Pulmonary embolism Flashcards
PE depends on what?
- Extent of vasculature exclusion
- Rate at which obstruction accumulates
- Pre-existing cardiopulmonary status of the patient
Discuss the Pathophysiology of the PE
Read pg 10 of slides
- Decreased in the cross-sectional area of the pulmonary vasculature bed > which will increase vasculature resistance and RV afterload
- More than 50% of the pulmonary vasculature bed needs to be obstructed to increase pulmonary resistance
- Mediators released from platelets may induce vaso-bronchoconstriction
- Increase alveolar dead space > ventilation-perfusion mismatch and hypoxemia
- This will stimulate irritant receptors > hypoventilation
Discuss the 4 clinical forms of PE
- Acute Minor PE > short sudden onset > less then 50% vasculature obstruction (VO) > PST: Dyspnoea ,pleuritic chest pains ,haemoptysis > PAP & RAP normal
- Acute massive PE > Short sudden onset > >50% VO and thrombus volume is >30 ml > Right side heart strain ,haemodynamic instability and syncope > PAP Increased & RAP 12
- Subacute massive PE > Several weeks > > 50%VO > Dyspnoea with right heartstrain > PAP increases and RAP 8
- Chronic thromboembolic pulmonary hypertension > Months to years > >50% VO > Slowly progressing dyspnoea with exercise intolerance and right heart strain > PAP increased & RAP 6
History that might suggest PE
- Dyspnoea at rest or exertion usually onset
- Pleuritic chest pain
- calf pain or swelling
- coagh
- wheeze
- haemopytysis
- syncope
The examination that might suggest PE
- Tachypnoea
- Signs of DVT
- Tachycardia
- pulmonary crackles
- loud pulmonary component of second heart sound
- Elevated jugular venous pressure
Investigating PE: Arterial blood gas
- Doesn’t exclude minor PE but it is good evidence against major PE
- Decreased pO2 and Increased pCO2
- Widen alveolar-arterial O2 gradient
Investigating PE: Chest X-ray
- Usually abnormal (80%) but it is a nonspecific diagnosis therefore it may provide an alternative diagnosis
- Normal cardiac shadow with plump pulmonary artery segments
- Palla sign: Abrupt cut off of pulmonary artery
- Westermark sign: Oligeamia of the affected segment
- Hampton s hump: peripheral semicircular / wedge shape in contact with the pleural surface
- small pleural effusion, atelectasis, and raised hemidiaphragm
Investigating PE: ECG
ECG changes are common in PE but are nonspecific
- Sinus tachycardia
- S1Q3T3 pattern is uncommon
Investigating PE: Well’s Criteria for a clinical assessment for PE
- Symptoms of DVT (leg swelling with pain ,warmth ,palpation ) : 3
- Other diagnosis less likely than PE : 3
- HR > 100 bpm : 1,5
- Immobalization for more than 3 days or surgery in the past 4 weeks : 1,5
- Previous DVT / PE : 1,5
- Hemoptysis : 1
- malignancy 1
Simplified clinical assessment(mordified Wells criteria)
>4: PE likely
< 4: PE unlikely
Traditional clinicall probability assessment (Wells criteria)
- High :>6
- moderate : 2-6
- Low: <2
What to do when the patient is likely PE and haemodynamically stable after resus
- Start full anticoagulation and do definitive diagnostic imaging (CTPA) which will give us 2 types of results either PEor no PE
- When no PE stop full anticoagulation and investigate other causes for circulatory collapse
What to do when the patient is likely PE and hemodynamically unstable despite resus
- Bedside transthoracic or oesophagus echo which will give us 2 types of results
either Clot visualization in RV or proximal pulmonary arteries after considering empiric thrombolysis - Clot visualised no other cause for instability and RV dysfunction
What to expect when performing echocardiography in a likely PE situation
- Transthroracic: May see clot in RA
- Transoesophageal: Allows visualization of proximal pulmonary arteries
- Can assess for the presence of RV dysfunction
Using D dimer to determine PE
1.Determine if PE likely / PE unlikely
- IF PE unlikely :
* D-dimer assay
* if <500 ng/mL then exclude PE and offer no treatment
* if >500 ng/mL then CT pulmonary angiogram (CTPA) - If PE likely
* CTPA which will give us one of 3 different results
* Negative > PE excluded
* Possivtive > PE confirmed > Treatment
* Inconclusive > Additional testing eg V/Q which will ether confirm PE / not
Are elevated D-dimer levels enough to confirm PE
- NO, however, it should raise suspicions for VTED and prompt further testing even if well s modified criteria is PE unlikely
- Normal D dimer levels with likely PE is not enough to exclude PE but can exclude PE in patients with PE unlikely
Investigating PE : V/Q scan
Mismatch of inhaled and injected compounds on the lung scan suggest PE
