Very common disease—usually missedVery common disease—usually missed
Commonly considered clinical diagnosis—usually wrongCommonly considered clinical diagnosis—usually wrong
In other words…In other words…
In most patients with PE, we don’t think of thediagnosis and…In most patients with PE, we don’t think of thediagnosis and…
In most patients in whom the diagnosis ispursued, it is not present.In most patients in whom the diagnosis ispursued, it is not present.
Pulmonary EmbolismPulmonary Embolism
Large numbers of patients die of PELarge numbers of patients die of PE
3rd most common cause of death3rd most common cause of death
650,000 deaths per year650,000 deaths per year
70% of PE found at autopsy was not suspected pre-mortem.70% of PE found at autopsy was not suspected pre-mortem.
1/3 who survive initial event will die of PE in thefuture. Mortality much less in treated patients.1/3 who survive initial event will die of PE in thefuture. Mortality much less in treated patients.
Many hospitalized patients have unsuspected DVT.Many hospitalized patients have unsuspected DVT.
You must think of the diagnosis in order to make it.You must think of the diagnosis in order to make it.
Problems with clinical evaluation Problems with clinical evaluation
Symptoms and signs are very nonspecificSymptoms and signs are very nonspecific
Hypoxia not a reliable findingHypoxia not a reliable finding
Degree of hypoxia not proportional to extent of PEDegree of hypoxia not proportional to extent of PE
Elevated WBC commonElevated WBC common
Classic ECG findings in only 20%Classic ECG findings in only 20%
Dozens of differential dx’sDozens of differential dx’s
Radiologic EvaluationRadiologic Evaluation
Most work ups for DVT/PE are negativeMost work ups for DVT/PE are negative
At best, about 1/3 of PE workups will be positive.At best, about 1/3 of PE workups will be positive.
With easy availability of MDCT in ERs, manyhospitals have positive rate of <20%.With easy availability of MDCT in ERs, manyhospitals have positive rate of <20%.
Radiologic EvaluationRadiologic Evaluation
“Gestalt” evaluation of likelihood of PE is good, butnot adequate, even with experienced MDs.“Gestalt” evaluation of likelihood of PE is good, butnot adequate, even with experienced MDs.
Use pretest probability systems, especially ifinexperienced residents are making workup decisions.Use pretest probability systems, especially ifinexperienced residents are making workup decisions.
Geneva, Wells criteriaGeneva, Wells criteria
Have a standardized protocol for evaluating patientswith possible PE.Have a standardized protocol for evaluating patientswith possible PE.
Not available 24/7everywhere.Not available 24/7everywhere.
Intermediate prob scannot much help.Intermediate prob scannot much help.
Low prob not much helpin patient with highsuspicion.Low prob not much helpin patient with highsuspicion.
CT AngiographyCT Angiography
Advantages:Advantages:
Multislice technologywidely availableMultislice technologywidely available
RapidRapid
AccurateAccurate
Direct imaging of vesselsDirect imaging of vessels
Can add venography withsame injection to evaluatethe legs and central veinsCan add venography withsame injection to evaluatethe legs and central veins
Critically ill patientsrequire special ventilator,monitoring equipmentCritically ill patientsrequire special ventilator,monitoring equipment
PE: Radiologic workupPE: Radiologic workup
Einstein algorithmEinstein algorithm
Patient with suspected
PE / DVT
Chest x-ray normal?
Bun/Creat abnormal?
Contrast Allergy?
Can’t hold breath?
DVT Sx?
inter
high
normal
No
further eval
for PE
low
CT
PAgram
Venous
Doppler
US
yes
no
V/Q
scan
yes toany
+
Treat
+
+
Venous
Doppler
US
_
_
no
_
V/Q scanV/Q scan
PIOPED study established standardized criteriafor assigning likelihood of PEPIOPED study established standardized criteriafor assigning likelihood of PE
True likelihood depends on pretest assessmentof likelihood of PETrue likelihood depends on pretest assessmentof likelihood of PE
High prob V/Q + low risk pt = 50% chance of PEHigh prob V/Q + low risk pt = 50% chance of PE
Low prob V/Q + high risk pt = 16% chance of PELow prob V/Q + high risk pt = 16% chance of PE
At AEMC, V/Q performed as first test if CXRnormal and no COPDAt AEMC, V/Q performed as first test if CXRnormal and no COPD
Intermediate probability scan in only 11%.Intermediate probability scan in only 11%.
