The heart foci They are specific areas of the thorax where heart sounds can be seen, corresponding to the closure of the four heart valves. These foci are in areas where blood passes, once it has passed the valve to be auscultated.
An audible vibration is generated in the process because sound travels with the bloodstream. Auscultation of cardiac foci is the method of cardiovascular physical examination that provides the most information in cardiothoracic evaluation.
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Audible physiological heart sounds are the first and second sounds; however, under certain physiological conditions the third and fourth sounds can also be heard.
Between the first and second sounds there is a space called “small silence”, which corresponds to ventricular systole; and between the second and the first noise there is again a space called “great silence”, which corresponds to ventricular diastole.
The first noise corresponds to the closure of the atrio-ventricular valves, and indicates the onset of ventricular systole (small silence).
The second heart sound occurs when the aortic and pulmonary (sigmoid) valves close. Under normal conditions, a slight doubling can be heard (hearing the blow in two almost immediate times) due to the slightly precocious closure of the aortic valve with respect to the pulmonary valve..
It is difficult to differentiate the third noise, because a little expert ear can confuse it with the doubling of the second noise. It is a low-pitched noise that is produced by the vibration of the ventricular wall at the beginning of diastole.
It is heard in some cases, mainly in children and young adults. When heard in people over 40 years of age, it is usually secondary to mitral regurgitation, which increases the pressure of blood flow to the ventricle and, therefore, the filling is perceived on auscultation.
The fourth heart sound is produced by the sudden deceleration of blood flow against a hypertrophied ventricle. It is less frequent than the third noise and its presence usually has pathological significance.
With the advancement of medicine, the methods of physical examination of the patient have been refined, and consensus has been achieved on the areas that allow the heart sounds important for the cardiovascular physical examination to be clearly detailed. These areas or foci are the following:
It is the fifth left intercostal space (between the 5th and 6th rib) on the midclavicular line.
It corresponds to the cardiac apex. It is the focus where the closure of the mitral valve can be heard best.
This is because the left ventricle has more contact with the rib wall at this point. Since the flow from the left atrium, after passing the mitral valve, reaches the left ventricle, the sound of the valve closing propagates through this chamber.
It is located at the junction of the body of the sternum with the xiphoid appendix or the 4th and 5th left intercostal space next to the sternum.
It corresponds to the noise of the closure of the tricuspid valve that projects through the right ventricle to the lower portion of the body of the sternum.
It is located in the 2nd left intercostal space with a left parasternal line. It is parallel to the aortic focus.
In this focus, the pulmonary valve closing noises can be perceived more clearly.
It is parallel to the pulmonary focus on the opposite side and is located in the 2nd right intercostal space with a right parasternal line.
It corresponds to the area where the sounds of the aortic valve closure of the supraigmoid portion of the artery are projected.
It is located in the left third intercostal space with a left parasternal line. It is also called the Erb focus.
It corresponds to the projection of the sounds of the aortic valves, especially those dependent on valve regurgitation.
Initially, the exploration of heart sounds was performed by applying the ear directly to the areas to be explored.
At present, cardiac auscultation consists of listening through the use of a stethoscope to the sounds produced in the precordial area and its vicinity..
The ear pieces of the stethoscope must fit snugly into the ear so that there is an airtight system from the thorax to the eardrum. The length of the tube should not exceed 50 cm.
If possible, the physical examination should be performed in a well-lit, low-noise room. The doctor should stand to the right of the patient.
It should be heard directly on the patient's skin, never over clothing. If possible, all foci should be auscultated with the membrane (heart murmurs and lung sounds) and the bell (normal heart sounds) of the stethoscope, in order to capture high and low frequency sounds, respectively..
It is usually done in the supine position. If for some reason the heart sounds are not very audible, we proceed to auscultation in the left lateral decubitus position (pachón position).
Some sounds are better heard in different positions, especially pathological sounds.
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