Catheter Ablation 101

Sirin Apiyasawat, MD

Ramathibodi Hospital

Outline

• Radiofrequency ablation

– Basic concept

– Complications

• New modalities

• Where & when to ablate

• Qs & As

Before Radiofrequency…

• 160-360J monophasic shock• On average, >2 shocks were

delivered to achieve complete heart block

• 8/136 (5.9%) died 1-32 days after• Causes of death

• Polymorphic VT• VF• Heart Failure

Evans et al. Circulation 1991, 84:1924-1937.

What is Radiofrequency?

Electromagnetic Radiation Energy that travels in wave

Same wavelength range (1 mm to 100 km) as lightning and AM/FM radio

Electromagnetic Spectrum

How does RF heat things up?

Resistive Heating or Joule Heating

RF Lesion

Pathology Lesion

Shpun et al. Circulation. 1997;96:2016-2021.

Radiofrequency Ablation

V= IRPower (watt) = I∙V = 𝑉2

𝑅

Lesion is formed by direct electrical heating (resistive heating) and passive (conductive) heating of contiguous tissue.

Biophysics of RF Ablation

Current Density = 𝐼

4¶𝑟2

Tissue Temperature falls as the distance from the electrode grows

Wayne et al. Circulation. 1994;89:2390-2395.

50°C Isotherm Line of irreversible injury which determines the boundary of the lesion

Lesion Size vs. Electrode Length

4-mm catheter8-mm catheter 12-mm catheter

Langberg et al. Circulation 1993;88:245-249.

Power and Time

Lesion Size was determined by power level and exposure duration.Wittkampf et al. Circulation 1989:80:962-968.

Temperature

Nakagawa et al. Circulation. 1995;91:2264-2273.

Lesion Size correlates with Tissue Temperature BUT…

Boiling, Charring, and Popping

Sudden rise in impedance due to coagulum coating at the tip of the catheter

Haines & Verow. Circulation 1990, 82:1034-1038.

Langberg et al.Circulation 1992, 86:1469-1474.

Temperature vs. Power Control

Nakagawa et al. Circulation. 1995;91:2264-2273.

Power-controlled

Temp-controlled

Cooling Effect

P<0.05 for lesion size between apex vs. septum vs. free wall

Peterson et al. Circulation. 1999;99:319-325.

Lesion Size depends on…

Power Directly proportional to lesion size

Ablation electrode temperature Directly proportional to lesion size

Duration of energy delivery Monoexponential relation to lesion size

Ablation circuit impedance Direct effects from altering delivered power

Electrode-tissue contact pressure Directly proportional to lesion size

Electrode radius Directly proportional to lesion size

Blood flow- Over electrode-tissue interface- Intramyocardial

Reduces lesion size with fixed energy deliveryPotentially prevent transmural lesion formation

Tissue properties Smaller lesion in scar

Huang & Wood. Catheter Ablation for Arrhythmias. 2006

What to monitor during RFA?

Setting: Power, TemperatureMonitoring: Power, Temperature, Impedance

Charring

Overheating & Popping

Sudden burst into “popping” followed by a transmural lesion (white arrow)

Ren JF, et al. Practical Intracardiac Echocardiography in Electrophysiology. 2006.

Pathological Lesions

Good Lesion

Over Heating

Complications: Perforation

Atrio-Esophageal Fistula

• Rare (incidence = 0.05%) but deadly.•Occurs 3-5 days after ablation that involves posterior wall of left atrium.• Symptoms: sepsis, embolic stroke.• Rapid diagnosis and intervention is critical.

Pappone et al. Circulation.2004;109:2724-2726.

Pulmonary Vein Stenosis

Symptoms: Dyspnea, cough, hemoptysis, chest painInvestigations: CT Angiography, V/Q ScanGold Standard: Angiogram

Prieto et al. Heart Rhythm 2010.

Efficacy of Ablation

Fatal Outcome in Catheter Ablation for AF

Death 32/32,569 (0.1%)

Tamponade 8

Stroke 5

Massive Pneumonia 2

MI 1

Sepsis 1

Arrhythmia 1

Extra PV perforation 1

Esophageal Perforation 1

Incidence of intra & post procedure DeathData from 32 569 patients underwent catheter ablation for AF between ‘95 and ’06 from 162 center worldwide

Capato et al. J Am Coll Cardiol. 2009 May 12;53(19):1798-803.

