Evaluation of Patients with Severe Aortic Stenosis after TAVI with Self-Expandable vs. Balloon-Expandable Devices ()
1. Introduction
Transcatheter aortic valve implantation (TAVI) has been introduced as a new therapeutic option for patients diagnosed with severe aortic stenosis (SAS) at high risk for surgical operation [1] [2] .
Transcatheter device development has been progressing rapidly during the past decade, and to date, this approach challenges surgical intervention as the preferred or the only option for managing symptomatic SAS [3] .
Recent research has explored if TAVI remains an alternative to surgical aortic valve replacement (SAVR) when surgical risk is low. To date, two large randomized controlled trials have been carried out to evaluate TAVI in patients with moderate surgical risk; both have documented TAVI as non-inferior to SAVR regarding stroke and all-cause mortality, whilst benefiting from a lower tendency to new acute kidney injury, major bleeding, or atrial fibrillation [4] [5] [6] .
Several new-generation devices for TAVI have been developed to overcome the limitations of the earlier ones [7] . Aortic prosthesis transcatheter placement requires either a self-expandable (SE) system (Medtronic Core Valve, Evolute R) or a balloon-expandable (BE) system (Edwards SAPIEN). Because the hemodynamic effects and complications of these valves are different and have not been studied enough, this study aims to evaluate the efficacy of these devices and compare their results and complications after midterm follow-up.
2. Methods and Materials
This study was quasi-experimental, as device selection was based on availability rather than randomization. The research took place at Rajaee Heart center and Dey clinic in Tehran, Iran. All patients with SAS who were at high risk for operation and were capable of undergoing TAVI from May 2012 to June 2017 were included in this study. Based on the availability of the devices and their indications for insertion, one patient went to either the BE group or the SE group. If severe calcification existed in the aortic valve (AV) or the left ventricular outlet, the BE device was preferred.
Since this was the starting point of the insertion of these types of devices in the AV, all patients who met the inclusion criteria and agreed to undergo TAVI instead of SAVR were included in the study.
The ethics committees of both participating centers approved this study. Additionally, all participants were provided with written informed consent for inclusion in the trial. TAVI candidates were only included in the study if they met all of the inclusion and none of the exclusion criteria. A questionnaire was given to each patient containing two sections: Section one was about the medical history and chief complications of patients, which was self-administered, while section two was about anatomical characteristics of the AV and annulus in echocardiography and multi-slice Computed Tomography (CT) scan which was filled out by a cardiologist. The inclusion criteria were comprised of 1) the presence of SAS, defined as a maximum AV area of 1 cm2 or a maximum indexed AV area of 0.6 cm2/m2, and 2) clinical symptoms described as the functional class of two or higher based on the New York Heart Association (NYHA) classification.
Contraindications to SAVR were anatomic appropriateness for either transfemoral vascular access or transcatheter device.
Primary exclusion criteria were hemodynamic instability, transfemoral access contraindications, a native AV annulus of less than 20 mm, and active endocarditis history. Additional contraindications that were also used were hypersensitivity or other contraindications for Clopidogrel, Heparin, or Aspirin use; active infection in need of antibiotics, and upper gastrointestinal bleeding within 3 months prior to the intervention.
Patients’ assessment was performed using transesophageal echocardiography, transthoracic echocardiography, left ventriculography, multi-detector CT scan, selective coronary angiography, as well as angiography of iliofemoral vessels and the aortic root for comprehensive evaluation of the aortic root anatomy in addition to the AV. Each multi-detector CT examination was evaluated locally by expert cardiac CT readers. 3D multidetector CT annular measurements included the mean, the minimum, and the maximum; perimeter, area, and diameter. The eccentricity index was used to describe annular eccentricity, defined as [1 – (minimum diameter/maximum diameter)]. The grading of the AV calcification was performed semi-quantitatively based on the observation of the amount of calcium on the Aortic valve by the echocardiographer: Grade (1) without calcification, Grade (2) mild calcification (small isolated spots), Grade (3) moderate calcification (multiple larger spots), and Grade (4) heavy calcification (all cusps extensively calcified). The outflow tract of the left ventricle was separately analyzed semi-quantitatively for the presence, location, and amount of calcification. To conduct TAVI, a multidisciplinary team comprised of a cardiac surgeon, an anesthesiologist, and an interventional cardiologist was responsible for the final decision.
