Imaging of the Cardiac Venous System: Comparison of MDCT and Conventional Angiography

Transcription

1 Mühlenbruc h et al. Imaging the Cardiac Venous System Cardiac Imaging Clinical Observations Georg Mühlenbruch 1 Ralf Koos 2 Joachim E. Wildberger 1 Rolf W. Günther 1 Andreas H. Mahnken 1 Mühlenbruch G, Koos R, Wildberger JE, Günther RW, Mahnken AH DOI: /AJR Received August 3, 2004; accepted after revision November 10, Department of Diagnostic Radiology, RWTH Aachen University Hospital, Pauwelsstrasse 30, Aachen 52057, Germany. Address correspondence to G. Mühlenbruch (gmuehlen@rad.rwth-aachen.de). 2 Department of Cardiology, RWTH Aachen University Hospital, Aachen 52057, Germany. AJR 2005; 185: X/05/ American Roentgen Ray Society Imaging of the Cardiac Venous System: Comparison of MDCT and Conventional Angiography OBJECTIVE. Diagnostic and therapeutic strategies in electrophysiology and interventional cardiology include the coronary venous system. The purpose of this study was to compare MDCT angiography with conventional coronary sinus angiography in terms of detailed anatomic display of the coronary veins. CONCLUSION. MDCT angiography is a reliable alternative to conventional coronary sinus angiography for detailed anatomic display of the coronary veins. n addition to coronary arteries, the I coronary venous system is a field of growing interest in diagnostic and interventional cardiology. This interest is based on a growing number of diagnostic and therapeutic procedures that include the coronary venous system: cardiac electrophysiological studies with placement of a catheter in the coronary sinus (CS), radiofrequency ablation of posteroseptal or leftsided accessory pathways [1], or retroperfusion therapy in high-risk or complicated coronary angioplasty [2]. Further therapeutic approaches include the use of the coronary venous system as a conduit for bypassing coronary artery stenoses [3] and for local drug and gene delivery [4]. In addition, the coronary venous system is increasingly being used for left ventricular or biventricular pacing in patients with severe heart failure [5]. Because the coronary veins are variable in number, caliber, and course, detailed knowledge of the patient s individual anatomy is essential for optimum planning of the intended procedure. Thus, there is a need for imaging the cardiac venous system. The current gold standard for imaging of the coronary veins is retrograde coronary venography via the coronary sinus. It is frequently performed before placement of left ventricular pacemaker leads or in patients with accessory pathways who are undergoing radiofrequency ablation. Conventional angiography requires central venous access and may be technically challenging because of difficult intubation of the coronary sinus and vigorous backwash of contrast material into the right atrium [5]. Because only the venous system is visualized, conventional angiography is of limited value for some interventional cardiac procedures, for example, using the coronary venous system for conduits to bypass coronary artery stenoses. Before these procedures, an additional catheter-based coronary angiography is needed. Contrast-enhanced MDCT angiography with high spatial and temporal resolution allows for diagnostic evaluation of the coronary arteries [6]. MDCT angiography is less invasive than conventional angiography and has fewer complications; it may therefore be an alternative tool for visualization of the coronary veins. The usefulness of electron beam CT for visualization of the coronary veins has already been shown [7]. To the best of our knowledge, this is the first study comparing MDCT angiography to conventional angiography as the reference standard. Materials and Methods Patients Within 5 months from March 2002 until August 2002, 22 patients (6 men, 16 women; mean age, 62.9 ± 10.6 years) underwent conventional angiography. Seven of these patients also underwent MDCT angiography and were included in the study. The mean time interval between the two examinations was 4.3 ± 3.6 days. In five patients, placement of a left ventricular lead for biventricular pacing was planned; two patients underwent radiofrequency ablation. MDCT angiography was conducted to gain additional information on coronary arteries, cardiac chamber morphology, and cardiac function. Exclusion criteria were renal insufficiency with creatinine 1252 AJR:185, November 2005

