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Severe, pathological bradycardia is an arrhythmic condition where the heart rate is below the normal reference therefore the sufficient blood pressure is not upheld, resulting in symptoms such as weakness and syncope. In dogs, common pathological causes for bradycardia are sinus node dysfunction and AV blocks. These conditions usually require pacemaker as treatment. Pacemaker implantation is a surgery requiring high competence, expensive equipment and patients are often of old age and the summation of these factors causes a smaller motivation for the owner to proceed with the implantation. This results in the need for a medication more easily applicable and lower in cost more sought out for.

Cilostazol is a drug originally intended for human patients with symptoms of intermittent claudation in peripheral vascular disease. It is a phosphodiesterase type 3 inhibitor, where it inhibits platelet aggregation and vasodilating effect by increasing the amount of protein kinase A. As a side effect it produces tachycardia. In some studies, it has shown promising effect in patients presenting with pathological bradycardia, both in humans and in dogs, where the use of the drug has increased and stabilized the heart rate. Despite the clinical success of cilostazol in several human studies, there are very few data (individual cases only) in animals that oral medication can substitute the need for pacemaker implantation or provide less symptoms in the period between diagnosis of bradycardia and scheduled pacemaker implantation.

The purpose of this prospective clinical study is to determine the safety, tolerability and clinical effects of Cilostazol in severely bradycardic dogs due to cardiac disease. Six dogs averaging at 14 years of age (range: 12-15) was presented at the clinic with signs associated with bradycardia, all 6 showed signs of weakness and in addition 4 was presented with syncope. 3 dogs were diagnosed with sick sinus syndrome, 1 with 2nd degree AV block Mobitz II and 2 with 3rd degree AV block, with the use of ECG. Cilostazol was presented for the owners as an alternative drug, without knowing the full- or long-term effect. The dogs was given 10mg/kg Cilostazol b.i.d orally. Follow up were made in frame of regular cardiological examinations. Data were evaluated using descriptive statistics and student’s t-test. All dogs showed increase in heartrate after administration of the drug averaging of 62% significant increase of baseline (p=0,03) and became asymptomatic with no side effects. The average symptom free survival was 14 months (ranging 5-22 months). However, our study population size is limited, we conclude that cilostazol is clinically effective, safe and well tolerated in bradycardia of cardiac origin in dogs with AV block and sick sinus syndrome and may provide an alternative medical option to pacemaker implantation.