Pulmonary embolism

ID: 1426292-8

Date of admission:90-10-22

Name: 謝美莉 sex:female

age:30y/o

Chief complaint

Exertional dyspnea noted for 1 month

Present illness

This 30y/o woman was well before. Unfortunately, she suffered from exertional dyspnea one month ago. Exertional dyspnea occurred during her MC period. According to her statement, symptom/sign subsided after the finish of MC period. But it attacked again 1wk ago. In addition, syncope, dizziness, cold sweating, chest pain, epigastralgia, and nausea/vomiting was noted. She went to 小港 hospital for help. Treadmill test was arranged. Due to personal reason, she came to our ER for help.

At ER:

WBC:10820 Hgb:13.4 PLT:81k CK:66

CK-MB:3.7 TnT<0.01 GOT/GPT:36/35

Sugar:132 BUN/Cr:14/1.0 Na/K/Cl:139/4.3/112

Under the impression of (1). Extertional dyspnea. (2). Thrombocytopenia. She was arranged to get admission for further survey and management. After admission to 11C, the diagnosis of acute pulmonary embolism was made. At once, heparinization and anticoagulant drug was given. However, the poor clinical improvement was noted. The pulmonary angiography was performed. Because of (1). The persisted pulmonary embolism. (2). APS. She was transferred to the CCU for thrombolytic treatment.

Past History

1.DM ： (-)

2.H/T ： (-)

3.Alcohol: (-)

Smoking: (-)

4.Other systemic disease: myoischemic (+) was ever told

5.Drug allergy: denied

Physical examinationConsciousness: clear Head: Conjunctiva: not anemic

Sclera: icteric Neck: supple LAP: (-) JVE: (-) Chest: symmetric expansion

Heart sound: RHB, no murmur Breath sound: rale over left basal area

Abdomen: soft & flat Bowel sound: normoactive Tenderness: (+) over epigastralgia area,

Extremity:freely movable Lower legs: pitting edema

EKG

LeadⅠ: deep S

LeadⅢ: Q wave, reversed T wave(S1Q3) => R/O pulmonary embolism

V1-4: QS wave, reversed T wave => R/O old anterior septal ischemic change

APS

＊ Anti-phospholipid syndrome

(1). Lupus anti-coagulant(+)

(2). Anti-cardiolipin Ab(+)

(3). β2GP1 (+)

Impression

1.  Exertional dyspnea

suspect CHF, IHD,

pulmonary hypertension,

pulmonary embolism

2.  Thrombocytopenia

Image Finding Date: 10/25 Tc99m MAA pulmonary perfusion/Tc99m DTPA aerosal ventilation

scintigraphyFrom the both perfusion and ventilation images, the findings are shown as:(1). Relatively delayed pulmonary perfusion in the bilateral lung fields.(2). Multiple segmental perfusion defects in the bilateral lung fields, including the right low basal, middle segments and left basal segments, upper segment. (3). Borderline cardiomegaly.(4). No overt abnormality in the correlated lung fields on the chest CT. Imp: High probability of pulmonary embolism.

11/12 Tc99m MAA pulmonary perfusion/Tc99m DTPA aerosal

ventilation scintigraphy From the both perfusion and ventilation images, the

findings are shown as:(1). Significant improvement of pulmonary perfusion in the bilateral lung field, compared with previous survey(10/25)(2). But still persistent segmental V/Q mismatch in the right post, apical, superior segments and left post apical and inguinal portion.(3). Uneven perfusion in the bilateral lung field.(4). Cardiomegaly.

11/14 Imaging findings: Tc-99m RBCs subcutaneous radionuclide

venography(SC-RNV)1. Dynamic Study:

faint deep venous return in the calf and communicating into the collateral in the right leg; smooth deep venous return in the left leg.2. Static Study(after removing tourniquet in the bilateral ankles)

dominant collateral flow with faint deep venous return in the bilateral legs, and more reduced deep venous flow in the right.

Venous thrombosis＊    About 60-80% pulmonary emboli (PE) arise from

thrombi of the lower extremity veins, while 15% arise from the pelvic veins.

＊    In other series: more than 90% of pulmonary emboli originates from deep vein thrombosis(DVT).

＊ Early diagnosis and treatment of DVT can constitute a preventive measure against PE.

＊    DVT does not cause death but PE contribute to moartality.

Reasons for underdiagnosed of DVT

＊    The thrombi may be clinically silent or the clinical features of DVT are atypical.(The usual S/S to diagnose DVT: tachycardia, low grade fever, localized tenderness, pain, increased skin temperature, redness, swelling, oedema, and positive Homan’s sign- are not specific.)

＊    Contrast venography(CNV): the age-old “ gold standard “ since 1934, has a poor patient and physician acceptance.

＊    Radionuclide venography(RNV): There remains some familiarity and perhaps scepticism regarding the overall worthiness of RNV in the diagnosis of DVT.

99m Tc pertechnetate ＊   The decision to use 99mTcO4 permits the use of a much

larger dose. Theoretically, electrostatic attraction is better achieved

with plain pertechnetate of its much smaller molecular size.

