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Heartworm Disease, Cat 415

of the heart cycle (continuous). Murmurs noisy breathing, respiratory distress, or anxiety, increased radiographic vertebral heart score
are also described as being early, middle, the breath sounds may be confused with heart together with a murmur is usually a good
VetBooks.ir characterized by their musical quality or or upper respiratory system during auscultation PROGNOSIS & OUTCOME Diseases and Disorders
or late (within systole or diastole) and are
indication of the severity of the cardiac disease.
murmurs because of the noise from the thorax
tone, such as high frequency, midrange, or
and physical exam.
low frequency. Although not always true,
in some cardiac diseases the intensity of the Initial Database Highly variable depending on the underlying
murmur can correlate with the severity of the Depends on the context in which the murmur cause of the murmur. The prognosis of a
disease. Other cardiac diseases may not have a is noted (see History, Chief Complaint above): patient with a heart murmur is influenced by
murmur, and the absence of a murmur does • Second opinion auscultation: to confirm or the disorder causing the murmur, not by the
not rule out the presence of cardiac disease. refute the presence of the murmur if unclear murmur itself.
• Thoracic radiographs: diagnostic test of
Etiology and Pathophysiology choice for left-sided congestive heart failure PEARLS & CONSIDERATIONS
• Systolic murmurs are associated with (pulmonary edema)
congenital conditions such as aortic stenosis, ○ Moderate and advanced states of heart Comments
pulmonic stenosis, septal defects, atrioven- disease can alter the shape and size of • For dogs that are panting, anxious, sniffing,
tricular valve dysplasia, tetralogy of Fallot, the cardiac silhouette in a way that is or whining, closure of the mouth and inter-
and other, less common congenital lesions. diagnostically useful. mittent occlusion of the dog’s nostrils for 2-3
• Acquired systolic murmurs are auscultated ○ Radiographs are very useful for establish- seconds at a time is useful for intermittently
with mitral or tricuspid degenerative valvular ing a baseline in dogs if myxomatous or masking breath sounds that interfere with
heart disease (insufficiency), cardiomyopa- degenerative mitral valve disease is the auscultation of the heart.
thies, anemia, fever, hyperthyroid disease, most likely cause of the murmur. Absence • For cats, the sound of running water or
heartworm disease, endocarditis, and diastolic of cardiomegaly in these dogs suggests scruffing (lifting the skin of the nape of
dysfunction syndromes. early disease and no justification for the neck) helps abolish purring.
• Diastolic murmurs in small-animal veterinary treatment (p. 658). • A systolic whoop is an uncommon but
medicine are unusual but are associated with • Echocardiography: diagnostic test of choice loud musical systolic murmur produced
mitral stenosis, aortic valvular insufficiency, for pinpointing the cardiac lesion responsible by resonance of the mitral valve. It may
and pulmonic valvular insufficiency. for the murmur appear or disappear spontaneously and is
• Continuous murmurs are heard with PDA • CBC, serum chemistry panel, urinalysis, not related to the presence or severity of any
or atrioventricular vascular shunting lesions abdominal imaging: as indicated for possible underlying heart problem, although further
on the left thorax (PDA) or in the peripheral concurrent systemic disorders monitoring is indicated. Usually, dogs with
vascular system. • Cardiac biomarkers (particularly NT-pro-BNP systolic whoops ultimately develop murmurs
[p. 1369]): NT-pro-BNP level may have associated with valvular heart disease over
DIAGNOSIS significance in correlating with the severity time.
of cardiac disease. NT-pro-BNP testing may
Diagnostic Overview be useful to screen murmur significance in Technician Tips
By definition, a heart murmur is detected asymptomatic cats or for distinguishing respi- Optimal auscultation is done with the patient
during auscultation of the heart. Knowing ratory signs caused by CHF from primary in a standing position. In recumbent patients,
the cause of the murmur is important for respiratory disease in the feline. shifting of the heart may alter the perceived
therapeutic and prognostic reasons, and the point of maximal intensity and alter intensity
need for diagnostic testing is determined by the TREATMENT of the murmur.
rest of the physical exam and discussion with
the pet’s owner regarding the advantages and Treatment Overview SUGGESTED READING
drawbacks of performing such tests. A global Treatment of heart murmurs is not an option. Prosek R: Abnormal heart sounds and heart murmurs.
approach to diagnosis and management is The veterinarian must first identify the murmur, In Ettinger SJ, et al, editors: Textbook of veterinary
outlined on p. 1422. then the cause of the murmur, and then make internal medicine, ed 8, St. Louis, 2017, Elsevier,
associations with the disease/condition present. pp 220-224.
Differential Diagnosis A murmur does not mean the animal requires
Heart murmurs must be differentiated from therapy. The intensity of the murmur usually AUTHOR: Stephen J. Ettinger, DVM, DACVIM
EDITOR: Meg M. Sleeper, VMD, DACVIM
breath sounds. In animals with particularly is directly related to the severity of the disease;

Heartworm Disease, Cat Client Education
Sheet

BASIC INFORMATION pulmonary thromboembolism (PTE), and • There is no age predisposition.
uncommonly, pulmonary hypertension (PH) • Male cats generally have an increased risk
Definition with/without cor pulmonale and rarely conges- of exposure and have higher experimental
Heartworm disease (HWD) is the clinico- tive heart failure (CHF). infection rates and worm burdens than
pathologic manifestation of infestation with Epidemiology females.
Dirofilaria immitis, an intravascular parasite • Prevalence of heartworm infection (HWI)
that resides in the pulmonary arteries, the right SPECIES, AGE, SEX in cats is estimated to be 5%-15% that of
side of the heart, and venae cavae. Infestation • Felids are atypical hosts for this canine unprotected dogs in the same area.
results in pneumonitis, pulmonary endarteritis, parasite.

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