The subsegmental pulmonary embolus: Should all clots be treated equally?
Date First Published:
June 1, 2014
Last Updated:
June 1, 2014
Report by:
Fraser Magee, ST6 (St Thomas' Hospital)
Search checked by:
Fraser Magee, St Thomas' Hospital
Three-Part Question:
1. In [patients with isolated subsegmental pulmonary emboli]
2. is [oral anticoagulation therapy] necessary
3. [to reduce mortality and morbidity]?
Clinical Scenario:
A 36 year-old gentleman presented with pleuritic chest pain to the emergency department of St Vincent’s Hospital, Melbourne. He was low-risk for pulmonary embolism with a modified Well’s score of 0 but had a raised d-dimer of 0.7 mcg/ml. A CT pulmonary artery scan (CTPA) was performed, showing a subsegmental pulmonary embolus . He was subsequently admitted to hospital for anticoagulation and investigation of underlying risk factors.
The prospect of systemic anticoagulation for three months was unappealing for him. He was otherwise clinically well and was a young person with an active lifestyle. This raised the question of whether the use of oral anticoagulation was justified in this gentleman, or whether the potential harm would outweigh the benefits.
The prospect of systemic anticoagulation for three months was unappealing for him. He was otherwise clinically well and was a young person with an active lifestyle. This raised the question of whether the use of oral anticoagulation was justified in this gentleman, or whether the potential harm would outweigh the benefits.
Search Strategy:
The following search strategy was used:
Medline (54 papers identified): MM Pulmonary Embolism OR TI Pulmonary embol* AND subsegment OR sub segment* AND anticoag* OR MH anticoagulants OR TI therap* OR TI manag* OR TI treat*.
Embase (51 papers identified, nil additional): Pulmonary and embol* AND subsegment OR sub segment* AND anticoag OR anticoagulants OR therap* OR manag* OR treatment.
Cinahl (No additional papers identified): MM Pulmonary Embolism OR TI Pulmonary embol* AND subsegment OR sub segment* AND anticoag* OR MH anticoagulants OR TI therap* OR TI manag* OR TI treat*.
Cochrane database (No additional papers identified): Pulmonary embolus OR embolism AND subsegmental OR peripheral.
Reference lists of major papers identified from this search were scanned for any studies not identified by the database search.
Exclusion criteria:
-tStudies assessing patients with clots in larger vessels than the subsegmental arteries.
-tFollow-up of less than three months after diagnosis.
-tStudies performed prior to the MDCT-era (before 2002).
Medline (54 papers identified): MM Pulmonary Embolism OR TI Pulmonary embol* AND subsegment OR sub segment* AND anticoag* OR MH anticoagulants OR TI therap* OR TI manag* OR TI treat*.
Embase (51 papers identified, nil additional): Pulmonary and embol* AND subsegment OR sub segment* AND anticoag OR anticoagulants OR therap* OR manag* OR treatment.
Cinahl (No additional papers identified): MM Pulmonary Embolism OR TI Pulmonary embol* AND subsegment OR sub segment* AND anticoag* OR MH anticoagulants OR TI therap* OR TI manag* OR TI treat*.
Cochrane database (No additional papers identified): Pulmonary embolus OR embolism AND subsegmental OR peripheral.
Reference lists of major papers identified from this search were scanned for any studies not identified by the database search.
Exclusion criteria:
-tStudies assessing patients with clots in larger vessels than the subsegmental arteries.
-tFollow-up of less than three months after diagnosis.
-tStudies performed prior to the MDCT-era (before 2002).
Search Details:
Exclusion criteria:
-tStudies assessing patients with clots in larger vessels than the subsegmental arteries.
-tFollow-up of less than three months after diagnosis.
-tStudies performed prior to the MDCT-era (before 2002).
-tStudies assessing patients with clots in larger vessels than the subsegmental arteries.
-tFollow-up of less than three months after diagnosis.
-tStudies performed prior to the MDCT-era (before 2002).
Outcome:
Three studies were identified from the literature search that met the criteria.