2 Imaging the Cardiac Venous System levels higher than 1.3 mg/dl, hyperthyroidism, intolerance to iodinated contrast agents, atrial fibrillation, previous placement of cardiac pacemaker leads, and inability to suspend breathing for about 40 sec. The study was approved by the local institutional review board, and informed consent was obtained from each patient. A C Fig year-old man with left bundle branch block prior to resynchronization therapy. LA = left atrium, LV = left ventricle, RA = right atrium, RV = right ventricle, RCA = right coronary artery. A, Example (multiplanar reformation) of measurement of vessel diameter at orifice of coronary sinus (arrow). B D, Maximum intensity projections (MDCT angiography) of different cardiac veins: B, posterior cardiac vein (arrow); C, left marginal vein (arrow); D, small cardiac vein (arrowhead); arrow in D denotes RCA. Coronary Sinus Angiography Retrograde coronary catheter venography was performed via femoral venous access by an experienced cardiologist. Estimated radiation dose was 2 msv, and 50 to 60 ml of iodinated contrast agent was administered. Venograms were obtained in right anterior oblique (60 ) and left anterior oblique (30 ) views. The different image series were stored digitally (ACOM version 3.0, Siemens Medical Solutions) and analyzed at a separate workstation. Vein diameters were measured after catheter-based image calibration (QuantCor, CASS II; Siemens Medical Solutions) by an experienced electrophysiologist. The catheter was always centered and as- B D AJR:185, November

3 Mühlenbruch et al. sessed in the middle of the view in all patients. Thus, variations were minimized. MDCT Angiography All MDCT examinations were performed with a 4-MDCT scanner (Somatom Volume Zoom, Siemens) during a single end-expiratory breath-hold of sec (median, 42.3 sec) in a supine position. A standardized examination protocol with 4 1 mm collimation, 1.5-mm table feed per rotation (normalized pitch: 0.375), and a gantry rotation time of 500 msec was used. Tube voltage was 120 kv with a tube current of 400 mas eff. Contrast material was administered via an 18-gauge needle in the right cubital vein. The scanning delay was determined by injection of a 20-mL test bolus with a flow rate of 2.5 ml/sec and repeated scanning at the level of the aortic root. The time to peak enhancement plus 5 sec was chosen as delay time. For vessel enhancement, 120 ml of nonionic contrast material (Ultravist 370 [iopromide], Schering) was injected at a flow rate of 2.5 ml/sec. Both injections were followed by a 50-mL saline chaser injected at the same flow rate. Average heart rate during the MDCT examination was 73.2 ± 13.3 bpm (range, bpm); no medication was given to slow down the heart rate. Estimated radiation dose using WinDose 2.1 (IMP) [8] was 6.5 ± 1.2 msv for men and 10.3 msv for women. Axial image series were reconstructed at 0 100% of the R-R interval in steps of 5% with an effective slice thickness of 1.25 mm and a reconstruction increment of 0.8 mm. A field of view of mm 2, a matrix of , and a mediumsmooth convolution kernel (B30f) were applied. All image series were transferred to an external workstation (Leonardo, Siemens) and analyzed using the standard software package (Syngo CT, Siemens). From the image series presenting with the least motion artifacts, multiplanar reconstructions (MPR) and maximum intensity projections (MIP) along the course of the coronary veins and 3D volume-rendering technique images (3D-VRT) were obtained. Image analysis was performed by an experienced radiologist using all of the described images and blinded to the results of conventional angiography. Thus, the final MDCT angiography interpretation of the coronary veins represents an integrated opinion based on all image-display techniques mentioned above. In both techniques (conventional angiography and MDCT angiography), visibility of the coronary veins was graded visually using a 4- point scale for each coronary vein (grade 0, not visible; grade 1, visible with discontinuity; grade 2, visible with irregular borders; grade 3, visible as