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JACC CardioOncol
JACC CardioOncol
JACC: CardioOncology
2666-0873
Elsevier

S2666-0873(24)00145-5
10.1016/j.jaccao.2024.04.001
Original Research
Editorial Comment
Cardiac Tumors and Innovations in Local Therapies
Blazing New Trails
Markman Timothy M. MD timothy.markman@pennmedicine.upenn.edu
a∗
Plastaras John P. MD, PhD b
a Department of Medicine, Division of Cardiovascular Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
b Department of Radiation Oncology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
∗ Address for correspondence: Dr Timothy M. Markman, University of Pennsylvania, 1 Convention Avenue, Philadelphia, Pennsylvania 19104, USA. timothy.markman@pennmedicine.upenn.edu
30 4 2024
8 2024
30 4 2024
6 4 572574
© 2024 The Authors
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Corresponding Author

Key Words

cardiac masses
echocardiography
treatment
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pmcCardiac tumors are rare but can lead to a myriad of therapeutic challenges stemming from their location within the heart. Although these tumors can be found incidentally or may cause constitutional symptoms, cardiac-specific manifestations are the most concerning. Thromboembolism from the tumor can result in pulmonary or systemic infarcts with right- or left-sided tumors. Depending on the location of the tumor, the obstruction of flow, interference with normal valvular function, or promotion of cardiac arrhythmias can cause dyspnea, angina, syncope, or sudden death. When the patient is a suitable candidate, surgical resection is the ideal treatment. Removal of a primary cardiac tumor with negative margins can be curative. Additionally, damage to the surrounding structures such as the valve apparatus can be repaired or replaced if necessary, theoretically restoring normal function. Unfortunately, surgical resection is often limited by patient and anatomical factors that affect the technical feasibility of the procedure or suggest an unacceptably high procedural risk. Chemotherapy, alone or in combination with other local therapies, can be a valuable tool for certain malignant tumors. However, these regimens can similarly be restricted by cardiac and systemic toxicity. Advancing technologies have allowed stereotactic body radiotherapy (SBRT) to be used for cardiac targets, including tumors and aberrant conduction targets for the treatment of ventricular arrhythmias.1, 2, 3 Although there remain unknowns about the efficacy and safety of this approach, it highlights a growing familiarity with radiation to beating hearts with substantial therapeutic potential. Despite this range of multimodal therapeutic approaches, the limitations associated with each are notable. There remains a need for innovative therapies.

In this issue of JACC: CardioOncology, Huang et al4 address this challenging clinical scenario and describe a novel approach to radiofrequency (RF) ablation of cardiac tumors. They present a series of 5 subjects with cardiac tumors that recurred despite surgical resection or were not surgical candidates because of the tumor location. The novel transapical radiofrequency ablation for cardiac tumors (TARFACT) procedure was performed under general anesthesia after extensive preprocedural imaging to characterize the mass. Real-time transthoracic echocardiography was used to guide insertion of an 18-G biopsy needle via a percutaneous, transthoracic approach. Once the needle reached the tumor, a biopsy was taken; a 17-G RF electrode needle was inserted into the tumor, and energy was applied from 20 to 130 W until 150% of the baseline impedance was reached, a markedly different approach from that used for cardiac RF for arrhythmias in which lower power is used and relatively modest impedance reduction is targeted. After a 15-minute hibernation period, this application was repeated on average 6 times with the placement being adjusted in an attempt to cover the entire tumor mass. After ablation, the needle was removed, and manual pressure was held briefly on the puncture site. There were no procedure-related deaths, and no subject developed a pericardial effusion requiring intervention. Two subjects developed ventricular arrhythmias during ablation, 1 of which required cardioversion. During a median follow-up of 9 months, all subjects had improvements in heart failure symptoms, and there was a measurable effect on tumor size by transthoracic echocardiography. The authors are to be commended for undertaking a novel, invasive approach to treat this devastating condition.

