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  Dogs' hearts work the same as humans'. There are four chambers, two atriums and two ventricles, one each on the right and the left. The two atriums are the upper two chambers, while the ventricles are the lower two chambers. There are valves that connect the chambers of the heart to ensure the blood flows in the proper direction.
  
  

Congestive Heart Failure

• Congestive heart failure is what happens when your heart gets enlarged. When there are issues within the heart, this is typically how it ends. X-rays and ultrasound are used to diagnose congestive heart failure, as the enlarged heart shows up clearly. This condition is treated with drugs.
  
  

Mitral Valve Failure

• The valve that is located between the left ventricle and the left atrium is called the mitral valve. This is typically the first valve to wear out due to the fact that the pressure on this valve is higher than any other. The left ventricle has to push hard to circulate the blood through the body, and the mitral valve has to stop that blood from going backwards into the atrium. Treatment is based on the individual dog and can include medications, diet and/or limited exercise.
  
  

Cardiac Arrhythmia

• Cardiac arrhythmia is the medical term for an abnormal heart beat. Blood work will help to pinpoint some irregularities that are consistent with this condition, in order to provide a correct diagnosis. Hypothyroidism is one disease that can contribute to cardiac arrhythmia also. Depending on the severity of the arrhythmia, as well as any other diseases present, treatment may include medication or electric shock therapy. With very mild cases, it's best left alone.