• 40% have pulmonary arterial oxygen saturation greater than systemic, 40% have systemic arterial oxygen saturation greater than pulmonary and the rest have equal saturations is systemic and pulmonary arteries.
• With subpulmonary VSD, pulmonary oxygen saturation is always more than systemic.
• With subaortic VSD, in 60% cases systemic arterial oxygen saturation is greater than pulmonary while in 40% pulmonary arterial oxygen saturation is greater than systemic.
• With doubly committed VSD, pulmonary arterial oxygen saturation is more than systemic.
• If systemic arterial oxygen saturation is more pulmonary, the VSD cannot be subpulmonary.
• If pulmonary arterial saturation is more than systemic, VSD location cannot be predicted.
• RV has systemic pressure.
• If PS is present, PA pressure is reduced.
• If PS is mild, pulmonary vascular disease can occur.
• With restrictive VSD or intact ventricular septum, LV pressure is suprasystemic.
• With subaortic stenosis, RV pressure is suprasystemic.

  Clinical manifestations
  

• Four groups-
  • Like TOF- subaortic VSD + PS
  • Like TGA- subpulmonary VSD (with or without PS)
  • Like VSD- subaortic VSD without PS
  • Like Eisenmenger- subaortic VSD with pulmonary vascular obstructive disease
• Group 1- like TOF- subaortic VSD + PS
  • Cyanosis, squatting.
  • PS MSM, single S2.
• Group 2- like TGA- subpulmonary VSD (with or without PS)
  • Resemble TGA with VSD.
  • In early infancy, cyanosis with heart failure occurs.
  • Pulmonary plethora and frequent respiratory infections.
  • RV impulse, PSM at upper left sternal border and single loud S2.
• Group 3- like VSD- subaortic VSD without PS
  • Heart failure.
  • PSM of VSD.
  • Apical MDM and S3.
• Group 4- like Eisenmenger- subaortic VSD with pulmonary vascular obstructive disease
  • Older group 3 patients.
  • Cyanosis, decreased pulmonary blood flow, absent PSM, loud single S2.

• Intact ventricular septum
  • LV is hypoplastic.
  • Mitral valve is deformed.
  • ASD is present.
  • Only outlet for LV is via mitral valve and ASD.
• Double chambered right ventricle
• Tricuspid atresia- RV is hypoplastic
• DORV with dextrocardia and AV discordance
  • Subpulmonary VSD + severe PS (valvular and subvalvular)

   

  Associated cardiac anomalies
  

• Pulmonary stenosis
  • Commonest associated anomaly.
  • Present in 70% of patients with malposed great arteries.
• Subaortic stenosis
  • In 3%.
  • Mechanisms-
    • Hypertrophy of aortic conus
    • Shift of aortic conus due to pulmonary artery enlargement in subpulmonary VSD.
• Mitral valve abnormalities
  • As part of complete AV septal defects
  • Cleft AML with mild straddling. Usually does not produce mitral valve dysfunction.
• Trisomy 18.
• Left ventricular hypoplasia- usually mild.

   

  Conduction system
  

• AV bundle lies in the inferior wall of the VSD.

   

  Coronary anatomy
  

  • Normal- Usual pattern.
  • Abnormal and like TOF- LAD from RCA- in DORV with subaortic VSD and PS
  • Abnormal and like TGA- uncommonly seen in TBA.

• Types of DORV based on great artery relation and VSD location

  · Side by side relationship of great arteries

  o Subaortic VSD

  § Right lateral aorta with subaortic VSD accounts for nearly half of all DORV cases.

  § Both semilunar valves are in the same horizontal plane.

  § VSD is posteroinferior.

  o Subpulmonary VSD (TBA)

  § Accounts for 8% of DORV.

  § PS does not occur- so pulmonary trunk is markedly dilated.

  § VSD is anterosuperior.

  § VSD is supracristal.

  § The conus septum may narrow the aortic outflow tract of the RV- subaortic stenosis. This may lead to coarctation of aorta and interrupted aortic arch.

  § There is no conus between the VSD and the pulmonary valve.

  o Doubly committed VSD

  § Superior large oblique supracristal VSD related to both semilunar valves.

