A

refined

radio-telemetry

technique

to

monitor

right

ventricle

or

pulmonary

artery

pressures

in

rats

a

useful

tool

in

pulmonary

hypertension

research

Implantable

radio-telemetry

methodology

allowing

for

continuous

recording

of

pulmonary

haemodynamics

has

previously

been

used

to

assess

effects

of

therapy

on

development

and

treatment

of

pulmonary

hypertension

In

the

original

procedure

rats

were

subjected

to

invasive

thoracic

surgery

which

imposes

significant

stress

that

may

disturb

critical

aspects

of

the

cardiovascular

system

and

delay

recovery

In

the

present

study

we

describe

and

compare

the

original

trans-thoracic

approach

with

a

new

simpler

trans-diaphragm

approach

for

catheter

placement

which

avoids

the

need

for

surgical

invasion

of

the

thorax

Satisfactory

overall

success

rates

up

to

were

achieved

in

both

approaches

and

right

ventricular

pressures

and

heart

and

respiratory

rates

normalised

within

weeks

However

recovery

was

significantly

faster

in

trans-diaphragm

than

in

trans-thoracic

operated

animals

-LRB-

vs

days

respectively

p

-RRB-

Stable

right

ventricular

pressures

were

recorded

for

more

than

months

and

pressure

changes

induced

by

monocrotaline

or

pulmonary

embolisms

were

readily

detected

The

data

demonstrate

that

right

ventricular

telemetry

is

a

practicable

procedure

and

a

useful

tool

in

pulmonary

hypertension

research

in

rats

especially

when

used

in

combination

with

echocardiography

We

conclude

that

the

described

trans-diaphragm

approach

should

be

considered

as

the

method

of

choice

for

it

is

less

invasive

and

simpler

to

perform

Introduction

Over

the

last

decade

new

medical

treatments

became

available

for

the

treatment

of

pulmonary

hypertension

-LRB-

PH

-RRB-

patients

and

this

development

set

off

a

renewed

interest

in

the

pathophysiology

and

haemodynamics

of

the

pulmonary

circulation

-LSB-

-RSB-

Experimental

PH

studies

are

still

largely

confined

to

single

measurements

of

pulmonary

arterial

-LRB-

PA

-RRB-

or

right

ventricular

-LRB-

RV

-RRB-

pressure

in

anaesthetised

open-chest

animals

undergoing

artificial

respiration

which

does

not

allow

determining

changes

of

pressures

in

time

Measuring

pulmonary

haemodynamics

have

improved

considerably

since

RV

telemetry

was

firstly

introduced

by

Hess

et

al.

