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The fourth heart sound or S 4 is an extra heart sound that occurs during late diastole, immediately before the normal two "lub-dub" heart sounds (S 1 and S 2).It occurs just after atrial contraction and immediately before the systolic S 1 and is caused by the atria contracting forcefully in an effort to overcome an abnormally stiff or hypertrophic ventricle.
The first heart sound, or S 1, forms the "lub" of "lub-dub" and is composed of components M 1 (mitral valve closure) and T 1 (tricuspid valve closure). Normally M 1 precedes T 1 slightly. It is caused by the closure of the atrioventricular valves , i.e. tricuspid and mitral (bicuspid), at the beginning of ventricular contraction, or systole .
Ectopic beats are considered normal and are not indicative of cardiac pathology. Ectopic beats often remain undetected and occur as part of minor errors in the heart conduction system. They are rarely indicative of cardiac pathology, although may occur more frequently or be more noticeable in those with existing cardiac abnormalities.
A gallop rhythm refers to a (usually abnormal) rhythm of the heart on auscultation. [1] It includes three or four sounds, thus resembling the sounds of a gallop.. The normal heart rhythm contains two audible heart sounds called S 1 and S 2 that give the well-known "lub-dub" rhythm; they are caused by the closing of valves in the heart.
If the heart rate is also very fast (tachycardia), it can become difficult to distinguish between S 3 and S 4 thus producing a single sound called a summation gallop. S 3 is a dull, low-pitched sound best heard with the bell placed over the cardiac apex with the patient lying in the left lateral decubitus position. This heart sound when present ...
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Heart disease was excluded after physical examination, chest x-ray, ECG, echocardiography, maximal exercise stress test, right- and left-heart catheterization and coronary angiography. [30] In 122,043 United States Air Force flyers and cadet applicants during approximately 48 seconds of ECG 0.78% (952 males) had PVC within all age groups, but ...
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