  § By angiography, this cannot be differentiated from TBA.

  o Remote VSD

  § Most common is complete AV septal defect- gooseneck deformity may not be seen.

  § Posteroinferior VSD involving inlet.

  § Muscular VSD.

  · Right anterior aorta

  o Subaortic VSD- 16% of DORV cases.

  o Subpulmonary VSD- 10% of DORV cases. The VSD is subcristal.

  o Remote VSD

  · Left anterior aorta

  o Subaortic VSD- < 5% of DORV cases. Anterosuperior VSD. PS is common.

  o Subpulmonary VSD- 4% of DORV cases. Perimembranous VSD.

  · Normally related great arteries

  o Subaortic posteroinferior VSD is present.

• Definitions
  • Witham and Neufeld-
    • Both great arteries originate exclusively from the right ventricle (although some override may be acceptable- not in the original definition)
    • Bilateral conus muscle- so no continuity between any semilunar valve and any atrioventricular valve.
  • Lev and Wilcox
    • One arterial trunk and at least half of the other arterial trunk emerges from the right ventricle
• Relationship of the great arteries
  • Right posterior aorta
  • Right lateral aorta – side by side relationship- the classically described relation
  • Right anterior aorta
  • Left anterior aorta
• Position of the VSD
  • Subaortic
  • Subpulmonary- above the septal limb of the crista supraventricularis- Taussig Bing complex
  • Doubly committed- very large and related to both semilunar valves
  • Remote- AV canal, muscular, posterior.

Embryology

• Goor and Edwards- This is a primitive embryological condition which persists.
• Anderson- DORV is a primitive embryological condition as Goor and Edwards have hypothesized. Leftward shift of aortic conus produces TOF while leftward shift of the pulmonary conus produces TGA.
• Manner- abnormal orientation of tricuspid valve to left and anterior leads to DORV.

• Almost always associated with a VSD which is usually a large malaligned outlet VSD.  Hence often referred to as Tetralogy of Fallot with absent pulmonary valve (TOF with APV).
• The pulmonary valve is rudimentary and usually both stenotic and regurgitant.
• The pulmonary arteries are aneurysmally dilated.
• Almost always associated with absence of PDA. In fact, this may be the cause of the syndrome.
• Commonly associated with airway abnormalities which may cause respiratory failure. Abnormally branching pulmonary arteries compress bronchi.
• Rarely, IVS may be intact.
• TOF with APV constitutes 2.5% of TOF.
• 75% of APV has 22q11 deletion. This is the commonest genetic association of APV.

Embryology

• Agenesis or early closure of the ductus plays an important role in the pathogenesis.
• APV syndrome is different from TOF in pathogenesis. Even though VSD and aortic override are present in APV also, obstruction is due to pulmonary annular hypoplasia, not infundibular narrowing.

Pathology

• Pulmonary valve tissue is rudimentary.
• Pulmonary annulus is hypoplastic.
• Proximal pulmonary arteries are aneurysmally dilated. These may compress major bronchi.
• Pulmonary segmental arterioles are replaced by tufts of vessels which compress bronchi.
• Non-restrictive malaligned VSD
• RVH
• Coronary anomalies may occur- single origin, aberrant course.
• MAPCAs may be present.

Clinical presentations

• Hydrops fetalis occurs in 20%.
• Neonatal presentation-
  • Cyanosis
  • Respiratory distress- sometimes needing mechanical ventilation
  • Harsh to-and-fro murmur, single S2, prominent right ventricular impulse, hepatomegaly due to RV failure.
  • Rhonchi due to bronchial narrowing.
  • VSD like- Presentation like a large VSD.

Diagnostic findings

• ECG shows RVH and wide QRS.
• Chest X-ray shows dilated pulmonary arteries with distal attenuation of pulmonary vasculature and cardiomegaly. Right aortic arch may be present.
• Echo makes the diagnosis.
• Cardiac catheterization may be needed for ruling out AP collaterals and for their preoperative coil embolization.
• PA and RV pressures equalize in diastole due to PR. During systole there is a gradient between RV and PA suggesting PS.

Medical management

• Respiratory distress may be lessened by placing the patient prone as this suspends the pulmonary artery off the airways.
• Cyanosis is due to right to left shunt due to pulmonary stenosis, pulmonary regurgitation and abnormal distal pulmonary arteriolar bed.
• Sometimes left to right shunt can occur leading to volume overload.

