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RadioGraphics 2007;27:1566-1567

EDUCATION EXHIBIT

Invited Commentary

Jürgen Rademaker, MD

Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, New York

I am pleased to have the opportunity to comment on the excellent article by Saremi and Krishnan in this issue of RadioGraphics (1). The article is an example of successful collaboration between radiologists (F.S.) and cardiologists (S.K.) in the rapidly evolving field of cardiac imaging (2–5). The article by Saremi and Krishnan is important for two reasons. First, it is a highly educational review for readers who want to deepen their general knowledge of cardiac imaging, with special emphasis on anatomic landmarks and variants and their clinical relevance. Second, the article provides a thorough introduction to the new field of cardiac imaging and ablation techniques (6–8) by reviewing important anatomic details that can be used for treatment planning.

The success of new ablation strategies for AF and other cardiac arrhythmias depends on the ability to place ablation lesions at predefined anatomic targets, such as the pulmonary vein ostia. Traditionally, navigation of catheters for electrophysiologic studies has been performed under fluoroscopic guidance, with placement of catheters in reproducible locations. During subsequent cardiac mapping, catheters track and stimulate signals in real time to help locate abnormal areas in the cardiac conduction system. Anatomic structures such as the left atrium and the pulmonary veins are not delineated with fluoroscopy because there is no contrast differentiation between these structures and the surrounding anatomy. CT scans such as those presented by Saremi and Krishnan are preinterventional static models used to help direct the mapping and ablation catheters to the appropriate sites. Proper understanding of the anatomy (1,9–12) enables the cardiac imager to obtain the specific information needed by the interventional cardiologist.

Recent reports (13,14) document the feasibility and development of catheter navigation and mapping by fusing fluoroscopic images with cardiac volume images derived from multisection CT and MR imaging data. Fluoroscopy remains the means by which the catheter is navigated from moment to moment, and the static cardiac images are not superimposed on the real-time fluoroscopic images. In the end, the clinical utility of these approaches must be determined by how well they guide therapy or whether, for example, mapping alone or mapping combined with echocardiographic imaging is more powerful. Triedman (15) and Triedman et al (16) correctly pointed out that structured clinical outcome studies are the most important criteria for evaluating these ablation techniques. Triedman also noted that the "ablation itself remains a spatially uncertain process" (15). Further improvements in the accuracy of visualization may not be clinically relevant because of the current inability to precisely control the size and shape of the ablation lesion (15). Posttreatment imaging is likely going to focus on complications such as stenoses, dissections, or perforations.


