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SHUNT QUANTIFICATION AND REVERSIBILITY Dr. Gopal Ch. Ghosh Cardiology unit-II
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Page 1: Shunt quantification and reversibility

SHUNT QUANTIFICATION

AND REVERSIBILITY

Dr. Gopal Ch. Ghosh

Cardiology unit-II

Page 2: Shunt quantification and reversibility

Definition

• Shunts are abnormal communications between

the systemic circulation and pulmonary

circulation.

1. Physiological

2. Pathological

3. Iatrogenic

Page 3: Shunt quantification and reversibility

Intracardiac shunt

• Diagnosis:

• Clinical evaluation of patient before

catheterisation

Page 4: Shunt quantification and reversibility

When to suspect a shunt?

(In CATH LAB )

• Unexplained arterial desaturation(Sao2<95%)

1. Excessive sedation

2. COPD

3. Pulmonary congestion/edema

• Unexpectedly high Oxygen content in pulmonary

artery (>80%)

• When data obtained in catheterisation laboratory

do not confirm the presence of suspected lesion

Page 5: Shunt quantification and reversibility

Oximetry run

• Pioneering studies of Dexter and his associates

in 1947(Technique)

• Oxygen content: measured by Van Slyke

technique (manometric technique)

• Volume% of oxygen: 1ml O2/100ml blood

• Present era: Oxygen saturation by

spectrophotometry

Page 6: Shunt quantification and reversibility
Page 7: Shunt quantification and reversibility

• Obtain a 2-ml sample from each of the following locations:1. Left and or right pulmonary artery2. Main pulmonary artery3. Right Ventricle, outflow tract4. Right ventricle, mid5. Right ventricle, tricuspid valve or apex6. Right atrium, low or near tricuspid valve7. Right atrium, mid8. Right atrium, high9. Superior vena cava, low (near junction with

right atrium)10. Superior vena cava, high (near junction with

innominate vein)11. Inferior vena cava, high (just at or below diaphragm)12. Inferior vena cava, low L4-L5)13. Left Ventricle

14. Aorta (distal to insertion of ductus)

Page 8: Shunt quantification and reversibility

Methods

• End hole catheters or side holes close to its tip

[Swan Ganz balloon flotation catheter, Goodale-

Lubin catheter]

• <7 minutes

• Withdraw fiberoptic catheter

Page 9: Shunt quantification and reversibility

Significant step up

• An increase in blood oxygen content or

saturation that exceeds the normal variability

that might be observed if multiple samples

were drawn from that cardiac chamber

Page 10: Shunt quantification and reversibility
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Guidelines for optimal utilisation

• Rapid collection of blood samples

• O2 saturation data preferable

• Comparison of mean values

• Exercise should be used in borderline cases

Antman EM et al. Am J Cardiol 1980

Page 12: Shunt quantification and reversibility

Advantages

1. Easy to perform

2. Results are available immediately

3. Site of the shunt detection

4. Magnitude of the shunt determination

James D. Boehrer et al. American Heart Journal

Volume 124, Issue 2, August 1992, Pages 448–455

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Limitations

• Small left to-right shunts: Not detectable

Page 14: Shunt quantification and reversibility

James D. Boehrer et al. American Heart Journal

Volume 124, Issue 2, August 1992, Pages 448–455

Page 15: Shunt quantification and reversibility

• Influence of blood hemoglobin concentration

may be important when blood O2 content

(rather than O2 saturation) is used to detect a

shunt

Page 16: Shunt quantification and reversibility

• A primary source of error may be the absence

of a steady state during the collection of blood

samples

Error source Problem solving

Prolonged because of

technical difficulties

Start from PCW-PA-RV-RA-VC

If the patient is agitated

(children)

Sedation

If arrhythmias occur during

the oximetry run

Leave the site and go to next site

Page 17: Shunt quantification and reversibility

• Presence of physiological shunt

– Thebesian veins and coronary veins entering LV

(R- L)

