assessment of shunt by cardiac catheterization

MSN Pavan Kumar,DM,NIMS,HYDERABD

Assessment of shunt by cardiac catheterization

Our concepts of heart disease are based on the enormous reservoir of physiologic and anatomic knowledge derived from the past 70 years' of experience in the cardiac catheterization laboratory.

As Andre Cournand remarked in his Nobel lecture of December 11, 1956, the cardiac catheter was the key in the lock.

By turning this key, Cournand and his colleagues led us into a new era in the understanding of normal and disordered cardiac function in humans

Shunt by cardiac catheterization

In 1930, Klein reported 11 RT heart catheterizations, including passage to the RV and measurement of cardiac output using Fick's principle.

In 1932, Padillo and coworkers reported right heart catheterization and measurement of cardiac output in two subjects

In 1947, Dexter reported his studies on congenital heart disease

The biggest change in the last 25 years has been the return to the therapeutic potential of the cardiac catheter.



Disease Present diagnostic catheterization indication

ASD , VSD , PDA

For pul. resistance and reversibility Of pulmonary HTN

Complex pulmonary atresia

Detailed characterization of lung segmental pulmonary vascular supply when noninvasive imaging methods incompletely define pulmonary artery anatomy

PA with intact IVS

Determination of coronary circulation

Supravalvar AS

useful to define relationship to CA origins

TOF Anatomy when CAs, VSDs, Ao-PA collaterals cannot be sufficiently imaged otherwise

Single ventricle

Hemodynamics/PVR

1. L – R shunt

2. R – L shunt



1. Pulmonary artery [PA] blood oxygen saturation is >80%, the possibility of a left-to-right intracardiac shunt should be considered .

When to suspect cardiac L – R shunt ?

Plan of management by catheterisation:

1. Diagnosis2. Quantification of shunt3. Hemodynamic load

1. Oximetry run2. Flow ratio3. Indicator dye dilution

technique4. Angiography 5. Pressure mearement


Left-to-right Intracardiac Shunts

In the oximetry run the oxygen content or % saturation is measured in PA,RV,RA,VC.

A left-to-right shunt may be detected and localized if a significant step-up in blood oxygen saturation or content is found in one of the right heart chambers

A significant step-up is defined as 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.

1. Left-to-right Intracardiac Shunts - Oximetry run


Various methods used for oximetry run are1. Oxygen content 2. Oxygen saturation

Spectrophotometry Oxygen dissociation curve

Oxygen content = O2 bound to Hb + dissolved O2Dissolved O2 = 3.26 * PaO2 / 100.Oxygen saturation = O2 bound to Hb / O2

capacity * 100Oxygen capacity = Hb * 13.6



Oxygen content The technique of the oximetry run is based on

the pioneering studies of Dexter and his associates in 1947

Oxygen content was measured by Van Slyke technique , and other manometric studies

Proposed step up at atrial , ventricular , pulmonary artery level are 2%, 1%, 0.5%.

Disadvantages of oxygen content technique15 – 30 min for obtaining a reading Technically difficult to performDependency on Hb content



Oxygen content Manometric to spectrophotometric methodSpectrophotometric is technically easy and results are

with 1 minOxygen content is calculated by saturation by

= O2 sat. * Hb % * 1.36When oxygen content is derived in this manner, rather

than by direct oximetric technique, the value is no more accurate (presence of carboxyhemoglobin or hemoglobin variants with O2 capacity other than 1.36).



O2 content Vs O2 saturationAntman EM. Blood oxygen measurements in the assessment

of intracardiac left to right shunts: a critical appraisal of methodology. Am J Cardiol 1980

Antman and coworkers – normal variation of both oxygen content and oxygen saturation of blood in the right heart chambers

Pts. without intracardiac shunts who were undergoing diagnostic cath.

