Interobserver variability of CT angiography for evaluation of aortic annulus dimensions prior to transcatheter aortic valve implantation (TAVI).

OBJECTIVE: Assessment of aortic annulus dimensions prior to transcatheter aortic valve implantation (TAVI) is crucial for accurate prosthesis sizing in order to avoid prosthesis-annulus-mismatch possibly resulting in complications like valve dislodgement, paravalvular regurgitation or annulus rupture. Contrast-enhanced multidetector computed tomography allows 3-dimensional assessment of aortic annulus dimensions. Only limited data exist about its interobserver variability. METHODS: In 100 consecutive patients with symptomatic severe aortic stenosis (51 male, BMI 27±5kg/m(2), age 81±7 years, heart rate 72±15bpm, Logistic Euroscore 31±14%, STS-Score 7±4%), pre-interventional aortic annulus assessment was performed by dual source computed tomography (collimation 2×128×0.6mm, high pitch spiral data acquisition mode, 40-60ml contrast agents, radiation dose 3.5±0.9mSv). The following aortic annulus characteristics were determined by three independent observers: aortic annulus maximum, minimum and mean diameters (Dmax, Dmin, Dmean), eccentricity index (EI), effective aortic annulus diameter according to its circumference (Dcirc), effective aortic annulus diameter according to its area (Darea), distance from the aortic annulus plane to the left (LCA) and right coronary artery (RCA) ostia, maximum (DmaxAR) and minimum aortic root diameter (DminAR), maximum (DmaxSTJ) and minimum diameter of the sinotubular junction (DminSTJ). Subsequently, interobserver variabilities were assessed. RESULTS: Correlation between the three observers showed moderate to close agreement (between r=0.67 and r=0.97, all p<0.001). Mean differences (SE) between the three observers ranged from 0.07 (0.06)mm to 0.24 (0.07)mm for assessing the mean AA diameter (Dmean), from 0.28 (0.04)mm to 0.60 (0.06)mm for determining the effective AA diameter derived from the annulus area (Darea) and from 0.03 (0.07)mm to 0.07 (0.11)mm derived from the AA perimeter (Dcirc). For measurements of LCA and RCA distances to the AA level, mean interobserver differences (SE) ranged from 0.36 (0.07)mm to 0.76 (0.09)mm and from 0.15 (0.06)mm to 0.45 (0.11)mm. CONCLUSION: Computed tomography provides reproducible measurements of the aortic annulus and root geometry in patients scheduled for TAVI. The perimeter-derived aortic annulus diameter shows the lowest interobserver differences. Interobserver variabilities in prosthesis size recommendation were further reduced, if all three sizing methods were considered and stated as a "consensus result".

Coronary CT angiography in the elderly.

People over 75 years of age represent a specific group of patients for which the clinician is often in doubt about what to do, whether additional diagnostic workup is helpful or a primary medical approach would suffice. However, this patient population is less prone to the long-term effects of radiation burden or contrast medium-induced nephropathy, and therefore it may be especially worthwhile to use advanced imaging techniques such as contrast-enhanced CT in these patients. The following cases illustrate two common diagnostic problems, in which coronary CT angiography decided the clinical course.

Clinical characteristics of patients with obstructive coronary lesions in the absence of coronary calcification: an evaluation by coronary CT angiography.

BACKGROUND: Multidetector CT allows detection of coronary artery calcium and, after contrast injection, visualisation of the coronary artery lumen. It is commonly assumed that the absence of coronary calcification makes the presence of obstructive coronary lesions highly unlikely. This study evaluates the clinical characteristics of patients with at least one symptomatic, high-grade coronary artery stenosis in both computed tomography and invasive angiography but absence of any coronary calcification and compares the results with patients with stenoses in the setting of detectable coronary calcium PATIENTS AND METHODS: The study retrospectively identified 21 consecutive patients with symptoms in whom a high-grade coronary artery stenosis had been identified in 64-slice or dual-source CT coronary angiography (Siemens Sensation 64 or Siemens Definition, 120 kV, 50 to 85 ml of intravenous contrast at 5 ml/s) in the absence of coronary calcium and in whom that finding had been confirmed by invasive coronary angiography. Clinical presentation ("unstable": all forms of acute coronary syndrome versus "stable": stable chest pain or dyspnoea on exertion) and standard cardiovascular risk factors were assessed, and the results were compared with 42 consecutive patients with symptoms in whom both coronary calcium and coronary stenoses had been identified in computed tomography and invasive coronary angiography. RESULTS: The majority of patients with coronary stenoses in the absence of coronary calcium presented with "unstable" symptoms (non-ST-segment elevation myocardial infarction (NSTEMI) or unstable angina), significantly more frequently than patients with detectable calcification (71% vs 26%, p = 0.001). The age range of patients without calcium was 33 to 76 years, their mean age was younger (53 (SD 13) vs 63 (8) years, p<0.001), but none of the risk factors showed any significant difference compared with patients with calcification. CONCLUSION: The presence of significant coronary artery stenosis in the absence of coronary calcium is possible. It is more likely in the setting of unstable angina or NSTEMI than in stable chest pain and occurs more frequently in younger patients.