-LSB-

-RSB-

as

it

allows

for

continuous

monitoring

of

RV

or

PA

pressures

without

introducing

artefacts

caused

by

stress

or

anaesthetics

-LSB-

-RSB-

Moreover

animals

fitted

with

telemetry

can

serve

as

their

own

controls

thus

permitting

the

use

of

smaller

groups

of

animals

than

is

possible

with

the

single

measurement

approach

in

anaesthetised

animals

-LSB-

-RSB-

Although

many

investigators

have

embraced

this

new

technology

with

enthusiasm

and

despite

its

proven

potential

studies

actually

using

this

methodology

in

rats

are

scarce

-LSB-

-RSB-

One

possible

explanation

for

this

discrepancy

is

that

the

original

procedure

was

only

described

briefly

before

-LSB-

-RSB-

complicating

its

implementation

for

potential

new

users

Secondly

the

described

trans-thoracic

approach

involves

RV

catheterisation

through

complex

and

highly

invasive

thoracotomy

-LSB-

-RSB-

In

the

present

study

we

hypothesised

that

RV

catheterisation

performed

via

an

opening

in

the

diaphragm

thereby

omitting

a

thoracotomy

may

be

a

simpler

less

invasive

alternative

In

the

present

report

we

provide

a

detailed

description

of

the

alternative

trans-diaphragm

approach

together

with

a

comparison

with

the

original

trans-thoracic

approach

Furthermore

we

illustrate

its

usefulness

when

studying

the

pulmonary

circulation

by

presenting

novel

comprehensive

pulmonary

and

cardiac

haemodynamic

data

during

the

development

of

monocrotaline-induced

pulmonary

hypertension

Materials

and

methods

All

experiments

were

approved

by

the

Institutional

Animal

Care

and

Use

Committee

of

the

VU

University

and

were

conducted

in

accordance

with

the

European

Convention

for

the

Protection

of

Vertebrate

Animals

used

for

Experimental

and

Other

Scientific

Purposes

and

the

Dutch

Animal

Experimentation

Act

Animals

Thirty-eight

male

Wistar

rats

were

used

-LRB-

g

Harlan

Horst

The

Netherlands

-RRB-

of

which

were

operated

and

served

as

controls

-LRB-

no

surgery

-RRB-

The

animals

were

allowed

to

adapt

to

their

new

environment

for

at

least

week

before

surgery

The

animals

were

conventionally

housed

in

pairs

under

controlled

conditions

-LRB-

temperature

°C

humidity

h

light

dark

cycle

-RRB-

and

had

free

access

to

filtered

water

and

standard

rat

chow

-LRB-

Global

Harlan

Teklad

Blackthorn-Bicester

England

-RRB-

Telemetry

system

An

implantable

radio-telemetry

system

for

blood

pressure

measurements

for

small

laboratory

animals

was

used

comprising

a

radio-transmitter

-LRB-

-RRB-

fitted

with

a

catheter

-LRB-

Data

Science

International

-LSB-

DSI

-RSB-

St.

Paul

MN

-RRB-

Transmitters

were

turned

on

a

day

before

implantation

and

stored

in

sterilised

saline

following

the

manufacturer

's

instructions

-LRB-

-RRB-

The

pressure

was

monitored

continuously

during

surgery

to

ensure

proper

position

of

the

tip

of

the

pressure

catheter

After

successful

implantation

of

the

transmitter

RV

or

PA

pressures

and

locomotor

activity

were

recorded

for

s

every

min

From

the

pressure

recordings

mean

systolic

and

diastolic

pressure

heart

rate

respiratory

rate

and

circadian

rhythm

were

subsequently

derived

-LRB-

Dataquest

A.R.T.