Surgery

1. VSD closure.
2. Transannular incision to relieve the annular obstruction.
3. Repair of pulmonary arteries- approaches include

• Anterior plication with or without translocation of MPA and RPA anterior to the aorta OR
• Homograft insertion with excision of aneurysmal pulmonary arteries.

• In longstanding unrepaired TOF, right ventricular hypertension induces fibrosis leading to RV systolic and diastolic dysfunctions and ventricular arrhythmias.
• Neonate with TOF should be carefully assessed by echo to see if the PS is so severe that ductal patency is needed. If this is the case, give PGE1 infusion and do early surgery.
• Cyanotic spells can occur in acyanotic TOF also.
• Treatment of cyanotic spells includes oxygen, volume expansion, sedation with morphine or ketamine and vasopressors like phenylephrine.
• Patients with relative anemia are at more risk of cerebrovascular accidents and hypercyanotic spells.

Interventional catheterization procedures

• Preoperative-

Palliation of cyanosis by RVOT stent placement or balloon valvuloplasty. This avoids need for BT shunt which may cause pulmonary artery distortion.
Coil embolization of aortopulmonary collaterals.

• Postoperative- For residual pulmonary artery obstruction- ballooning and stenting.

Primary repair

• This is done via median sternotomy.
• Approaches-
  • Atrial route- This is the preferred route. The VSD is closed by a Dacron patch. RVOT obstruction is resected. Atrial route was earlier done only for patients with coronaries crossing the RVOT. Now it is done for other patients also as it avoids the need for ventriculotomy.
  • Right ventriculotomy- A vertical incision is made over the infundibulum. RVOT obstruction is relieved. VSD is closed by a Dacron patch. RVOT is patched with pericardium. If the pulmonary annulus is hypoplastic (Z score preoperatively and visual impression of the surgeon intraoperatively), the initial incision is extended onto the pulmonary artery. A transannular patch is placed. A monocusp pericardial valve may be placed to avoid pulmonary regurgitation.
  • Combined atrial and transpulmonary approach- avoids need for ventriculotomy.
• AP collaterals- These are coiled prior to surgery to avoid steal phenomenon during cardiopulmonary bypass which causes neurologic sequelae. If it constitutes the sole blood supply to the lung, it should be incorporated into the final repair.

Palliative procedures

• Initial palliative BT shunt is not preferred due to PA distortion, ventricular volume loading and the surgical risks of an additional thoracotomy. Primary repair is directly done. But palliation may need to be done in severe PA hypoplasia and aberrant LAD form RCA.
• Blalock Thomas Taussig shunt and central shunt are used now. Waterston shunt and Potts shunt are not used now. Modified BTT shunt is the most commonly used one. It is done opposite to the side of the aortic arch. Shunt size in newborn is usually 3.5 to 4 mm.

Surgical results-

• Early primary repair is not associated with higher incidence of early complications or late reintervention compared to late repair. Also, primary repair is not associated with more reintervention for residual obstruction  compared to staged repair. Hence, early primary repair is preferred though repair in first 3 months of life increases intensive care morbidity.
• Hospital survival for repair is 100% even for early surgery. 20 year survival after primary repair is 98% for TOF with PS and slightly lower for TOF with primary atresia.
• In TOF with PS, after primary repair, at 2 years 25% needed reoperation usually for residual obstruction in RV or PA. The indication for reoperation in older patients is different and is residual VSD.

Long-term follow-up

• Early repair may be associated with less long term incidence of arrhythmias, ventricular dysfunction and cognitive dysfunction.

Sudden death and arrhythmias

• Incidence of sudden death is 1.2% at 10 years, 2.2% at 20 years, 4% at 25 years and 6% at 30 years.
• Sudden death is not more in patients who underwent surgery before 80s.
• Ventricular arrhythmias are more in patients who undergo surgery at older age. These patients are predisposed to ventricular arrhythmias before surgery itself due to their older age and surgery does not decrease the chance of ventricular arrhythmias.
• Ventricular arrhythmias are more in patients with PR and in those with RV dilation.
• EP studies are not clearly shown to predict sudden death in patients with ventricular arrhythmias.
• Other predictors of sudden death are significant PR, sustained ventricular arrhythmias, QRS duration more than 180 msec and LV dysfunction.
• Other arrhythmias noted in the long term are sinus dysfunction, atrial flutter , atrial fibrillation and supraventricular tachycardia. The incidence of supraventricular tachycardia is 10% at 12 years after repair.