smoothly bordered vascular structure). The diameter of each of these coronary veins was measured at its orifice (Fig. 1). Statistical Analysis Statistical analysis was performed using SAS System for Windows (Microsoft), release 8.02 TS level 02M0 (SAS Institute). Venous visibility is given as median and range. Statistical analysis for visibility comparing conventional angiography and MDCT angiography was performed using Pearson s correlation coefficient. Values for vessel diameter are given as mean ± SD. An equivalence test for conventional angiography and MDCT angiography was applied and a difference of 0.5 mm was considered acceptable. Bland-Altman plots for method comparison were calculated. Results In all patients, conventional angiography and MDCT angiography were successfully completed without the occurrence of any complications. Comparing both imaging techniques, the following coronary veins were visualized (conventional angiography/mdct angiography) (Fig. 1): coronary sinus (7/7); great cardiac vein (7/7); middle cardiac vein (6/7); running in the posterior interventricular groove, left posterior vein (7/7); draining the inferior posterior wall of the left ventricle, left marginal vein (6/6); running along the free wall of the left ventricle, the anterior interventricular vein (7/7); and near the anterior descending artery and small cardiac veins (2/3) with direct drainage into the right atrium. For both techniques, the median coronary vein visibility was 2 (conventional angiography, mean 2.38 ± 0.70; MDCT angiography, 2.33 ± 0.67). Results are summarized in detail in Table 1 and Figure 2. With decreasing size and peripheral course of the vessel, the visibility of the cardiac veins decreases. Especially for visualization of the small cardiac veins draining directly into the right atrium, MDCT angiography was superior to conventional angiography. TABLE 1: Distribution of Visibility Grades of the Coronary Veins Coronary Sinus Angiography MDCT Angiography Visibility Grade (%) Visibility Grade (%) Target Visualized Mean Mean CS GCV MCV LPV LMV AIVV SCV Note Data are percentages of veins rated at each grade. CS = coronary sinus, GCV = great cardiac vein, MCV = middle cardiac vein, LPV = left posterior vein, LMV = left marginal vein, AIVV = anterior interventricular vein, SCV = small cardiac vein. Visibility Grade CS GCV MCV LPV LMV AIVV SCV Fig. 2 Average visibility grades of all cardiac veins. White bars indicate coronary sinus angiography, gray bars indicate MDCT angiography. CS = coronary sinus, GCV = great cardiac vein, MCV = middle cardiac vein, LPV = left posterior vein, LMV = left marginal vein, AIVV = anterior interventricular vein, SCV = small cardiac vein AJR:185, November 2005

4 Imaging the Cardiac Venous System In selective retrograde conventional angiography, vessel evaluation was sometimes hindered by insufficient contrast of the cardiac veins. Mainly the middle cardiac vein, with its orifice into the coronary sinus very close to the right atrium, was affected. Because of its anatomy, only a small amount of contrast material A C Fig year-old man with cardiac arrhythmias. RA = right atrium, RV = right ventricle, LV = left ventricle, CS = coronary sinus, GCV = great cardiac vein, MCV = middle cardiac vein. A D, Samples of different image displays in MDCT angiography compared with conventional angiography: A, axial image; B, multiplanar reformation; C, maximum intensity projection; and D, 3D volume rendering display. (Fig. 3 continues on next page) is delivered into the middle cardiac vein in retrograde perfusion angiography with selective intubation of the coronary sinus. In MDCT angiography, the visually determined optimum time of the R-R interval for image reconstruction for evaluation of the coronary venous system with fewest motion artifacts was 65% (range, 60 80%). Three-dimensional VRT images proved helpful for global orientation and vessel identification. However, detailed information on the venous anatomy and diameter measurements were provided by the axial slices, individually adapted MPRs, and MIPs (Fig. 3). B D AJR:185, November

