Murmurs Made Easy

For the purpose of this post, I shall fast forward the examination of the heart to auscultation of the heart murmurs. 

We begin auscultation of the precordium by placing the stethoscope over the mitral area. 

A hand drawn picture of the anterior chest with the location of each valves

One very important step which is often overlooked or neglected by medical students is the instruction to the patient to breathe in and breathe out slowly. Personally, I would let my stethoscope to remain over each valve area for a total duration of 2 breathing cycles (i.e. breathe in-breathe out-breathe in-breathe out) before moving to the next valve area. 

Let us recap the basic physiological changes that affect murmurs during breathing. During inspiration, the increased thoracic cavity volume lowers intrathoracic pressure thus increases venous return to the right side of the heart. This will cause an increase in murmur intensity for tricuspid and pulmonary valve disorders. 

On the other hand, expiration reduces the thoracic cavity volume and thus increases arterial outflow from the left side of the heart. This will cause an increase in murmur intensity for mitral and aortic valve disorders. 

This basic concept is very important and will help guide you to eliminate and narrow down possible differentials for every murmur heard over any particular valve area as I will explain next. 

Let us begin at the mitral valve area. Place the diaphragm of the stethoscope over the mitral valve area. Regardless whether you hear any murmurs or not, I would encourage you to do the breathing manouvres for at least 2 breath cycles as mentioned above. If there are any soft murmurs, this manouvre will enhance or increase the murmur intensity. 

If there is a murmur heard over the mitral area, below are the possible causes:

1. Mitral regurgitation (MR)

2. Mitral stenosis (MS)

3. Aortic stenosis (AS)

4. Tricuspid regurgitation (TR)

5. Ventricular septal defect (VSD)

To help differentiate between the causes, here is how the breathing manouvre will help narrow down the diagnoses. 

If during inspiration, the murmur heard over the mitral area becomes louder, then it can be concluded that the murmur is actually originating from the neighbouring tricuspid valve. Therefore the murmur detected over the mitral valve can be ignored. The murmur will then be best heard over the tricuspid area after completing the mitral valve examination. 

If during expiration, the murmur heard over the mitral area becomes louder, then it can be concluded that the murmur is unlikely to originate from the tricuspid valve or VSD. Only 3 possibilities remain i.e. MR, MS or AS. To differentiate between the 3 possible source of the expiratory phase murmur heard over the mitral valve area, the student will need to time the murmur by palpating the carotid or radial pulse. If the expiratory murmur coincides with the diastolic phase, then the only diagnosis possible would be a MS murmur. Next step is to listen and verify that the murmur is indeed a mid diastolic murmur (MDM) of MS i.e. switching to the bell of the stethoscope and listening for the MDM with the patient lying left lateral.

If the expiratory murmur coincides with the systolic phase, then you have ruled out MS. So all that is left would be either MR or AS. To differentiate between this two, listen to the systolic murmur carefully and decide if its a pansystolic murmur (PSM) or an ejection systolic murmur (ESM). A PSM would classically have a soft S1 with the systolic murmur extending throughout systole. An ESM, on the other hand, would have a clearly heard S1 and the systolic murmur would be heard in mid systole. 

If it is a PSM, then the diagnosis would be a MR. This can be further confirmed by auscultating the axillae for radiation of the MR murmur. If it is a ESM, then the only diagnosis possible would be an AS murmur. An AS murmur can sometimes be heard all the way to the left axillae as well. This phenomenon is called the Gallarvardin phenomenon. 

If there no variation in the murmur intensity between inspiration and expiration, time the murmur by palpating the carotid or radial pulse. A systolic murmur that does not vary with inspiration or expiration heard over the mitral area can only be caused by a VSD. Once you have completed the mitral valve examination, confirm the earlier heard murmur which will be best heard over the lower left sternal edge. This will confirm the presence of a VSD. 

 

Over the tricuspid valve area, the same manouvres as above should be applied. If a PSM is heard over the tricuspid valve area, there are only 3 possibilities: a TR, a VSD or a loud MR. Remember, the chest cavity and specifically the heart isnt a very large structure. Therefore any loud murmur can practically be heard everywhere. If the PSM increases intensity during inspiration, the PSM is confirmed to be from the tricuspid valve i.e. a TR. If the PSM is louder during expiration, then the murmur is a radiation from the mitral valve i.e. a MR. But if the murmur does not change with either inspiration or expiration, then the PSM could be from a VSD. 

 

Over the pulmonary valve area, it is unusual to hear a PSM. But you could detect a ESM of pulmonary stenosis (PS). This is, however, uncommon for undergraduate examinations. An early diastolic murmur (EDM) of pulmonary regurgitation (PR) is even more rare. Both PS and PR murmurs will be louder during inspiration. Also, do look out for machinery or continuous murmurs near the pulmonary valve area. This may indicate presence of a Patent Ductus Arteriosus (PDA). The machinery murmur of a PDA is often heard over the upper left chest area just below the left clavicle. This area is often close to the pulmonary valve area.

Over the aortic valve area, it is also uncommon to hear a PSM. Look out for ESM of aortic stenosis (AS) and EDM of aortic regurgitation (AR). Both AR and AS murmurs will be louder during expiration. AR murmur can be further verified by presence of EDM which is best heard over the Erb's space or second aortic space over the left sternal edge with the patient leaning forward. AR murmurs are usually accompanied by other peripheral signs like Corrigan's sign (bilateral prominent carotid arterial pulsations), a collapsing pulse as well as wide pulse pressure. AS murmurs can sometimes radiate to both carotid arteries and this feature should be looked for and examined routinely in patients with AS murmurs. However, AS due to aortic sclerosis (degenerative cause) may not always have radiation to both carotids. The ESM murmur may be localised to the aortic valve area only. It is important to take note of this. In real life practice, the ESM of AS can sometimes be heard over the pulmonary valve area as well. This may confuse the unsuspecting student. However this confusion can be avoided when patient is asked to inspire and expire slowly. If the ESM heard over the pulmonary valve area is louder during inspiration as mentioned earlier, then the ESM is likely due to PS. If the ESM over the pulmonary valve area is louder during expiration, then the ESM is likely to originate from the neighbouring aortic valve i.e. an AS.

CCE.