Transcranial Doppler (TCD) - PowerPoint Presentation

Slide1

Transcranial Doppler (TCD) scan&Stroke risk assessment

Dr. Ijeoma N. Akinwumi

(

FMCPaed

, MSc.

Haemoglobinopathy

)

Lagos State University College of Medicine/ Teaching Hospital,

Ikeja

Lagos

Slide2

Stroke risk assessmentStroke is a vascular event with neurological

sequelae

.

Only the ischaemic type predominant in childhood SCD

can be predicted.

Comprehensive

care & hence routine practice - UK,

USA

and

other countries dealing with

SCD includes TCD

ischaemic stroke risk assessment/ screening.

Identify

asymptomatic

children at greatest risk for ischaemic stroke

Prevent an initial stroke by offering preventive intervention = Primary stroke prevention

Secondary

stroke prevention – prevention of recurrence

Slide3

Cost of StrokeMorbidity

Prevents achievement of expected independence and full potential

Adversely affects the quality of life

Imposes emotional, physical, psychosocial and financial burdens on their family, society

Financial burden to the healthcare system

Mortality

PREVENTION IS DESIRABLE!!

Stroke risk assessment is EXTREMELY IMPORTANT.

Steinlin

et al, 2012

Slide4

Epidemiology of childhood StrokeRare

worldwide

, approx 0.003%

SCD is a major contributor

- HbSS>>

HbSC

.

Ischaemic or haemorrhagic or combined

In SCD

Peak incidence of 1st stroke



age 2-5yrs

Most before 10yrs and

rare below age 1

yr

By age 20 years – 11%.

(

Ganesan

et al, 2002; Kirkham et al, 2004;

Mallick

and O’Callaghan, 2010;

Ohene-Frempong

et al, 1998)

Slide5

SCD related stroke in Nigeria

Clinical stroke rate is 5-8.4% of affected children

14-20% of children die.

Recurrence rate 26 - 75%

2/3

rd

survivors - lifelong handicaps

28% stroke related epilepsy & 26% school dropout rate (hosp based data)

Also unreported strokes & deaths in community

Fatunde

, 2005; Kehinde, 2008; Lagunju &Brown, 2012

Slide6

History of Stroke risk assessment

Aaslid

et al, 1982,

1

st

recommended time averaged mean max velocity (TAMMV) in cm/sec for occlusive cerebral artery disease

- less vulnerable to

haemodynamic

changes

- corresponds better to cerebral perfusion & ideal for categorization of stroke risk.

Adams et al, 1992

predicted stroke risk using non-imaging transcranial Doppler techniques

Ohene-Frempong

et al 1998

– Risk factors for CVA in SCD from 20yr natural

hx

study of 4,000 pts (0- 45yrs)

Adams et al, 1998

(STOP trial)-RCT blood transfusion

vs

standard treatment, outcome – stroke

Nichols et al, 2001

developed STOP Guidelines categorising and indicating need for intervention

Slide7

Large artery vasculopathyVessels of the Circle of Willis, notably:Internal carotid artery (ICA)

Middle cerebral artery (MCA) in 85% (training)

Anterior cerebral artery (ACA)

Rarely,

Posterior cerebral artery (least likely, ≤1%) - often not studied.

Slide8

Slide9

Risk factors for ischaemic strokeClinical (history, exam)

Age

: peak at 2-5

yrs

,

most before age 16 years

Siblings with SCD and Stroke

Low arterial oxygen saturation (SPO

2

)

Relative systemic hypertension (SCD normal is lower)

Acute chest syndrome in preceding 2wks or frequently >2 times per annum

Transient Ischaemic attacks

Infections,

esp

meningitis

Ohene-Fremong

et al, 1998

Slide10

Risk factors continuedLaboratory

Low steady state Hb concentration/ PCV

High leukocyte count

High reticulocyte count

Elevated serum bilirubin and LDH

Imaging/ radiological

High cerebral artery flow velocity/ Abnormal TCD study ( TAMMV ≥200cm/s)

Now used as proxy for stroke risk and correlates well

with other risk factors.