– Bronchial veins draining in to LA / PV (R- L)

– Bronchial artery to pulmonary artery (L – R )

Page 18: Shunt quantification and reversibility

• In a patient with a large L-R shunt caused by arterial

collaterals entering the distal pulmonary vascular bed,

it is impossible to obtain a blood sample distal to the

shunt

Page 19: Shunt quantification and reversibility

Calculation of pulmonary blood

flow(Qp) & systemic blood flow(Qs)

• If Sao2>95% then use Sao2 as Pvo2

• If Sao2<95% then use Pvo2 as 98% (look for

right to left shunt)

Page 20: Shunt quantification and reversibility

Mixed venous oxygen saturation

• Patients in resting state:

Mvo2 = 3 x SVC O2 + 1 x IVC O2 / 4

• Supine bicycle exercise:

Mvo2 = 1 x SVC O2 + 2 x IVC O2 / 3

Page 21: Shunt quantification and reversibility

Oxygen content

Page 22: Shunt quantification and reversibility

O2 Consumption

• Prediction from tables, nomograms, or

regression models is notoriously unreliable

• VO2 = 5.0×kg+19.8

• Direct measurement is preferable

LaFarge CG et al. Cardiovasc Res 1970

Page 23: Shunt quantification and reversibility

Effective blood flow

Page 24: Shunt quantification and reversibility

• Approximate left to right flow: Qp – Qeffective

• Approximate Right to left shunt: Qs - Qeffective

Page 25: Shunt quantification and reversibility

Other methods for shunt detection

• Indocyanine green dye curve

• Radionuclide technique

• Contrast angiography

• Echocardiographic methods

Page 26: Shunt quantification and reversibility

Indocyanine green dye curve

• Rarely used today

• Laboratories are not equipped

• Qualitative only

• Does not localise the shunt

• Can detect shunt < 25% of systemic flowCastillo et al. Am J Cardio 1966

Page 27: Shunt quantification and reversibility
Page 28: Shunt quantification and reversibility

Contrast angiography

• Visualisation & localisation of left to right

shunt

• Left ventriculogram

- Interventricular septum

- Sinuses of valsalva

- Ascending & descending aorta

• Left to right shunt except atrial septal defects

& anomalous pulmonary venous connection

Page 29: Shunt quantification and reversibility

Pulmonary hypertension

• Mean pulmonary artery pressure > 25mm hg

(at rest) or 30mm hg after exercise

• In infants & neonates: may not be applicable

Page 30: Shunt quantification and reversibility

WHO 2003

Page 31: Shunt quantification and reversibility

Types

• Hyperkinetic pulmonary hypertension:

minimal pathological changes

• Pulmonary vascular occlusive disease:

irreversible changes

Page 32: Shunt quantification and reversibility

Lesion specific pulmonary

hypertension

• Large VSD or PDA: 1-2 years of age

• Cyanotic congenital heart disease with

increased blood flow: 6 months

A saxena et al. PVRI review. 2009

Page 33: Shunt quantification and reversibility

ASD with pulmonary hypertension

• Behaves differently from post tricuspid shunt

• Persistence of the fetal pulmonary vascular

pattern

• Thromboembolism in small pulmonary arteries

• “Musculoelastosis"

Cherian G et al. Am heart journal. 1983

Yamaki S et al. Chest. 1987

Page 34: Shunt quantification and reversibility

Determination of shunt

Page 35: Shunt quantification and reversibility

Electrocardiogram

• Post tricuspid shunts: Biventricular

hypertrophy with left ventricular volume

overload

• Significant left ventricular voltage with “q”

wave in lateral leads suggests operability

• Eisenmenger syndrome: right axis deviation

& right ventricular hypertrophy

Page 36: Shunt quantification and reversibility

Significant infant VSD with moderate sized defect and a large left to right shunt.

