Non-Invasive Workup of Suspected PE in Pregnancy

cardiology members papercut lit review Dec 04, 2024

This study looked at the safety and efficiency of non-invasive diagnostic approaches in pregnant patients suspected of having a pulmonary embolism(PE).

The Study
Milo A.M et al. Diagnostic work-up for suspected acute pulmonary embolism during pregnancy: a systematic review and meta-analysis of individual patient data. J Thromb Haemost. 2023;21:606–615

Bottom Line

This was a systematic review, which was limited by only 2 studies being included. They looked at Wells Score and YEARS criteria and D-Dimers. The 2 studies used different scoring systems ie., Wells vs Revised Geneva and so are limited in the conclusion we can draw. What I think was important is that they found that in pregnant patients with no leg pain, 127 compressive ultrsounds had to be performed to avoid one CTPA. This is in my view is clinically significant to my practice, given that ultrasound of the legs is sometimes recommended as the first diagnostic step. The yield, is very low if the patient is asymptomatic.

What They Did

This was a systematic review followed by "an individual patient data meta-analysis of available studies in the setting of pregnancy." Databases of PubMed, Embase, Web of Science, Cochrane Library, and EMcare were searched for studies evaluating diagnostic strategies for suspected PE in pregnancy.

Inclusion Criteria:

Prospective studies with consecutive pregnant patients with suspected PE
Patients had to be prospectively managed according to a predefined diagnostic strategy.
The minimum duration of follow-up was one month.
The minimum number of patients to make a study eligible were 50.

Exclusion Criteria:

Patients receiving anticoagulants initiated 24 hours or more before inclusion.
Case Reports
Reviews

The study looked at the diagnostic performance of PE rule-out strategies in the pregnant patient. The diagnostic strategies included:

Wells Score
- For the fixed D-dimer threshold patients were classified as
  - PE unlikely (Wells score 0-4) or
  - PE likely (≥4⋅5).
- Where clinical pretest probability was used: a trichotomized Wells rule was used, which classifies patients as:
  - low (Wells score 0-4)
  - moderate (4⋅5-6⋅0), or
  - high (≥6⋅5) CPTP
YEARS algorithm
Wells Score and YEARS combined with D-dimer testing, and if indicated compression ultrasonography

Primary Outcomes

Sensitivity and specificity.

Safety
- This was the failure rate defined as:
  - proportion of patients with confirmed Venous Thromboembolism (VTE) to patients where PE excluded due to non-high pretest probability and a negative D-dimer, and where anticoagulation was withheld

VTE was confirmed by objective imaging or at autopsy, or if no other cause of death could be identified.

Secondary Outcomes

The diagnostic performance of compression ultrasonography.
- At baseline
- In suspected PE
The proportion of nondiagnostic test results and proportion of positive test results
Base- line prevalence of acute PE
The risk of PE-related death in the studied population.

What They Found

2 studies that fulfilled the predefined eligibility criteria (1, 2).

N = 893 patients.

Mean age of the patients was 31 years

42% of patients were in the 2nd trimester

42% of patients were in the 3rd trimester.

6.6% had a history of VTE

The 2 studies were:

The CT-PE pregnancy study (1) which used the revised Geneva score and a fixed D-dimer threshold of 500 μg/L
- Bilateral ultrasound was performed in patients with a high pretest probability or a positive D-dimer result regardless of the presence or absence of leg symptoms
- Baseline prevalence of PE was 7.1%
The Artemis study (2) applied the (pregnancy-adapted) YEARS algorithm.
- Only patients with symptoms of DVT were present during the initial assessment underwent leg ultraosund of the affected leg.
- Baseline prevalence of PE was 4.0%

Outcomes

Overall, sensitivity was high for all strategies:

Wells rule with fixed D-dimer threshold and the YEARS algorithm both had a sensitivity of 98%
The Wells rule with D-dimer threshold dependent on pre-test probability had a sensitivity of 90%

Specificity was:

44%: when using the Wells rule with D-dimer threshold dependent on pre-test probability
32%: when using the YEARS algorithm (32%),
12%: when using the Wells rule with the fixed D-dimer threshold.

Failure rates:

0.96% in non-high pretest probability and a normal D-dimer test was
1.4% in Wells rule with fixed D-dimer threshold
0.37% for the Wells rule with D-dimer threshold dependent on pre-test probability

Efficiency was:

Highest in the first trimester of pregnancy, when applying a D-dimer threshold dependent on pre-test probability.
Lowest in the third trimester of pregnancy, although it increased when applying an adapted D-dimer threshold.

The performance of compression ultrasonography is shown in the table below:

Chest Imaging was performed as shown in the table below. The rate of non-diagnostic CTPA tests in the Artemis trial was very low.

Discussion and My Take on This

This systematic review is limited by the fact that only 2 studies could be included. These studies used different algorithms for patient assement ie the CT-PE study used a revised Geneva Score for assessing pre-test probability and these patients were reclassified for the purpose of this study into an equivalent Wells Score.

For me, the most important thing I take away from this study was that compressive ultrasonography
In patients without leg symptoms, was not very good at picking up DVTs. 127 ultrasounds needed to be performed to avoid one CTPA. I will be probably not be performing this test if my pretest probability is anything but high.

References

Righini M, et al. Diagnosis of pulmonary embolism during pregnancy: a multicenter prospective management outcome study. Ann Intern Med. 2018;169:766–73.
Van Der Pol LM, et al. Pregnancy-adapted YEARS algorithm for diagnosis of suspected pulmonary embolism. N Engl J Med. 2019;380:1139–49.

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