Posts Tagged ‘Catheter ablation’

Ablation Techniques in Interventional Oncology

Author and Curator: Dror Nir, PhD

“Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes.”; WikipediA.

The use of ablative techniques in medicine is known for decades. By the late 90s, the ability to manipulate ablation sources and control their application to area of interest improved to a level that triggered their adaptation to cancer treatment. To date, ablation  is still a controversial treatment, yet steadily growing in it’s offerings to very specific cancer patients’ population.

The attractiveness in ablation as a form of cancer treatment is in the promise of minimal invasiveness, focused tissue destruction and better quality of life due to the ability to partially maintain viability of affected organs.  The main challenges preventing wider adaptation of ablative treatments are: the inability to noninvasively assess the level of cancerous tissue destruction during treatment; resulting in metastatic recurrence of the disease and the insufficient isolation of the treatment area from its surrounding.   This frequently results In addition, post-ablation salvage treatments are much more complicated. Since failed ablative treatment represents a lost opportunity to apply effective treatment to the primary tumor the current trend is to apply such treatments to low-grade cancers.

Nevertheless, the attractiveness of treating cancer in a focused way that preserves the long-term quality of life continuously feeds the development efforts and investments related to introduction of new and improved ablative treatments giving the hope that sometime in the future focused ablative treatment will reach its full potential.

The following paper reviews the main ablation techniques that are available for use today: Percutaneous image-guided ablation of bone and soft tissue tumours: a review of available techniques and protective measures.



Primary or metastatic osseous and soft tissue lesions can be treated by ablation techniques.


These techniques are classified into chemical ablation (including ethanol or acetic acid injection) and thermal ablation (including laser, radiofrequency, microwave, cryoablation, radiofrequency ionisation and MR-guided HIFU). Ablation can be performed either alone or in combination with surgical or other percutaneous techniques.


In most cases, ablation provides curative treatment for benign lesions and malignant lesions up to 3 cm. Furthermore, it can be a palliative treatment providing pain reduction and local control of the disease, diminishing the tumor burden and mass effect on organs. Ablation may result in bone weakening; therefore, whenever stabilization is undermined, bone augmentation should follow ablation depending on the lesion size and location.


Thermal ablation of bone and soft tissues demonstrates high success and relatively low complication rates. However, the most common complication is the iatrogenic thermal damage of surrounding sensitive structures. Nervous structures are very sensitive to extremely high and low temperatures with resultant transient or permanent neurological damage. Thermal damage can cause normal bone osteonecrosis in the lesion’s periphery, surrounding muscular atrophy and scarring, and skin burns. Successful thermal ablation requires a sufficient ablation volume and thermal protection of the surrounding vulnerable structures.

Teaching points

Percutaneous ablations constitute a safe and efficacious therapy for treatment of osteoid osteoma.

Ablation techniques can treat painful malignant MSK lesions and provide local tumor control.

Thermal ablation of bone and soft tissues demonstrates high success and low complication rates.

Nerves, cartilage and skin are sensitive to extremely high and low temperatures.

Successful thermal ablation occasionally requires thermal protection of the surrounding structures.

For the purpose of this chapter we picked up three techniques:

Radiofrequency ablation

Straight or expandable percutaneously placed electrodes deliver a high-frequency alternating current, which causes ionic agitation with resultant frictional heat (temperatures of 60–100 ˚C) that produces protein denaturation and coagulation necrosis [8]. Concerning active protective techniques, all kinds of gas dissection can be performed. Hydrodissection is performed with dextrose 5 % (acts as an insulator as opposed to normal saline, which acts as a conductor). All kinds of skin cooling, thermal and neural monitoring can be performed.


Microwave ablation

Straight percutaneously placed antennae deliver electromagnetic microwaves (915 or 2,450 MHz) with resultant frictional heat (temperatures of 60–100 ˚C) that produces protein denaturation and coagulation necrosis [8]. Concerning active protective techniques, all kinds of gas dissection can be performed, whilst hydrodissection is usually avoided (MWA is based on agitation of water molecules for energy transmission). All kinds of skin cooling, thermal and neural monitoring can be performed.

