1. Clinical Intracardiac Electrophysiologic Testing: Technique, Diagnostic Indications, and Therapeutic Uses 
STEPHEN C. HAMMILL, M.D. 
Mayo Clinic Proceedings 
Volume 61, Issue 6, Pages (June 1986)
DOI: /S (12)
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

2. Fig. 1
Locations of four multielectrode recording and pacing catheters during intracardiac electrophysiologic study: in high right atrium (HRA), across tricuspid valve in region of His bundle electrogram (HBE), in coronary sinus (CS) to record electrical activity from left atrium and left ventricle, and in right ventricular apex (RVA). Relationship to atrioventricular node (AVN) is depicted.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

3. Fig. 2
Simultaneous intracardiac recordings from high right atrium (HRA), His bundle electrogram (H1, and H2), and right ventricle (V) and surface electrocardiographic leads V1, II, and AVF. On His bundle electrogram, atrial depolarization (a), His bundle depolarization (h), and ventricular depolarization (v) allow measurement of conduction times through atrioventricular conduction system. A critically timed atrial premature stimulus (APC) during sinus rhythm (first two beats) induced supraventricular tachycardia due to reentry within the atrium and 2:1 atrioventricular conduction (last four beats). Absence of a His (h) depolarization after the atrial depolarization (a) indicates block at level of atrioventricular node.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

4. Fig. 4
Rhythm strip recorded during atrial fibrillation (mean heart rate, 300 beats/min with shortest interval between two QRS complexes being 160 ms) in patient with Wolff-Parkinson-White syndrome. This patient had experienced no previous symptoms associated with the Wolff-Parkinson-White syndrome until this arrhythmia, which resulted in sudden cardiac arrest.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

5. Fig. 5
Serial drug testing technique used to identify a drug regimen that is effective in preventing induction of ventricular tachycardia (VT). Sustained ventricular tachycardia is induced in the control state after introduction of critically timed paired stimuli (S1 S2). Ventricular tachycardia continues to be induced after administration of procainamide, lidocaine, propranolol, and quinidine on separate days. The combination of quinidine and propranolol is effective in preventing induction of ventricular tachycardia.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

6. Fig. 6
Rhythm strip recorded during supraventricular tachycardia, demonstrating termination of tachycardia by introduction of a critically timed premature atrial beat (arrow) delivered by a scanning pacemaker and subsequent restoration of sinus rhythm.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

7. Fig. 7
Diagram of procedure used for transcatheter ablation (fulguration) of the atrioventricular conduction system or tachycardias originating in posterior atrial septum or ventricles. Temporary pacemaker is placed, and catheter is positioned adjacent to structure that is to be ablated. The electrode catheter is attached to a switching box, which allows recording and display of unipolar electrograms obtained from distal, middle, and proximal electrodes of recording lead. At time of ablation, the desired electrode is switched to the cardioverter so that the electrical current will pass from the cardioverter through the electrode, ablate the cardiac tissue adjacent to the electrode, and return to the cardioverter through the back paddle. ECG = electrocardiographic; HBE = His bundle electrogram.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

8. Fig. 8
Diagrams of retrograde atrial activation in patients with Wolff-Parkinson-White syndrome and accessory atrioventricular pathways. Representation is at level of tricuspid and mitral valves; recorded time from ventricular activation to atrial activation is shown in milliseconds. A, Normal pattern of retrograde atrial activation during ventricular pacing, demonstrating that earliest activation is recorded in region of His bundle and other atrial septal structures and then spreads laterally to left and right atria. B, Right anterior free wall pathway map during paroxysmal supraventricular tachycardia, demonstrating that earliest point of retrograde atrial activation is eccentric—recorded in anterior portion of right atrium. C, Left lateral free wall pathway map during paroxysmal supraventricular tachycardia, demonstrating that earliest point of retrograde activation is eccentric—recorded in lateral left atrium from a coronary sinus catheter. D, Posteroseptal accessory pathway map during paroxysmal supraventricular tachycardia, demonstrating that earliest point of atrial activation is recorded in posterior septum from a catheter placed in right atrium.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

9. Fig. 9
Tracing from electrocardiographic lead V1, showing initiation of ventricular tachycardia (VT) with two critically timed premature ventricular stimuli (S1 S2) introduced during sinus rhythm.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

10. Fig. 10
Tracing from electrocardiographic lead I, showing that ventricular tachycardia (VT) at rate of 230 beats/min (BPM) is accelerated to rate of 260 beats/min after introduction of two premature stimuli (S1 S2).
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

11. Fig. 11
Demonstration of automatic implantable cardioverter defibrillator terminating an episode of rapid ventricular tachycardia and restoring sinus rhythm. Electrograms from epicardial leads and patch electrodes are recorded simultaneously with surface leads V6, I, and AVF at time of surgical implantation of automatic cardioverter.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

12. Fig. 12
Diagram of endocardial encircling ventriculotomy. Left ventricular aneurysm is opened, and surgical incision is made through endocardium to isolate normal myocardium from abnormal myocardium electrically in border zone adjacent to fibrotic ventricular aneurysm. Objective of performing this surgical technique is to isolate focus of the ventricular tachycardia.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

13. Fig. 13
Diagram of endocardial resection. Left ventricular aneurysm is opened, and endocardium in border zone between normal myocardium and ventricular aneurysm is excised. Objective of performing this technique is to remove abnormal endocardium (scarred tissue) that is involved in reentrant circuit of the ventricular tachycardia.
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions

14. Fig. 14
Use of a tilt table to assess patient with syncope in association with paroxysmal supraventricular tachycardia due to sinus node reentry. A, With patient in supine position, length of tachycardia cycle (CL) is 350 ms (170 beats/min), atrioventricular conduction is 3:2, and blood pressure (BP) is 110 mm Hg. B, With patient in erect position, duration of tachycardia cycle is decreased to 320 ms (188 beats/min), atrioventricular conduction is increased to 1:1, and blood pressure is decreased to 75 mm Hg. Patient experienced her clinical syndrome, including near-syncope. HRA, H1 and H2, and V = high right atrial, His, and right ventricular recording electrodes, respectively; a and v = atrial and ventricular depolarizations, respectively.145
Mayo Clinic Proceedings  , DOI: ( /S (12) )
Copyright © 1986 Mayo Foundation for Medical Education and Research Terms and Conditions