Evaluating the Hemodynamic Impact of Saddle Versus Non-Saddle Pulmonary Embolism: Insights From a Thrombectomy Cohort

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J INVASIVE CARDIOL 2024. doi:10.25270/jic/24.00156. Epub June 17, 2024.

Objectives. The aim of this study was to compare the hemodynamic impact and clinical outcomes of saddle vs non-saddle pulmonary embolism (PE).

Methods. This was a retrospective analysis of clinical characteristics and outcomes among patients with saddle and non-saddle PE within a cohort referred for catheter-based thrombectomy (CBT) with invasive hemodynamic assessments. Patients who underwent CBT between August 2020 and January 2024 were included. The primary outcome was the proportion of patients with a low cardiac index (CI < 2.2 L/min/m²). Secondary outcomes included 30-day mortality, intensive care unit (ICU) length of stay (LOS), and hospital LOS.

Results. A total of 107 patients (84 intermediate risk, 23 high-risk; mean age 58 years, 47.6% female) were included in the study, with 44 patients having saddle PE and 63 having non-saddle PE. There were no significant differences in baseline demographics and clinical characteristics between saddle and non-saddle PE, including rates of high-risk PE (25% vs 16%, P = .24), rates of RV dysfunction, pulmonary artery systolic pressure (55 vs 53 mm Hg, P = .74), mean pulmonary artery pressure (34 mm Hg vs 33 mm Hg), low cardiac index (56% vs 51%, P = .64), rates of normotensive shock (27% vs 20%, P = .44), or Composite Pulmonary Embolism Shock scores (4.5 vs 4.7, P = .25). Additionally, 30-day mortality (6% vs 5%, P = .69), ICU LOS, and hospital LOS were similar between the groups.

Conclusions. Among patients undergoing CBT, there were no significant differences in invasive hemodynamic parameters or clinical outcomes between those with saddle and non-saddle PE.

Acute pulmonary embolism (PE) ranks as the third leading cause of cardiovascular death in the United States, with most PE-associated fatalities attributed to acute right ventricular (RV) failure from RV ischemia resulting from a sudden surge in RV afterload due to flow-limiting clot burden.^1-3 Computed tomography angiography (CTA) is the primary diagnostic and prognostic tool for PE, as it describes the presence and extent of PE while offering crucial insights into RV dysfunction. The assumption that a saddle PE, which is defined by a thrombus spanning the main pulmonary artery bifurcation, equates to a severe, hemodynamically significant PE is prevalent. Contrary to this assumption, limited data support this perspective, and are often derived from extrapolation of autopsy studies noting a relatively high incidence of saddle PE during postmortem exams.^4-6 However, the literature suggests that thrombus burden may have a more pronounced hemodynamic impact.^7,8 Conversely, assuming that a non-saddle PE indicates a less severe prognosis may pose risks, as the care team could develop a false sense of stability in the absence of a saddle PE. In our study, we conducted a comparative analysis of clinical characteristics and outcomes among patients with non-saddle and saddle PE within a cohort specifically referred for catheter-based thrombectomy (CBT) with invasive hemodynamic assessments.⁹ The primary objective was to examine and compare the hemodynamic impact of saddle vs non-saddle PE in this selected patient population.

Patients who underwent CBT between August 2020 and January 2024 were included in the study. The study was approved by the New York University Institutional Review Board with a waiver of informed consent. All patients undergoing CBT (FlowTriever device, Inari Medical) underwent invasive hemodynamic evaluation. The primary outcome was the proportion of patients with a low cardiac index (pre-procedural invasive measures of CI < 2.2 L/min/m²). Secondary outcomes included 30-day mortality, normotensive shock, intensive care unit (ICU) length of stay (LOS), and hospital length of stay. The decision to proceed with CBT was at the recommendation of the PE Response Team (PERT). Simplified Pulmonary Embolism Severity Index (sPESI) and Composite Pulmonary Embolism Shock (CPES) scores were calculated as previously described.^10,11 For the CPES score, 1 point each was assigned to an elevated troponin, an elevated B-type natriuretic peptide (BNP), the presence of moderate or severe reduction in RV systolic function on transthoracic echocardiogram, the presence of central thrombus, concomitant deep vein thrombosis, and tachycardia.^10,12

Continuous variables were presented using mean ± standard deviation or median with interquartile range for skewed data, while categorical data were expressed as frequency and proportions. Paired Student’s t-test or Wilcoxon signed-rank test was applied for continuous variables based on normal distribution assumptions. Categorical variables were compared using χ2 test or Fisher exact test. A 2-sided P-value less than 0.05 was considered significant. All analyses were performed using Stata 18 software (StataCorp LP).