MRI –

Moya

moya

, Silent cerebral infarct

Ohene-Fremong

et al, 1998;

Pegelow

et al, 2002

Slide11

Eligibility for TCD screening(Nichols et al, 2001).

The STOP guidelines listed clinical conditions which may

affect the authenticity of TCD studies

Erroneously low TCD velocity:

Recent blood transfusion

may reduce HbS % -

hypocarbia

can lower TCD velocities below a patient’s baseline.

Erroneously high TCD velocity:

hypoxia

,

hypoglycaemia

,

hypercarbia

,

fever

acute anaemic / pain

acrisis

may increase cerebral blood flow and TCD velocity

Recommendation: Asymptomatic child in steady state.

Slide12

STOP Guidelines for interpretation (Nichols et al 2001)

The criteria for classification were based on TAMMV flow in any one of the distal ICA, proximal MCA or ACA (highest determines)

1) Normal: when TAMMV< 170 cm/sec;

2) Conditional: when TAMMV ≥170 but < 200 cm/sec, and

3) High risk: when TAMMV ≥ 200 cm/sec.

Repeat TCD scans two weeks later for high risk subjects.

Slide13

Interpretation of TCDHighest TAMMV in any studied artery determines category

TAMMV ≥200cm/s (high risk/ abnormal TCD)- 40% risk of stroke in 2 yrs

TAMMV ≥ 170cm/s but < 199cm/s (conditional risk) – 7%

standard 2% stroke risk as in the general SCD population was reported in children with TAMMV <170cm/s (normal TCD)

(Adams et al, 1997; Adams et al, 1998).

Slide14

Interpretation contdSubjects prone to overt stroke could also have a TAMMV <70cm/s in their MCA velocity

Inadequate study despite adequate temporal window or

A comparison of non-imaging TCD and MRI/ MRA suggest

these findings are indicative of vasculopathy.

This category not included in STOP guidelines

Use to MRI/ MRA to confirm vascular

stenosis

before transfusions therapy is commenced

(Adams et al, 1992; Seibert et al, 1993; Seibert et al, 1998).

Slide15

Non-imaging TCD - ProcedureWell patient (steady state if possible) - supine, awake and quiet, not sedated

2MHz ultrasound probe aligned with a specific cerebral artery blindly

via thin temporal bone (window) above the

zygomatic

arch - Temporal

insonation

window

Slide16

OptimizationThe machine records and saves the TAMMV in the ICA, ACA and MCA at maximal sound

pitch.

For

accuracy

probe angle is adjusted manually & depth

and

penetration

power

of

ultrasound

waves adjusted by

hand held remote

Control until highest

sound pitch is

obtained

diff for each

vessel

The amplitude of the wave form measured & recorded on a screen over time correlates directly with the speed of the blood in cm/sec

Corresponds to time averaged maximum mean velocity (TAMMV)

Slide17

TCD equipment

Slide18

EQUIPMENT (CONTD)

Slide19

Slide20

High risk TCD waveforms – Rt MCA

Slide21

Risk conversion (counselling)Reversion from high risk category – without intervention

In 2yrs, 4% of standard risk

grp

can change to high risk

50% of

conditonal

risk group can

convet

to high risk in a 2yr period

Need for continued regular TCD screening till age 16yrs

NOTE: Up to 20% may sustain high risk status without stroke for over 2 years, also false positive results

<10% may not respond to transfusion Rx at all

Adams et al, 2006; Zimmerman et al 2007;

Kwiatoskwy

et al, 2011

Slide22

Management of High risk groupSCA predominantly, only 1 case of stroke in

HbSC

in Nigeria - Lagos

– Monthly exchange blood transfusion/ top up transfusion with red cells and

chelation

therapy

– HbS <30% of total Hb

– reduce sickling and haemolysis

– Maintain pre-transfusion total Hb at 12g/dl max

– rapid initial reduction of TAMMV

–change category in 3months (5cm/s)-6 months(38cm/s)

