Left-to-Right Shunt

Most common CHD in adults

Associated with some genetic syndromes, e.g. Noonan, trisomy 21

More likely in females than males.

1. Ostium secundum
   1. 70% of all ASD
   2. Often show right bundle branch block with right axis deviation on ECG
2. Ostium primum
   1. 15% of all ASD, associated with atrioventricular node abnormalities
   2. Often have right bundle branch block with left axis deviation on ECG
3. Sinus venous defect
   1. 5% of all ASD
   2. Associated with an anomaly in the insertion of the inferior or superior vena cava
4. Coronary sinus defect
   1. Less than 1% of all ASD
   2. Associated with a missing or partial wall between the left atrium and coronary sinus

Often symptomatic after 4th decade: palpitations, dizziness (an atrial arrhythmia), shortness of breath, dyspnoea, fatigue, reduced exercise tolerance

Most common:

1. Systolic Ejection Murmur – loudest at the left upper sternal border, radiates to the back. This is due to excess blood flow across the pulmonary valve.
2. Fixed second heart sound splitting – split second heart sound, even in expiration.

Uncommon:

1. Risk factors: maternal alcohol consumption, female
2. Mid-diastolic murmur: if moderate to large left-to-right shunt
3. Finger clubbing

ECG: typically normal in small ASD but tall P waves and large R waves in V1 (moderate to severe)

Chest X-ray: normal if small ASD, possible cardiomegaly (moderate to severe)

Qp:Qs <1.5 – observation, may resolve spontaneously

Qp:Qs ≥ 1.5 or enlargement of the right atrium – corrective surgical or transcatheter closure

Pulmonary Vascular Resistance >5

1. Pulmonary vasodilator
2. If PVR drops < 5 – corrective closure and prophylactic antibiotics
3. If PVR remains >5 – consider cardiopulmonary transplantation

If there is no evidence of pulmonary vascular obstructive disease, there is an excellent prognosis.

The older the age of the patient at the point of repair, the increased risk of adverse events.

Other symptoms can include palpitations, haemoptysis, syncope, progressive cyanosis and swelling.

Also, due to chronic hypoxaemia, the patient can develop symptoms related to polycythaemia. These include headache, dizziness, stroke and visual changes.

1. Right ventricular heave – forceful contracture against increased pulmonary pressures
2. Raised jugular venous pressure
3. Peripheral oedema
4. Loud Second Heart Sound – due to forceful pulmonary valve closure

Signs related to the underlying CHD

1. ASD: mid-systolic, crescendo-decrescendo murmur, loudest at the upper left sternal edge
2. VSD: pan-systolic murmur, loudest at the level of left lower sternal border
3. PDA: “machinery” murmur, continuous crescendo-decrescendo

Signs of right-to-left shunt and chronic hypoxaemia

1. Dyspnoea
2. Clubbing
3. Cyanosis
4. Plethoric complexion (secondary to polycythaemia)

ECG

Chest X-ray

Bloods, including full blood count and iron studies

Once Eisenmenger syndrome has developed, reversal of the high pulmonary arterial pressure is not possible, and a cardiopulmonary transplant is needed. This is not always possible and is associated with high mortality.

Supportive treatment options can include:

1. Vasodilators for pulmonary hypertension
2. Venesection for polycythaemia
3. Anticoagulation to reduce thrombus risk
4. Treatment of any resulting arrhythmias

The most common cause of death is stroke, haemoptysis, ventricular failure and pregnancy complications.

Management is required from a multidisciplinary team, including cardiologists.

Isolated VSD occurs in 3.5 per 1000 live births but often close spontaneously.

VSD can accompany other congenital defects, not just in isolation

Acquired VSD secondary to trauma or myocardial infarction is rare

Unusual for VSD to present in adults.

Congenital

• No known definitive cause
• High incidence in those with Down’s syndrome

Acquired

• Are rare causes
• Penetrating chest wall trauma
• 2-5 days after an acute myocardial infarction

Shortness of breath on exertion

Risk factors: Maternal alcohol use in pregnancy, Down’s syndrome, family history of CHD

Repeated pulmonary infections: in shunt reversal associated with large defects

• Loudest in the left parasternal region, the smaller the defect, the louder the murmur

Loud pulmonary component of the second heart sound

• Indicative of pulmonary hypertension

Chest x-ray – may be normal or show cardiomegaly.

