Introduction

• Cardiac murmurs are audible sounds that:
  • Occur during the cardiac cycle.
  • Result from turbulence in laminar blood flow or vibration of certain cardiac structures (chordae).
• Blood flow turbulence may develop for a number of different reasons:
  • When blood flow velocity increases.
  • When blood passes through a narrowed vessel or narrow orifice, with a high velocity.
  • When a jet of regurgitant blood strikes a chamber or vessel wall.
• While intrathoracic blood flow turbulence generates the majority of audible vibrations detected on clinical examination, it is also possible for peripheral vascular abnormalities, eg arteriovenous fistulas, to produce blood flow turbulence and similar audible vibrations (called 'bruits' or 'hums').
• Cardiac murmurs are distinct from the normal heart sounds caused by passive valve closure and should also be distinguished from systolic clicks, gallop rhythms, and normal and abnormal respiratory sounds.
• Murmurs may be:
  • Innocent.
  • Physiological/functional.
  • Pathological.
• Innocent murmurs: frequently heard in young animals and may disappear by maturity. They may be more common in mature dogs than previously reported, especially in certain breeds.
• Physiological/functional murmurs: may be heard in association with anemia, tachycardia, pyrexia.
• Pathological murmurs: may be caused by congenital cardiac disease Congenital heart disease: overview:
  • Patent ductus arteriosus Patent ductus arteriosus.
  • Pulmonic stenosis.
  • Aortic stenosis.
  • Septal defect.
  • Atrioventricular regurgitation.
• Or acquired cardiac disease:
• • Degenerative valvular disease.
  • Endocarditis.
  • Dilated cardiomyopathy.

Print off the owner factsheet on Heart murmurs Heart murmurs to give to your client.

Characterization of murmurs

Abnormal heart sounds

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Pouchelon J L, Chetboul V, Devauchelle P et al (1997) Diagnosis of pulmonary thromboembolism in a cat using echocardiography and pulmonary scintigraphy. JSAP 38 (7), 306-310 PubMed.
• Pion P D, Kittleson M D, Thomas W P et al (1992) Clinical findings in cats with dilated cardiomyopathy and relationship of findings to taurine deficiency. JAVMA 201 (2), 267-274 PubMed.
• Jacobs G, Hutson C, Dougherty J et al (1986) Congestive heart failure associated with hyperthyroidism in cats. JAVMA 188 (1), 52-56 PubMed.
• Harpster N K (1977) Clinical examination of the feline cardiovascular system. Vet Clin North Am 7 (2), 241-256 PubMed.