software

DSI

-RRB-

Pre-operative

care

and

anaesthesia

All

animals

received

pre-surgical

intramuscular

buprenorphine

analgesia

-LRB-

mg/kg

Schering-Plough

Maarssen

The

Netherlands

-RRB-

For

general

anaesthesia

isoflurane

-LRB-

in

mix

Pharmachemie

Haarlem

The

Netherlands

-RRB-

was

used

via

induction

chamber

and

tracheal

intubation

-LRB-

G

Teflon

tube

ventilator

settings

breathing

frequency

pressures

inspiratory/expiratory

ratio

-RRB-

For

extra

local

analgesia

lidocaine

spray

-LRB-

mg/ml

AstraZeneca

Zoetermeer

The

Netherlands

-RRB-

was

applied

at

the

surgical

region

Animals

were

maintained

under

anaesthesia

for

an

average

time

of

min

Animals

were

placed

on

a

heating

pad

to

maintain

body

temperature

and

positioned

in

dorsal

recumbency

Hydromellose

drops

-LRB-

Ratiopharm

Zaandam

The

Netherlands

-RRB-

were

applied

to

prevent

drying

of

the

eyes

After

shaving

and

disinfection

with

ethanol

of

the

chest

and

abdomen

animals

were

covered

with

sterile

incision

foil

and

the

animals

were

then

covered

with

sterile

incision

foil

-LRB-

Opraflex

Lohmann

Rauscher

Almere

The

Netherlands

-RRB-

A

surgical

microscope

was

used

-LRB-

magnification

Carl

Zeiss

Sliedrecht

The

Netherlands

-RRB-

for

optimal

view

Surgery

trans-thoracic

approach

Implantation

of

the

telemetry

transmitter

in

the

abdomen

The

abdominal

cavity

was

accessed

via

a

midline

laparotomy

starting

just

below

the

xiphoid

process

The

transmitter

was

placed

in

the

peritoneal

cavity

with

the

catheter

pointing

caudally

to

prevent

liver

injury

and

tissue

reaction

The

abdominal

cavity

was

covered

with

gauzes

soaked

in

warm

saline

and

left

open

until

the

end

of

the

procedure

Routing

of

the

pressure

catheter

to

the

right

ventricle

The

heart

was

exposed

by

means

of

a

left

thoracotomy

performed

at

the

sixth

intercostal

space

and

mid-clavicular

line

The

thorax

was

opened

with

blunt

scissors

respecting

the

anatomy

of

the

overlying

muscle

layers

and

cautiously

avoiding

injury

to

the

lungs

The

pressure

catheter

was

then

tunnelled

subcutaneously

from

the

peritoneal

cavity

to

the

opening

in

the

thorax

and

temporarily

laid

aside

Four

individual

small

hooks

were

used

to

retract

the

ribs

and

expose

the

heart

through

a

wider

window

The

pericardium

was

then

opened

with

two

dressing

forceps

Catheterisation

of

the

right

ventricle

A

superficial

purse

string

-LRB-

Prolene

Ethicon

St-Stevens-Woluwe

Belgium

-RRB-

was

placed

on

the

right

ventricle

free

wall

near

the

apex

Through

the

purse

string

the

right

ventricle

was

punctured

with

a

G

syringe

needle

in

the

direction

of

the

RV

outflow

tract

avoiding

any

coronary

vessel

After

removing

the

needle

the

site

was

wiped

with

a

sterile

cotton

stick

The

tip

of

the

catheter

was

then

carefully

inserted

into

the

right

ventricle

using

a

vessel

canulation

forceps

-LRB-

mm

outer

diameter

Fine

Science

Tools

Heidelberg

Germany

-RRB-

avoiding

loss

of

gel

from

the

tip

at

all

times

Live

pressure

waveform

trace

confirmed

proper

RV

catheterisation

-LRB-

RV

systolic/diastolic

pressures

are

typically

mmHg

-RRB-

Depending

on

the

protocol

the

pressure

catheter

was

subsequently

advanced

for

about

cm

more

positioning

the

tip

of

the

catheter

beyond

the

pulmonary

valves

Again

live

pressure

waveform

trace

confirmed

correct

positioning

of

the

pressure

catheter

in

the

pulmonary

artery

-LRB-

PA

systolic/diastolic

pressures

are

typically

mmHg

Fig.

left

panel

-RRB-

Finally

the

catheter

was

fixed

by

the

purse

string

and

a

small

drop

of

tissue

adhesive

at

the

site

of

insertion

-LRB-

μl

dispensed

by

a

pipette

Vetbond

St.

Paul

MN

Electronic

Supplementary

Material

-LRB-

ESM

-RRB-

Fig

-RRB-

Fig.

panel

Live

pressure

recordings

while

advancing

the

pressurecatheter

into

the

pulmonary

artery

Notice

the

stepwise

increase

in

diastolic

pressures

when

manoeuvring

the

catheter

beyond

the

pulmonary

valves

-LRB-

arrow

-RRB-

whereas

the

systolic

pressures

remained

unchanged

right

panel

Live

pressure

recordings

while

injecting

a

bolus

injection

of

microspheres

-LRB-

arrow

μm

g

i.v.

