Indications for Left-to-Right Shunt Closure

How closure of ASD, VSD, PFO, and PDA may lead to prevention or improvement of symptoms.

By Sudeshna Banerjee, MD, and John M. Lasala, MD, PHD, FACC
 

Communications between the right- and leftsidedchambers of the heart result in left-torightshunting due to the relatively lowintracardiac pressures on the right side. Inatrial septal defects (ASDs), the volume load affectsthe right ventricle, leading to enlargement and elevatedpulmonary pressures. In ventricular septal defects(VSDs), as well as patent ductus, shunting leads to leftventricular overload.1 All of these defects can lead toincreased pulmonary flow resulting in severe or irreversiblepulmonary hypertension and, consequently,reversal of the shunt. The mechanism of the murmuris not due to the size of the communication but ratherto increased pulmonary flow.

The degree and direction of shunting are determinedby the compliance of the right and left ventricles.The right ventricle is initially more compliant andpredominately shunts flow left to right early in the diseaseprocess. As right ventricular volume overload andenlargement ensues, pulmonary pressures rise and theleft ventricular compliance exceeds the right-sidedcompliance, leading to right-to-left shunting. Theeffects of shunts include arrhythmias, endocarditis,right and left ventricular dysfunction, paradoxicalemboli, and pulmonary hypertension.2 Closure ofthese defects may lead to prevention or improvementof these conditions.

ASD
ASDs are the most common congenital cardiac malformation,accounting for 10% of those recognized at birthand 40% of anomalies in adults older than 40 years.3They are often asymptomatic in infancy and childhood,but when a significant shunt exists, dyspnea on exertionoccurs in 30% of patients by the third decade, and inmore than 75% of patients by the fifth decade of life.4Right ventricular volume overload leads to right ventricularenlargement and right atrial enlargement, which caneventually result in pulmonary hypertension and rightventricular failure. The degree of shunting may increasewith age as a result of increased systolic or diastolic dysfunction,affecting the left and right atrial pressuregradient.

Indications
Right atrial and right ventricular enlargement is a class Irecommendation for ASD closure, either surgically orpercutaneously due to the morbidity and mortality associatedwith elevated right-sided pressures and pulmonaryhypertension. Paradoxical embolism and documentedorthodeoxia-platypnea should also be considered for closure.In patients with left-to-right shunting, if the pulmonaryvascular resistance is less than two-thirds of thesystemic vascular resistance, closure may be contemplated.It is recommended that specific types of ASD, namelysinus venosus, coronary sinus, or primum ASDs, shouldbe closed surgically. Secundum ASDs, the most commontype, are due to defects in the fossa ovalis. Patients withsecundum ASD are candidates for percutaneous closuredue to their favorable anatomic location and characteristicswhen the defect is < 38 mm (size of the largestAmplatzer device, AGA Medical Corporation, Plymouth,MN) with appropriate margins (approximately 4 mm).The exception is the deficient anterior rim when the device can straddle the aorta.

Patients without left-to-right shunts or irreversible pulmonaryhypertension are contraindicated to undergoclosure.5 There have been reports, however, that treatmentwith pulmonary vasodilators may improve pulmonarypressures enough to allow successful ASD closure.6 If a bidirectional shunt is present, response to apulmonary vasodilator and test occlusion of ASDs shouldbe determined. If a favorable response (a decrease inmean pulmonary artery pressure with no decrease in cardiacoutput and no increase in right atrial pressure) isobtained, ASD closure may commence without reservation.If there is an unfavorable response, pulmonaryvasodilators may be initiated, with reassessment in 6months.7

