Cardiology is about heart conditions. Not all heart disorders actually cause clinical signs but some of them can be fatal.
There are various ways to assess a heart for problems. The clinical history can be important as many animals with heart problems present with a moist, retchy cough that is often worse after periods of lying down. Other signs include reduced exercise tolerence, heavy breathing or abnormal mucus membrane colour. During a clinical examination a heart murmur may be detected along with pulse deficits (a heart beat being heard but no pulse for the beat being detected). Sometimes an arrythmia (abnormal rhythm) may be detected.
Further investigations may be recommended and these might include a chest x-ray, an electrocardiogram (ECG) and/or an ultrasound of the heart.
We have a modern ECG machine (see pictures above) that is capable of detecting abnormal electrical rhythms from the heart. Ultrasound can be used to measure the size of the heart, watch how well the chambers contract as well as looking for structural abnormaliities.
X-rays may be used to assess how big the heart appears as well as giving a lot of information about the lungs.
Cardiology is about heart conditions. Not all heart disorders actually cause clinical signs but some of them can be fatal. 
There are various ways to assess a heart for problems. The clinical history can be important as many animals with heart problems present with a moist, retchy cough that is often worse after periods of lying down. Other signs include reduced exercise tolerence, heavy breathing or abnormal mucus membrane colour. During a clinical examination a heart murmur may be detected along with pulse deficits (a heart beat being heard but no pulse for the beat being detected). Sometimes an arrythmia (abnormal rhythm) may be detected.