Journal Reading Pulmonary embolism

1
Journal Reading Pulmonary embolism
91-09-14 ??? ???
2
A practical approach to the venothroboembolism

• --Clinical Medicine, Volume 1(4). July/August
  2001
• --Paul A Corris

3
Investigations-- Basic tests

• 1. Chest radiography
• Non-specific
• Exclude other diagnoses , ex. Heart failure,
  pneumonia, pneumothorax, tumor
• Common findings in PE focal infiltrate,
  segmental collapse, raised diaphragm and pleural
  effusion
• A wedge-shaped, pleural-based opacity rare

4
Investigations-- Basic tests

• 2. Eletrocardiography
• Usually non-specific changes in ST segment and/or
  T wave
• Massive emboli acute right heart strain is
  common
• Exclude other diagnoses, ex. MI, pericardial
  diasease

5
Investigations-- Basic tests

• 3. Arterial blood gas
• PE ventilation perfusion mismatch, reduced
  cardiac output with a low mixed venous oxygen
  saturation, and hyperventilation ? reduced PaCO2
  and normal or low PaCO2
• The degree of hypoxia roughly correlates with the
  extent of the embolism juged by V/Q scanning
• PaO2 and PaCO2 may be normal with small emboli
• In acute massive PE , cardiovascular collapse may
  cause a metabolic acidosis

6
Investigations Specific tests

• D dimers
• D-dimer is a degradation product released into
  the cross-linked fibrin undergoes endogenous
  fibrinolysis.
• In pt with suspected PE, a low plasma D-dimer
  concentration (lt500 ng/ml) measured by ELISA has
  a 95negative predictive power, but low D- dimer
  levels have been found in only about 25 of pt
  without PE.

7
Investigations Specific tests

• Ginsberg and colleagues evaluated the results of
  a bedside whole-blood agglutination D-dimer assay
  and impedance plethysmography in patients with
  suspected DVT. The overall negative predictive
  value for VTE was 98.5, while for the D-dimer
  tes alone it was 97.2.

8
Investigations Specific tests

• In an evaluation of 308 consecutive patients
  presenting to the emergency room with suspect PE
  using the same cut-off value for the quantitative
  D-dimer test, all but two of 198 patients with
  suspected PE and a D-dimer level below 500 ng/ml
  were free of PE, one had PE and one was lost to
  follow-up indicating an approximately 99
  negative predictive value.
• A normal plasma D-dimer, based on a reliable
  ELISA method, can thus be used to rule out VTE.

9
Investigations Specific tests

• 2. Lung imaging
• V/Q isotope scanning
• V/Q scanning should normally be performed within
  24 hours of clinical suspicion of PE because some
  scans revert to normal quickly, and half do so
  within a week.

10
V/Q isotope scanning

• In patients suspected of PE, a high probability
  V/Q scan report correctly indicated PE in 86-92
  of cases, while the accuracy in excluding PE is
  86 and 96 for low probability and normal scans.
  

11
V/Q isotope scanning

• In large studies using single-view133 Xe
  ventilation images and conventional reporting
  criteria, many patients fell into the
  indeterminate category which is of no value in
  discriminating between PE and non-PE.
• The use of newer ventilation scanning agents
  allowing multiple views should reduce the number
  of indeterminate scan reports.

12
V/Q isotope scanning

• Alternative imaging investigations
• previous pulmonary embolism, unless a
  follow-up scan has been performed
• left heart failure, shich can cause regional
  variations in pulmonary perfusion
• COPD with local variations in ventilation and
  in which the vascular bed may be constricted due
  to local hypoxia
• lung fibrosis with patchy unmatched defects in
  both ventilation and perfusion
• proximal lung cancer causing vascular occlusion,
  leading to a marked perfusion defect with
  preserved ventilation

13
Investigations Specific tests

• Spiral CT scan
• Early studies suggest good sensitivity and
  specificity of spiral CT for central or segmental
  thrombus
• The investigation of choice in patients with
  major embolism and those in the isolated
  dyspnea group.
• But not all the lung peripheral is included, and
  since emboli in subsegmental pulmonary arteries
  are not reliably visualised, it is less acurate
  than angiography in minor embolism

14
Spiral CT scan

• A recent report of PA confined to patients with
  nondiagnostic V/Q scans found that 30 had
  abnormalities confined to the subsegmental level
  where spiral CT scanning is less reliable.
• The initial confirmatory investigation of choice
  in patients with underlying chronic
  cardiorespiratory disease who present with
  clinical features suggesting VTE.