Surgery Versus Percutaneous Closure
Surgical ASD closure has been practiced for more than50 years and has been shown to be safe and effective,improve survival, and prevent deterioration secondary toheart failure. It is, however, associated with increasedmorbidity related to sternotomy, cardiopulmonarybypass, and extended intensive care stay. The comparativesafety of percutaneous closure was demonstrated bySuchon et al, who showed zero mortality and similar lowperiprocedural complication rates and early outcomes ina cohort randomized to surgical versus percutaneous closure.4 The Amplatzer septal occluders (AGA MedicalCorporation) and the Gore Helex occluder (W. L. Gore &Associates, Flagstaff, AZ) (Figures 1 and 2) are availableand approved for use in the United States. AmplatzerFDA data have shown lower complications with a similarstatistical closure rate compared to surgery.8 The Helexdevice can currently close defects ≤ 16 mm, while theAmplatzer device has sizes up to 38 mm in the UnitedStates. Sizing and success of closure has been aided withthe development of test balloon occlusion.

Percutaneous closure leads to decreased right atrialsize and normalization of right and left ventricular volumesper MRI evaluation, which has not been establishedin postsurgical patients.9 Studies suggest a transcatheterapproach is superior to a surgical approachin terms of improvement in myocardial function.Surgical treatment does not lead to an improvementin myocardial performance index; this has been attributedto the effects of cardiopulmonary bypass.10Conversely, after percutaneous closure, right ventricularvolume reduction at 6 and 12 months, as well asimprovement in right and left ventricular function,results in a decrease in pulmonary artery pressure andimproved New York Heart Association functionalclass.11,12

Complications/Limitations
Surgical complications include infection, bleeding, andatrial arrhythmias. Fever, vomiting, or chest pain shouldraise suspicion for postpericardiotomy syndrome or tamponade.5 Percutaneous closure is associated with a lowrate of long-term complications; transient atrial arrhythmiashave been reported, but they are rarely clinically significant.13 Device erosion is rare (0.05%) and has beenreported with the Amplatzer ASD occluder in associationwith oversizing of the device, as seen in the setting ofdeficient rims.14 Although device erosion and migrationare uncommon, urgent evaluation is warranted shouldsymptoms occur or if a new effusion is seen on echocardiography.

VSD
Ventricular septal defects may be congenital or resultfrom myocardial infarction or trauma. In VSDs, complicatingacute myocardial infarction, the mortality is high with and without closure. Some studies have reported a2-month mortality rate as high as 90% in patients whodid not undergo closure.15

In congenital patients, VSDs usually spontaneouslyclose in childhood. In one series, up to 80% of VSDs seenat 1 month were closed at follow-up. In adults, spontaneousclosure occurs in only 10% of patients. Persistentdefects can lead to heart failure, arrhythmias, pulmonaryhypertension, endocarditis, and aortic valve regurgitation.16 The most common VSD is perimembranous, followedby muscular and, rarely, supracristal.17 At present,only muscular VSDs can be closed percutaneously,although a perimembranous device is being developed.The remainder should be closed surgically, if indicated.

Indications
The major indications for VSD closure in adults areleft-to-right shunt leading to right and left ventricularoverload, prevention of endocarditis, heart failure, andaortic regurgitation. Endocarditis is associated with a 10%mortality rate in patients with a congenital VSD.16Closure of a VSD is indicated when there is clinical evidenceof left ventricular volume overload or Qp/Qs (pulmonary-to-systemic blood flow ratio) of 2.0 or more. Ahistory of infective endocarditis is another class I indication.5 As recommended for ASD closure, if the pulmonaryvascular resistance is less than two-thirds of thesystemic vascular resistance, closure may be contemplated.Device closure should only be considered if the VSD isremote from the tricuspid valve and aorta (Figure 3).Patients with irreversible pulmonary hypertension arecontraindicated to undergo closure.5

Surgical Versus Percutaneous Closure
Surgical treatment is still the gold standard for VSDsresulting from myocardial infarction; the mortality can vary from 20% to 80%.17 Surgeons often recommend adelay consisting of days to weeks to allow for formation ofnecrotic tissue, which provides a better anchor for closure.Postsurgical shunts are not uncommon and may lead toreintervention.15 Surgical closure does not improve intracardiacdimensions.16 Thiele et al observed the outcomesof a group of patients undergoing immediate primarytranscatheter closure of postinfarct VSDs. The benefits ofpercutaneous closure over surgical closure included earliertreatment time, decreased mortality, and the ability toclose inferior defects. Long-term follow-up of thesepatients revealed a mortality rate of 37% at 730 days.17Percutaneous closure is feasible in postsurgical and posttraumaticpatients. In patients with congenital muscularVSDs, the mortality and complication rates associatedwith percutaneous closure are very low.16 To date, a perimembranousclosure device has not been approved.

