Sub-segmental Pulmonary Embolism (SSPE):

An Incidental or Clinically Significant Finding?

Tarun Dalia, MD PGY- 3

Department of Internal Medicine University of Kansas Medical Center

What is Sub-segmental PE?

□ PE that involves 5th order pulmonary artery branches.

Why is it an important entity to discuss? ❑ Rate of SSPE detection has gone up from 4% (single detector) to 15%

(64 detector scanner CT). [1]

❑ Since introduction of CTPA, the rate of PE detection is increased by 80% from 1998 to 2006, without an associated increase in PE mortality nationally. [2]

1. Peiman S et al. Subsegmental pulmonary embolism: A narrative review. Thromb Res. 2016 Feb;138:55-60. doi: 10.1016/j.thromres.2015.12.003. Epub 2015 Dec 8. Review.

2. Wiener RS, Schwartz LM, Woloshin S. Time trends in pulmonary embolism in the United States: evidence of overdiagnosis. Archives of internal medicine. 2011;171:831-7.

SSPE: Is It Clinically Significant?□ May be artifact in some patients

■ Non PE protocol/ Patient motion/ Non expert reader □ Small thrombus burden

Almost Data free Zone?□ Meta-analysis of 14 studies (largest study with 715 SSPE patients) [3]

■ 589 anticoagulated and 126 not anticoagulated ■ F/U only 3 months ■ Most studies lacked clinical details of patients characteristics.

Chest Guidelines 2016: Essentially Expert opinions [4]

■ Anticoagulate in those considered high risk ■ Do not anticoagulated those considered low risk

3. Bariteau A et al. Systematic Review and Meta‐analysis of Outcomes of Patients With Subsegmental Pulmonary Embolism With and Without Anticoagulation Treatment. Academic Emergency Medicine. 2018. 4. Kearon C et al Antithrombotic Therapy for VTE Disease: CHEST Guideline and Expert Panel Report. Chest. 2016 Feb;149(2):315-352. doi: 10.1016/j.chest.2015.11.026. Epub 2016 Jan 7. Erratum in: Chest. 2016 Oct;150(4):988.

Study Aims

□ To understand the clinical characteristics of patients with SSPE: ■ Clinical presentation ■ Co-morbidities (VTE Risk factors)

□ To study the current management of SSPE patients in a tertiary care academic center.

□ To study the natural history of SSPE at 1 year follow up.

METHODS

□ Retrospective study from 1/1/2013 to 6/30/2017 at our center (The University of Kansas Medical Center).

□ We manually reviewed the medical records for detailed information on demographics, risk factors, clinical features, tests performed, medications used and follow up.

□ Inclusion and Exclusion criteria:

Inclusion Criteria Exclusion criteriaAge >18 years Concomitant Segmental or larger PE

SSPE diagnosed using CTA chest Prior history of PE

PE diagnosed using V/Q scan

RESULTS□ 213 patients with isolated SSPE constituted the study group. (mean age : 57.9 years,

51.2% were female and 76.1% were Caucasians). □ 70.5 % of patients were followed for >1 year.

Risk Factors for VTE □ Majority patients had risk factors for VTE.

□ 37 out of 213 (17.4%) patients had SSPE despite having no known risk factors for development of VTE.

Comorbidities/Risk Factors Number of Patients PercentageMalignancy 111 52.1Recent Surgery within 1 month 55 25.8Current Tobacco smoker 44 20.7Immobility for > 3 days 38 18.1

Clinical Presentation and Imaging

❑ Most patients were symptomatic.

❑ SSPE was an incidental finding in 18.3% of patients. ❑ Symptoms concerning for PE prompted CTA chest in 73.7% of patients. ❑ 47.4% patients underwent lower extremity ultrasound. 7.04% patients (out of 213

patients) had concomitant lower extremity DVT.

18.3%

Clinical features Frequency PercentageDyspnea 118 55.7Chest pain 76 35.7Lower extremity Swelling 23 10.9Calf pain 9 4.3

Hemoptysis 3 1.4

Treatment characteristics□ Majority of patients were treated regardless of symptoms, risk factors and place of

diagnosis (inpatient, outpatient or ER).

□ Most common initial and long term anticoagulant use was Enoxaparin (61.2%) and warfarin (37.5%) respectively.

□ 39.3% of our patients were treated for ≥ 1 year.

Total Patients Patients with no risk factors Asymptomatic patients Outpatient patients

91.9

82.981.5

76.8

87.289.2

84.285.2

Risk factors Symptoms Place of diagnosis

Follow up and Outcomes

□ SSPE related mortality was low. □ No statistically significant difference was observed in PE mortality (2.8% vs 0%) □ PE recurrence at one year (1.1% vs 9.7%, NS) among anticoagulated and non-

anticoagulated patients, respectively. □ 10.9% of anticoagulated patients had major bleeding on follow up.

Sub-analysis of SSPE patients who were not anticoagulated

Figure . Showing 31 patients in whom no anticoagulation was used

Reason for Not using Anticoagulation (AC)

Patient transitioned to hospice/comfort measures

Patient asymptomatic

Contraindication to AC

SSPE lesions on CTA were thought to be scar/clinically insignificant 18

9

3

1

LIMITATIONS

□ Single Center Study □ Tertiary Care Academic center, May not reflect diagnosis of SSPE in

community setting ■ Chest radiologists read CTA ■ Patient population is different

□ Small Sample size

Strengths

□ Largest study to date □ Detailed clinical information from careful review of medical

records □ 1 year Follow up information on treatment and clinical outcomes

CONCLUSIONS

□ In a tertiary care setting ■ A majority of patients with SSPE have symptoms consistent with PE ■ A majority of patients have traditional risk factors for VTE ■ In current clinical practice a majority of patients are anticoagulated ■ PE related mortality in both anticoagulated and non anticoagulated patients was low ■ Though not statistically significant, higher recurrence rate in non-anticoagulated patients

(small numbers) □ Unable to definitively answer the question of safety of not anticoagulating □ There is still a need for a RCT

RESEARCH TEAM

Kamal Gupta, MD : Mentor Nilay Patel, MBBS

Matthew Lippmann, DO Ethan Hacker, MD

Alexander Robinson, DO Nicholas Isom, MD Tyler Buechler, DO

Michael Pierpoline, DO Christopher Janish, MD Lewis Satterwhite, MD

THANK YOU FOR YOUR ATTENTION