Residual defects and hemodynamic abnormalities

• Branch PA stenosis
  • After shunt procedures.
  • After RVOT patch, due to compression by the redundant patch.
  • Treated by ballooning or stenting- the complications include aneurysms, stent migration and stent thrombosis.
  • Redundant RVOT patch should be surgically revised.
• Membranous subaortic stenosis- uncommon late complication.
• Coronary to RV fistula
• Pulmonary regurgitation
  • All patients have PR by echo.
  • Some have audible PR.
  • Pan-diastolic PR with end-diastolic velocity of 1 m/s indicates mild PR and good pulmonary valve anatomy.
  • PR signal ending before the end of diastole indicates that pulmonary valve function is poor and that the RV is stiff. This occurs due to equalization of PA diastolic pressure and RV diastolic pressure in diastole itself.
  • PR may occur due to increased pulmonary arterial impedance which is due to either stenosis of main or branch pulmonary arteries or elevated LA pressure due to causes like LV dysfunction. If branch PA stenosis is the cause of PR, it may be treated by interventional catheterization. If LV dysfunction is the cause of PR, it may decrease with treatment of the LV dysfunction.
  • For significant PR, pulmonary valve replacement (homograft) will be needed.
• Tricuspid regurgitation
  • Present in many.
  • Not audible unless RV pressure is elevated.
  • May need repair.
• Aortic dilation
  • Aorta is dilated in TOF patients after repair. This dilation may progress.
  • Avoid isometric exercise and high blood pressure.
  • Serial monitoring for enlargement and development of AR is needed.

Exercise testing

• Reduced exercise capacity is present in patients with PA stenosis, PR or RV dysfunction.

Bacterial endocarditis

• Prophylaxis is needed in unoperated patients, palliated patients, in repaired patients for 6 months and in repaired patients with prosthetic valves.

http://www.heartpearls.com/2009/06/tetralogy-of-fallot-an-article-part-1.html

http://www.heartpearls.com/2009/06/tetralogy-of-fallot-an-article-part-2.html

http://www.heartpearls.com/2009/08/tetralogy-of-fallot-an-article-part-3.html

• Some patients may have left to right shunt will full arterial oxygen saturation.
• PA pressure is normal or low, never is it high.
• All patients have subpulmonic obstruction.
• VSD is non-restrictive usually. So, RVH is in proportion to the LV mass.
• Rarely, VSD is restrictive. Then RVH will be severe due to suprasystemic RV pressure.
• Exercise produces cyanosis due to decrease in systemic vascular resistance leading to increased right to left shunting.
• Hypercyanotic episode is due to acute increase in infundibular obstruction.

Clinical features

• Fetal diagnosis is possible by echo.
• Newborn with severe RVOT obstruction may have only mild cyanosis till ductus closes.
• Hypercyanotic spells or tetralogy spells-
  • More common in patients with iron deficiency anemia.
  • Mechanisms-
    • Acute increase in subpulmonic obstruction due to contraction due to catecholamines or due to hypovolemia.
    • Decreased systemic vascular resistance
• Severe cyanosis.
• Hyperpnea due to hypoxia and metabolic acidosis.
• Can be lethal.
• Murmur intensity is markedly decreased.
• Squatting-
  • Usually after exercise.
  • Instinctive- to increase arterial saturation.
  • Increased systemic vascular resistance decreases shunting.
• Left parasternal impulse is present.
• S2 is single in almost all patients.
• S2 is often loud due to anterior aorta.
• No S3 or S4.
• Wide pulse pressure if
  • PDA
  • AP collaterals or
  • Palliative shunt.
• Mid-systolic murmur
  • Site – inferior to the site of valvular PS murmur
  • Crescendo-decrescendo or plateau shaped
  • Harsh
  • Intensity is inversely proportional to RVOT obstruction
  • Decreases during hypercyanotic spell
  • Absent in TOF with PA
• EDM
  • AR
  • PR
    • In TOF with PA
    • Harsh sawing to and fro murmur
    • Pathognomonic
• AES (aortic ejection sound) – in older patients.
• Continuous murmur-
  • PDA
  • AP collaterals (murmur in back)
• Postoperative-
  • S2 is single (only A2).
  • MSM of PS is often heart due to some degree of residual PS.
  • Low frequency EDM of PR is heart in many.
  • PSM if residual VSD.