Page 37: Shunt quantification and reversibility

X-RAY CHEST

• Cardiomegaly, prominent pulmonary artery

segments (except in malposed vessels) &

increased pulmonary vasculature: Large left to

right shunt

Page 38: Shunt quantification and reversibility

Patient with large VSD

Page 39: Shunt quantification and reversibility

22 year old lady with large PDA

Page 40: Shunt quantification and reversibility

• A large heart in X-ray chest may indicate

operabilitry

• Pruning of pulmonary artery branches are

common to both hyperkinetic pulmonary

hypertension & pulmonary vascular occlusive

disease

Page 41: Shunt quantification and reversibility

Echocardiography

• Most important test & most often performed

Page 42: Shunt quantification and reversibility

Clinical assessment for operability

• In infants & young children: Operable

• Presence of flow murmur

• Cardiomegaly & increased pulmonary blood

flow in X-ray

• Biventricular hypertrophy & left ventricular

volume overload in ECG

Page 43: Shunt quantification and reversibility

Clinical assessment for operability

• Older child: Unoperable

• Cyanosis

• No shunt or flow murmur

• ECG showing RVH

• Heart size normal or minimaly enlarged in X-

ray chest

Page 44: Shunt quantification and reversibility

Clinical assessment for operability

• Cyanotic congenital heart disease:

• Arterial saturation >85% indicates operability

in infants < 1 year of age

Page 45: Shunt quantification and reversibility

Role of cardiac catheterisation

• Must be performed in all borderline cases for

decision making

• Simple shunt, age < 1 year: Non invasive

monitoring

• Infants with common arterial trunk, atrio-

ventricular septal defect, transposition with

VSD presenting after 1 year: Needs

catheterisation

Antonio Augusto Lopes et al. Cardiol Young

2009; 19: 431–435

Page 46: Shunt quantification and reversibility

Role of cardiac catheterisation

• Patients living at high altitude: necessary even

below the age of 3 to 6 months

• Functionally univentricular physiology who

are candidates for creation of the Fontan

circulation

Page 47: Shunt quantification and reversibility

Anaesthetic protocols

• Adequately ventilated during the entireprocedure: Paco2 normal or slightly decreased

• Sao2 should be at precatheterisation level

• Low volume Ketamine + Midazolam

• Ketamine + Propofol

• Midazolam + Ramifentanyl

Jobeir A et al. Pediatr Cardiol 2003

Kogan A et al. J Cardiothorac Vasc Anaesth 2003

Laird TH et al. Anaesth Analg 2002

Page 48: Shunt quantification and reversibility

Signs of operability

• Pulmonary vascular resistance index <6 Wood

units times metre squared

• Resistance ratio of less than 0.3

• PVRI: 6-9, needs reversibility testing

• Fontan circulation: PVRI<3 woods units times

metre squared Khambdkone S et al. Circulation 2003

Page 49: Shunt quantification and reversibility

Reversibility testing

• Oxygen(100%)

• Inhaled nitric oxide

• Intravenous prostacyclin

• Intravenous isoprenaline

• Intravenous adenosine

Page 50: Shunt quantification and reversibility

Protocol

• Initial sample: breathing room air or 21-30%

oxygen inhalation for 10 minutes

• Repeat them after pure oxygen inhalation for

15 min

Page 51: Shunt quantification and reversibility

Signs of reversibility

• A decrease of around one-fifth in the index of

pulmonary vascular resistance

• A decrease of around one-fifth the ratio of

pulmonary to systemic vascular resistance

• A final pulmonary vascular resistance index of

less than 6 Wood units times metre squared

• A final ratio of resistance of less than 0.3

Antonio Augusto Lopes et al. Cardiol Young 2009

Page 52: Shunt quantification and reversibility

Cautions

• Elimination of the dissolved oxygen can

falsely increase pulmonary flow

Page 53: Shunt quantification and reversibility

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