Complications/Limitations
Surgery remains the traditional treatment but hasincreased morbidity and mortality resulting from scarringand sternotomy. Complete heart block is the maincomplication.18

Percutaneous closure involves a rigid sheath that mayenlarge the VSD or cause rupture, with resultant dislocationinto the right ventricle. Another limitation issmall device sizes that are not adequate for large VSDs.Late embolization or dislocation has been describedafter percutaneous closure due to late healing andenlargement of the defect.17 The rates of completeheart block are similar to surgical closure and have leadto pacemaker placement and, rarely, closure deviceremoval with referral to surgery.18 Infection and arrhythmiasare reported but are less common.17 To date, theAmplatzer postmyocardial infarction device is availableonly for compassionate use.

PDA
The ductus arteriosus connects the main pulmonaryartery to the descending aorta. It normally closes spontaneouslywithin 24 to 48 hours after birth. The incidence is5% to 10% of congenital cardiac malformations and thedefect is two times more common in female patients.19Untreated mortality in adults is approximately 1.8% peryear.20 Cardiac catheterization provides important hemodynamicinformation, including pulmonary vascularresistance and degree of shunting.20

Ten percent of congenital heart disease patients havethe diagnosis of patent ductus arteriosus (PDA).19 PDAcommonly escapes diagnosis until adulthood when it isusually found incidentally by auscultation of a murmuror as an incidental finding on transthoracic echocardiography.Asymptomatic patients may have silent pulmonaryhypertension and left ventricular dysfunction.21

Indications
Endocarditis is responsible for almost 50% of deaths inpatients with untreated PDA; patients with a history ofendarteritis are strongly recommended to undergo surgicalor percutaneous closure. Left atrial or left ventricularenlargement indicating left ventricular volume overload is aclass I indication.20 Other class I recommendations includepulmonary arterial hypertension or the presence of left-torightshunting.22 If the PDA is calcified, is too large fordevice closure, or has distorted anatomy, surgical closure isrecommended.22 Asymptomatic patients with a PDA arealso candidates for closure with a transcatheter device. Aswith ASD and VSD, irreversible pulmonary hypertensionwith net right-to-left shunt is a contraindication for closure.

Surgery Versus Percutaneous Closure
Surgical closure has been the conventional treatmentand has a negligible mortality rate but an increased morbidityrate.19 Percutaneous closure was first described in1998;23 since that time there have been many new generationsof devices, including improved sheaths and sizes.The Amplatzer PDA occluder (AGA Medical Corporation)(Figure 4) can close defects 4 to 12 mm in size, but smallerresidual defects can be occluded with coils. New advanceshave also provided allowance of confirmation beforedevice release.21 Temporary test occlusion with a ballooncatheter can help with sizing and predict the degree ofsuccess.20 Percutaneous transcatheter closure is a safe alternativeto surgery. It decreases endocarditis, arrhythmias,and development of pulmonary hypertension.

Complications/Limitations
Complications and limitations include residual left toright shunt, incomplete closure, hemolysis, distalembolization, and endocarditis.21

PFO
Patent foramen ovale (PFO) has an overall prevalenceof 27%, as described in one autopsy series. The interatrialtunnel usually fuses within 2 years. In one series, it wasfound to be patent in 35% of children. Cryptogenicstroke is defined as an ischemic cerebrovascular episodein the absence of identifiable cause. This accounts for30% to 40% of patients affected who are younger than 55years.24 PFO is more prevalent in patients with cryptogenicstroke than in patients with known cause of stroke(20% vs 40%–50%).24