5 Mühlenbruch et al. Diameter (mm) Pearson s correlation coefficient for vessel visibility was r = For evaluation of vessel diameter before measurement, an aberrance of 0.5 mm was considered acceptable for comparison of conventional angiography and MDCT angiography values. The average vessel diameter on conventional angiography was 3.98 ± 1.82 mm, and 4.18 ± 1.84 mm on MDCT angiography (Fig. 4). Equivalence of vessel diameter comparing conventional angiography and MDCT angiography could be shown with a 95% confidence interval inside the tolerated difference. A Bland-Altman plot of the paired vessel diameters is shown in Figure 5. Besides evaluation of the coronary venous system, MDCT angiography with the contrast bolus optimized for the coronary arteries also E Fig. 3 (continued) 52- year-old man with cardiac arrhythmias. RA = right atrium, RV = right ventricle, LV = left ventricle, CS = coronary sinus, GCV = great cardiac vein, MCV = middle cardiac vein. E, Conventional angiography, view: right anterior oblique 60. CS GCV MCV LPV LMV AIVV SCV Fig. 4 Average cardiac vein diameter comparing conventional angiography and MDCT angiography values. White bars indicate coronary sinus angiography, gray bars indicate MDCT angiography. CS = coronary sinus, GCV = great cardiac vein, MCV = middle cardiac vein, LPV = left posterior vein, LMV = left marginal vein, AIVV = anterior interventricular vein, SCV = small cardiac vein. allows for detailed analysis of the coronary arteries and the cardiac chambers. Overall, three high-grade stenoses were detected. In two patients, intact coronary bypass grafts were visualized; two patients showed impaired left ventricular function with wall thinning; and in two other patients, coronary artery disease could be excluded. Discussion The usefulness of electron beam CT for visualization of the coronary veins has already been shown [7]. In previous reports, excellent sensitivity and specificity of MDCT coronary angiography have been shown in detecting coronary artery stenoses or coronary bypass graft patency [6]. However, to the best of our knowledge there are no data re- garding the feasibility of dedicated examination of the coronary venous system using MDCT angiography in comparison with conventional angiography as the reference standard. Cardiac resynchronization therapy (CRT) acutely improves hemodynamics in patients with systolic heart failure and ventricular conduction delay [9]. It has been shown to reduce symptoms, increase exercise tolerance, and reduce hospitalization in such patients [10]. The implantation of a CRT pacemaker or defibrillator usually requires left ventricular stimulation, achieved either by direct epicardial lead placement via a limited lateral thoracotomy or, mainly, by a transvenous approach using the tributaries of the coronary sinus. Thus, the availability and location of cardiac veins for potential placement of a left ventricular lead should be assessed before implantation of a CRT device. Because the posterolateral left ventricular wall is usually the optimal location for pacing [11], attention is focused on the presence and availability of coronary veins on the posterolateral aspect of the left ventricle. Depending on the diameter and angle with the great cardiac vein, cannulating a specific left ventricular vein may be difficult. Thus, prior knowledge of venous anatomy may aid in anticipating the degree of difficulty and in selecting special equipment (e.g., steerable pacing guidewires) [7]. Furthermore, vessel size is an important criterion for selecting the target vein in procedures such as left ventricular pacemaker lead insertion. The results of this study prove that evaluation of the cardiac venous system is feasible using MDCT angiography, even with a scanning protocol optimized for the visualization of the coronary arteries. A good correlation of vessel visibility and diameter was shown. Remaining aberrances may have different reasons, including differences in the ways images display in conventional angiography and MDCT angiography. Vessel diameter in conventional angiography can only be assessed in a 2D projection. Although different imaging planes of the same vessel are addressed, the reviewer needs to be aware of the tendency of this imaging technique to underestimate the maximum vessel diameter [12]. In contrast, using MPRs of MDCT angiography with the image plane orthographic to the vessel course, the maximum vessel diameter can easily be measured. MDCT angiography may suffer from motion artifacts, although, in 1256 AJR:185, November 2005