Oxygen content and Oxygen saturation was calculatedFinally it was concluded that O2 sat. and O2 content

correlate well and also proposed that systemic blood flow and mixing of blood both determine step up of O2 levels



Oxygen saturation :O2 is determined by

1. O2 dissociation curve2. Spectrophotometry



O2 saturation – O2 dissociation curveMethod of saturation calculation Major disadvantage of dissociation curve is its

dependency on other factors



O2 saturation by spectrophotometry :Based on Beers law Advantages : quick ,accurate, precise , subject to

few errors , less dependency on Hb% .Disadvantages :

Inaccurate if large amounts of carboxy hemoglobin is present

Indocyanin green interfere with light source of spectrphotometry

Elevated bilirubin effect absorbtion of light



O2 saturation by spectrophotometry :Disadvantages :

1% error at 95% O2 saturation2.5% error at 70% O2 saturationMore accurate at 40-50%Low values O2 saturation is not at all reliable

if necessary saturations below 50% can be determined by blood gas method



O2 saturation spectrophotometry is presently best method for oximetry

Procedure of oximetry run2-mL sample from each of the following locations.

1. Left and/or right pulmonary artery & Main pulmonary artery

2. Right ventricle, outflow tract, mid & tricuspid valve .3. Right atrium, low or near tricuspid valve , mid & high .4. Superior vena cava, low (near junction with right atrium).5. Superior vena cava, high (near junction with innominate

vein).6. Inferior vena cava, high (just at or below diaphragm).7. Inferior vena cava, low (at L4-L5).8. Left ventricle.9. Aorta (distal to insertion of ductus).



Procedure of oximetry runIn performing the oximetry run, an end-hole catheter

(e.g., Swan-Ganz balloon flotation catheter) or one with side holes close to its tip (e.g., a Goodale-Lubin catheter) can be used

The entire procedure should take less than 7 minutes.If a sample cannot be obtained from a specific site

because of ventricular premature beats, that site should be skipped until the rest of the run has been completed.



site Average Range

SVC 74% 67-83%

IVC 78% 65-87%

RA 75% 65-87%

RV 75% 67-84%

PA 75% 67-84%

LA 95% 92-98%

LV 95% 92-98%

FA 95% 92-98%



• IVC variation

• RA variation

• SVC and IVC

difference

Oxygen saturation abnormalities :Right heart saturation

1. Elevated PA saturation – high cardiac output , L to R shunt

2. Low PA saturation – low cardiac out put , low systemic arterial saturation , increased oxygen extraction .

Left heart saturation 1. Elevated FA saturation – Pt.receiving O22. Low FA saturation – lung disease , pulmonary

edema , R to L shunt



Limitations of Oximetry Method1.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

Limitations of Oximetry Method2.Antman and coworkers ,

oxygen saturation influenced by the magnitude of systemic blood flow. High levels of systemic flow

tend to equalize the arterial and venous and low levels increase difference.



Limitations of Oximetry Method3.Antman and colleagues , the influence of blood hemoglobin

concentration may be important when blood O2 content (rather than O2 saturation) is used to detect a shunt



Limitations of Oximetry Method4.Lacks sensitivity in detecting intracardiac shunts ,

Small shunts, however, are not consistently detected by this technique.

5.Variations in pulmonary venous saturation Lower portion of lung has lower O2 saturation Children CHD – atelectasis – compress the bronchus

– desaturation of corresponding bronchus6.d/t the 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 )



7. Various CHD where it is virtually impossible to calculate systemic and pulmonary blood flow

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



Indicator dye dilution technique is used to identify left to right shunt

Various dyes that are used are1. Indocyanine green dye2. Inhaled hydrogen , dissolved hydrogen in

saline3. Freon test4. L – krypton – 85 5. Nitrous oxide test6. T - 1824

Left-to-right Intracardiac Shunts - Indicator dye dilution technique


For detection of left to right shunt dye is injected in to proximal chamber and sample is taken from distal chamber by densitometry and density of dye displayed over time

Usually it is injected in to PA and identified in aortaPresence of L – R shunt is detected by early recirculation of

dye on the down slope of the curveIn addition to identification curve can also predict the

severity of shunt





In adults indocyanine green dye dilution curve provides estimate of shunt magnitude

Shunt magnitude is smaller than oxymetric method

But flow ratio (Qp/Qs) are equal in both

Advantages :This technique can detect left-to-right shunts too small

to be detected by the oxygen step-up method .Thus if there is no evidence of a left-to-right shunt by

this method, there is no need to perform an oximetry run.