RF ablation for the local treatment of noncardiac tumors relies on thermal injury delivered via a needle inserted into the tumor tissue that delivers an alternating current between the electrode and a dispersive skin electrode. The subsequent heating is felt to generate coagulation necrosis of the tumor tissue because the local temperatures reaches 60 °C with local temperatures able to exceed 100 °C.5 Although RF ablation can control small tumors (<2 cm), it may be less effective than SBRT, potentially because of the inability to cover an adequate surface area when individual lesions likely do not extend significantly beyond 1 cm from the needle.6 This may be especially true when delivered adjacent to the blood pool, which likely acts as a “heat sink,” reducing the temperature rise in the adjacent tissue. Given the increasing comfort with SBRT in the heart for both arrhythmias and cardiac tumors, the relative merits should be considered when applying the findings from Huang et al4 to patients who may be candidates for either approach. Although both SBRT and RF ablation offer the ability to treat co-occurring ventricular arrhythmias arising from tumors, an invasive approach such as RF ablation uniquely affords an opportunity for tissue biopsy. Although these preliminary data suggest that arrhythmia from an adjacent tumor may be affected by RF applied to the tumor, the ability to safely deliver RF to the myocardium with this approach is uncertain.

Understanding the implications of these findings requires context from the use of RF ablation for noncardiac tumors but also from a growing experience with RF ablation in the heart for cardiac arrhythmias. RF ablation has undergone significant evolution in its application as a treatment for cardiac arrhythmias. Initially used as a method to selectively eliminate accessory atrioventricular pathways causing supraventricular tachycardia, it has since seen remarkable advancements in technology and procedural techniques. Innovations such as irrigated tip catheters, electroanatomic mapping systems, and real-time monitoring capabilities such as intracardiac echocardiography have greatly enhanced precision, efficacy, and safety during ablation procedures. These developments have not only improved outcomes for patients with various types of arrhythmias but also have expanded the scope of treatable conditions, including complex atrial and ventricular arrhythmias previously deemed inoperable. As a result, RF ablation stands as a cornerstone therapy in the management of cardiac arrhythmias, offering patients a minimally invasive and highly effective option for restoring normal heart rhythm and improving quality of life.

RF technology has achieved this level of safety and efficacy through careful attention to the potential risks associated with RF energy in the heart. The application of TARFACT or any related therapy should carefully be adopted to these lessons. RF for arrhythmias similarly works by creating thermal injury with a goal of affecting only abnormal myocardial tissue, although often accepting damage to a normal myocardium depending on the ablation strategy. RF ablation has evolved through the use of various sized electrode tips and the application of continuous irrigation with attempts to minimize the risk for the formation of coagulum, thromboembolism, and the creation of potentially catastrophic myocardial “stem pops” caused by elevated tissue temperatures and the production of steam.7 Continuous irrigation allows for cooling at the tip of the electrode-myocardial interface, displacing the maximum temperature several millimeters into the tissue and allowing continuous RF delivery and deeper, safer lesions.

When RF is performed in the heart, injury to normal myocardial tissue is minimized but is also accepted as inevitable in certain situations, such as with the creation of a linear lesion set to stop a re-entrant atrial flutter or when ventricular arrhythmias arise from abnormal midmyocardial substrate that is surrounded by normal tissue. When RF energy is delivered to normal tissue, the risks described previously, especially the potential for the creation of steam, is exaggerated. Additionally, there is significant proarrhythmic potential in this case because new substrate can be created, promoting arrhythmia development. For example, with extensive atrial ablation for atrial fibrillation, de novo atrial flutters can easily result.8 Similarly, ablation of the existing substrate can render an existing, rare arrhythmia incessant because of the modification but not the elimination of conduction.

In this series of 5 patients undergoing TARFACT, 2 developed ventricular arrhythmias during ablation. This is highly suggestive of heating of nearby myocardial tissue, which is a commonly observed phenomenon during RF enhancing automaticity during ablation. The importance of this observation cannot be overstated. Although guided by imaging and an understanding of the biophysics of RF applied in other tumor types, there was almost certainly inadvertent myocardial injury in these patients. Although not surprising, it necessitates that any application of RF for cardiac tumors consider all of the risks faced by electrophysiologists, especially the potential for thromboembolism, injury to RF-sensitive adjacent conduction system, and the creation of proarrhythmic substrate.

The findings presented here are novel, and the authors should be commended for their field-advancing work. Although surgical resection offers the greatest promise for cure and the restoration of normal cardiac function for patients with suitable cardiac tumors, we should continue to investigate alternative therapies, including SBRT and RF ablation. RF holds considerable promise. Ongoing innovation should emphasize the need to balance efficacy and safety with cardiac electrophysiology strategies including the application of real-time rhythm, conduction, and lesion monitoring; titration of temperature and power; and management of complications.

Funding Support and Author Disclosures

Dr Markman has received consulting fees from Biosense Webster, Abbott, Boston Scientific, and Medtronic. Dr Plastaras has served on an Advisory Board for Ion Beam Applications.

The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
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