Ventricular Inversion 

Updated: Jan 28, 2021
Author: Ira H Gessner, MD; Chief Editor: Howard S Weber, MD, FSCAI 

Overview

Background

Before discussing the fascinating congenital heart defect of ventricular inversion, a definition of terms is essential, particularly in reference to the two ventricles. This article refers to right and left ventricles based on their specific anatomic characteristics and not on their spatial relationships (ie, on the right and left sides of the body).

The right ventricle is tubular, with its inflow portion separated from its outflow portion by the muscular crista supraventricularis (conus). Its ventricular septal surface is coarsely trabeculated; the inflow (ie, tricuspid) valve has three leaflets and associated papillary muscles, including a papillary muscle attached to the conus. The left ventricle is cone shaped with its inlet valve and outlet valve in continuity. Its ventricular septal surface is finely trabeculated; the inflow (ie, mitral) valve has two leaflets and two papillary muscles with no septal attachments. Therefore, a ventricle is named right or left only on the basis of its anatomy. The reader must keep this essential point in mind.

The atrioventricular (AV) valves derive embryologically, in significant part, from the wall of the ventricle into which they enter. An AV valve entering a right ventricle has the morphology of a tricuspid valve, and an AV valve entering a left ventricle has the morphology of a mitral valve. For the purposes of this article, transposition of the great arteries refers to their anteroposterior (AP) interrelationship. See the image below.

This right ventricular angiogram shows a patient w This right ventricular angiogram shows a patient with transposition of the great arteries. The aorta arises directly from the right-sided anterior right ventricle (10° left anterior oblique [LAO]).

The aorta lies anterior, and the pulmonary trunk lies posterior. This definition is neither comprehensive nor uniformly accepted. Similarly, the right and left atria can be identified solely on the basis of their anatomic characteristics. This article refers to these structures on this basis.

Definition

Ventricular inversion refers to a specific congenital heart defect in which the ventricles are exchanged in position so that the left atrium enters the right ventricle and the right atrium enters the left ventricle.

In regard to the person's body and in the absence of other abnormalities affecting chamber position, the left ventricle lies primarily to the right of the right ventricle. The term ventricular inversion includes understanding that the aorta arises from the right ventricular outflow tract in a position anterior to the pulmonary trunk that arises from the left ventricle (ie, the commonly accepted elementary definition of transposition of the great arteries).

As described below, a natural consequence of ventricular inversion results in the aorta arising from the right ventricular outflow tract anterior to the pulmonary trunk that arises from the left ventricle; in other words, the great arteries are transposed. Just as the term normal heart includes the pulmonary trunk anterior from the right ventricular outflow tract and the aorta posterior from the left ventricle, the term ventricular inversion includes an aorta anterior from the right ventricular outflow tract and a pulmonary trunk posterior from the left ventricle. Transposition of the great arteries is inherent in ventricular inversion and does not represent an additional abnormality.

Embryology

At the beginning of 4 weeks' gestation, the embryonic heart includes the primary heart tube that eventually forms the ventricles, their outflow tracts, and the proximal great arteries. This initially straight structure, fixed at its ends, grows more rapidly than the pericardial cavity in which it lies and, as a result, it must bend. This results in a C-shaped loop with the convexity directed anteriorly and rightward. It places the left side of systemic venous flow entering the heart tube in relation to the initial portion of the heart tube, the component that forms the left ventricle.

With division of the AV canal, the right side of the entering systemic venous flow (ie, right atrium) aligns with the second portion of the heart tube (ie, the portion that forms the right ventricle). Normal septation of the distal portion of the heart tube aligns the aorta with the left ventricle and the pulmonary trunk with the right ventricle. Critical to this process is bending of the heart tube to the right, so-called d-looping. This is not a random process. The precise definition of what controls d-looping remains obscure but is probably genetically determined.

Ventricular inversion results from bending of the heart tube to the left, so-called L-looping. If cardiac development otherwise proceeds in usual fashion, the right side of systemic venous inflow (ie, right atrium) aligns with the initial portion of the heart tube (ie, left ventricle). With division of the AV canal, the left atrium aligns with the second portion of the heart tube (ie, right ventricle).