※ Large volume＊    The large volume makes it easier to apportion

the radiopharmaceutical during the slow and simultaneous but continuous intravenous injections.

＊    The larger volume also permits a relatively wider coverage of the venous network because of a fuller filling of the overall deep venous system.

＊    In post-phlebitic syndrome or in patients with full-blown varicosities, it is almost mandatory that large volume is used.(Venous capacitance has greatly increased)

＊    The entire procedure consists of the ascending dynamic and static RNV, usually takes less than 12min to complete.

Tourniquet

＊    The whole premise of tourniquet application is to prevent or minimize the passage of the contrast material into the superficial veins and concurrently deflect a larger volume to the deep venous system, thereby improving image resolution.

＊    Its use in CNV may be necessary because the required volume of contrast material is far greater than that ordinarily used in RNV.

＊    Another reason for its use: To minimize or altogether obviate problems related to the layering and streamlining of contrast material.(which are not problems in RNV since the N/S readily mixs with circulating blood.)

＊    The tourniquets are unnecessary generally since 74% of RNV studies automatically outline the popliteal / femoral vein.( If given adequate time, most of the deep venous system can be outlined)

＊    Tiny fragile dorsal pedal veins are frequently the only routes available for the injection.

Modifications (1)

＊    If the popliteal / femoral vein failed to be outlined in the ipsilateral symptomatic limb, a tourniquet is tightly applied above the ankle joint during the second injection.

＊    The persistent non-visualization of the popliteal/ femoral veins, especially when accompanied by pain => indicate DVT even if no collaterals are seen.

(2)

＊    Anterior static images of the pelvis and both lower extremities are performed and, in the case of the limbs, an additional “frog-leg” position of each extremity is obtained.

＊    Static RNV permits to differentiate between acute versus chronic DVT.

＊   “ frog-leg” position unbundles the superficial from the deep varices when these are present.

Limitation ＊    RNV identifies the site of occlusion, but does

not identify the thrombus inself.

＊   It is unable to distinguish between extraluminal or intraluminal causes of obstruction except on some occasions.

＊    Distal to the popliteal veins => the results are variable and hence diagnosis of calf DVT is not reliable unless a distinct “hotspot or segment” is identified on static images.

Types of studies for diagnosis of DVT

＊    Consist of non-radionuclide and radionuclide studies.

＊    CNV and Doppler/US: The most widely used non-radionuclide procedures.

＊    Radionuclide procedures consist of both non-imaging (ex: 125I-labelled fibrinogen uptake test ) and imaging studies.

＊    Two general types of RNV:

(1). Ascending dymanic RNV: best mimics CNV, injection is through the pedal veins.

(2). Static RNV: in some types, injection is done antecubitally.

＊   In some types of RNV, both dynamic and static RNV are performed together.

＊   An array of radiopharmaceuticals which include:99mTc-MAA, 99mTc-HAM, 123I or 125I fibrinogen, radiolabelled streptokinase, urokinase, 99mTc plasmin, 99mTc RBC, large volume 99mTcO4 …

have been introduced to perform RNV.

＊    Each RNV has its own merits and limitations, its own proponents and detractors.

＊    An optimally performed RNV, if negative, does exclude the presence of DVT, so it is reasonable to advocate it as a screening procedure of DVT.

Non-radionuclide study CNV

＊    The ability to ascess the deep venous system for thrombi is CNV’s primary edge over other procedures.

＊   It fails to distinguish between recent and residual(old) thrombi.

＊    The procedure has 7.5-24% related morbidity.

＊    Poor patient acceptance.

＊    It cannot be performed in patients with a swollen lower extremities or in patients with a history of contrast reaction.

Doppler/US ＊    Doppler/US are usually performed together as

one study.

＊   Doppler: measure deep vein blood flow velocity.

＊   A high degree of diagnostic accuracy in patients with initial episodes of DVT.

＊   When deep veins are not easily compressible during the study, the specificity and sensitivity drop significantly when compared with CNV.

＊    Resolution in the pelvis and thigh is poor.

＊    It fails to distinguish between recent and chronic thrombi.

＊    Drawback: limited field of view.

Other types of RNV 99mTc-HAM or 99mTc-MAA

＊   Arguments: There is no recirculation of radiopharmaceutical and a lung perfusion scintigraphy can subsequently be performed without a separate injection being administered. => valid reasons

＊    A large percentage of patients who undergo RNV do not necessarily need concurrent lung perfusion study.

99mTc RBC radionuclide venography

＊    99mTc RBC venography has high sensitivity and specificity exceeding 90%.

＊   Drawback: Tagging efficiency is influenced negatively by a large range of commonly used medications, contrast agents and RBC Ab.

＊ The procedure requires strict symmetric position of limbs: a minimal variance which give rise to some limb rotation will interfere with the accuracy.

＊    The low-pressure venous system is susceptible to external compressions by pillows, elastic bandages or stockings => false positive results.

