This will lay the foundation for your differential diagnosis list. If a murmur is identified it is essential to grade, localize and time the murmur wherever possible. Small headed stethoscopes (pediatric, neonatal) can enable better localization of sounds and auscultation with both the diaphragm and bell head of the stethoscope may enable clearer detection of a wider range of sound frequencies. Auscultation should include listening to several sites on the thoracic wall (apical and basilar cardiac regions, left and right) again this may be challenging with small puppies. Understanding cardiac anatomy and physiology can assist with localization and timing of murmurs.
Options include lifting the animal from the table and cradling in your arms with the stethoscope placed on the chest (Figure 1), or giving the puppy a brief feed and then allowing it to relax with the owners before attempting again (as they often then fall asleep). Auscultation of puppies can be challenging they can be wriggly, noisy and very non compliant, and it may be necessary to try and calm the puppy to enable better examination. How do I diagnose a murmur in a puppy?Īuscultation is a skill learnt during veterinary training, but is honed with practice. Importantly, note the breed signalment can be useful in guiding you towards a differential diagnosis, although the rules are not absolute. Note if there have been any other concerns with the littermates or whether either of the parents were reported as having heart disease or a murmur. Check if the puppy has been wormed appropriately for lungworm and heartworm prophylaxis (in countries where this is prevalent). Should you suspect a murmur, pay particular attention to the cardiovascular history, including exercise tolerance, resting respiratory rate/effort and any coughing.
What is important in the history and signalment?Įven in routine health check/vaccination appointments, a thorough history must be taken. However, over time chronic overload of the right side can increase right-sided pressures until they equate and then surpass left-sided pressures, resulting in a right to left shunt this may translate into a dramatic worsening of clinical signs but with loss or significant reduction in the murmur. Furthermore, some shunts will originate left to right, with the high-pressure differential between the systemic and pulmonary circulations. Movement of blood between two low pressure systems will not create a murmur loud enough to hear, for example with an atrial septal defect. It is important to note that shunting of blood through defects may not always cause a murmur. The key is the difference in pressure across two chambers for example, a mitral regurgitation forces blood into the low pressure left atrium (approximately 10 mmHg) from the high pressure left ventricle (approximately 120 mmHg) in systole, therefore moving blood with an overall pressure difference of 110 mmHg and causing local tissue vibrations which translate into a detectable sound. Blood must move at high velocity to produce turbulence or a regurgitation which creates a murmur loud enough to detect. Murmurs are sound waves created by vibrations caused by turbulent or regurgitant blood flow in the heart or nearby vasculature (the chamber walls, valves and walls of blood vessels).
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