You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
coronary artery disease ( cad ) is the emerging cause of morbidity and mortality in developing world .
it provides an excellent resolution for visualization of the coronary arteries for catheter - based or operating interventions .
although the association of this technique with major complications such as mortality is highly uncommon , it is frequently associated with various cardiac and noncardiac complications . computed tomography ( ct ) coronary angiography is a promising technique for the evaluation of cad noninvasively .
it assesses disease within the coronary artery and provides qualitative and quantitative information about nonobstructive atherosclerotic plaque burden within the vessel wall .
thus , ct angiography - based disease evaluation may provide clinically more significant information than conventional angiography . the introduction of multi - slice computed tomography ( msct ) technology such as 64-slice , 128-slice , 256-slice , and now 320-slice msct has produced a high diagnostic accuracy of ct coronary angiography .
it has consistently showed to have a very high negative predictive value ( well above 90% ) in ruling out patients with significant cad defined as coronary luminal stenosis of > 50% .
the american college of cardiology / american heart association recommends that coronary angiography should be performed before valve surgery in men aged > 40 years , women aged > 35 years with coronary risk factors and in postmenopausal women .
the prevalence of cad in patients undergoing valve replacement is 2040% in developed countries . in the previous studies ,
the incidence of angiographically proven cad in acquired valvular diseases has been shown to vary widely from 9% to 41% . in aortic stenosis ,
we aimed to report the diagnostic performance of 128-slice ct coronary angiography in 50 patients undergoing for major noncoronary cardiac surgery referred for diagnostic invasive coronary angiography to assess the extent and severity of coronary stenosis .
during january 2013 to december 2014 , we enrolled fifty major noncoronary cardiac surgery patients scheduled for invasive coronary angiography who fulfilled the following inclusion criteria of age 40 years , having low or intermediate probability of cad , left ventricular ejection fraction ( lvef ) > 35% , and patient giving informed consent for undergoing msct and conventional coronary angiography .
those having any contraindication for contrast injection , lvef < 35% , high pretest probability of cad , and hemodynamic instability were excluded from the study .
patients with heart rates of > 70 bpm received ( unless they had known overt heart failure or electrocardiogram ( ecg ) atrioventricular conduction abnormalities ) a single oral dose of 100 mg metoprolol 45 min before the scan .
patients with heart rates of > 80 bpm received an additional oral dose of metoprolol if not contraindicated .
all patients were scanned with a 128-slice ct scanner ( siemens , somatom definition as ) equipped with a new feature in msct technology , so - called z - axis flying - focus technology .
the central 32 detector rows acquire 0.6-mm slices , and the flying - focus spot switches back and forth between 2 z positions between each reading .
two slices per detector row are acquired , which results in a higher oversampling rate in the z - axis , thereby reducing artifacts related to the spiral acquisition and improving spatial resolution down to 0.4 mm .
a bolus of 6580 ml contrast material ( omnipaque ) was injected through an arm vein at a flow rate of 5 ml / s .
a bolus tracking technique was used to synchronize the arrival of contrast in the coronary arteries with the initiation of the scan . to monitor the arrival of contrast material ,
axial scans were obtained at the level of the ascending aorta with a delay of 10 s after the start of the contrast injection .
the scan was automatically started when a threshold of 150 hounsfield units was reached in a region of interest positioned in the ascending aorta .
images were reconstructed with ecg gating to obtain optimal , motion - free image quality .
all scans were performed within 2 weeks of the msct coronary diagnostic angiogram . a single observer unaware of the multi - slice ct results identified coronary lesion as a single vessel , double vessel , or triple vessel disease .
all lesion , regardless of size , were included for comparison with ct coronary angiography .
lesions were classified as having nonsignificant disease ( luminal irregularities or < 50% stenosis ) or as having significant stenosis .
stenosis was evaluated in two orthogonal views and classified as significant if the mean lumen diameter reduction was 50% using a validated quantitative coronary angiography ( qca ) .