Percutaneous ablation of malignant metastatic lesions is performed under imaging guidance, extended local sterility measures and antibiotic prophylaxis. Whenever the ablation zone is expected to extend up to 1 cm close to critical structures (e.g. the nerve root, skin, etc.), all the necessary thermal protection techniques should be applied (Fig. 3).


a Painful soft tissue mass infiltrating the left T10 posterior rib. b A microwave antenna is percutaneously inserted inside the mass. Due to the proximity to the skin a sterile glove filled with cold water is placed over the skin. c CT axial scan 3 months

Irreversible Electroporation (IRE)

Each cell membrane point has a local transmembrane voltage that determines a dynamic phenomenon called electroporation (reversible or irreversible) [16]. Electroporation is manifested by specific transmembrane voltage thresholds related to a given pulse duration and shape. Thus, a threshold for an electronic field magnitude is defined and only cells with higher electric field magnitudes than this threshold are electroporated. IRE produces persistent nano-sized membrane pores compromising the viability of cells [16]. On the other hand, collagen and other supporting structures remain unaffected. The IRE generator produces direct current (25–45 A) electric pulses of high voltage (1,500–3,000 V).

Lastly we wish to highlight a method that is mostly used on patients diagnosed at intermediate or advanced clinical stages of Hepatocellular Carcinoma (HCC); transarterial chemoembolization  (TACE)

“Transcatheter arterial chemoembolization (also called transarterial chemoembolization or TACE) is a minimally invasive procedure performed in interventional radiology  to restrict a tumor’s blood supply. Small embolic particles coated with chemotherapeutic agents are injected selectively into an artery directly supplying a tumor. TACE derives its beneficial effect by two primary mechanisms. Most tumors within the liver are supplied by the proper hepatic artery, so arterial embolization preferentially interrupts the tumor’s blood supply and stalls growth until neovascularization. Secondly, focused administration of chemotherapy allows for delivery of a higher dose to the tissue while simultaneously reducing systemic exposure, which is typically the dose limiting factor. This effect is potentiated by the fact that the chemotherapeutic drug is not washed out from the tumor vascular bed by blood flow after embolization. Effectively, this results in a higher concentration of drug to be in contact with the tumor for a longer period of time. Park et al. conceptualized carcinogenesis of HCC as a multistep process involving parenchymal arterialization, sinusoidal capillarization, and development of unpaired arteries (a vital component of tumor angiogenesis). All these events lead to a gradual shift in tumor blood supply from portal to arterial circulation. This concept has been validated using dynamic imaging modalities by various investigators. Sigurdson et al. demonstrated that when an agent was infused via the hepatic artery, intratumoral concentrations were ten times greater compared to when agents were administered through the portal vein. Hence, arterial treatment targets the tumor while normal liver is relatively spared. Embolization induces ischemic necrosis of tumor causing a failure of the transmembrane pump, resulting in a greater absorption of agents by the tumor cells. Tissue concentration of agents within the tumor is greater than 40 times that of the surrounding normal liver.”; WikipediA

A recent open access research paper: Conventional transarterial chemoembolization versus drug-eluting bead transarterial chemoembolization for the treatment of hepatocellular carcinoma is discussing recent clinical approaches  related to this techniques.



To compare the overall survival of patients with hepatocellular carcinoma (HCC) who were treated with lipiodol-based conventional transarterial chemoembolization (cTACE) with that of patients treated with drug-eluting bead transarterial chemoembolization (DEB-TACE).


