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METHODS
Bipolar surface electrogram (EG):
Bipolar electrograms were obtained using quadripolar RFA-electrophysiology catheters (St. Jude
Medical Livewire™ 7F with 4 mm tip and 2-5-2 mm spacing), as well as Teflon-insulated (except at the
tip) silver electrodes spaced 2 mm apart. Bipolar EG recordings were simultaneously band-pass filtered at
0.1-1000Hz, 10-1000Hz, 30-1000Hz and 10-250Hz, 30-250 Hz and 100-250 Hz to differentiate low and
high frequency (slope) changes. In figures where the band-pass filter setting of the EG is not specified, the
traces recorded with 0.1-1000Hz filter are shown throughout the study.
Measurements and Calculations
ECG parameters:
The interval between the peak and the end of the T wave (Tpeak-Tend) was measured from the
apex or nadir to the end of the T wave ( where the steepest tangent of the second component of the T wave
intersects the zero-line) (Figure 1A).
J wave area was calculated using SigmaPlot software (Systat Software Inc.). The onset of the J
wave (Jo) was set as defined by the recent consensus paper by Macfarlane et al. (1) The end of the J wave
(Jt) was set to the point where its downslope meets the isoelectric line set to the QRS-onset, which was
also considered as the bottom limiting line of J wave area measurement. For a better basis of comparison,
J wave area was normalized to R wave amplitude (J wave arear) (Figure 1A).
Action potential (AP) parameters:
AP notch area (NA) was calculated using SigmaPlot software (Systat Software Inc.). The start of
the notch was defined as the peak of phase 0 (point at which the first derivative of phase 0 is zero). The
end of the notch was determined as the peak of the phase 2 plateau (where the first derivative reaches the
zero line). The upper limiting line of area measurement was defined as the horizontal cursor set to the
peak of the phase 2 plateau (Figure 1A). Here again we normalized NA to phase 2 amplitude (notch arear).
Epicardial dispersion of repolarization (EDR) was calculated as the longest interval between
the AP durations measured at 90% repolarization (APD90) of the two simultaneously recorded epicardial
APs (Figure 1B) corrected by the activation time (AT) differences as follows:
EDR = (APD90Epi2 + ATEpi2) – (APD90Epi1 + ATEpi1).
Transmural dispersion of repolarization (TDR) was calculated as the longest interval between
endocardial (Endo) and epicardial (Epi) APD90 values in simultaneously recorded APs (Figure 1B),
corrected by AT difference as follows: TDR = (APD90Endo + ATEndo) – (APD90Epi + ATEpi).
STUDY LIMITATIONS
It is noteworthy that the pharmacological models employed in our study may not precisely mimic
the effect of the genetic variants underlying the clinical syndrome. It would be preferable to study these
relationships in transgenic animal models, but none are available at present. Transgenic mice are not
helpful because of fundamental differences in repolarization characteristics. Transgenic rabbits are not
available and are unlikely to be useful because the transient outward current (Ito), which is at the heart of
mechanism responsible for BrS , is very slow to recover from inactivation and contributes little to early
repolarization at normal heart rates. Transgenic dogs are not available. As discussed in the main paper, a
transgenic pig model expressing a BrS mutation has been developed, but is unable to recapitulate the BrS
phenotype, presumably because pigs lack Ito. (2)
It can also be argued that arterially perfused wedge preparations do not represent the complete
anatomical structure of the heart and thus may not fully recapitulate the disease phenotype. Endocardial
point-stimulation and the lack of His-Purkinje activation alters the normal activation pattern and thus may
blunt the impact of conduction defects. At the present time, the arterially perfused canine ventricular
wedge model is the only model capable of recapitulating all features of the BrS (e.g., response to
pharmacologic agents, response to ablation, response to changes in heart rate, electrographic and
arrhythmic manifestations). This model permitted us and other groups the ability to elucidate the cellular
mechanisms and thus to recommend novel therapeutic approaches. Using these models our laboratory was
the first to recommend the use of quinidine and isoproterenol for the treatment of the J wave syndromes
(3), which are widely used in the clinic today to deal with J wave syndrome-associated electrical storms or
as an adjunct to ICD therapy. These models have also identified ECG markers such as Tpeak-Tend and
QT/RR relationships that have proved useful in risk stratification of patients with LQTS, BrS and SQTS.
(4-7)
These similarities notwithstanding, translation of our results to humans should be approached with
caution.
Figure 1: Schematic illustration of parameters characterizing Brugada syndrome phenotype.
APs: action potentials; Endo: endocardial; Epi: epicardial, Tp-Te: Tpeak-Tend interval, ECG:
electrocardiogram; TDR: transmural dispersion of repolarization; EDR: epicardial dispersion of
repolarization. A: AP notch area (yellow), J wave area (blue) and Tp-Te (blue double-arrow). B: TDR
(blue double-arrow) and EDR (yellow double-arrow).
Figure 2: Ajmaline decreases early repolarization phenotype displaying small J waves.
Simultaneously recorded endocardial (Endo) and epicardial (Epi) action potentials together with an
epicardial bipolar electrogram (Bip. Epi EG) and a pseudo ECG recorded from arteially perfused canine
left ventricular wedge preparation. Prolongation of QRS duration and dimished epicardial action
potential notch led to disappearence of the J wave. The effects were reversible upon washout. These
results explain the clinical observations of Bastiaenen et al. (8) and Roten et al. (9)., who reported
improvement of early repolarization pattern in response to ajmaline.
