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VENOUS THROMBOEMBOLISM IN PREGNANCY

Pulmonary Embolism

ByEman mahmoudM.D of chest diseases

1

Pulmonary Embolism

Embolism : Impaction of a thrombus or foreign matter in the pulmonary vascular bed.

Epidemiology2nd most common cause of unexpected death in most age groups.

present in 60-80% of patients with DVT, more than 50 % them are asymptomatic.

Account for 15 % of all postoperative deaths

it is estimated that in the USA .100 000 peopledie each year of pulmonary embolism.

.

Thrombotic

Non-thrombotic : Fat, Air, Tumour , Amniotic fluid.

EMBOLUS

4

RISK FACTORSBed restPost-operativeAfter severe blood loss and traumaCOPDCHFVaricose veinsAdvancing age

ObesityPost-partumMalignancyTravel of 4 hours or more Smoking1ry polycythemiaOral contraceptives

THROMBOPHILIA Acquired thrombophiliaInherited thrombophilias

Hereditary factors

Antithrombin III deficiencyProtein C deficiencyProtein S deficiencyFactor V Leiden (most common genetic risk factor for thrombophilia)Plasminogen abnormalityPlasminogen activator abnormalityFibrinogen abnormalityResistance to activated protein C

Acquired thrombophilia

This is mostly associated with the antiphospholipid syndrome (APS). APS is the combination of (LAC) with or without, (ACA), with a history of recurrent miscarriage and or thrombosis.

Pathophysiology

Clinical FeaturesSize of the embolus and blood vessel occluded.

State of the lung.

Associated disease(s).

PE, Clinical Features

dyspnea (7585%)

Pleuritic chest pain (5787%)

cough (4053% )

Hemoptysis

Syncope.

Massive Pulmonary Embolism MPEcollapse/hypotension

unexplained hypoxia

engorged neck veins

Acut right heart failure

Physical Signs

NormalTachypnea (respiratory rate >16/min) - 96%Rales - 58%Accentuated second heart sound - 53%Tachycardia (heart rate >100/min) - 44%Fever (temperature >37.8C) - 43%Diaphoresis - 36%S3 or S4 gallop - 34%Clinical signs and symptoms suggesting thrombophlebitis - 32%Lower extremity edema - 24%Cardiac murmur - 23%Cyanosis - 19%

14

Clinical Probability of PE

D-Dimer

Degradation product produced by plasmin-mediated proteases of cross-linked fibrin.

Blood D-dimer assay should only be considered following assessment of clinical probability.

D-dimer assay should not be performed in those with high clinical probability of PE.

D-dimer

.Highly sensitive assays, such rapid ELISA assays, have high false positive rates but safely rule out VTE in outpatients presenting with a low clinical probability of PE. A negative D-dimer test reliably excludes PE in patients with low clinical probability; such patients do not require imaging for VTE.

Ischemia-Modified Albumin levels

A potential alternative to D-dimer testing is assessment of the ischemia-modified albumin (IMA) level.

93% sensitive and 75% specific for pulmonary embolism

The positive predictive value of IMA, in particular, is better than D-dimer. However, it should not be used alone.

Chest x-ray 14% Normal 68% Atelectasis 48% Pleural Effusion 35% Pleural based opacity 24% Elevated diaphragm 15% Prominent central pulmonary artery 7% Westermarks sign 7% Cardiomegaly 5% Pulmonary edema

Elevated L H.Diaph

20

Decreased vascularity (Westermark sign)

(Hampton hump) The classic radiographic findings of pulmonary infarction

a wedge-shaped, pleura-based triangular opacity with an apex pointing toward the hilus

22

Atelectic band

cardiac troponins

Recently, cardiac troponins I and T have been shown to be associated with early mortality and a complicated hospital course in patients with PE.

The assessment of cardiac plasma troponin levels revealed ventricular injury, especially in patients with massive PE who had hypotensionor shock.

B Natriuretic Peptide (BNP)

BNP is a neurohormone secreted from the cardiac ventricles in response to dilatation or an increase of pressure.

BNP levels may increase with right ventricle dysfunction when the patients is in bed and decrease with treatment.

Serum brain natriuretic peptide levels of > 90 pg/mL have a sensitivity of 85% and a specificity of 75% for predicting adverse clinical outcomes

Arterial blood gases

Blood gases may increase the suspicion and contribute to the clinical assessment, but they are insufficient to permit proof or exclusion of PE.

