First heart sound S1

First heart sound (S1): Description, Causes and Risk Factors: S1Heart sounds are discrete bursts of auditory vibrations of varying intensity (loudness), frequency (pitch), quality, and duration. The first heart sound (S1) is composed of several high-frequency components; only the first two are normally audible. These two sets of audible vibrations are temporally related to closure of the mitral and tricuspid valves. The first heart sound coincides with contraction of the ventricles, thus identifying the onset of ventricular systole and the end of mechanical diastole. Causes of soft S1: Poor conductance of sound through chest wall. e.g.: Obesity, emphysema, pleural effusion and pericardial effusion.
  • Decrease in rate of LV pressure development. e.g.: Myxedema, cardiomyopathy, acute MI and MR.
  • PR interval and velocity of valve closure. e.g.: Prolonged PR interval - first degree heart block.
  • Mobility of the valve. e.g.: Severe calcification of the valve or reduced mobility of the valve - Long standing MS is associated with severe calcification of mitral valve and soft S1.
Causes of loud S1: S1 is louder if diastole is shortened due to tachycardia. e.g.: Anemia, anxiety and fever.
  • Increased AV flow due to high cardiac output. e.g.: AV fistula and thyrotoxicosis.
  • Increased AV flow due to left to right shunt. e.g.: atrial septal defect (ASD), patent ductus arteriosus (PDA) and other conditions.
  • Prolonged AV flow due to stenosis. e.g.: Mitral stenosis (MS) and tricuspid stenosis (TS).
  • Short PR interval (velocity of valve closure) - At short PR intervals, the mitral valve leaflets are maximally separated by atrial contraction. At the onset of LV systole, the mitral valve leaflets therefore close with a high velocity and with a large excursion resulting in loud S1.
Symptoms: Symptoms may include: Shortness of breath. Diagnosis: Your cardiologist will listen to your heart with a stethoscope. If problems are detected, he/she may order an echocardiogram to get a better understanding of the abnormal sounds detected. Other tests: Chest X-ray: A chest x ray is a painless test that creates pictures of the structures inside your chest, such as your heart, lungs, and blood vessels. This test is done to find the cause of symptoms, such as shortness of breath and chest pain.
  • EKG: An EKG (electrocardiogram) is a simple test that detects and records the heart's electrical activity. An EKG shows how fast the heart is beating and its rhythm (steady or irregular). An EKG also records the strength and timing of electrical signals as they pass through each part of the heart.
This test is used to detect and locate the source of heart problems. The results from an EKG also may be used to rule out certain heart problems. Treatment: Treatment depends on the cause. Many children and adults have harmless heart murmurs, which do not indicate disease and require no treatment, just periodic checkups by your doctor is mandatory. When other conditions, such as high blood pressure cause first heart sound, your doctor will treat the underlying cause. Some types of heart valve disease may require medications and surgery. NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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