Initial energy setting, outcome and efficacy in direct current cardioversion of atrial

fibrillation and flutter

The probability of success on the first shock in AF of > 30 days duration was 5.5% at < 200 J, 35% at 200 J and 56% at 360J

In atrial flutter, an initial 100 J shock work in 68% In Af of > 30 days duration, shock of < 200 J had a

6.1% probability of success , this fell to 2.2% with a duration of > 180 days

AF > 180 days, initial use of a 360 J shock was associated with eventual use of less electrical energy than initial shock of 100 J≦

ACC/AHA/ESC Practice Guidlines

An initial shock of 100 J is often to low, and an initial energy of 200 J or greater is recommended for electrical CV of AF

Chronic atrial fibrillation. Long-term results of direct current conversion--- Lundstrom T et al. Acta Med Scand 1988;223:53-9

primary success rate as measured 3 days after CV in 100 consecutive subjects was 86%; increase to 94% when procedure was repeated during treatment with quinidine or disopyramide

23% remained in SR after 1 year and 16% after 2 years

in relapsed pts, repeated CV with antiarrhythmic medication resulted in SR in 40% and 33% after 1 and 2 years

relapsed again, a third CV resulted in SR in 54% at 1 year and 41% at 2 year

DC countershock vs Myocardial damage

Animal study Myocardial injury from transthoracic

defibrillation countershock--- Warner ED et al. Arch Pathol 1975;99:55-9

DC shock in 66 dogs, 400 watt-seconds, animal were killed from 3 to 14 days after receiving the discharges, myocardial necrosis was produced in most of the animals

Cardiac damage produced by direct current countershock to the heart. ---- Doherty PW

et al.Am J Cardiol 1979;43:225-32

DC shock over a dose range of 10-90 watt-seconds, applied directly to the heart in 26 dogs

The threshold for significant injury was approximately 30 watt-seconds

Therapeutic indices for transchest defibrillator shocks: effective, damage and lethal electrical doses---- Babbs CF et al. Am Heart J 1980;99:734-8

In terms of delivered energy the ED50, TD50, LD 50 were 1.5 30, and 470 joules/Kg

TD50= median toxic or damage-inducing dose, ED50= median effective or defibrillating dose, LD50= median lethal dose

a reasonable margin of safety for damped sine wave defibrillator shock in dogs

Direct current cardioversion dose not cause cardiac damage: evidence from cardiac troponin T estimation ---RaoAC et al. Heart 1998;80:229-30

Cardiac troponin T and CK were estimated 20-28 hours after DC cardioversion in 51 Pts who received DC shocks for elective CV of chronic AF/AFL

Although CK was raised in 44 patients, cardiac troponin T was undetectable in all Pts.

Plasma levels of troponin T after electrical cardioversion of atrial fibrillation and flutter--- Neumayr G et al. Am J Cardiol 1997;10:1367-9

Measure plasma levels of troponin T after electrical CV in 33 AF/AFL patients

unchanged normal levels of troponin T indicate that significant myocardial cell injury by shocks in the usual dosage in unlikely to occur

Electrical Cardioversion (1)

Successful CV of AF depends on the nature of the underlying heart disease and the current density delivered to the atrial myocardium

The latter depends on the voltage of the defibrillator capacitor , the output waveform, the size and position of the electrode paddles, and transthoracic impedance

Electrical Cardioversion (2)

Monophasic waveform shock damped sinusoidal truncated exponential

biphasic waveform shocklow energy internal cardioversion