Heart murmurs are most frequently organized by timing, into

systolic heart murmur Systolic heart murmurs are heart murmurs heard during systole, i.e. they begin and end between S1 and S2. Many involve stenosis of the semilunar valves or regurgitation of the atrioventricular valves. Types * Mid-systolic ejection murmurs ...

s and diastolic heart murmurs. However, continuous murmurs can not be directly placed into either category. These murmurs are due to blood flow from a high pressure chamber or vessel to a lower pressure system. *

Patent ductus arteriosus Patent ductus arteriosus (PDA) is a medical condition in which the ''ductus arteriosus'' fails to close after childbirth, birth: this allows a portion of oxygenated blood from the left heart to flow back to the lungs from the aorta, which has a h ...

. Patent ductus arteriosus (PDA) is an abnormal connection between the aorta and the pulmonary artery, which normally should be closed in infancy. Since aortic pressure is higher than pulmonary pressure, a continuous murmur occurs. This murmur is often described as a machinery murmur, or Gibson's murmur. This is named for George Alexander Gibson, who characterised it in 1898.Gibson GA 1898 Diseases of the heart and aorta. Pentland, Edinburgh, pp 61, 303, 310–312 * Aortopulmonary window. * Shunts. Usually a left to right shunt through a small atrial septal defect in the presence of mitral valve obstruction.

References

Heart murmurs Turbulence {{Cardiology-stub}