S4 which is due to diastolic dysfunction of heart is produced due to forceful atrial contraction. S4 can occur in both obstructive and non obstructive HCM.
S3 can also occur due to associated MR.
In patient with ESM with brisk raise of pulse which goes against valvular AS, one has to consider HOCM. Valvular AS produces slow raising pulse
Pulse of HOCM is bisferance type i.e. initial spike is brisk during this initial part (around 80 to 90% of systolic ejection occurs). This is followed by dip in pulse due occurrence of obstruction and again on more slow raising peak.
Bisferance pulse is classically described with severe AR, which is associated with EDM but not HOCM with bisference pulse.
Apical impulse of HCM is very important sign. S4 is palpable, this is followed by early systolic contraction, followed by one more impulse due to occurrence of obstruction, so patient may have triple ripple.
Presence of Loud S4 is a rule in HCM
About 30-50% of HOCM are associated with mitral regurgitation. HCM with MR produces a systolic murmur, which is much longer with both ejection and regurgitant quality. Site of maximal intensity is lower than the site of ejection murmur.
· Valvular aortic stenosis
o Cardinal differential feature between HCM and AS is carotid impulse which is slow raising in valvular AS and brisk in HCM
o Carotid thrill is present in AS and rare in HCM
o ESM of HCM is lower down in precardium where as of valvular AS is on right side
o Post PVC augmentation is more pronounced in HCM than AS
· Mitral regurgitation
o Presence of holosystolic murmur at apex suggest possibility of MR than HCM
o S4 which cardinal sign of HCM is unusual in chronic MR, but in acute MR S4 can occur
o LVH is much more common in HCM.
o Both HCM and MR have quick raise of carotid impulse.
o Reversed splitting is heard in HCM, but in MR wide splitting is heard.
o Post PVC, MR murmur does not change but HCM and AS murmur increases.
· Mitral valve prolapse
o Dynamic auscultation behaviour of MVP and HCM are in similar way
o S4 and is not heard in MVP
o Post PVC murmur of MVP does not increase