Assessment of regional left ventricular function by dual source computed tomography: interobserver variability and validation to laevocardiography.

OBJECTIVE: Assessment of left ventricular function is possible in contrast-enhanced cardiac CT data sets. However, rapid ventricular motion especially in systole can lead to artifacts. Dual Source Computed Tomography (DSCT) has high temporal resolution which effectively limits motion artifact. We therefore assessed the accuracy of DSCT to detect regional left ventricular wall motion abnormalities in comparison to invasive cine angiocardiography. METHODS: We analyzed DSCT data sets of 50 patients (39 male, 11 female, mean age: 61+/-10 years) which were acquired after intravenous injection of 55-70 mL contrast agent (rotation time: 330 ms, collimation: 2 mm x 64 mm x 0.6 mm, 120 kV, 380 mAs, ECG-correlated tube current modulation). 10 data sets consisting of transaxial slices with a slice thickness of 1.5 mm, an increment of 1.0 mm and a matrix of 256 x 256 pixels were reconstructed at 10 time instants during the cardiac cycle (0-90% in 10% increments). The data sets were analyzed visually by two independent readers, using standard left ventricular planes, concerning regional wall motion abnormalities. DSCT was verified in a blinded fashion against cine ventriculography performed during cardiac catheterization (RAO and LAO projection), using a 7-segment model. Analysis was performed on a per-patient (presence of at least one hypo-, a- or dyskinetic segment) and on a per-segment basis. RESULTS: Concerning the presence of a wall motion abnormality, the two observers agreed in 340/350 segments (97%) and 48/50 patients (96%). In invasive cine angiocardiography, 22 of 50 patients displayed at least one segment with abnormal contraction. To detect these patients, DSCT showed a sensitivity of 95% (21/22), specificity of 96% (27/28), positive predictive value of 95% and negative predictive value of 96%. Out of a total of 350 left ventricular segments, 66 segments had abnormal contraction in cine angiocardiography (34 hypokinetic, 26 akinetic, 6 dyskinetic). For detection of these segments, DSCT had a sensitivity of 88% (58/66), specificity of 98% (278/284), positive predictive value of 91% (58/64) and negative predictive value of 97% (278/286). CONCLUSION: DSCT allows the detection of regional wall motion abnormalities with high interobserver agreement as well as high sensitivity and specificity. Whereas sensitivity and positive predictive value were higher in a per-patient- in comparison to a per-segment-based analysis, specificity, negative predictive value and interobserver agreement did not differ considerably between both analyzing methods.

Differentiation of total occlusion and high-grade stenosis in coronary CT angiography.

In coronary CT angiography (CTA), both high-grade stenoses and total occlusions of a coronary artery may appear as a complete interruption of the contrast-enhanced lumen. Parameters to differentiate between occlusions and stenoses have not been systematically assessed. We evaluated 40 consecutive patients with a lesion demonstrating complete interruption of the contrast-enhanced lumen in coronary CTA and in whom invasive coronary angiography was available. Length of the vessel segment without luminal contrast enhancement; luminal enhancement proximal, in and distal to the lesion; degree of coronary remodelling; and the degree of lesion calcification were assessed by a blinded observer unaware of the invasive angiogram. Mean length of complete occlusions (n = 20; range 4-54 mm; mean 16.6 +/- 3.5 mm) was significantly longer than for high-grade stenoses (n = 20; 2-8 mm; mean 4.6 +/- 1.7 mm, p < 0.001). A lesion length > or = 9 mm was 100% specific and 70% sensitive for an occlusion. No significant differences were found for vessel enhancement in or distal to the lesion, remodelling index or degree of calcification. Lesion length is the only parameter that may differentiate complete occlusions and high-grade stenoses in coronary CTA. For lesions > or = 9 mm, an occlusion is very likely.

