Syncope recurrence in pacemaker-implanted subjects for the cardio-inhibitory response to sinus carotid massage (SCM) was investigated. The study-hypothesis was that recurrences had significant vasodepressor responses that could justify the loss of consciousness. Forty-six patients were enrolled (16 patients and 30 controls), followed and revaluated after 5–7 years. At the end of follow-up, significant differences were found between patients and controls in mean SCM SAP (87 versus 106？mmHg) and reduction in mean SCM SAP (59 versus 38？mmHg); in the number of symptomatic subjects soon after SCM (5 versus 1); and in the number of subjects suffering from orthostatic hypotension. A subgroup of 13 patients showed significantly different hypotensive responses to SCM compared with the values observed at study recruitment. The data showed that some subjects with a defined hemodynamic pattern in response to SCM may change their characteristics and have spontaneous and/or provocative symptoms. These data explain the syncopal relapses, and suggest the presence of autonomic dysregulation in individuals with carotid sinus hypersensitivity. 1. Introduction Carotid sinus hypersensitivity (CSH) is the response manifested with bradycardia and/or hypotension during sinus carotid massage (SCM). CSH has been classified as “cardio-inhibitory” (asystole >3？s), “vasodepressive” (if systolic arterial pressure (SAP) falls to >50？mmHg), or “mixed” forms [1]. The effect of SCM may be not only upon cardiovascular parameters but also on symptoms. Hence, the appearance of symptoms during SCM and their characteristics are the most important signs for appropriate and efficacious therapy. Attention has recently been focused upon differences between CSH and carotid sinus syndrome (CSS). CSS is diagnosed in the presence of symptoms, syncope, or presyncope, during or soon after SCM [2]. Dual-chamber pacing (DDD) is the treatment of choice for cardioinhibitory and mixed forms. It is believed to improve quality of life by reducing the number of episodes of recurrent syncope, but it does not completely eliminate the risk of syncope recurrence [3], especially in patients with vasodepressive effects [4, 5]. It is known that patients with CSH showing a reduction in blood pressure after an SCM have a worse prognosis than those with a pure cardioinhibitory response or a lack of vasodepressor response [1, 4]. Hence, the aim of this study was to assess if patients treated with cardiac pacing for cardio-inhibitory CSH with recurrent syncope had a prevalent vasodepressor response that could justify
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