– subsequently reverse/ reduce occlusive vasculopathy

Adams et al, 1998;

Kwiatkowsky

et al, 2011

Slide23

Ischaemic stroke preventionTranscranial Doppler Ultrasound identifies

asymptomatic high risk patients in children 2-

16yrs old (epidemiology, co-operation, temporal

insonation

window)

Pre- an post-TCD counselling

Chronic episodic red cell transfusion prevents up to 90% of initial ischaemic strokes

Hydroxyurea (HU)/ Hydroxycarbamide

Slide24

Update of management of high stroke risk

Hydroxyurea (HU)/ Hydroxycarbamide escalated to maximal tolerable dose (MTD)

Works and very

useful,

trials

underway for exact figures,

Galadanci

et al, 2016 -acceptable & efficacious.

Ware et al, 2016 - HU vs. Chr Transf Tx - Nichols et al, 2001 – STOP guidelines for stroke risk assessment and primary stroke prevention

Slide25

Stopping blood transfusions (counselling)

STOP 2 trial to determine at when to stop

bld

Tx

and SWiTCH trial – stop blood

 Hydroxyurea

– high stroke rate, death

– overwhelming evidence of adverse outcome

– trial discontinued prematurely

These were RCTs.

Recommendation remains – continue blood Tx till at least

age 16-18 yrs.

Adams et al, 2005; Ware et al, 2004

Slide26

Stopping Blood transfusion: 2016 updateFor high-risk children with sickle cell anaemia and abnormal TCD velocities who have received at least 1 year of transfusions, and have no MRA-defined severe

vasculopathy

,

hydroxycarbamide

treatment can substitute for chronic transfusions to maintain TCD velocities and help to prevent primary

stroke.

– Ware et el, 2016

1yr OVERLAP of both red cell transfusions & HU

Slide27

Stroke risk assessment in Nigeria

Standard practice in UK, USA, some other SCD

burdened countries.

Stroke risk assessment & chronic blood transfusion has

drastically reduced America’s childhood SCD stroke rate

Efforts to standardize SCD care are underway in Nigeria

Not available in most dedicated SCD clinics in Nigeria

Relatively

new to Nigeria, not practiced routinely

Standard stroke risk assessment resources – SCD – 3

places in Nigeria (Sickle cell Foundation,

Idia-Araba

,

Gbagada

General hospital both in Lagos & UCH Ibadan)

Fullerton, 2004;

Galadanchi

et al, 2013

Slide28

Non- imaging TCD Studies in South west Nigeria

High risk patients to STOP guidelines using similar

equipment and protocol:

4.7% - 8% in Ibadan – Lagunju et al, 2011, 2013.

9.6

% -

Ojewumi

&

Adeyemo

et al 2016,

9.8%–,

Diaku

-Akinwumi et al, &

11% in Lagos

Adekunle

&

Diaku

-Akinwumi et al

Blood

transfusion not acceptable/ sustainable

All studies -

Conditional risk – 20% and

Majority are standard

risk ≥70

%

Slide29

Caution!Interpretations discussed are for NON-IMAGING TCD

- quick procedure with portable , relatively inexpensive TCD unit

- easy to teach non-clinical staff in few days, skills improve with time

IMAGING TCD using a colour Doppler machine

- can be achieved with most standard ultrasound equipment if performed by an expert

- visualizes and identifies vessels more confidently

BUT - expensive machines with larger transducers-not suitable for small temporal windows of children.

Bullas

, 2005; Padayachee et al, 2011

Slide30

Caution! continuedRCTs were with age 2-16yrs, using non-imaging

TCD

– Imaging and non-imaging TCD correlate well

BUT

Results (actual cerebral flow velocity figures) are

NOT interchangeable

– no known formula to interconvert yet

Padayachee et al, 2011

Slide31

APPEALSEEK TO GET TCD MACHINES & EXPERTISEPOLITICAL WILL

FUNDING

2. SEEK ALTERNATIVE WAYS

Slide32

Thank you for listening