Shunt lesions

Shunt Lesions: Objectives

• Identify types of shunts
• Identify clinical features
• Diagnosis of shunts (including echo features)
• Qualification and management of shunts
• Who, when and how to treat

What is a shunt?

Right-to-Left shunts

• Blood from systemic arterial circulation mixes with venous blood

Where is the shunt

Laflamme, D., 2018. Cardiology: A Practical Handbook. CRC Press.

Calculating the shunt fraction

Laflamme, D., 2018. Cardiology: A Practical Handbook. CRC Press.

Is the shunt important?

Atrial Septal Defect

ACCSAP, Simple shunts, R. Krasuski 

Types of atrial septal defects

Silvestry, et al 2015. Journal of the American Society of Echocardiography, 28(8), pp.910-958.

ASD

• 15% of congenital abnormalities
• Ostium Secundum is 75% of all ASD abnormalities
• 10% of patients have >1 defect in the atrial septum
• 1/3 of patients have associated defects
  • eg: partial anomalous pulmonary venous drainage, coarctation of the aorta, subaortic stenosis, VSD, pulmonary stenosis

ASD: When to suspect

• Systolic murmur at LSB with fixed S2 split,
• Unexplained RV overload
• Atrial arrhythmia
• Pulmonary HTN

ASD: Clinical features

• Adult patients often present ~40 yo
• Symptoms: fatigue, palpitations, breathlessness
• Physical: fixed split-second heart sound, pulmonic flow murmur
  • +/- signs of pulmonary hypertension
  • +/- signs of Eisenmenger syndrome
• ECG: RBB, R-axis deviation, abnormal p-wave axis
• CXR: Prominent PA, RA, RV, pulmonary plethora

ACCSAP, Simple shunts, R. Krasuski 

Secundum ASD

• Normal or slightly elevated JVP
• RV heave
• Ejection systolic murmur PA
• Fixed split 2nd heart sound
• Tricuspid diastolic flow rumble

Associated findings: Secundum ASD

ECG: Typical RBB

Notched R-waves in inferior leads: "Crochetage"

Incomplete RBB in V1

Associated findings: Secundum ASD

Prominant PA

Pulmonary plethora

Assessing ASD

2018 AHA/ACC ACHD Guideline

ASD: Role of echo 

Journal of the American Society of Echocardiography Volume 28 Number 8

Journal of the American Society of Echocardiography (2015) Volume 28 Number 8

Journal of the American Society of Echocardiography (2015) Volume 28 Number 8

Journal of the American Society of Echocardiography (2015) Volume 28 Number 8

ASD: Cardiac imaging

• CT or MR cross-sectional imaging best for viewing pulmonary venous connections 
  • Especially: innominate vein or vertical vein
• CT and CMR can provide a shunt estimate

ASD: Estimation of Qp:Qs

• Can be estimated by CMR
• Limited reliability by TTE or TEE
• Cardiac cath- direct measurement

ASD: Role of cardiac catheterization

• Performed at the time of closure
• Diagnostic catheterization IF necessary to determine detailed hemodynamics (e.g. in the case of discrepant non-invasive imaging)

Calculation of Qp:Qs 

- indications for cath

1. Inconclusive left-to-right shunt severity by noninvasive means
2. Significant pHTN is suspected
   • PASP >50% systemic SAP or PVR > 1/3 of SVR and no cyanosis at rest or during exercise
3. Assess  LV diastolic function
4. Device close of secundum ASD
5. In older adults: Rule out left atrial hypertension secondary to diastolic dysfunction
   • Could have a similar presentation to ASD but have poor outcomes after ASD closure

Shunt run by cath

© 2021 UpToDate, Inc.

Note American values - in Canada no need to divide by 10

ASD: Should all be closed?