The process of division of the distal portion of the primary heart tube (ie, truncus arteriosus) into the aorta and pulmonary trunk remains somewhat controversial, particularly in regard to the development of isolated, simple transposition of the great arteries. However, all agree that d-looping with subsequent normal cardiac development results in the pulmonary trunk arising from the right ventricle anteriorly to the aorta that arises from the left ventricle. Simple transposition of the great arteries in d-looping results in the aorta arising from the right ventricle anteriorly to the pulmonic trunk that arises from the left ventricle.

In L-looping, in the ordinary course of events, the aorta arises anteriorly from the right ventricle, and the pulmonary trunk arises posteriorly from the left ventricle. Although this condition satisfies the definition of transposition mentioned above and though it results in discordance of the normal ventricular-arterial relationship, septation of the truncus arteriosus in this manner appears to be normal in L-looping. In other words, otherwise normal development of the heart after L-looping includes transposition of the great arteries; therefore, it should not be considered an additional abnormality.

Anatomy

The anatomy of the atria in ventricular inversion remains normal. The right atrium enters the left ventricle through a mitral valve that is anatomically normal. Left ventricular internal anatomy is normal, and the mitral valve is in fibrous continuity with its outlet valve, the pulmonary valve. The pulmonary trunk is central and posterior in position. The left atrium enters the right ventricle through a tricuspid valve that almost always demonstrates at least minor anatomic abnormalities. The outflow area of the right ventricle (ie, infundibulum) leads to the aortic valve located at the left upper heart border. The anterior ascending aorta rises more or less straight toward the midline and then passes to the left of the trachea, branching normally.

Because of the abnormal relationship of the atria to the ventricles, the position of the AV node is abnormal (ie, above and to the left of its normal position). An accessory AV node may also be present. The bundle of His and the right and left bundle branches are inverted, a condition that substantially lengthens the main bundle.

The coronary arteries usually have normal morphology but are distributed and named in accordance with the ventricles. Therefore, the left coronary artery arises from right posterior sinus and the right coronary arises from the left posterior sinus.

Pathophysiology

In the absence of an additional heart defect the circulation in ventricular inversion is normal. Systemic venous blood passes from the right atrium to the left ventricle and then to the pulmonary arteries. Pulmonary venous blood enters the left atrium, passes into the right ventricle, and then enters the aorta. This physiology accounts for the terms congenitally corrected transposition and physiologically corrected transposition. However, these names emphasize transposition rather than ventricular inversion as the primary abnormality. Moreover, this distraction from the primary embryologic abnormality of looping makes understanding this defect more complex and more difficult than it otherwise is.

The heart with ventricular inversion may have no other clinically significant abnormality. Therefore, the individual's cardiac function remains normal. However, this situation is the exception, occurring in less than 1% of all persons with ventricular inversion. The vast majority of hearts with ventricular inversion have associated defects. Any cardiac defect that can occur in a normal d-looped heart can occur in the heart with ventricular inversion.

Some defects are more common than others. A ventricular septal defect (VSD) occurs in 80% of cases, and pulmonic stenosis, usually subvalvar, occurs in 50%. Anatomic abnormality of the tricuspid valve occurs in almost all cases although functional abnormality, usually tricuspid regurgitation, occurs in approximately one third. Some type of AV conduction abnormality is observed in one third of persons with ventricular inversion. Positional abnormalities of the ventricular mass, mesoversion, and dextroversion are encountered fairly often; in these cases, ensure that the patient does not have a heterotaxy syndrome such as asplenia or polysplenia because these conditions usually prevent accurate definition of left and right cardiac anatomy.[1]

The most rare and most interesting associated cardiac defect observed in ventricular inversion is that which causes the pulmonary artery to arise anteriorly from the right ventricle and the aorta posteriorly from the left ventricle. In other words, the great arteries are reversed from their expected position for the heart with ventricular inversion.

