Comparative Analysis of the Kinetic Behavior of Systemic Inflammatory Markers in Patients with Depressed versus Preserved Left Ventricular Function Undergoing Transcatheter Aortic Valve Implantation

Background: Prior studies have proven the safety and efficacy of transcatheter aortic valve implantation (TAVI) in patients with reduced left ventricular (LV) function. This study’s aim was to investigate periprocedural inflammatory responses after TAVI. Methods: Patients with severe symptomatic aortic stenosis and reduced LV function who underwent transfemoral TAVI were enrolled. A paired-matched analysis (1:2 ratio) was performed using patients with preserved LV function. Whole white blood cells (WBC) and subpopulation dynamics as well as the neutrophil to lymphocyte ratio (NLR) were evaluated at different times. Results: A total of 156 patients were enrolled, including 52 patients with LVEF < 40% 35.00 [30.00, 39.25] and 104 with LVEF > 50% 55.00 [53.75, 60.0], p < 0.001. Baseline NLR in the reduced LV function group was significantly higher compared to the preserved LV function group, 2.85 [2.07, 4.78] vs. 3.90 [2.67, 5.26], p < 0.04. After a six-month follow-up, the inflammatory profile was found to be similar in the two groups, NLR 2.94 [2.01, 388] vs. 3.30 [2.06, 5.35], p = 0.288. No significant mortality differences between the two groups were observed in the long-term outcome. Conclusions: TAVI for severe symptomatic aortic stenosis, with reduced LV function, was associated with an improvement in the inflammatory profile that may account for some of the observable benefits of the procedure in this subset of patients.

Atherosclerosis and degenerative aortic stenosis have common risk factors and etiopathogenesis, and inflammation appears to play an important role in this respect. Furthermore, systemic inflammation has been recognized as a dominant feature in the progression of heart failure [9][10][11]. Specifically, inflammation has been linked to disease development, progression, and associated complications, and is predictive of poor patient outcomes, independent of LVEF [12][13][14]. One such inflammatory biomarker is the NLR, which is derived from routine complete blood counts. The NLR leverages early hematological observations in which the absolute neutrophil count is positively associated with cardiovascular events, while the absolute lymphocyte count is negatively associated with cardiovascular 2 of 11 events [15,16]. Moreover, while total white blood cell counts have been shown to predict cardiovascular risk, the NLR appears to be a superior predictor [17]. Some studies have evaluated the NLR as a predictor of total mortality in the setting of acute coronary interventions [17,18] and heart failure [19].
We aimed to compare the kinetic behavior of inflammatory profile after TAVI in patients with preserved or reduced LV function by measuring the NLR biomarker as a potential mediator of outcome improvement from the procedure.

Study Population
We retrospectively included patients with severe symptomatic aortic stenosis who underwent TAVI in our center between January 2010 and March 2020. This study was approved by Kaplan Medical Center's IRB. We excluded patients with chronic systemic inflammatory or autoimmune diseases, acute infections, hematological disorders, malignancies, dialysis, or treatment with agents affecting the white blood cell count, e.g., corticosteroids. Patients who did not have repeated blood tests and those with periprocedural death (up to 72 h after TAVI) were excluded as well.

TAVI Procedure
The type and size of the valves were at the discretion of the local heart team, and a decision was made according to the patient's anatomical and clinical characteristics. Patients treated with BEV were implanted with either SAPIEN, SAPIEN XT, or S3 (Edwards Lifesciences, Irvine, CA, USA) valves. Patients treated with SEV were implanted with either CoreValve, Evolut PRO, or Evolut R (Medtronic, Inc., Minneapolis, MN, USA) valves. The small number of subjects treated with other valves were also excluded from the analysis. Transfemoral vascular access and closure was performed using the percutaneous approach with the safety wire technique and the Prostar XL (Abbott Vascular, Redwood City, CA, USA) vascular closure device. The procedure duration was calculated as "skin-to-skin", i.e., time 0 marked the beginning of arterial blood pressure regulation by the accessory support access and the final time was represented by the termination of this accessory support access. Following that, we also used local anesthesia with conscious sedation as a first-line approach. All patients received unfractionated heparin to maintain a minimum active clotting time of >250 s after the insertion of the femoral sheet. Protamine (1 mg for each 100 U of heparin, maximal dose 50 mg) was administered at the time of vascular closure if needed. The use of prophylactic antibiotics during the procedure or hospital stay was routinely avoided. Aspirin was recommended before TAVI. Dual-antiplatelet treatment with 100 mg of aspirin and 75 mg of clopidogrel was started the day before the procedure and followed thereafter for six months, except for patients requiring chronic oral anticoagulation.

