Sphenopalatine ganglion block: an external gate to modulate cardiac autonomic tone and suppress premature ventricular beats?

Background: Autonomic modulation is used for treating various cardiovascular diseases, such as cardiac arrhythmias. Sphenopalatine ganglion (SPG) block is an easy, non-invasive therapy for migraine with a potential cardiovascular impact that remains unclear. In this study, we sought to assess the effect of SPG block on cardiac autonomic tone, as expressed by heart rate variability (HRV), and on ventricular arrhythmogenesis. Methods: Forty patients (14 male and 26 female) suffering from migraine were randomized by 1:1 to SPG block or placebo (controls) and HRV parameters were evaluated 1 hour before and hourly after the intervention. Twenty-four additional patients (11 men and 13 women) with premature ventricular contractions (PVCs) from the right ventricular outflow tract underwent the same randomization and the number of PVCs was assessed during 1 hour before and every hour after treatment. Values were summarized as median (1st–3rd quartile). Results: During the first four hours after SPG block, an increase in mean RR [883 (IQR, 869–948) vs. 839 (IQR, 806–887) ms at baseline, P<0.01], SDNN [64 (IQR, 59–69) vs. 51 (IQR, 47–55) ms, P<0.01], SDANN [39 (IQR, 36–43) vs. 27 (IQR, 22–29) ms, P<0.01], ASDNN [51 (IQR, 47–53) vs. 40 (IQR, 37–44) ms, P<0.01], rMSSD [30 (IQR, 27–32) vs. 25 (IQR, 23–27) ms, P<0.01], VLF [26 (IQR, 24–29) vs. 23 (IQR, 22–25) ms2, P<0.01] and HF [14 (IQR, 11–16) vs. 11 (IQR, 9–12) ms2, P<0.01], along with a decrease in LF/HF ratio [1.7 (IQR, 1.4–1.9) vs. 2.0 (IQR, 1.7–2.5), P<0.01] was observed in patients with migraine. In patients with PVCs, the number of ectopic ventricular beats per hour was decreased for the first five hours following SPG block [360 (IQR, 264–850) from 956 (IQR, 545–1,412), P<0.001]. No such differences were observed in controls. Conclusions: SPG block is associated with a transient increase in those HRV parameters that mainly express parasympathetic activity. It is also followed by a significant decrease in ventricular arrhythmic burden. These findings imply an effect on cardiac autonomic tone with a potential favorable clinical impact on arrhythmogenesis.