Diagnostic studies

• ECG-
  • RVH is evident beyond 3 months when neonatal RVH should have resolved.
  • Right axis deviation is present.
  • In older untreated patients, RV fibrosis may cause ventricular ectopy or arrhythmias.
• Chest X-ray-
  • No cardiomegaly.
  • Upturned apex- boot-shaped heart or coeur en sabot.
  • Concavity of left heart border due to RV infundibular hypoplasia and MPA hypoplasia.
  • Decreased pulmonary vascularity.
  • Right aortic arch in 25%.
• Blood investigations-
  • Hematocrit more than 65% will cause hyperviscosity syndrome.
  • Microcytosis due to iron deficiency can cause cerebrovascular events and should be avoided.
• Echocardiography-
  • With more than 50% override, look for bilateral conus to rule out DORV.
  • TR will not occur despite RV hypertension.
  • In the first few days of life, PS severity is underestimated due to elevated PVR and due to PDA.
  • The VSD is just below the RCC, at 10’O clock position.
• Cardiac catheterization-
  • Stenting for PS has been done along with surgery.
  • AP collaterals can be closed with coils.
  • RV hypertension is equal to LV hypertension.
  • PA anatomy and coronary anatomy clarifications are the usual indications for cath study.
  • PA pressure is normal or low. Elevation suggests diffuse distal pulmonary arterial stenosis.
  • With AP collaterals, calculation of right to left ventricular shunt gives a falsely low value.
  • Pulmonary artery anatomy delineation is especially important in patients who have undergone palliative aortopulmonary shunts.
  • AP collaterals usually originate from the descending aorta. Occasionally they originate from the brachicephalic vessels as in pulmonary atresia.

http://www.heartpearls.com/2009/06/tetralogy-of-fallot-an-article-part-1.html

http://www.heartpearls.com/2009/06/tetralogy-of-fallot-an-article-part-2.html

http://www.heartpearls.com/2009/08/tetralogy-of-fallot-an-article-part-4.html

The tricuspid valve is absent. The nearby inflow portion of the right ventricle is hypoplastic.

An ASD is always present to allow blood to leave the right atrium to enter the left atrium. There is usually a VSD for return of flow to the right side. In cases without VSD, there will be left to right flow through a ductus.

Classification

The great arteries are normally related in 70% and are transposed in 30%. The normal great artery relation type has 50% having restrictive VSD and PS, 10% having large VSD and no PS and 10% having intact ventricular septum and pulmonary atresia. The transposed great artery group has 20% having no PS, 8% having PS and 2% having pulmonary atresia. (Draw the connections yourself for a better idea.)

In the transposed great artery group, there will mostly be a VSD. Patients without a large VSD develop decreased aortic flow and shock.

Coarctation of aorta is the commonest associated anomaly. It is more common in patients with transposed great arteries.

Physiology

We can divide the patients into three groups- decreased pulmonary blood flow group, increased pulmonary blood flow group and balanced pulmonary blood flow group. The decreased pulmonary blood flow group is the largest and consists of NRGA+small VSD+PS, NRGA+ intact IVS+ pulmonary atresia, TGA + PS and TGA + pulmonary atresia groups. The increased pulmonary blood flow group consists of NRGA + large VSD + no PS and TGA + no PS groups.

The decreased pulmonary blood flow group has poor blood oxygenation leading to cyanosis and death. The increased pulmonary blood flow group does not have deep cyanosis, but has heart failure initially as the increased pulmonary blood flow will further overload the already overloaded left ventricle and then pulmonary vascular disease.

Some patients have pulmonary blood flow just enough to avoid deep cyanosis and not enough to cause heart failure or pulmonary vascular disease. These form the balanced pulmonary blood flow group.

