cardiovascular disorders
Cardiac Auscultation
Continuous murmurs
Continuous murmurs occur throughout the cardiac cycle. They are always abnormal, indicating a constant shunt flow throughout systole and diastole, hence remaining audible through S2. They may be due to various cardiac defects (see table Etiology of Murmurs by Timing ). Some defects produce a thrill; many are associated with signs of right ventricular hypertrophy and left ventricular hypertrophy. As pulmonary artery resistance increases in shunt lesions, the diastolic component gradually decreases. When pulmonary and systemic resistance equalize, the murmur may disappear. Patent Ductus Arteriosus (PDA) murmurs are loudest at the 2nd intercostal space just below the medial end of the left clavicle. When circulation is increased, as occurs during pregnancy, anemia, and Hyperthyroidism , a continuous venous hum is often heard in the right supraclavicular fossa; this venous hum also occurs normally in children. The sound generated by increased flow in a dilated internal mammary artery (mammary souffle), may be mistaken for a continuous cardiac murmur. Mammary souffle is typically heard best over the breast at the level of the right and/or left 2nd or 3rd intercostal space and, although often classified as continuous, is usually louder during systole. 