Ventricular Septal Defects – A Review

Ventricular Septal Defect

• Henri Roger was the first man to describe a ventricular septal defect, in 1879 he wrote: “A developmental defect of the heart occurs from which cyanosis does not ensue in spite of the fact that a communication exists between the cavities of the two ventricles and in spite of the fact that the admixture of venous blood and arterial blood occurs. This congenital defect, which is even compatible with long life, is a simple one. It comprises a defect in the interventricular septum”

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• Roger in 1879 - first described

• Eisenmenger – 1897 - autopsy finding

• Pathophysiology by Abbott (1936) & Selzer (1949)

• 1952 – Muller and Danman- pulmonary artery band

• 1954 – Lillehei and associates – First vsd repair

• 1961 – Kirklin - Repair of VSD in infants

• 1987 – Device closure by Lock et al with Rashkind double umbrella

HISTORICAL ASPECT

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• VSD occurs during the first 8 weeks of fetal life• 3 components – Interventricular muscular partition• - Endocardial cushions• - Bulbar ridges that separate great vessels

EMBRYOLOGY

Four cushions (AVC) have developed at the A/V junction; the superior and inferior cushions willmeet to divide the AV orifice (AVO)into the tricuspid and mitral valves. The inferior septal crest (VS)will aim to meet the divided valve where the cushions fuse.

Formation of IV septum IV septum moves upwards

from the floor of the bulboventricular cavity, division into right and left halves. It meets fused AV cushions and partially fuse with them.

Two ridges right and left arise in conical upper part of bulboventricular cavity which fuse with each other to form bulbar septum.

Gap persists between the two-filled by proliferation of tissue from the AV cushions.

Membranous IV septum

• Ant part separates right and left ventricles.

• Post part separates right atrium and left ventricle.

• This is because the interatrial and interventricular septum don’t meet in the midline.

Classification by Soto et. al

Ventricular Septum

• The membranous septum is small and is located at the base of the heart between the inlet and outlet components of the muscular septum and below the right and noncoronary cusps of the aortic valve.

• The septal leaflet of the tricuspid valve divides the membranous septum into 2 components, the pars atrioventricularis and the pars interventricularis.

• Tricuspid, aortic, and mitral continuity is via this central fibrous body.• True defects of the membranous septum are surrounded by fibrous

tissue without extension into adjacent muscular septum.• Defects that involve the membranous septum and extend into 1 of

the 3 muscular components are called perimembranous, paramembranous, or infracristal.

• The muscular septum is a nonplanar structure that can be divided into inlet, trabecular, and infundibular components.

• The inlet portion is inferioposterior to the membranous septum. • It begins at the level of the atrioventricular valves and ends at

their chordal attachments apically. • An inlet VSD has no muscular rim between the defect and the

atrioventricular valve annulus. • Defects in the inlet muscular septum are called inlet VSDs.• Another classification scheme divides the inlet septum into the

atrioventricular septum and the inlet septum. • Defects in the inlet septum can include abnormalities of the

tricuspid and mitral valves that are called common atrioventricular canal defect.

• The trabecular septum is the largest part of the interventricular septum.

• It extends from the membranous septum to the apex and superiorly to the infundibular septum.

• A defect in the trabecular septum is called muscular VSD if the defect is completely rimmed by muscle.

• The location of defects in the trabecular septum can be classified as anterior, midmuscular, apical, and posterior, as proposed by Kirklin et al.

• The infundibular septum separates the right and left ventricular outflow tracts.

• On the right side, it is bordered by the line from the membranous septum to the papillary muscle of the conus inferiorly and the semilunar valves superiorly.

• The right side of the infundibular septum is more extensive.• Defects in the infundibulum are called infundibular, outlet,

supracristal, conal, conoventricular, subpulmonary, or doubly committed subarterial defects.

• A deficient infundibular septum may be present with corresponding degrees of malalignment.

• Many defects involve 1 component of the ventricular septum. • Perimembranous defects extend into the adjacent muscular septum

and have been called perimembranous inlet, perimembranous muscular, and perimembranous outlet on the basis of the extension.

• Abnormalities of the tricuspid valve adjacent to these defects can be in the form of an aneurysm partially or completely occluding the defect.

• The tricuspid valve can have perforations, clefts, or commissural abnormalities.

• There can be straddling of the mitral valve in the presence of infundibular defects.

