Stephen G. Quallich

Optimal contact forces to minimize cardiac perforations before, during, and/or after radiofrequency or cryothermal ablations

BACKGROUND Catheter perforations remain a major clinical concern during ablation procedures for treatment of atrial arrhythmias and may lead to life-threatening cardiac tamponade. Radiofrequency (RF) ablation alters the biomechanical properties of cardiac tissue, ultimately allowing for perforation to occur more readily. Studies on the effects of cryoablation on perforation force as well as studies defining the perforation force of human tissue are limited. OBJECTIVE The purpose of this study was to investigate the required force to elicit perforation of cardiac atrial tissue after or during ablation procedures. METHODS Effects of RF or cryothermal ablations on catheter perforation forces for both swine (n = 83 animals, 530 treatments) and human (n = 8 specimens, 136 treatments) cardiac tissue were investigated. RESULTS Overall average forces resulting in perforation of healthy unablated tissue were 406g ± 170g for swine and 591g ± 240g for humans. Post-RF ablation applications considerably reduced these forces to 246g ± 118g for swine and 362 ± 185g for humans (P <.001). Treatments with cryoablation did not significantly alter forces required to induce perforations. Decreasing catheter sizes resulted in a reduction in forces required to perforate the atrial wall (P <.001). Catheter perforations occurred over an array of contact forces with a minimum of 38g being observed. CONCLUSION The swine model likely underestimates the required perforation forces relative to those of human tissues. We provide novel insights related to the comparative effects of RF and cryothermal ablations on the potential for inducing undesired punctures, with RF ablation reducing perforation force significantly. These data are insightful for physicians performing ablation procedures as well as for medical device designers.

The Effects of Radiofrequency or Cryothermal Ablation on Biomechanical Properties of Isolated Human or Swine Cardiac Tissues

Changes in cardiac tissue properties following the application of various ablation modalities may lead to the development of an array of associated complications. The application of either radio frequency (RF) or cryothermal ablations will alter the biomechanical properties of various cardiac tissues in a differential manner; in some cases, this may be attributable to increased incidences of cardiac tamponade, pulmonary vein stenosis, and/or atrial-esophageal fistula. Thus, a greater understanding of the underlying changes in tissue properties induced by ablative therapies will ultimately promote safer and more efficacious procedures. The effects of applied RF or cryothermal energies on the biomechanical properties of the pulmonary vein, left atrial, or right atrial samples (n=369 ) were examined from fresh excised porcine (n=35) and donated human tissue (n=11). RF ablations were found to reduce the tensile strength of the porcine cardiac specimens (p<;0.05), and a similar trend was noted for human samples. Cryoablations did not have a significant impact on the tissue properties compared with the untreated tissue specimens. Locational and species differences were also observed in this experimental paradigm (p<;0.001). Incorporating these findings into cardiac device design and computational modeling should aid to reduce the risks of complications associated with tissue property changes resulting from cardiac ablative procedures.

Direct visualization of induced steam pops during radiofrequency ablation

Introduction Importantly, during clinical ablation procedures, the elicitation of elevated tissue temperatures may induce audible steam pops. Rapidly induced high endocardial tissue temperatures are considered to generate these events as a result of blood/tissue vaporizations. In addition, discrepancies between monitored catheter tip temperature and actual endocardial tissue temperature may be related to the unanticipated elicitation of steam pops. Ultimately, these induced tissue disruptions can have important clinical consequences. They even may result in perforations of the atrial wall and/or the release of tissue or air emboli from the affected tissues.

The benefits of the Atlas of Human Cardiac Anatomy website for the design of cardiac devices

This paper describes how the Atlas of Human Cardiac Anatomy website can be used to improve cardiac device design throughout the process of development. The Atlas is a free-access website featuring novel images of both functional and fixed human cardiac anatomy from over 250 human heart specimens. This website provides numerous educational tutorials on anatomy, physiology and various imaging modalities. For instance, the ‘device tutorial’ provides examples of devices that were either present at the time of in vitro reanimation or were subsequently delivered, including leads, catheters, valves, annuloplasty rings and stents. Another section of the website displays 3D models of the vasculature, blood volumes and/or tissue volumes reconstructed from computed tomography and magnetic resonance images of various heart specimens. The website shares library images, video clips and computed tomography and MRI DICOM files in honor of the generous gifts received from donors and their families.