Cardiovascular responses to isometric handgrip exercise in neurally mediated syncope

Abstract

Background/Aims: Neurally mediated syncope (vasovagal) is characterized by a transient instability of neurocardiovascular reflexes. Changes in posture and physical exercise involve activation of these reflexes. We explore arterial blood pressure (BP), heart rate (HR) and cardiac output (CO) changes occurring during voluntary sustained handgrip (SHG) protocol in patients with vasovagal syncope. Methods: 14 patients with syncope (13 women, aged 31.2 ± 10.4 years), and 30 age-matched healthy subjects (20 women). Diagnosis of vasovagal syncope was based upon clinical criteria. All patients had normal physical examination and normal cardiac evaluation. Orthostatic stress testing was performed with active standing. Valsalva maneuver, baroreflex sensitivity (BRS) and BP, HR and CO changes during sub maximum force (SHG) for 3 minutes were monitored in supine position using FINAPRES. Results: No difference was found in Valsalva ratio between control (1.7 ± 0.3) and syncope group (1.7 ± 0.4) (P = 0.6), BRS was 10.9 ± 2.8 ms/mmHg in controls and 8.6 ± 6.3 ms/mmHg in syncope group (P = 0.007). During SHG, both healthy and syncope groups show significantly BP and CO increases, while HR increased in healthy subjects but did not increase significantly in syncope patients. Conclusion: In syncope patients, the increase in BP with blunted HR change during SHG suggests an abnormal modulation of vagally-mediated cardiac baroreflex responses.