This condition causes systemic venous blood to travel from right atrium to the left ventricle and then to the aorta (ie, back to the systemic circulation); pulmonary venous blood enters the pulmonary artery returning to the lungs. Therefore, this situation is physiologically identical to simple transposition of the great arteries in D-looping. Some use the terms isolated ventricular inversion or ventricular inversion without transposition to describe these cases in which the pulmonary artery is anterior and the aorta posterior even though the physiology is that of simple transposition. One can make the argument that these hearts demonstrate two independent developmental abnormalities: ventricular inversion and transposition of the great arteries. In this case, the usual definition of transposition (ie, aorta anterior, pulmonary trunk posterior) does not apply.

If transposition is defined as pulmonary artery posterior and aorta anterior, an admittedly useful definition, the heart with ventricular inversion, anterior pulmonary artery, and posterior aorta cannot be labeled as demonstrating transposition, though the aorta and pulmonary artery are reversed in relation to their expected positions. Some authorities call this heart atrial-ventricular discordance with ventricular-arterial concordance, but this term tends to obscure the combination of defects that appears to be present. Given the controversies in the terminology, it is prudent and important to concentrate on understanding this interesting defect and not to dwell on the issue of naming it.

Natural history

The natural history of ventricular inversion depends on the associated heart defect, if any. Many defects are stable. On the contrary, regurgitation of the tricuspid (left-sided AV valve) tends to progress and may cause right ventricular dysfunction more rapidly than a similar degree of mitral regurgitation in a noninverted heart causes left ventricular dysfunction. Data from a substantial multicenter study suggest that individuals with ventricular inversion have a long-term risk of developing both right ventricular myocardial dysfunction and congestive heart failure that is not directly related to the degree of tricuspid valve regurgitation. Furthermore, other reports indicate that right ventricular coronary blood-flow reserve is decreased in the absence of ischemic symptoms.

Etiology

The cause of ventricular inversion is not known. In a single case-control study, 36 patients with ventricular inversion were compared with 3495 population-based live-born infant control subjects.[2] An increased incidence of this defect was associated with parental exposure to toxic chemicals from the air and from hazardous-waste sites.

Note the following:

  • The looping that occurs in the development of the embryonic heart tube is not a random event and must be under the same control as other developmental processes. The cause for l-looping remains unknown. The fact that other congenital heart defects occur in the vast majority of hearts that exhibit L-looping implies that the process predisposes individuals to additional abnormalities.

  • No familial factors have been determined.

  • No teratogenic factors have been identified with certainty. Data from a single study suggest that parental exposure to toxic chemicals increases the risk of ventricular inversion.[2]

  • See Pathophysiology for associated defects.

Epidemiology

United States data

Ventricular inversion accounts for approximately 0.5% of all congenital heart defects. Ventricular inversion occurs with VSD in 80% of cases and occurs with pulmonic stenosis (usually subvalvar) in 50%. Almost all patients have an associated anatomic abnormality of the tricuspid valve. Functional abnormality, usually tricuspid regurgitation, is present in approximately one third. Ventricular inversion is associated with some type of AV conduction abnormality in one third of patients. Associated positional abnormalities of the ventricular mass, mesoversion, and dextroversion are encountered fairly often. More complex defects (eg, single ventricle of the double-inlet left ventricle [DILV] type, often with coarctation of the aorta) also occur.

International data

As in the United States, ventricular inversion accounts for approximately 0.5% of all congenital heart defects.

Race-, sex-, and age-related demographics

No significant racial influences have been identified.

The prevalence is higher in males than in females, with a male-to-female ratio of approximately 2:1.

Ventricular inversion is a congenital abnormality and therefore is present at birth. It may be diagnosed in persons of any age, including young infants. The defect cannot be acquired. It most commonly comes to attention because of associated heart defects, including complete heart block. Ventricular inversion without an associated defect may escape detection indefinitely.

Ventricular inversion may be discovered on an ECG recorded during investigation of an innocent heart murmur. In rare cases, ventricular inversion is recognized on a plain posterior-anterior chest radiograph. Fetal echocardiography can identify ventricular inversion.

Patient Education

Patient restrictions regarding exercise and other lifestyle issues depend on the associated cardiac defect.

Instruct parents and older patients regarding the symptoms of cardiac conduction abnormality and specifically the symptoms of sudden-onset of Adams-Stokes syndrome, which can cause complete heart block.

When children with ventricular inversion reach maturity, they must be educated regarding the importance of the defect and of any associated abnormalities.

