HEART SOUNDS

INTRODUCTION Heart sounds are sounds produced by the mechanical activities of the heart during each cardiac cycle. They are due to movements of Blood flow through the chambers of the heart Cardiac muscle Valves of the heart. These are heard by placing the ear over the chest or by using stethoscope or microphone.

Heart sounds There are four heart sounds produced during each cardiac cycle. First & second heart sounds are more prominent, appear as “LUB & DUB” these sounds are heard by stethoscope. Third heart sound is mild it cannot be heard by stethoscope in normal conditions, but can be heard by microphone. Fourth heart sound is an inaudible, become audible in pathological conditions only by phonocardiogram.

Importance of heart sounds The study of heart sounds has important diagnostic value in clinical practice b/c the alteration in heart sounds indicates the cardiac diseases involving the valves of heart.

First heart sound: It is produced due to the simultaneous closure of both the atrioventricular (mitral & tricuspid) valves. It is produced during isometric contraction period & earlier part of ejection period or at the start of ventricular systole. Characteristics: This is long, soft & low pitched sound It resembles the spoken word “LUBB” The duration of sound is about 0.15 sec Frequency is 25-45 Hz.

ISOVOLUMETRIC CONTRACTION 1st Heart Sound The first heart sound (S1, "lub") is due to the closing AV valves and associated blood turbulence.

CAUSES: Along with closure of A/V valves some other factors also involved to produce 1st heart sound these are, Valvular factor; Synchronous closure of atrioventricular valves set up the vibrations in the valvular leaflets & chordae tendinae. Vascular factor; The distension of aorta & pulmonary artery due to the rush of blood from ventricles into these vessels during ejection period.

3. Muscular factor; The myocardial tension & contraction of ventricular muscle during Isometric contraction & the ejection period. 4. Atrial factor; The residual vibrations produced by the atrial systole also play a role in the production of 1st heart sound. Reduplication of 1st heart sound: This is the splitting of the 1st heart sound, this is due to the asynchronous closure of A/V valves, may occur in normal conditions but rare. 1st heart sound & ECG: coincides with peak R wave in ECG.

Second heart sound: Characteristics: It is produced during the onset of diastole. This sound is due to the simultaneous closure of both the semilunar valves. Characteristics: The 2nd heart sound is a short, sharp & high pitched sound. It resemble the spoken word “DUBB” The duration of the 2nd heart sound is 0.10 to 0.14sec. Frequency is about 50 cycles/sec

ISOVOLUMETRIC RELAXATION 2nd Heart Sound The second heart sound (S2, "dup") occurs when the semilunar (aortic and pulmonary) valves close. S2 is normally split because the aortic valve closes slightly earlier than the pulmonary valve.

Physiological splitting: Reduplication of 2nd heart sound: This is the splitting of this sound. It occurs due to asynchronous closure of both the semilunar valves. Physiological splitting: occurs during deep inspiration. Aotic valve close prior to pulmonary valve & interval widening during inspiration. Pathological splitting: occurs during pulmonary stenosis, right bundle branch block & right ventricular hypertrophy. 2nd heart sound & ECG: It coincide with T wave in ECG

Third heart sound: It is produced during rapid filling period of the cardiac cycle. It is also called ventricular gallop or protodiastolic gallop as produced during earlier part of diastole. Characteristics: The 3rd heart sound is short & low pitched Its duration is 0.07-0.1 sec Frequency is about 1-6 cycles/sec. Cause: It is due to rush of blood into ventricles. When blood flows rapidly, vibrations are set up in ventricular wall resulting in production of sound.

3rd heart sound is not audible by stethoscope, can be heard by microphone. Physiologically can be audible in children & athletes. Pathological conditions: aortic regurgitation or mitral incompetence , cardiac failure & cardiomyopathy with dilated ventricles, severe hypertension, myocardial infarction. 3rd heart sound & ECG: it appears b/w T and P waves.

RAPID VENTRICULAR FILLING 3rd Heart Sound A third heart sound (S3) is usually abnormal and is due to rapid passive ventricular filling.

Fourth heart sound: This sound produced during atrial systole (late diastole). Characteristics: Short & low pitched sound Duration is 0.02-0.04 sec Frequency is 1-4 cycles/sec. Cause: During atrial systole vibrations are set up in the atrial musculature & in the flaps of A/V valves.

ATRIAL SYSTOLE 4th Heart Sound A fourth heart sound (S4) is abnormal and is associated with the end of atrial emptying after atrial contraction.

Conditions when 4th heart sound is audible: It occurs with hypertrophic congestive heart failure, massive pulmonary embolism, tricuspid incompetence, or cor pulmonale & aortic stenosis 4th heart sound & ECG: It coincides with the interval b/w the end of P wave & onset of Q wave.

Methods of study of heart sounds: Heart sounds are studied by three methods: By using stethoscope By using microphone By phonocardiogram. 1. BY STETHOSCOPE: 1st & 2nd heart sounds are heard on auscultation areas by stethoscope. Chest piece is placed over 4 auscultation areas. The 4 auscultation areas are: Mitral areas (Bicuspid Area or apex beat area)= 1st heart sound is audible Tricuspid area= 1st heart sound Pulmonary area= 2nd heart sound Aortic area= 2nd heart sound

4 auscultation areas

stethoscope

By Microphone: It is highly sensitive microphone is placed over the chest. The heart sounds are amplified by means of amplifier & heard by using loud speaker. 1st, 2nd & 3rd heart sounds are heard by this method. By Phono cardiogram: Phonocardiography is the technique used to record the heart sounds. phonocardiogram is the graphical record of the heart sounds .It is done by placing an electronic sound transducer over the chest. This transducer is connected to a recording device like poly graph. All the 4 heart sounds can be recorded in phonocardiogram. It helps to analyze the frequency of the sound waves.

Cardio Microphone:

Phonocardiogram