Physiology of Heart Sounds and Murmurs Authors: Michael A. Chizner, MD Journal: Heart Disease: A Textbook of Cardiovascular Medicine (often updated; look for chapters in Braunwald’s Heart Disease) OR a dedicated review in Current Problems in Cardiology Example modern review: "Heart Sounds: From the Physiology to the Bedside" — Journal of Cardiovascular Medicine (various years, e.g., 2018, 2022)
The "dub" occurs at the beginning of ventricular diastole. This is the phase where the ventricles relax so they can refill with blood for the next beat.
Variations in these sounds provide critical diagnostic data. For instance, a "murmur" represents turbulent blood flow often caused by a valve that fails to open fully (stenosis) or close completely (regurgitation). A "gallop rhythm," characterized by a third heart sound ($S_3$), suggests volume overload or heart failure. Thus, the simple "lub-dub" is a complex acoustic window into the structural integrity of the heart.
This closure prevents blood from flowing backward into the atria as the ventricles begin to squeeze. The "Dub" (S2 Sound) what causes the lub dub sound of the heart
As the ventricles squeeze, the pressure inside them rises sharply. To prevent blood from flowing backward into the upper chambers (the atria), two specific valves snap shut: Located on the left side of the heart.
In a healthy heart, the valves close cleanly and completely. However, if a valve does not close all the way (regurgitation) or is too stiff to open fully (stenosis), the blood flow becomes turbulent.
The primary cause of $S_1$ is the closure of the atrioventricular (AV) valves: the mitral valve (left side) and the tricuspid valve (right side). As the ventricles contract, the pressure within them rises rapidly, exceeding the pressure in the atria. This pressure gradient forces the AV valve leaflets to snap shut. Physiology of Heart Sounds and Murmurs Authors: Michael A
Your heartbeat * After your atria pump blood into the ventricles, the valves between the atria and ventricles close to prevent bac... nhlbi, nih (.gov) The "lub" of the heart's "lub-dub" sound is caused by the closing of the The "lub" of the heart's "lub-dub" sound is caused by the closing of the _______ valves. ... The lub sound is produced by the clos... Quizlet Lub Dub (S1 & S2) Heart Sounds Anatomy Explained in 30 ... Aug 22, 2022 —
The "dub" is caused by the closure of the semilunar valves: the aortic valve and the pulmonary valve. When the ventricles finish contracting and begin to relax, the pressure within the ventricles drops below the pressure in the aorta and pulmonary artery.
This rhythmic sequence represents the cardiac cycle, a perfectly timed process of blood moving through the four chambers of the heart. To understand what causes the lub-dub sound, we have to look at the two distinct phases of a heartbeat: systole and diastole. The First Sound: The "Lub" (S1) Variations in these sounds provide critical diagnostic data
This turbulence creates a swishing or whistling noise known as a . While many murmurs are "innocent" and harmless, others can indicate underlying heart conditions that require medical attention. Doctors also listen for "gallops" (S3 or S4 sounds), which are faint extra clicks or thuds that can signal heart strain or fluid buildup.
While this is an older paper, it is a classic and direct investigation into the cause of the "lub" (S1) and "dub" (S2). It clearly explains the then-current (and still largely correct) understanding: