We conducted a retrospective review of the medical records of 338 consecutive patients who underwent TAVI from August 2007 to October 2016 at Vila Nova de Gaia Hospital Center, Portugal.13,14 We excluded from the analysis patients with pPM (implanted before TAVI or during the follow-up period) and those with unavailable 12-lead electrocardiograms.

A separate sub-analysis was performed according to the type of implanted prosthesis: SEP or BEP. The types of SEP were Medtronic CoreValve Evolut R (Medtronic, Minneapolis, Minnesota), Medtronic Engager Valve (Medtronic, Minneapolis, Minnesota), Symetis Acurate Neo Valve (Symetis, Ecublens VD, Switzerland), St. Jude Medical Portico Valve (St. Jude Medical, St. Paul, Minnesota) and Boston Scientific Lotus Valve (Boston Scientific, Marlborough, Massachusetts). The BEP were Edwards Sapien XT Valve and Edwards Sapien 3 Valve (Edwards Lifesciences, Irvine, California).

All patients were assessed by a multidisciplinary team and the TAVI procedure was decided by consensus. The local ethics board approved the study, which was conducted in accordance with the Declaration of Helsinki.

Standard 12-lead electrocardiograms were obtained at hospital admission (within 24 hours before the procedure), on the day of hospital discharge and at six-month follow-up. Electrocardiograms were recorded using standard calibration (10 mm=1 mV, 25 mm/second). The same researcher performed a prospective analysis of all the electrocardiograms and assessed the following parameters: rhythm, heart rate, PR interval, presence and type of AV block, QRS interval, presence of bundle-branch block and corrected QT interval (cQT) using Bazett's formula. All these analyses were performed according to the recommendations for the standardization and interpretation of electrocardiograms.15 The investigator was blinded to the type of implanted prosthesis.

Echocardiograms were performed and several variables were collected, mean aortic gradient, valvular aortic area, left ventricle ejection fraction and left ventricle end-diastolic diameter.

Cardiac computed tomography was performed and the following variables were collected: aortic valve calcium volume and depth of prosthesis implantation within left ventricular outflow tract (LVOT). Prosthesis implantation depth was assessed before and three months after TAVI and measured as the distance between the annular margin of the non-coronary cusp of the native aortic valve and the ventricular edge of the prosthesis frame, as previously described.16

All these measurements were performed by two independent and experienced cardiologists blinded to clinical data, who reviewed the images separately, using dedicated software for aortic valve assessment (3mensioValvesTM, version 6.1, 3mensio Medical Imaging BV, Bilthoven, the Netherlands). We used the mean values of the two measurements.

Continuous variables are expressed as mean ± standard deviation or median, as appropriate. Differences were analyzed using the Friedman test for heart rhythm, AV and intraventricular conduction. The Wilcoxon signed-rank test was used for the other variables.

To identify predictors of electric disturbances after TAVI, univariate and multivariate logistic regressions were performed. All variables with a p-value of <0.10 in univariate analysis were entered in the multivariate model. The adequacy of the model was verified using the Hosmer-Lemeshow test. All statistical tests were two-tailed and a p-value of <0.05 was considered statistically significant. All data analyses were performed using the IBM SPSS Statistics for Windows, Version 23.0. Armonk, NY: IBM Corp.

Table 4 shows the electrocardiogram parameters according to the types of prostheses (SEP and BEP) and the comparative analysis of the differences observed.

At discharge, there was a significant increase in the PR interval in patients with SEP (baseline 174±31 ms vs. discharge 184±41 ms, p=0.01) which did not continue at follow up (178±33 ms, p=0.05). PR interval was not significantly different before and after BEP implantation.

There was a widening of the QRS duration in both groups after TAVI (Table 4). At discharge, SEP group presented higher QRS values (SEP 132±28 ms vs. BEP 126±28 ms, p=0.324) and a higher incidence of new-onset LBBB (16% SEP vs. 9% BEP, p<0.0001).

Although QRS values tended to improve at 6 months follow-up, the improvement was less pronounced in the SEP group (SEP 127±28 ms vs. BEP 117±28 ms, p=0.034).

In five patients (3%), there was a need for prosthesis repositioning; among these patients, one (0.5%) received a SEP and developed new LBBB at discharge, which persisted at the 6-month follow-up.

At discharge, there was a significant increase in the cQT interval in patients with SEP (baseline 434±31 vs. discharge 444±30 ms, p=0.01) which did not persist at follow-up (439±33, p=0.140). cQT interval changes after TAVI with BEP were not statistically significant.

Table 5 shows analysis of predictors of LBBB at discharge after TAVI.

The depth of valve implantation within the LVOT was a predictor of new LBBB at discharge in univariate logistic regression (OR 29, 95% CI 9.3–51.7 per additional mm of implantation depth, p=0.002) and in the multivariate regression (OR 37.6, 95% CI 14.6–65.2, p=0.001; Hosmer-Lemeshow goodness-of-fit test p=0.65). This variable was also a predictor of new LBBB in the SEP group (OR 38, 95% CI 10.5–72.6, p=0.005) but not in the BEP group (OR 14, 95% CI 12.9–48.7, p=0.345). The remaining analysis of predictors of electric disturbances after TAVI was not statistically significant.