• Inlet defects can involve malalignment of the atrial and ventricular septa.

Location of various types of ventricular septal defect as viewed from the right ventricular aspect of the septum

The Ventricular Septum and related Defects

1. Membranous

2. Outflow

3. Trabecular septum

4. Inflow

5. Subarterial / Supracristal

Nomenclature / ClassificationKIRKLIN Classification

• TYPE I- Conal,Supracristal,

Infundibular,Subarterial

• TYPE II – Perimembranous

• TYPE III – Inlet / AV canal type

• Type IV – Muscular

Classification

Anderson et al

• Perimembranous

• Muscular

• Doubly committed Juxta arterial defects

• Juxtatricuspid

Van Praagh et al

• AV canal type

• Muscular VSDs

• Conoventricular (Proximal Conal)

• Distal Conal(Outlet septum)

Lesion Size• Restrictive VSD

– < 0.5 cm2 (Smaller than Ao valve orifice area)– Small L to R shunt– Normal RV output– 75% spontaneously close < 2yrs

• Non-restrictive VSD– > 1.0 cm2 (Equal to or greater than to Ao valve orifice area)– Equal RV and LV pressures– Large hemodynamically significant L to R shunt– Rarely close spontaneously

Based on size 1) Large : > 2/3rd of aortic annular size,

or > 1cm2/m2 of BSA Peak RV sys = LV sys pressure(Difference < 20 mm of Hg) PA/Ao Systolic Pressure > 0.66 Qp/Qs > 2.2

2) Moderate : 1/3rd to 2/3rd the size of aortic annulus, or >0.5-1 cm2/m2 of BSA RV pressure to ½ of LV (Difference > 20 mm of Hg) PA/Ao Systolic pressure < 0.66 Qp/Os>2.0

3) Small : One third of aortic annular size, or < 0.5 cm2/m2 of BSA insufficient size to raise RV pressure, PA/Ao systolic pressure <0.3 & Qp/Qs < 1.75

Physiology• The primary anatomic variable that determines the physiologic state of the patient

is defect size. • In small or medium-sized VSD, the size of the defect limits the left-to-right shunt;

however, in large defects (those approximately the size of the aortic orifice), there is essentially no resistance to flow across the VSD, and the relative resistances of the systemic and pulmonary circulations regulate flow across the defect.

• Pulmonary vascular resistance determines the magnitude of the left-to-right shunt in infancy.

• Following birth, the small muscular pulmonary arteries normally change from the fetal state, with a small lumen and a thick medial muscle layer, to thin-walled structures with increased lumen size.

• The normal rate of decline in pulmonary vascular resistance that accompanies these changes is such that the right ventricular pressure is near adult levels within 7 to 10 days.

• In the presence of large VSDs, the rate of this process is delayed, and the increased pulmonary resistance prevents massive shunting of blood through the lungs.

• Elevation of left atrial pressure (pulmonary venous pressure) plays an important role in maintaining this phase of pulmonary vascular constriction.

Spontaneous closure

• The incidence varies considerably.

• It is reported as 50-75% for restrictive perimembranous and muscular defects observed from birth.

• Moderately restrictive and non-restrictive defects also close spontaneously but incidence is low, around 5-10%.

• Most defects destined to close do so within first year of life, with approx 60% closing by 3 yrs and 90% by 8 yrs of age.

• Multiple defects have a strong tendency to close spontaneously.

Mechanism of spontaneous closure

• Adherence of the septal tricuspid leaflet tissue to the margin

• Prolapse of the aortic cusp

• Intrusion of sinus of valsalva aneurysm

• Growth of the septum

Clinical Features• VSDs can be detected by auscultation. • The murmurs are typically described as holosystolic or pansystolic. • The grade of murmur depends on the velocity of flow; the location

of murmur is dependent on the location of the defect. • Smaller defects are loudest and may have a thrill. • Muscular defects can be heard along the lower left sternal border

and may vary in intensity as the defect size changes with muscular contraction throughout systole.

• Infundibular defects shunt close to the pulmonary valve and can be heard best at the left upper sternal border.

• Perimembranous defects may have an associated systolic click of a tricuspid valve aneurysm.

• In the setting of low pulmonary vascular resistance, larger defects have murmurs of constant quality that vary little throughout the cardiac cycle and less commonly have an associated thrill.

• These defects will have a corresponding increase in mitral flow, resulting in a diastolic rumble at the apex.