 

Presentation

History and Physical Examination

History

The history in patients with ventricular inversion reflects associated heart defects, including conduction abnormalities.

Most patients present in infancy with a clinically significant heart murmur.

Physical examination

Physical findings reflect the associated heart defect, if any, and its effects (eg, cyanosis, heart failure) on the patient.

The physical findings are not likely to suggest ventricular inversion if an associated defect is absent, though some subtle observations may provide a clue.

Anterior and leftward location of the ascending aorta may result in a palpable brisk systolic impulse in the second left intercostal space. Because the aorta is anterior, the aortic component of the second heart sound (S2) is louder than usual. Because the pulmonary artery is posterior, the pulmonic component of S2 is softer than usual.

Variation in the splitting interval of S2 occurs with respiration, but with a notable modification. The left ventricle is activated before the right ventricle as usual. In ventricular inversion this causes P2 to occur earlier than in a healthy, normal heart. This change is not enough to cause paradoxical splitting of S2, but it does substantially shorten the A2 -P2. interval. As a result of these phenomena, normal splitting and respiratory variation of S2 may not be detectable. Therefore, the only clue to the diagnosis of ventricular inversion may be a loud single S2 in the second left intercostal space without another reason for this finding.

 

DDx

Diagnostic Considerations

Important considerations

A potential problem is the failure of the primary care physician to identify an abnormal cardiac finding on physical examination of a patient with ventricular inversion who also has a clinically significant associated defect that creates observable findings.

Surgery or cardiac catheterization may raise medicolegal concerns, especially if the operator is inexperienced in caring for patients with complex congenital heart defects.

The patient's family and, if appropriate, the patient should be fully informed regarding the increased risks of evaluating and treating ventricular inversion.

Special concerns

Pregnancy can be accomplished successfully in many women who have ventricular inversion. Such patients should undergo careful evaluation by a cardiologist with expertise in both congenital heart disease and high-risk pregnancies. If right ventricular function is satisfactory, no significant tricuspid-valve regurgitation is present, and no major associated heart defects are present, the pregnancy can occur safely under careful guidance and management. The risk of the baby having congenital heart disease is approximately 5% provided that no close relatives of either parent have another congenital heart defect.

The presence of tricuspid regurgitation with any evidence of right ventricular dysfunction substantially increases the risk for the mother. Other associated factors can also include the risk of pregnancy risks in a patient with ventricular inversion.

Other problems to be considered

Identification of ventricular inversion is most difficult and, perhaps, most controversial in hearts with clinically significant positional abnormality. For example, when the cardiac mass is oriented primarily to a person's right, establishing that neither asplenia nor polysplenia are present is essential because these conditions, especially asplenia, prevent precise determination of left and right ventricular chambers.

In a heart with a rotational abnormality of the ventricular mass to the right (ie, dextroversion) the incidence of a congenital heart defect is high, and ventricular inversion is one of the most common types. Another rare and interesting anomaly is the corollary (ie, situs inversus with levoversion). In this situation, ventricular inversion frequently occurs.

The specific abnormality dictates the differential diagnosis of an associated congenital heart defect of any type.

 

Workup

Laboratory Studies

The type of heart defect associated with ventricular inversion and its effect on the patient indicate the laboratory studies. For example, infants in heart failure or those with a cyanotic lesion require the same laboratory evaluation as those indicated in case of a noninverted heart.

Imaging Studies

Chest radiography

In the absence of a clinically significant associated defect, a plain posteroanterior (PA) chest radiograph may still suggest ventricular inversion.

The shape of the heart differs from normal because of the straight left upper border caused by location of the ascending aorta in that position. Likewise, no evidence of a pulmonary trunk shadow is present.

The right pulmonary artery is more apparent than normal because it is positioned somewhat toward the right.

Chest radiographs otherwise reflect associated heart defects, if present.

Magnetic resonance imaging and magnetic resonance angiography

Magnetic resonance (MR) imaging can be used to identify ventricular inversion. This procedure usually provides less total information than echocardiography does, but it can provide important additional information, particularly in regard to associated defects.

The performance and interpretation of MR in this condition requires great expertise.