Figure 3: Late potential characteristics vary as a function of the degree of AP notch accentuation. Traces
are as described in Figure 1. The first grouping shows an example of concealed phase 2 reentry giving rise
to a prominent late potential in the bipolar epicardial electrogram (Bip. Epi EG). Subsequent groupings
show late potentials due to the prominent second upstroke of the epicardial action potential.
Figure 4: Late potentials appear on the epicardial (Epi) but not on the endocardial (Endo) electrogram
(EG). Simultaneous recordings of action potentials (AP) and bipolar electrograms (Bip. EG) from the
endocardium and epicardium of arterially perfused canine right ventricular wedge preparation.
Delayed 2nd upstroke of the Epi AP, secondary to a massively pronounced notch, depicts on the Epi EG as
late potential, but does not alter the Endo EG characteristics. The morphology of these late potentials are
similar to those reported by Nakagawa et al (10) in early repolarization syndrome –related idiopathic
ventricular fibrillation.
Table 1: Incidence of Brugada syndrome phenotype and arrhythmic activity at each experimental step.
Exp.
Control
Ajm.+Pin.
BrSECG
1
2
3
4
5
6
7
8
9
10
11
-
NS.+Ver.
BrSECG
1
2
3
4
5
6
7
8
9
-
Provocative agents
L.o.t.d. P2R+EG CCPVC VT/VF
-
-
-
-
L.o.t.d. P2R+EG CCPVC VT/VF
-
-
-
-
BrSECG
+
+
+
+
+
+
BrSECG
+
+
+
+
+
+
+
+
+
Ablation
BrSECG
L.o.t.d. P2R+EG CCPVC VT/VF
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Epi
Epi
Epi
Epi
Endo
Endo
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Epi
Epi
Epi
Epi
Epi
Epi
Endo
Endo
Endo
L.o.t.d. P2R+EG CCPVC VT/VF
↓
↓
-
-
-
-
↓
-
-
-
-
↓
↔
+
+
+
+
↔
+
+
+
+
BrSECG
L.o.t.d. P2R+EG CCPVC VT/VF
+
+
+
+
+
+
+
+
+
After ablation
↓
↓
↓
↓
↓
↓
↔
↔
↔
L.o.t.d. P2R+EG CCPVC VT/VF
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
Ajm.+Pin.: Experiments in which ajmaline and pinacidil were used to provoke BrS; NS.+Ver.: experiments in which NS5806 and verapamil were
applied to provoke BrS. Epi: surface epicardial radiofrequency ablation; Endo: surface endocardial radiofrequency ablation; Br-ECG: Brugada ECG
pattern ; L.o.t.d.: loss of the action potential dome at (some) epicardial sites; P2R+EG: phase 2 reentry and/or abnormal local electrogram recordings;
CCPVC: closely coupled premature complexes including couplets, triplets, bigeminy, trigeminy and salvos (≤5 consecutive closely coupled premature
beats); VT/VF: polymorphic ventricular tachycardia or fibrillation (˃5 consecutive closely coupled premature beats).
-: absent, +: present, ↓: significant decrease; ↔: no change
REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Macfarlane PW, Antzelevitch C, Haissaguerre M et al. The Early Repolarization Pattern:
A Consensus Paper. J Am Coll Cardiol 2015;66:470-7.
Park DS, Cerrone M, Morley G et al. Genetically engineered SCN5A mutant pig hearts
exhibit conduction defects and arrhythmias. J Clin Invest 2015;125:403-12.
Yan GX, Antzelevitch C. Cellular basis for the Brugada syndrome and other mechanisms
of arrhythmogenesis associated with ST segment elevation. Circulation 1999;100:16601666.
Antzelevitch C, Sicouri S, Di Diego JM et al. Does Tpeak-Tend provide an index of
transmural dispersion of repolarization? Heart Rhythm 2007;4:1114-1116.
Extramiana F, Antzelevitch C. Amplified transmural dispersion of repolarization as the
basis for arrhythmogenesis in a canine ventricular-wedge model of short QT syndrome.
Circulation 2004;110:3661-3666.
Patel C, Antzelevitch C. Cellular basis for arrhythmogenesis in an experimental model of
the SQT1 form of the short QT syndrome. Heart Rhythm 2008;5:585-590.
Antzelevitch C, Oliva A. Amplification of spatial dispersion of repolarization underlies
sudden cardiac death associated with catecholaminergic polymorphic VT, long QT, short
QT and Brugada syndromes. J InternMed 2006;259:48-58.
Bastiaenen R, Raju H, Sharma S et al. Characterization of early repolarization during
ajmaline provocation and exercise tolerance testing. Heart Rhythm 2013;10:247-254.
Roten L, Derval N, Sacher F et al. Ajmaline attenuates electrocardiogram characteristics
of inferolateral early repolarization. Heart Rhythm 2012;9:232-239.
Nakagawa K, Nagase S, Morita H, Ito H. Left ventricular epicardial electrogram
recordings in idiopathic ventricular fibrillation with inferior and lateral early
repolarization. Heart Rhythm 2014;11:314-7.