\n\nOverview\nA phonocardiogram (PCG) is a high-fidelity plot of heart sounds over time. An example of a normal PCG can be found above. PCGs are useful tools that can be used to determine overall heart health through the detection of otherwise subaudible sounds and murmurs. PCGs quantify heart sound characteristics (e.g., intensity, timing, and duration) and are an effective method for tracking the progression of disease and effects of drugs on the heart.\n\n\n\nSimplified PCG\nSimplifying a PCG into discrete components makes disease diagnosis easier. In the simplified form, the audio intensity (volume) is represented on the y axis and increases with distance from the centerline. A flat line represents silence. The first (S1) and second (S2) heart sounds are represented by thick vertical lines with heights directly proportional to their respective intensities. A normal heart sound example can be seen above.\n\n\n\nSystolic murmur\nThe timing of sounds relative to the cardiac cycle is important when analyzing heart sounds and PCGs. A murmur that starts during or after the first heart sound (S1) and ends before or during the second heart sound (S2) is called a systolic murmur because during that period of time blood is being ejected from the ventricles (systole). \n\n\n\nDiastolic murmur\nSimilarly, a diastolic murmur starts during or after the second heart sound (S2) and ends before or during the first heart sound (S1), because that period of time corresponds to ventricular relaxation (diastole).\n\n\n\nContinuous murmur\nContinuous murmurs are audible throughout the cardiac cycle. They start in systole and continue through S2 into part or all of diastole.\n\n\n\nCrescendo \nMurmurs are further classified by their points of highest audio intensity which can be seen as distinct shapes in normal and simplified phonocardiograms (PCGs). For example, the crescendo murmur above progressively increases in intensity over time.\n\n\n\nDecrescendo\nDecrescendo murmurs gradually decrease in intensity over time. \n\n\n\nCrescendo-decrescendo \nA crescendo-decrescendo murmur will gradually increase intensity, reach a maximum, and then progressively decrease intensity over its duration. \n\n\n\nPlateau \nA plateau murmur maintains a relatively constant volume and intensity. It is represented by a rectangle in a simplified PCG.\n\n\n\nTiming\nMurmurs can be further classified depending on their point of highest intensity within the cardiac cycle.\n\n\n\nEarly peaking\nEarly peaking murmurs have the point of highest intensity located near the start of systole or diastole. For example, the early peaking diastolic murmur above reaches maximum intensity near the start of diastole (S2).\n\n\n\nMid peaking\nMid peaking murmurs have the point of highest intensity located close to the middle of systole or diastole.\n\n\n\nLate peaking\nLate peaking murmurs have the point of highest intensity located at the end of systole or diastole. A late systolic plateau murmur like the one above may extend all the way to S2.\n\n\n\nHolosystolic\nHolosystolic murmurs begin with the first heart sound (S1) and end with the second heart sound (S2), without a large variation in intensity (plateau). The sound intensity is present and almost constant between S1 and S2. \n\n\n\nHolodiastolic\nA holodiastolic murmur is audible for the entire duration of diastole with an almost constant intensity. It starts with the second heart sound (S2) and ends with the first heart sound (S1).\nMedical Advice Disclaimer\nDISCLAIMER: THE CONTENT SET FORTH HEREIN DOES NOT PROVIDE MEDICAL ADVICE OR IS AN ATTEMPT TO PRACTICE MEDICINE\nThe information, including but not limited to, text, graphics, images, and other material contained on this website are for informational purposes only. No material on this website or document are intended to be a substitute for professional medical education, advice, diagnosis, or treatment.