15
Investigations Specific tests

• Ultrasound techniques
• Compression ultrasound, which can be performed on
  basic real-time equipment, shows a high degree of
  accuracy in the femoropopliteal segment
• Color Doppler Imaging is now the investigation of
  choice in the detection of suspected DVT of the
  lower limb

16
Investigations Specific tests

• Ascending contrast venography
• Leg images
  -- leg vein imaging within 24 hrs is
  an alternative first-line investigation in those
  with clinical DVT or who have chronic
  cardiorespiratory disease, and following an
  indeterminate V/Q scan.

17
Investigations Other tests

• Echocardiography
• Echocardiography can establish the diagnosis in
  major central PE.
• A number of changes can be seen through cardiac
  echo
• --right ventricular dilatation and hypokinesis
• --pulmonary artery enlargement
• --tricuspid regurgitation
• --abnormal septal movement
• --lack of IVC collapse during inspiration

18
Echocardiography

• Can easily distinguished from conditions which
  may mimic PE (ex. MI, aortic dissection, cardiac
  temponade)
• Changes occur only when there has been
  significant obstruction to the pulmonary
  circulation.

19
Investigations Other tests

• Pulmonary angiography
• --PA should be considered in patients suspected
  of PE in whom investigations have failed to give
  a firm diagnosis
• --no absolute contraindications, particualr care
  sensitivity to cntrast, severe
  pul.hypertention, renal impairment, following AMI
• MRA

20
Sonography of Lung and Pleura in Pulmonary
embolism

• ---Chest, Volume 120(6). December 2001
• ---Reissig, Angelika MD Heyne, Jens-Peter MD
  Kroegel, Claus MD, PhD, FCCP

21
Introduction

• Only 1/3 of PEs that are confirmed by autopsy
  are diagnosed before death, reflecting the
  difficalty in establishing the diagnosis.
• Despite the widespread use of lung scanning and
  angiography, there has been no significant
  reduction in mortality from PEs throughout the
  past 40 yrs

22
Introduction

• Transthoracic echocardiography can easily and
  rapidly show
  1. the presence and the
  degree of right ventricular pressure overload
  2. direcly demonstrate
  thrombotic masses in t he main pulmonary
  arteries, although sensitivity and specificity
  are low.
• MRI offers both morphologic and functional
  information on lung perfusion and right heart
  function , but its image quality still needs
  improvement

23
Introduction

• In the past 10 yrs, spiral CT scannig has been
  introduced for the diagnosis of acute and chronic
  PEs, and it provides a noninvasive means of
  detecting acute PEs and organized thrombi, as
  well as perfusion abnormalities and other
  concomitant findings.
• Although sCT offers a high sensitivity and
  specificity for central or segmental PEs, more
  peripheral thromboembolic lesions confined to the
  subsegmental level may be overlooked.

24
Introduction

• CT imaging is costly and usually requires
  time-consuming organization prior to the
  investigation.

25
Introduction

• The detection of thromboembolic lesions of the
  lung by sonography was first described some 30
  years ago. Although the sonographic accuracy was
  gt 90, these early reports appear to have been
  overlooked for many years.

26
Goal

• To assess the diagnostic accuracy of
  transthoracic sonography (TS) in patients with
  suspected PEs and to compare the results with sCT
  scanning.

