Abstract: Background: Feline systemic arterial hypertension (SHT) is associated with a wide spectrum of left ventricular (LV) geometric patterns as well as diastolic, and to a lesser extent, systolic myocardial dysfunction. However, little is known about SHT-related cardiac changes in dogs. Hypothesis: SHT in dogs is responsible for morphological and functional cardiac alterations. Animals: Thirty dogs with spontaneous untreated SHT and 28 age- and body weight-matched healthy dogs as controls. Methods: Prospective observational study. Conventional echocardiography and 2-dimensional color tissue Doppler imaging were performed in SHT dogs by trained observers and compared with controls. Results: Forty-seven percent of SHT dogs (14/30) had diffuse concentric hypertrophy. None had left atrial dilatation and 10/30 (33%) had aortic insufficiency (AoI) associated with proximal aortic dilatation. Longitudinal diastolic left ventricular free wall (LVFW) motion was altered in all SHT dogs at the base (early to late diastolic wave ratio, E/A=0.50.1 versus 1.30.3 for controls, P<.0001) and the apex (E/A=1.61.7 versus 3.93.1, P<.05). Longitudinal motion of the interventricular septum at the base (E/A=0.70.4 versus 1.10.1, P<.01) and radial LVFW motion in the subendocardium (E/A=0.90.5 versus 1.60.3, P<.01) were also altered in dogs with SHT. Longitudinal LVFW systolic velocities and gradients were also significantly decreased ( P<.05) in SHT dogs. Conclusion and Clinical Importance: As in SHT in cats, SHT in dogs is associated with myocardial dysfunction independently of the presence of myocardial hypertrophy. However, unlike feline SHT, it results in a homogeneous LV geometric pattern with a relatively high prevalence of AoI.