Initial energy setting, outcome and efficacy in direct current cardioversion of atrial fibrillation and flutter - PowerPoint PPT Presentation

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Initial energy setting, outcome and efficacy in direct current cardioversion of atrial fibrillation and flutter PowerPoint Presentation
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Initial energy setting, outcome and efficacy in direct current cardioversion of atrial fibrillation and flutter

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

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  1. 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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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

  9. 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

  10. Electrical Cardioversion (2) • Monophasic waveform shock • damped sinusoidal • truncated exponential • biphasic waveform shock • low energy internal cardioversion