Diagnosis of TR is based on the finding of the typical pan or holosystolic plateau-type murmur with a PMI over the TV region, on the right side of the chest (Figure 6.2). These murmurs often have a soft blowing quality. When they are harsh they are more likely to be related to primary TV disease. In some animals with TR, the murmur can also be heard on the left side of the chest cranial to the MV region, usually low down in the second intercostal space.
An important differential diagnosis in the case of a loud pan or holosystolic plateau-type murmur over the TV region is a ventricular septal defect. Typically, the murmur associated with this congenital defect is lower on the chest wall, just above the sternum, has a harsh quality and an associated palpable precordial thrill. These characteristics are, however, dependent on the exact location and size of the defect and on secondary changes (see section 5.5.3).