Science - USA (2022-05-27)

of vibrotactile input ( 20 ). The respiratory mod-
ule mounts at the suprasternal notch to capture
physical activity, body temperature, and res-
piratory behavior in a dual-sensing design
for accurate operation ( 21 ). The hemodynamic

module on the forehead measures peripheral

bloodoxygensaturation(SpO 2 )( 22 ).

Figure 2H shows a block diagram of the

skin-interfaced cardiac module. An ECG ana-

log front end (AFE) and a microcontroller unit

(MCU) process measured data in real time to

calculate the HR (fig. S15). A BLE-enabled user

interfaceservesasacontrolunitthatstores

and displays ECG tracings and three-axis ac-

celeration data associated with cardiac and

Choiet al., Science 376 , 1006–1012 (2022) 27 May 2022 4of7

0

120

(ms

)

C

D

Monitor

ECG

Calculate

heart rate

Heart rate

< Lower rate limit

E-stimulation

on

Check the electrical

stimulation

Ye s

No

Duration

< setting value

On

Off Ye s

E-stimulation

off

No

heart

Ventricles

Pacemaker

electrode

Electrode

point of

contact

A

ECG monitoring cable

Human

whole

heart

Cannula

Bioresorbable Control module

module

B

0 20 40 60 80 100 120 140

-2

0

2

4

ECG (mV)

40

50

60

70

80

Time (s)

demmargorP )mpb( etar

traeh

Lower rate limit

= 54 bpm

Recover the heart rate

during pacing

~ 70 ~ 60 ~ 50 ~ 100 ~ 50 ~ 100 ~ 50 ~ 100 ~ 60

Measured heart rate (bpm) Pacing

E

Pacing duration

= 10 s

On Off On Off On Off

Temporary bradycardia

Heart rate

> Higher rate limit

No

Ye s

Cardiac

module

5 cm 5 mm

Fig. 3. Treatment of temporary bradycardia.(A andB) Schematic illustration (A) and photograph (B) of a Langendorff-perfused human whole-heart model with a
transient closed-loop system (dcoil= 25 mm). (C) Action potential maps obtained by optical mapping of the human epicardium. (D) Flow chart of closed-loop
hysteresis pacing to activate the pacemaker upon automatic detection of temporary bradycardia (supplementary text 8). (E) Programmed HR (top) and measured
ECG (bottom) of a human whole heart. Set parameters are as follows: The lower rate limit is 54 bpm, pacing duration is 10 s, and pacing rate is 100 bpm.

RESEARCH | REPORT