27
Materials and Methods

• February 1998 to March 2000
• Total 69 consecutive patients (27 women and 42
  men mean age, 62.8 years age range, 2488 y/o)
  with clinical signs of PE
• Only including TS as well as CT scans had been
  performed within 24 hrs
• During the study period, 138 patients with
  suspected PEs were investigated with sCT scanning
  but did not undergo TS

28
Materials and Methods

• All patients had a typical history of PE with the
  acute onset of complaints that included dyspnea,
  pleuritic chest pain, hemoptysis, vertigo or
  syncope, and/or tachypnea.
• Patients were examined by CXR (n69),
  echocardiography (n47), sCT scanning (n62), V/Q
  scanning (n23), ECG(n69), venous duplex
  sonography of the legs orcontrast venography
  (n61) and pulmonary angiography (n2). The
  diagnostic procedures also included the
  estimation of d-dimer levels

29
Materials and Methods

• TS--5-MHz and 3.5-MHz convex scanner
• TS was performed by one independent physician who
  was trained in chest sonography and who was
  unaware of the results of other diagnostic
  procedures.

30
Materials and Methods

• sCT Scanning
• 62 pts
• The CT image was read by an expert in chest
  radiology
• 7cases?this method cant be available

31
Materials and Methods

• Diagnostic Criteria
• --A diagnosis of PE was acccepted if PEs could be
  detected by sCT scanning
• --When parenchymal lesions were detcted on
  sonography only (n7) or if sCT scanning was not
  available (n7), the diagnosis of PE was
  acccepted when at least 3 of following 5
  investigations yielded positive results (1)
  typical history (2) echocardigraphy (3)venous
  duplex sonography or contrast venography of the
  legs (4) V/Q scanning (5) D-dimer level

32
Materials and Methods

• Diagnostic Criteria
• -- sCT scans were analyzed for the presence of
  intraluminal filling defects, defects within the
  central pulmonary arteries, dilatation of the
  main pulmonary arteries, and decreases in the
  size of the small branches of the lung as well as
  irregularities of the blood vessels.

33
Results

• Of the 69 patients in this study, 44 (63.8) had
  experienced PEs. Among the 44 patients, 35
  (80.9) showed sonographic changes involving the
  lung parenchyma.
• The parenchyma lesions were assessed according to
  their shape, number, size, demarcation, movement
  during respiration, and the detection of a single
  central echo.

34
Results
35
Results

• 9 paitents (25.7 ) --gt only one parenchymal
  lesion
• 26 paitents (74.3) suffered from multiple
  lesions.

36
Results

• Total 91 peripheral lesions were detected by TS
  (mean 2.6 lesions per patient range, 1 to 9
  lesions per patient)
• The most typical parenchymal findings were the
  following 1. wege-shaped or rounded hypoechoic
  lesions 2. hypoechoic lesions that extended to
  the pleural surface and in most cases, were
  well-demarcated and 3. occasionally a single
  echo that could be detected in the center of the
  lesions

37
Results
38
Results

• Parenchymal lesions detected by chest conography
  had an average size of 13.8 x 10.6 mm (size
  range, 3.7x3.9mm to 60x70 mm).
• 10 of the 91 lesions (11) were rounded, and 3
  lesions (3.3) had polygonal configurations. Most
  of the hypoechoic areas (78 areas 85.7 of
  lesions ) were wedge-shaped
• All lesions were hypoechoic and showed a convex
  outward bulging of the pleura.
• In 6 cases, a hyperechoic single echo was seen in
  the center of the lesions.
• All areas showed free movement during respiration

39
(No Transcript)
40
Results

• Characteristic signs of the pleural involvement
  included the following
• 1. a widening of the pleural space corresponding
  to the parenchymal lesion due to the local
  accumulation of fluid
• 2. a widening of the basal pleural space as a
  consequence of basal effusion with the paitent in
  the upright position
• 3. a convex outward bulging of the pleura 4. a
  thinned and fragmented hypoechoic visceral
  pleural line.

41
Results

• Localized effusion was seen in 8 patients
  (22.9), and another 7 patients (20.6) showed
  basal efusions. In 6 paitents (17.1), both
  localized and basal effusions could be detected.

42
Results

• 4 of these patients (44.4) showed localized
  effusions, and in one patient (11.1) a localized
  and a basal effusion were apparent. Another
  patient revealed sonographic features that were
  suggestive of pneumonia with a corresponding
  pleural effusion.

