It does not indicate the audible separation of M1 and T1, but instead the presence of an early ejection sound.This can be of either pulmonic or aortic origin.
What is the significance of a split S1 at the base?
It does not indicate the audible separation of M1 and T1, but instead the presence of an early ejection sound.This can be of either pulmonic or aortic origin.
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Is the tricuspid component of S1 (T1) audible at the apex?
No. It is only audible over the lower left sternal border (LLSB). T1, however, may become audible at the apex in case of (1) thickening of the tricuspid valve leaflets (i.e., early tricuspid stenosis) or (2) right ventricular pressure overload (such as pulmonary hypertension or atrial septal defect). What is the significance of a narrowly split S1?
It reflects the audible separation of M1 and T1, a normal phenomenon that may at times be detected by listening over the lower left sternal border/epigastric area (where the tricuspid component is louder and thus easier to separate from its mitral counterpart). What is the sequence of closure and opening of the various valves at
the time of S1? In sequence: Mitral closure (M1) Tricuspid closure (T1) Pulmonic opening Aortic opening The first two events are the only real contributors to S1, whereas the last two may become audible (as ejection clicks/sounds) in case of disease. Which semilunar valve opens first?
The pulmonic, followed by the aortic (low pressure beds always open earlier). As for the intensity, the aortic ejection sound is usually louder than the pulmonic, but still not enough to become audible in the normal patient. Which conditions can be associated with a soft S1?
Other than calcific mitral stenosis, a soft S1 is usually heard in either early closure of the mitral valve (aortic regurgitation) or late closure (prolonged P-R interval). Alternatively, a soft or absent S1 can result from inadequate left ventricular contraction because of congestive heart failure, myocardial infarction, or left bundle branch block (where the left ventricle not only contracts ineffectively, but also late, with M1 following T1; “M” for mitral and “T” for tricuspid). Which atrioventricular valve closes first?
The mitral, followed by the tricuspid (high pressure beds always close earlier). Since mitral closure is much louder than tricuspid, the first component of S1 is usually referred to as M1 and predominates in the formation of the sound. What other conditions can be associated with a loud S1?
In addition to mitral stenosis and the hyperkinetic heart syndrome, a loud S1 is often encountered in: Hypertrophic ventricles Holosystolic mitral valve prolapse with regurgitation (where the prolapse delays the tension of the redundant mitral leaflet, thus allowing it to occur at peak of ventricular contraction, which makes it louder). A similar mechanism takes place in: A left-atrial myxoma. Here it is the tumor that delays the closure of the mitral valve, thus allowing it to occur at peak of ventricular contraction and making it, therefore, louder. As a result, 80% of patients with this condition will have a loud S1. Short P-R interval, as in the pre-excitation syndromes of Wolff-Parkinson-White and Ganong-Levine syndromes. How is S1 in mitral stenosis (MS)?
Booming (in 90% of the patients). A loud S1 should always alert the clinician to the possibility of MS and thus prompt a search for its associated diastolic rumble. Conversely, a soft S1 argues against the presence of uncomplicated MS (i.e., one where the valve is still relatively pliable). The loud S1 is usually the result of: Thickening of the mitral leaflets: In the late stages of MS, however, leaflets can become stiff and poorly mobile, which, in turn, softens S1 and eventually eliminates it. High atrioventricular pressure gradient: This is produced by the stenotic valve and keeps the A-V leaflets maximally separated at the onset of ventricular contraction. How can you separate the variable S1 of atrial fibrillation from that of complete A-V block?5/26/2019 How can you separate the variable S1 of atrial fibrillation from that of complete A-V block?
In atrial fibrillation, the rhythm is irregularly irregular, whereas in third degree, A-V block is a regular bradycardia (due to either nodal or ventricular “escape”). |