How to do Cardiac Auscultation with a Stethoscope

Cardiac auscultation remains one of the most integral parts of physical examination and provides enough information about the animal’s condition if performed correctly. Even though the examination itself cannot confirm a diagnosis, it can be used as a guide for further diagnostics along with the thorough history of symptoms of the patient. Before actually doing cardiac auscultation you will need to learn the standard nomenclature – murmur loudness rating (grading scale), murmur quality and location description, and the transient cardiac sounds. It is also very important to listen for cases of arrhythmias. It’s always a good idea to use a high-quality stethoscope model with double-lumen tubing, large and small diaphragms, and a bell.

Performing cardiac auscultation

At first, palpate the precordium and locate the beat of the heart against the chest wall around the fifth and sixth intercostals space. This is known as apical impulse and there might be some breed variations in regards to the location. Afterward, you start the auscultation and search for two types of sound: murmurs and transient sounds. Murmurs are sounds of turbulent blood flow and most commonly you will hear these abnormal sounds of the heart.

PMI is the location where the murmur is heard the loudest. The auscultation begins on the left apex beat where the mitral valve is best heard. From there you should move the stethoscope dorsal and cranial taking one intercostal space. This is the area of the aortic valve, and approximately half an intercostal space ventral and cranial to this point is the pulmonic valve. Dorsally to this the area where the great vessels cross can be auscultated. After you finish with the left side you should move on to the right hemithorax. Across the area where the mitral valve was examined on the left side, on the right side, the tricuspid valve is located. The last thing to do is listen for murmurs arousing from septal ventricular defects located on the dorsal cranial region on the right chest wall.     

In small animals, the first and second heart sounds (S1, S2) known as lub and dub are the only normal sounds. Additional S3 and S4 referred to as gallop sounds always mean that there is something wrong. In equines and cattle, S3 and S4 are normally heard.

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