Interobserver variability of 64-slice computed tomography for the quantification of non-calcified coronary atherosclerotic plaque.

PURPOSE: Multidetector CT (MDCT) is a reliable tool to assess and quantify calcified plaque in coronary arteries. Only very limited information is available concerning the accuracy of MDCT for evaluating non-calcified plaque. We determined the interobserver variability for measuring non-calcified plaque volumes in the three main coronary arteries using 64-slice computed tomography. MATERIALS AND METHODS: We retrospectively evaluated data sets of 41 patients who received a 64-slice CT scan (Sensation 64, Siemens Forchheim, Germany, 330 msec rotation, 0.6 mm collimation, 60 ml contrast agent i. v. at 5 ml/sec) due to suspected stable coronary artery disease. The patients showed presence of non-calcified plaque in the proximal part of at least one main coronary artery. The image quality was defined on the basis of a 4-point rating scale. Two independent and blinded investigators measured the plaque volume of the non-calcified plaque by manually tracing plaque areas in contiguous cross-sectional reconstructions rendered along the vessel centerline using a slice thickness of 1 mm and an increment of 0.5 mm. The interobserver variability was evaluated and the influence of plaque volume and image quality on interobserver variability was determined. RESULTS: The mean volume of non-calcified plaque was 157 +/- 85 mm (3), 76 +/- 43 mm (3) and 133 +/- 80 mm (3) for the LAD, LCX and RCA, respectively (LAD vs. LCX: p < 0.01; LAD vs. RCA: p = 0.33; LCX vs. RCA: p < 0.01). There was a mean absolute difference in plaque volume between the two observers of 23 +/- 15 mm (3), of 20 +/- 9 mm (3) and of 38 +/- 21 mm (3), which corresponds to a mean interobserver variability of 17 +/- 10 %, 29 +/- 13 % and 32 +/- 13 % for the LAD, LCX and RCA, respectively (LAD vs. LCX: p < 0.01; LAD vs. RCA: p < 0.01; LCX vs. RCA: p = 0.87). A significant inverse correlation between interobserver variability and the extent of the plaque volume (r = - 0.48; p = 0.01) was found. Interobserver variability was dependent on image quality: The highest image quality was observed in the LAD (2.4 +/- 0.5), while the image quality in the LCX (2.1 +/- 0.7) and the RCA (2.0 +/- 0.6) was lower. CONCLUSION: Interobserver variability for the quantification of non-calcified plaque volumes in 64-slice MDCT is substantial. Interobserver variability in the LAD was significantly lower than in the LCX and the RCA. This might be due to a larger mean plaque volume and better image quality in the LAD than in other coronary arteries.

BRAVO I: A pilot study of vascular brachytherapy in polytetrafluoroethylene dialysis access grafts.

Hemodialysis vascular access dysfunction owing to stenosis and thrombosis in polytetrafluoroethylene dialysis access grafts is a huge clinical problem for which there are currently no long lasting durable therapies. Vascular brachytherapy has been used successfully for the prevention of coronary restenosis following angioplasty and stent placement. The Beta Radiation for Treatment of Arterial-Venous Graft Outflow I study was a pilot study of vascular brachytherapy in hemodialysis patients with patent but dysfunctional grafts. Twenty-five patients were randomized to receive either radiation therapy (a single dose of 18.4 Gy) or sham radiation, following angioplasty. The primary efficacy end point of the study was target lesion primary patency at 6 months. The primary safety end point was a composite of death, emergency surgery on the graft, venous rupture, or aneurysm formation. Forty-two percent of the radiated grafts achieved the target lesion primary patency end point at 6 months as compared to 0% of the control group (P = 0.015), but this did not translate into an improvement in secondary patency at either 6 or 12 months. Radiation therapy was found to be safe in the setting of hemodialysis vascular access dysfunction. Our results suggest that vascular brachytherapy is an intervention that is worthy of further examination in the setting of non-thrombosed dialysis access grafts.

