Understanding Second Heart Sound (S2) Splitting
The second heart sound, S2, is produced by the closure of the aortic and pulmonic valves. It consists of two components: aortic valve closure (A2) and pulmonic valve closure (P2). Normally, A2 precedes P2, and this slight difference in timing is called physiological splitting, which is usually audible during inspiration.
Reverse splitting of S2 is an abnormal finding where P2 precedes A2, or the normal splitting pattern is inverted, often becoming most apparent during expiration.
Conditions Affecting S2 Splitting Patterns
- Atrial Septal Defect (ASD): Typically causes a widely fixed split S2, meaning the split is present and doesn't change significantly with respiration.
- Severe Mitral Regurgitation (MR): Can cause a single S2 due to obscured valve sounds or, less commonly, paradoxical splitting. It is not the most common cause of reverse splitting.
- Left Bundle Branch Block (LBBB): This condition significantly delays the activation and contraction of the left ventricle. This delay causes the aortic valve (A2) to close much later than usual. Consequently, P2 may occur before A2, or the interval between them becomes abnormal, leading to reverse splitting of S2. This is considered the most common cause.
- Pulmonary Hypertension: Severe pulmonary hypertension typically leads to a widened physiological split of S2 because the increased pressure delays pulmonic valve closure (P2), exaggerating the normal inspiratory splitting. It does not typically cause reverse splitting.
Therefore, reverse splitting of the second heart sound is most commonly seen in LBBB.
Important Questions from General Clinical Conditions
- The height of the Jugular Venous Pulse is determined by :
- The SA node is situated at the junction of:
- A 70-year-old man with dyspnoea on exertion has been found to have a single second heart sound and a loud diamond-shaped, rough quality systolic murmur best heard at the right $2^{nd}$ intercostal space, radiating to the right carotid artery. Which one of the following is the likely diagnosis ?
Consider the following statements with regard to pulmonary embolism :
1. Unexplained breathlessness is the most common symptom.
2. When congestive heart failure or pneumonia fail to improve despite standard medical treatment, occult pulmonary embolism should be considered.
3. Patients with high clinical likelihood of venous thromboembolism should first undergo D-dimer testing alone without obligatory imaging tests.
Which of the statements given above are correct?
Consider the following criteria:
1. Pleural fluid protein : Serum protein ratio > 0.5
2. Pleural fluid LDH : Serum LDH ratio > 0.6
3. Pleural fluid LDH > Two-thirds of the upper limit of normal serum LDH
Which of the above criteria, if present in pleural fluid, will indicate an exudate ?