The SE system included the Core Valve system and also the newer generation Evulote R valves, consisting of porcine pericardial tissue sewn to form a trileaflet valve mounted within a self-expanding hourglass-shaped nitinol frame. The prosthetic size was determined by the external diameter of the ventricular end.
The BE system included a cylindrical cobalt-chromium stent onto which 3 leaflets made of bovine pericardium were mounted. Edwards SAPIEN was used as the BE valve.
The selection of the device size was performed according to the sizing charts issued by the manufacturer; however, it was recommended by the steering committee to do the sizing based on 3D imaging and the multi-detector CT-based annular area preferably. The currently utilized transfemoral delivery system has 16-F through 20-F catheters.
The procedures were mainly carried out under sedation (no endotracheal intubation) with the aid of fluoroscopic guidance. Moreover, in all patients, transesophageal echocardiography was performed as the appropriate guidance. The SE valve positioning was performed in a controlled fashion, either under slow- rapid pacing or without pacing, with limited realignment potential.
The BE device was positioned under rapid pacing without the use of cardiopulmonary support. Complete preprocedural revascularization was performed in cases that were diagnosed with significant coronary artery disease.
2.1. Valve Function Assessment
After the deployment of the valve, the valve function assessment was carried out using transthoracic echocardiography, invasive hemodynamic measurements, and angiography.
After the wire was retrieved from the ventricle, the angiographic assessment was carried out with the aid of a 6- or 5-F pigtail catheter positioned in the implanted valve’s superior segment above the cusps within the ascending aorta.
Aortographies were recorded in the 45˚ left anterior oblique and the 30˚ right projections over several cardiac cycles. The contrast amount was standardized to permit adequate angiographic evaluation (minimum of 25 mL with a flow rate of 20 mL/s). We semi-quantitatively assessed aortic regurgitation (AR) by the estimation of the circumference proportion: more than 20% was considered severe, 10% to 20% moderate, and up to 10% mild paravalvular AR [8] [9] .
An experienced interventional echocardiographer performed the evaluation on-site. The invasive hemodynamic assessment involved measuring the aortic diastolic pressure, end-diastolic pressure of the left ventricle, and residual transprosthetic gradient. The dimensionless AR index was calculated as ([diastolic blood pressure − left ventricular end-diastolic pressure]/systolic blood pressure) × 100.
Throughout follow-up, the assessment of valve function was performed by transthoracic echocardiography at two prearranged sessions (24 hours, 90 days).
2.2. Follow-Up and Endpoints
Electrocardiography was conducted at multiple time points after valve implantation, including 1 hour after the procedure, 24 hours later, daily throughout the first week, and immediately prior to discharge. Additionally, blood tests were performed, including a complete blood count, as well as renal and liver function tests, 24 hours after the procedure. During hospitalization and for one week after discharge, patients were closely monitored for any adverse events. Further follow-up visits were scheduled for 3 months to ensure continued monitoring of patient health.
The primary endpoint of the trial was device success as defined by the third Valve Academic Research Consortium document consisting of 1) technical success (immediate success of a procedure, which is measured at the time of leaving the procedure room and encompasses the true technical safety of the device and its delivery), 2) freedom from mortality, 3) freedom from surgery or intervention related to the device (excluding permanent pacemaker) or a major vascular or access-related or cardiac structural complication, and 4) intended performance of the valve (mean gradient < 20 mmHg, peak velocity < 3 m/s, Doppler velocity index ≥ 0.25, and less than moderate AR) [10] .