V/Q scanV/Q scan
Perfusion scan: microembolization ofpulmonary vascular bed with labeled aggregatesof albuminPerfusion scan: microembolization ofpulmonary vascular bed with labeled aggregatesof albumin
Ventilation scan: may be performed withTechnicium labeled DTPA aerosol or Xenon gasVentilation scan: may be performed withTechnicium labeled DTPA aerosol or Xenon gas
Fetal dose similar to CTPAgram in pregnantpatientsFetal dose similar to CTPAgram in pregnantpatients
Normal V/Q scanNormal V/Q scan
ventilation
perfusion
High probability V/Q scanHigh probability V/Q scan
CT PAgram - TechniqueCT PAgram - Technique
Best on modern multidetector CTBest on modern multidetector CT
4, 8 or 16 channels4, 8 or 16 channels
Scan at thinnest slice width possible for breath holdScan at thinnest slice width possible for breath hold
1mm best-good evaluation of most subsegmental vessels1mm best-good evaluation of most subsegmental vessels
2.5 - 3 mm satisfactory for segmental vessels2.5 - 3 mm satisfactory for segmental vessels
High injection rate of contrast for maximum vesselenhancementHigh injection rate of contrast for maximum vesselenhancement
3-4 cc/sec3-4 cc/sec
Breath hold 8 sec for 16 channel scanner, 18 sec for 4channelsBreath hold 8 sec for 16 channel scanner, 18 sec for 4channels
Window and levels settings customized to scanWindow and levels settings customized to scan
CT PAgramCT PAgram
How good is good enough?How good is good enough?
Respiratory motion, lung disease, poor enhancementmay limit evaluation of small vesselsRespiratory motion, lung disease, poor enhancementmay limit evaluation of small vessels
If only segmental vessels are well seen, and scanis normal, can the workup stop?If only segmental vessels are well seen, and scanis normal, can the workup stop?
What is the risk of missing subsegmentalembolism?What is the risk of missing subsegmentalembolism?
Isolated subsegmental PE in 6-30% of cases.Isolated subsegmental PE in 6-30% of cases.
CT PAgramCT PAgram
Follow up studies have shown that there is lowrisk of embolism in 6-12 months followingnegative CT evaluation.Follow up studies have shown that there is lowrisk of embolism in 6-12 months followingnegative CT evaluation.
Important to include a study of the legs.Important to include a study of the legs.
Any subsegmental emboli missed are probablyclinically insignificant in most patients.Any subsegmental emboli missed are probablyclinically insignificant in most patients.
Remember that conventional angiography maynot be reliable for small vessels.Remember that conventional angiography maynot be reliable for small vessels.
Positive CTPA—Acute PEPositive CTPA—Acute PE
Acute PEAcute PE
Signs of massive embolismSigns of massive embolism
Clinical: loud P2, JVD—signs of RV failure, PAHTNClinical: loud P2, JVD—signs of RV failure, PAHTN
Dilated Main PA and right ventricleDilated Main PA and right ventricle
Reflux of contrast into IVCReflux of contrast into IVC
Straightening of IV septum or bowing towardsLV lumenStraightening of IV septum or bowing towardsLV lumen
Massive PE with right heart failureMassive PE with right heart failure
MPR may help define PEMPR may help define PE
Thick slab MIP
Pulmonary infarctionPulmonary infarction
Not commonNot common
Bronchial arteries usually supply sufficient flowBronchial arteries usually supply sufficient flow
Generally found with coexisting LV dysfunction,pulmonary venous HTNGenerally found with coexisting LV dysfunction,pulmonary venous HTN
Peripheral consolidation broadly based on pleuraPeripheral consolidation broadly based on pleura
“melting snowball” over several days to weeks“melting snowball” over several days to weeks
Chronic PEChronic PE
Cause of chronic pulmonary hypertension, dyspneaCause of chronic pulmonary hypertension, dyspnea
May not have known hx of acute PEMay not have known hx of acute PE
Most acute PE resolves without residuaMost acute PE resolves without residua
CT findings:CT findings:
Crescentic thrombus along wall of vessels, not in centerCrescentic thrombus along wall of vessels, not in center
Rapid tapering of vessels, small sizeRapid tapering of vessels, small size