Noninvasive Assessment of the Biventricular Pacing System

Abstract

Cardiac resynchronization using biventricular (BiV) pacing systems has been introduced for the treatment of symptomatic heart failure in patients with bundle branch block or prolonged QRS duration. Recent controlled clinical trials 1,2 have concluded and the results indicate that the majority of carefully selected patients will experience clinical improvement. The Food and Drug Administration has recently approved BiV pacing systems for implantation in patients with NYHA class III-IV heart failure despite optimal medical therapy when the QRS duration is >130 ms. The BiV pacing system differs from the conventional permanent pacemaker by incorporating a third lead that is positioned on the epicardial surface of the left ventricle (LV) via the coronary venous system. Simultaneous stimulation of the right ventricle (RV) (via a conventional endocardial lead) and the LV accomplishes BiV pacing and "resynchronizes" ventricular activation. This nontraditional format of ventricular stimulation may present new challenges in the assessment of pacing function, and will necessitate a greater understanding of basic and complex features of BiV pacing and its effect on noninvasive modalities such as the electrocardiogram (ECG) and intracardiac recordings on the pacemaker programmers. Initial systems utilized a conventional pulse generator with a modified header where LV and RV signals and output were linked; systems with separate ports for the LV and RV are now available.Many variables, in addition to the basic lead configuration, can influence accurate assessment of BiV pacer function, including LV and RV lead position, consistency of capture, differences in impedance between the ventricular leads, conduction velocity and patterns, relative timing of stimulation between the ventricular channels, and fusion with intrinsic activation. New and unusual sensing problems can arise creating complications such as pacemaker-mediated tachycardia or inappropriate inhibition. Pacemaker programming also involves issues unrelated to combating bradycardia. This review will focus on performing a noninvasive assessment of the BiV pacing system using the 12-lead ECG and intracardiac electrograms, analyses of sensing and capture functions, and general programming recommendations. TWELVE-LEAD ECGThe ECG is the most readily available tool to ascertain whether BiV pacing has been successfully accomplished, and whether sensing or capture problems exist. The ECG can provide a permanent template of capture configurations (e.g., no pacing, RV, LV, BiV) for easy and reliable troubleshooting. Current BiV systems usually pace BiV via a unipolar LV lead as a common anode attached to the RV tip versus a ring or proximal shared electrode also on the RV lead. They may also pace in a unipolar 58

Electrocardiographic Follow‐Up of Biventricular Pacemakers

“…[9][10][11] When there is intact capture in both the RV and LV, the evoked response on the ventricular electrogram will show a monophasic complex in contrast to the two distinct depolarizations during spontaneous AV conduction if the native QRS is wide (LBBB or left intraventricular conduction delay) (Fig. [9][10][11] When there is intact capture in both the RV and LV, the evoked response on the ventricular electrogram will show a monophasic complex in contrast to the two distinct depolarizations during spontaneous AV conduction if the native QRS is wide (LBBB or left intraventricular conduction delay) (Fig.…”

“…1,2,11 If the biventricular ECG is virtually similar to that recorded with RV or LV pacing alone and no cause is found, one should not automatically conclude that one of the leads does not contribute to biventricular depolarization without a detailed evaluation of the pacing system. [9][10][11] The electrocardiographic consequences of temporally different RV and LV activation with programmable V-V timing in the most recent biventricular devices have not yet been studied.…”

Computer analysis of implanted cardiac pacemaker rhythm

“…Biventricular pacing gives rise to new challenges in the assessment of pacing function and requires a greater understanding of its effect on the ECG [10]. As far as is known, this is the first demonstration (Figure 3) of the detection of distinct biventricular pacing spikes using a standard, albeit enhanced, ECG machine.…”

“…Two standard 12-lead resting ECGs were recorded and printed from each subject (one after the other), following strict technique guidelines [10]. Settings were then altered on the Atria to allow recordings of two channels of high speed data which could be examined and analysed separately in order to measure pacing stimuli amplitudes in leads I, II and V1-V6, which would allow lead comparisons.…”

“…Although two spikes might not always be visible in biventricular pacing, the fact that two distinct spikes are seen in all 16 cases means that there is potential for developing an algorithm possibly involving analysis of QRS morphology, which would allow automated detection of biventricular pacing, Furthermore, in light of the advocated resurgence of 12 lead ECG use in CRT follow-up [3,10,11], technology which is able to report biventricular pacing will prove to be of great clinical use.…”