Introduction to Electrophysiology Wm. W. Barrington, MD, FACC University of Pittsburgh Medical Center
Objectives Indications for EP Study How do we do the study Normal recordings Abnormal Recordings Limitations of EP Study
Indications for EP Study Characterization of an arrhythmia with the intent of performing ablation therapy. Characterization of the conduction system to determine the need for permanent pacing. Stratify the patient s risk of developing a symptomatic or life threatening arrhythmia. Characterization of the effectiveness of therapy. "Guidelines for Clinical Intracardiac Electrophysiological and Catheter Ablation Procedures Circulation. 1995;92:673-691.)
Ablation is a large part of the current indications for EP Study The authors examined published results from 1990 to 2007 that were cited in Medline or EMBASE: 18 Primary Studies of Atrial Flutter ablation 39 Primary Studies of SVT ablation Am J Cardiol (2009)104:671-77
Study examined reentrant SVT s Atrial Flutter AV Node Reentry Accessory Pathways Ablation site Ablation Line Ablation Site Am J Cardiol (2009)104:671-77
Meta-Analysis of Ablation of Atrial Flutter and SVT s Atrial Flutter Accessory Pathways AV Node Reentry Single procedure success 91.7% 90.9% 94.3% Multi-procedure success 97.0% 93.3% 96.0% Repeat ablation procedure 8.0% 8.0% 5.6% Complications Procedure related mortality 0.0% 0.1% 0.0% Hematoma 0.0% 0.3% 0.3% Cardiac Tamponade 0.0% 0.4 % 0.1% Need for Pacemaker 0.2% 0.3 % 0.7% Am J Cardiol (2009)104:671-77
Meta-Analysis of Ablation of Atrial Flutter and SVT s The authors concluded: studies of RFA for treatment of patients with atrial flutter and SVT report high efficacy rates and low rates of complications 1. Furthermore: the 2003 consensus guidelines for SVT management 2 recommend radiofrequency ablation as a class I intervention in all cases except: First episode of well tolerated atrial flutter SVT patients who do not desire ablation or Asymptomatic patients with WPW. 1. Am J Cardiol (2009)104:671-77 2. J Am Coll Card (2003) also available at www.acc.org
How to do an EP Study Electrophysiologist will place 1, 2, 3 or more catheters into the heart. Access will be from femoral vein, antecubital vein, subclavian vein or internal jugular vein. Catheters generally at least quadrapolar (4 electrodes) in configuration. Pacing and recording usually done in bipolar configuration (one electrode + and the other -)
How to do an EP Study
How to do an EP Study Typical Catheter Locations High Right Atrial Location HRA His Bundle Location His Right Ventricular Apical Location RVA
How to do an EP Study
How to do an EP Study Screen display shows surface ECG and appropriate intracardiac channels Intracardiac recordings are filtered to allow visualization of signals Band pass filter from 30 or 40 Hz to 400 or 500 Hz Gain settings to optimize viewing Clipping as needed
How to do an EP Study P QRS A H V
How to do an EP Study Baseline Measurements Sinus cycle length (SCL or AA interval) PR interval (120 200 ms) QRS duration (< 100 ms) QT interval (QTc < 440) AH interval (60 125 ms) HV interval (35 55 ms)
PR = 170 ms QT = 380 ms QRS = 80 ms HV = 40 ms AH = 90 ms SCL (AA) = 830 ms
PR = 140 ms QRS = 140 ms AA = 880 ms AH = 100 ms HV = -30 ms Ventricular Pre-excitation (Wolff- Parkinson-White)
12 Lead ECG of patient with short HV interval
How to do an EP Study Atrial pacing examining SA nodal function or Sinus Node Recovery Time (SNRT) Pace HRA at fixed rate for at least 30 seconds. Measure interval from last paced atrial signal to first sinus atrial signal this is the sinus node recovery time (SNRT). Generally this is repeated for a variety of pacing cycle lengths.
Paced at 600 ms (100 bpm) for > 30 sec Last paced A First sinus A SNRT = 1320 ms
How to do an EP Study Sinus Node Recovery Times (SNRT) Normal is < 1.3 x sinus cycle length (<1600 ms) Can correct by several methods: CSNRT = SNRT SCL ( Normal <525 ms) Ratio of SNRT/SCL (Normal < 1.5) Limitation of SNRT is that while it is very specific it is not very sensitive!
How to do an EP Study Incremental atrial pacing examining AV nodal function Pace the HRA at gradually increasing rates. Look for gradual prolongation in the AH interval ( decremental conduction). Determine the AV nodal wenkebach cycle length.
