Effects of Combined Sildenafil-Nitric Oxide Donor On Defibrillation Efficacy
Krekwit Shinlapawittayatorn MD*, Siriporn Chattipakorn PhD*, Rattapong Sungnoon MD*, Nipon Chattipakorn MD, PhD*
Affiliation : * Cardiac Electrophysiology Unit, Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai * Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai
Background : A previous study demonstrated that supra-therapeutic concentration of sildenafil citrate attenuates
defibrillation efficacy. However, the effect of combined sildenafil and NTG administration on defibrillation
efficacy is not known.
Objective : The present study investigated whether sildenafil administration at the therapeutic level increases
the defibrillation threshold (DFT) when combined with NTG.
Materials and Methods : Twenty-four pigs (20-25 kg) were randomized into four groups. After the control DFT
was obtained, a stock solution of 50-mg (group 1, therapeutic concentration) and 100-mg (group 2, supra-
therapeutic concentration) of sildenafil, and 100-mL of saline (groups 3 and 4) were infused at 2 mL/min.
Then, NTG was administered in groups 1-3 at 5 (cid:31)g/min, with an increment of 5 (cid:31)g/min every 5 min. The DFT
was determined again after NTG was infused for 20 minutes.
Results : In group 1, the DFT (402 + 33V, 11 + 2J) was not different from the control (404 + 28V, 11 + 2J). In
group 2, the DFT (521 + 18V, 19 + 1J) was higher (p < 0.004) than that in the control group (444 + 31V, 14
+ 2J). Saline did not alter the DFT, either individually or in combination with NTG.
Conclusion : Supratherapeutic dose of sildenafil-NTG combination significantly increased the DFT (17% of
peak voltage, 37% of total energy). This effect on DFT appears to be driven by sildenafil and not NTG.
Keywords : Sildenafil citrate, Nitroglycerin, Fibrillation, Defibrillation