   References
Top
 References
 

  1. Saremi F, Krishnan S. Cardiac conduction system: anatomic landmarks relevant to interventional electrophysiologic techniques demonstrated with 64-Detector CT. RadioGraphics 2007;27(6): 1539–1567.[Abstract/Free Full Text]
  2. vanden Driesen RI, Slaughter RE, Strugnell WE. MR findings in cardiac amyloidosis. AJR Am J Roentgenol 2006;186:1682–1685.[Abstract/Free Full Text]
  3. Peters DC, Wylie JV, Hauser TH, et al. Detection of pulmonary vein and left atrial scar after catheter ablation with three-dimensional navigator-gated delayed enhancement MR imaging: initial experience. Radiology 2007;243:690–695.[Abstract/Free Full Text]
  4. Zeina AR, Odeh M, Blinder J, Rosenschein U, Barmeir E. Myocardial bridge: evaluation with MDCT. AJR Am J Roentgenol 2007;188:1069–1073.[Abstract/Free Full Text]
  5. Srichai MB, Hecht EM, Kim DC, Jacobs JE. Ventricular diverticula on cardiac CT: more common than previously thought. AJR Am J Roentgenol 2007;189:204–208.[Abstract/Free Full Text]
  6. Reddy VY, Malchano ZJ, Holmvang G, et al. Integration of cardiac magnetic resonance imaging with three-dimensional electroanatomic mapping to guide left ventricular catheter manipulation: feasibility in a porcine model of healed myocardial infarction. J Am Coll Cardiol 2004;44:2202–2213.[Abstract/Free Full Text]
  7. Sporton SC, Earley MJ, Nathan AW, Schilling RJ. Electroanatomic versus fluoroscopic mapping for catheter ablation procedures: a prospective randomized study. J Cardiovasc Electrophysiol 2004; 15:310–315.[CrossRef][Medline]
  8. Sra J, Narayan G, Krum D, Akhtar M. Registration of 3D computed tomographic images with interventional systems: implications for catheter ablation of atrial fibrillation. J Interv Card Electrophysiol 2006;16:141–148.[CrossRef][Medline]
  9. Jongbloed MR, Dirksen MS, Bax JJ, et al. Atrial fibrillation: multi–detector row CT of pulmonary vein anatomy prior to radiofrequency catheter ablation—initial experience. Radiology 2005;234: 702–709.[Abstract/Free Full Text]
  10. Kim YH, Marom EM, Herndon JE, McAdams HP. Pulmonary vein diameter, cross-sectional area, and shape: CT analysis. Radiology 2005; 235:43–49.[Abstract/Free Full Text]
  11. Marom EM, Herndon JE, Kim YH, McAdams HP. Variations in pulmonary venous drainage to the left atrium: implications for radiofrequency ablation. Radiology 2004;230:824–829.[Abstract/Free Full Text]
  12. Lacomis JM, Wigginton W, Fuhrman C, Schwartzman D, Armfield DR, Pealer KM. Multi–detector row CT of the left atrium and pulmonary veins before radio-frequency catheter ablation for atrial fibrillation. RadioGraphics 2003; 23(spec no):S35–S48.[Abstract/Free Full Text]
  13. Ector J, De Buck S, Adams J, et al. Cardiac three-dimensional magnetic resonance imaging and fluoroscopy merging: a new approach for electroanatomic mapping to assist catheter ablation. Circulation 2005;112:3769–3776.[Abstract/Free Full Text]
  14. Sra J, Krum D, Malloy A, et al. Registration of three-dimensional left atrial computed tomographic images with projection images obtained using fluoroscopy. Circulation 2005;112:3763–3768.[Abstract/Free Full Text]
  15. Triedman J. Virtual reality in interventional electrophysiology. Circulation 2005;112:3677–3679.[Free Full Text]
  16. Triedman JK, Alexander ME, Love BA, et al. Influence of patient factors and ablative technologies on outcomes of radiofrequency ablation of intraatrial reentrant tachycardia in congenital heart disease patients. J Am Coll Cardiol 2002;39:1827–1835.[Abstract/Free Full Text]

Authors’ Response

Farhood Saremi, MD and Subramaniam Krishnan, MD

Department of Radiological Sciences and Cardiology, Division of Cardiothoracic Imaging
Department of Medicine, Division of Cardiology, UCI Medical Center, Orange, California

One of the primary catalysts of the revolution in the treatment of cardiac arrhythmias has been the dramatic improvement in imaging technology. The consequent improvement in the understanding of the disease process and the arrhythmic substrate in the individual patient has translated into improved procedural outcomes in terms of higher success rates as well as enhanced safety. Accurate anatomic description of the heart and related vasculature requires that the radiologist interpreting the images, as well as the cardiologist and surgeon treating the patient, interact closely and "speak the same language." We thank Dr Rademaker for his insightful comments and believe that his editorial will improve awareness of the need for the radiologist and the cardiologist to closely interact and collaborate. In interventional electrophysiology, the role of the cardiac radiologist will continue to grow. The imaging specialist who is aware of the finer aspects of electrophysiologic procedures will be a key member of the team providing care for these patients. We hope that our article will help in some small way to make this happen.


Related Article

Cardiac Conduction System: Anatomic Landmarks Relevant to Interventional Electrophysiologic Techniques Demonstrated with 64-Detector CT
Farhood Saremi and Subramaniam Krishnan
RadioGraphics 2007 27: 1539-1565. [Abstract] [Full Text] [PDF]




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