Presented at the Annual Scientific Sessions of the Heart Rhythm Society, Boston, USA, May 2024 History of the development of the concept and many ECG examples

1. Supernormal Conduction
Sergio L. Pinski, MD, FHRS
Medical University of South Carolina
Charleston, South Carolina, USA
@SergioPinski

2. • No conflicts of interest, besides the fact that I am Argentinian.

3. Definitions of Supernormal Conduction
A misnomer. Conduction is not better than normal.
”Impulse conduction is better than expected”
”Conduction that is better than anticipated under the circumstances”
“ Propagation succeeds early in diastole and fails later".
True only when conduction improves in relation to a supernormal phase
of excitability. Many other unrelated causes of improvement “pseudo-
supernormal conduction”

4. The case of Katz & Pick, 1956

5. 1962
1968 1973
1983

6. The definitive review - Mandatory reading
for EP fellows
Current Cardiology Reviews, 2014, 10: 202-221

7. Latest edition of Josephson’s edited by
Callans

9. Causes of pseudo supernormal conduction
in AV conduction
• Gap phenomena
• Shortening of refractoriness by changing the preceding cycle length
• Peeling of refractoriness by an early beat
• Manifest or concealed nodal reentry during Wenckebach periodicity
• Dissociation with interference
• Dual AV nodal pathways
• Pulsatile changes in vagal discharge
• Facilitation of conduction by ectopic beats (summation)

10. Causes of pseudo supernormal conduction
in bundle branch block
• Gap phenomena
• Peeling of refractoriness by an early beat
• Shortening of refractoriness by changing the preceding cycle
length
• Dissipation of concealed transeptal conduction
• Wenckebach phenomenon in the bundle branches
• Bradycardia-dependent or phase 4 block
• Bilateral bundle branch delay

11. Equal delay in conduction in the bundle
branches: My pet peeve
• To my knowledge, never demonstrated. I could not find a convincing
example in a thorough literature review. I believe it unlikely to exist.
• Clinical and experimental evidence demonstrate that most cases of
bundle branch block are true “blocks”
• Given the very different length of the fascicles, the possibility that delay
will be exactly the necessary in each one to result in a narrow QRS is very
improbable
• Type 2 gap can result in pseudo supernormal conduction with a long HV.
Diligent search for a split His or a bundle branch potential reveals that
the delay is proximal.

12. Where does supernormal conduction exist?
• In depressed or injured His-Purkinje system (mainly bundle
branches)
• In not very healthy A-V accessory pathways (WPW)
• It cannot occur in the AV node. AV supernormal conduction
can only occur in infranodal block, and so it is a special
variant of supernormal conduction in His or bundle branches

13. Typical behavior of supernormal conduction
in intermittent bundle branch block
Rosenbaum et al. Cardiol Clin 1983;1:75

14. Supernormal conduction in LBB in presence
of RBBB= supernormal AV conduction
Miles & George. Cardiol Clin 2023;41:315

15. Unexpected narrow beats during atrial fibrillation
Wellens H. Am Heart J 1969;77:158

16. Spontaneous demonstration of
supernormal conduction in LBBB
Levi et al. In Frontiers in Cardiac Electrophysiology, 1983

17. PAC and compensatory pause unmasks phase 3
block and supernormal conduction in LBB
@SergioPinski

18. Marked sinus arrhythmia unmasks phase 3 block
and supernormal conduction in LBB
@SergioPinski

19. PACs with possible supernormal conduction in
the left anterior fascicle
@SergioPinski

20. Supernormal conduction as a mechanism
of 2:1 bundle branch block
Elizari et al. Curr Cardiol Rev 2014;202-221

21. 1:1 Supernormal Conduction
Aldariz et al. Rev Arg Cardiol 1998;66:203

22. Supernormal Conduction explains early
captures in infranodal block
Rosenbaum et al. Cardiol Clin 1983;1:75

23. Supernomal conduction explains the
paradoxes of 3:2 Mobitz II AV block
Rosenbaum et al. Cardiol Clin 1983;1:75

24. Pacing proves that Mobitz II 3:2 is due to
supernormal conduction
@SergioPinski

25. Even the HV can shorten due to supernormal
conduction
Rosenbaum et al. Cardiol Clin 1983;1:75

26. Paradoxical shortening of the 2nd PR in 3:2
AV nodal block
Pinski et al. J Cardiovasc Electrophysiol 1996;7:1091

27. Paradoxical shortening of the PR in 3:2 AV
nodal block
Pinski et al. J Cardiovasc Electrophysiol 1996;7:1091

28. Supernormal conduction in WPW
Przybylski et al. Am J Cardiol 1987;9:1269

29. Supernormal conduction in WPW resulting in
2:1 pre-excitation
Cheng et al. Am J Cardiol 1987;59:852

30. Supernormal retrograde conduction in
left concealed accessory pathway
Chiale et al. J Cardiovasc Pharmacol Ther 2007;12:181

31. Possible 1:1 supernormal conduction in WPW
Chiale et al. J Cardiovasc Pharmacol Ther 2007;12:181

32. Conclusions
• Supernormal conduction exists in depressed His-Purkinje tissue
(generally intermittent bundle branch block) and AV accessory
pathways with poor conduction
• Generally, has little clinical significance but helps explain may puzzling
ECG findings.
• It can be casual to the rare cases of sudden death in patients with
WPW with a long baseline refractory period