You sometimes think ‘Cardiac Murmurs … Arghhhh. How to simplify it’?!
This definitely is one of the most useful posts for a medical student. It summarizes all that you need to know about Cardiac Murmurs.
Keep reading & enjoy learning.
To simplify, Murmurs can be categorised in the following ways.
1. Timing 2. Duration 3. Pitch 4. Intensity 5. Location 6. Radiation
Practically, all these different categories are combined when describing a murmur.
1 – Timing
Murmur can be a) Systolic b) Diastolic or c) Continuous
a) Systolic: Heard during systole, between S1 & S2. This coincides with the upstroke of the carotid pulse.
b) Diastolic: It is heard during diastole, i.e., between S2 & S1. Just after the carotid pulse upstroke.
c) Continuous murmur: Also called Machinery murmur. As the name implies, it is heard throughout the cardiac cycle i.e., during both systole & diastole. They are not classically cardiac in origin. Examples are Patent ductus arteriosus (PDA), Arteriovenous (AV) fistula etc.
2 – Duration
Systolic & Diastolic murmurs can be further categorized based on the duration or location of the murmur during the systolic or diastolic phases of the cardiac cycle.
a) Systolic Murmurs:
i) Ejection Systolic Murmur: Start at the beginning of systole and reaches its peak in mid systole (Crescendo-Decrescendo Murmur) e.g., Aortic stenosis murmur.
ii) Pansystolic or Holosystolic Murmur: It spans the whole of the systole at a constant intensity. Examples are Mitral Regurgitation, VSD, Tricuspid Regurgitation.
iii) Late Systolic Murmur: Starts in the middle of the systole and extends till S2. Heard in Mitral Leaflet Prolapse (MLP).
b) Diastolic Murmurs:
i) Early Diastolic Murmur: Starts with S2 (closure of aortic & pulmonary valves) but aortic or pulmonary valve insufficiency cannot prevent backflow through the valve so there is an early murmur.
ii) Mid-diastolic Murmur: It is a low-pitched murmur caused by passive ventricular filling during diastole through a narrowed AV valve. e.g., in Mitral Stenosis.
iii) Late Diastolic Murmur: Late diastolic murmur arises in the last 1/3rd of diastole when atria contracts and pushes blood through stenosed mitral or the tricuspid valve. It is also called Presystolic accentuation.
3 – Pitch
A murmur can be either HIGH PITCHED or LOW PITCHED.
a) High-Pitched Murmurs: Easily heard with the diaphragm of a stethoscope.
Examples: Aortic stenosis murmur, AR murmur
b) Low-Pitched Murmurs: Heard on careful listening with the bell of a stethoscope.
Examples: Mitral stenosis.
4 – Intensity
Levine Grading classifies intensity into 6 grades – Grade I to VI, from very faint murmur (audible only on careful listening in a quiet place) to as loud that it is audible with a stethoscope just off the chest.
Diastolic Murmurs rarely goes beyond Grade III in intensity. Similarly, Innocent murmurs (flow murmur) have intensity < 3.
Following are the Six grades of Murmur Intensity: (Click for video)
Grade I/VI: Faint murmur, audible on listening carefully in a quiet room.
Grade II/VI: Soft murmur but immediately audible on placing the stethoscope on the chest.
Grade III/VI: Loud murmur readily audible but without a Thrill.
Grade IV/VI: A loud murmur with Thrill.
Grade V/VI: A loud murmur with a thrill. The murmur is so loud that it is audible with only the rim of the stethoscope touching the chest.
Grade VI/VI: A very loud murmur with a thrill. The murmur is audible with the stethoscope not touching the chest but lifted just off it.
5 – Location
All cardiac auscultatory areas shall be auscultated.
Diastolic Murmurs are heard in specific locations. Mitral stenosis murmur is audible on Apex, & Aortic Regurgitation over the left sternal edge (LSE).
Systolic Murmurs are usually audible over a large area of precordium so locate where it is heard loudest & associated radiation be noted (see below).
6 – Radiation
Murmur can radiate from its original auscultatory area to other areas. It is only seen in systolic murmurs. There is usually no radiation heard with diastolic murmurs.
Systolic murmurs radiate in the direction of the flow of blood across the valve.
– MR murmur from apex to the left axilla.
– Aortic stenosis murmur from right 2nd intercostal space to the neck.
– VSD murmur from LSE to the right sternal edge.
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