Inflammatory Markers
Baseline characteristics, procedural data, and clinical outcomes were collected. Blood samples were obtained using a 21G sterile syringe without stasis. Laboratory analyses were performed before the procedure, during the patient's postprocedural intensive care unit stay on a daily basis, and at the physician's discretion in the cardiology ward. These were retrospectively collected. The neutrophil-lymphocyte ratio (NLR) was calculated using this formula: NLR = absolute neutrophils count/absolute lymphocytes count.

Definition Criteria for Events
All the outcome definitions were strictly determined according to the Valve Academic Research Consortium 2 (VARC-2) criteria. All of these standardized endpoint definitions together represent the major adverse cardiovascular events (MACE) in our study. Clinical follow-up included 30-day and six-month visits after hospital discharge. The follow-ups were performed on site.

Matching
The reduced LV function cohort (LVEF < 40%) was compared to a preserved LV function cohort (LVEF > 50%), using matched-pair grouping for statistical analysis in a retrospective and descriptive manner. Patients suffering mid-range LV dysfunction, i.e., LVEF between 40% to 50%, or severely depressed LV function (LVEF ≤ 25%), were excluded. Matched patients were also selected during the same time period out of 104 patients undergoing TAVI. Age ± 5 years, sex, BMI ± 5, dialysis and additive EuroSCORE ± 5 were used for matched-pair analysis (1:2). Thus, a total of 156 patients were matched and compared. We performed a propensity score to build the matching groups.

Statistical Analysis
Data are presented as median values (with ranges in parentheses). Continuous variables between the various study groups were tested for normality with a Shapiro-Wilk test and when an abnormal distribution was found, a Mann-Whitney test was performed. When the distribution was normal, a t-test was used. Pearson's chi-square test was performed for categorical variables when appropriate. Main effect estimates are presented with their 95% confidence interval. Statistical analysis was performed using SPSS software (IBM SPSS Statistics for Windows, Version 25.0., Armonk, NY, USA) and R programming version 4.0.2 (The R Foundation for Statistical Computing, Vienna, Austria; http://www.R-project.org) (accessed date 1 June 2021) for all analyses. Where the p values were less than 0.05, these were considered statistically significant.

Pre-Procedural Data
During the ten-year study period, 370 consecutive patients were enrolled. The study flowchart is shown in Figure 1. According to our definitions, a total of 56 patients were excluded. The analyzed population included 314 patients (43% female, with a median age of 81.00 [76.00-85.00] years old), with severe symptomatic aortic stenosis (transaortic pressure gradient 37.00 [29.50-47.00] mmHg), and high or prohibitive operative risk (an STS score of 8.01 [5.1-10.3]). Baseline and procedural characteristics of the 1:2 matched study population according to ejection fraction are summarized in Table 1.   The clinical profile and executive procedural characteristics showed no significant differences between the two 1:2 matched population group types at baseline. As expected, according to the study aims, compared with patients with preserved LV function, LV function was significantly depressed in the reduced LV group, LVEF 55. 00%

Procedural Data
Inflammatory marker dynamics: baseline total WBC, absolute cell counts of neutrophils, lymphocytes, and NLR and their dynamic changes after TAVI for the total study population are summarized in Table 2. In the entire 1:2 matched population, we noticed that there were significant kinetic changes in the WBC response (p value < 0.0001) from admission, to 24 h post procedure, to 72 h post procedure, with significant increases in WBC, neutrophils, and NLR, and significant decreases in absolute lymphocyte counts. Figure 2 shows the dynamic changes of white blood cells and the differential subsets in the entire study population at different times during the first 24 h and 72 h, and at six months post procedure. There was a significant increase in inflammatory markers, including total WBC, neutrophils, and NLR in all the study 1:2 matched population. When comparing the two subgroups as shown in Table 3 and Figure 3, patients with reduced left ventricular function had a significantly more pronounced inflammatory response at baseline. However, six months after TAVI, there was a similar extent of reduction in the inflammatory markers to about the same level of the in-patients, with reduced NLR compared to preserved ejection fraction, NLR        Values are presented as: median (ranges). Abbreviations: WBC = white blood cells; NLR = neutrophils to lymphocytes ratio. In a variable analysis for factors that may influence inflammatory markers post-TAVI for the whole study population, we found significant differences only in the procedure duration and contrast volume injected (Table 4). Data are presented as: median (ranges). Continuous variables between the various study groups were tested for normality by a Shapiro-Wilk test and when abnormal distribution was found, a Mann-Whitney test was performed. When the distribution was normal, a t-test was used. * Correlation between two continuous variables were tested by a Pearson's correlation. Abbreviations: TAVI = transcatheter valve implantation; BMI = Body mass index; AF = atrial fibrillation; CAD = coronary artery disease; PAD = peripheral arterial disease; LVEF = left ventricle ejection fraction; SEV = self-expandable valve; BEV = balloon-expandable valve; WBC = white blood cells; Abs = absolute; NLR = neutrophils to lymphocytes ratio.

