Supporting Information S1

Supporting Information S1 Original recordings and analysis Original recordings of contraction patterns of four EHTs are presented under baseline condition and in the presence of proarrhythmic compounds. E-4031 original recordings E-4031 baseline

E-4031 1 nM

E-4031 3 nM

E-4031 10 nM

E-4031 30 nM

Analysis E-4031 Force

BPM

*

Contraction velocity (mN/33 millisec)

*

50 40 30 20

0.050

0.025

10

0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00

E4 03 1

E4 03 1

30

nM

ba se lin e E4 03 1 1 nM E4 03 1 3 nM E4 03 1 10 nM E4 03 1 30 nM

*

T1

*

*

nM

nM E4 03 1

Relaxation velocity 0.3

10

3

1

E4 03 1

E4 03 1

E4 03 1

E4 03 1

30

ba se lin e

nM

nM

nM

10

3 E4 03 1

E4 03 1

e

nM 1

E4 03 1

ba se lin E4 03 1

nM

0.000

0

T2

0.2

*

0.35

*

*

*

0.30

0.1

T2 (sec)

0.25

0.2

T1 (sec)

0.1

0.20 0.15 0.10 0.05

nM

nM

30 E4 03 1

10 E4 03 1

3

nM

nM 1

E4 03 1

ba se lin e E4 03 1

E4 03 1

nM

nM

30 E4 03 1

10

3

nM E4 03 1

E4 03 1

E4 03 1

1

ba se lin e

nM

nM

30 E4 03 1

E4 03 1

E4 03 1

3

10

nM

nM 1

E4 03 1

ba se lin e E4 03 1

0.00

nM

0.0

0.0

E4 03 1

Relaxation velocity (mN/33 millisec)

Contraction velocity

0.075

* Force (mN)

Beats per minute

60

Analysis of contraction. *P