You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

When communicating with professional colleagues it is useful to be familiar with terminology in common use when describing cases. The Mobitz sub-classification system is used to described different types of second degree heart block.

Heart block can be first degree  - when there is a delay in electrical conduction through the atrioventricular node and a prolonged PR interval is found on ECG examination.

It can also be second degree - when the electrical conduction does not pass through the atrioventricular node resulting in a P wave without a subsequent QRST complex on ECG examination.. There are 2 sub-categories of second degree heart block :

• Mobitz Type I - The PR interval increases prior to the block . Usually the duration of the QRS complexes on the ECG  is normal and the block is believed to occur above the division of the bundle of His (known as Type A heart block)
• Mobitz Type II - The PR interval remains constant prior to the block. Usually the QRS complexes on ECG are prolonged and this is thought to be caused by a block below the division of the bundle of His. In these cases the block may occur on a regular basis eg every 2nd or 3rd complex.

Last updated : October 2013