Issue during Ablation

• Char Formation at the Tip of the Catheter

– Embolic Event esp. Left Side Ablation.

– Heparin (ACT ~300)

• Perforation, Cardiac Tamponade

• Heart Block

• Arrhythmias

• Pain

Issue after ablation

• Cardiac Tamponade

• Pericarditis

• Groin complications

C r y o a b l a t i o n

Cryoablation- Preserve underlying tissue architecture.- Minimal thrombus formation.

Cryo

RF

Khairy et al. Circulation 2003, 107:2045-2050

Hi-Intensity Focus Ultrasound (HIFU)

• Focus Ultrasound• No direct tissue contact• Tissue damage caused by heat, not tissue disruption

Microwave

• No direct contact• Better penetration

Tse et al. PACE 2009; 32:201–208.

Laser

Gerstenfeld et al. J Interv Card Electrophysiol (2010 ) 29:1 –9

Paroxysmal Supraventricular Tachycardia

Atrioventricular Reentrant Tachycardia (AVNRT)

Koch’s Triangle• Coronary Sinus (CS)• Tendon of Todaro*• Tricuspid Ring#

Fast Pathwayapex of triangleJunction between AVN & His

Slow Pathwaymiddle or lower part of trianglenear the os of CS

*#

Nakagawa & Jackman. Circulation. 2007;116:2465-2478.

Atrioventricular Reentrant Tachycardia (AVNRT)

Slow Fast

His

CS Os

CS

Tricuspid Annulus

Tendon of Todaro

Slow Pathway

Fast Pathway

RV

His CS

RV

Tendon of Todaro

Fast Pathway

Slow Pathway

Koch Triangle in Ablation of AVNRT

H H H H H H HV V V V V V V

Junctional Rhythm during ablation

‘Typical’ Atrial Flutter- Cavo-tricuspid isthmus dependent- Saw-tooth appearance on ECG- Macroreentry

RA activation map during atrial flutter

The Circuit

Lee et al. Catheter ablation of atrial arrhythmias: state of the art. Lancet 2012; 380: 1509-19.

Prox

Distal

Halo

Prox

Distal

WPW

Ablation SiteII

aVF

V1

hRA

HIS d

RVa

CS7,8CS5,6

CS3,4CS1,2

HIS pHIS m

ABL d

ABL p

ABLuni

* * *

Post AblationII

aVF

V1hRA

HIS d

RVa

CS7,8CS5,6

CS3,4CS1,2

HIS p

HIS m

ABL d

ABL p

Acute AF

Atrial Ectopy ↑Trigger Activity ↑

Spontaneous Calcium

Release ↓

Triggers

Koebe & Kirchhoff. Europace2008.10:433–437.

Nishida et al. JACC 2014. 64(8):823-31.

Pulmonary Vein IsolationAntiarrhythmic Agents

Autonomic denervation

Fibrosis

Conduction Slowing

Preformed reentry circuit

Chronic AF

Structural Remodelling

Wavelength ↓

Ion currents altered ↓

Effective refractory period ↓

Electrical Remodelling

AF

Antiarrhythmic AgentsEarly Termination of AF

- MAZE Procedure- Linear Ablation- Complex Fractionated Electrogram guided ablation- Autonomic denervation

Pulmonary Vein Isolation (PVI)

From Segmental to Antral Isolation

Segmental ostial isolationHigh incidence of PV stenosis (up to 20%)

Circumferential or Antral isolationIncidence of PV stenosis is low (<3%)

Saad et al. Circulation.2003;108:3102-3107.

Complex Fractionated Electrogram(CFAE)

Continuous deflection of a prolonged activation complex over a 10-s recording period

Atrial electrogram with a very short cycle length (≤ 120 ms) over a 10-s recording period

Nademanee et al. J Am Coll Cardiol 2004;43:2044–53.

Common Sites: Pulmonary veins, Interatrial septum, LA roof, Mitral annulus, and CS Os.

Additional Line

In patients with persistent AF, additional roof and mitral annulus line to PVI improved survival free from AF when compared to PVI alone (69% vs. 20% at 487 days)

(Willems et al. Eur Heart J. 2006;27:2871–2878).

Role of Autonomic Nervous System

Some of PV firings can be induced by stimulation of intrinsic cardiac autonomic nervous system.