The studies of Castillo and coworkers suggest that left-to-right shunts as small as 25% of the systemic output can be detected by standard pulmonary artery to systemic artery dye curves



Disadvantages :Although a simple pulmonary to systemic artery

indocyanine green dye curve may detect the presence of a shunt, it does not localize it

Presence of aortic and mitral regurgitation may distort the slope and give rise to false positive results



Selective angiography is effective in visualizing and localizing the site of left-to-right shunts

Angiographic demonstration of anatomy has become a routine part of the preoperative evaluation of patients with congenital or acquired shunts and is useful in localizing the anatomic site of the shunt

Left-to-right Intracardiac Shunts - Angiocardiography




Lesion

View Angio site

ASD Steep LAO (60) cranial(15) PA angio - levophase

VSD LAXO(60-30) –Perimembranous and mid muscular 4CV(LAO40-40) – posterior muscular and inlet RAO(30) – Anterior muscular and outlet

LV angio

PDA Lateral , LAO(60) , RAO caudal Pulmonary or Aortic angio

AVSD 4CV(LAO40-40) Lv angio

LV – RA

4CV(LAO40-40) Lv angio



Angiograms in the LAXO in VSD



Angiograms in the lateral position in patent ductus arteriosus



Angiograms in the LAO position in RSOV to RA

Qualitative by oximetry and next Quantitative by flow ratio

Quantification is done by Qp , Qs , Qp/Qs , Effevtive blood flow, L-R shunt , R-L shunt .

Qp and Qs are amount of blood flowing through pulmonary and systemic vascular bed

Qef is quantity of mixed venous blood that carries desaturated blood from systemic capillaries to be oxygenated by lungs

L-R and R-L shunt are amount of blood that bypass systemic and pulmonary vascular bed .


Left-to-right Intracardiac Shunts - Flow ratio

Qp , Qs , Qeff are based on Ficks principle for calculation of cariac output

Cardiac output = VO2 / AVO2 difference



Points of importance while calculation:1. Oxygen consumption2. Calculation of saturations3. Oxygen content



Oxygen consumption: Oxygen consumption = oxygen inspired – oxygen

expiredMethods for OC are the Douglass bag , the

polarographic method and paramagnetic method





Oxygen consumption: Emperical formulas :

VO2 = 125 * BSAFor boys, VO2 = 138.1 - 11.49 In(age) + 0.378

(heart rate).For girls, VO2 = 138.1 - 17.04 In(age) + 0.378

(heart rate).

LaFarge C.G., Miettinen O.S. The estimation of oxygen consumption. Cardiovasc Res. 1970



Calculation of saturation :PAO2 and FAO2 are usually calculated by blood

samplesMVO2 and PVO2 calculations are most importantMVO2



MVO2 at atrium level1. At rest = 3SVC + IVC / 4

Flamm's formula weights blood returning from the superior vena cava more heavily than might be expected on the basis of relative flows in the superior and inferior cavae.

2. During bicycle ergometry = SVC + 2IVC / 33. Directly taking SVC saturation as MVO2



Calculation of saturation PVO2NOT usually entered LA vs PVO2



Assumed valve if not calculated

FA saturation

≥ 95%

< 95%

Take FA sat.

1. d/t R – L shunt assume 98% as PVO2

2. Not d/t R – L shunt take FA saturation

Oxygen content :Oxygen in blood is present bound to Hb and dissolved

contentOxygen content = O2 with Hb + O2 dissolvedO2 with Hb = 13.6 * Hb in gm/dl * % saturationO2 dissolved = 3.26mlO2/L at oxygen tension of 100

mm hgImportance of dissolved oxygen – while breathing

room air and breathing oxygenEg: oxygen tension is 50 mm hg – O2 dissolved is 1.83 oxygen tension is 500 mm hg – O2dissolved is

16.3



Additional information that can be obtained are Bidirectional shunt Double left to right shunt



Bidirectional shunt : estimation and quantification of each L-R and R-L shunts can be done by oxymetric help in catheterisation



L – R = Qp – QeffR – L = Qs – QeffNET SUNT = (L-R) – (R-L)

Double left to right shunt : Not only identification but also quantification double L-R shunt can be done by oxymetry

Method 1: S = F * A – B /C – A S = L – R shunt in to the chamberF = Blood flowing in to the chamberA = O2 sat. In chamber receiving shunted bloodB = O2 sat. in chamber proximal to the shuntC = O2 sat. in pulmonary vein



Double L – R shunt Method 2 :