ECG – dependent on the size of the VSD, not diagnostic but supportive. In medium VSD can show signs of left ventricular hypertrophy.

Prophylactic antibiotics should be considered in all VSDs to prevent endocarditis.

Congenital

Small VSD (Qp:Qs <1) – monitoring and observation, they may spontaneously close.

Medium/Large VSD (Qp:Qs ≥1.5)

• Asymptomatic
  • Surgical closure to prevent progression into heart failure
• Symptomatic
  • Preoperative medical treatment, e.g. diuretics, ACEi and digoxin
  • Followed by surgical closure
• Eisenmenger’s Syndrome
  • Supportive medical management, e.g. vasodilators
  • Cardiopulmonary transplant

Acquired

Surgical repair

Patients who have corrective closure require monitoring for the development of heart block or arrhythmia.

Potential complications include aortic regurgitation, heart block, arrhythmia and infective endocarditis.

The prognosis is dependent on the size of the VSD.

• Asymptomatic: 50% will spontaneously close, and 50% will remain asymptomatic.
• Moderate VSD: if untreated, it will progress to congestive cardiac failure. If treated with surgical closure, then progress is excellent.
• Large VSD: if untreated, will progress faster to Eisenmenger syndrome, with a poor prognosis.

2:1 female-to-male ratio

May be present with other congenital heart defects

It can present in some genetic syndromes, e.g. Noonan, Downs, DiGeorge

In the post-natal period, increased oxygen saturations and reduced circulating prostaglandin secondary to placental loss result in the closure of the ductus.

The pathology of PDA is due to the left-to-right shunting of blood from the aorta to the pulmonary artery.

An older child or adult can present with shortness of breath and exercise intolerance.

• Qp:Qs <1.5
• Often asymptomatic and due to incidental finding
• After the newborn period, a continuous flow murmur/machinery murmur/Gibson’s murmur is heard on auscultation.

Moderate PDA

• Qp:Qs 1.5-2.2
• Exercise intolerance
• A continuous murmur in the left infraclavicular area
• Wide systemic pulse pressure
• Displaced left ventricular apex (due to left ventricular volume overload)

Large PDA

• Qp:Qs >2.2
• Shunt reversal, resulting in cyanotic Eisenmenger syndrome
• In adults, short systolic ejection murmur on auscultation
• Cyanosis and clubbing

Chest X-ray – normal if PDA is small, slight cardiomegaly if moderate, left heart enlargement if large.

Ecg – normal if PDA is small, biventricular hypertrophy and left atrial anomaly if large.

Risk factors include atrial septal aneurysms and congenital heart defects.

A trans-oesophageal echo with contrast and colour Doppler is used when a definitive diagnosis is required.

Asymptomatic

1. Low risk for a thrombotic event and in a low-risk profession
   1. No history of TIA or CVA
   2. Treatment is education and monitoring
2. High risk for a thrombotic event and in a low-risk profession
   1. Presence of an atrial septal aneurysm and/or large PFO
   2. For some patients, education and monitoring is sufficient.
3. In some, anticoagulation with aspirin or clopidogrel is indicated.

Cryptogenic stroke or transient ischaemic attack

Patient selection based on a MDT approach involving neurology and cardiology

1. Suitable for percutaneous closure
   1. In patients aged 18-60, via percutaneous transcatheter PFO
   2. Also treated with antiplatelet therapy
2. Not suitable for percutaneous closure
   1. Medical management with anticoagulation, e.g. Warfarin, Aspirin or Clopidogrel
   2. Note there is a risk of major bleeding with this approach

High-risk professions, e.g. astronauts, pilots and deep-sea divers

1. Anticoagulation vs antiplatelet therapy
   1. Aspirin or Clopidogrel vs Warfarin
2. Education on how to avoid decompression sicknessPercutaneous closure is considered if suitable.

Prognosis is variable, dependent on the category of patient. In most, however, PFO is not correlated with a higher risk of death or stroke if medically treated. In those with CVA and/or TIA, the risk of a reoccurrence of CVA and/or TIA is 3x higher in PFO, and this increases to 6x higher in those with a concurrent atrial septal aneurysm.