Phonocardiograms from normal and abnormal heart sounds

A phonocardiogram (or PCG) is a plot of high-fidelity recording of the

sounds In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...

and murmurs made by the

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...

with the help of the machine called the phonocardiograph; thus, phonocardiography is the recording of all the sounds made by the heart during a

cardiac cycle The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following ...

Medical use

Heart sounds result from vibrations created by the closure of the

heart valve A heart valve is a one-way valve that allows blood to flow in one direction through the chambers of the heart. Four valves are usually present in a mammalian heart and together they determine the pathway of blood flow through the heart. A heart v ...

s. There are at least two; the first (S1) is produced when the atrioventricular valves (tricuspid and mitral) close at the beginning of

systole Systole ( ) is the part of the cardiac cycle during which some chambers of the heart contract after refilling with blood. The term originates, via New Latin, from Ancient Greek (''sustolē''), from (''sustéllein'' 'to contract'; from ''sun ...

and the second (S2) when the

aortic valve The aortic valve is a valve in the heart of humans and most other animals, located between the left ventricle and the aorta. It is one of the four valves of the heart and one of the two semilunar valves, the other being the pulmonary valve. The ...

and

pulmonary valve The pulmonary valve (sometimes referred to as the pulmonic valve) is a valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps. It is one of the four valves of the heart and one of the two semilunar va ...

(semilunar valves) close at the end of systole. Phonocardiography allows the detection of subaudible sounds and murmurs and makes a permanent record of these events. In contrast, the

stethoscope The stethoscope is a medical device for auscultation, or listening to internal sounds of an animal or human body. It typically has a small disc-shaped resonator that is placed against the skin, and one or two tubes connected to two earpieces. ...

cannot always detect all such sounds or murmurs and provides no record of their occurrence. The ability to quantitate the sounds made by the heart provides information not readily available from more sophisticated tests and provides vital information about the effects of certain

drugs A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via inhalat ...

on the heart. It is also an effective method for tracking the progress of a patient's disease.

Discrete and the packet wavelet transform

According to a review by Cherif et al., discrete wavelet transform DWT is better at not affecting S1 or S2 while filtering

heart murmurs Heart murmurs are unique heart sounds produced when blood flows across a heart valve or blood vessel. This occurs when turbulent blood flow creates a sound loud enough to hear with a stethoscope. Turbulent blood flow is not smooth. The sound di ...

. Packet wavelet transform affects internal components structure much more than DWT does.

History

Awareness of the sounds made by the heart dates to ancient times. The idea of developing an instrument to record it may date back to

Robert Hooke Robert Hooke FRS (; 18 July 16353 March 1703) was an English polymath active as a scientist, natural philosopher and architect, who is credited to be one of two scientists to discover microorganisms in 1665 using a compound microscope that ...

(1635–1703), who wrote: "There may also be a possibility of discovering the internal motions and actions of bodies - whether animal, vegetable, or mineral, by the sound they make". The earliest known examples of phonocardiography date to the 1800s. Monitoring and recording equipment for phonocardiography was developed through the 1930s and 1940s. Standardization began by 1950, when the first international conference was held in Paris. A phonocardiogram system manufactured by Beckman Instruments was used on at least one of the

Project Gemini Project Gemini () was NASA's second human spaceflight program. Conducted between projects Mercury and Apollo, Gemini started in 1961 and concluded in 1966. The Gemini spacecraft carried a two-astronaut crew. Ten Gemini crews and 16 individual ...

manned spaceflights (1965-1966) to monitor the heartbeat of astronauts on the flight. It was one of many Beckman Instruments specialized for and used by NASA. John Keefer filed a patent for a phonocardiogram simulator in 1970 while he was an employee of the U.S. government. The original patent description indicates that it is a device which via ''electrical

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...

'' mimics the human heart's ''sounds''.

Medical use

Discrete and the packet wavelet transform

History

See also

References

Further reading