Electrocardiography

On occasion, ventricular inversion is discovered on an ECG recorded during investigation of an innocent heart murmur. In rare cases, ventricular inversion is recognized on a plain posterior-anterior chest radiograph.

The ECG can be highly valuable in making the specific diagnosis of ventricular inversion and in identifying the cardiac chamber alteration secondary to an associated defect. It also helps in identifying AV conduction abnormalities.

As in the normal heart, initial activation of the inverted ventricles occurs in the ventricular septum, beginning on the left ventricular surface and spreading toward the right ventricle. Therefore, the initial QRS deflection is directed leftward, posteriorly, and superiorly. This condition results in Q waves in leads II, III, and aVF; initial negativity in V1; and initial positivity in V6. The remainder of the QRS complex reflects the relative size of the two ventricles.

In the heart with ventricular inversion and no associated defect, the remaining QRS forces, after the initial septal depolarization described above, are directed leftward and mainly posteriorly, reflecting domination of right ventricular mass over left ventricular mass. This causes the QRS deflection in V1 to remain negative, inscribing a QS wave. In V6, a dominant R followed by a smaller terminal s wave can be observed. A T wave that is positive in all precordial leads is the expected finding in ventricular inversion, regardless of chamber enlargement.

After septal depolarization in the heart with ventricular inversion and substantial domination of the left ventricle, the QRS forces are directed rightward and anteriorly. This results in a qR pattern in V1 and an rS pattern in V6. Ventricular inversion and double-inlet left ventricle (DILV) is the extreme of this pattern.

After septal depolarization in the heart with ventricular inversion and substantial right ventricular hypertrophy, the QRS forces continue leftward and posteriorly, but they may terminate rightward and anteriorly. This may result in a Qr pattern in V1 and an RS pattern in V6.

Criteria for biventricular hypertrophy in the heart with ventricular inversion can be deduced from the aforementioned patterns and reflects the balance between the ventricles.

Criteria for atrial enlargement in the heart with ventricular inversion do not differ from those in the noninverted heart.

Echocardiography

The fetal echocardiogram is of primary importance in the diagnosis of ventricular inversion and associated heart defects.[3]

Ventricular anatomy can be identified by specific criteria for each, such as the following:

  • Position of the atrioventricular (AV) valves provides important information.

  • The tricuspid valve originates more inferiorly than the mitral valve. This may allow precise definition that the valve leading out of the left atrium is a tricuspid valve, whereas the valve leading out of the right atrium is a mitral valve; however, presence of a large ventricular septal defect (VSD) may obscure this observation.

  • The tricuspid valve usually has septal chordal-papillary attachments.

  • Identification of the right ventricle by the separation of its inlet and outlet valves and, conversely, identification of the left ventricle by the continuity of its 2 valves can be diagnostic

Identifying location and interrelationship of the great arteries establishes the presence of transposition.

Evaluate associated heart defects anatomically and hemodynamically in the same manner as they are evaluated in the noninverted heart.

Other Tests

Electrophysiologic studies in patients with ventricular inversion may be used to manage some abnormalities of AV conduction by applying transcatheter ablation techniques.

Holter monitor testing may be useful when standard electrocardiography indicates an AV block.

Additional tests and procedures are necessary only in evaluating other components of the patient's status, as indicated by a complete history and physical examination.

Procedures

The type of associated heart defect and the information required to manage it, particularly in regard to surgical assessment, dictates the need for cardiac catheterization.

Before cardiac catheterization is preformed in the patient with ventricular inversion, carefully plan the procedure to maximize information obtained and to minimize risks. For example, because of the location of the AV node, passage of a catheter through the left ventricle in attempt to reach the pulmonary artery incurs a clinically significant risk of causing complete and possibly permanent, heart block. Use of soft tip or balloon tip catheters may reduce this risk.

Ventricular angiograms should usually be obtained in straight anteroposterior (AP) and lateral projections because this is the best way to put the ventricular septum on edge.

The indications for interventional cardiac catheterization in these patients are fewer than they are in other patients. One clear indication is the newborn with ventricular inversion in whom the aorta arises from the left ventricle and the pulmonary artery from the right ventricle, thereby creating the physiology of simple transposition. Without an additional heart defect, this patient requires a mixing site; therefore, balloon atrial septostomy is indicated.

