Key result
A decrease >7% in nonrespiratory frequency diastolic blood pressure variability 20 seconds after glyceryl trinitrate application predicted cardioinhibitory syncope (AUC 0.811).
Why the study?
Endogenous nitric oxide attenuates blood pressure variability (BPV) independently of blood pressure, leading to the hypothesis that glyceryl trinitrate might decrease BPV during presyncope and predict head-up tilt test outcome.
Does a decrease in blood pressure variability after glyceryl trinitrate application during a head-up tilt test predict cardioinhibitory syncope?
Observational (n=59)
Does a decrease in blood pressure variability after glyceryl trinitrate application during a head-up tilt test predict cardioinhibitory syncope?
A decrease in nonrespiratory frequency diastolic blood pressure variability shortly after GTN application during a tilt test can predict cardioinhibitory syncope.
May support BP variability monitoring for GTN-induced syncope prediction; leaves open larger validation trials.
PURPOSE: Glyceryl trinitrate (GTN) provoked cardioinhibitory syncope during the head-up tilt test is preceded by a period of disrupted blood pressure variability (BPV). Endogenous nitric oxide (NO) attenuates BPV independently of blood pressure (BP). We hypothesized that exogenous NO donor GTN might decrease BPV during the presyncope period. A decrease in BPV may predict the tilt outcome. METHODS: We analyzed 29 tilt test recordings of subjects with GTN-induced cardioinhibitory syncope and 30 recordings of negative subjects. A recursive autoregressive model of BPV after GTN was performed; powers of the respiratory (0.15-0.45 Hz) and nonrespiratory frequency (0.01-0.15 Hz) bands were calculated for each of the 20 normalized time periods. The post-GTN relative changes in heart rate, BP, and BPV were calculated. RESULTS: In the syncope group, spectral power of nonrespiratory frequency systolic and diastolic BPV progressively felt for 30% after GTN application and stabilized after 180 s. BP started to fall 240 s after the GTN application. Decrease in nonrespiratory frequency power of diastolic BPV 20 s after GTN administration predicted cardioinhibitory syncope (area under the curve 0.811; 77% sensitivity; 70% specificity; cutoff value > 7%). CONCLUSION: GTN application during the tilt test attenuates systolic and diastolic nonrespiratory frequency BPV during the presyncope period, independent of BP. A decrease in nonrespiratory frequency diastolic BPV 20 s after GTN application predicts cardioinhibitory syncope with good sensitivity and moderate specificity.
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Meglič et al. (2023) conducted an observational in Vasovagal syncope (n=59). Glyceryl trinitrate (GTN) application vs. Negative subjects (no syncope) was evaluated on Prediction of cardioinhibitory syncope by decrease in nonrespiratory frequency power of diastolic BPV 20 s after GTN administration (AUC 0.811). A decrease >7% in nonrespiratory frequency diastolic blood pressure variability 20 seconds after glyceryl trinitrate application predicted cardioinhibitory syncope (AUC 0.811).
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