The secondary endpoints were about the complications of device insertion such as complete heart block, pericardial effusion, atrial fibrillation, sepsis, vascular complications, myocardial infarction (MI), decompensated heart failure (DHF), and stroke that were compared between the two types of valves, immediately as well as after ninety days.
Immediate post-procedural AR assessment was performed as a criterion for the primary composite endpoint of this study via transesophageal echocardiography and angiography.
Continuous variables were compared using a two-sided unpaired t-test and noncontinuous variables were analyzed by ANOVA and the numbers were reported using mean ± SD.
There were no missing data on the primary endpoint.
A P-value < 0.05 was considered statistically significant and All tests were two-sided. No adjustment was made for the primary and secondary endpoint comparisons. Statistical analyses were carried out via SPSS software 16.
3. Results
The total number of patients was 60 (32 in the BE group and 28 in the SE group).
41 patients were included from Rajaee Heart Center, and 19 patients were included from Dey clinic. The mean age of patients who underwent TAVI for the SE group was 81.2 ± 8 years, and for the BE group was 79.8 ± 7 years.
According to Table 1, the basic characteristics of patients such as gender, age, height, body weight, diastolic and systolic blood pressure, and EuroSCORE and STS score in the SE group and the BE group were not significantly different (P > 0.05).
Past medical history of the two groups such as hypertension, the history of diabetes mellitus, ischemic heart disease (IHD), hyperlipidemia, cerebrovascular accident (CVA), and chronic kidney disease (CKD) did not have any significant differences (P > 0.05).
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Table 1. Basic characteristics of patients.
NYHA = New York heart association; Hlp = hyper lipidemia; CABG = coronary artery bypass graft.
Echocardiography and CT scan findings of patients are illustrated in Table 2 and Table 3.
The mean ejection fraction (EF) in patients in the SE group was 40.23 ± 14 while in the BE group was 43.7 ± 10 (P = 0.733).
The mean pulmonary artery pressure (PAP) in the SE group was 40.7 ± 18 mmhg while in the BE group was 41 ± 13 mph (P > 0.05).
The mean aortic area, mean aortic gradient, eccentric index, and the mean and the maximum diameter of the aortic annulus did not vary significantly between the BE group and the SE group (P > 0.05).
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Table 2. Transthoracic and transesophageal characteristics of patients before TAVI.
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Table 3. CT scan characteristics of patients before TAVI.
Moderate to severe Aortic regurgitation immediately after angiography was found in 16% of patients in the self-expandable group versus 27% in the balloon-expandable group (P > 0.05).
On the other hand, echocardiography revealed that 40% of patients experienced moderate AR after one week in the SE group compared to only 23% of patients in the BE group (P > 0.05).
Outcomes and Procedural Details
Procedural details and outcomes are demonstrated in Table 4 and Table 5. The 26-mm valve was the most common valve used in the BE group (20, 62.5%), whereas in the SE group the most frequently implanted valve was the 29-mm valve (14, 50%).
There was only one case of in-hospital mortality. Mortality occurred in 12 (20%) cases (5 cases in the SE group and 7 cases in the BE group). The cause of mortality was 66.6 % (8 cases) cardiac (3 cases of MI, 2 cases of DHF, 3 cases of SCD) and 33% none cardiac (1 case of ICH, 2 cases of sepsis, 1 case of hepatic liver cancer).
According to Table 6, no significant differences were found in the total mortality rate between the SE and the BE groups; the mortality rate was 5 (41.6%) in the SE group versus 7 (58.3%) in the BE group (P > 0.05).
Pneumonia led to hospital admission in one case from the BE group and two cases from the SE group (P > 0.05).
According to Table 7, severe pericardial effusion leading to urgent drainage of fluid from the pericardial space occurred in one patient in the BE group and one patient in the SE group (P > 0.05).
Complete heart block leading to the cardiac pacemaker occurred in 3 cases (10%) in the BE group and 6 cases (21%) in the SE group (P > 0.05).