Emergency fluid management for hypovolemia.

Emergency fluid resuscitation of hypovolemic patients begins with an accurate assessment of the degree of volume depletion as well as identification of the cause and associated abnormalities. On the basis of this information, the proper resuscitative fluid can be chosen and administered by the appropriate route, as guided by the urgency of the situation. Patients with severe volume depletion and those in shock require intravenous fluids. In other situations, oral rehydration is often appropriate. Specific fluids then can be tailored to the individual patient's needs and adjusted as warranted by ongoing monitoring.

Is 8 hours of nightly peritoneal dialysis enough?

Eight hours of nightly tidal peritoneal dialysis (TPD) theoretically can provide uremia control equal that of continuous cyclic peritoneal dialysis (CCPD). To assess the in vivo validity of this prediction, six patients underwent mass transfer area coefficient (MTaC) measurements and dialysis using CCPD and TPD. CCPD consisted of five nighttime exchanges of 40 ml/kg and a daytime exchange of 20 ml/kg. TPD used an initial fill of 40 ml/kg and hourly tidal flows of 30 or 50 ml/kg. The nocturnal portion of CCPD lasted 9.7 hr (range 9.5-10 hr). TPD lasted 8.5 hr (range 8-9 hr) and was devoid of daytime dialysis. The patients consumed a diet containing 1.2 +/- 0.07 g protein/kg body weight (range 0.7-1.7 g/kg) and had a pre dialysis blood urea nitrogen concentration of 52 mg/dl (range 18-82 mg/dl). The dialysate clearances of urea and creatinine were indexed to patient size and extrapolated to weekly values. CCPD provided a weekly creatinine clearance of 50 L/1.73 m2 and a Kt/Vurea of 2.06. TPD with an hourly dialysate flow of 30 ml/kg achieved a weekly creatinine clearance of 42.8 L/1.73 m2 and a Kt/Vurea of 1.73. When the hourly dialysate flow was increased to 50 ml/kg, these values improved to 53.3 L/1.73 m2 and 2.15, respectively. Dialysis efficiency equal to that of CCPD can be obtained using 8 hr of TPD when membrane characteristics (mass transfer area coefficient) and dialysate flow rates are appropriate. Patients with normal or above normal mass transfer area coefficients can obtain a weekly Kt/Vurea exceeding 2.0 using nightly high flow TPD.

Tidal peritoneal dialysis: kinetics and protein balance.

Some patients find automated peritoneal dialysis preferable to continuous ambulatory peritoneal dialysis (CAPD). Unfortunately, automated peritoneal dialysis prescriptions are time consuming and can impede rehabilitation. We wished to determine whether an 8-hour tidal peritoneal dialysis (TPD) prescription could maintain the time averaged blood urea nitrogen at 60 mg/dL or less while patients consumed a diet containing approximately 1.2 g protein/kg body weight/d. Ten home dialysis patients previously stabilized on continuous cyclic peritoneal dialysis volunteered for a metabolic balance study conducted at the University of Iowa's Clinical Research Center. A peritoneal equilibration test was conducted and mass transfer area coefficients (MTaCs) were derived for each subject. Nitrogen balance was measured during the last 5 days of a 12-day constant diet while patients underwent a series of monitored nocturnal dialyses. Mass transfer area coefficient measurements were reproducible and independent of the filling volume and ultrafiltration, but varied between subjects (normalized MTaCurea = 33.6 +/- 16.3 mL/min, normalized MTaCcrt = 16.3 +/- 9.5 mL/min). Tidal peritoneal dialysis urea and creatinine clearances could be predicted by these MTaC values (r2 = 0.70 urea, r2 = 0.91 creatinine). Nitrogen balance assumptions predicted, and we confirmed, a relationship between dietary protein intake and urea nitrogen generation (r2 = 0.82) during TPD. A normalized protein catabolic rate of 1.2 g/kg/d resulted in a urea nitrogen generation rate of approximately 100 mg/kg/d. If a patient's protein intake was approximately 1.2 g/kg/d, then TPD with a weekly urea clearance normalized to body volume (Kt/V(urea)) of approximately 2.1 (urea clearance, approximately 0.35 mL/kg/min) could maintain a time averaged blood urea nitrogen of approximately 60 mg/dL.(ABSTRACT TRUNCATED AT 250 WORDS)