• In patients with normal functional capacity: closure benefits are unclear
• Patients who do not undergo closure have worse long-term outcomes:
  • Atrial arrhythmias 
  • Reduced functional capacity
  • Greater instances and degree of PAH

ASD: Who should have closure

• Patients with reduced functional capacity caused by important Secundum ASD
  • moderate-large left-to-right shunt
  • evidence of right heart volume overload
  • in the absence of PAH
• History of paradoxical embolism

ASD: Who to close

2018 AHA/ACC ACHD Guideline

ASD - Therapy

2018 AHA/ACC ACHD Guideline

ASD: Who to close

2020 ESC ACHD Guideline

Journal of the American Society of Echocardiography (2015) Volume 28 Number 8

Indications and contraindications for percutaneous  ASD and PFO closure

Journal of the American Society of Echocardiography (2015) Volume 28 Number 8

ASD Case

• 29 yo F with lifelong palpitations and new shortness of breath on exertion - specifically with stairs and with vigorous activity
• Physical exam: RV heave, S1, S2 split, soft murmur over left sternal border. No signs of heart failure

ASD Case

ASD Case

ASD Case

ASD Case

Hemodynamic data

(mmHg)

Oxygen saturations (%)

Right atrium 2

Right ventricle 28/3

Pulmonary artery 26/6, mean 14

Pulmonary wedge mean 4

Left atrium 4

Blood pressure (via cuff) 111/67

SVC 68.7

RA 84.7

IVC 73.4

Mixed venous 69.5

Left atrium 94.6

Pulmonary vein 93.8

Systemic 96

RV 86.9

Pulmonary artery 86.6

Hemoglobin 141 g/L 

Pulmonary vascular resistance 0.6 units.

Hemodynamic data (mmHg)

Oxygen saturation
(%)

Right atrium 2

Right ventricle 28/3

Pulmonary artery 26/6, mean 14

Pulmonary wedge mean 4

Left atrium 4

Blood pressure (via cuff) 111/67

SVC 68.7

RA 84.7

IVC 73.4

Mixed venous 69.5

Left atrium 94.6

Pulmonary vein 93.8

Systemic 96

RV 86.9%

Pulmonary artery 86.6%

Hemoglobin 141 g/L 

Pulmonary vascular resistance 0.6 units.

ASD Case

Underwent minimally invasive secundum atrial septal defect repair (4 x 3 cm autologous pericardial patch)

Ventricular Septal Defect

VSD

• The most common congenital defect in children
• The second most common congenital defect in adults
• Most common is perimembranous (80%) of cases
• Often isolated lesions, but can be in concert with other lesions or complexes (e.g. transposition of the great vessels, tetralogy of Fallot)

VSD: an acquired lesion

• Post MI
• Post TAVI
• Post septal myectomy
• Erosion of a strut of a bioprosthetic mitral valve
• Takuotsubo cardiomyopathy
• Trauma

ACCSAP, Simple shunts, R. Krasuski 

VSD: Clinical features

• Defect size is inversely proportional to sound and severity
• Large defect (>75% of aortic annulus diameter): Eisenmenger- syndrome has no sound
  • Equalization of pressure across the RV and LV
• Moderate-sized (measure 25-75% of aortic annulus diameter): mitral diastolic flow rumble
• • Mild to moderate volume overload of pulmonary arteries, left atrium and LV
• Small restrictive defect (Qp:Qs <1.5:1): loud holosystolic along the left sternal border
  • No LV volume overload or pulmonary hypertension

VSD: Prognosis

• Moderate - Large VSD: risk of progressive pulmonary vascular disease
  • Further risk of pulmonary hypertension, shunt reversal and cyanosis
  • HF
  • Other: Arrhythmias, endocarditis, double-chambered right ventricle, thromboembolism
• Small VSD: Good prognosis, risk of endocarditis, aortic regurgiation, double chambered right ventricle

VSD investigations

• ECG - if large with pulmonary hypertension - isolated RV or biventricular hypertrophy
• CXR - if large left-to-right shunt then LA, LV enlargement and/or pulmonary edema can be noted

VSD: Echocardiographic evaluation

• Identify the location of the defect on the septum
• Establishing the number of defects
• Identifying associated features
• Assessment of size and hemodynamic significance of the defect
• Guidance treatment: interventional or surgical

Membranous VSD: Echocardiographic evaluation

• The defect lies in the membranous septum just apical to the aortic valve and below the tricuspid valve's septal leaflet
• Parasternal long axis: seen below the aortic valve
• The orthogonal short axis of LVOT: beneath the tricuspid valve septal leaflet
• Subcostal: coronal and sagittal views

