bicuspid aortic valve is an autosomal dominant hereditary disease with incomplete penetrance and represents the most common congenital disease that can be found in the general population , with prevalence between 1% and 2% .
however , a threefold higher male predominance one was observed , suggesting that this disease may be related to an x - linked hereditary .
this structural alteration seems to be a consequence of an abnormal developmental process of the aortic cusps during embryogenesis [ 29 ] .
patients with bicuspid aortic valve have a higher morbidity and mortality owing to the associated cardiovascular complications .  
aortic coarctation , dilatation , and consequent aneurysm or dissections of the ascending aorta are very common in this group of patients .
aortic stenosis / insufficient valve is very common in these patients and it is related to gradual calcification of the valve . in these patients
a valve replacement is necessary and the surgical rational is similar to the valve replacement of the tricuspid one .
it is generally accepted that replacement of the ascending aorta should be performed , at the time of aortic valve replacement , when the aortic diameter exceeds 4045  mm ; however , it is still open to doubt which procedure should be performed and if it should be performed , especially in young patients .
in fact a dilatation of the ascending aorta could occur , even after the valve replacement , so the followup of the aorta in these patients is needed .  
echocardiography is considered the first standard examination for the diagnosis and the followup of this disease , especially if performed via transthoracic approach , with sensibility of 87% and specificity of 91% .
ecg - gated ct has been shown to provide accurate information about the aortic valve and root and may be considered as an alternative imaging technique [ 1113 ] . the aim of our study is to compare the results of the tee ( transthoracic echocardiography ) with the results obtained by the ecg - gated 64 slices ct during the followup of patients with bav , after aortic valve replacement ; in particular we evaluated the aortic root and the ascending aorta looking for a new algorithm in the followup of these patients .
from january 1999 to december 2009 , 369 patients with bicuspid aortic valve were submitted to surgical treatment by cardiac surgery division of tor vergata university foundation . in particular our attention
was focused on 67 patients with isolated surgical substitution of aortic valve ( 48 male , 19 female ; mild age of 61  15 , min age 21 , max age 88 ) , selected for clinical and instrumental preoperative and postoperative studies with echo - cardiac and mdct exams , on the bases of ascending aortic diameters < 45  mm at the moment of surgical treatment , absence of genetic disease ( e.g. , marfan syndrome ) , general ct exam contraindications , and also for geographical territory distribution .   preoperatory characteristics of this selected population of patients are shown in table 1 .
the study was approved by the local ethics committee and all the patients provided informed consent to the examination . an echo - cardiac transthoracic exam
( table 2 ) and mdct ( table 3 ) were performed before surgical treatment .
a preoperative coronary study was also performed by means of a conventional coronarographic study in 60 patients and a mdct in 7 patients .
all these patients underwent surgical implanted valves ; in particular , 30 of them received a biological prosthesis ( lifesciences edwards c - e perimount ) and 37 of them a mechanical prosthesis ( 24 sorin bicarbon , 12 carbomedics , 1 st.jude medical ) .
after dismissal , all of these patients were strictly observed with clinical exams , ecg , transthoracic echocardiography , and in selected cases with mdct .   during the period between may to september 2010 , these patients underwent their last evaluation , and clinical exams , ecg , transthoracic echocardiography and an ecg - gated - mdct were performed .
an echo - cardiac transthoracic exam was performed in order to measure the diameter of the aortic root , sinotubular junction , and ascending aorta .
a measurement of parietal thickness , telediastolic and telesystolic left ventricular diameter and left ventricular ejection fraction was also obtained . as regards the prosthesis aortic valve ,
we evaluated transvalvular maximum and medium gradients and the presence of reflux ; we also studied the other valves and systolic pulmonary arterial pressure .
mdct was also performed before surgical treatment to measure the aortic root diameter , sinotubular junction , and ascending aorta ( at the bifurcation of pulmonary trunk ) and proximal aortic arch .
cardiac frequency < 75  bpm was required for the execution of the examination ; in the case of higher frequency a beta blocker was administrated ( 5  mg propranolol ev . ) .
ct exams were performed with a 64-slice ct scanner ( lightspeed vct , general electric medical system , milwaukee , wi , usa ) , and by a retrospective synchronization technique .
a preliminary unenhanced scan was done in order to determine the scan extent and calculate the calcium score ( smartscore protocol ) . the acquisition stack extended from the pulmonary apex to the diaphragm
a second image stack was then acquired after intravenous administration of iodinated contrast material using a dual - head automated injector ( stellant , medrad , pittsburgh , pa , usa ) .
a dose of 90  ml of nonionic iodinated contrast material ( iomeron 400 , bracco , milan , italy ) was administered through an 18-gauge needle cannula placed in an antecubital vein , followed by a 40  ml saline solution injection , both at a rate of 5  ml / s . to synchronize the acquisition start with the arrival of the contrast agent in the aortic root
parameters for the contrast - enhanced scan were beam collimation 64  0.625  mm , slice thickness 0.625  mm , reconstruction increment 0.625  mm , table feed 2.9  mm / rotation , tube rotation 0.35  s , tube voltage 120  kv , dose modulation protocol ( intensity 140750  ma ) , and craniocaudal scan direction .
