II. Physiology
- S1 Heart Sound represents closure of the mitral and tricuspid valves
III. Causes: S1 Augmented or Loud
- Normal in children
- Increased Cardiac Output: Hyperkinetic or Sinus Tachycardia
- Intrinsic Heart Disorders
- Mitral Stenosis
- Tricuspid Stenosis
- Short PR Interval (e.g. WPW Syndrome, nodal rhythm)
IV. Causes: S1 Diminished, Soft or Muffled
- First degree AV Block
- Mitral Regurgitation (or valve calcification)
- Tricuspid Regurgitation (or valve calcification)
- Congestive Heart Failure (Right or Left Ventricular Dysfunction)
- Acute Coronary Syndrome (acute Myocardial Infarction)
- Shock
- Overall Muffled heart sounds (thick chest wall, Obesity, COPD, Pericardial Effusion)
V. Causes: Split S1
-
General
- M1 (mitral) is normally louder, and occurs slightly before T1 (tricuspid)
- Split S1 is best heard at the tricuspid auscultation point (4th left sternal border)
- Widely Split S1
- Complete Right Bundle Branch Block
- Left ventricular pacing
- Ebstein's Anomaly
- Reversed Split S1 (delayed M1 falls after T1)
- Complete Left Bundle Branch Block
- Right ventricular pacing
- Severe Mitral Stenosis
- Left atrial Myxoma
VI. Causes: S1 Variable
- Atrial Fibrillation
- Ventricular Tachycardia
- Frequent Extrasystole
- Third degree AV Block
- Intermittent Loud S1 (Cannon sound)
VII. Resources
- University of Michigan Heart Sound and Murmur Library
- Felner in Walker (1990) The Fourth Heart Sound, Clinical Methods, 3rd ed
Images: Related links to external sites (from Bing)
Related Studies
| Concepts | Finding (T033) |
| SnomedCT | 47309005 |
| English | First heart sound, S1 (function), First heart sound, S1, function (observable entity), First heart sound, S1, First heart sound, S<sub>1</sub> (function), First heart sound, S<sub>1</sub>, function (observable entity), First heart sound, S<sub>1</sub>, First heart sound, S1, function, First heart sound, S<sub>1</sub>, function, First heart sound, S>1<, function, First heart sound, S<sub>1</sub>, NOS, First heart sound, S1, NOS, First heart sound, S>1<, NOS, First heart sound, S>1<, function (observable entity), First heart sound, S>1<, First heart sound, S>1< (function) |
| Spanish | primer ruido cardíaco, R1, primer ruido cardíaco, R1 (función), primer ruido cardíaco, R<sub>1</sub>, primer ruido cardíaco, R<sub>1</sub> (entidad observable), primer ruido cardíaco, R1 (entidad observable), primer ruido cardíaco, R<sub>1</sub> (función), primer ruido cardíaco, R>1< (entidad observable), primer ruido cardíaco, R>1< (función), primer ruido cardíaco, R>1< |