-RRB-

Upon

embolisation

a

significant

increase

in

systolic

diastolic

and

developed

RV

pressures

was

observed

Furthermore

in

both

recordings

the

effect

of

breathing

is

noticeable

Closing

of

the

chest

and

abdomen

After

the

catheterisation

blood

clots

if

any

were

removed

from

the

pleural

cavity

with

a

moist

cotton

stick

The

ribs

were

approximated

with

two

individual

sutures

-LRB-

Vicryl

Ethicon

-RRB-

To

promote

full

expansion

of

the

lungs

a

small

burst

of

positive

pressure

was

applied

-LRB-

maximally

for

s

-RRB-

A

chest

tube

-LRB-

G

-RRB-

used

as

air

outlet

was

removed

after

proper

thorax

excursions

were

observed

The

chest

muscles

were

laid

back

in

layers

-LRB-

no

suturing

necessary

-RRB-

Then

the

transmitter

was

sutured

to

the

abdominal

muscle

-LRB-

Perma-Hand

Ethicon

-RRB-

incorporating

the

suture

rib

of

the

device

The

abdominal

wall

was

sutured

in

a

running

subcuticular

pattern

-LRB-

Vicryl

-RRB-

Finally

the

skin

of

the

chest

and

abdomen

was

closed

with

a

running

suture

-LRB-

Vicryl

-RRB-

Surgery

trans-diaphragm

approach

Opening

of

abdomen

and

the

diaphragm

The

abdominal

cavity

was

accessed

via

a

midline

laparotomy

with

the

abdominal

wall

retracted

by

two

individual

hooks

To

expose

the

diaphragm

a

retraction

suture

was

used

to

lift

the

xiphoid

process

during

the

whole

procedure

The

visceral

organs

were

covered

temporarily

with

wet

gazes

and

the

liver

was

gently

pushed

down

by

the

weight

of

a

blade

holder

A

small

midline

incision

in

the

diaphragm

was

then

made

with

small

sharp

scissors

from

the

xiphoid

process

until

the

tendinous

part

of

the

diaphragmatic

membrane

The

two

sides

of

the

diaphragm

were

held

aside

with

two

retraction

sutures

providing

optimal

exposure

of

the

heart

-LRB-

ESM

Fig

-RRB-

Catheterisation

of

the

right

ventricle

RV

catheterisation

was

performed

similarly

as

described

above

In

short

the

pericardium

was

opened

by

two

dressing

forceps

and

a

purse

string

was

placed

just

right

of

the

apex

The

pressure

catheter

was

then

inserted

into

the

right

ventricle

through

a

small

puncture

made

with

a

syringe

needle

and

fixed

in

place

Closing

the

diaphragm

and

abdomen

After

catheterisation

blood

clots

in

the

thorax

if

any

were

removed

The

diaphragm

was

closed

with

a

running

suture

-LRB-

Vicryl

-RRB-

starting

from

the

ventral

side

with

the

pressure

catheter

sticking

out

the

diaphragm

at

the

dorsal

end

of

the

incision

After

that

the

retraction

suture

through

the

xiphoid

process

was

removed

To

promote

full

expansion

of

the

lungs

a

small

burst

of

positive

pressure

was

applied

as

described

above

with

the

chest

tube

between

the

sutures

of

the

diaphragm

until

proper

thorax

excursions

were

visually

confirmed

To

further

secure

closure

of

the

diaphragm

a

small

amount

of

tissue

adhesive

-LRB-

Vetbond

-RRB-

was

applied

Finally

the

transmitter

was

implanted

in

the

peritoneal

cavity

fixed

to

the

abdominal

wall

with

the

catheter

facing

caudally

and

the

abdomen

was

closed

as

described

above

Post-operative

care

To

compensate

for

loss

of

fluids

all

animals

received

warm

sterile

saline

at

the

end

of

the

procedure

-LRB-

ml

intraperitoneal

-RRB-

After

final

skin

closure

the

animals

were

allowed

to

regain

consciousness

In

the

first

h

of

recovery

the

animals

were

housed

in

individual

cages

Each

cage

was

placed

halfway

on

a

heating

pad

in

such

a

way

that

half

of

the

cage

was

maintained

above

it

and

the

other

at

room

temperature

During

this

period

the

animals

were

monitored

three

times

received

post-surgical

analgesia

when

clinically

indicated

-LRB-

buprenorphine

mg/kg

subcutaneous

-RRB-

and

were

provided

with

drinking

gel

pads

and

softened

rat

chow

After

h

the

animals

were

conventionally

housed

in

pairs

for

a

full

recovery

and

they

were

inspected

and

weighted

daily

Animals

were

considered

fully

recovered

from

surgery

when

their

appearance

and

behaviour

were

normal

their

surgical

wounds

healed

their

pre-surgical

body

weight

regained

when

the

pressures

normalised

and

circadian

rhythm

was

restored

The

study

period

was

ended

after

months

Experimental

protocol

To

induce

acute

and

chronic

pulmonary

hypertension

four

animal

received

an

intravenous

bolus

injection

of

microspheres

-LSB-

-RSB-

-LRB-

tail

million

g

body

mass

in

sterile

saline

polystyrene

mean

diameter

μm

-LRB-

-RRB-

Duke

Scientific

Fremont

CA

-RRB-

and

three

animals

monocrotaline

subcutaneous

-LSB-

-RSB-

-LRB-

MCT

mg/kg

in

sterile

saline

Sigma-Aldrich

Zwijndrecht

The

Netherlands

-RRB-

respectively

Experimental

interventions

were

performed

no

earlier

then

weeks

after

the

surgery

RV

echocardiography

After

a

recovery

trans-thoracic

echocardiographic

measurements

-LRB-

ProSound

system

equipped

with

a

linear

transducer

-LSB-

-RSB-

Aloka

Tokyo

Japan

-RRB-

were

performed

on

anaesthetised

but

spontaneously

breathing

rats

-LRB-

isoflurane

in

mix

-RRB-

according

to

the

standards

of

the

American

Society

of

Echocardiography

-LSB-

-RSB-

To

minimise

the

effects

of

isoflurane

on

cardiac

function

the

time

under

anaesthesia

was

set

to

a

maximum

of

min

-LSB-

-RSB-

The

measurements

were

compared

with

untreated

rats

to

check

for

possible

adverse

effects

related

to

the

procedure

Cardiac

output

tricuspid

annular

plane

systolic

excursion

-LRB-

TAPSE

-RRB-

RV

wall

thickness

-LRB-

RVWT

-RRB-

and

RV

end

diastolic

diameter

-LRB-

RVEDD

-RRB-

were

measured

as

described

before

by

Hardziyenka

et

al.