A total of 107 patients (84 intermediate risk, 23 high-risk, mean age 58 years, 47.6% female) were included in the study; 44 patients had saddle PE and 63 patients had non-saddle PE. Overall, there was no significant difference in baseline demographics and clinical characteristics between the 2 groups (Table). There were no statistically significant differences in the proportion of high-risk PE (25% vs 16%, P = .24), rates of RV dysfunction (100% vs 100%), pulmonary artery systolic pressure (PASP) (55 vs 53 mm Hg, P = .74), mean pulmonary artery pressure (mPAP) (34 mm Hg vs 33 mm Hg), pre-procedure cardiac index (2.2 vs 2.4 L/min/m²), low cardiac index (56% vs 51%, P = .64), rates of normotensive shock (27% vs 20%, P = .44), or CPES score (4.5 vs 4.7, P = .25) between the saddle and non-saddle PE groups. Moreover, the 30-day mortality (6% vs 5%, P = .69), ICU LOS (3 [IQR 3, 5] vs 4 [IQR 3,6], P = .41), and hospital LOS (8 [IQR 5,18] vs 4 [IQR 6,14], P = .92) were largely similar. These findings were similar when restricted to the intermediate-risk group only.

Our study aimed to address the prevailing assumption that saddle PE signifies a more severe and hemodynamically significant condition compared with non-saddle PE. We found that among patients undergoing CBT for PE, there were no significant differences in clinical outcomes between those with saddle and non-saddle PE, which is consistent with prior studies.^7,13 Importantly, to our knowledge, this is the first study to directly compare invasive hemodynamic parameters between patients with saddle vs non-saddle PE. Our findings reveal no differences in hemodynamic parameters such as PASP, mPAP, or cardiac index between the 2 groups. These findings are likely explained by the complex interplay of thrombus location, burden, variable compensatory responses based on pre-existing cardiorespiratory disease, and time to therapeutic anticoagulation.^14-16 The comparable outcomes and invasive hemodynamics observed in patients with saddle and non-saddle PE underscore the importance of exercising caution in interpreting the severity of PE based solely on the presence or absence of a saddle thrombus. Instead, a comprehensive evaluation of hemodynamic status, RV function, and clinical presentation is warranted to guide appropriate management strategies.

Limitations. Our results should be interpreted in consideration of certain limitations. First, this was a single-center retrospective study of patients referred for CBT (specifically with FlowTriever) with invasive hemodynamic data, which is subject to inherent biases and limits the generalizability of our findings to the broader population of PE patients who did not undergo CBT.  Second, our findings are confined to patients who survived until hospitalization and underwent diagnostic testing followed by CBT. Third, our dataset is limited to the information collected during the initial study design, which focused primarily on comparing the hemodynamic and clinical outcomes between saddle and non-saddle pulmonary embolism within the cohort. Future research with a more detailed breakdown of non-saddle thrombi characteristics would be beneficial to address this gap.

Among patients referred for CBT, there were no significant differences in invasive hemodynamic parameters or clinical outcomes between those with saddle and non-saddle PE.

From the ¹Division of Cardiovascular Medicine, New York University, New York, NY, USA; ²Department of Medicine, NYU Grossman School of Medicine, New York, NY, USA; ³Division of Pulmonary Critical Care, and Sleep Medicine, NYU Grossman School of Medicine, NY, USA.

Disclosures: Dr. Bangalore serves on the advisory boards for Abbott Vascular, Boston Scientific, Biotronik, Amgen, Pfizer, Merck, REATA, Inari, Imperial Health, and Argon. The remaining authors report no financial relationships or conflicts of interest regarding the content herein.

Address for correspondence: Sripal Bangalore, MD, MHA, New York University School of Medicine, New York, NY 10016, USA. Email: sripalbangalore@gmail.com; X: @sripalbangalore