Considering the proximity of the aortic valve to the conduction system, most of the electrical disturbances following TAVI result primarily from direct mechanical injury to the conduction system, which can result from edema and/or ischemia.17 In this study, the observation that conduction disturbances are more pronounced at discharge compared to follow-up further supports this theory.

It is well known that TAVI prolongs the atrial-His interval and may cause high-degree AV block,18,19 which is transitory in most of the patients without the need for pPM.20–22 In accordance with these observations, our study is one of the few studies20,22 that analyzes systematically AV conduction after TAVI in pPM-free patients and demonstrates generalized PR interval prolongation. Interestingly, we observed that these AV disturbances improve at 6 months follow-up, as also previously described.20,23

Regarding the intraventricular conduction disturbances, we observed that new-onset LBBB occurred in 25% of patients which is in accordance with previous studies that reported an incidence between 4%–65%.10,24–28 Nazif et al.29 analyzed disturbances following TAVI with BEP in 1151 patients without pPM and found an incidence of new LBBB of 10.5%. The variation in incidence of new LBBB can be explained by differences in the type of patients that were included in the studies, the timing of measurement, the type of prothesis that was implanted and the duration of follow-up.

The main rhythm disturbance associated with TAVI implantation is AF, although ventricular arrhythmias can also occur.30,31 We found an incidence of new-onset AF of 11% at discharge and 10% at 6 months. Similar results were reported in a meta-analysis that included sixty-five studies (43 506 patients), which found an incidence of new-onset AF after TAVI of 11% in-hospital and 14% at 1-year follow-up.31 It is known that the prevalence of new-onset AF after surgical aortic valve replacement (SAVR) is much higher, between 15–45%.32,33 The pathophysiological mechanisms of AF after TAVI are still unclear. In severe AS, left atrial dysfunction predicts post-SAVR new-onset AF even in patients with nondilated left atria, as previously described.34 These observations support the theory that post-TAVI AF may be related to underlying left atrium disease and systemic inflammatory response.

The cQT interval represents ventricular repolarization and its increase is associated with the risk of cardiac death.35 Previous studies reported a decrease in QT interval after TAVI,35–37 which is thought to be possibly related to reduction in afterload, increase in coronary flow and early left ventricular mass regression. In the present study, there was an increase of cQT interval at discharge, particularly in patients with SEP. The divergent QT evolution results after TAVI may be related to different methodologies among studies and the significant incidence of ventricular electrical disturbances found in our study. Moreover, other factors such as autonomic neuropathy, electrolyte imbalance and medication, can also lead to QT interval changes.

Regarding the medication used by the study population, beta-blockers were the most common drug. Although many patients presented electrical disturbances, chronotropic negative therapy was continued at discharge and at the six month follow-up, possibly due to the significant prevalence of comorbidities, such as hypertension, heart failure, coronary artery disease and AF.

The risk of electrical disturbances for SEP and BEP can be different.28 We found a higher incidence of electrical disturbances in the SEP group with no recovery from QRS widening at six months, contrary to the observations in the BEP group. In addition, the risk of new-onset LBBB at discharge was two times more frequent after SEP than BEP. The different design and deployment system associated with the gradual radial force exerted by SEP on the LVOT can contribute to a higher frequency of disturbances.

Most of the previous studies that assessed the influence of prosthesis type on electrocardiogram disturbances did not consider the differences between SEP and BEP38–43 or reported indirect comparisons of studies with different designs.10,28 However, there are two studies which compared the incidence of LBBB according to the type of prosthesis. Franzoni et al. reported similar results to our study, with a 26.5% incidence of LBBB and a higher rate of LBBB persistence at discharge (32.2%) with SEP.26 Houthuizen et al. also reported a more frequent LBBB occurrence and poorer recovery with SEP, although there was a slightly higher incidence of LBBB, 36.8%.27 Our study was performed on a single-center, included more SEP than the CoreValve trial and was conducted in the same European population, while the study from Houthuizen et al. included participants from multiple countries.

Female gender, diabetes, previous coronary bypass grafting and baseline QRS duration were described as predictors of new LBBB.24,44–46 However, in the present series, these variables were not significant.

In our cohort, the depth of valve implantation was an independent predictor of new-onset LBBB at discharge, particularly in the SEP group. This result is in accordance with previous studies, which also reported right bundle branch block, first-degree AV block at baseline, oversizing and eccentricity index as predictors of electrical disturbances after TAVI.44,47–50

It is known that anatomic variations in the AV node and the length of the nonpenetrating portion of the His bundle with respect to the membranous septum were associated with a higher risk of disturbances.10 Multimodal imaging assessment, including echocardiography, angiography and cardiac CT is important for guiding TAVI and preventing electrical disturbances. It may provide information regarding the location of the AV conduction axis relative to the aortic root and the depth of prothesis implantation.51–55

The main limitations of this study were its retrospective nature and the relatively short follow-up. Because we only analyzed the electrocardiograms before TAVI, at discharge and at the six month follow-up, it was not possible to assess accurately the exact point at which TAVI induces these electrical disturbances and intermittent changes. We also described a significant incidence of LBBB. It has been reported that growing operator experience and the new generation of transcatheter heart valves could reduce the rate of pPM implantation.56 These factors might also reduce electrical disturbances following TAVI.