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tricuspid valve and the opening of the aortic valve allowing flow into the aorta and the rest of the
body [4].
1.3 Generation of acoustic vibrations during the cardiac cycle
The previous section describes the contractions of the heart cavities giving rise to displacement
(flow) of blood, increasing and decreasing pressure and opening and closing of valves. Each of
these events occurs in different temporal overlaps, at acoustic frequencies higher than those of
simply the heart rate and may be collected with instruments like the stethoscope. These vibration
frequencies between 20 and 3000 Hz are considered heart sounds are used in auscultation
techniques and PCG.
There are two main sounds in the cardiac cycle of a healthy heart: the first due to the closure
of the mitral and tricuspid valves and the second due to the closure of the aortic and pulmonary
valves. During these closures, an abrupt change of intraventricular and arterial pressure occurs
generating a sound wave that is transmitted to the heart wall, mainly through the blood. The
flowing blood itself produces sound, especially as it flows through the variable-size openings at the
valves. This acoustic system then excites the transducer used to record the sounds and can be
tested on the model proposed.
There are other significant sounds that are generated in pathological conditions: a sound due to
narrowing (stenosis) of the connections between atria and ventricles, deficient closure
(regurgitation) of the valves, and other pathological recirculations such as heart murmurs. The
acoustic disturbances caused by these pathologies can be picked up by the transducer and used in
the model.
1.4 The need and software to fill the need
The application of recording techniques, visualization and processing of PCGs is the classification
of the auscultatory findings into diagnostic categories. A few pathologies of interest that can be
detected by PCG are: changes in ventricular compliance (diastolic dysfunction), pericardium
changes, congenital heart disease, innocent murmurs (especially in children), monitoring of
patients with prosthetic heart valves, mitral stenosis detection, mitral regurgitation, aortic
stenosis, pulmonary stenosis, valve sclerosis, mitral valve insufficiency, obstructive hypertrophic
cardiomyopathy, and coronary AV fistulas, among others [5].
Because of its complexity, caused by variations in time and frequency, as well as by age, the
patient's pathology and even differences between test days, analyzing biomedical signals presents
some difficulty. These complexities can increase the difficulty in detection and even alter the
biomedical signals, and therefore constitute a barrier to early diagnosis of certain diseases [3]. As a
specific example PCG has fallen into disuse in favor of EKG and echocardiographic (ECG) studies,