Critical Points and the Upper Limit of Vulnerability for Defibrillation

  • Raymond E. Ideker
  • Derek J. Dosdall

Electric shocks delivered to the heart are like a double-edged sword. Depending on the circumstances, they can either halt an arrhythmia or initiate one. Except for very large shocks that are so strong that their damaging effects cause immediate refibrillation, there is a range of shock strengths, below which shocks almost always fail to defibrillate and above which they usually successfully defibrillate. Throughout this range, the probability of successful defibrillation increases as the shock strength increases. The defibrillation threshold (DFT) is a single shock strength within this range whose mean value depends on the method used to estimate it.1 For example, one method gave a mean DFT value that was at the 71% probability of success point (DF71), meaning that this shock strength would be expected to succeed 71% of the time.2

There is a different range of shock strengths in which ventricular fibrillation (VF) is induced when the shock is given during cardiac repolarization (i.e., the vulnerable period). The lower limit of this range, the ventricular fibrillation threshold (VFT), is considerably lower than the range of shock strengths that defibrillate. However, the upper limit of this range, the upper limit of vulnerability (ULV), is typically within the range of shock strengths that successfully defibrillate.3,4 If the ULV did not exist, then it might not be possible to defibrillate with a shock of any strength because VF is so complex that some cardiac regions are probably in the vulnerable period at any time during VF. Thus, if the ULV did not exist, a shock larger than the VFT, even if it halted all the VF wavefronts, would immediately reinitiate VF in the regions in the vulnerable period. Just as for defibrillation, the ULV is also not a single value, but is a probability function in which the odds of not inducing VF increase with increasing shock strength.5


