الفهرس 
The relevant radiological anatomyOnly 14 pages are availabe for public view
 |  | from | 165 |  |  |
| | | from | 165 | | |
Abstract
Incidence of transposition of great arteries (TGA) is 1 per 3300 live birth according to the center of disease control and prevention.
TGA is subdivided into 2 types; dextro-transposition of great arteries (d-TGA) which is the most common type with an atrio-ventricular concordance and ventriculo- arterial discordance, the other type is levo-transposition of great arteries (l-TGA) with atrio-ventricular and ventriculo-arterial discordance, l-TGA is also known as congenitally corrected transposition of great arteries (cc-TGA).
Atrial switch is one of the surgical procedures done for d-TGA by redirecting the deoxygenated blood into the left ventricle which pumps blood into pulmonary artery and redirecting the oxygenated blood through pulmonary baffle to the right ventricle which acts as a systemic ventricle pumping oxygenated blood into the aorta. This procedure is indicated when there is no chance to proceed for arterial switch as the left ventricle is not conditioned to act as a systemic ventricle. Survival is 68% after 39 years while survival free of events like arrhythmias, heart failure and reoperation is 19% only after 39 years.
These figures raise questions about the underlying mechanisms of atrial switch complications on the long run, diffuse myocardial fibrosis is considered as a prominent problem. Underlying etiology of diffuse systemic ventricle fibrosis is an area of further researches helping to clarify the risk factors which could be the late atrial switch palliation sparing more time for deoxygenated blood to harm the myocardium or the hemodynamic burden on the systemic right ventricle in addition to the exposure to major cardiac surgery with decreased oxygen saturation.
Despite being congenitally corrected since birth by having similar circulation as atrial switch patients with right ventricle acting as a systemic ventricle pumping oxygenated blood to aorta, ccTGA patients have high incidence of systemic ventricle failure (up to 34% in case of absent associated other cardiac anomalies and 70% if other anomalies present) and premature death even without associated cardiac anomalies. This encourages the idea of anatomical repair by doing atrial and arterial switch in the same patient.
Still the gap of knowledge about the different performance of the systemic ventricle in atrial switch and ccTGA patients, is there an effect of the low oxygen saturation before and at the time of surgery in case of atrial switch? which could be the leading point in diffuse myocardial fibrosis in this cohort. What is the effect of the hemodynamic burden on the systemic right ventricle? Is the idea of anatomical repair a wise idea or it leads to more complications (complications of 2 different surgeries together in the same patient)?
Thanks for the advances in cardiac MRI techniques as we can calculate the myocardial fibrosis in a non-invasive manner by combination of T1 mapping and late gadolinium enhancement images, these techniques give an accurate idea about replacement and interstitial myocardial fibrosis. These data will help us to answer the question about systemic ventricle reaction in atrial switch and ccTGA.
Sixteen patients with previous atrial switch procedure (Mustard surgery) for TGA and twelve patients with congenitally corrected transposition of great arteries followed up in the congenital heart diseases and grown up adults with congenital heart diseases clinics at our Institution, they were prospectively recruited between August 2017 and August 2018 after approval of the ethical committee and after a given written informed consent.
We compared patients with atrial switch and ccTGA with saturation above 90% to determine the effect of mechanical stress in both groups and the additional decreased oxygen and open-heart surgery stresses in atrial switch patients.
All patients underwent cardiac MRI and serum brain natriuretic peptide (NT-proBNP) as a marker for heart failure severity.
16 Mustard patients, 12 males and 4 females, mean age was 39.25 months, mean age at time of surgery was 31.75 months. We calculated Pro-BNP for 13 patients only. 2 patients had no preoperative CMR.
12 cc-TGA patients, 3 males and 9 females, mean age was 17.08 years. Oxygen saturation above 90%. We calculated Pro-BNP for 10 patients only.
Interstitial fibrosis; extra-cellular volume (ECV) and native T1 parameters were calculated in 17-segment model of the left ventricle and 9-segment model of the right ventricle.
Interstitial fibrosis parameters (ECV and native T1) were not correlated with the decreased oxygen saturation before surgery or at time of surgery in TGA patients. They were not correlated the systolic ventricular dysfunction or the dilated systemic right ventricle. This raises the possibility that interstitial fibrosis is an independent marker for the mechanical stress of the systemic right ventricle that appears earlier before deterioration of the ventricular function.
Interstitial fibrosis increases in both ventricles which confirms that it is a problem for the left ventricle to be deprived from its high aortic pressure as the pressure load problem effect in the systemic right ventricle.
No systemic right ventricle territorial predilection in both interstitial fibrosis parameters in Mustard and cc TGA groups. This is against the theory of increased systemic right ventricle dysfunction as a result of its limited blood supply in comparison to the left ventricle.
Our study is limited in the size of cohorts, cc-TGA patients with saturation above 90% are presented late to health care systems. We had no comparable age range in both cohorts. We need also longer follow up period to validate our findings.
The other limit in our study is the lack of consensus of the normal age-related range of T1 mapping parameters (native T1 and ECV).