Comparison Between Saddle Versus Non-Saddle Pulmonary Embolism: Insights from Nationwide Inpatient Sample
Authors: Pathak Ranjan , Giri Smith , Aryal Madan Raj , Karmacharya Paras , Donato Anthony A 
Published: October 2019

Abstract
Introduction
Saddle pulmonary embolism (PE), defined as thrombi at the bifurcation of pulmonary artery, occurs in about 2-5% of all PE cases. Due to relative rarity of this condition, studies aimed at describing the clinical attributes and outcomes have been limited by small sample size. Although clot burden was once believed to be important prognostically, recent data has challenged this assumption.
Methods
We used the Nationwide Inpatient Sample to identify all hospitalizations related to acute pulmonary embolism in the United States from the year 2009 to 2011. Nationwide Inpatient Sample is the largest all-payer publicly available inpatient care database in the US. It contains data from five to eight million hospital stays from about 1,000 hospitals across the country and approximates a 20% sample of all US hospitals. Using the appropriate International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes, the study cohort was divided into saddle and non-saddle groups. Baseline demographic and hospital characteristics, comorbidities, in-hospital mortality and complications were compared between the two groups. Data analysis was done using STATA, version 13.0 (College Station, TX).
Results
A total of 861,762 acute PE related hospitalizations were identified during the study period. Saddle PE was coded in 1472 (0.16%) hospitalizations. A significantly greater proportion of saddle PE cases were seen among males (p =0.01), obese (p<0.001), dyslipidemic (p<0.001) and diabetic patients (p<0.001). Although the in-hospital mortality rate was similar in the two groups (3.62% versus 3.19%, p=0.73), rates of cardiac arrest, cardiogenic shock, respiratory failure and thrombolysis were significantly higher in saddle PE.
Conclusion
Saddle PE carries similar prognosis compared to patients without this finding. Whether thrombolytics are necessary in hemodynamically stable patients is a matter for further study.
Table 1. Univariate analysis of baseline characteristics, Saddle PE vs Non-saddle PE Characteristics Saddle PE (n=1,427) Non-saddle PE (n=186,335) p Age in years Mean 62.71±15.10 62.14±17.37 0.49 Male sex 53.83 46.03 0.02 Race 0.05 White 79.69 74.09 Black 11.78 17.22 Hispanic 4.8 5.33 Others/unknown 3.73 3.36 Insurance status 0.29 Medicare 46.66 50.23 Medicaid 6.7 8.87 Private insurance 36.43 32.41 Self-Pay 4.83 4.68 No charge 1.01 0.50 Other 4.36 3.31 Region 0.36 Northeast 19.49 18.01 Midwest 22.13 25.52 South 35.12 37.18 West 23.26 19.29 Location/teaching status <0.001 Rural 6.23 13.59 Urban nonteaching 40.9 43.39 Urban teaching 52.86 43.03 Bed-size 0.21 Small 12.20 13.12 Medium 20.77 25.05 Large 67.03 61.79 Weekend admission 22.92 22.22 0.78 Comorbidities Smoking 31.64 27.21 0.15 Obesity 25.06 17.96 0.008 Dyslipidemia 38.28 32.48 0.05 Hypertension 59.01 56.02 0.29 Diabetes mellitus 29.02 23.27 0.03 PVD 2.62 3.49 0.38 CAD 12.94 16.26 0.13 AKI 14.31 8.08 0.002 CKD 8.31 9.63 0.41 Stroke 1.02 0.73 0.62 Sepsis 0.97 1.17 0.72 Cardiac dysrhythmias 21.15 19.02 0.42 Acute CHF 11.85 12.73 0.65 Cardiac arrest 3.27 1.09 0.03 Syncope 2.97 1.85 0.24 Cardiogenic shock 3.03 0.57 0.04 Respiratory failure 19.84 8.27 <0.001 Thrombolysis 3.98 0.56 0.005 Intubation 3.84 1.93 0.08
AKI=Acute Kidney Injury; CAD=Coronary Artery Disease; CHF=Congestive Heart Failure; CKD=Chronic Kidney Disease; PE=Pulmonary Embolism; PVD=Peripheral Vascular Disease
Table 2. Mean hospital charge, LOS and In-hospital mortality, Saddle PE vs Non-saddle PE Saddle PE Non-saddle PE p Mean hospital charge 63,517 36,727 <0.001 mean LOS 6.95 5.24 <0.001 In-hospital mortality 3.62 3.09 0.669
LOS=Length of Stay; PE=Pulmonary Embolism

Disclosures
No relevant conflicts of interest to declare.