Criss-Cross Heart

Definition and General Features: 

Criss-cross heart is a rare and complex congenital cardiac malformation characterized by a twisted atrioventricular (AV) connection, leading to a crossed orientation of the inflow axes of the ventricles. Also referred to as twisted atrioventricular connection, superior-inferior ventricles, or upstairs-downstairs ventricles, this condition results in a spatial arrangement where one ventricle lies superiorly (usually the right) and the other inferiorly (usually the left), with the ventricular septum often oriented horizontally. Despite the presence of two ventricular chambers, this configuration frequently presents with functionally single ventricle physiology.

Anatomy and Morphology: 

The hallmark of criss-cross heart is the significant twisting of the AV junction, either clockwise or counter-clockwise, resulting in the inflow axes of the AV valves crossing each other at angles up to 150 degrees, compared to the normal parallel alignment. The right ventricle (RV) is typically superior to the left ventricle (LV), contributing to the horizontal orientation of the ventricular septum. A large ventricular septal defect (VSD), often perimembranous with inlet extension, is commonly present. Straddling of the AV valves, particularly the tricuspid valve, is a frequent finding. The tricuspid valve may be hypoplastic due to its constrained position between the atrial and ventricular septa. The mitral valve is usually of normal or enlarged size. In some variants, the mitral valve may straddle into the right ventricular infundibulum, leading to infundibular enlargement and sinus hypoplasia. The ventriculo-arterial (VA) connections in criss-cross hearts are variable, with double outlet right ventricle (DORV) being the most common. Other arrangements include complete transposition of the great arteries (TGA), double discordance - "congenitally corrected TGA (ccTGA)", or occasionally a normal VA connection. The course of the left anterior descending (LAD) coronary artery, typically demarcating the RV-LV boundary, may also appear distorted.

Etiology and Development: 

The underlying causes of criss-cross heart remain unclear, though most cases appear sporadic. The anomaly is believed to result from abnormal ventricular rotation relative to fixed atrial and outflow positions during cardiac looping. This malrotation can alter AV and VA alignments and elongate inflow and outflow tracts.

Classification: 

Criss-cross hearts are classified based on the direction of the AV twist (clockwise vs. counter-clockwise) and the associated VA connections. This classification is applicable even in cases with situs inversus or heterotaxy.

Associated Anomalies: 

Criss-cross hearts are frequently associated with additional structural defects, including large VSDs, AV valve straddling, DORV, TGA, hypoplastic RV, left ventricular diverticulum, and features of heterotaxy syndromes. The presence of these anomalies often complicates the hemodynamics and surgical approach.

Diagnosis: 

Diagnosis relies primarily on echocardiography, which can visualize the crossed AV valve inflow axes and abnormal septal orientations. Advanced imaging modalities, such as cardiac MRI and 3D CT, are valuable for detailed anatomical assessment. Angiocardiography may also aid in complex cases.

Management and Surgical Considerations: 

Surgical planning depends on the degree of AV twisting, presence of AV valve straddling, and adequacy of both ventricles. In most cases, biventricular repair is not feasible due to anatomical complexity. If the ventricles are well formed and AV valve alignment is favorable, biventricular repair may be considered. Otherwise, a Fontan-type palliation is the preferred approach for managing functionally univentricular physiology. Specific scenarios, such as criss-cross heart with TGA and VSD, may be addressed through tailored palliative approaches.

Prognosis: 

Long-term outcomes vary and are closely tied to the complexity of associated defects and the type of surgical repair performed. Ongoing cardiology follow-up is essential due to the risk of residual lesions and evolving hemodynamics over time.

Example 1

Atrial situs solitus. Criss-cross heart with twisted atrioventricular connections. The right atrium connects to a superior right ventricle. The left atrium connects to an inferior left ventricle. Secundum atrial septal defect (ASD). Large inlet ventricular septal defect without a common atrioventricular junction. Non-apex forming right ventricle. Double outlet right ventricle, with pulmonary atresia. Aortic orifice anterior left with respect to pulmonary orifice. 

Example 2

Atrial situs solitus. Normal atrial arrangement (situs), atrioventricular and ventriculo-arterial connections. Criss-cross heart. The systemic veins drain to the right atrium (on the right), that is connected to a superior morphological right ventricle. The pulmonary veins drain to the left atrium (on the left), that is connected to an inferior morphological left ventricle (dominant). Patent foramen ovale (PFO) shunting left to right. Ventricular imbalance, the left ventricle being larger than the right. Moderate perimembranous central ventricular septal defect (VSD) with extension to right ventricular inlet (posterior). Aortic orifice posterior right with respect to pulmonary orifice. Outflow tracts seem parallel in some views but the great arteries have normal spiraling course. No annular hypoplasia of the tricuspid valve. Apex forming tripartite right ventricle.