Physiology and Etiologies

1. What is meant by a reversed or paradoxical split of the S2?

ANS: This is a split in which the order of components is P2A2 instead of the normal A2P2.

2. Can too early a P2 cause a reversed split?

ANS: A reversed split is nearly always caused by a delayed A2.

3. What can delay the A2 enough to cause a paradoxical splitting?

ANS: a. Conduction defects that delay depolarization of the LV, such as complete LBBB and some types of Wolff-Parkinson-White (W-P-W) preexcitation that imitate LBBB.

Note: The type of W-P-W preexcitation that acts like LBBB is one in which the initial conduction passes to the RV muscle first. This is known as type B, in which the QRS and delta wave in V1 point predominantly posteriorly (i.e., they are predominantly negative).

b. Aortic stenosis with a marked systolic gradient across the aortic valve, causing a delay in the fall of LV pressure to below aortic pressure.

c. Hypertension plus myocardial damage.

4. What causes the widest reversed split?

ANS: Complete LBBB (i.e., with a QRS of 120 ms [0.12 s] or longer). This is also the most common cause of a reversed split and the only one that is easily recognized by the noncardiologist.

These simultaneous intra-arterial and phonocardiogram tracings are from a 59-year-old man in heart failure due to an idiopathic cardiomyopathy. Because of LBBB, the incisura of the pulmonary artery and its simultaneous P2 comes before the aortic incisura and its simultaneous A2. (His pulmonary artery systolic pressure was 35 mmHg; his LV pressure, 120 mmHg; and his cardiac index, 2.4). These are catheter-tip electroma-nometer tracings, so that there are no tubing delays.

These simultaneous intra-arterial and phonocardiogram tracings are from a 59-year-old man in heart failure due to an idiopathic cardiomyopathy. Because of LBBB, the incisura of the pulmonary artery and its simultaneous P2 comes before the aortic incisura and its simultaneous A2. (His pulmonary artery systolic pressure was 35 mmHg; his LV pressure, 120 mmHg; and his cardiac index, 2.4). These are catheter-tip electroma-nometer tracings, so that there are no tubing delays.

5. What is the significance of expiratory splitting of the S2?

ANS: Expiratory splitting indicates either a wide split, a fixed split, or a paradoxical split.

6. What causes the most common confusion with paradoxical splitting of S2?

ANS: An S2-opening snap. (This is discussed in detail in Chapter 10.)

7. How can S2 splitting differentiate a PAC from a PVC?

ANS: If a premature beat has narrow or no splitting of S2, it is probably supraventricular.

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Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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