Postural Heart Rate Changes in Young Patients With Vasovagal Syncope

Area of Science:

• Cardiology
• Autonomic Nervous System Disorders
• Neurally Mediated Syncope

Background:

• Recurrent vasovagal syncope (VVS) is characterized by transient cerebral hypoperfusion due to episodic hypotension and bradycardia.
• Postural tachycardia syndrome (POTS) presents with chronic orthostatic intolerance and excessive upright tachycardia without hypotension.
• Distinguishing VVS from POTS can be challenging when tachycardia precedes hypotension during tilt testing.

Purpose of the Study:

• To investigate whether the excessive tachycardia observed during head-up tilt (HUT) testing in patients with VVS is a component of the vasovagal response.
• To differentiate the hemodynamic responses during HUT testing between patients with VVS and healthy controls.

Main Methods:

• Prospective head-up tilt (HUT) testing was performed on 47 patients with recurrent VVS and 15 age- and BMI-matched healthy controls.
• Hemodynamic parameters including blood pressure, heart rate (HR), cardiac output, total peripheral resistance, and end-tidal carbon dioxide were continuously monitored.

Main Results:

• Patients with VVS exhibited a significantly greater increase in HR during HUT compared to controls (39.8 ± 2.1 vs. 20.3 ± 2.9 beats per minute, P < .001).
• A substantial percentage of VVS patients (26% at 5 minutes, 44% before syncope) showed an HR increase of ≥40 beats per minute during HUT, which was not observed in controls.
• Baseline hemodynamic parameters were similar between VVS patients and controls.

Conclusions:

• The significant tachycardia observed during orthostasis in patients with VVS is an integral part of the vasovagal response.
• This pronounced heart rate increase during HUT testing in VVS patients should not be misinterpreted as indicative of POTS.