scan duration was 1012  s. image reconstruction was carried out using 75% of the cardiac cycle , corresponding to the r - r interval or end diastole .
the data - set was sent to a workstation console and elaborated using a dedicated software ( advantage windows with cardioiq software , version 4.4 ; ge healthcare , milwaukee , usa ) to get multiplanar reconstruction ( mpr ) , maximum intensity projection ( mip ) , and volume rendering ( vr ) images .
the data was expressed as means plus one standard deviation ( sd ) or as percentages .
the comparison between groups was obtained using the  test and the student 's t - test , as appropriate .
during the period between may to september 2010 , these patients underwent their last evaluation ; clinical exams , ecg , transthoracic echocardiography , and an ecg - gated - mdct were performed .
the average time of the followup was 55  35  months ( range 9137  months , median 44  months )
. 
 table 4 shows all the clinical characteristics of the population during the followup .
tte results show an aortic root of 36.7  4  mm and an ascending aorta of 39.6  4.8  mm ( table 5 ) .
ecg - gated ct shows an aortic root of 37.9  5.5  mm and an ascending aorta of 43.1  5.2 ( table 6 ) .
the comparison between preoperative and postoperative eet shows a significant long - term dilatation of the ascending aorta ( 37.5  4.4  mm versus 39.6  4.8  mm ; p < 0.0001 ) , while the aortic root diameter seems to be stable ( 36.4  4.1 versus 36.7  4.1  mm ; p < 0.0001 ) .
all the patients underwent ecg - gated ct and none of them were excluded during the examination .  
ecg - gated ct confirms the stability of the aortic root diameter ( 38.2  5.3  mm versus 37.9  5.5  mm ; < 0.0001 ) and the increasing diameter value of the ascending aorta ( 40.2  3.9  mm versus 43.1  5.2  mm ; p = 0.0156 ) .
in particular , we noticed that in 7 ( 10.4% ) patients , the diameter of the ascending aorta was 50  mm ( figure 1 ) . comparing this group of patients with the rest of the population we discovered that the only statistical difference was in the period of followup ; in fact these 7 patients have been observed for a period longer than 60  months .
ecg - gated ct acquisition allowed us an evaluation of the coronary tree in all patients : 43 ( 64.1% ) patients did not show coronary stenosis , while 21 ( 31.3% ) of them had a nonsignificant coronary stenosis ( < 50% ) and 3 ( 4.4% ) had a significant coronary stenosis ( 50% ) .
bicuspid aortic valve ( bav ) is the most common congenital cardiac malformation , affecting 1 - 2% of the population , with strong male predominance .
it has been recognized as a syndrome incorporating aortic valve disorders and aortic wall abnormalities .
these intrinsic defects in the aortic wall end up in late complications such as aortic root dilatation , ascending aortic aneurysm , often asymmetric , and dissection .    because these complications , with a potentially fatal outcome , will develop in approximately one third of all patients with a bicuspid aortic valve , it is of the utmost importance to correctly detect and treat this type of congenital malformation , and also to follow these possible complications over time .
for this reason , different surgical options have been developed for these patients , including not only aortic valve replacement but , in some cases , also concomitant prophylactic surgery of the aorta .
according to the guidelines of the american college of cardiology and of the american heart association , patients with bav should undergo elective repair of the aortic root or replacement of the ascending aorta , at the time of aortic valve replacement , if the diameter of these structures exceeds 45  mm .
in fact , the risk of combined surgery on the aortic valve and ascending aorta is almost comparable to the risk of isolated valve replacement , but it is considerably lower than the risk of a possible resurgery in election , or even worse , in emergency .   in case of only aortic valve replacement , a close followup is required after surgery , to evaluate aortic dilatation and to avoid late complications .
indeed , in patients with bav without dilatation of the ascending aorta , even successful valve replacement is not able to prevent long - term dilatation of the ascending aorta .
transthoracic echocardiography ( tte ) is the first standard examination during the followup of these patients .
currently , in patients with previous bav and aortic valve replacement , transthoracic echocardiographic followup is performed twice a year and it is integrated with angio - ct in the case of initial signs of aortic disease or of suspicious echocardiographic findings .
followup evaluation includes the state of the heart chambers , the functioning of prosthetic aortic valve , and the size of thoracic aorta .
tee is an excellent method for studying the aortic root , although this technique has some limitations : it is operator dependent and has a high incidence of artefacts in the evaluation of the upper ascending aorta .
the interposition of the trachea and left main bronchus between the aorta and the oesophagus can cause a 
the presence of severe aortic wall calcifications may lead to misdiagnosis because of the resulting  acoustic shadows  .