Clinical and lab findings

Cyanosis is always present as the right sided blood always has to mix with left sided blood.

S2 is usually single as most patients have decreased pulmonary blood flow.

ECG shows right or biatrial hypertrophy. LVH is present. There will be left axis deviation.

Chest X-ray also shows right atrial enlargement and left ventricular enlargement.

Treatment

The commonest group is having normally related great arteries and decreased pulmonary blood flow. Immediate relief is by PGE1 infusion to increase pulmonary blood flow. In cases in which the ASD is small, Rashkind procedure (balloon atrial septostomy) may be done. The surgery is connecting the venacavae to the pulmonary artery- this is called Fontan surgery. This cannot be done in the neonate as pulmonary vascular resistance is high in the neonate and so venous blood cannot go into the high pressure pulmonary circulation. So first, a subclavian artery is connected to a pulmonary artery by a side to side window- this is called Blalock-Taussig shunt. At 3 to 6 months, when we are sure that pulmonary pressure has fallen enough, we can proceed to direct venous blood to the pulmonary circulation. The BT shunt is taken down. But full Fontan would be a major shift in the hemodynamics. So we direct only SVC blood to the pulmonary circulation at this 3 to 6 month period. This is done by bidirectional Glenn shunt or hemi-Fontan surgery. At 1 to 2 years after this surgery, full Fontan surgery is done by connecting IVC blood also to the pulmonary artery.

For the increased pulmonary blood flow group also, the final pathway is BDG or hemi-Fontan at 3 to 6 months followed by Fontan after 1 to 2 years. But in the neonatal period, the increased pulmonary blood flow can cause heart failure and pulmonary vascular disease- so to decrease pulmonary blood flow, PA banding will be needed.

For the balanced pulmonary blood flow group, till BDG or hemi-Fontan is done at 3 to 6 months, no surgery is needed, but they need close observation to monitor for decrease in pulmonary flow due to decrease in size of the VSD.

For the TGA group with a restrictive VSD, the neonatal problem is decreased systemic flow. So, either the VSD has to be enlarged or the main pulmonary artery is connected to the aorta to give blood to the aorta with the branch pulmonary arteries being detached from the main pulmonary artery to be connected to the aorta, the aorta now receiving blood from both the VSD and the main pulmonary artery, thus maintaining adequate systemic flow. Fontan surgery is done later as in other cases.

Bidirectional Glenn surgery- this refers to end-to-side SVC to right pulmonary artery shunt. When converting this to Fontan, the IVC is connected to a tubular pathway created in the right atrium, the tubular pathway being connected to the SVC orifice.

In the hemi-Fontan surgery, a side to side connection is made between the SVC and adjacent right atrium (this part of the right atrium having been sealed off from the rest of the right atrium) and the main pulmonary artery. When converting this to Fontan, a lateral atrial tunnel is made to connect IVC to this area.

The Fontan surgery is usually done at around 2 years of age. It will be dangerous with a high pulmonary vascular resistance (>2 U/m2) or pulmonary artery pressure (mean > 18 mmHg). Distorted pulmonary arteries from previous shunt surgeries also increase  the risk. AV valve regurgitation also increases the risk. LVEF less than 60% and LVEDP more than 12 mm Hg are the other risk factors. Early complications are heart failure, low cardiac output, persistent pleural effusion due to high venous pressure, thrombosis in systemic venous pathways due to sluggish flow and acute liver dysfunction due to low cardiac output. Late complications are supraventricular arrhythmias, ascites, protein losing enteropathy which causes death and cyanosis due to venous pathway obstruction, intra-atrial baffle leakage or pulmonary AV fistula.