-LSB-

-RSB-

TAPSE

is

a

parameter

for

RV

systolic

function

which

is

measured

in

the

apical

four-chamber

view

of

the

heart

and

expresses

the

displacement

of

the

lateral

tricuspid

annulus

towards

the

apex

during

systole

-LSB-

-RSB-

Estimation

of

pulmonary

vascular

resistance

and

RV

power

output

Additional

echocardiographic

measurements

were

performed

in

MCT-treated

rats

and

untreated

but

operated

controls

just

before

the

injection

weeks

after

injection

and

when

the

first

clinical

signs

of

RV

heart

failure

developed

-LRB-

as

indicated

by

weight

loss

dyspnoea

and

lethargy

after

which

the

rats

were

euthanised

-RRB-

Pulmonary

vascular

resistance

-LRB-

PVR

-RRB-

and

RV

power

output

-LRB-

RV-power

-RRB-

were

estimated

by

combining

telemetric

pressure

data

and

echocardiographic

flow

data

PVR

was

estimated

by

Poiseuille

's

law

-LSB-

PVR

-RSB-

-LSB-

mean

PAP

-RSB-

-LSB-

cardiac

output

-RSB-

-LRB-

-LSB-

systolic

RV

pressure

-RSB-

mmHg

-RRB-

-LSB-

cardiac

output

-RSB-

-LSB-

-RSB-

RV-power

was

estimated

using

a

simplified

pressure

volume

analysis

assuming

rectangular

pressure

volume

loops

-LSB-

RV-power

-RSB-

-LSB-

systolic

RV

pressure

-RSB-

-LSB-

stroke

volume

-RSB-

-LSB-

heart

rate

-RSB-

-LSB-

systolic

RV

pressure

-RSB-

-LSB-

cardiac

output

-RSB-

-LSB-

-RSB-

Autopsy

To

investigate

potential

effects

of

chronic

implantation

of

the

telemetry

transmitters

the

animals

were

euthanised

at

the

end

of

the

study

protocol

by

exsanguination

under

isoflurane

-LRB-

in

mix

-RRB-

Macroscopic

examination

of

right

ventricle

lungs

diaphragm

and

intercostal

muscles

were

performed

and

organ

weights

-LRB-

heart

lungs

liver

spleen

kidneys

-RRB-

were

measured

and

compared

with

controls

Animals

treated

with

MCT

or

microspheres

were

excluded

from

these

analyses

Statistical

analyses

All

measurements

unless

otherwise

stated

are

presented

as

mean

standard

error

of

the

mean

Normal

distribution

was

verified

and

Student

's

t

test

analysis

of

variance

or

Fisher

Exact

test

were

used

when

appropriate

-LRB-

SPSS

SPSS

Chicago

IL

-RRB-

A

p

value

less

than

was

considered

statistically

significant

Results

Success

rate

Seventeen

animals

were

operated

using

the

trans-thoracic

approach

and

animals

were

operated

using

the

trans-diaphragm

approach

In

the

trans-thoracic

group

animals

showed

stable

pressure

signals

for

the

whole

study

period

of

months

Five

animals

did

not

recover

form

surgery

and

animals

developed

instable

pressure

signals

caused

by

clot

formation

inside

the

pressure

catheter

within

weeks

of

recovery

Of

the

failed

procedures

occured

in

the

first

four

attempts

In

the

trans-diaphragm

group

animals

showed

stable

pressure

signal

for

the

whole

study

period

of

months

Six

animals

did

not

recover

form

surgery

and

one

animal

developed

instable

pressure

signals

caused

by

clot

formation

inside

the

pressure

catheter

within

weeks

of

recovery

As

in

the

trans-thoracic

group

of

the

failures

occurred

in

the

first

four

attempts

By

discarding

the

first

animals

in

each

procedure

as

we

consider

this

the

learning

curve

the

overall

success

rate

was

of

-LRB-

-RRB-

for

the

trans-thoracic

approach

and

of

-LRB-

-RRB-

for

the

trans-diaphragm

approach

Recovery

from

surgery

Within

a

week

post-surgery

heart

and

respiratory

rates

and

circadian

rhythm

normalised

in

all

rats

and

no

differences

were

observed

between

the

two

approaches

-LRB-

Table

-RRB-

Although

all

animals

regained

their

pre-surgical

body

weight

within

weeks

full

recovery

was

significantly

faster

in

the

trans-diaphragm

than

the

trans-thoracic-operated

animals

-LRB-

vs

days

respectively

p

-RRB-

Table

results

of

this

study

all

values

in

mean

SEM

Trans-thoracic

approach

-LRB-

n

-RRB-

Trans-diaphragm

approach

-LRB-

n

-RRB-

Controls

-LRB-

n

-RRB-

Success

-LRB-

-RRB-

-LRB-

-RRB-

n.r.Recovery

BW

to

pre-surgical

level

-LRB-

days

-RRB-

n.r.

