Ventricular septal defect and patent ductus arteriosus

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

VSDs vary by site and haemodynamic effect. Perimembranous defects can distort the aortic valve; muscular defects may be multiple. Adult intervention is uncommon and needs an ACHD team because anatomy, pulmonary resistance and associated lesions determine risk.

A PDA joins the descending aorta to the pulmonary artery. Persistent pulmonary overcirculation can dilate the left heart; advanced pulmonary vascular disease can reverse ductal flow and cause differential cyanosis.

Key points

A small restrictive VSD can produce a loud pansystolic murmur despite a small shunt.
A large VSD causes left-heart volume loading and, if uncorrected, pulmonary vascular disease and shunt reversal.
PDA classically causes a continuous left infraclavicular murmur, bounding pulses and wide pulse pressure when the shunt is substantial.
TTE defines most lesions; CMR or CT quantifies anatomy and flow when echo is incomplete.
Consider closure for significant left-to-right shunt with left-ventricular volume overload when pulmonary vascular resistance is acceptable.
VSD closure may also be considered for progressive aortic regurgitation from cusp prolapse or recurrent endocarditis.
Do not close a VSD or PDA in established Eisenmenger syndrome or irreversible severe pulmonary vascular disease.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Congenital septal malformation

Incomplete formation or alignment of the interventricular septum leaves a perimembranous, muscular or outlet communication. Location influences spontaneous closure, valve distortion and procedural planning.

Persistent arterial duct

Failure of the fetal connection between the descending aorta and pulmonary artery to close after birth leaves a continuous systemic-to-pulmonary communication.

Residual or associated congenital disease

A defect may persist after earlier surgery or occur with other congenital lesions. Operative history and current anatomy are therefore essential before attributing adult symptoms to one shunt.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Postnatal pressure gradients
After pulmonary vascular resistance falls, a VSD usually carries oxygenated blood from the left to the right ventricle, mainly during systole. A PDA carries blood from the aorta to the pulmonary artery during systole and diastole while aortic pressure remains higher.
2
Pulmonary overcirculation
Excess pulmonary flow returns to the left atrium and ventricle, causing volume loading and dilatation when the communication is haemodynamically important.
3
Defect-dependent flow patterns
A small restrictive VSD maintains a large pressure gradient and loud high-velocity systolic jet, whereas a large non-restrictive VSD may sound quieter as ventricular pressures equalise. A PDA instead produces continuous flow and, when the shunt is substantial, bounding pulses and a wide pulse pressure.
4
Pulmonary vascular remodelling
In a large unrepaired VSD or PDA, persistent high pulmonary flow and pressure can cause pulmonary arteriolar remodelling, raising pulmonary vascular resistance and reducing the original left-to-right gradient.
5
Shunt reversal
When pulmonary vascular resistance becomes sufficiently high, a VSD can reverse and cause central cyanosis. Reversed PDA flow enters the descending aorta distal to the left subclavian artery, so lower-limb cyanosis may exceed upper-limb cyanosis.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Restrictive VSD

Harsh pansystolic murmur at the lower left sternal edge, often with a palpable thrill; symptoms may be absent.

Large shunt

Exertional dyspnoea, recurrent respiratory symptoms, displaced apex and signs of left-heart volume overload suggest haemodynamic significance.

PDA physiology

Continuous machinery-like murmur below the left clavicle with bounding pulse and wide pulse pressure; the murmur may disappear after shunt reversal.

Aortic cusp prolapse

A new early diastolic murmur in a perimembranous or outlet VSD suggests developing aortic regurgitation.

Eisenmenger conversionRed flag

Cyanosis, clubbing, erythrocytosis, haemoptysis or syncope signals advanced pulmonary vascular disease and makes closure hazardous.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Transthoracic echocardiographyFirst step
Why
Define defect/duct, direction and velocity of flow, chamber size, valves and estimated pulmonary pressure.
Interpretation and limitations
A high-velocity VSD jet suggests restriction; low velocity does not reassure if pulmonary pressure is high.
02
12-lead ECG
Why
Identify chamber hypertrophy, conduction disease or arrhythmia.
Interpretation and limitations
Findings range from normal in small lesions to biventricular hypertrophy with a large shunt or PH.
03
CMR or cardiac CT
Why
Quantify Qp:Qs, ventricular volumes and anatomy when echo is limited.
Interpretation and limitations
CT is particularly useful for ductal calcification and procedural anatomy; CMR avoids ionising radiation.
04
Oxygen saturation and FBC/iron studies
Why
Detect cyanosis, secondary erythrocytosis and iron deficiency.
Interpretation and limitations
In PDA-related Eisenmenger physiology, lower-limb saturation may be lower than right-arm saturation.
05
Right-heart catheterisation
Why
Measure pulmonary haemodynamics and operability when PH is suspected.
Interpretation and limitations
Closure decisions require specialist interpretation of pulmonary vascular resistance and shunt response, not Doppler pressure alone.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Mitral regurgitation

Both can cause a pansystolic murmur, but mitral regurgitation is maximal at the apex and often radiates to the axilla rather than producing a lower-sternal thrill.