1. Calculate L – R shunt(Qp – Qeff) by convention 2. Calculate L – R shunt of proximal chamber

assuming PAO2 to be saturation in that chamber

3. See the difference between step 1 and 2



PVR = PA – PCWP / QpSVR = AORTA – RA /QsPVRI = PA – PCWP / CARDIAC INDEX = (PA – PCWP / Qp) * BMIPVRI/SVRIReversibility testing when required

1. MAP > 40 mm hg2. PVRI > 8 wood units3. PVRI/SVRI > 0.5

Left-to-right Intracardiac Shunts - Hemodynamic overload


Any patient with cyanosis or arterial desaturation <95%


Suspesion Of Right to Left Intracardiac Shunts

Supine position of the patient - Alveolar hypoventilation ,

Excessive sedation from the premedicationCOPD or other pulmonary parenchymal diseasePulmonary congestion secondary to the cardiac

disease , L – R shuntAssume a more upright posture , take deep breaths ,

cough Administer 100% oxygen

Persisting hypoxia indicates L – R cardiac shunt


Detection Of Right to Left Intracardiac Shunts

Various methods available in cahteterisation for R – L 1. Indicator dye dilution technique and other

indicators2. Angiography 3. Oximetry run

Catheterisation aims in R – L shunts are

1. Detection 2. localisation 3. magnitude of shunt

Attempts to measure right-to-left shunts in patients with cyanotic heart disease date back at least to 1941

Prinzmetal , Benenson and Hitzig studied regarding R-L identification

1. Left-to-right Intracardiac Shunts - Indicators


Ether injected intravenously in patients

Normal subjects the ether is eliminated by the lungs and thus does not reach the systemic circulation

Patients with R – L shunt cause a prickly, burning sensation of the face

Prinzmetal then measured the time necessary for an intravenous injection of a dilute solution of saccharin to be tasted.

This time is equal to the transit time from a peripheral vein through the lungs, through the left heart, and then to the systemic circulation.

By increasing the concentration of the saccharin, he found that a second, much shorter appearance time occurred in patients with cyanotic heart disease because of the presence of a right-to-left shunt bypassing the pulmonary circulation.



He estimated the percent right-to-left shunt by the following formula:

where A is the smallest concentration of saccharin to be tasted by way of the long circuit and C is the smallest concentration of saccharin to be tasted by the short circuit.

But these methods are so indegenious and used now a days



Indicator dye dilution technique are used identify R – L shunt

Various indicators that are used are1. Indocyanine green dye2. Ascorbic acid3. Hydrogen 4. Krypton – 85

Dye is injected in the right of heart proximal to presumed shunt, and detected from systemic artery

Presence and quantification of right to left shunt can be done.


1. Left-to-right Intracardiac Shunts - Indicator dye dilution technique



Identification



Quantification

The site of right-to-left shunts may be localized if blood samples can be obtained from a PV , LA , LV , and Aorta

The PV blood of patients with arterial hypoxemia caused by an intracardiac right-to-left shunt is fully saturated with oxygen.

The site of a right-to-left shunt may be localized by noting which left heart chamber is the first to show desaturation .(STEP DOWN).

By calculation of Qeff quantification of total R – L can be determined by Qs – Qeff


2. Left-to-right Intracardiac Shunts - Oximetry

Disadvantages of oxymetry in R – L shunt:1.The main disadvantage of this technique is that a PV

and the LV must be entered. This is not as easy in adults as it is in infants, in whom the LA is entered routinely by way of the foramen ovale.

2.Quantification of desaturation that’s significant has not been adequately determined like L – R shunt.


2. Left-to-right Intracardiac Shunts - Oximetry

Angiography helps in assessing appropriate anatomy in patients with R – L shunt.


1. Left-to-right Intracardiac Shunts - Angio cardiography

Retrograde LV angiogram demonstrates a solitary

malaligned VSD

Infundibular narrowing & R-L shunt into aorta is seen in the RV angio in

RAO

Right & anterior AO connected to right-sided (anterior) morphologically RV and left & posterior pulmonary artery (PA) connected to left-sided (posterior) morphologically left ventricle





DORV with side-by-side great artery relationship and subaortic subpulmonic and doubly commited

VSD

Thank you

assessment of shunt by cardiac catheterization

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