Postcatheterization precautions include those for hemorrhage, vascular disruption after balloon dilation, pain, nausea and vomiting, and arterial or venous obstruction from thrombosis or spasm.

Possible complications include rupture of blood vessel, tachyarrhythmias, bradyarrhythmias, and vascular occlusion.

 

Treatment

Medical Care

Management of heart defects associated with ventricular inversion dictates the requirement for inpatient care.

Pharmacologic therapy in ventricular inversion depends on the type of associated heart defect and its effects on the patient. Treatment of an infant with a cyanotic lesion or congestive heart failure does not differ from treatment of a patient without ventricular inversion.

Indications to observe precautions against bacterial endocarditis depend on the patient's operative status. For more information, see Antibiotic Prophylactic Regimens for Endocarditis.

Do not presume stability in patients without a clinically significant associated defect because almost all have at least minor degrees of tricuspid valve abnormality.

Patients with complete heart block may require a pacemaker.

Transcatheter therapy for associated defects is indicated less frequently in ventricular inversion than in analogous lesions in the noninverted heart.

Consultations

A pediatric cardiologist should evaluate the patient. If surgery is contemplated, a cardiovascular surgeon experienced in surgery of congenital heart defects should also examine the patient.

Transfer

Evaluation and treatment should occur at a center specializing in congenital heart disease.

Diet and activity

No special diet is required except as dictated by an associated defect.

The type of associated defect dictates activity restriction, if any.

Surgical Care

The surgical care of associated defects in patients with ventricular inversion includes careful assessment of the risks and benefits.[4, 5, 6, 7, 8]

Elective correction may not be recommended for some defects when they occur with ventricular inversion in contrast to the same defect in a patient without ventricular inversion.

The management of clinically significant subpulmonic stenosis in patients with a large ventricular septal defect and ventricular inversion often is difficult, with a high probability of complete heart block and of a clinically significant residual obstruction. Some patients with these conditions can be treated with a combination of atrial rerouting of venous return by using the Senning technique, redirection of left ventricular outflow through the ventricular septal defect (VSD) to the anterior aorta (analogous to the Rastelli operation), and placement of a conduit from the right ventricle to the pulmonary artery to bypass the pulmonic obstruction.

Closure of a large VSD is also difficult because of the location of the defect and the problems encountered in approaching it.

For some patients, particularly those with a large VSD but without clinically significant pulmonic stenosis, combining an atrial switch (ie, Senning operation) and an arterial switch (ie, Jatene operation) is now increasingly recommended. This procedure results in the left ventricle pumping pulmonary venous blood to the aorta and the right ventricle pumping systemic venous blood to the lungs. Several institutions report highly successful results with this double-switch procedure.[9] Indeed, some patients with right ventricular dysfunction due to tricuspid-valve regurgitation with no clinically significant additional abnormality have undergone successful double-switch surgery.[10]

A patient with right ventricular dysfunction, with or without significant tricuspid regurgitation, presents special problems. Tricuspid valve repair or replacement is more difficult to accomplish with good hemodynamic results. If left ventricle pressure is low, it may not tolerate the sudden requirement of systemic perfusion following the double switch procedure.[11] In such patients, preparation of the left ventricle has been successfully accomplished by first performing pulmonary artery banding. This may have detrimental effects on the left ventricle that appear many years later.

Ventricular inversion associated with an aorta arising from the left ventricle and an pulmonary artery arising from the right ventricle, thereby creating the physiology of simple transposition, can be managed by means of an atrial switch alone. This situation is one in which definitive surgery for ventricular inversion should be electively performed in the young infant.

Long-Term Monitoring

All patients with ventricular inversion, including those with no clinically significant associated defect, require regular follow-up by a pediatric cardiologist or an adult cardiologist who is thoroughly familiar with congenital heart disease. A permanent risk of developing complete heart block and uncertain long-term stability of both the tricuspid valve and right ventricle dictate this need.

Patients with even mild degrees of clinically apparent tricuspid valve regurgitation require follow-up at regular intervals, no longer than yearly, because this abnormality tends to be progressive.