Risk factors for mbt shunt thrombosis
Authors: Muhammed S W , Azab S E , Elmidany A A H , Soliman A A 
Published: May 2020

Abstract

Background
The modified Blalock–Taussig shunt (MBTS) is the most commonly created systemic–pulmonary shunt in children with cyanotic heart disease, it continues to be a subject of academic interest, because of persistent risks associated with this simple-looking procedure. The purpose of this study was to determine the risk factors associated with the occurrence of thrombosis complicating modified blalock-taussig shunt.

Method
Clinical and perioperative variables were examined through prospective study of 45patients who had undergone MBTS construction in one-year period.

Results
male gender was predominant (33 cases) and females were 12 cases, mean age was 9.58 ±7.45months at the time of surgery. The most common cardiac anomaly was TOF (44.4%), mean duration of post-operative mechanical ventilation was 3.9±4.5 days, mean ICU stay was 5.9±4.5 days and the mean hospital stay was 10±5.4 days, shunt failure rate was 9/45(20%), the analysis revealed that shunt failure is significantly increased in patients aged 7 months at surgery (mean was7.1±6.8 months) (p-value 0.04),failure was more common if the pulmonary arterial diameter was4mm or less(p-value =0,06),shunt failure is significantly related to thoracotomy approach in which 6/45 (13.3%) have been subjected to this approach (p-value=0.02),shunt occlusion was significantly related to use of small shunt size 3.5mm encountered in6/45(13.3%), 4mm in 1/45(2.2%) and 5mm in2/45(4.4%) (p-value=0.02) ,failure rate was (15.55%)7/45 in patients who are deprived from heparin during operation while it was (4.4%)2/45 in heparinized patients (p-value=0.01), use of inotropes and nor-adrenalin are significantly related to shunt occlusion but on expense of poor hemodynamic state in which 6 patients out of 9 occluded shunt patients received inotropes while all occluded shunt cases received nor-adrenalin (p-value =0.02), we didn’t find any relation of other variables (sex, gender, pre-operative coagulation profile and low oxygen saturation) with development of post- operative shunt thrombosis (p-value&gt;0.05),The overall hospital mortality rate was 35.5% (16/45) The rate was significantly higher in patients aged below 10 months (mean 4.3±6.8 months)(p = 0.004),weighing 7kg or less(mean 5.3± 2.5kg) (p = 0.02),low oxygen saturation prior to operation was significantly related to post-operative mortality (mean 53.7±11.9%) while was (69.8 ± 14.5%) in discharged group (p = 0.002), all dead cases(16/16,100%) received nor adrenaline during and after operation that contributed to poor hemodynamic state while 12cases out 16 (75%) received inotropes due to the same reason, the mean Pulmonary artery size was (3.8±1.2mm) in dead cases and(4.3±1.4mm) in discharged cases(p &gt; 0.05), Shunt size was not related to mortality ,mean size was(3.9±0.4mm),( 4.1±0.5mm)in dead and discharged cases respectively(p &gt; 0.05),sternotomy approach was carried out on 29/45 patients9 (56.25%)cases are died and 20(68.96%) discharged while 16/45 underwent thoracotomy 7 of them died (15.55%)and 9(31.03%) discharged(p &gt; 0.05),mortality is encountered in non-heparinized (22/45)cases versus heparinized(23/45) during and after operation in which 10/16 (62.5%) didn’t receive heparin during and after operation while 6/16(37.5%) are heparinized , all patients later on turned to low dose oral aspirin Whether they heparinized or not.

Conclusion
It is important to assess risk factors associated with the MBTS operation. The results of our study suggest that MBTS thrombosis is associated with many risk factors includes age and presence of small shunt size, small pulmonary artery size, intra. and early post-operative anticoagulation can help to reduce the risk of shunt thrombosis, as well as thoracotomy surgical approach that influence shunt patency. Also, mortality is significantly associated with young age less than 5 months of age and low body weight around 5 kg and oxygen desaturation&lt;60% prior to operation.