• There may be evidence of left ventricular volume overload on palpation of the precordium with a laterally displaced impulse.

• Elevated pulmonary pressure causes an increase in the pulmonary component of the second heart sound.

• Large defects with no shunt and defects with Eisenmenger physiology and right-to-left shunt often do not have a VSD murmur.

• Patients with Eisenmenger syndrome often are cyanotic with clubbing. • They have a right ventricular heave on palpation of the precordium and a

loud pulmonary component of the second heart sound. • A VSD murmur may not be present.

Electrocardiography

Moderately Restrictive VSD

Non-Restrictive VSD

Eisenmenger Syndrome

Chest X-rays

Restrictive Perimembranous VSD

VSD with Eisenmenger

Echocardiography

• Two-dimensional echocardiography, coupled with Doppler echocardiography and color flow mapping, can be used to determine the size and location of virtually all VSDs.

• Also, Doppler echocardiography can provide physiologic information regarding right ventricular and pulmonary artery systolic pressures and the interventricular pressure difference.

• VSD sizes can be measured in absolute terms from the two-dimensional image.

• Doppler and color flow echocardiography have been used to demonstrate the shunting patterns in VSD.

Cardiac Catheterization

• It is performed to

– document the number of defects– evaluate the magnitude of shunting– estimate pulmonary vascular resistance– estimate the workload of the two ventricles – document or exclude the presence or absence of associated defects– provide the surgeon or interventional cardiologist with a clear

anatomic picture of the location of the defect (or defects) in those patients needing intervention.

Clinical Course and Prognosis• In general, long-term survival is good.

• Patients with small defects have an excellent prognosis, albeit with a small risk of endocarditis, aortic valve insufficiency, and late cardiac arrhythmia.

• A large number of these defects close spontaneously, this number approaches 75% to 80%, with most closing in the first 2 years of life.

• Endocarditis is a lifelong risk in unoperated patients (18.7 per 10 000 patient-years) and those with residual defects.

• Proper prophylaxis and periodic follow-up are indicated.

• Patients with moderate-sized defects may develop large left-to-right shunts in infancy, and their main risk is heart failure between 1 and 6 months of age.

• Usually, this group can be managed medically without surgical intervention during infancy.

• If catheterization demonstrates that the right ventricular pressure is normal or only mildly elevated, most of these patients will have decreasing shunts over the first year of life and never require operative intervention.

• Approximately 15% to 20% of these patients continue to have large left-to-right shunts following infancy. If the clinical signs indicate that the shunt remains large, operation is recommended.

• Patients with large defects are the most difficult to manage because of the dangers of mortality in the first year of life owing to heart failure and associated pulmonary infections as well as the problem of development of elevated pulmonary vascular resistance.

• Patients who respond poorly to medical therapy and who continue to show signs of a large left-to-right shunt with growth failure and pulmonary infection should undergo surgery within the first year of life.

• The development of pulmonary vascular disease is uncommon in patients who undergo surgery before 2 years of age but may occur in as many as a quarter of patients with large defects who undergo surgery after 2 years of age.

• In addition, there was a progressively higher frequency of increased postoperative pulmonary resistance in the older patients.

• These data indicate that the pulmonary vascular obstructive changes can occur as early as 2 years of age.

• Generally, infants with VSD and increased pulmonary artery pressure should undergo repair between 3 and 12 months of age.

Management

• The management of VSDs varies depending upon several factors including -

– The size of the defect– The likelihood of spontaneous closure or decrease in size over time– The involvement of one or more cardiac valves– The anticipated difficulty and effectiveness of surgical closure

Small VSD

• Infants who continue to have a murmur, but are otherwise asymptomatic and growing well should be seen again by the pediatric cardiologist at approximately 12 months of age.

• They are expected to remain asymptomatic and to experience possible disappearance of the murmur over time.

• If at the 12-month visit, the murmur is gone, repeat echocardiogram is not necessary, unless clinical concerns arise (ie, endocarditis).

• However, some physicians opt to obtain an echocardiogram to verify closure. • If there is no evidence of a defect on examination or echocardiography, no

additional follow-up is necessary. • Children in whom closure is associated with aneurysmal tissue should be

followed every two to three years to monitor the possible development of obstruction to right ventricular outflow.

Moderate to large VSD • Infants with moderate to large VSDs usually become symptomatic

within the first months of life as pulmonary vascular resistance (PVR) declines.

