Murmurs: Loud and clear

Murmurs: Loud and clear

Veterinary professionals, lend me your ears while I talk about the sound of heart murmurs and their locations.

Photo: Shutterstock.comTo start with the basics, murmurs are the sound of turbulent blood flow in the cardiac structures and are the most common abnormal cardiac sounds you’ll hear. Blood flow moves in a laminar fashion—as in, a smooth unidirectional motion—in a normal heart. Murmurs are indicative of turbulent blood flow in the heart and are typically longer in duration. The normal heart sounds are transient sounds, as they’re called, and short in duration. Some abnormal transient sounds are clicks and gallops, but they are not murmurs.

We're in for a bit of turbulence, folks

Turbulence is created when the blood moves in multiple directions at varying velocities all at once. The turbulence creates vibrations, which you can hear with a stethoscope or, in extreme cases, you can feel with your fingers as a palpable thrill. The grade of the murmur isn’t always correlated with the severity of the disease. Radiographic and echocardiographic examinations are necessary for a complete diagnosis and prognosis. However, accurate isolation and identification of the murmur can limit the list of rule-outs.

Paint a better picture to help veterinarians 

Knowing how to describe what you hear is the first step to take when it comes to murmurs. Location, timing (systolic, diastolic or continuous), and loudness are all great descriptors to use for murmurs, and by using this scheme, you’re able to tell the veterinarian you hear a grade-3 systolic murmur that’s heard best over the mitral valve. Or you could describe the same murmur as a left apical grade-3 systolic murmur—both are correct, since they describe where you heard the murmur (left side over the mitral valve or left apex), the loudness (grade 3) and the timing (systolic). Loudness is graded on a 1-6 scale, with 6 being the loudest.

Location, location, location

The location of a murmur is described as either right or left hemithorax and by valve area of the point of maximal intensity (PMI). The PMI is the location where a murmur is heard the loudest. This term is often mistakenly used to mean the apex beat.

A simplified method of describing PMI location is to identify a murmur ventral to the costochondral junction (the mitral valve area) as apical and one that is dorsal to the costochondral junction (the aortic and pulmonic valve regions) as basilar and the side of the chest (right versus left).

Are you still all ears? Good. Now go forth and use your new knowledge. Before you go, just remember to always listen carefully to every patient—especially the normal ones—to improve your skills and become a pro.

H. Edward Durham Jr., CVT, LATG, VTS (cardiology), is senior veterinary technician in anesthesia at Ross University School of Veterinary Medicine and Editor and author of Cardiology for Veterinary Technicians and Nurses. He is also a charter member of the Academy of Internal Medicine for Veterinary Technicians and until recently served on its executive board as the director at large—cardiology.