Ventricular Fibrillation Refractory Period Potential Gradient Transmembrane Potential Critical Point Theory 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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  1. 1.
    Singer I, Lang D. Defibrillation threshold: clinical utility and therapeutic implications.PAC E1992;15:932–949Google Scholar
  2. 2.
    Davy JM, Fain ES, Dorian P, Winkle RA. The relationship between successful defibrillation and delivered energy in open-chest dogs: reappraisal of the “defibrillation threshold” concept.Am Heart J1987;113(1):77–84PubMedCrossRefGoogle Scholar
  3. 3.
    Lesigne C, Levy B, Saumont R, Birkui P, Bardou A, Rubin B. An energy-time analysis of ventricular fibrillation and defibrillation thresholds with internal electrodes.Med Biol Eng1976;14(6):617–622PubMedCrossRefGoogle Scholar
  4. 4.
    Chen PS, Shibata N, Dixon EG, Martin RO, Ideker RE. Comparison of the defibrillation threshold and the upper limit of ventricular vulnerability.Circulation1986;73(5):1022– 1028PubMedGoogle Scholar
  5. 5.
    Malkin RA, Idriss SF, Walker RG, Ideker RE. Effect of rapid pacing and T-wave scanning on the relation between the defibrillation and upper-limit-of-vulnerability dose-response curves.Circulation1995;92(5):1291–1299PubMedGoogle Scholar
  6. 6.
    Swerdlow CD, Shehata M, Chen PS. Using the upper limit of vulnerability to assess defibrillation efficacy at implantation of ICDs.Pacing Clin Electrophysiol2007;30(2):258–270PubMedCrossRefGoogle Scholar
  7. 7.
    Shibata N, Chen PS, Dixon EG, Wolf PD, Danieley ND, Smith WM, Ideker RE. Epicardial activation after unsuccessful defibrillation shocks in dogs.Am J Physiol1988;255(4 Pt 2):H902–H909PubMedGoogle Scholar
  8. 8.
    De Piccoli B, Rigo F, Raviele A, Piccolo E, Maggiolo C, Milanesi A, Simone M. Transesophageal echocardiographic evaluation of the morphologic and hemodynamic cardiac changes during ventricular fibrillation.J Am Soc Echocardiogr1996;9(1):71–78PubMedCrossRefGoogle Scholar
  9. 9.
    Foley PJ, Tacker WA, Wortsman J, Frank S, Cryer PE. Plasma catecholamine and serum cortisol responses to experimental cardiac arrest in dogs.Am J Physiol1987;253(3 Pt 1):E283–E289PubMedGoogle Scholar
  10. 10.
    Kern KB, Elchisak MA, Sanders AB, Badylak SF, Tacker WA, Ewy GA. Plasma catecholamines and resuscitation from prolonged cardiac arrest.Crit Care Med1989;17(8):786–791PubMedCrossRefGoogle Scholar
  11. 11.
    Tovar OH, Jones JL. Electrophysiological deterioration during long-duration ventricular fibrillation.Circulation2000;102(23):2886–2891PubMedGoogle Scholar
  12. 12.
    Dosdall DJ, Cheng KA, Huang J, Allison JS, Allred JD, Smith WM, Ideker RE. Transmural and endocardial Purkinje activation in pigs before local myocardial activation after defibrillation shocks.Heart Rhythm2007;4(6):758–765PubMedCrossRefGoogle Scholar
  13. 13.
    Han J, Moe GK. Nonuniform recovery of excitability in ventricular muscle.Circ Res1964;14:44–60PubMedGoogle Scholar
  14. 14.
    Guyton AC, Hall JE. Cardiac arrhythmias and their electrocardiographic interpretation.Textbook of Medical Physiology, 10th edn. Philadelphia: W.B. Saunders; 2000:134–142Google Scholar
  15. 15.
    Cao JM, Qu Z, Kim YH, Wu TJ, Garfinkel A, Weiss JN, Karagueuzian HS, Chen PS. Spatiotemporal heterogeneity in the induction of ventricular fibrillation by rapid pacing: importance of cardiac restitution properties.Circ Res1999;84(11):1318–1331PubMedGoogle Scholar
  16. 16.
    Winfree AT. Time encircles a singularity.When Time Breaks Down: The Three-Dimensional Dynamics of Electrochemical Waves and Cardiac Arrhythmias. Princeton, NJ: Princeton University Press; 1987:125–153Google Scholar
  17. 17.
    Efimov IR, Cheng Y, Van Wagoner DR, Mazgalev T, Tchou PJ. Virtual electrode-induced phase singularity: a basic mechanism of defibrillation failure.Circ Res1998;82(8):918–925PubMedGoogle Scholar
  18. 18.
    Frazier DW, Wolf PD, Wharton JM, Tang AS, Smith WM, Ideker RE. Stimulusinduced critical point. Mechanism for electrical initiation of reentry in normal canine myocardium.J Clin Invest1989;83(3):1039–1052PubMedCrossRefGoogle Scholar
  19. 19.
    Daubert JP, Frazier DW, Wolf PD, Franz MR, Smith WM, Ideker RE. Response of relatively refractory canine myocardium to monophasic and biphasic shocks.Circulation1991;84(6):2522–2538PubMedGoogle Scholar
  20. 20.
    Knisley SB, Smith WM, Ideker RE. Effect of field stimulation on cellular repolarization in rabbit myocardium. Implications for reentry induction.Circ Res1992;70(4):707–715PubMedGoogle Scholar
  21. 21.
    Ideker RE, Alferness C, Melnick S, Sreenan KM, Johnson E, Smith WM. Reentry site during fibrillation induction in relation to defibrillation efficacy for different shock waveforms.J Cardiovasc Electrophysiol2001;12(5):581–591PubMedCrossRefGoogle Scholar
  22. 22.
    Shibata N, Chen PS, Dixon EG, Wolf PD, Danieley ND, Smith WM, Ideker RE. Influence of shock strength and timing on induction of ventricular arrhythmias in dogs.Am J Physiol1988;255(4 Pt 2):H891–H901PubMedGoogle Scholar
  23. 23.
    Idriss SF, Wolf PD, Smith WM, Ideker RE. Effect of pacing site on ventricular fibrillation initiation by shocks during the vulnerable period.AJP1999;277(Heart Circ Physiol 46):H2065–H2082Google Scholar
  24. 24.
    Chen PS, Shibata N, Dixon EG, Wolf PD, Danieley ND, Sweeney MB, Smith WM, Ideker RE. Activation during ventricular defibrillation in open-chest dogs. Evidence of complete cessation and regeneration of ventricular fibrillation after unsuccessful shocks.J Clin Invest1986;77(3):810–823PubMedCrossRefGoogle Scholar
  25. 25.
    Chattipakorn N, Ideker RE. Delayed afterdepolarization inhibitor: a potential pharmacologic intervention to improve defibrillation efficacy.J Cardiovasc Electrophysiol2003;14(1):72–75PubMedCrossRefGoogle Scholar
  26. 26.
    Idriss SF, Wolf PD, Smith WM, Ideker RE. Effect of pacing site on ventricular fibrillation initiation by shocks during the vulnerable period.Am J Physiol1999;277(5 Pt 2):H2065–H2082PubMedGoogle Scholar
  27. 27.
    Krassowska W, Frazier DW, Pilkington TC, Ideker RE. Potential distribution in three-dimensional periodic myocardium — Part II: application to extracellular stimulation.IEEE Trans Biomed Eng1990;37(3):267–284PubMedCrossRefGoogle Scholar
  28. 28.
    Lin SF, Roth BJ, Wikswo JP Jr. Quatrefoil reentry in myocardium: an optical imaging study of the induction mechanism.J Cardiovasc Electrophysiol1999;10(4):574–586PubMedCrossRefGoogle Scholar
  29. 29.
    Cheng Y, Mowrey KA, Van Wagoner DR, Tchou PJ, Efimov IR. Virtual electrode-induced reexcitation: a mechanism of defibrillation.Circ Res1999;85(11):1056–1066PubMedGoogle Scholar
  30. 30.
    Trayanova NA, Gray RA, Bourn DW, Eason JC. Virtual electrode-induced positive and negative graded responses: new insights into fibrillation induction and defibrillation.J Cardiovasc Electrophysiol2003;14(7):756–763PubMedGoogle Scholar
  31. 31.
    Efimov IR, Gray RA, Roth BJ. Virtual electrodes and deexcitation: new insights into fibrillation induction and defibrillation.J Cardiovasc Electrophysiol2000;11(3):339–353PubMedCrossRefGoogle Scholar
  32. 32.
    Knisley SB, Baynham TC. Line stimulation parallel to myofibers enhances regional uniformity of transmembrane voltage changes in rabbit hearts.Circ Res1997;81(2):229– 241PubMedGoogle Scholar
  33. 33.
    Nikolski VP, Efimov IR. Electroporation of the heart.Europace2005;7(Suppl 2):146–154PubMedCrossRefGoogle Scholar
  34. 34.
    Sharifov OF, Fast VG. Role of intramural virtual electrodes in shock-induced activation of left ventricle: optical measurements from the intact epicardial surface.Heart Rhythm2006;3(9):1063–1073PubMedCrossRefGoogle Scholar
  35. 35.
    Windisch H, Platzer D, Bilgici E. Quantification of shock-induced microscopic virtual electrodes assessed by subcellular resolution optical potential mapping in guinea pig papillary muscle.J Cardiovasc Electrophysiol2007;18(10):1086–1094PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC. 2009

Authors and Affiliations

  • Raymond E. Ideker
    • 1
  • Derek J. Dosdall
    • 1
  1. 1.Departments of Medicine, Biomedical Engineering, and PhysiologyUniversity of Alabama-BirminghamBirmingham

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