all scans were analyzed independently by a radiologist and a cardiologist who were unaware of the results of conventional coronary angiography .
total calcium scores of all patients were calculated with dedicated software and expressed as agatston scores .
the agatston score is a commonly used scoring method that calculates the total amount of calcium on the basis of the number , areas , and peak hounsfield units of the detected calcified lesions .
all available coronary segments were visually scored for the presence of > 50% considered as significant stenosis .
maximum intensity projections were used to identify coronary lesions and ( curved ) multiplanar reconstructions to classify lesions as significant or nonsignificant .
data were analyzed using statistical system spss version 20 software ( chicago , il , usa ) .
the diagnostic performance of ct coronary angiography for the detection of significant lesions in coronary arteries with qca as the standard of reference is presented as sensitivity , specificity , positive and negative predictive values , and positive and negative likelihood ratios with the corresponding exact 95% of confidence interval ( cis ) .
comparison between ct and conventional coronary angiography was performed on the two level vessel by vessel ( no or any disease per vessel ) , and patient by patient ( no or any disease per patient ) .
all scans were performed within 2 weeks of the msct coronary diagnostic angiogram . a single observer unaware of the multi - slice ct results identified coronary lesion as a single vessel , double vessel , or triple vessel disease .
all lesion , regardless of size , were included for comparison with ct coronary angiography .
lesions were classified as having nonsignificant disease ( luminal irregularities or < 50% stenosis ) or as having significant stenosis .
stenosis was evaluated in two orthogonal views and classified as significant if the mean lumen diameter reduction was 50% using a validated quantitative coronary angiography ( qca ) .
all scans were analyzed independently by a radiologist and a cardiologist who were unaware of the results of conventional coronary angiography .
total calcium scores of all patients were calculated with dedicated software and expressed as agatston scores .
the agatston score is a commonly used scoring method that calculates the total amount of calcium on the basis of the number , areas , and peak hounsfield units of the detected calcified lesions .
all available coronary segments were visually scored for the presence of > 50% considered as significant stenosis .
maximum intensity projections were used to identify coronary lesions and ( curved ) multiplanar reconstructions to classify lesions as significant or nonsignificant .
data were analyzed using statistical system spss version 20 software ( chicago , il , usa ) .
the diagnostic performance of ct coronary angiography for the detection of significant lesions in coronary arteries with qca as the standard of reference is presented as sensitivity , specificity , positive and negative predictive values , and positive and negative likelihood ratios with the corresponding exact 95% of confidence interval ( cis ) .
comparison between ct and conventional coronary angiography was performed on the two level vessel by vessel ( no or any disease per vessel ) , and patient by patient ( no or any disease per patient ) .
in this study , 29 ( 58% ) subjects were female , and 21 ( 42% ) were male showing an average age of 50.36  8.39 years .
of fifty patients 24 ( 48% ) , 13 ( 26% ) , eight ( 16% ) , and five ( 10% ) underwent mitral valve replacement , double valve replacement ( dvr ) , aortic valve replacement , and other surgeries , respectively .
high distribution of cad risk factors such as hypertension ( 24% ) , smoking ( 22% ) , and dyslipidemia ( 18% ) was observed in the study group .
the mean creatinine level was 0.766  0.17 and average dye used in conventional angiography was 48.5  26.6 whereas for ct angiography it was 72.8  6.32 .
average radiation dose in conventional coronary angiography and msct coronary angiography was 5.2 msv and 9.2 msv , respectively .
the majority of the patients had sinus rhythm ( 68% ) , whereas atrial fibrillation was found in 32% of the subjects .
patients included in the study had low to intermediate probability of cad . in this study , three patients had complications after conventional angiography .
complications were of local site hematoma , acute kidney injury managed conservatively , and acute heart failure .
a patient who developed hematoma was obese female patients with body mass index > 30 kg / m .
the patient suffered from pseudoaneurysm , had hospitalized for 9 days , which leads to increased morbidity and cost of hospital stay .
