Pharmacologic atrial defibrillation by drug delivery into the temporarily occluded coronary sinus. A canine study

Venous blood draining from the left atrium (LA) flows into the coronary sinus (CS) through the Marshall vein which has no valvular apparatus, thus allowing LA retroperfusion if reflow in the right atrium is hindered. We investigated pharmacologic atrial defibrillation via the CS in dogs with chronic atrial fibrillation (AF). Chronic AF was induced by rapid atrial pacing for 4-16 weeks in 6 mongrel dogs. A 7F occlusion balloon catheter was introduced into the proximal CS. Boluses of low doses of the class Ic antiarrhythmic drug, pilsicainide (2, 4, 6, and 8 mg as needed) or class III antiarrhythmic drug, nifekalant (0.5, 1, 2, and 4 mg) were infused directly within 3-4 seconds at 10 minute intervals into the temporarily balloon occluded CS near its orifice. In 4 of the 5 dogs (balloon catheter could not be placed in the CS in 1 dog), the cumulative dose of 11.5 ± 7.4 mg of pilsicainide was effective in restoring sinus rhythm; the venous concentration of pilsicainide was 1.23 ± 0.79 µg/mL. A cumulative dose of 7.5 mg nifekalant restored sinus rhythm in only 1 of the 6 dogs. Our results in dogs with sustained AF indicate that delivery of a class Ic or III antiarrhythmic drug near the CS ostium via the temporarily occluded CS is feasible and effective for pharmacologic atrial defibrillation; however, the effect may be related to the elevation of the serum concentration of the drug to the therapeutic range rather than to the delivery method itself.