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Summary Blood pressure was measured under practical conditions as found in the treatment room by means of comparing the doppler technique with the oscillometric technique. By comparing the results of 254 measurements of blood pressure in 141 cats it turned out that the oscillometric working device tended to underestimate systolic values of blood pressure, when compared to the results obtained by the doppler working device. This underestimation increased with increasing blood pressure. The closest match of systolic blood pressure between both techniques was found in the median part of the doppler pressure range, this being 111 mmHg to 160 mmHg. In this scope, 88 % (n = 132) of measured values did not deviate more than 20 mmHg. 69 additional 'measurements of blood pressure with the oscillometric technique offered no results. Under clinical conditions and in order to diagnose a hypertension the doppler turned out to be the more reliable method to measure blood pressure in cats. Therefore only the systolic blood pressure values resulting from the use of the doppler were used in further evaluations. It is very likely that stress caused by the examination may result in filsely elevated blood pressure. In order to objectify the results, blood pressure in 136 cats was taken over a time span of 5 to 10 minutes, thus objectifying the results. While the measurements were taken, the majority of animals (88 %) relaxed and their blood pressure decreased on average by 32 mmHg. Nevertheless, some animals (13 %) got increasingly stressed during the measurements and their blood pressure increased on average by 28 mmHg. The normal blood pressure value was determined in 20 healthy cats under conditions as found in the treatment room. Systolic readings ranged from 100 to 160 mmHg, the average value being 126 mmHg. In order to be able to analyse the blood pressure in all 300 cats from the pool of patients, consisting of 180 male and 120 female cats of different breed and age, the systolic value of blood pressure for hypotension was defined below 100 mmHg, for normotension between 100 to 169 mnnIlg, for a mild hypertension between 170 mmllg to 199 mmllg, and for a severe hypertension above 200 mmHg. Hypotension occurred in 4 % of the examined cats, normotension in 53 %, a mild hypertension in 15 % and a severe hypertension in 28 % of the patients' pool. No breed or sex predisposition could be detected, however, increasing blood pressure correlated with a increase of age. While cats up to the age of ten generally showed normotension ( 76 %, n = 105), they developed a hypertension from the age of eleven years onwards ( 64 %, n = 104). According to their cardiological condition, that is the T4-serum-concentration, all patients were divided into eight groups: In 52 cats, no heart dysfunction was diagnosed (Group I), 22 cats were suspected of having a heart condition (Group II), 119 animals were diagnosed with hypotrophic CMP (Group III), 15 cats were diagnosed with restrictive CMP (Group IV), six patients were diagnosed with dilated CMP (Group V), 59 patients had unclassified CMP (Group VI), eleven patients had a congenital heart condition (Group VII), and 16 cats were diagnosed with hyperthyreodism (Group VIII). Hypertension appeared in group III in 64 % of the cases, in group VIII in 56 % of the cases, in group IV in 40 % of the cases, in group VI in 36 % of the cases, in group II in 36 %, in group VII in 27 %, in group V in 17 %, and in group I in 8 % of all cases. The cause for hypertension in 82 of 118 hypertensive cats regarding to blood chemistry was a limited renal function, and in nine cats of group VIII hyperthyreodism. In two further examined cats diabetes mellitus is thought to be the cause of their high blood pressure. Unknown causes of hypertension in lab-diagnostically examined cats occurred in 25 patients. As an obvious consequence of high blood pressure, 36 % (n = 46) of the hypertensive cats showed a hypertensive retinopathy. The average age of these animals was 14 years, their average blood pressure had the systolic value of 262 mmHg. Hypertensive retinopathy occurred more frequently with increasing blood pressure. Blood pressure curves of 62 hypertensive patients under antihypertensive treatment were also observed. While 18 cats were treated with the calcium channel antagonist Amlodipine, or an ACE inhibitor as mono-therapy, 26 cats were administered with an Amlodipine ACE inhibitor combination. The antihypertensive therapy of the animals was not very successful using an ACE inhibitor. In most cases, blood pressure remained unchanged. Only in three animals, blood pressure decreased by 20 to 40 mmHg. In one animal, blood pressure even increased by 20 mmHg. Patients treated with Amlodipine reached an average systolic decrease in blood pressure of 102 mmHg, while patients treated with a combination of Amlodipine and ACE- inhibitors reached an average systolic decrease in blood pressure of 99 mmHg. 83 % (n = 15) of the patients treated with Amlodipine, and 73 % ( n = 19) of the patients treated with the Amlodipine ACE inhibitor combination, reached a normotension. The results of the examination conclude that neither a monotherapy with an ACE inhibitor results in a satisfying decrease in blood pressure, nor does the ACE inhibitor enhance the decrease in blood pressure of Amlodipine when given in combination.