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Hypersensitivity of the carotid sinus corresponds to a ventricular pause equal to or exceeding 3 seconds and/or a blood pressure drop equal to or exceeding 50 mmHg, induced by massage of the carotid sinus (MCS). MCS remains the diagnostic method of these two syndromes: cardio-inhibitor/vasodepressor. It must be performed systematically during the work-up of transient consciousness disorders since it is not unusual that hypersensitivity of the carotid sinus may cause cardiac syncopes. In addition, hypersensitivity of the carotid sinus is often associated with sinus dysfunction and atrioventricular conduction disorders. In the case of hypersensitivity of the carotid sinus with syncope secondary to a pure or dominant cardio-inhibiting response, heart stimulation with a dual-chamber pacemaker is probably the best treatment. In cases of hypersensitivity of the carotid sinus without syncope, therapeutic abstention is commonly accepted.

The authors have endeavoured to determine which of the parameters commonly used for His bundle ablation are likely to predict that ablation will be effective in altering the atrioventricular (AV) conduction system durability. His bundle ablation was performed in 18 patients (9 men, 9 women; mean age 47 years) presenting with supraventricular tachycardia refractory to all medical treatments. A total of 29 shocks were delivered with an Odam fulgurator, using a distal electrode connected to the positive pole of a selected catheter. Fifteen shocks were effective, resulting in a complete and permanent AV block (group I); the remaining 14 shocks failed to modify permanently the AV conduction system (group II). The parameters which differed between these two groups were the amplitude and the stability of the His bundle potential, the energy per kg bodyweight delivered with the shock and the possibility to shock the potential with the greatest amplitude in case of instability. A discriminant linear analysis showed that 3 interrelated criteria could be used to classify 83% of the shocks into one or the other group. In order of importance these criteria were: (1) amplitude of the His bundle potential; (2)energy delivered per kg bodyweight, and (3) stability of the potential. The corresponding discriminant values for successful results were more than 300 mV for parameter 1, more than 3 J/kg bodyweight for parameter 2 and very good stability of His bundle potential.