Heart rate variability analysis during head-up tilt test predicts nitroglycerine-induced syncope.

Area of Science:

• Cardiology
• Autonomic Nervous System Function
• Diagnostic Testing

Background:

• Head-up tilt testing (HUTT) is used to diagnose syncope.
• Nitroglycerine administration during HUTT can elicit syncope in susceptible individuals.
• Predicting syncope during HUTT can improve diagnostic efficiency.

Purpose of the Study:

• To assess if heart rate variability (HRV) analysis during the initial 20 minutes of HUTT can predict syncope after nitroglycerine administration.
• To identify specific HRV parameters indicative of impending syncope.

Main Methods:

• 64 patients with prior loss of consciousness underwent HUTT with the Italian protocol.
• HRV parameters were analyzed during pre-tilt rest and during the first 20 minutes of passive tilting.
• Changes in HRV spectral components (high frequency and total power) were calculated before nitroglycerine administration.

Main Results:

• Patients who experienced syncope after nitroglycerine (n=20) showed a significant decrease in high frequency and total power HRV parameters during tilting.
• Patients who did not experience syncope (n=44) did not exhibit significant changes in these HRV parameters.
• The calculated changes in HRV parameters (Δ) between tilt phases effectively differentiated between patients who would and would not experience syncope.

Conclusions:

• HRV analysis during the first 20 minutes of HUTT can predict nitroglycerine-induced syncope.
• A progressive decline in parasympathetic activity, reflected in HRV, is characteristic of patients who will develop syncope.
• HRV analysis may offer a non-invasive alternative to nitroglycerine, potentially shortening HUTT duration.