Heart

rate

-LRB-

bpm

-RRB-

-LSB-

-RSB-

Respiratory

rate

-LRB-

rpm

-RRB-

-LSB-

-RSB-

Circadian

rhythm

-LRB-

days

-RRB-

n.r.Pressurese

RVSP

-LRB-

mmHg

-RRB-

-LSB-

-RSB-

RVDP

-LRB-

mmHg

-RRB-

-LSB-

-RSB-

RV

echocardiographyd

Cardiac

output

-LRB-

ml/min

-RRB-

TAPSE

-LRB-

mm

-RRB-

RVWT

-LRB-

mm

-RRB-

RVEDD

-LRB-

mm

-RRB-

Autopsyf

organ

weights

-LRB-

g

-RRB-

n

Number

of

animals

n.r.

not

relevant

BM

body

mass

RVSP

RV

systolic

pressure

RVDP

RV

diastolic

pressure

TAPSE

tricuspid

annular

plane

systolic

excursion

RVWT

RV

wall

thickness

RVEDD

RV

end

diastolic

diameter

p

aFirst

four

attempts

were

discarded.bNormal

values

for

Wistar

rats

awake

and

at

rest

measured

by

radio-telemetrycNormal

values

for

Wistar

rats

measured

during

acute

pressure

measurements

under

anaesthesiadAnalyses

on

surviving

animals

onlyeAnalyses

on

successfully

operated

animals

only

-LRB-

stable

signal

-RRB-

fAnalyses

on

surviving

and

untreated

animals

only

-LRB-

no

microspheres

or

monocrotaline

-RRB-

RV

pressures

normalised

in

all

animals

within

weeks

after

surgery

-LRB-

RV

systolic/diastolic

pressures

mmHg

-RRB-

irrespective

of

the

method

used

-LRB-

Table

-RRB-

PA

systolic/diastolic

pressures

were

estimated

to

be

mmHg

-LRB-

Fig.

left

panel

-RRB-

Activity

had

no

significant

effect

on

the

stability

of

the

pressure

signals

Echocardiography

revealed

normal

cardiac

output

-LRB-

ml/min

-RRB-

TAPSE

-LRB-

mm

-RRB-

RVWT

-LRB-

mm

-RRB-

and

RVEDD

-LRB-

mm

-RRB-

in

all

rats

and

no

differences

were

seen

between

the

differently

operated

animals

and

controls

-LRB-

Table

-RRB-

Furthermore

other

signs

of

RV

dysfunction

like

pericardial

effusion

and

tricuspid

regurgitation

were

not

present

in

any

animal

Acute

pressure

effects

of

pulmonary

embolisation

by

microspheres

RV

telemetry

could

readily

detect

acute

changes

in

RV

pressure

induced

by

a

bolus

injection

of

microspheres

-LRB-

Fig.

right

panel

-RRB-

Upon

embolisation

systolic

RV

pressures

increased

from

to

mmHg

-LRB-

p

-RRB-

and

diastolic

RV

pressures

increased

from

to

mmHg

-LRB-

p

-RRB-

Haemodynamic

changes

during

the

development

of

MCT-induced

pulmonary

hypertension

Changes

in

haemodynamic

parameters

during

the

development

of

MCT-induced

PH

are

shown

in

Fig.

-LRB-

also

in

ESM

Fig

-RRB-

Four

weeks

after

MCT

injection

the

first

clinical

signs

of

RV

heart

failure

developed

During

this

period

there

was

a

gradual

rise

in

RV

systolic

pressure

from

mmHg

at

baseline

to

mmHg

at

weeks

and

mmHg

at

weeks

-LRB-

p

vs

control

-RRB-

At

weeks

cardiac

output

dropped

dramatically

from

ml/min

at

baseline

to

at

weeks

and

ml/min

at

weeks

-LRB-

p

vs

control

-RRB-

In

addition

the

poor

haemodynamic

condition

of

the

MCT-treated

rats

at

weeks

was

confirmed

by

a

simultaneous

decline

in

TAPSE

from

mm

during

the

first

weeks

to

mm

at

weeks

-LRB-

p

vs

control

-RRB-

During

the

development

of

PH

the

right

ventricle

remodelled

initially

by

increasing

RVWT

-LRB-

mm

at

baseline

mm

at

weeks

and

mm

at

weeks

respectively

p

vs

control

-RRB-

but

subsequently

by

increasing

RVEDDs

as

well

-LRB-

mm

at

baseline

mm

at

weeks

and

mm

at

weeks

respectively

p

vs

control

-RRB-

Fig.

