Heart Failure, Diagnosis

A number of diagnostic procedures need to be taken into account when diagnosing heart failure.

History & Clinical Signs

Coughing, dyspnea, tachypnea, orthopnea, exercise intolerance, syncope, lethargy, peripheral oedma, ascites, mucous membrane colour and weight loss are all clinical signs that may be caused by heart disease, but may also have other causes. There may also be a capillary refill time of less than 3 seconds, which is normal. Over 3 seconds is abnormal. Pale mucous membranes suggest poor peripheral circulation due to vasoconstriction, decreased hemoglobin in the blood (anaemia), or shock. Cyanosis suggests adequate hemoglobin, but inadequate oxygenation. This can be seen with pleural effusion/pulmonary oedema - right to left shunt within the circulation causing deoxygenated blood to mix with oxygenated blood.

Signs of heart failure are directly related to which side is affected. The above signs are characteristic of cardiac problems, but can also be the signs of other diseases involving different body systems therefore a good physical exam including signalment, history, observation, palpation, percussion, and auscultation are necessary to identify true cardiac problems.

Physical Exam

Observation

Clinical signs as described above.

Palpation

Precordium: (Left side of the chest behind the elbow where heart contractions are easily palpated and auscultated). Heart rate, rhythm, character, apex beat and palpable thrill can all be detected here. 

Pulse: (rate, rhythm, character). Dog: Femoral pulse; palpate heart, Horse: External maxillary/ facial artery; transverse facial artery; median artery; digital artery; metatarsal artery, Cattle: external maxillary/ facial artery; middle coccygeal artery; median artery. 

Pulse Deficits (seen with arrhythmias)

Jugular pulses and/or jugular venous distension and/or enlarged ventral abdominal veins (indicates high venous pressure).

Abdomen: pitting oedema, ascites, splenomegaly, hepatomegaly and fluid thrill (fluid movement causes a palpable vibration).

Percussion

A method of diagnosis performed by flicking a body part with fingers and the resulting sound helps determine size, position, and density of the underlying structures. The thorax will have a lack of resonance if the lung has solidified and you will be able to detect a fluid line. The abdomen will show a fluid thrill on percussion.

Auscultation

A method of diagnosis performed by listening to sounds inside the body. Auscultation can be performed with or without a stethoscope. Abdominal, cardiac, pulmonary, and thoracic auscultation can all be performed. Cardiac auscultation is used to listen to heart sounds and heart murmurs.

Heart Sounds:

These differ with different species. In the dog and cat normal heart sounds are S1 (closure of atrioventricular valves; heard best at left heart apex) and S2 (closure of semilunar valves; heard best at left heart base); Lub-Dup sound. Abnormal Heart Sounds: S3 & S4 occur during diastole and should not be audible in dogs and cats. If either one is present, this is called a GALLOP RHYTHM and suggests poor ventricular filling. Du-Lub-Dup sound.

In the horse normal heart sounds are S1 & S2, S3 & S4; S3 is audible in many horses and marks the end of ventricular filling.

In the bovid, normal heart sounds are S1 & S2, S4; Healthy farm animals do not have an audible S3 as in the horse.

Heart Murmurs are abnormal heart sounds due to turbulent blood flow. Heart murmurs are characterized based on their timing, location, intensity, radiation, pitch, and shape.

Electrocardiography (ECG)

This can be used to recognise conduction problems or arrhythmias but is not needed in the diagnosis of heart failure.

Radiology

Will show cardiac enlargement +/- right-sided heart failure signs, which are ascites, hepatomegaly and pleural effusion and left sided heart failure signs which are pulmonary oedema and pulmonary venous distension.

Echocardiography

Can be used to determine the cause of heart failure, such as structural deformities etc.

References

Andrews, A.H, Blowey, R.W, Boyd, H and Eddy, R.G. (2004) Bovine Medicine (Second edition), Blackwell Publishing

Blood, D.C. and Studdert, V. P. (1999) Saunders Comprehensive Veterinary Dictionary (2nd Edition) Elsevier Science

Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition) W.B. Saunders Company

Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2) W.B. Saunders Company

Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition) Mosby Elsevier

Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial

Nelson, R.W. and Couto, C.G. (2009) Small Animal Internal Medicine (Fourth Edition) Mosby Elsevier

Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses Elsevier Health Sciences

Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) Equine Internal Medicine (Third Edition), Saunders