Key result
Patients with neurally mediated reflex syncope exhibit higher night-time SBP variability and lower daytime SBP.
Why the study?
Does ambulatory blood pressure monitoring and heart rate variability analysis identify autonomic dysfunction in patients with neurally mediated reflex syncope?
Case-Control (n=100)
No
Does ambulatory blood pressure monitoring and heart rate variability analysis identify autonomic dysfunction in patients with neurally mediated reflex syncope?
Absolute Event Rate: 12.4% vs 9.56%
p-value: p=0.004
Ambulatory blood pressure monitoring may be useful for diagnosing neurally mediated reflex syncope by identifying inadequate circadian rhythm in blood pressure variation.
May support ABPM for autonomic assessment in reflex syncope; hypothesis-generating and requires prospective validation before practice change.
Background: In the present study we investigated autonomic dysfunction using hemodynamics and analysis of heart rate variability (HRV) following ambulatory blood pressure monitoring (APBM) in patients with neurally mediated reflex syncope (NMRS). In addition, we evaluated the usefulness of ABPM for diagnosing NMRS. Methods: In all, 88 consecutive patients with syncope and 12 controls (Group C) were subjected to a head-up tilt (HUT) test (80°, 30 min). If no syncope or presyncope occurred, the HUT test was repeated in the patient group following drug loading (ATP, isoproterenol, and/or isosorbide dinitrate). Results: Forty patients had a positive HUT test, with or without drug loading (Group P) ; the HUT test was negative in 48 patients, even after drug loading. Average daytime systolic and diastolic blood pressure (SBP and DBP, respectively) was significantly lower in Group P than in Group C (P = 0.042 and P = 0.047, respectively). The average standard deviation of SBP at night (SD-SBPNight) was significantly higher in Group P than in Group C (P = 0.004). HRV analysis revealed a significantly higher daytime high-frequency component in Group P than in Group C (P = 0.041). Conclusion: The results of the present study suggest that lower daytime blood pressure and a larger SD-SBPNight, as determined by ABPM, are associated with vagal nerve hyperactivity and sympathetic hypoactivity in patients with NMRS. Thus, an inadequate circadian rhythm in blood pressure variation, as identified by ABPM, may be useful for the diagnosis of NMRS.
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Onishi et al. (2014) conducted a case-control in Neurally mediated reflex syncope (n=100). Neurally mediated reflex syncope (positive head-up tilt test) vs. Healthy controls was evaluated on Standard deviation of night-time systolic blood pressure (SD-SBPNight) (p=0.004). Patients with neurally mediated reflex syncope exhibited significantly higher night-time systolic blood pressure variability (12.4 vs 9.56 mmHg, p=0.004) and lower daytime systolic blood pressure compared to healthy controls.
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