ECG

In minor pulmonary embolism, the only finding is sinus tachycardia.

In massive pulmonary embolism, evidence of right heart strain may be seen (rightward shift of the QRS axis, transient RBBB, T-wave inversion, SIQIIITIII pattern, P- pulmonale), but these signs are non-specific.

The main value of ECG is exclusion other diagnoses, such as MI or pericarditis.

S1 Q3 T3 Pattern

Echocardiography

RV dilatation RV size does not change from diastole to systole = hypokinesis D-shaped LV 40% of pts have RV abnormalities seen by ECHO

Echocardiography

Transthoracic echocardiography rarely enables direct visualisation of the pulmonary embolus but may reveal thrombus floating in the right atrium or ventricle.

Transoesophageal echocardiography, it is possible to visualise massive emboli in the central pulmonary arteries.

Lower extremity venous ultrasonography

Advantages Portability May avoid further diagnostic imaging if positive

Limitations Low sensitivity and risk of false positives No consistent protocol for technique Operator dependant

Venous UltrasonographyRecommendations of Use First-line if radiographic imaging contraindicated or not readily available

Not likely required in patient with negative CT-PA.

Helpful to rule out DVT in patient with non-diagnostic V/Q scan.

Lung scintigraphy

The lung scan is an indirect method of diagnosis since it does not detect the embolus itself but only its consequence, the perfusion abnormality.

Used when CT scanning is not available or if the patient has a contraindication to CT scanning or intravenous contrast material.

The Lung Scan Perfusion Perfusion

IV injection of human serum albumin labelled w/ technetium-99m Particles are same size as pulmonary capillaries and become trapped Lung peripheral to a clot is not perfused and will show defect

Ventilation: Inhalation of xenon-133 radioactive gas Degree of ventilation of all lung areas can be assesed Pneumonia, emphysema, tumors can cause defects Pulmonary embolism does not cause ventilation defect

Patients w/ a perfusion defect w/out a ventilation defect is suggestive of a pulmonary embolus.

Presence of several large focal perfusion defects not matched by ventilation defects indicates a high probability of PE !!!!!

Normal scan basically excludes PE and indicates for other explanations for the pts condition.

High probability start Rx.

Low probability withhold Rx can do CT / angiogram. Intermediate probability can do CT / angio VQ Scan results

V/Q Scan

Advantages Excellent negative predictive value (97%) Can be used in patients with contraindication to contrast medium Limitations 30-50% of patients have non-diagnostic scan necessitating further investigation

CTPACTPA studies using the multislice technique showed a high sensitivity (96 to 100%) and specificity (97 to 98%),

CTPA is now the recommended initial lung imaging modality for non-massive PE. Patients with a good quality negative CTPA do not require further invest. or ttt for PE. BTS (2003)

Multidetector helical CT pulmonary angiography

Diagnosis of alternative disease entities

Coverage of entire chest with high spatial resolution in one breath hold Availability

Improved depiction of small peripheral emboli Advantages

Multidetector helical CT pulmonary angiography Limitations

Reader expertise required Expense Requires precise timing of contrast bolus Radiation exposure Not portable Contraindications to contrast Renal insufficiency the radiation dose from 3 to 5 mSv, with an estimated cancer risk of 150 excess cancer deaths per million

Multidetector-CT Findings

Partial or complete filling defects in lumen of pulmonary arteries Most reliable sign is filling defect forming acute angle with vessel wall with defect outlined by contrast material polo mint sign Tram-track sign Parallel lines of contrast surrounding thrombus in vessel that travels in transverse plane Rim sign Contrast surrounding thrombus in vessel that travels orthogonal to transverse plane a right-to-left ventricular dimensional ratio of 0.9 or more at MDCTA, had 92% sensitivity for right ventricular dysfunction

railway track sign on longitudinal images of the vessel

Arterial occlusion with failure to enhance the entire lumen due to a large filling defect

A peripheral intraluminal filling defect that forms acute angles with the arterial wall

A partial filling defect surrounded by contrast material, producing the polo mint sign on images acquired perpendicular to the long axis of a vessel

a peripheral, crescent-shaped intraluminal defect that forms obtuse angles with the vessel wall

Pulmonary Angiography

Was traditionally regarded as the reference test for PE. Due to the invasive character, including right heart catheterization and injection of contrast material.

The current availability of noninvasive diagnostic