6 Imaging the Cardiac Venous System Coronary Sinus Angiography MDCT Angiography (mm) SD 1.24 Mean SD Vessel Diameter Using Average of Combined Coronary Sinus Angiography and MDCT Angiography (mm) Fig. 5 The Bland-Altman analysis of the paired vessel diameters shows a mean deviation of 0.2 mm with lower and upper limits of agreement (dotted lines) of 1.63 and 1.24 mm (±1.96 SD), respectively. our study, image analysis was performed at the point of the R-R interval presenting with the fewest artifacts and substantial coronary vein filling. Systematic overestimation of the vessel diameter by use of MDCT angiography may be explained in that the vessel wall of the coronary vein is supposed to enhance with the use of contrast material and this was taken into account during the measurements, whereas conventional angiography only depicts the true vessel lumen. However, in conventional angiography, this vessel lumen might be dilated and its diameter overestimated by retrograde injection of contrast material. Compared with conventional angiography, MDCT angiography is less invasive and has a lower rate of complications. Besides increased acceptance of the procedure by the patient population, reduced hospital stays and cost-reduction may be expected. Cardiac MDCT angiography provides additional information on cardiac function and thoracic abnormalities and may replace other invasive procedures, in some cases even catheter-based coronary angiography. Technical improvements, including the introduction of new MDCT scanners with higher spatial and temporal resolution exceeding the temporal resolution of electron beam CT scanners, will lead to even better visualization of the coronary veins. In conclusion, MDCT angiography offers a reliable tool for evaluation of the coronary veins before interventional electrophysiological procedures, pacemaker lead placement, and other procedures and should be considered as an alternative diagnostic technique to invasive conventional angiography. References 1. Wen MS, Yeh SJ, Wang CC, King A, Lin FC, Wu D. Radiofrequency ablation therapy of the posteroseptal accessory pathway. Am Heart J 1996; 132: Kar S, Nordlander R. Coronary veins: an alternate route to ischemic myocardium. Heart Lung 1992; 21: Oesterle SN, Reifart N, Hayase M, et al. Catheterbased coronary bypass: a development update. Catheter Cardiovasc Interv 2003; 58: Ryden L, Tadokoro H, Sjoquist PO, et al. Pharmacokinetic analysis of coronary venous retroinfusion: a comparison with anterograde coronary artery drug administration using metoprolol as a tracer. J Am Coll Cardiol 1991; 18: Gerber TC, Kantor B, Keelan PC, Hayes DL, Schwartz RS, Holmes DR. The coronary venous system: an alternate portal to the myocardium for diagnostic and therapeutic procedures in invasive cardiology. Curr Interv Cardiol Rep 2000; 2: Giesler T, Baum U, Ropers D, et al. Noninvasive visualization of coronary arteries using contrast-enhanced multidetector CT: influence of heart rate on image quality and stenosis detection. AJR 2002; 179: Gerber TC, Sheedy PF, Bell MR, et al. Evaluation of the coronary venous system using electron beam computed tomography. Int J Card Imaging 2001; 17: Kalender WA, Schmidt B, Zankl M, Schmidt M. A PC program for estimating organ dose and effective dose values in computed tomography. Eur Radiol 1999; 9: Auricchio A, Stellbrink C, Block M, et al. Effect of pacing chamber and atrioventricular delay on acute systolic function of paced patients with congestive heart failure. Circulation 1999; 99: Cazeau S, Leclercq C, Lavergne T, et al. Effects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay: Multisite Stimulation in Cardiomyopathies (MUSTIC) Study Investigators. N Engl J Med 2001; 12: Koos R, Sinha AM, Markus K, et al. Comparison of left ventricular lead placement via the coronary venous approach versus lateral thoracotomy in patients receiving cardiac resynchronization therapy. Am J Cardiol 2004; 94: Chen SJ, Carroll JD. 3-D reconstruction of coronary arterial tree to optimize angiographic visualization. IEEE Trans Med Imaging 2000; 19: AJR:185, November