No other significant difference was found between the two groups (P > 0.05).
4. Discussion
The therapeutic possibilities for successful management of severe AS have been expanded by the introduction of TAVI. Every year new devices are developed to treat these patients; however, the efficiency and complications of these devices, especially in the Middle East, have not been sufficiently studied. The present analysis is a quasi-experimental study that describes the outcomes of TAVI patients with the midterm follow-up using the self-expanding Core Valve System and the balloon-expanding Edwards SAPIEN device.
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Table 6. Clinical outcome on the 90th day.
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Table 7. Morbidity during TAVI in the self-expandable and the balloon-expandable groups.
GIB = gastro intestinal bleeding; MI = myocardial infarction; RBBB = right bundle branch block; LBBB = left bundle branch block; CHB = complete heart block.
Moderate to severe Paravalvular leakage in both groups did not differ substantially either by immediate aortography after the procedure or echocardiography after seven days.
In the Choice study, unlike our research, the self-expanding Core Valve cases had a higher occurrence of moderate to severe paravalvular leakage compared to the balloon-expanding Edwards SAPIEN group [11] .
The differences between the choice study with our study may be due to the use of Evolute R in the self-expandable group which had a lot less paravalvular leakage (only 2 out of 10 Evolute R valves had moderate to significant paravalvular leakage). Moreover, unlike the choice study, in our study paravalvular leakage did not decrease after one week. It seems that echocardiography, due to the lack of precision to detect paravalvular leakage, may influence the results (Table 8).
The success rate of devices used in the procedure was 97%, with only one failure due to the device not passing through a severely calcified aorta. The average fluoroscopic time and amount of contrast used were comparable to similar research conducted in Italy and Germany [11] .
The most common causes of mortality were myocardial infarction and decompensated heart failure after valve implantation. Upon closer examination of Table 9, it becomes evident that while TAVI was performed on only 28 patients (46.6%) from 2016 onwards, only one mortality (3%) was reported in these cases (P < 0.05). This suggests that as the TAVI team gained more experience in recent years, the mortality rate dropped dramatically.
The higher rate of mortality in our study may be due to the higher age and EuroSCORE as well as the lower ejection fraction of our patients, especially at the beginning of the study. However, two out of the three sepsis cases that led to death sparked more attention to sterilization and hygiene management pre-pro- cedurally, and also the use of more potent antibiotics during and after the intervention.
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Table 8. Mortality causes in self-expandable and balloon-expandable groups.
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Table 9. Mortality rate regarding time and center.
5. Study Limitation
The lack of standard imaging for detecting paravalvular leakage was one of the limitations of this study. Additional limitations were incomplete patient sheets as well as a lack of scheduled and regular patient follow-ups. Finally, as this research studied the patients who underwent TAVI for the first time after this procedure’s introduction in Iran, our sample size and their complication rate were also limited.
6. Conclusions
In conclusion, the balloon-expandable group (Edwards SAPIEN) did not have decreased paravalvular leakage in comparison with the self-expandable group (Core Valve and Evolute R).
The morbidity and mortality rates between the balloon-expandable and the self-expandable groups did not differ significantly.
Recommendations
It is highly recommended to conduct a study with a larger sample size and a longer follow-up period. It is also suggested to use stronger antibiotics before and after the procedure. In case of any signs of infection, consulting with infectious disease specialists is advised. Accurate evaluation of patients, especially during the initial weeks following the procedure, with regard to signs of decompensated heart failure, through echocardiography and regular patient follow-up can lead to lower mortality and morbidity rates.
Ethics Approval
All patients participating in this study provided written informed consent and the study was approved by the ethical committees of both participating centers. The study was performed in accordance with the declaration of Helsinki.
Authors’ Contribution
Mohammad Nourizadeh was responsible for the study concept and design. All authors intercepted the data, drafted the manuscript, approved the final manuscript, and agreed to be accountable for all aspects of the work.