Patterson et al. Heart Rhythm 2005;2:624 – 631.

An 18-year-old athlete has a history of infrequent episodes of a

narrow complex tachycardia that have previously been

terminated with adenosine. He is intolerant of beta-blockers, has

a delta wave with a large dominant R wave (right bundle pattern)

in lead V1, and is recommended radiofrequency ablation.

In this context, the patient can be counseled with information on

which of the following?

A. 5-10% chance of damage to the AV node with a 97% chance of success.

B. <2% change of requiring a permanent pacemaker, and a >95% success rate.

C. <1% chance of AV nodal damage, and an 80% chance of success.

D. 0% chance of ablation on the left side, with a >95% chance of success.

A 18-year-old man is referred for ECG abnormalities following a routine physical

examination before joining the college baseball team. He denies any sensation of

palpitations or fainting. He is on no medications and has no allergies. There is no

family history of sudden cardiac death. His blood pressure in the clinic is 95/60 mm

hg and heart rate is 80bpm. The cardiac and pulmonary examination is

unremarkable. An ECG is performed.

Which of the following

investigations are required?

a) Electrophysiology study

b) Holter monitor

c) Exercise treadmill test

d) Echocardiogram

e) No further investigations

Management of

asymptomatic young

patients (8-21 years) with

WPW pattern

SPERRI = shortest preexcited RR interval

Consider ablation in ASYMPTOMATIC WPW if…- High risk- Participating in moderate-high

level of competitive sports- Presence of structural heart

disease- Low risk and favorable location

2012 PACES/HRS Expert Consensus Statement on Asymptomatic Young Patient With WPW Pattern

A 58-year-old man is referred to you for evaluation of new-onset

heart failure symptoms. He was well until approximately 3

months ago, when he developed progressive dyspnea on

exertion. A stress test was normal, except for frequent PVCs that

increased with exercise. Echocardiography showed global LV

dysfunction, with an ejection fraction of 30%. Beta-blockers and

angiotensin-converting enzyme inhibitors were started, but

symptoms continue. There is no family history of heart failure.

Which of the following would be the most appropriate treatment

of his LV dysfunction?

A. Addition of spironolactone to the medical regimen.

B. Catheter ablation of the PVCs.

C. Cardiac catheterization and intervention as appropriate.

D. Uptitration of beta-blockers.

E. Addition of amiodarone to the medical regimen.

A 60-year-old man has been recently diagnosed with paroxysmal atrial fibrillation

and comes to you for further evaluation. Five years ago, he underwent dual-chamber

pacemaker implantation for intermittent high-grade atrioventricular (AV) block. His

other past history includes hypertension and hyperlipidemia. His medications at

present include aspirin 81 mg daily, lisinopril 10 mg daily, metoprolol 50 mg twice

daily, and simvastatin 40 mg nightly. Upon routine interrogation of his pacemaker, he

is found to be in atrial fibrillation by the detection of mode switching about 10% of

the time. The average ventricular rate in atrial fibrillation is 80-90 bpm. He is unaware

of these events.

With regard to management of atrial fibrillation, which of the following would you

advise?

A. Flecainide.

B. Sotalol.

C. Radiofrequency ablation.

D. Dronedarone.

E. No change in therapy.

A 57-year-old man calls your office complaining of malaise and a

fever of 102.5°F, 2 weeks after a catheter-based pulmonary vein

isolation for the treatment of paroxysmal atrial fibrillation. He

admits to some pain on swallowing for the past 3-4 days.

Which of the following is the most appropriate next step in his

management?

A. One-week treatment with Keflex 500 mg four times daily as an outpatient.

B. One-month treatment of nystatin three times daily as an outpatient.

C. Emergency room visit and urgent upper endoscopy.

D. Emergency room visit and urgent CT scan of chest.

E. Emergency room visit and treatment with intravenous tissue plasminogen activator.

Conclusions

• Catheter ablation for cardiac arrhythmia can be done using different modalities including radiofrequency, cryothermal, or ultrasound.

• Radiofrequency is a radio wave which can be used for ablation by means of resistive heating.

• Complications from ablation can be due to charring, popping, and perforating.

• Targets for ablation depend on the mechanism of each arrhythmia such as the earliest ventricular signal for WPW.

• Roles of catheter ablation include saving life (as in WPW), improving LV function (as in tachycardia induced cardiomyopathy), and reducing symptoms.