Question
A 55-year-old woman with a past history of treated breast malignancy presents with sudden onset breathlessness. On examination, respiratory rate is 40/min and oxygen saturation is 85% on room air. A diagnosis of pulmonary embolism is suspected and she is started on oxygen and low molecular weight heparin. She is shifted to a high-dependency setting. Which of the following findings would most strongly justify giving thrombolytic therapy?
a) Large clot seen in leg veins
b) Low blood pressure (shock state)
c) Patient requests aggressive treatment
d) Persistent low oxygen despite non-invasive support
e) ECG evidence of right heart strain
Answer:
Low blood pressure (shock state)
Detailed Explanation
The key concept here is risk stratification of pulmonary embolism (PE).
PE is classified into:
- Massive (high-risk) → haemodynamic instability
- Submassive (intermediate-risk) → RV strain but stable BP
- Low-risk → stable, no RV strain
👉 Thrombolysis is indicated ONLY in massive PE, defined by:
- Hypotension (SBP < 90 mmHg) OR
- Drop in SBP ≥ 40 mmHg for > 15 minutes
This reflects circulatory collapse due to RV failure, which carries a high mortality.
Why hypotension is the strongest indication:
- It indicates right ventricular failure + cardiogenic shock
- Mortality risk is very high
- Immediate clot dissolution (thrombolysis) is lifesaving
Why other options are wrong:
- Extensive DVT:
Indicates clot source, not severity of PE - Hypoxaemia:
Common in PE due to V/Q mismatch
❌ Not an indication for thrombolysis - ECG RV strain:
Suggests submassive PE
❌ Not enough alone for thrombolysis - Patient choice:
Clinical indication must guide therapy, not preference
Core Concept:
👉 Massive PE = Hypotension = Thrombolysis
Cheat Sheet (Exam Gold 🔥)
PE Severity Classification:
| Type | Features | Treatment |
|---|---|---|
| Massive PE | Hypotension / shock | Thrombolysis |
| Submassive PE | RV strain, normal BP | Anticoagulation |
| Low-risk PE | Stable | Anticoagulation ± outpatient |
Absolute indication for thrombolysis:
- Hypotension (SBP < 90 mmHg)
Not indications:
- Hypoxia
- RV strain alone
- Large clot burden
- DVT presence
Flashcards
Q1: What is the main indication for thrombolysis in PE?
A: Haemodynamic instability (hypotension)
Explanation: Indicates massive PE with high mortality risk
Q2: Does RV strain alone indicate thrombolysis?
A: No
Explanation: It indicates submassive PE → anticoagulation
Q3: Why is hypoxia not an indication for thrombolysis?
A: It occurs in most PE cases and does not reflect severity of circulatory compromise
Q4: What is the first-line treatment for stable PE?
A: Anticoagulation (DOAC preferred)
MCQs (High-Yield & Challenging)
MCQ 1
A 60-year-old man presents with PE. BP is 85/60 mmHg, HR 120, oxygen saturation 90%. What is the next best step?
a) Start DOAC
b) Thrombolysis
c) Oxygen only
d) IVC filter
e) Observe
Answer: b) Thrombolysis
Explanation: Hypotension = massive PE → immediate thrombolysis required
MCQ 2
Which of the following is NOT an indication for thrombolysis in PE?
a) SBP 85 mmHg
b) Persistent hypotension
c) Drop in BP >40 mmHg
d) RV strain on echo
e) Cardiogenic shock
Answer: d) RV strain on echo
Explanation: RV strain = submassive PE → not enough alone
MCQ 3
A patient with PE has normal BP but severe hypoxia. Best management?
a) Thrombolysis
b) Anticoagulation
c) Embolectomy immediately
d) IVC filter
e) Steroids
Answer: b) Anticoagulation
Explanation: Hypoxia alone ≠ indication for thrombolysis
MCQ 4 (False type)
Which statement about PE thrombolysis is false?
a) Indicated in hypotension
b) Used in massive PE
c) Based on haemodynamic instability
d) Indicated in all hypoxic patients
e) Reduces mortality in shock
Answer: d) Indicated in all hypoxic patients
Explanation: Hypoxia alone is NOT an indication
MCQ 5
Which finding best predicts mortality in PE?
a) Oxygen saturation
b) Size of embolus
c) Blood pressure
d) Presence of DVT
e) ECG changes
Answer: c) Blood pressure
Explanation: Hypotension reflects RV failure → strongest mortality predictor
Summary for Quick Exam Revision
Pulmonary embolism management revolves around haemodynamic status, not just clot size or oxygen levels. The most critical distinction is between massive and non-massive PE. Massive PE is defined by hypotension or shock, reflecting acute right ventricular failure due to obstruction of pulmonary circulation. This group has the highest mortality and requires urgent thrombolysis. In contrast, patients with right ventricular strain but normal blood pressure (submassive PE) are treated with anticoagulation alone, as thrombolysis carries bleeding risk without clear survival benefit. Hypoxia, though common, does not indicate severity of circulatory compromise and should not guide thrombolysis decisions. Similarly, ECG changes and clot burden are supportive findings but not decisive. Therefore, blood pressure is the single most important parameter in determining need for thrombolysis, making hypotension the strongest indication.