By an electronic search of our radiology information system, we identified 674 patients that received TACE between November 2002 and July 2013. A total of 520 patients received cTACE, and 154 received DEB-TACE. In total, 424 patients were excluded for the following reasons: tumor type other than HCC (n = 91), liver transplantation after TACE (n = 119), lack of histological grading (n = 58), incomplete laboratory values (n = 15), other reasons (e.g., previous systemic chemotherapy) (n = 114), or were lost to follow-up (n = 27). Therefore, 250 patients were finally included for comparative analysis (n = 174 cTACE; n = 76 DEB-TACE).


There were no significant differences between the two groups regarding sex, overall status (Barcelona Clinic Liver Cancer classification), liver function (Child-Pugh), portal invasion, tumor load, or tumor grading (all p > 0.05). The mean number of treatment sessions was 4 ± 3.1 in the cTACE group versus 2.9 ± 1.8 in the DEB-TACE group (p = 0.01). Median survival was 409 days (95 % CI: 321–488 days) in the cTACE group, compared with 369 days (95 % CI: 310–589 days) in the DEB-TACE group (p = 0.76). In the subgroup of Child A patients, the survival was 602 days (484–792 days) for cTACE versus 627 days (364–788 days) for DEB-TACE (p = 0.39). In Child B/C patients, the survival was considerably lower: 223 days (165–315 days) for cTACE versus 226 days (114–335 days) for DEB-TACE (p = 0.53).


The present study showed no significant difference in overall survival between cTACE and DEB-TACE in patients with HCC. However, the significantly lower number of treatments needed in the DEB-TACE group makes it a more appealing treatment option than cTACE for appropriately selected patients with unresectable HCC.


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Percutaneous Endocardial Ablation of Scar-Related Ventricular Tachycardia

Reporter: Aviva Lev-Ari, PhD, RN

UPDATED on 11/15/2013

Atrial Fibrillation Catheter Ablation Versus Surgical Ablation Treatment (FAST)

A 2-Center Randomized Clinical Trial

  1. Lucas V.A. Boersma, MD, PhD, FESC;
  2. Manuel Castella, MD, PhD;
  3. WimJan van Boven, MD;
  4. Antonio Berruezo, MD;
  5. Alaaddin Yilmaz, MD;
  6. Mercedes Nadal, MD;
  7. Elena Sandoval, MD;
  8. Naiara Calvo, MD;
  9. Josep Brugada, MD, PhD, FESC;
  10. Johannes Kelder, MD;
  11. Maurits Wijffels, MD, PhD;
  12. Lluís Mont, MD, PhD, FESC

+Author Affiliations

  1. From the Departments of Cardiology (L.V.A.B., J.K., M.W.) and Cardiothoracic Surgery (W.J.v.B., A.Y.), St. Antonius Hospital, Nieuwegein, the Netherlands, and Thorax Institute, Hospital Clinic, University of Barcelona, Barcelona, Catalonia, Spain (M.C., A.B., M.N., E.S., N.C., J.B., L.M.).
  1. Correspondence to Lucas V.A. Boersma, MD, PhD, FESC, Cardiology Department, St. Antonius Hospital, PO 2500, Nieuwegein, Netherlands.


Background—Catheter ablation (CA) and minimally invasive surgical ablation (SA) have become accepted therapy for antiarrhythmic drug–refractory atrial fibrillation. This study describes the first randomized clinical trial comparing their efficacy and safety during a 12-month follow-up.

Methods and Results—One hundred twenty-four patients with antiarrhythmic drug–refractory atrial fibrillation with left atrial dilatation and hypertension (42 patients, 33%) or failed prior CA (82 patients, 67%) were randomized to CA (63 patients) or SA (61 patients). CA consisted of linear antral pulmonary vein isolation and optional additional lines. SA consisted of bipolar radiofrequency isolation of the bilateral pulmonary vein, ganglionated plexi ablation, and left atrial appendage excision with optional additional lines. Follow-up at 6 and 12 months was performed by ECG and 7-day Holter recording. The primary end point, freedom from left atrial arrhythmia >30 seconds without antiarrhythmic drugs after 12 months, was 36.5% for CA and 65.6% for SA (P=0.0022). There was no difference in effect for subgroups, which was consistent at both sites. The primary safety end point of significant adverse events during the 12-month follow-up was significantly higher for SA than for CA (n=21 [34.4%] versus n=10 [15.9%]; P=0.027), driven mainly by procedural complications such as pneumothorax, major bleeding, and the need for pacemaker. In the CA group, 1 patient died at 1 month of subarachnoid hemorrhage.