Muscular VSD: Echocardiographic evaluation

• Often multiple defects, especially post MI
• The use of colour flow is helpful across the septum
• The septum should be sweeped through in each view with colour doppler
• As the RV pressure increases, the VSD will become less apparent

Supracristal VSD: Echocardiographic evaluation

• Located caudal to the pulmonary valve and above the crista supraventricular
• Parasternal short axis: beneath the pulmonary valve
• Parasternal and subcostal long axis and apical views: Aortic valve right coronary cusp might prolapse into the VSD

Inlet VSD: Echocardiographic evaluation

• Located at the crux of the heart, posterior and inferior to membranous and outlet defects
• Apical and subcostal views are the best to view these defects

Malalignment VSD: Echocardiographic evaluation

• This occurs when there is malalignment defects between the atrial and ventricular septa or individual parts of the septum

VSD: Echocardiographic evaluation of hemodynamics

• Measurement of RV and PA pressures are more useful than Qp/Qs 
• Significant left-to-right shunting: LA and LV cavity dialate
  • Increased transpulmonary and transmitral velocity by doppler

VSD: Echocardiographic evaluation of hemodynamics

• Timing of shunt: 
  • Normal: Left-to-right in mid and late diastole and throughout systole
  • With increased pulmonary vascular disease/hypertension: Right-to-left in early and mid-diastole and late systole

VSD: Management

• VSD from infancy often close on their own
• They are often a part of a complex, e.g. transposition of the great arteries, tetralogy of Fallot

2018 AHA/ACC ACHD Guideline

2018 AHA/ACC ACHD Guideline

2018 AHA/ACC ACHD Guideline

Stage A: NYHA FC I, no complications
Stage B: NYHA FC II, mild complications
Stage C: NYHA FC III, moderate complications
Stage D: NYHA IV, severe complications
 

2018 AHA/ACC ACHD Guideline

VSD Case

• 28yo M referred to cardiology for chest pain and fatigue associated with fevers. Found to have spontaneous type I Brugada
• Physical exam: S1S2, no RV lift or apical displacement. No signs of volume overload.

VSD Case

VSD Case

VSD Case

VSD Case

• Small restrictive VSD
• The patient will be followed long term

Patent Ductus Arteriosus

PDA

PDA

• Associated with maternal rubella
• More common in women (3F:1M)

Clinical features:

• Brisk upstroke pulse
• Dynamic LV
• Continuous "machinery murmur" best heard under the left clavicle

2018 AHA/ACC ACHD Guideline

PDA: Echocardiogram

• Parasternal Long Axis: PDA at the pulmonary end
• Parasternal Short Axis: Views of the main pulmonary artery and aorta
• Apical 4 chamber: Assess for evidence of left atrial, LV dilation
• Subcostal: PDA may cause runoff in the abdominal aorta - can be seen as flow reversal in diastole
• Suprasternal notch: Presence and directionality of shunting across the PDA between the aortic arch and main pulmonary artery

2018 AHA/ACC ACHD Guideline

2018 AHA/ACC ACHD Guideline

Stage A: NYHA FC I, no complications
Stage B: NYHA FC II, mild complications
Stage C: NYHA FC III, moderate complications
Stage D: NYHA IV, severe complications
 

PDA Case

• 32 yo F with history of syncope at 18 yo investigated with echo found to have a PDA. She has occasional palpitations
• Physical exam: S1S2, soft systolic ejection murmur over the left sternal border, no continuous murmur, no RV lift

PDA Case: Echocardiogram

• Parasternal Short Axis: Views of the main pulmonary artery and aorta

PDA Case: Echocardiogram

• Apical 4 chamber: Assess for evidence of left atrial, LV dilation

PDA Case: Echocardiogram

• Suprasternal notch: Presence and directionality of shunting across the PDA between the aortic arch and main pulmonary artery

PDA Case: Conclusion

The echocardiogram suggested a shunt ratio 1.3:1, no evidence of left-sided dilation or dysfunction.

She continues to be followed