John Mandrola, MD

Disclosures

May 15, 2017

The secret is out. Finally. Nearly 40 years have passed since Dr El-Sharif and colleagues at the University of Oklahoma showed normalization of bundle-branch-block patterns by distal His bundle pacing.[1]

In a Tweet, the well-respected Dr Suneet Mittal (Valley Health System, NJ) said: "Without doubt, history will judge the [Heart Rhythm Society (HRS) Scientific Sessions 2017] as the meeting when the 'secret' of His bundle pacing [HBP] got out to the masses! Unbelievable interest."

No longer relegated to poster boards, sessions on HBP filled big conference rooms. Session chairs competed with attendees to ask questions. And I could hear genuine curiosity (rather than courtesy) in their queries.

Two advantages of pacing the His bundle instead of the right ventricle (RV) are that HBP results in a narrow QRS and thus synchronous ventricular contraction, and, in the majority of cases, HBP reverses bundle-branch patterns. Other than a special introducer sheath, HBP uses a standard pacemaker generator and standard pacing lead.

Dr Pugazhendhi Vijayaraman (Geisinger Heart Institute, PA) and colleagues presented long-term follow-up of a study comparing heart-failure hospitalization and mortality with either HBP (n=94) or right ventricular pacing (n=98). This comparison was made possible because colleagues at a neighboring hospital perform standard RV pacing; these patients made up the control group. Baseline characteristics of the nonrandomized groups were similar, except more patients in the HBP group had atrial fibrillation.

An earlier report of this study showed that HBP was feasible and resulted in reduced heart-failure hospitalizations and mortality compared with control patients who had greater than 40% RV pacing.[2] The latest abstract reported 5-year follow-up, which is important because skeptics of HBP worry about maintenance of acute results.

Vijayaraman said the early results held up: electrical parameters showed slight increases of pacing threshold with HBP vs RV pacing (1.6 V vs 0.8 V), but QRS narrowing was maintained at 5 years. HBP resulted in significantly fewer heart-failure hospitalizations (3% vs 12.3%, P=0.03) and numerically fewer deaths (27% vs 37%, P=0.14). When the authors compared death rates with HBP vs control patients with >40% ventricular pacing, they found a significant lowering of death rate (28% vs 47%,P=0.04)

Vijayaraman was quick to point out the limitations: it was a nonrandomized case-control study and an on-treatment analysis of HBP.

In that same oral abstract session, Dr Weijian Huang and colleagues from the First Affiliated Hospital of Wenzhou Medical College, China, presented two papers on HBP for the correction of left bundle branch block (LBBB). In the feasibility study, Huang showed acute correction of LBBB in 55 of 57 patients; 10 patients lost LBBB correction during follow-up because of increases in His bundle threshold. In the outcomes paper, he reported that patients with HBP-induced reversal of LBBB had significantly lower LV diameter, higher ejection fraction, and improved NYHA functional class after the procedure. While all patients had been hospitalized for heart failure before HBP, only three patients were hospitalized after HBP.

Dr Francesco Zanon (Santa Maria Della Misericordia Hospital, Rovigo, Italy) and colleagues in Maastricht presented the largest series of patients (n=369) with HBP. Zanon, who has been publishing on HBP for more than a decade,[3] reported that 85% of the patients maintained good performance of the His bundle lead over an average follow-up of 6 years.

If His bundle pacing provides synchronous ventricular contraction, why not combine it with atrioventricular (AV) node ablation in patients with symptomatic atrial fibrillation (AF) and high ventricular rates? The concern here is safety. AV node ablation renders the patient dependent on pacing.

Dr Vijayaraman led the way again with a series of 42 patients who underwent HBP and AV node ablation. He achieved success in 40 of 42 patients. Other than a slight increase in His threshold, (0.6 V on average), HBP remained stable during an average 19-month follow-up. Notably, in patients with an LVEF ≤40% before the procedure, LVEF improved from an average of 33±7% to 45±9% (P<0.001).

These papers replicate the published literature. In a crossover study design, Lustgarten and colleagues found HBP provided an equivalent CRT response in patients eligible for CRT.[4] In a recent paper published online in Heart Rhythm, the UCLA group showed that HBP successfully reversed LBBB in 16 of 21 patients referred for CRT and HBP-induced LBBB correction resulted in improved clinical and echocardiographic measures.[5]

Conclusions

Regular readers know that I am biased about His bundle pacing. Having done more than 50 cases, including five with AV node ablation, I am enraptured with this technique.

My experience should quiet the critics who say this is difficult. It is not. I learned it by watching a 5-minute video, and then starting on patients with sick sinus syndrome. It took about 10 cases to get comfortable, and now the norm in our lab is HBP in nearly all patients (Figures 1 and 2 show a typical LBBB reversal).

Figure 1. ECG Showing Left Bundle Branch Block (Courtesy of Dr Mandrola)

Figure 2. Reversal of LBB after His-Bundle Pacing (Courtesy of Dr Mandrola)

To be fair, there are reasons for caution. The evidence thus far comes from case series and nonrandomized case-control studies. We need randomized controlled trials. Long-term lead performance is also a concern. The early signal looks reassuring, but we need longer follow-up data. Another worry is battery longevity. His bundle thresholds are typically higher than the ventricular threshold. This could reduce battery longevity and potentially expose younger patients to more generator changes.

I will close with a note on the challenge of funding a multicenter trial. Industry usually does not fund trials that reduce units sold. Consider these facts: About 10% to 20% of patients who receive standard pacing will develop pacing-induced LV dysfunction.[6,7,8] Many of these patients go on to get a CRT upgrade (another unit sold). HBP can reverse bundle branch block—which is exactly what CRT does. These two features reduce market demand for the lucrative CRT device.

The current research on HBP is investigator driven. Investigators told me they are using monies left over from other projects. I hope the enthusiasm from this meeting will nudge industry to defy its critics and do what is best for patients: fund a trial. Government could also fund such a trial, but experts I spoke with felt this was unlikely.

HBP has it all: the beauty of basic electrophysiology, the elegance of simplicity, the parsimony of cost-conscious care, and the joy of helping people.

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