Indications
Factors suggesting need for PFO closure includeyounger patients (younger than 50 years), no other causesfor stroke, large PFO, coexisting atrial fibrillation, recurrentevents, failure of anticoagulation to prevent recurrence,intolerance of anticoagulation, and a history ofpulmonary embolism or deep vein thrombosis.25

In cryptogenic stroke, conventional therapy is anticoagulationand/or antiplatelet medications. There havenot been any studies that substantially show one of thesetreatments to be superior to the other. Twenty-five percentof these patients have repeat recurrences of cerebralvascular accident (CVA) or transient ischemic attack in 4years despite medical treatment.24 Thus, medical therapyhas not been shown to prevent recurrence but has beenassociated with increased risk of bleeding.13 Surgical closureincreases morbidity, usually manifested as atrial fibrillation,infection, bleeding and tamponade. PercutaneousPFO closure secondary to cryptogenic stroke has a success rate of 86% to 100%, with a recurrent stroke rate of 0% to4.9%. Percutaneous closure is superior to conservativetreatment in patients who achieve complete closure orhave more than one stroke.13 Mas et al have shown thatthe recurrence rate of stroke was increased in patientswith an atrial septal aneurysm that coexisted with a PFO,leading some physicians to perform closure in the settingof atrial septal aneurysm.13

Migraines are not currently an indication for PFO closure.The MIST trial examined this indication but the primaryendpoint was not reached.26 Of note, these patientshad no history of transient ischemic attack or CVA. Inregistry data of patients with a history of transientischemic attack/CVA plus migraine, 50% to 70% ofpatients had a reduction or elimination of their migraine.This population still has to be studied. There are insufficientdata to make a recommendation about PFO closurein patients with a first stroke and a PFO. PFO closuremay be considered for patients with recurrent cryptogenicstroke despite medical therapy.22

Complications/Limitations
Surgical treatment leads to decreased recurrence oftransient ischemic attacks and CVA, but increasedmorbidity due to atrial fibrillation, bleeding, infection,and tamponade.26 Rates of atrial fibrillation are verylow (< 2.5%), and arrhythmia is usually transient.Hazards of PFO closure include thrombus formationon the device (incidence of 2%), seen mostly with theCardioSeal device (NMT Medical, Boston, MA), as wellas embolization and erosion, which are very rare.25

CONCLUSION
Cardiac shunts are associated with heart failure, pulmonaryhypertension, infection, and arrhythmias.Closure of these lesions may prevent or reverse thesecomplications. Surgical closure is safe and well-validated.Percutaneous closure devices have comparable safety andefficacy in specific situations and may be associated withless morbidity due to a less invasive procedure. Surgicalclosure has been the conventional management for manyyears, but with the advent of percutaneous devices andcontinued advances in technology, percutaneous closureof cardiac shunts may become more prevalent.

Sudeshna Banerjee, MD, is a fellow in interventional cardiologyat the Barnes-Jewish Hospital, WashingtonUniversity School of Medicine in St. Louis, Missouri. She hasdisclosed that she holds no financial interest in any productor manufacturer mentioned herein.

John M. Lasala, MD, PhD, FACC, is Professor of Medicineand Medical Director, Cardiac Catheterization Laboratory at the Barnes-Jewish Hospital, Washington UniversitySchool of Medicine in St. Louis, Missouri. Financial interestdisclosure information was not available at the time of publication.Dr. Lasala may be reached atjlasala@dom.wustl.edu.

 

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Cardiac Interventions Today is a publication dedicated to providing comprehensive coverage of the latest developments in technology, techniques, clinical studies, and regulatory and reimbursement issues in the field of coronary and cardiac interventions. Cardiac Interventions Today premiered in March 2007, with its launch issue focusing on the state of coronary drug-eluting stent use. Each edition will cover a variety of topics in a flexible format that includes articles covering various perspectives on current clinical topics, in-depth interviews with expert physicians, overviews of available technologies, industry news, and insights into the issues affecting today's cardiology practices.

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