Category Archives: Veterinary Medicine

Investigation Of The Cardiovascular System

History As always, the animal’s vaccination status, past medical history, diet and details of any previous or present treatment (including the response to any treatment given) should be recorded. Dogs, and to a lesser extent, cats in heart failure often present with a history of coughing. In most cases this is due to pulmonary venous… Read More »

Radiological examination

Thoracic radiographs are essential in the evaluation of animals with suspected heart disease. Changes in the cardiac silhouette and lung fields provide direct information about the heart size, the condition of the lungs and volume load in the circulation. Thoracic radiography may facilitate or confirm a diagnosis suspected on the basis of physical examination, help… Read More »


An electrocardiogram provides a graphic record of the voltage produced by cardiac muscle cells during atrial and ventricular depolarization and repolarization plotted against time. The electrical forces produced possess both direction and magnitude and can therefore be regarded as true cardiac vectors. The cardiac or mean electrical axis (MEA) represents the summation of many different… Read More »

Cardiac murmurs

Cardiac murmurs are caused by alterations in blood flow through the heart or its major outflow tracts which produce turbulence. It is important to record details of a murmur for comparison with later observations (possibly by a different clinician) which may in turn correlate with an altered clinical presentation. The criteria used to characterize a… Read More »

Heart Failure

The cardiovascular system has enormous compensatory reserves and heart failure only occurs when the reserve capacity is overwhelmed. Cardiovascular reserves Venous oxygen reserves. The normal end-capillary or venous oxygen tension is 30-50 mm Hg. Providing this figure remains greater than 30 mm Hg increased oxygen can be extracted by the tissues as the demand for… Read More »

Pathophysiology of heart failure

Heart failure, by definition, occurs when cardiac output is insufficient to provide the tissues with adequate blood flow and / or when the venous return to the heart is greater than the amount of blood that the heart can expel at normal filling pressure. Most animals with heart failure show signs of both forward and… Read More »

Compensatory mechanisms in heart failure

The normal physiological mechanisms regulating the cardiovascular system are primarily concerned with the maintenance of arterial blood pressure which is adequate for cerebral perfusion. A fall in cardiac output and therefore arterial blood pressure will activate the following neurohormonal systems: 1. The sympathetic nervous system 2. The renin-angiotensin-aidosterone system 3. The renal body fluid system… Read More »

Adaptive consequences of sustained neurohormonal activation

If the neurohormonal compensatory mechanisms are activated for sustained periods of time, adaptive changes in the heart and circulation ensue which tip the balance away from compensation towards uncontrolled salt and water retention, vasoconstriction, and the detrimental consequences which lead Co clinical congestive heart failure. The myocardium Prolonged ventricular distension leads to a loss of… Read More »

Causes and clinical signs of congestive heart failure

The clinical signs of congestive heart failure (CHF) are a direct consequence of volume overload. A large regurgitant fraction is required before signs of congestive heart failure become apparent. With mitral incompetence, the rate at which progression occurs depends on the size of the regurgitant traction and also the compliance (distensihility) of the left atrium.… Read More »