Clinical Outcomes
The thirty-day clinical outcomes according to the VARC-2 criteria are summarized in Table 5. We found no differences between the two subgroups according to MACE and mortality. The Kaplan-Meier survival curve at the four-year follow-up is shown in Figure 4. During the ten-year study period, we found no significant differences between the two groups according to the ejection fraction (p = 0.35).

Clinical Outcomes
The thirty-day clinical outcomes according to the VARC-2 criteria are summarized in Table 5. We found no differences between the two subgroups according to MACE and mortality. The Kaplan-Meier survival curve at the four-year follow-up is shown in Figure  4. During the ten-year study period, we found no significant differences between the two groups according to the ejection fraction (p = 0.35).

Discussion
We have presented a matched-pair analysis comparing inflammatory biomarker behavior in patients who underwent TAVI for symptomatic severe aortic stenosis in two different cohorts: patients with reduced LV function versus patients with preserved LV function. The major findings of our study were: (i) the enhanced inflammatory state in patients with reduced LV function compared with preserved LV function is reflected by a higher baseline NLR; (ii) the effect of the TAVI on the reduction of the NLR inflammatory marker in the reduced LV group caught up with the NLR in the preserved LV function group after six months of follow-up; (iii) there are similarly favorable clinical outcomes, independent of the baseline LV function.
Inflammation contributes to the pathogenesis and progression of heart failure (HF) [12] as well as degenerative aortic stenosis [20,21]. Elevated inflammatory biomarkers, including NLR, were reported in the TIME-CHF study [9] that enrolled elderly patients with HF and severe aortic stenosis who were candidates for surgical replacement [22][23][24]. Our findings of elevated NLR in patients with severe aortic stenosis and reduced LV function are concordant with the publication of Avci et al. [22], who found higher NLR in patients presenting with these two entities. In our study, we added another parameter when analyzing the effect of TAVI on the inflammatory profile six months after the procedure, which mirrors complete resolution from inflammation-related features associated with the procedure.
Our findings are in agreement with the recent publication of Baratchi et al. [25], who found an anti-inflammatory effect of TAVI reflected by a significant reduction in the NLR. One possible pathophysiologic explanation is that the reduction of NLR after TAVI in patients with reduced LV function may be related to the effect of TAVI in decreasing hemodynamic resistance, which lowers the high shear stress that activates and perpetuates the inflammatory state, as experimentally demonstrated in the Baratchi publication [25].
Other significant baseline characteristic differences found were septum thickness, aortic valve area, and mean aortic valve gradient. These issues reflect the underling pathophysiology of patients with reduced LV function, which are superimposed with significant aortic stenosis activated compensatory pathways (i.e., chamber remodeling). These parameters are not statistically significant in the variable analysis (Table 4).
Finally, as described in the pivotal PARTNER study [5] and other studies [5,6,26], we show that there are no differences in the long-term mortality rates between patients with decreased or preserved LV function after TAVI. The apparent normalization of the inflammatory markers by TAVI, which was more pronounced in the patients with baseline reduced EF, may be associated with the observation that despite the presence of preexisting LV dysfunction, these patients do not have a poorer short-term outcome. However, this should be tested in larger cohorts and for extended periods of follow-up.
To the best of our knowledge, this is the first report that compares the inflammatory state behavior and kinetics in patients undergoing TAVI with low ejection fraction versus those with preserved LV function. In conclusion, we found that TAVI has a more pronounced anti-inflammatory effect in patients with a low baseline ejection fraction, and this effect may partly account for the beneficial clinical response, which is translated to similar outcomes when compared to patients with preserved LV function. Informed Consent Statement: Individual patient consent was waived because of the study's retrospective design and the data collection from routine care.