Conclusion—In atrial fibrillation patients with dilated left atrium and hypertension or failed prior atrial fibrillation CA, SA is superior to CA in achieving freedom from left atrial arrhythmias after 12 months of follow-up, although the procedural adverse event rate is significantly higher for SA than for CA.

Clinical Trial Registration—URL: Unique identifier:NCT00662701.

Key Words:


 A single-center experience of clinical and electrophysiologic outcomes of patients undergoing percutaneous endocardial ablation of scar-related Ventricular Tachycardia (VT) is reported in

IMAJ Isr Med Assoc J 2010; 12: 667-670.

 Catheter ablation can control or prevent recurrent ischemic VT and reduce incidence of implantable cardioverter defibrillator (ICD) therapy. The ablation can be done during VT in patients with stable VTs or during sinus rhythm in patients with unstable unmappable VTs by targeting the scar border using electroanatomic substrate mapping. VT ablation should be offered to ischemic patients with recurrent uncontrolled VT. Radiofrequency ablation of VT in patients with ischemic cardiomyopathy was proposed to treat and control recurrent VT

J Cardiovasc Electrophys 2005; 16(Suppl 1): S59-70.

Curr Opin Cardiol 2005; 20: 42-7.

An experience with VT ablation in patients with ischemic cardiomyopathy using the electroanatomic mapping system (CARTO) was presented in

Circulation 1997; 95: 1611-22

There are several reasons for the limited success of ischemic VT ablation. Ventricular scars are not electrically homogenous. They are composed of variable regions of dense fibrosis that create conduction block and surviving myocyte bundles with interstitial fibrosis and diminished coupling, which produce circuitous slow conduction paths that promote reentry

Circulation 1993; 88: 915-26.

Repeated programmed stimulation typically induces more than one monomorphic VT. Multiple VTs can be due to different circuits in widely disparate areas of scar, different axis from the same region of the scar, or changes in activation remote from the circuit due to functional regions of block

Circulation 2007; 115: 2750-60.

Catheter ablation using conventional techniques are suitable for stable VT. VT reentry circuit can be defined using electroanatomic mapping (CARTO) only during stable and tolerable tachycardia. However, many patients with reduced ejection fraction secondary to coronary heart disease have unstable VTs. These patients do not tolerate sustained VT or rapid pacing. Thus, electric or pace mapping is not available in most cases (unmappable VT with catheter technique). In these cases, scar mapping and ablation can be done only during sinus rhythm using the CARTO system

IMAJ Isr Med Assoc J 2007; 9: 260-4.

Radiofrequency catheter ablation of ventricular tachycardia in the setting of ischemic cardiomyopathy has emerged recently as a useful adjunctive therapy to ICD. Scar related reentrant ventricular tachycardia is the most common underlying mechanism of sustained monomorphic VT in patients with ischemic heart disease.

Limitations of Alternative Treatment Methods:

1.            Recurrent ICD shocks have had physiological and psychological side effects.

2.            Antiarrythmic drugs are used to reduce incidence of ICD therapy, but their role in reducing mortality is not proven. In addition, these drugs have important side effects including pro-arrythmic effect and worsening of heart failure status.

Conclusions: Ablation of ischemic VT using electroanatomic scar mapping is feasible, has an acceptable success rate and should be offered for ischemic patients with recurrent uncontrolled VT.


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Curr Opin Cardiol 2005; 20: 42-7.

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