additionally , the examination may be undetermined by the lack of a suitable acoustic window due to body habitus and artefacts related to the presence of prostheses .
furthermore , the use of tte does not permit the visualization of the descending aorta .   
the introduction of the latest generation of 64-slice ct scanners with short acquisition times and their high spatial and temporal resolution allows images to be acquired during a single short breath - hold and thus with a high level of anatomical detail of the whole thoracic aorta and of the other anatomic thoracic structures .
furthermore , ecg - gated synchronization with its reconstruction algorithms permits a correct evaluation of cardiovascular structures minimizing cardiac motion artefacts ; the advantage of cardiac ct in these patients is that it allows a better visualization of the aortic root and aortic valve and that permits a simultaneous evaluation of the coronary arteries . a heart rate < 70  bpm , whether spontaneous or induced by -blockers , is considered sufficient to increase diastolic time and duration of end - diastole , when the heart , the valves , the aortic root , and coronary arteries are nearly motionless .
the volume of data acquired during scanning time can be subsequently reelaborated by a postprocessing procedure .
multiplanar reconstruction ( mpr ) , maximum intensity projection ( mip ) , and volume rendering ( vr ) techniques provide a comprehensive depiction of the prosthesis valve , the aortic root , the thoracic aorta , and coronary artery tree .
all this information is achieved with values of an absorbed dose of between 810  msv . however , when the heart rate is stable and lower than 65  bpm , a prospective ecg - gated ct protocol could be used with a significant reduction in the adsorbed dose , up to 35  msv , without decreasing the image quality .   in our study
we investigated the clinical applicability and image quality of retrospectively ecg - gated 64 slices ct for the followup of patients with aortic valve replacement due to bav , in comparison with transthoracic echocardiography .
in particular , our evaluation included thoracic aorta diameters at different levels : aortic root , sinotubular junction , ascending aorta , and aortic arch . in all patients
the study was also extended to the descending aorta and completed with an evaluation of the coronary artery tree .
we observed a statistically significant difference between ct and tte in the evaluation of ascending aorta diameters .
in particular , in 7 patients , the ascending aortic diameter measured by ct exceeded 50  mm , while echocardiographic measurements were lower .
these results disagree with those of other studies , in particular the study by tamborini et al .
moreover , it is important to notice that in these patients we observed the longest followup overall , 60  months .
this evidence underlines the progression of ascending aorta dilatation and also enhances the importance of long - term evaluation , with an accurate imaging technique , in patients with a prosthesis substitution of bav .
the most important issue emerging from our study is that ascending aorta shows a progressively long - term dilatation while aortic root 's diameters seem to be more stable .
probably , this happens because in patients with bav syndrome the defects of the valve had previously caused a hemodynamic stress of the ascending aorta wall associated with a congenital alteration of the structures of the aortic wall .
due to the different findings between ct and tte studies , angio - ct should no longer be considered as a complementary exam in the followup of these patients , but as a fundamental role since it is a real necessity .
we think that should be necessary to perform two angio - ct exams in followup , respectively 12  months and 48  months after aortic valve replacement . indeed ,
if between these observation times there are changes in the clinical history of the patient , it is important to perform also one more angio - ct study .
our study demonstrated that angio - ct is a compulsory diagnostic step , in the followup of patients with previous bav who have undergone aortic valve replacement , to avoid late complications .
the information provided by angio - ct regarding the thoracic aorta is more complete and exhaustive than that obtained by tte .
 the aim of our study was to compare the results of the tte ( transthoracic echocardiography ) with the results obtained by the ecg - gated 64 slices ct during the followup of patients with bicuspid aortic valve ( bav ) , after aortic valve replacement ; in particular we evaluated the aortic root and the ascending aorta looking for a new algorithm in the followup of these patients . from january 1999 
 to december 2009 our attention was focused on 67 patients with isolated surgical substitution of aortic valve ; after dismissal they were strictly observed . during the period between may and september 2010 , these patients underwent their last evaluation , and clinical exams , ecg , tte , and an ecg - gated - mdct were performed . at followup tte results showed an aortic root of 36.7  4  mm and an ascending aorta of 39.6  4.8  mm . 
 ecg- gated ct showed an aortic root of 37.9  5.5  mm and an ascending aorta of 43.1  5.2 . 
 the comparison between preoperative and postoperative tte shows a significant long - term dilatation of the ascending aorta while the aortic root diameter seems to be stable . 
 ecg - gated ct confirms the stability of the aortic root diameter ( 38.2  5.3  mm versus 37.9  5.5   mm ; < 0.0001 ) and the increasing diameter value of the ascending aorta ( 40.2  3.9  mm versus 43.1  5.2  mm ; p = 0.0156 ) . due to the different findings between ct and tte studies , ecg - gated ct should no longer be considered as a complementary exam in the followup of patients with bav , but as a fundamental role since it is a real necessity 
 . 