What: Is The S2 Heart Sound
But S2 tells stories of illness, too.
When you breathe in, your diaphragm descends. The pressure inside your chest drops, drawing more blood into the right heart. That extra blood takes a little longer to eject through the pulmonic valve, so P2 is delayed. Meanwhile, the left heart receives slightly less blood during inspiration, so A2 happens a hair earlier. The result: on a good exhalation, “dub” sounds like one crisp note. On a deep breath in, the “dub” splits into two soft, fleeting clicks— tuh-dup . This is called of S2. It is normal, even beautiful, a sign of a flexible, responsive heart. what is the s2 heart sound
Picture the instant. Ventricles have just finished squeezing. Their pressure plummets. For a fraction of a second, the aorta (high pressure) and the pulmonary artery (lower pressure) still hold blood that wants to surge backward into the heart. But the aortic and pulmonic valves snap shut like umbrellas blown inside out by the wind—only in reverse. Their cusps meet, tense, and vibrate. That vibration, transmitted through the chest wall, is S2. But S2 tells stories of illness, too
If the split is —meaning the valves close in reverse order (P2 before A2) and the split narrows on inspiration instead of widening—that could murmur of left bundle branch block or aortic stenosis . The left ventricle struggles to finish its squeeze, so A2 arrives late. That extra blood takes a little longer to
S2 is the sound of closure. Not of all doors, but of the two great exit valves from the heart’s lower chambers: the aortic valve on the left, and the pulmonic valve on the right.
If the split becomes —present on both inhale and exhale, never coming back together—that might whisper of an atrial septal defect , a hole between the heart’s upper chambers. Extra blood sloshes through the right side, always delaying P2.
The most famous S2 of all—the one taught in every medical school—is the heard during a heart attack affecting the left bundle branch. It defies nature: the “dub” splits as you breathe out , not in. A clue hidden in a heartbeat.