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:
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Position of the atrioventricular (AV) valves provides important information.
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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.
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The tricuspid valve usually has septal chordal-papillary attachments.
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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.
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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]).
