The findings of this study should come as no surprise, as some of the main TAVI vs. surgery clinical trials have established three well-supported conclusions:

• Patients requiring a pacemaker post-TAVI have reduced survival rates.
• Patients who develop left bundle branch block post-TAVI often exhibit higher pacemaker implantation rates during follow-up.
• Patients with post-TAVI left bundle branch block experience reduced survival.

While the rate of paravalvular leakage has notably improved due to newer prosthesis adaptations, the pacemaker implantation rate remains unresolved, likely due to procedural constraints. Implantation onto a calcified valve compresses the conductive tissue in the membranous septum, which could be modulated by specific implantation techniques but remains difficult to prevent.

Despite this potentially redundant work, its significance lies in three aspects: methodological quality, a patient population closer to real clinical practice than those in trials, and the inclusion of influential authors, mostly from the interventional cardiology field, published in a prestigious cardiology journal (JACC).

This study included 3,211 patients from the NEOPRO and NEOPRO-2 registries, comprising multinational experiences with two self-expanding prosthesis types—Medtronic Evolut® PRO® and PRO+® and Acurate® NEO® and NEO2®. Procedures occurred from 2012 to 2021 exclusively through transfemoral access, comprising 1,090 Acurate NEO® implants, 665 Acurate NEO2®, 1,312 Evolut PRO®, and 144 Evolut PRO+®. The pacemaker implantation rate was 11.3% within 30 days. However, rates varied markedly between Evolut® (15.2% for PRO® and 10.4% for PRO+®) and Acurate® (8.8% for NEO® and 7.7% for NEO2®); p < 0.001.

Pacemaker implantation post-TAVI led to observable consequences:

• Left ventricular ejection fraction was reduced in patients needing a pacemaker prior to hospital discharge.
• Pacemaker necessity was linked to higher mortality within one year of follow-up (HR = 1.66, p < 0.01).
• Higher rehospitalization rates were noted, impacting patients’ quality of life.
• This was particularly notable in patients with left ventricular ejection fraction depression, both mild (LVEF <50%; HR = 2.48, p = 0.021) and moderate (LVEF <40%; HR = 1.5, p = 0.07).
• In patients with normal left ventricular function, post-TAVI pacemaker implantation did not affect survival within the first year, though it may have longer-term implications.

The included population reflects typical registry characteristics, with an average age of 81.6 years and moderate surgical risk based on average STS scores of 4.5 points and EuroSCORE II of 5%. The authors conducted a univariate analysis revealing that patients needing a pacemaker were often male, diabetic, with previous surgical revascularization, poorer NYHA III-IV functional class, lower glomerular filtration rates, and higher surgical risk scores, as well as a higher preprocedural right bundle branch block rate (26% vs. 7%, p < 0.001). These factors should have been considered in the analysis, as they might serve as confounders impacting survival. Surprisingly, the authors did not mention this in the limitations section.

Multivariate analysis identified STS score and preoperative right bundle branch block (HR > 5) as the sole independent clinical predictors for pacemaker implantation necessity.

The authors conclude that post-TAVI pacemaker implantation with self-expanding devices is frequent and associated with increased mortality at one year in patients with some degree of left ventricular dysfunction. They highlight the importance of planning the procedure with these prostheses, emphasizing patient selection and identification of predictors influencing implantation technique variations that may help reduce this complication rate.

COMMENTARY:

As the saying goes, “it is better to prevent than to cure”. When atrioventricular block occurs post-TAVI, pacemaker implantation may be too high a price, especially if not anticipated during procedural planning. The authors’ suggestion of using resynchronization therapy devices in patients with ventricular dysfunction reveals a partial view of the issue and a potentially costly solution in terms of efficiency and added patient morbidity.

The reported pacemaker implantation rates, though high, align with literature standards, ranging from 8.3% to 11% for Acurate® and 11.8% to 20.7% for Medtronic Evolut®. Literature consistently shows that clinical trials provide the lower rate limits, while observational studies and registries provide the upper limits.

Beyond the preprocedural right bundle branch block, which quintupled the pacemaker need risk, understanding how prostheses interact with left ventricular outflow tract anatomy remains crucial for self-expanding devices. The specific characteristics of these TAVI devices should ideally make them less vulnerable to this complication, given their recapturability, adaptability to an irregular annulus, and lower radial force. However, the potential for post-implant expansion due to the nitinol material may be a factor justifying these outcomes.

The authors found that neither annular nor outflow tract calcification significantly affected post-TAVI pacemaker need. This places responsibility on the technique and device itself, where implantation depth emerged as an independent predictor, with thresholds of 5.9 mm for Acurate® (ROC AUC 0.58) and 4.3 mm (ROC AUC 0.58) for Evolut®. However, in my opinion, such precise measurements are impractical in real imaging. The authors emphasize Acurate®’s lower pacemaker need rate compared to Medtronic Evolut®, likely due to lower radial force, as well as technical aspects like alignment with native valve structure and a radiopaque marker on the Acurate NEO2® for more precise implantation depth control.

In summary, while TAVI has revolutionized aortic stenosis treatment, significant issues remain after 20 years. Atrioventricular block incidence is one of them. And amid competition with surgical techniques, a stronger internal comparison between devices is needed. This study, by interventional cardiologists, sets the stage by comparing two widely-used self-expanding devices, as previously done with studies like SCOPE2. This approach is necessary as not all devices will perform equally, and as in evolution, the best designs will endure.

REFERENCE:

Pagnesi M, Kim WK, Baggio S, Scotti A, Barbanti M, De Marco F, et al. Incidence, Predictors, and Prognostic Impact of New Permanent Pacemaker Implantation After TAVR With Self-Expanding Valves. JACC Cardiovasc Interv. 2023 Aug 28;16(16):2004-2017. doi: 10.1016/j.jcin.2023.05.020.