the ductus arteriosus develops from the distal portion of the left sixth aortic arch and connects the main pulmonary trunk to the descending aorta . it runs in a posterior - anterior , inferior - superior , and leftward direction from the aorta to the pulmonary artery . patent ductus arteriosus ( pda ) is a common congenital heart defect , and the incidence of isolated pda in full - term infants is about 1 in 2000 , accounting for approximately 5% to 10% of all types of congenital heart disease . pda can be closed via such different modalities as video - assisted thoracoscopic surgery , conventional surgery with division and suture , and transcatheter closure by interventional catheterization . small pdas ( < 1 - 2 mm ) can be closed safely with cook detachable ( flipper ) coils or gianturco with minimal mortality and morbidity and excellent results . the amplatzer ductal occluder ( ado ) , which was introduced in 1997 , is recommended for pdas with sizes larger than 2 mm . an antegrade approach via venous line is required for the occlusion of pda using the ado . rates of complete closure are as high as 99.7% , as was confirmed during a long - term follow - up study . during the procedure , the device is pushed with a delivery cable until it reaches the tip of the delivery sheath in the descending aorta under fluoroscopy . the sheath is gently pulled to deploy the aortic disk , and the cable delivery sheath and device are subsequently pulled as one unit under lateral fluoroscopy until the retention disk is positioned at the ductal ampulla . at this stage by using fluoroscopy , the tracheal air column can be used as a landmark from the previous aortogram to position the device . also , a tugging sensation can be felt with the pulse of the aorta . by comparing the tracheal air column and the narrowest diameter of the pda from the diagnostic aortogram , the operator can retract the delivery sheath with only a slight tension on the cable and deploy the device . after the confirmation of the correct deployment of the ado by aortography , the device can be released by screwing the cable . some complications such as device embolization , narrowing of the aortic artery area , and left pulmonary stenosis have been previously described . one of the most critical complications of pda closure by ado is device embolization , frequently seen due to the undersizing of the ado or incorrect positioning of the ado in the pda . accordingly , having a practical landmark for the correct positioning of the device into the pda could reduce complications after device deployment . one of the best guides for the correct positioning of the ado is aortography after ado deployment in the descending aorta . be that as it may , in some procedures , there is no arterial line and aortography can not be performed until the ado is released . so the question remains as to when we can release the ado safely . in this article , we describe for the first time a sign that was extremely helpful during our use of the ado for the closure of pda . the study protocol was approved by the ethics committee of iran university of medical sciences . this retrospective study recruited all patients scheduled to undergo pda transcatheter closure between september 2009 and september 2012 in rajaie cardiovascular , medical and research center . the inclusion criteria were comprised of age < 15 years , body weight > 5 kg , conical pda , and narrowest size of the pulmonary end of the pda  2 mm in lateral view aortograms . the exclusion criteria consisted of other complex diseases requiring surgery , other pda shapes rendering it suitable for coiling , very small pdas , and near or systemic pulmonary hypertension . the clinical characteristics of the patients  including age , sex , and weight  were recorded . during cardiac catheterization , angiographic and catheterization data such as the size of the narrowest diameter of the pda and the type of the pda in lateral view aortograms , pulmonary artery pressure , and fluoroscopy time were obtained . the antegrade procedure via venous line under general anesthesia was recommended for all the patients . the course of the venous catheter was from the inferior vena cava to the right atrium , right ventricle , and pulmonary artery . after the estimation of the size of the pda via lateral view aortography , a device size at least 2 mm greater than the narrowest size of the pda at the pulmonary end was chosen . an appropriate sheath was positioned in the descending aorta , and the ado reached the tip of the delivery sheath by pushing the delivery cable . next , all of the sheath , delivery cable , and ado were pulled together in order to position the retention disk at the ductal ampulla . in some patients , there was no arterial line and the ado was positioned in the pda by pulling the sheath and tensing the cable . at this time in some of our patients , the continuity between the cable , sheath and ado was broken  signifying the correct deployment of the ado . echocardiography was done during the procedure before releasing the ado and the day after the procedure as well as one month and six months postprocedurally by using a ge vivid 3 echocardiographic machine . the patients were assessed for residual pda , left pulmonary artery stenosis , and descending aorta stenosis intraprocedurally via echocardiography . in the case of the presence of significant complications , two hundred thirty - seven patients underwent pda transcatheter closure between september 2009 and september 2012 . the study population comprised 130 female and 107 male patients . two patients had protrusion of the ado into the aortic artery but had no significant stenosis ; these patients did not have coarctation of the aorta on follow - up . in one of our patients , the ado protruded into the left pulmonary artery ; this artery had no obstruction on follow - up . transcatheter closure of pda is an established and safe method of treatment with no mortality and significant morbidity . in our study , transcatheter closure was performed in 237 patients under general anesthesia and the pda size ranged from 2.1 mm to 6.2 mm . there was no mortality , and there were minimal intraprocedural complications inasmuch as none of the patients had device embolization or vascular complications . the closure rate in our patients was greater than 99.7% , which is comparable to the rates reported in some other studies . two of our patients had ado protrusion into the aortic artery . on follow - up , however , there was no significant stenosis or other complications . if the ado protrudes into the descending aorta without significant coarctation of the aorta or if less than 50% of the aortic area is obstructed , long follow - up without other procedures is needed . as the patient grows older and this complication necessitates long follow - up periods , but this type of stenosis tends to diminish as the patient grows older . nonetheless , if left pulmonary stenosis leads to the reduction or obstruction of the left pulmonary artery flow , other alternative treatment modalities such as surgery and use of other devices should be taken into consideration . we herein introduce a sign , which can be useful for the correct deployment of the ado . figure 1 illustrates a normal conical pda in a lateral view aortogram . as is shown in figure 2 , during the procedure and before complete deployment ( i.e. when the device is pulled into the ductal ampulla ) , the device , delivery cable , and delivery sheath have continuity with each other in a curved line . the retention disk of the ado is placed in the ductal ampulla , and the other segments of the ado are positioned in the narrow segment of the pda . after pulling the cable delivery sheath and the device as one unit under lateral fluoroscopy , the delivery sheath is pulled into the pulmonary artery and the distal end of the ado is placed in the pulmonary artery at the narrowest part of the pda . when there is correct deployment , only the delivery sheath is pulled into the pulmonary artery and the continuity between the cable and the device is broken . this angulation is created by the angle between the pda and the pulmonary artery ( figure 3 ) . this figure shows an ado positioned in the pda with its retention disk placed in the ductal ampulla . the narrow segment of the device is also positioned in the junction between the pda and the pulmonary artery , and the distal end of the device is in the pulmonary artery . the continuity between the cable and the delivery sheath is broken by a sharp angle between the ado and the cable . during the procedure and before the release of the ado , echocardiography is performed to investigate the possible presence of coarctation of the aorta and left pulmonary artery stenosis . at this point in time , the operator knows that the ado is positioned in the correct site ( especially in the absence of an arterial line ) and he can release the ado safely . if the ado is positioned in other sites , the sign described herein can not be observed . in our study , more than 85% of the patients , who underwent pda closure by ado , had a positive sign , which denotes the reliability of this sign . the relatively small sample size and duration may be the major limitations of the present study . we herein introduced a new sign , which can assist in the correct deployment of the ado during pda closure . to our knowledge , the existing literature lacks signs similar to what we describe here . this sign , especially in the absence of an arterial line for post - pda aortography , can help the operator release the ado safely .
backgroundthe ductus arteriosus connects the main pulmonary trunk to the descending aorta . 
 the incidence of isolated patent ductus arteriosus ( pda ) in full - term infants is about 1 in 2000 . 
 the amplatzer ductal occluder ( ado ) is recommended for pdas with sizes larger than 2 mm . in this procedure , we must confirm the ado position in pda by aortogram from the arterial line . 
 the purpose of this study was to determine the optimal release time of the ado in the pda closure procedure , especially in the absence of an arterial line for post - pda aortography.methodsthis study recruited all patients scheduled to undergo pda transcatheter closure with the ado between september 2009 and september 2012 in our center . 
 age , weight , pda diameter , systolic and diastolic pulmonic pressures , fluoroscopy time , and total angiographic time were studied . 
 major complications such as mortality and vascular complications were considered.resultswe studied 237 patients in our investigation . 
 we had 130 female and 107 male patients at a mean age of 34.3  40.6 months and mean weight of 14.2 7.8 kg . 
 pda sizes ranged from 2.1 to 6.2 mm and its mean was 3.7  1.8 mm . 
 mean of fluoroscopy time was 11.4  9.7 min and mean of total angiographic time was 42.0  12.3 min . 
 there were no significant complications.conclusionwe herein describe a new sign , which proved extremely helpful during our pda closure procedures with the ado . by considering the angle between the ado and the cable during the procedure 
 , the operator can release the ado safely .