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first heart sound (S1)

Occurs immediately following the QRS complex on EKG & reflects closing of the mitral valve & tricuspid valve. At a rate of about 120 beats/second, systole & diastole become indistinguishable by auscultation & S1 must be distinguished from S2 from the timing of the carotid or apical impulse, both which occur in early systole, immediately after S1. Loud S1: 1) mitral stenosis 2) short PR interval 3) thin chest wall Soft S1: 1) long PR interval 2) heart failure 3) mitral regurgitation 4) heavily calcified mitral valve 5) thick chest wall 6) pulmonary emphysema

General

heart sound(s)

References

  1. Harrison's Principles of Internal Medicine, 13th ed. Companion Handbook, Isselbacher et al (eds), McGraw-Hill Inc. NY, 1995, pg 327
  2. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 38
  3. Guide to Physical Examination & History Taking, 6th edition, Bates B, JB Lippincott, Philadelphia, 1995, pg 283-85