الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
IHD is the primary single cause of left ventricular systolic dysfunction leading to heart failure in Europe. Left ventricular function is an important determinant of prognosis and parameters that reflect function, such as left ventricular ejection fraction [LVEF], end-diastolic volume, end-diastolic pressure and exercise capacity can all be used to help predict outcome.
Additionally, in patients studied after coronary artery surgery, LV ejection fraction was shown to be a more important predictor of survival than the number of coronary arteries bypasses. Independent examination of LV function is important because the degree of coronary stenosis and LV function is nonlinear.
Conversely, LV dysfunction, even in a regional distribution, does not always predict an underlying coronary lesion. CTA provides the unique ability to evaluate both structure and function with a single test, offering convenience for both patients and clinicians.
This current study was conducted on 50 patients who suspected ischemic heart disease to evaluate the current accuracy of multidetector Computed Tomography in the evaluation of the left ventricular function in comparison with magnetic resonance imaging.
All patients were subjected to full history taking, thorough clinical examination and review of the laboratory investigations and of available previous imaging studies. Patients with heart rate >60 beat/min received β-blocker; 100 mg atenolol orally 1 hour before the scan.
All patients were scanned using a 64-MDCT scanners. The scan range was extended to the level of the subclavian arteries in patients with internal mammary artery grafts. A bolus of iodinated contrast material (Ultravist 370, Schering AG, Berlin, Germany), which varied between 80 and 100 ml depending on the expected scan time, was injected in an antecubital vein followed by a saline chaser (40 ml; flow rate 4.0 to 5.0 ml/s). The flow rate (4.0 to 5.0 ml/s) was adjusted to the scan range (presence of left internal mammary artery) and the expected scan time (pitch dependent).
The retrospective gating technique was used to synchronize data reconstruction with ECG signal. Best systolic and diastolic reconstructions were made in all patients at a slice thickness of 0.75 mm and a reconstruction increment of 0.4 mm. The reconstruction with fewest motion artifacts was chosen and used for further analysis.
All patients were also scanned by a 1.5-tesla whole-body scanner (Magnetom, Avanto by Siemens, Erlangen, Germany) using a four-element, phased-array cardiac coil. Electrocardiographically gated cine images were acquired using a steady-state free precession sequence. To assess the apex, one vertical and one horizontal long-axis view were obtained. 10–12 short-axis views [slice thickness 8 mm, 2 mm gap] covering the whole left ventricle were obtained during repeated breath-holds.
All patients were examined by MDCT and MRI within the same hour.
For functional analysis by MDCT, image reconstruction was performed from raw data, 10 sets of reconstructions at every 10% (0% –90%) of R –R interval were performed. Short-axis cine images and vertical and horizontal long-axis cine images were reoriented from the reconstruction data by using cardiac multi-planar reformats (MPR) software (Toshiba, Vitrea) in 10-mm thickness without inter-slice gap. Only in ten patients 20 sets of reconstruction at every 5% (0%-95%) of R-R interval were additionally performed.
LV volumes and ejection fraction derived from cine cardiac MR imaging were analyzed by using a commercial software [Syngo Argus Ventricular Function; Siemens Medical Solutions]. Wall motion was assessed by visual interpretation for each myocardial sector on each cross section and classified as normal contractility, hypokinesia, akinesia and dyskinesia.
Global functional parameters were derived with the aid of commercially available software (Argus; Siemens) Global and regional function was assessed with the same approach as in CT studies. For image quality and regional wall motion analyses, cine loops were also evaluated by two experienced observers independently in the 17-segment model.
Their total mean age of the patients was found 59.36 years, with their ages ranged between 33 and 76 years old. The majority of patient population laid at the age group of 51-60 years which was represented by 23 patients (46%). There were a total number of 42 males (84%) and 8 females (16%).
There were 50 patients, 12 patients had normal coronaries angiographic study (24%), seven patients (14%) had single vessel disease, six patients (12%) had two vessel disease, six patients (12%) had three vessel disease, six patients had multiple stents (PTCA) (12%), 10 patients had done CABG (20%) six of them had occluded arterial and venous grafts, and only three patients (6%) had myocardial bridging of LAD.
There were 19 patients with no previous intervention and had coronary disease, 3 patients (15.7%) had significant (> 70% stenosis) LAD artery lesions, three patients (15.7%) had significant RCA lesions, one patient (0.5%) had LCx artery significant lesion, 4 patient (21%) had combined LAD and RCA significant lesions, two patients (10.5 %) had LAD and LCx significant lesions, and six patients (31.5%) had three vessel significant lesions including LAD, LCx and RCA.
There were 10 patients with previous CABG, six patients (60%) had occluded arterial or venous grafts and only four patients had patent grafts.
Average EDV was 149.88± 31.09 ml (range 95– 230 ml) on MDCT, as compared with 149.91± 31.09ml (range 99– 238 ml) on MRI. Linear regression analysis showed a good correlation between MDCT and MRI for the assessment of EDV.
Average ESV was 72.12± 32.63 ml (range 33– 158ml) on MDCT, as compared with 71.29± 32.05 ml (range 35– 155 ml) on MRI. Linear regression analysis showed a good correlation between MDCT and MRI for the assessment of ESV .
Average EF was 53.84 ± 11.21% (range 28- 69%) as determined on MDCT, compared with 54.53± 10.85% (range 28% - 68%) on MRI. Evaluation of EF by linear regression analysis demonstrated a good correlation between MDCT and MRI
In this study there were 850 segments examined, 584 segments (68.7%) showed normal motility, 188 segments (22.1%) showed hypokinesia, 76 segments (8.9 %) showed akinesia and 10 segments (1.1%) showed dyskinesia by MRI examination
In this study there were 850 segments examined, 590 segments (69.4%) showed normal motility, 182 segments (21.5%) showed hypokinesia, 76 segments (8.9 %) showed akinesia and 10 segments (1.1%) showed dyskinesia by CT examination
All patients with no CT findings of CAD show normal ejection fraction values (15 patients). Patients with one vessel significant lesion were seven in number, three of them show normal EF value, two with mildly reduced EF, and two patients with severely reduced EF. Two of the patients with one vessel disease show mild hypokinesia of the segments supplied by the diseased artery, while showing akinesia and wall thinning of segments supplied by normal artery by CT angiography. Four patients with significant two vessels disease show normal EF values while two of them show moderately reduced EF. Patients with three vessels disease were six in number, two of them had normal EF and four of them show severely reduced EF. Ten patients had CABG, four of them show normal EF, and two of the four patients show occluded grafts although showing mild decreased motility and normal EF. The remaining six patients who had CABG show mildly reduced ejection fraction.
Excellent agreement was noticed in this study between MDCT and CMR in the assessment of global left ventricular function and regional wall motion abnormalities.
Information for LV function analysis could be collected from the data set acquired for the evaluation of the coronary arteries by the retrospective method, lately prospective ECG gating has become available, Making data-acquisition for MDCT coronary angiography during only a small proportion of the cardiac cycle. Since assessment of LV function requires data-acquisition during an entire cardiac cycle, functional study will prolongs the total exposure time in machines using prospective ECG gating, . Subsequently, the MDCT study of LV function increases the dose of radiation when compared to coronary angiography MDCT for purpose of evaluating the coronary arteries alone. So the need for LV function analysis should be cautiously considered for each separate patient.
Since high-quality images are not necessary for LV functional assessment as in the coronary imaging, accurate functional assessment will be reached with a use of low dose of contrast media. Consequently, CT could be considered an alternative of CMR in patients with metal implants (e.g. pacemakers– defibrillators) and claustrophobia.