Aorto-septal angle, isolated basal septal hypertrophy, and systolic murmur in 122 cats

Systolic murmurs in the absence of cardiac structural abnormalities are common in cats. Narrow aorto-septal angle (AoSA) and septal remodeling can be a cause of a systolic murmur in elderly human beings. The aim of this study was to measure the AoSA in cats and to investigate the association between the AoSA and the presence of a murmur and isolated basal septal hypertrophy (IBSH).

The study population comprised 122 cats.

A physical exam, blood pressure measurement, chest radiographs, and echocardiography were performed.

A systolic murmur was audible in 39/122 cats. A difference between cats with and without a murmur was found for age (P=0.0001), interventricular basal septal thickness (BIVSd) (P=0.004), AoSA (P=0.003), aortic (P<0.0001), and pulmonic (P=0.021) flow velocity, the presence of IBSH (P<0.0001), and systolic anterior motion of the mitral valve (P=0.0002). More than 50% of cats with a murmur had an AoSA ≤122°. Less than 25% of the cats with an AoSA ≥137° had a murmur. The AoSA narrowed 0.55°/year of age (P<0.001), whereas the BIVSd increased 0.11 mm/year of age (P<0.0001); the BIVSd increased as the AoSA narrowed. In all cats with AoSA < 120°, IBSH was present.

This study demonstrates that the probability of having a systolic murmur in cats is increased by the presence of a narrow AoSA. Aging was associated with a narrower AoSA and a thicker basal septum; these findings might represent an age-related heart remodeling.