Application Note

Cells:
Tools:

hiPSC-CM
CardioExcyte 96

Conduction velocity with the 2-electrodelayout of the CardioExcyte 96
Nanion Technologies GmbHCardiosight®-S hiPSC-CMs kindly provided by Nexel
SummaryResults

Cardiac conduction is the process by which electricalTo estimate the CV the time delay between theexcitation spreads through the heart, triggering individual

electrical pacing artifact and the maximum peakmyocytes to contract synchronously. Slowed cardiacof the EFP sodium spike was calculated before andconduction velocity (CV) is associated with an increasedafterrisk of re-entrant excitation, leading to a pre-disposition todistance between the stimulation electrode and thelife-threatening arrhythmias1.

recording electrode in the NSP-96 Stim plate is known

CV is determined by the ion channel properties of(Figure 1B), it is possible to estimate the CV as the ratio of

cardiac myocytes and by their interconnections. It is

the distance between the two electrodes and the timestrictly dependent on the maximum upstroke velocity ofdelay between the pacing artifact and the peak of thean action potential, which is determined by the sodium

sodium spike. The CV calculated with the CardioExcyte

current2. In addition, gap junctions play a key role because

96 is an approximation due to the presence of only two

they ultimately determine how much depolarizing

electrodes, which are simplified as two points. Therefore,

sodium current passes from excited to non-excitedthe percentage change before and after compound

regions of the network. Uncoupling of gap junctions

addition is calculated, instead of an absolute CV value.

causes discontinuities leading to slower CV. Defectiveintercellular coupling between the cardiomyocytes
results in increased subthreshold depolarization, which

compoundAaddition(Figure1A).

SincetheBTime delay

slowly inactivates the voltage-gated sodium channels,

Distance between the electrodes

EFP signal
before compound

further reducing the sodium current and excitability3.
In the case of collagenous scar tissue the uncoupling

EFP signal
after compoundof myocyte–myocyte connections and subsequent
coupling of myocytes with fibroblasts impairs theRecording
electrode
1.6 mmStimulationelectrodeelectrical conduction. In fact, collagen deposition resultsin electrically isolated fibers of viable myocardium,discontinuingtheconduction

path

and

globallyreducing the action potential propagation velocity
and consequently promoting the onset of re-entrant
arrhythmias4.
Since CV plays a pivotal role in cardiovascular diseases, it
is essential to investigate the effect of a new compoundon the cardiac CV.
In this study, we have investigated the effect of thesodium channel blocker lidocaine (30 and 100 µM)
on CV in hiPSC-CMs (NEXEL Cardiosight®-S) using theCardioExcyte 96.
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Pacingartifact
Figure 1: A) Simplified EFP signals under electrical pacing before (grey)
and after (blue) compound addition. The time delay between the pacing
artifact and the sodium spike peak used to calculate the conduction
velocity is depicted. B) Distance between the recording and stimulationelectrodes in the NSP-96 Stim plate.

Application Note
In control conditions, EFP signals are stable and canAbe overlaid when treated with vehicle (Figure 2). Thereis no difference between field potential duration (FPD)
recorded during baseline vs. vehicle measurements(Figure 2B).
AB

Baseline
Vehicle (media; 15min)

500 ms

500 msB

Baseline
30 µM lidocaine (15min)
100 µM lidocaine (15min)

350

400

300

FPD (ms)

FPD (ms)

400

250
200450

***

350

300

300

250
Baseline

500 ms

Vehicle(media)

250

200

200
Baseline

Figure 2: A) Representative EFP traces shown before (baseline) and aftervehicle treatment (light blue). B) Quantification of the FPD before (baseline) and after vehicle application. There is no statistical difference between the two groups.

***

400

350

30µMBaseline

100µM

Figure 3: A) Representative EFP traces shown before (baseline) and after
30 µM (left) or 100 µM (right)lidocaine exposure. B) Quantification of theFPD before (baseline) and after 30 µM (left) or 100 µM (right) lidocaine
exposure.

In summary, CV is related to how fast the membrane
Exposure (15 minutes) to 30 µM and 100 µM lidocaine,
resulted in 8 ± 1% and 15 ± 2% reduction in the estimatedCV, respectively. Figure 3 shows the prolongation of theFPD upon lidocaine exposure (30 µM: 242 ± 4 ms vs. 303 ±9 ms, n = 8, p < 0.005, paired t-test; 100 µM: 240 ± 4 ms vs.
348 ± 12 ms, n = 7, p < 0.005, paired t-test).

depolarizes and sodium channel blockers (like lidocaine)
can reduce CV. Decreasing CV is often used to terminate
arrhythmias caused by re-entry circuits. Therefore, theestablishment of a method to estimate compound
effect on conduction velocity with CardioExcyte 96 is
an important aspect of the study of arrhythmogenesis,
especially where it involves arrhythmias based on reentry6.

ReferencesMethods

1. Veeraraghavan, R., et al. 2014. Am. J. Physiol. HeartCells

Circ. Physiol. 306(5): H619–H627

We thank NEXEL Co., Ltd for providing the cells and the

2. King, J.H. et al. 2013. Front. Physiol. 4: Article 154. doi:

culture media. Cardiosight®-S were handled according

10.3389/fphys.2013.00154

to the manfacturer’s guide provided by Nexel.

3. Rohr, S. 2004. Cardiovasc. Res. 62: 309 – 322
4. Monteiro, L.M., et al. 2017. npj Regen. Med. 2: Article 9.

EFP measurements

doi: 10.1038/s41536-017-0015-2

EFP measurements were conducted according to

5. Doerr, L., et al. J. Lab. Autom. 2015. 20(2): 175-88. doi:

Nanion’s standard procedures for the CardioExcyte 96.

10.1177/2211068214562832.

Cardiosight®-S were plated onto NSP-96 Stim plates. After

6. Janse, M.J. & Wit, A.L. 1989 Physiol. Rev. 69(4):1049-169.

7 days in culture the cardiomyocytes were electricallydoi: 10.1152/physrev.1989.69.4.1049

paced at 1.7 Hz with 1 ms pulse duration. After one hour
under electrical pacing, vehicle or 30 µM and 100 µMlidocaine were added to the cardiomyocytes. EFP signals
were recorded for one hour after compound addition.

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