His bundle electrogram

A quad-polar electrode catheter is inserted through the left femoral artery and positioned at the noncoronary cup of the aortic valve to record a His bundle electrogram. A bidirectional steerable monophasic action potential (MAP) recording/pacing combination catheter is inserted through the left femoral vein and positioned at the endocardium to obtain MAP signals. The signals are amplified with a DC amplifier. 

Figure 24.7 shows an example of a His bundle recording. The top two traces are leads II and Vq of the EGG and the bottom trace is the voltage difference from two electrodes on the indwelling electrode catheter. This internal view of cardiac activation combined with the His bundle electrogram has been referred to as His bundle electrocardiography [20]. Atrial activation on the catheter recording is called the A deflection and ventricular activation called the V deflection. The His bundle potential is the central H deflection. Since the catheter is located very close to the His bundle and AV node, it is assumed that the A deflection arises from atrial muscle tissue close to the AV node. When combined with the surface lead information a number of new intervals can be obtained. These are the PA, AH, and HV intervals. The PA interval is a measure of atrial muscle activation time, the AH interval is a measure of AV nodal activation time, and the HV interval is a measure of the ventricular conduction system activation time. 

Scherlag B.J., Samet R, and Helfant R.H. His bundle electrogram a critical appraisal of its uses and hmitations. Circulation 46 601-613,1972. 

Fig. 10.1 Diagrammatic representation of the atrioventricular conduction system. The bundle branch system consists of a three-pronged system (two on the left side and one on the right side). At the bottom, the surface ECG is depicted simultaneously with a His bundle electrogram (HBE). The HBE is recorded near the septal leaflet of...

Fig. 10.5 Sinus rhythm with second-degree Type 13 2 iniranodal AV block, and RBBB. Note that the AH interval remains constant. TTie HV interval increases from 80 (following first P-wave) to 150ms (following second P-wave). The third P-wave is followed by an H deflection but no QRS complex. AV block occurs in the His-Purkinje system below the site of recording of the His bundle potential (arrow). Note the shorter PR interval after the nonconducted P-wave, a feature typical of Type I second-degree AV block. HBE = His bundle electrogram, A = atrial deflection, H = His bundle deflection, V = ventricular deflection, P = P-wave. TL = time lines 50ms. (Barold SS. Pacemaker treatment of bradycardias and selection of optimal pacing modes. In Zipes DP (Ed.). Contemporary Treatments in Cardiovascular Disease, 1997 1 123, with pamission.)...

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