1. Electrical resynchronization induced by direct His-bundle pacing
Daniel L. Lustgarten, MD, PhD, Susan Calame, RN, Eric M. Crespo, MD, James Calame, RN, Robert Lobel, MD, Peter S. Spector, MD 
Heart Rhythm 
Volume 7, Issue 1, Pages (January 2010)
DOI: /j.hrthm
Copyright © 2010 Heart Rhythm Society Terms and Conditions

2. Figure 1
Summary of the types of direct His-bundle pacing (DHBP). In the two patients in whom selective direct His-bundle pacing (S-DHBP) did not narrow the QRS, the His-to-QRS and stimulus-to-QRS intervals were identical. The septal ventricular activation time was not advanced in either patient with DHBP. These findings indicate that the pacing site in these two patients was proximal to the His-Purkinje defect. NS-DHBP = nonselective direct His-bundle pacing.
Heart Rhythm 2010 7, 15-21DOI: ( /j.hrthm )
Copyright © 2010 Heart Rhythm Society Terms and Conditions

3. Figure 2
Criteria for selective direct His-bundle pacing (S-DHBP) with narrow QRS. A: The first QRS is an atrial paced beat showing complete left bundle branch block, QRS duration 172 ms. The second QRS shows S-DHBP with shorter QRS duration of 144 ms. There is rightward shift of the limb lead axis, and an r wave is present in lead V1. There is subsequent R-wave progression with transition between leads V2 and V3. There are associated repolarization axis changes. In addition, the stimulus-to-QRS onset interval is isoelectric in all 12 leads of the ECG with DHBP. Sweep speed = 50 mm/s. B: The first QRS is conducted during sinus rhythm, and the second QRS is S-DHBP. Electrograms from the DHBP lead (“LEAD”) and the adjacent His-bundle mapping catheter (“HBD–HB4”) are shown below the surface electrograms. Three findings are notable. (1) The interval between the His potential and QRS onset is longer than the interval between the stimulus and QRS onset (68 ms vs 50 ms). (2) The septal ventricular electrogram on the His-bundle mapping catheter (HBD–HB4) is advanced from 114 to 81 ms during DHBP. (3) There is no evidence of local ventricular capture on the His-bundle mapping catheter, consistent with the surface ECG. Sweep speed = 200 mm/s.
Heart Rhythm 2010 7, 15-21DOI: ( /j.hrthm )
Copyright © 2010 Heart Rhythm Society Terms and Conditions

4. Figure 3
Nonselective direct His-bundle pacing (NS-DHBP) with normalization of QRS morphology and restoration of inferior myocardial infarction pattern. A: Twelve-lead ECG from 1995, recorded in the setting of a recent inferior myocardial infarction that shows inferior Q waves. B: Atrial pacing during the implant procedure, with left bundle branch block and obliteration of the inferior myocardial infarction pattern (QRS duration 200 ms). C: NS-DHBP with QRS duration shortened to 172 ms and restoration of inferior Q waves. The vertical axis shifted from –30° to +60°. QRS dV/dt is more rapid. Evidence of local ventricular capture in the precordial leads is seen (arrow). Sweep speed = 50 mm/s in A-C.
Heart Rhythm 2010 7, 15-21DOI: ( /j.hrthm )
Copyright © 2010 Heart Rhythm Society Terms and Conditions

5. Figure 4
Progressive capture of latent His-Purkinje tissue resulting in nonselective direct His-bundle pacing (NS-DHBP) with increasing output and reversing polarity. A: Sinus rhythm with left bundle branch block, QRS duration 180 ms. A discrete His potential is present on both the DHBP lead (“LEAD”) and the octapolar mapping catheter (“HB2–HB4”). The H–QRS interval is 50 ms. B: During low-output bipolar pacing (cathodal tip) from the DHBP lead, there is a retrograde His potential with evidence of immediate ventricular activation following the stimulus artifact on the mapping catheter. Therefore, the QRS (200 ms) is the result of ventricular capture only. C: Increased output results in elimination of the His potential (arrow indicates where the His potential was prior to capture) and advances the early component of the QRS complex (R) from 86 to 65 ms. The late portion of the QRS remains unaffected (R′). The persistent left bundle branch block morphology and QS pattern in lead V1 suggests capture of the right bundle branch. D: Reverse polarity pacing (anodal tip) advances R′ from 150 to 105 ms, without affecting the early portion of the QRS (R), which remains at 65 ms. The end of the QRS is advanced from 195 to 165 ms. Sweep speed = 200 mm/s.
Heart Rhythm 2010 7, 15-21DOI: ( /j.hrthm )
Copyright © 2010 Heart Rhythm Society Terms and Conditions

6. Figure 5
Comparison of QRS duration with native conduction, direct His-bundle pacing (DHBP), and biventricular pacing (BiV) in patients in whom the QRS narrowed with DHBP. QRS narrowing was greater with DHBP compared with BiV, although the latter was also significantly less than conducted QRS duration (P <.05 for each comparison).
Heart Rhythm 2010 7, 15-21DOI: ( /j.hrthm )
Copyright © 2010 Heart Rhythm Society Terms and Conditions

7. Figure 6
Example of selective direct His-bundle pacing (S-DHBP) at lower-power output with onset of nonselective direct His-bundle pacing (NS-DHBP) at higher-output pacing. A: S-DHBP with stimulus-to-QRS onset isoelectric in all 12 surface leads. QRS duration is 144 ms. The interval from stimulus-to-QRS terminus is 190 ms. B: Distortion of the stimulus-to-QRS onset due to immediate ventricular capture (NS-DHBP) with increased pacing stimulus output. The interval from the stimulus-to-QRS terminus is identical to S-DHBP because the latter part of the QRS is activated by conduction via His-Purkinje tissue in both cases. Sweep speed = 50 mm/s in both panels.
Heart Rhythm 2010 7, 15-21DOI: ( /j.hrthm )
Copyright © 2010 Heart Rhythm Society Terms and Conditions