the diagnostic accuracy of ct coronary angiography was evaluated regarding true positive , true negative values and is presented in table 1 . the overall sensitivity and
specificity of ct angiography technique was 100% ( 95% ci : 39.76%100% ) and 91.30% ( 95% ci : 79.21%97.58% ) , respectively [ table 2 ] .
the positive predictive value ( 50% ; 95% ci : 15.70%84.30% ) and negative predictive value ( 100% ; 95% ci : 91.59%100% ) of ct angiography were also fairly high in these patients .
recent reports from multiple studies demonstrated that recent - generation msct scanners showed promise for noninvasive detection of coronary stenosis however , until now no studies were found regarding the clinical efficacy or prognostic value of 128-slice ct coronary angiography versus conventional invasive coronary angiography in the diagnosis of patients planned for major noncoronary surgeries such as dvr , bentall , atrial septal defect closure , etc . in our study , we reported 8% cad prevalence in patients planned for major noncoronary cardiac surgery .
we performed conventional and msct coronary angiography in all patients and the results showed that ct coronary angiography with invasive coronary angiography as the reference standard had a considerably high sensitivity ( 100% ) and specificity ( 95.65% ) .
the health economic model using invasive coronary angiography as the reference standard showed that at a pretest probability of cad of 70% or lower , ct coronary angiography resulted in lower cost per patient with a true positive diagnosis . at a pretest probability of cad of 70% or higher , invasive coronary angiography was associated with a lower cost per patient with a true positive diagnosis . in our study population ,
two patients developed local site complications in the form of hematoma and pseudoaneurysm after conventional angiography .
hence , msct coronary angiography will be more favorable in female obese patients with intermediate likelihood of cad .
hence , msct coronary angiography will be cost - effective in patients of valvular heart diseases .
however , ct angiography suffers from a drawback that average amount of dye used in msct coronary angiography were 72.8  6.32 ml which is higher than average amount of dye required for conventional angiography ( 48.6  26.6 ml ) .
hence , the use of ct coronary angiography could not be used in patients with known renal dysfunction , where reduction of contrast dye load is highly advocated .
our results show that 128-slice ct coronary angiography is a reliable technique to detect coronary stenosis in patients planned for noncoronary cardiac surgery .
although there has been important technological progress in the development of ct coronary angiography , its clinical application remains limited .
a study wth large numbers of patients is required for the recommendation of only ct coronary angiography for the coronary evaluation in major non - cardiac surgeries .
mehta institute of cardiology and research center ( affiliated to bj medical college , ahmedabad , gujarat , india ) .
u.n . mehta institute of cardiology and research center ( affiliated to bj medical college , ahmedabad , gujarat , india ) .
objective : to compare the diagnostic accuracy of multi - slice computed tomography ( msct ) angiography with conventional angiography in patients undergoing major noncoronary cardiac surgeries.materials and methods : we studied fifty major noncoronary cardiac surgery patients scheduled for invasive coronary angiography , 29 ( 58% ) female and 21 ( 42% ) male . 
 inclusion criteria of the study were age of the patients 40 years , having low or intermediate probability of coronary artery disease ( cad ) , left ventricular ejection fraction ( lvef ) > 35% , and patient giving informed consent for undergoing msct and conventional coronary angiography . the patients with lvef < 35% , high pretest probability of cad , and hemodynamically unstable were excluded from the study.results:the diagnostic accuracy of ct coronary angiography was evaluated regarding true positive , true negative values . the overall sensitivity and 
 specificity of ct angiography technique was 100% ( 95% confidence interval [ ci ] : 39.76%100% ) and 91.30% ( 95% ci : 79.21%97.58% ) . the positive ( 50% ; 95% ci : 15.70%84.30% ) and negative predictive values ( 100% ; 95% ci : 91.59%100% ) of ct angiography were also fairly high in these patients.conclusion:our study suggests that this non - invasive technique may improve perioperative risk stratification in patients undegoing non - cardiac surgery .