Investigators retrospectively analyzed almost 250 patients with severe aortic stenosis (AS) who underwent TAVR, examining multiple factors that contributed to PPMI.
The analysis was used to generate an anatomically guided Minimizing-Depth-According-to-the-membranous-Septum (MIDAS) approach to device implantation and, after adjusting for confounding variables, they found that implant depth greater than the length of the membranous septum (MS) independently predicted PPMI.
Prospectively applying the MIDAS approach to 100 patients, positioning the device at a depth of less than the MS length, PPMI rate was reduced from 9.7% in the original patients to 3.0% in the MIDAS patients.
Moreover, the rate of new left bundle branch block (LBBB) was reduced from 25.8% in the original cohort to 9% in the MIDAS cohort.
“In a nutshell, to summarize the rationale, rather than doing the procedure the same way for every patient, we tailored the positioning of the valve according to the individual patient’s anatomy of the MS,” lead author Hasan Jilaihawi, MD, associate director of medicine and cardiothoracic surgery and interventional cardiologist, NYU Langone Health, New York City, told theheart.org | Medscape Cardiology.
“In our center, using this approach, we have been able to reduce our CoreValve pacemaker rates to lower than the rates of surgical aortic valve replacement,” said Jilaihawi, who is also the director of the NYU Imagine CoreLab.
A Further Look
“Many of the problems previously associated with TAVR, such as paravalvular leak and death, have been resolved and are very low, but the rates of pacemaker implantation have until now remained very high,” Jilaihawi observed.
The risk has been higher in self-expanding vs balloon expandable TAVR.
Moreover, “there remains a huge variation in the rates of pacemaker [implantation] throughout the country and worldwide, so it was an important issue for us to focus on and try to resolve — especially as we are seeing lower-risk and younger patients in whom the impact of a pacemaker is much greater,” Jilaihawi said.
Jilaihawi and his group “looked further,” and realized that PPMI was “associated with having a shorter length of MS.”
He explained that the electrical conduction system is close to the aortic valve and a shorter MS passes closer to that system than a longer MS.
“The problem was that previously, there was no parameter that could be used to guide a procedure, so we didn’t modify the procedure based on the MS, but we recognized that it was a risk factor,” he said.
The researchers performed a retrospective analysis of 248 consecutive patients (mean age 83.2 ± 6.9, 77.5% male) with severe AS who were treated with repositionable self-expanding TAVR (Evolut R, Evolut Pro, and Evolut 34 XL).
Patients had been treated using the standard TAVR approach, that is, aiming for a 3 to 4 mm implant depth in relation to the noncoronary cusp and recapturing and repositioning in the event that the device landed markedly lower.
Right bundle branch block (RBBB) and larger aortic annular and root dimensions on CT, larger device size, pre-release implant depth, and pre-release implant depth larger than MS were predictors of PPMI.
Shorter MS was a “notable” predictor of PPMI.
Table. PPMI Rate by MS Length
PPMI Rate (%)
≥ 5 mm
< 5 mm
< 2 mm
PPMI = permanent pacemaker implantation
MS = membranous septum
Although no differences in PPMI were found between the Evolut R and Evolut Pro, a “clear correlation” was found between increasing device size and PPMI.
After multivariable analysis, the only significant predictors that remained were device size (34 XL) and implant depth in relation to the MS.
The researchers applied the findings of the retrospective analysis to develop a “prospective anatomically-guided MIDAS approach to peri-operative pacer management and device positioning.”
“I developed some new imaging techniques to look at the MS that corresponded to the procedure itself, calibrating the technique to a level where we could aim higher than the MS in a particular placement, thereby guiding the position of the TAVR device,” Jilaihawi said.
“For example, if the MS is very short, we would not accept a lower position and would always try to be higher than the MS, at least in theory, not to make contact with the conduction system,” he said.
The MIDAS approach aims for a pre-release depth, in relation to the noncoronary cusp (NCC), smaller than the length of the patient’s MS, but no higher than 1 mm “to minimize the potential risk of device embolization (also described as ‘pop-out’),” the authors explain.
The MIDAS model was then implemented in the prospective study of 100 consecutive patients, who were followed after discharge for at least 30 days.
The prospective MIDAS group and the retrospective standard group had similar rates of PPMI risk factors, in terms of RBBB, use of XL prostheses, and MS length (3.6 ± 1.9 mm vs 3.9 ± 2.3 mm, respectively, P = .28).
However, there was a “small but significant difference” in device depth between the MIDAS and the standard in device groups (2.3 ± 1.2 mm vs 3.3 ± 1.8 mm, respectively, P < .001).
“This translated to a dramatic difference” in device depth smaller than MS length in the MIDAS and the standard groups (79.8% vs 54.8%, P <.001), the authors write.
At 30 days of follow-up, there were only 3 cases of PPMI in the MIDAS group — all implanted peri-procedurally — and there were no deaths.
The standard group had over three times the number of PPMIs compared with the MIDAS group (9.7% vs 3%, respectively, P =.035).
The rate of new LBBB was also significantly lower in the MIDAS group vs the standard group (9% vs 25.8%, respectively, P < .001).
“The MIDAS-TAVR approach, which respected this individualized anatomy and delivered a precision-medicine ethos to procedural technique, resulted in a dramatic reduction in PPMI and LBBB, despite a minimally higher length of implantation overall, with no compromise to other potentially related clinical outcomes, such as valve embolizations,” the authors summarize.
Commenting on the study for told theheart.org | Medscape Cardiology, Josep Rodés-Cabau, MD, director, Catheterization and Interventional Laboratories, Quebec Heart and Lung Institute, Quebec City, Canada, called the results “really impressive” because going down below 5% in terms of pacemaker implantation rate is “exceptional.”
Rodés-Cabau, who is the author of an accompanying editorial and was not involved with the study, said the “proposed approach should be evaluated and it would be worth it to try to reproduce these results, because there’s no doubt that they’re outstanding in terms of conduction disturbances and pacemaker rates.”
It needs to be “demonstrated that these results are maintained in a larger cohort of patients, especially when multiple operators are involved,” he said.
Jilaihawi agreed, adding that the “next step of research is to reproduce it in multicenter studies.”
He noted that his group will be further testing MIDAS in collaboration with other cardiac centers and will be working with Medtronic and Boston Scientific to “try to use their repositioning valves in the setting of MIDAS, to minimize depth according to the septum.”
No source of funding was listed. Jilaihawi has been a consultant to Edwards Lifesciences and Venus Medtech and has received grant/research support from Medtronic and Abbott Vascular. The other authors’ disclosures are listed with the original article. Rodés-Cabau has received institutional research grants from, and is consultant for, Edwards Lifesciences, Medtronic, and Boston Scientific.