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