NWCC Newsletter
Whippet Wanderings Club Newsletter
The NWCC publishes an informative newsletter, Whippet Wanderings, four times a year. Our newsletter contains regional reports, Specialty reports, coursing results, and informative articles and information of interest to whippet fanciers.
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Whippet Wanderings Quarterly Article
Small snippets from each issue of WW will be posted here... stay tuned for updates!
Heart Sounds: What Auscultation Tells Us
Excepts by Janet Lalonde, DVM (author permission is required for usage)
One of the most useful tools in veterinary medicine is the stethoscope. Its principle function is to relay heart sounds transmitted from the chest wall to our ears. Auscultation of cardiac sounds is the basis for diagnosing cardiac conditions. Auscultation allows the detection of the normal heart sounds that mark the mechanical events in the cardiac cycle, and abnormal sounds, such as murmurs, which result from turbulent flow.
The normal cardiac cycle
The heart is a four-chambered pump. Blood flow to and from the heart is controlled by a series of valves. Contraction of the heart elevates blood pressure, sending blood into the vascular system, which then perfuses the body’s tissues.
The heart has two separate circuits that operate at the same time. Systemic circulation distributes blood to the body
tissues; pulmonary circulation distributes blood to and from the lungs for oxygenation and elimination of carbon dioxide.
Following blood flow through the heart helps one understand the structure of the heart. Blood returning from the body empties into the right atrium. The blood then passes through the right atrioventricular (AV) valve, also known as the tricuspid valve, into the right ventricle.
As the ventricle fills, it begins to contract, raising blood pressure within it and causing the AV valve to close.
Almost at the same instant, the increased pressure cause the pulmonic valve to open, permitting blood to flow into the
pulmonary artery. When the blood is ejected, attempted backflow from the pulmonary artery causes the pulmonary valve to snap shut. Blood pressure in the pulmonary artery is sufficient to force blood through the lung capillaries and back to the heart by the pulmonary veins.
The oxygenated blood collects in the left atrium. The left atrioventricular (AV) valve, also known as the mitral valve, opens, allowing the left ventricle to fill. As the ventricle contracts, the mitral valve snaps shut and the aortic valve opens, allowing blood to eject into the aorta and then be transported to body tissues.
The first sound of the characteristic “lub-dub” pattern of a normal heart is known as S1. This sounds signals the onset of ventricular contraction, which results in vibrations produced with the closure of the mitral and tricuspid valves. The second heart sound (S2) is produced by the closure of the aortic and pulmonic valves, which happens at the termination of ventricular contraction. The third (S3) and fourth (S4) heart sounds occur during ventricular filling and are of a low-enough frequency that they’re not normally heard in the dog.
When they are heard, they may sound like the galloping of a horse and are termed “gallop” sounds. When these sounds are heard, it usually indicates ventricular dilatation with myocardial failure.
Murmurs
Heart murmurs are caused by turbulent blood flow in the heart or adjacent blood vessels. Murmurs are described by their timing within the cardiac cycle, loudness, quality, pitch and degree of radiation over the chest wall. The intensity of a murmur is graded 1 to 4. Very loud murmurs are associated with palpable vibrations on the chest wall known as a “thrill”. The point of maximum intensity usually corresponds to the anatomic origin of the murmur.
The quality and pitch of a murmur relate to its frequency components. “Musical” murmurs are of one frequency, whereas “noisy” or “harsh” murmurs contain mixed frequencies.
Timing the murmur and pinpointing its location will lead to a diagnosis.