**9. References**


the tube. The anterior portion of the heart shows a prominent specialization (the conical chamber, which is larger in size) and anastomoses into the aorta that runs from the posterior end of the thorax into the head capsule. Several pairs of alary muscles are attached to the heart tube, which are likely to help to maintain heart position. The pericardial cells are found alongside the heart and have a nephrocyte-like as well as other cardiac support functions. The ventral longitudinal layer consists of several multi-nucleated muscle cells that ensheath the heart from A1 to about mid-A5 (indicated as VLL in transverse section of the conical chamber).

Anatomical features: The conical chamber is the largest chamber of the adult fly heart

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(compare transverse sections 1+2). The VLL that ventrally and laterally covers the heart can be seen in transverse section 1. Myofibrillar structure: The cardiomyocytes of the conical chamber are much larger in size and have a higher acto-myosin content compared to other regions of the heart. The cardiomyocytes of the valves show a very dense packaging of myofibrils compared to regular cardiomyocytes of the heart. Cardiac physiology: High-speed image capturing from semi-dissected fly hearts allows determination of several parameters, which are indicative for fly heart morphology and function: the diameters of the heart during diastole (DD) and systole (SD) are determined from the original movies. M-modes are generated by aligning a 1-pixel wide strip from each frame showing the location of the heart walls (Y axis) over time (X-axis) (Ocorr et al., 2007). Heart rate, durations of diastoles and systoles (DI and SI) and rhythmicity are determined by semi-automated analysis using MATlab-based software

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**Part 3** 

**Individual Heart Defects** 


**Part 3** 

**Individual Heart Defects** 

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Tinman activity controls proper diversification and differentiation of myocardial cells

**7** 

*USA* 

**Congenitally Corrected** 

*Vanderbilt University* 

English C. Flack and Thomas P. Graham

**Transposition of the Great Arteries** 

Congenitally corrected transposition of the great arteries (ccTGA) is a rare defect combining atrioventricular discordance with ventriculoarterial discordance. The atria are connected to the opposite ventricle (left atrium to right ventricle via a tricuspid valve) and the ventricles are connected to the incorrect great artery (right ventricle to aorta). Thus oxygenated blood is circulated systemically by the morphologic right ventricle (RV) and deoxygenated blood returns to the right atrium to be pumped out the left ventricle (LV) to the lungs (Figure 1). The defect is therefore "corrected" because of the physiologic flow of blood through the body. For the purposes of this review, univentricular hearts, those with common

The most common anatomy of ccTGA is that of {S,L,L}, representing atrial and visceral situs solitus (right-sided inferior and superior vena cavae returning deoxygenated blood to a right sided atrium), L-looped ventricles (the morphologic LV with mitral valve positioned on the right), and L-transposed great arteries (aorta arising off the left-sided morphologic RV and therefore situated anterior and leftward of the pulmonary artery). The RV serves as the systemic ventricle and, in the absence of other defects, oxygen saturation is normal. The most common positions of the heart in the chest are levocardia (apex to the left) or mesocardia (midline). Patients with levo- or mesocardia and visceral situs inversus have a high likelihood of ccTGA and therefore must carefully by assessed for atrial, ventricular, and arterial concordance. Dextrocardia, in which the apex of the heart is to the right, occurs in approximately 20% of patients (Graham & Markham, 2010). In cases of dextrocardia with

The most common associated defects in ccTGA are ventricular septal defects (VSDs), which occur in 60-80% of cases, pulmonary stenosis (PS) in 30-50%, and tricuspid valve (TV) anomalies in 14-56%. The VSDs are usually large, perimembranous, and subpulmonary in location. Muscular inlet defects as well as multiple VSDs may also be seen. Pulmonary stenosis, more appropriately referred to as left ventricular outflow tract obstruction

atrioventricular (AV) valves and those with aortic atresia will not be discussed.

mirror-image anatomy the anatomic designation is {I,D,D}.

**1. Introduction** 

**2. Anatomy** 

**2.1 Associated defects** 
