstruction 1, 5
• This contrasts sharply with the delayed, diminished upstroke (pulsus parvus et tardus) seen in aortic stenosis 5

Patients Without Obstruction

• Those without left ventricular outflow tract obstruction (either at rest or with provocation) may have a completely normal physical examination 1
• This underscores the importance of provocative maneuvers during examination when HOCM is suspected clinically 1

Clinical Context and Examination Technique

Systematic Approach

• Physical examination should include maneuvers performed at the bedside: Valsalva, squat-to-stand, passive leg raising, or walking 1
• Auscultation should be performed during each maneuver to detect dynamic changes in murmur intensity 1, 6
• The examination may not be feasible in young children, requiring alternative diagnostic approaches 1

Common Pitfalls

• Failure to perform provocative maneuvers will miss latent obstruction in patients with minimal or absent resting gradients 1
• Confusing the murmur with aortic stenosis: HOCM murmur increases with decreased preload (Valsalva, standing), while aortic stenosis murmur decreases 5
• Overlooking the examination in asymptomatic patients: Many patients are identified incidentally or through family screening and may have subtle findings 1