Heart murmurs are the most common type of congenital dog heart health problem, which is noted because of
turbulent blood flow in the heart.
This is often also associated with some degree of mitral regurgitation, and these causes
of turbulent blood flow account for the systolic murmur audible in some cats with HCM.
Most often animals are referred to our veterinary cardiology specialists for a heart murmur (an abnormal heart sound that usually
indicates turbulent blood flow) or clinical signs that may indicate cardiac disease (such as exercise intolerance, lethargy, persistent cough, difficulty breathing, collapse, or swollen abdomen or limbs).
Murmurs are caused by
turbulent blood flow such as when the structure of the heart undergoes changes and does not allow for regular laminar blood flow.
Heart murmurs are «swooshing» sounds created
by turbulent blood flow and are most commonly associated with diseases that affect the heart valves such as degenerative valve disease, AV valve dysplasia, pulmonic stenosis however, disease that do not primarily affect the valves such as dilated cardiomyopathy may secondarily cause a murmur by stretching apart the valve leaflets causing them to leak as the heart enlarges.
Such murmurs usually develop secondary to
turbulent blood flow.
Thickening of the myocardium per se does not cause
turbulent blood flow, hence many cats with HCM do not have a heart murmur.
Chihuahuas are also prone to some heart related disorders such as heart murmurs, i.e., extra heart sound produced due to
turbulent blood flow and Pulmonic Stenosis in which the blood outflow from the heart's right ventricle is obstructed at the pulmonic valve.
A heart murmur is when extra vibrations are produced due to
turbulent blood flow or because of vibrations of the heart structure, such as part of a valve.
Examples are: dogs with chronic heart failure or cats with cardiomyopathy, where
the turbulent blood flow may increase the likelihood of development of endocarditis; and dogs with chronic kidney or hepatic failure, where metabolic instability may produce a secondary immunopathy or where septic vascular aggregates may exacerbate the systemic disease.
The short answer to this question is «
turbulent blood flow.»