changes

during

the

development

of

MCT-induced

pulmonary

hypertension

Four

weeks

after

the

rats

received

MCT

clinical

signs

of

RV

heart

failure

developed

In

these

weeks

systolic

pressures

continued

to

rise

while

cardiac

output

could

not

be

maintained

The

presence

of

RV

remodelling

was

indicated

by

increased

wall

thickness

and

diameter

The

pulmonary

vascular

resistance

continued

to

rise

as

well

while

at

weeks

the

increase

in

the

RV-power

was

inadequate

to

compensate

for

the

dramatically

increased

afterload

Triangles

connected

by

dashed

lines

MCT-treated

squares

connected

by

uninterrupted

lines

control

group

n

for

both

groups

All

values

are

in

mean

SEM

Asterisk

p

double

asterisk

p

compared

to

control

-LRB-

post-hoc

analyses

-RRB-

Please

note

that

sometimes

the

icons

conceal

the

error

bars

For

explanation

of

the

abbreviations

see

corresponding

text

During

the

development

of

PH

PVR

increased

continuously

from

N

m

s

at

baseline

to

N

m

s

at

weeks

and

N

m

s

at

weeks

-LRB-

p

vs

control

-RRB-

RV-power

was

increased

at

weeks

but

no

further

increase

was

seen

at

weeks

-LRB-

RV-power

mW

at

baseline

mW

at

weeks

mW

at

weeks

respectively

p

vs

controls

-RRB-

Autopsy

Chronic

implantation

of

the

telemetry

transmitter

in

both

approaches

did

not

result

in

any

differences

in

organ

weight

as

compared

to

control

-LRB-

Table

-RRB-

and

no

apparent

pulmonary

embolisms

were

seen

Autopsy

revealed

only

local

fibrosis

of

the

right

ventricle

near

the

insertion

point

of

the

catheter

-LRB-

ESM

Fig

-RRB-

In

the

trans-thoracic

approach

animals

showed

normal

healing

of

the

intercostal

muscles

In

the

trans-diaphragm

approach

no

herniation

or

dehiscence

of

the

diaphragm

were

seen

in

any

animal

and

often

the

liver

was

partially

accreted

to

the

healed

wound

of

the

diaphragm

-LRB-

ESM

Fig

-RRB-

Discussion

The

present

study

describes

in

detail

two

surgical

techniques

to

monitor

RV

or

PA

pressures

over

time

by

radio-telemetry

in

rats

To

our

best

knowledge

we

are

the

first

research

group

to

describe

the

trans-diaphragm

approach

and

its

comparison

with

the

previously

used

trans-thoracic

approach

We

have

demonstrated

that

-LRB-

-RRB-

in

our

hands

both

the

trans-diaphragm

as

well

as

the

trans-thoracic

approach

have

satisfactory

success

rates

especially

when

considering

the

complexity

of

the

procedures

-LRB-

-RRB-

the

time-to-recovery

was

significantly

shorter

with

the

trans-diaphragm

approach

than

the

trans-thoracic

approach

-LRB-

-RRB-

measured

physiological

parameters

recovered

fully

in

both

methods

and

there

were

no

permanent

detrimental

effects

on

RV

intercostal

muscles

or

diaphragm

-LRB-

-RRB-

using

RV-telemetry

acute

and

chronic

pressure

changes

in

the

pulmonary

circulation

can

be

readily

detected

and

-LRB-

-RRB-

RV-telemetry

in

combination

with

echocardiography

allow

thorough

monitoring

of

pulmonary

and

cardiac

haemodynamic

changes

over

time

Fully

recovered

animals

showed

normal

RV

structure

as

expressed

by

RVWT

and

RVEDD

and

normal

function

as

expressed

by

cardiac

output

and

TAPSE

In

addition

in

both

approaches

RV

pressure

normalised

shortly

after

surgery

and

autopsy

revealed

only

minor

fibrosis

in

the

direct

proximity

of

the

catheter

Therefore

permanent

detrimental

effects

of

RV-telemetry

on

the

RV

can

be

excluded

for

both

techniques

In

addition

examination

of

other

organs

revealed

no

abnormalities

as

was

described

by

others

-LSB-

-RSB-

In

animals

operated

using

the

trans-diaphragm

approach

macroscopic

examination

revealed

normal

wound

healing

of

the

diaphragm

Although

