Criss-cross heart or ‘upstairs–downstairs’ heart.
Review by S.Gerboni

Lev and Rowlatt in 1961 described unusual arrangement of the cardiac inlets : ventricular chambers arranged in a superoinferior fashion, with the RV superiorly and the LV inferiorly located. The term Criss-cross heart,was introduced by Anderson et al. in 1974, defined as crossing of the long axes of the AV valves. Criss-cross heart is a rare abnormality,its frequency is no more than eight per 1 000 000 and it accounts for <0.1% of congenital heart defects. The morphological spectrum of hearts with crossed AV relationships includes a wide variety of segmental arrangements. Usually, the venoatrial connections are normal, and the AV connections are either concordant or discordant (biventricular). The ventricular chambers are arranged characteristically in a superoinferior fashion, with the RV superiorly and the LV inferiorly located. Most commonly the VA connection is DORV and less often discordant. Associated anomalies include RV hypoplasia, straddling and/or overriding of the AV valves, and subaortic or subpulmonary stenosis. Rarely, criss-cross hearts have been described with an intact ventricular septum. Postnatal presentation varies and may include cyanosis, heart failure or a murmur, depending on the full sequential diagnosis and associated abnormalities. The diagnosis can be established by echocardiography, angiocardiography and magnetic resonance imaging.

Key points

• It appears to be an isolated cardiac finding with no associated extracardiac or chromosomal abnormalities.
• usually have biventricular AV connections.
• criss-cross relationship with doubleinlet ventricles is rarely recognized.
• the diagnosis should be suspected when the parallel arrangement of the AV valves and ventricular inlets cannot be achieved, and the two valves are not easily visualized simultaneously.
• the clue to diagnosis is the inability to image flow across the two AV valves in the same plane or in the straight transverse cut through the fetal chest owing to the unusual superoinferior relationship of the ventricles, also called the ‘upstairs–downstairs’ arrangement.
• to image the two valves and ventricles, the transducer must be tilted and a careful ‘sweep’ (posteroinferior to anterosuperior) allows the operator to appreciate this rare spatial relationship of the AV valves, with axes of openings that are not in parallel, but across one another. Their imaging requires different ultrasound planes in order to demonstrate the twisted AV inflow tracts.
• if this spatial arrangement of the inlets is not appreciated during live scanning, the echocardiographic views may be misinterpreted, leading to an incorrect sequential diagnosis.
• color flow mapping can help in assessing the AV connection as this allows visualization of the relative direction of intracardiac blood flows and facilitates recognition of the crossover of the inflow streams.
• Surgical options vary according to the exact sequential segmental analysis and associated abnormalities. In general, however, a univentricular repair is required, owing to significant AV valve straddling, even with two good size ventricles.
• This is very important in prenatal counceling.

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