• In the fetus, of the total right ventricular output, 85% goes through the ductus.
• Persistent fetal circulation means that the fetal ductal right to left shunt persists after birth.
• Ductus dependent circulations are left sided obstructions, right sided obstructions and TGA.
• Ductus histology peculiarities are intimal cushions and prominent smooth muscle.
• Functional closure of ductus begins within 15 hours and ends within 2 weeks.
• Anatomical closure of ductus usually occurs within 3 weeks.
• Persistent patency of ductus means that it is patent for more than 3 months in a full term baby.
• The main constrictor of the ductus is oxygen and the main dilator is PG-E2.
• In the early fetal life, ductus is more responsive to PG-E2 while in late fetal life, it is more sensitive to oxygen.
• Immediately after birth, ductus flow is bidirectional. This becomes left to right soon. This flow decreases to become nil within 48 hours.
• In the preterm baby, the ductus may close any time within 1 year.
• In the full term baby, the dutus may close any time within 3 months.
• In the preterm baby, ductus may decrease cerebral blood flow by stealing circulation from the aorta into the pulmonary artery.
• With first trimester rubella, heart disease occurs in two-third of babies, one-third of whom will be having a patent ductus arteriosus.
• The ductus may be highly restrictive, moderately restrictive or non-restrictive. If highly restrictive, there is no hemodynamic problem. If moderately restrictive, there is left to right flow causing left ventricular volume overload. Pulmonary artery pressure is not much increased due to gradient across the PDA. So, pulmonary vascular resistance does not increase. If non-restrictive, first there is left to right shunt and left ventricular volume overload since systemic vascular resistance is more than pulmonary vascular resistance. Then, since pulmonary artery is having systemic pressure, pulmonary vascular resistance increases. When it exceeds systemic vascular resistance, right to left shunt occurs.
• Only 5% of PDAs are non-restrictive.
• With non-restrictive PDA, right ventricle is exposed to systemic pressure.
• With non-restrictive PDA, right ventricle is not exposed to supra-systemic pressures.

History

• Less common mechanisms of ductal closure are healed vegetations and thrombus.
• PDA is 2 to 3 times more common in females.
• Female prevalence increases with age.
• It is more common in siblings and offspring.
• With maternal rubella, PDA co-exists with pulmonary artery stenosis.
• In rubella syndrome, birth weight is low.
• Patency of ductus is 6 times more at high altitude.
• Commonest cause of death due to the ductus is heart failure.
• Less common causes of death are ductal rupture, pulmonary artery rupture and ductal dissecting aneurysm.
• Non-patent ductal aneurysm can rupture, cause pressure symptoms, cause embolisms and can get infected.
• Infective endarteritis does not occur with a non-restrictive ductus.
• Infective endarteritis occurs at pulmonary end or at the site of jet impinging on the pulmonary artery wall.
• Preterm with non-restrictive ductus can have cerebral hemorrhage due to increased pulse pressure.
• PDA may cause symptoms during the first year of life.
• Moderately restrictive PDA causes heart failure in the third decade of life.
• In Eisenmenger PDA, exercise causes leg fatigue but not dyspnoea because desaturated blood goes to the legs, but not to the respiratory center and carotid bodies.
• In Eisenmenger PDA, the right ventricle does not have supra-systemic pressure. So, there is no angina from right ventricular strain.
• With maternal salicylate ingestion, ductus closure can cause massive tricuspid regurgitation and right to left atrial shunt in the neonate.

Physical appearance

• PDA may be associated with trisomy 18, Char syndrome and maternal rubella.
• Trisomy 18 is characterized by lax skin, clinodactyly (overlapping fingers) and rocker bottom feet.
• Char syndrome is inherited as a defect in chromosome 6 and is characterized by abnormal face and hands.
• With differential cyanosis of Eisenmenger PDA, the left hand may also be slightly cyanotic and have finger clubbing.
• With neonatal right to left shunt via PDA, a line demarcates cyanosis below and no cyanosis above. This line extends from above the left shoulder to below the right axilla.

The arterial pulse

• The classical wide pulse pressure may be absent in preterm due to steal effect into the pulmonaries.
• With Eisenmenger, the pulse volume returns to normal. But even in this situation, wide pulse pressure can occur due to pulmonary regurgitation.

The jugulars

• With Eisenmenger, a wave is not prominent as would be expected, as right ventricular pressure is never suprasystemic.

The precordium

• Moderately restrictive VSD- LV impulse is hyperdynamic. RV impulse is not prominent.
• Non-restrictive VSD- Before Eisenmeger, LV impulse is hyperdynamic, after Eisenmemger, LV impulse is not prominent. RV impulse is always heaving. Loud P2.

