Early diastolic murmurs: Begin immediately after S2, are high-pitched, and are usually caused by aortic or pulmonary regurgitation.
Mid-to-late diastolic murmurs: Low-pitched, heard best with bell of stethoscope; observed in MS or TS; less commonly due to atrial myxoma.
Continuous murmurs: Present in systole and diastole (envelops S2); found in patent ductus arteriosus and sometimes in coarctation of aorta; less common causes are systemic or coronary AV fistula, aortopulmonary septal defect, ruptured aneurysm of sinus of Valsalva.
For a more detailed discussion, see O'Gara PT, Loscalzo J: Physical Examination of the Cardiovascular System, Chap. 267, p. 1442, in HPIM-19.