Tricuspid regurgitation

A lower-sternal pansystolic murmur that strengthens on inspiration, with prominent jugular v waves or a pulsatile liver, favours tricuspid regurgitation over VSD.

Venous hum

A benign continuous cervical murmur changes with posture or gentle venous compression. A PDA murmur persists beneath the left clavicle and may accompany bounding pulses.

Other continuous vascular shunt

An arteriovenous fistula or another aortopulmonary communication can generate continuous flow. Cross-sectional or Doppler imaging demonstrates the connection rather than relying on auscultation alone.

Primary pulmonary hypertension

Pulmonary hypertension without a congenital communication lacks the earlier left-to-right volume-load pattern. Congenital imaging, clinical history and invasive haemodynamics help determine whether a shunt caused the vascular disease.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01FirstNew or residual VSD/PDAFirst stepCharacteristic murmur, unexplained chamber dilatation, cyanosis or known childhood lesion.

1Obtain prior operative/catheter records and perform examination including upper- and lower-limb saturation.
2Use expert TTE to define lesion, shunt, ventricular effects, valves and pulmonary pressure.
3Refer adults with more than a trivial lesion, symptoms, aortic regurgitation or suspected PH to an ACHD service.
4Use CMR/CT and catheterisation when anatomy or operability is uncertain.

02NextClosure assessmentLeft-ventricular volume overload, significant shunt, progressive aortic regurgitation or recurrent endocarditis.

1Confirm that pulmonary vascular resistance permits safe closure and identify associated lesions.
2Select device or surgery in an ACHD multidisciplinary team; perimembranous VSD anatomy carries conduction and valve considerations.
3Treat active endocarditis or decompensation before elective intervention.
4After closure, check residual shunt, valve function, ventricular response and procedure-related conduction disease.

03EscalationSuspected Eisenmenger physiologyEscalationCyanosis, clubbing, haemoptysis, syncope or severe pulmonary hypertension.

1Do not proceed to closure; assess urgently in a combined ACHD-pulmonary-hypertension service.
2DefinitiveCheck saturation, FBC, iron status, renal/liver function, echo and definitive haemodynamics when safe.
3Avoid dehydration, routine venesection and unplanned anaesthesia; manage pregnancy risk explicitly.
4EscalationStart targeted PAH therapy only through the specialist service and escalate haemoptysis or decompensation emergently.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Left-heart volume overload

A substantial left-to-right shunt chronically enlarges the left atrium and ventricle, eventually causing exertional breathlessness, reduced ventricular function and overt heart failure.

Pulmonary hypertension and Eisenmenger syndrome

Irreversible pulmonary vascular remodelling can raise pulmonary arterial pressure and resistance enough to reverse the shunt, producing cyanosis. Routine closure is then dangerous because it can precipitate right-heart failure.

Aortic cusp prolapse and regurgitation

A high-velocity jet through a perimembranous or outlet VSD can draw an adjacent aortic cusp into the defect, progressively impairing leaflet coaptation.

Infective endocarditis or endarteritis

Turbulent shunt jets can damage endocardial or ductal surfaces and support infection. Valve involvement, embolisation or abscess formation may then complicate the congenital lesion.

Cyanotic vascular complications

Right-to-left flow permits paradoxical embolism, while chronic hypoxaemia causes erythrocytosis and haemostatic disturbance. Haemoptysis, stroke or other embolic events may result.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Track symptoms, functional capacity, oxygen saturation and signs of heart failure or pulmonary hypertension.
Use serial echo to assess residual shunt, LV size/function, pulmonary pressure and aortic or pulmonary valve regurgitation.
Obtain periodic ECG and rhythm monitoring when palpitations, syncope or post-procedure conduction risk is present.
Maintain dental health and investigate fever promptly; NICE does not recommend routine antibiotic prophylaxis for dental procedures solely because of these lesions.
Provide pre-pregnancy ACHD assessment for any residual shunt, pulmonary hypertension, ventricular dysfunction or aortopathy.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Loud can be small

A restrictive VSD produces a high-velocity turbulent jet and may be louder than a large non-restrictive defect.

Murmur loss can be ominous

As pulmonary vascular resistance rises, the pressure gradient and classic murmur may diminish while disease worsens.

Differential cyanosis

With reversed PDA flow entering distal to the left subclavian artery, toes may be more cyanosed than fingers.

Aortic valve surveillance

Perimembranous and outlet VSDs can draw an aortic cusp into the defect, causing progressive regurgitation.

Closure is physiology-led

A visible communication is not itself an indication; ventricular volume load and pulmonary vascular resistance determine benefit and safety.

11Common pitfallsFrequent interpretation and management errors.

01
Equating a loud VSD murmur with a large defect.
02
Reassuring after a murmur becomes quieter without reassessing pulmonary pressure.
03
Closing a shunt before invasive haemodynamic assessment when significant PH is suspected.
04
Missing aortic regurgitation in a perimembranous or outlet VSD.
05
Giving routine dental antibiotic prophylaxis contrary to NICE CG64.