Normal Decremental Function AH = 160 ms AH = 195 ms PCL = 600 ms PCL = 500 ms
AH Interval AV Nodal Function Curve Normal Decremental AV Nodal Conduction Faster Rate S1 Interval
Wenkebach Block Mobitz type I (above His bundle) V No V A H AH = 220 ms A No H A Wenkebach CL = 410 ms PCL = 410 ms
Mobitz type II block (below the bundle of His) A H V A H A H V A H A H V A H A H V A H Atrial PCL = 500 ms or 120 bpm
How to do an EP Study Atrial extra stimulus techniques Pace the atrium at a fixed CL (typically 600, 500, 400 ms) for 8 beats then introduce 1,2 or 3 extrastimuli Useful in determining: Refractory periods Change in conduction Dual AV nodal physiology Initiation of an arrhythmia
S1 S2 310 ms S1 S2 300 ms A H V AH=160 ms A H V AH=280 ms Drive Train of 8 beats at 500 ms (S1) and one premature S2 310 ms after S1 Drive Train of 8 beats at 500 ms (S1) and one premature S2 300 ms after S1
AH Interval AV Nodal Function Curve AH Interval jumps suggest conduction moved from one conduction pathway to another. A > 50 msec jump in AH interval with a 10 msec decrease in S1S2 interval is called Dual AV Nodal Physiology More Premature S1S2 Interval
Right Atrial Anatomy Superior Input Inferior Input Left Atrial Input Atrial depolarization can reach the AV node by several paths. When activation changes from the fast conducting Superior input to the slower Inferior input we see an AH interval jump.
S1 S2 240 ms A H V AH=250 ms SVT at 200 bpm AV Node Reentry
S1 S2 310 ms QRS = 120 ms PR = 210 ms HV = 45 ms A H V Functional LBBB
How to do an EP Study Incremental Ventricular pacing examining retrograde AV nodal function Pace the RVA at gradually increasing rates. Look for gradual prolongation in the VA interval (decremental conduction) Concentric activation (via AV node) Eccentric activation (via AP). Determine the VA wenkebach cycle length.
Concentric retrograde conduction V A His A is earliest PCL = 500 ms
V A V A Earliest A In His Earliest A In CS (left side) Concentric (AV nodal) retrograde Activation Eccentric (AP) retrograde Activation
Retrograde Jump VA = 80 ms VA = 210 ms V A V A V A S1 = 600 ms
How to do an EP Study Ventricular extra stimulus techniques Pace the ventricle at a fixed CL (typically 600, 500, 400 ms) for 8 beats then introduce 1,2 or 3 extrastimuli Useful in determining: Refractory periods Change in conduction Dual retrograde AV nodal physiology Initiation of an arrhythmia
No retrograde conduction No repetitive response S1 = 600 ms S1S2 = 260 ms Single Ventricular extra stimuli
No ventricular response ERP of the RVA S1 = 600 ms S1S2 = 240 ms Single Ventricular extra stimuli
Single induced beat S1= 400 ms S1S2 = 240 ms Single Ventricular extra stimuli
No repetitive response S1 = 400 ms S1S2 = 250 ms S2S3 = 200 ms Multiple Ventricular extra stimuli
400/260/230 Sustained Monomorphic VT Multiple Ventricular extra stimuli
Sustained Monomorphic VT Rate = 220 bpm Induced Ventricular Tachycardia
Limitations of the EP Study EP Study has not been widely used in patients with nonischemic cardiomyopathy Sensitivity and specificity is likely decreased
Limitations of the EP Study EP study may not be able to reproduce a non-reentrant arrhythmia The EP study tries to cause block in one limb while exciting the other limb to induce the arrhythmia Pharmacologic maneuvers may help induce non reentrant arrhythmias
How to do an EP Study These techniques along with Electro-anatomic mapping (CARTO) Catheter mapping Pacing maneuvers Allow us to localize the arrhythmia circuit to facilitate diagnosis and treatment with ablation.
Ablation is a large part of the current indications for EP Study so lets look at a few examples
Baseline ECG for 17 year old with palpitations
Wide QRS (130 ms) Negative HV AP Potential Pacing from HRA
His cloud 4 cm Ablation Location
Wide QRS (130 ms) QRS = 80 ms AV = 50 ms AV = 180 ms Loss of antegrade AP function Successful RF Ablation
Post Ablation ECG
ECG of SVT in 67 year old
I avf V1 V6 hra His p His m His d Why are these different? Abl d Abl p Cs 4 Cs 3 Cs 2 Cs d RVa Stim Eccentric Activation Concentric Activation Intracardiac in SVT Ventricular Pacing
I avf V1 V6 hra His p His m His d Abl d Abl p Cs 4 Cs 3 Cs 2 Cs d RVa Stim Eccentric Activation In SVT Concentric Activation RV pacing
I avf V1 V6 hra His p His m His d SVT Abl d Abl p Cs 4 Cs 3 Cs 2 Cs d RVa Stim Termination of SVT with RF Termination with Block in AP
Questions or Comments?