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| Clinicians’ Re Eyer et al 2005 USA | Patients diagnosed with subsegmental pulmonary embolism on CTPA. | A retrospective single-centre study assessed the clinician’s response to 77 MDCTs that were reported positive for ISSPE. The researchers reviewed 1,435 scans and 77 (5%) were reported as showing a subsegmental pulmonary embolism. 130 scans were reported as inconclusive and these patients were also followed-up. 32 patients with ISSPE received no anticoagulation (34%). The decision on whether to anticoagulate was based on individual clinician judgement. No clinical probability scores or protocol were used. It was unclear how many untreated patients were actually misdiagnosed and in what proportion an active decision not to anticoagulant was made. 25 of the 32 patients were followed-up at 3-months. This was done by retrospective analysis of the hospital records. Two of the untreated patients returned with symptoms of recurrent pulmonary embolism but repeat CTPA was negative. None of the patients, treated or untreated with anticoagulants, had recurrence of venous thromboembolism at 3 months. | This study was limited by being performed in a single center. It was a retrospective review of case notes and so may have missed patients who presented to another hospital with pulmonary embolism or who died and were not accounted for. It was limited by small numbers and was designed to assess the response of clinicians to the radiographic diagnosis of ISSPE rather than the safety of withholding anticoagulation. A high proportion of scans were reported as inconclusive (9%). The experience of the radiologist reporting the scan was unclear from the methodology and the scans were not independently reviewed. It is possible that there were a number of false positive and false negative reports in the ISSPE and inconclusive groups. Only 78% of untreated patients had records of having been followed-up at three months and this may have resulted in selection bias. | ||
| Clinical Outcomes in patients with isolated subsegmental pulmonary emboli diagnosed by multidetector CT pulmonary angiography Donato et al 2010 USA | Patients diagnosed with subsegmental PE on CTPA. | This was a retrospective single-centre study that reviewed the clinical outcomes of 93 patients who had a positive radiology report for subsegmental PE on CTPA. Fifteen patients who had a co-existing deep vein thrombosis (DVT) were excluded. 10,453 CTPA radiology reports over a 74- month period were analysed, with 1,463 being positive for PE. Patients were followed up over a three-month period to assess outcome and bleeding risk. Twenty-two patients (23.6% of those with ISSPEs) were treated conservatively. 20 out of 22 of the untreated patients had a negative doppler ultrasound scan, excluding DVT. Follow-up was performed by review of clinical records and direct contact with the outpatient physician. The untreated group had no recurrent PE at the end of three months. All patients were accounted for and patients who could not be found had death records requested. All CT scans were reported by a board certified radiologist and the positive scans were then re-reviewed externally to confirm the diagnosis. The decision to anticoagulate depended on individual physicians and there was no protocol to guide this decision. It was unclear whether there was any clinically significant difference between the treatment and non-treatment groups. Eight adverse events due to haemorrhage were reported in the treatment group. Two deaths were reported but thought to be unrelated to thromboembolic disease. Recurrence of subsegmental emboli was reported in one patient who was actively treated. This was at 15 days and following IVC filter placement and warfarin commencement. This was the largest study on clinical outcomes in ISSPE. It involved the interpretation of data over six years and on over 10,000 CT scans. Very few patients were lost to follow-up. |
22 out of 93 patients with ISSPE treated conservatively (23.6%). Nil had recurrence of venous thromboembolism at three months. | Single-centre retrospective study. No protocol determining treatment. Limited by small numbers of untreated patients. The majority of patients with ISSPE were treated with anticoagulation. |
|
| Clinical characteristics of patients with peripheral pulmonary embolism. Cha et al 2010 South Korea | Patients with subsegmental pulmonary embolus diagnosed on CTPA. | These authors reviewed MDCT scans performed over five years at a tertiary centre in South Korea between 2003 and 2008. 334 patients who had scans reported as positive for PE were retrospectively analysed for underlying clinical characteristics, treatment and outcome. The total number of CTPA scans performed during the study period was not reported so it is unclear whether clinicians had a lower threshold for performing scans at this center, increasing the possibility of incidental false positive scans. These were reported externally by two experienced radiologists who were blinded to the underlying clinical information. PEs were divided into central (245; 73.4%), segmental (67; 20.1%) and subsegmental (22; 6.6%). Twenty-two patients were identified as having ISSPE and 63.6% of these patients had this diagnosed as an incidental finding. Fifteen patients with ISSPE received anticoagulation with seven being untreated. The majority of these patients were untreated because diagnosis was missed on initial MDCT. The median follow-up was for eight months and there were no reports of recurrent PE or PE-related death in the untreated patient group. This was in contrast to 2.9% and 4.5% of patients with central and segmental PEs having clot-related deaths |
No information was given as to how the patients were followed-up. If this was done simply by retrospective review of case records then the possibility of missed PE recurrence and death is possible. This study involved small numbers of patients with ISSPE and was retrospective in design, leading to possible selection bias. |
Author Commentary:
Current evidence base consists of retrospective studies including small numbers of patients. There is insufficient evidence to recommend a change from current practice.
Bottom Line:
Maintaining a practice of routine anticoagulation, unless there are contraindications or specific reasons not to, seems a prudent and reasonable strategy with the current evidence base.
References:
- Eyer et al. Clinicians’ Re
- Donato et al. Clinical Outcomes in patients with isolated subsegmental pulmonary emboli diagnosed by multidetector CT pulmonary angiography
- Cha et al. Clinical characteristics of patients with peripheral pulmonary embolism.