Blood Pressure in Hyperthyroid Cats in Comparison to Age Matched Controls Using High Definition Oscillometry

Sakals S. and Carr A.H. (2015). ACVIM Forum. Indianapolis, Indiana: 759.


Hypertension is a common finding in older cats. A variety of underlying reasons for hypertension have been suggested including hyperthyroidism, where it is estimated around 20% are hypertensive at diagnosis. The literature to date has predominantly consisted of studies using Doppler technology where diastolic blood pressures are not determined. In addition these studies did not use an age matched control group to assess the data. Blood pressure was measured using an HDO (S+B MedVet, Babenhausen, Germany) oscillometric device. Tracings were visually evaluated using the provided software to assess the blood pressure curves for quality (adequate amplitudes, lack of significant artifact). Cats were measured with minimal or no restraint with the cuff placed on the tail. A series of readings were taken till at least 3 verified readings were obtained. A total of 42 hyperthryoid and 18 age matched non-hyperthyroid controls were available for analysis. Systolic blood pressure (hyperthyroid mean 158 ± 19 mmgHg; control 154 ± 16 mmHg), diastolic blood pressure (hyperthyroid mean 88 ± 13; control 84 ±12), mean blood pressure (hyperthyroid mean 113 ± 13; control 109 ± 12) and heart rate (hyperthyroid mean 203 ± 39; control 202 ± 24) were not different based on paired T-test. When cat’s blood pressure values were categorized using the ACVIM Consensus Statement values for risk of target organ damage (systolic; mild, 150-159, moderate 160-179, severe > 180: diastolic; mild 95-99, moderate 100-119, severe >120) there was a significant difference between the groups only for systolic blood pressures using chi-square (p = 0.03). According to this classification in the hyperthyroid group there were 8 severe, 8 moderate and 12 mild cases whereas in the control group it was one case of severe, 9 of moderate and 1 of mild. In the hyperthyroid group for diastolic blood pressure 9 moderate and 3 mild cases were present whereas in the control group it was 2 cases of moderate and 1 case of mild. The data shows that as a group older cats and hyperthryoid cats have similar blood pressures with a similar percentage of cats being considered at risk of target organ damage (61% of control cats and 67% of hyperthyroid cats based on systolic blood pressure) however in the hyperthyroid group there is a higher percentage of cats with severe risk of target organ damage. Diastolic risk of target organ damage was more common in the hyperthyroid group (29% vs. 17%), though generally only moderate or mild.