• The frequency of cardiology follow-up in these infants depends upon the progression of symptoms and the response to medical therapy.

• The primary care provider should monitor the infant for manifestations of heart failure (eg, poor weight gain, tachypnea, tachycardia) and for changes in physical examination that should prompt an earlier appointment with the cardiologist.

• These include a hyperdynamic precordium, displacement of the cardiac apex outside the midclavicular line, increased intensity of the second component of the second heart sound, or the onset of a diastolic murmur.

• Medical therapy, should be instituted in infants with obvious cardiac failure.

• The goals of therapy include: – relief of symptoms, – normalization of growth, – minimization of frequency and severity of respiratory infections

• The symptoms of children with heart failure from left-to-right shunts can improve with medical therapy, postponing and possibly avoiding the need for surgical correction.

• However, despite maximum medical management, 50 percent of patients with moderate to large VSDs continue to have tachypnea and or/failure to thrive.

• These patients undergo surgical closure in infancy, preferably before six months of age.

Eisenmenger syndrome

• The patient with Eisenmenger syndrome needs very specialized care at centers, with trained personnel capable of managing myriad medical problems.

• Arrhythmias, endocarditis, gallstones, gouty arthritis, hemoptysis, pulmonary artery thrombosis, and symptomatic hypertrophic osteoarthropathy are frequently seen.

• Pregnancy is poorly tolerated and many believe contraindicated in this disorder.

• Echocardiography and magnetic resonance imaging are used to evaluate right ventricular function.

SURGICAL MANAGEMENT

• Decisions regarding surgery, and the type of surgical procedure, must be made on a case by case basis.

• Factors to consider include – the severity of failure – likelihood of progression of pulmonary vascular disease– other complications – likelihood of reduction in size or spontaneous closure of the defect– the morbidity and mortality of the procedure in young infants in the

center where the surgery is to be performed

Indications

• Infants <6 months (<3 months for those with trisomy 21) who have uncontrolled heart failure despite maximal medical and dietary interventions or who have pulmonary hypertension.

• Children with a persistent significant shunt (Qp:Qs >2:1) with elevated PA pressures should undergo surgical repair.

• Children with a persistent significant shunt and normal PA pressures may be considered for surgical closure. However, the optimal management remains controversial. A conservative nonsurgical approach for these patients consists of annual follow-up for assessment of change in clinical status and estimation of PA pressure by echocardiogram and examination.

• Subpulmonic and membranous defects, regardless of size, with aortic regurgitation should be surgically corrected before the aortic valve is permanently damaged. The decision to close small defects with aortic valve prolapse without aortic regurgitation is controversial.

Intracardiac repair

• Direct patch closure of the defect under cardiopulmonary bypass and/or deep hypothermia is the procedure of choice in most children and at most centers.

• The approach (eg, transatrial, right ventriculotomy, apical ventriculotomy) depends upon the type and location of the defect, as well as the preference of the surgeon.

• Whenever possible, ventriculotomies should be avoided.

• Current surgical mortality is <3% for single VSDs and VSDs with aortic valve insufficiency (AI), and about 5% for multiple VSD repair.

• Most perimembranous and inlet defects are repaired using a transatrial surgical approach (the septal leaflet of the tricuspid valve may need to be detached to repair some inlet defects).

• Defects in the outlet septum can be repaired through the pulmonary valve.

• Multiple muscular defects, especially if near the apex, pose a difficult operative problem.

Transcatheter closure

• The era of percutaneous VSD closure has evolved significantly since Lock et al. initial description of the procedure.

• Percutaneous VSD closure is now an acceptable alternative to surgical closure of VSDs with very high procedural success rates.

• The overall rate of residual shunting is quite small and decreases with time with the vast majority of residual shunts being trivial or small and not hemodynamically significant.

• Continued improvements in both the devices available as well as the technique of implantation are likely to result in decreases in complication rates and further improvements in procedural outcomes.

Conclusions

• It is one of the most common CHD.

• All cases of suspicion should be evaluated by cardiologist.

• Majority of VSD’s require only close follow up because of tendency to close spontaneously.

• Echocardiography remains the central and most important tool for evaluation.

• Large VSD’s should be effectively managed for heart failure and early surgery to be considered.

• Newer techniques and hardware are allowing more and more device closures with excellent success rates.