This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hsu, W. Articles by Jones, J. L. Search for Related Content PubMed PubMed Citation Articles by Hsu, W. Articles by Jones, J. L.

(Circulation. 1998;98:808-812.)
© 1998 American Heart Association, Inc.

Basic Science Reports

Improved Internal Defibrillation Success With Shocks Timed to the Morphology Electrogram

William Hsu, PhD; Yayun Lin, MSEE; Douglas J. Lang, PhD; ; Janice L. Jones, PhD

From the Department of Tachyarrhythmia Research, CPI/Guidant, St Paul, Minn, and the Department of Physiology and Biophysics, Georgetown University and Department of Veterans Affairs Medical Center, Washington, DC (J.L.J.).

Correspondence to Janice Jones, PhD (151P), Georgetown University and DVAMC, 50 Irving St, NW, Washington, DC 20422. E-mail jjones04{at}medlib.georgetown.edu

Background—A previous retrospective study by our group suggested that shocks timed to the upslope of the shocking lead electrogram improved defibrillation efficacy. The goal of this study was to prospectively determine whether defibrillation threshold could be reduced by use of an algorithm that timed shocks to the upslope of coarse ventricular fibrillation (test treatment) compared with shocks delivered asynchronously after 10 seconds of fibrillation (control treatment).

Methods and Results—Ten pigs were instrumented with a 3-lead system for internal defibrillation. Initial estimates of the energy required to achieve defibrillation E₅₀ for both treatments were made by an up/down method. Subsequently, additional shocks at V₅₀±10% and V₅₀±20% were given for each treatment to obtain data points at higher and lower intensities. Probability-of-success curves were estimated for both treatments by the best-fit method. Energies required were significantly lower for the timed shocks than for the asynchronous shocks (P<0.001). E₈₀ was reduced 15.5%, from 27.1±2.5 to 22.9±1.8 J (P<0.002). The width of the probability-of-success curve (E₈₀-E₂₀) for the test treatment was also significantly narrower than that for the control treatment (7.1±0.9 versus 10.8±1.7, P<0.01). Normalized curve width (E₈₀-E₂₀)/E₅₀ was decreased from 51±5% of E₅₀ for control shocks to 37±4% of E₅₀ for synchronous shocks (P<0.02).

Conclusions—In this model, defibrillation threshold is lower and more deterministic when shocks are timed to the upslope of the shocking lead electrogram. If a similar reduction is observed in humans, shock timing may lower defibrillation threshold and simplify programming of shock intensity.

Key Words: action potentials • defibrillation • electrophysiology • fibrillation

This article has been cited by other articles:

				T. H. Everett IV, E. E. Wilson, S. Foreman, and J. E. Olgin Mechanisms of Ventricular Fibrillation in Canine Models of Congestive Heart Failure and Ischemia Assessed by In Vivo Noncontact Mapping Circulation, September 13, 2005; 112(11): 1532 - 1541. [Abstract] [Full Text] [PDF]

				N. Chattipakorn, I. Banville, R. A. Gray, and R. E. Ideker Mechanism of Ventricular Defibrillation for Near-Defibrillation Threshold Shocks: A Whole-Heart Optical Mapping Study in Swine Circulation, September 11, 2001; 104(11): 1313 - 1319. [Abstract] [Full Text] [PDF]

				T. H. Everett IV, J. R. Moorman, L.-C. Kok, J. G. Akar, and D. E. Haines Assessment of Global Atrial Fibrillation Organization to Optimize Timing of Atrial Defibrillation Circulation, June 12, 2001; 103(23): 2857 - 2861. [Abstract] [Full Text] [PDF]