Auscultation

• The continuous murmur may not be present in late diastole and early systole.
• The classical character description is rough and thrilling.
• Maximum intensity of the murmur is at or just after the second heart sound.
• Highly restrictive PDA- murmur has high frequency.
• Moderately restrictive PDA- murmur has coarse quality with eddy sounds- called machinery murmur.
• Murmur is loudest in first or second left intercostal space and left infracalvicular area.
• The murmur may rarely be intermittent due to ductal angulation or valve.
• The murmur is said to have “systolic reinforcement”.
• With rise in pulmonary vascular resistance, the diastolic part disappears first and then the murmur disappears altogether.
• With Eisenmenger PDA, the findings are differential cyanosis + findings of pulmonary hypertension (loud P2, pulmonary ejection sound, single or closely split S2).
• A normal newborn may have a systolic murmur due to ductal flow before ductal closure.
• In a newborn destined to have PDA, first there is a systolic murmur only. This then becomes a continuous murmur when pulmonary vascular resistance falls.
• Infants with large left to right shunt across a PDA may have a to-and-fro over the cranium.
• With a large left to right shunt across a PDA, A2 may be delayed to cause a paradoxical split.

ECG

• Superior axis can occur in rubella syndrome.

Echocardiogram

• With a large left to right shunt across the PDA, aorta distal to the ductus shows diastolic flow reversal.

The hallmark of tetralogy of Fallot is anterior and cephalad deviation of the conotruncal septum.

Pulmonic stenosis – is always significant and hence pulmonary artery pressure is normal or low, never high as in pure VSD. The obstruction is subpulmonic. If this is severe, distal obstructions are more commonly present. Usually pulmonary arteries are of adequate size to permit surgical repair. In pulmonary atresia, pulmonary artery size may be too less for repair.

Subpulmonic obstruction is due to both antero-cephalad deviation of the conotruncal septum and muscular hypertrophy of the deviated septum and the right ventricular free wall. In addition, there may be intracavitary obstruction due to hypertrophied muscle bundles.

The pulmonary valve is commonly small and stenotic and is usually unicuspid or bicuspid. Supravalvular discrete stenosis may occur. Branch ostial stenosis may occur, especially on the left. In pulmonary atresia, the pulmonary arteries are very small and are feeded by aortopulmonary collaterals.

Ventricular septal defect- This has fibrous continuity between tricuspid and aortic valve and hence is a true perimembranous defect, even though it lies in a subarterial location. It is non-restrictive by definition, though some defects may be restrictive due to tricuspid valve tissue.

Aortic override- This may vary from 15% to 95%. Override of more than 50% does not mean double outlet right ventricle- this needs presence of both subaortic conus (absent aorto-mitral continuity) and subpulmonary conus. Aortic override is not only due to the malalignment. It is also due to aortic dilation due to malseptation of the conotruncus and due to rotation of the aorta so that the right aortic sinus becomes more anterior (and left).

Coronary arteries-

1. 15% have a large conal branch or accessory left anterior descending artery.
2. 5% have origin of left anterior descending artery from right coronary artery. This then crosses the right ventricular outflow tract- this is important surgically as the surgeon cannot approach through this area for repair.
3. 4% have single origin of coronaries.

Coronary artery origin has to be found by echocardiography, angiography or MRI before surgery.

Aortic arch anomalies – These are more common if there is Catch 22. Right aortic arch is present in 25%. Aberrant origin of ipsilateral subclavian artery and origin of left subclavian artery from pulmonary artery are sometimes seen.

Aortopulmonary collaterals- Rabinovich type 1 (bronchial artery collaterals) collaterals are uncommonly present in Tetralogy of Fallot with pulmonic stenosis. Collaterals are much more common in Tetralogy of Fallot with pulmonary atresia.

Other anomalies- ASD is present in 83%. Left superior vena cava is found in 11%. Atrioventricular septal defect may be associated, especially in Down’s syndrome. Left sided anomalies are rare.

http://www.heartpearls.com/2009/06/tetralogy-of-fallot-an-article-part-1.html

http://www.heartpearls.com/2009/08/tetralogy-of-fallot-an-article-part-3.html

http://www.heartpearls.com/2009/08/tetralogy-of-fallot-an-article-part-4.html