we

have

not

tested

the

strength

of

the

healed

diaphragm

others

did

not

find

significant

differences

between

a

normal

-LRB-

untouched

-RRB-

and

a

sutured

diaphragm

-LSB-

-RSB-

The

natural

history

of

small

defects

in

the

diaphragm

is

relatively

benign

as

they

almost

always

heal

spontaneously

-LSB-

-RSB-

especially

when

the

diaphragm

is

fixated

by

other

organs

-LSB-

-RSB-

Furthermore

the

observation

of

a

normal

respiratory

rate

seen

in

the

recovered

animals

confirms

that

the

trans-diaphragm

approach

is

safe

and

a

good

alternative

for

the

trans-thoracic

approach

In

our

experience

insertion

of

the

pressure

catheter

into

the

RV

and

its

advance

further

into

the

pulmonary

artery

when

desired

is

comparatively

easy

to

perform

in

the

trans-diaphragm

approach

This

relative

ease

of

RV

catheterisation

is

reflected

in

the

higher

success

rate

compared

to

the

trans-thoracic

approach

and

might

be

well

explained

by

the

more

caudal

and

inferior

direction

by

which

the

catheter

enters

the

heart

Approaching

the

heart

in

this

manner

entails

minimal

manipulation

and

manoeuvring

of

the

catheter

during

the

process

of

RV

catheterisation

resulting

in

a

lower

incidence

of

clot

formation

inside

the

catheter

This

complication

occurred

more

frequently

in

trans-thoracic-operated

animals

as

a

direct

consequence

of

excessive

manoeuvring

and

accidental

squeezing

of

the

catheter

causing

it

to

lose

or

displace

some

of

its

anti-thrombolitic

gel

The

strongest

advocate

of

the

trans-diaphragm

approach

over

the

trans-thoracic

approach

however

is

the

significantly

faster

recovery

of

the

animals

Prompt

recovery

from

surgery

is

particularly

important

in

rats

with

MCT-induced

PH

because

of

low

survival

rates

beyond

weeks

after

MCT

injection

In

this

study

we

used

echocardiography

to

validate

RV-telemetry

in

vivo

Additionally

through

the

combination

of

pressure

data

obtained

by

RV-telemetry

with

echo-Doppler

flow

data

we

were

able

to

study

the

haemodynamics

of

the

pulmonary

circulation

in

greater

detail

-LSB-

-RSB-

MCT

induced

pulmonary

and

cardiac

remodelling

at

the

same

time

as

PVR

RVWT

and

RVEDD

increased

Cardiac

adaptation

to

overcome

the

increasing

afterload

became

inadequate

by

the

fourth

week

of

MCT

injection

in

such

that

there

was

no

further

increase

in

RV-power

to

maintain

adequate

cardiac

output

while

RV

systolic

pressure

continued

to

rise

Detailed

studies

of

these

observations

are

planned

for

the

near

future

In

the

present

study

we

have

focussed

on

the

refinement

of

the

RV-telemetry

technique

in

rats

but

this

does

not

exclude

its

applicability

in

mice

and

other

rodents

Indeed

in

their

recent

study

Schwenke

et

al.

-LSB-

-RSB-

reported

long-term

monitoring

of

PA

pressure

in

mice

using

radio-telemetry

In

conclusion

we

described

a

new

easier-to-perform

mildly

invasive

trans-diaphragm-based

RV-telemetry

approach

for

long-term

monitoring

of

PA

and

RV

pressures

in

the

rat

model

of

MCT-induced

PH.

Our

findings

may

be

applied

to

improve

our

understanding

of

the

disease

processes

involved

in

PH

and

develop

better

treatment

strategies

for

the

disease

Electronic

supplementary

material

Below

is

the

link

to

the

electronic

supplementary

material

Electronic

Supplementary

Material

M.L.

Handoko

et

al.

A

refined

radio-telemetry

technique

to

monitor

right

ventricle

or

pulmonary

artery

pressures

in

rats

Pflugers

Arcg

Eur

J

Physiol

Fig

-LRB-

PDF

kb

-RRB-

O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O

blood pressure
heart
pulmonary artery
diaphragm
cardiac output
power output
circulation
respiration