＊    The static images tend to underestimate the presence of an extensive network of collaterals => take away important clue in diagnosis of DVT.

＊    Inefficient labeling, cross-activity from the arterial system becomes a major sourse of interference.

＊    It does not differentiate between acute and chronic DVT.

Radiolabelled platelet and antiifibrin RNV

＊    It not only diagnose but also monitor directly the efficacy of therapy instituted.

＊    Since heparin may reduce the sensitivity of technique => therapy require discontinuation.(But some people deny it.)

＊    It is accurate in the calf and popliteal area, has low sensitivity In the thigh and pelvis.

Normal scintigraphic features

＊    The normal ascending dynamic RNV outlines the IVC and the common iliac, external iliac, femoral and popliteal veins. Peroneal vein, ant. or post. tibial vein or saphenous vein is also identified.

＊    Normal configuration: easily resembles a wishbone or an inverted “Y” with long arms.

＊    Iliac vein: may show slightly less intense activity.(esp.attenuate in pts with capacious abdominal girth or massive ascites).

＊    The left iliac vein is relatively longer and has a generally more horizontal and superiorly curved course than the right. This apparently explains its greater vulnerability to extrinsic compression by pelvic masses or lesions => results in the higher incidence of left-sided occlusion of deep venous system.

＊    Right common iliac artery: as it branches out of the abdominal aorta , compresses the left common iliac vein as it joins the contralateral vein to become the IVC.

＊    The static RNV also outlined all the major deep veins described above with relatively less intensity.

Abnormal scintigraphic features

Sites and sides of DVT＊    DVT occurs frequently at venous bifurcations

since the angulations at these junctions may create some slowing of venous flow.

＊ Three common sites: (1) iliofemoral, (2) femorosaphenous (3) external-internal iliac junctions.

＊   Sites where structures that normally compress veins are susceptible sites of thrombi formation.

＊   82% if cases of DVT involve one side of the deep venous system; 18% of cases are bilateral.(usually seen at the level of iliofemoral junctions.)

＊   DVT involves external/common iliac, femoral and popliteal veins either singly or in combination. Of the multiple contiguous veins involved, the most common(25.7%of the case) is the iliofemoral combination.

＊ When the iliac vein is occluded, 61% involved the left side.

Scintigraphic features Ascending dynamic RNV

＊   Non-visualization of a major vein(usually the common iliac, ext. iliac, femoral or popliteal.)

＊    Rule of a thumb: occlusions at the iliac levels are associated with rich collateral formations and at the popliteal level a paucity or absence of collaterals.

＊    The extent of the network of collaterals depends directly on the degree, size and age of the thrombus.

＊    The dynamic RNV often demonstrates more vividly than conventional CNV the presence of rich collaterals.

＊    In some case, non-visualized vein of the thrombosed vein is the sole sign of occlusion. It is frequently seen at two sites: popliteal vein level and femorosaphenous junction.

＊   Frequently, non-visualization is due to a more localized and distal thrombus.

＊    The ascending dynamic RNV indentifies the site of distal occlusion but does not necessarily indicates the degree or the proximal extent of the thrombus.

＊    Despite the presence of complete deep vein occlusion, there is an absence or a paucity of small networks of collaterals.

＊    A middle pelvic abscess which compresses the left iliac vein shows a rich network of collaterals.

＊   Late and asymmetrical arrival of activity on one side of the deep venous system as a sign of occlusion on that side => But other causes must be excluded.(ex: post-phlebitic syndrome or the presence of deep or superficial varicose veins…)

＊   Some static RNV depend solely on the presence of so-called “hotspots” along the course of deep venous system.

“ Hotspots”    (1). Indicate uptake by the newly formed

thrombi.

(2). Have been observed in large dysfunctional

vein valves, sites of soft-tissue infections,

post-phlebitic syndrome, varicose veins…

(3). Newly formed larger thrombus of the pelvis

have failed to demonstrate “hotspots” by

radiolabelled anti-fibrin.(attributed to the

inability of the anti-fibrin radical to adhere to

or penetrate the core if the large thrombi.)

(4). Using anti-fibrin or platelets are better than

using 99mTc-HAM or 99mTc-MAA

(5). Reliable sign of acute DVT: particularly when

they are segmental rather than focal, and there

is a “smudgy” backdrop along with network

collaterals.

RNV – ideal monitor for DVT

＊   CNV: due to morbidity => poor pts and physician acceptance

＊    Doppler/US and IPG: have their own inherent limitation.

＊    RNV: are optimally suited for repeat studies of already established DVT.

＊    If the anti-thrombin or enzyme therapy has successfully prevented additional thrombi formation, and the thrombus is lysed, the disappearance of collaterals and some recanalization are seen.

＊    Early recanalization occurs usually within 10-12days.

＊   The site of thrombosis is usually narrower and fainter in outline, and traces of residual collaterals in the appropriate site linger.

＊   If the thrombus is not lysed, the initial observed collaterals are fortified and appear more graphic, while the occluded vein remains non-visualized.