43
Results

• The sensitivity of the TS for PEs as 80, and the
  specificity was 92. The positive and negative
  predictive valued of TS for the detection of a PE
  were 95 and 72, respectively.
• The accuracy of TS for the detection of the PE
  was 84

44
Results

• Because of these results ,the sensitivity of
  heical sCT scanning for predicting PEs was 82,
  and the specificity was 100. The positive and
  negative predictive values were 100 and 77,
  respectively. The accuracy of helical sCT
  scanning for predicting PEs was 89

45
Discussion

• PEs need to be made in real time and that the
  time available for decision making is short.
• dignostic techniques such as V/Q scanning, CT
  scanning, or angiography may not be immediately
  at hand, and require time for arranging an
  examination and for the transport of the patient.
  

46
Discussion

• TS widely available, easily accessible, and
  can be performed at the bedside without delay.
• 80 sensitivity of TS for PE and a 92
  specificity of TS for PE, the results are in
  agreement with previously published values for
  the TS diagnosis of PE.

47
Discussion

• The sensitivty of Ts is comparable with that
  shown for CT scanning (sensitivity range, 75 to
  92)
• Although the number of patients in this study is
  low and future prospective studies are warranted,
  the data suggest that TS represents a reliable
  technique for diagnosing PEs, with a sensitivity
  that is compatible with that obtained by CT scan
  assessment.

48
Discussion

• The sudden complete embolic clog of a pulmonary
  artery results in a rapid breakdown of the
  surfactant system, which promotes not only
  atelectasis but also the transudation of fluid
  and the migration of cells into the affected lung
  tissue. ?depletion of air aloowing ultrasound
  waves to penetrate the affected arenchymal lung
  region.

49
Discussion

• During sonography, these thromboembolic lesions
  characteritically appear as well-demarcated,
  pleura-based, mostly triangular, but also
  circular, hypoehoic areas
• The data also suggest that in the majority of
  cases, PEs involves multiple sites withn the
  peripheral lung parenchyma. 75 patients with PEs
  showed 2 or more lesions (mean, 2.6 lesions
  perpatient) , the number of lesions is in good
  agreement with previous studies that reported an
  average of 2.7 lesions perpatient, as detected by
  pulmonary angiography, whether these lesions
  result from a single embolic event or are due to
  recurrent embolic episodes remains unknown.

50
Discussion

• While some authors consider minor PEs to be
  clinically irrelevant, othors have suggested that
  minor embolic events may represent a first
  warning signal preceding further thromboembolic
  events.
• In patients with preexisting cardiopulmonary
  disorders, even a minor PE might cause severe
  cardiorespiratory deterioration
• Since TS can distinguish parenchymal leions of lt
  1 cm, it represents an ideal method for the
  detection of small or very small peripheral
  thromboembolic events

51
Discussion

• A convex outward bulging of the pleura, and a
  thinned and fragmented hypoechoic visceral
  pleural line adjacent to the parenchymal lesion
  represented a regular feature.
• Thus, data obtained by TS provided a rather
  detailed picture of both the parenchymal and
  pleural alterations following thrmboembolic
  occlusion of pulmonary arteries, and they suggest
  an involvement of the pleura in approximately
  half of the patients.

52
Discussion

• Restriction of TS
• -- 1. embolism-associated lesions can be detected
  only when they extend to the lung periphry
• -- 2. a mere 66 of the peripheral lung area is
  accessible to sonographic examination, the
  remainder being covered by bony structures.
• -- 3. TS is subjective and operator-dependent,
  relying on the experience of the examiner.

53
Discussion

• Limitation of this study
• -- the use of sCT scanning as the comparative
  standard.
• --in order to compensate for the potential lack
  of sensetivity and specificity of CT scanning,
  the diagnosis of PE also was accepted when the
  results of at least three of the additional
  investigations ( medical history )were positive

54
Discussion

• A substantial number of PE events extent to the
  peripheral lung areas and can, thus, be detected
  by applying TS.
• TS is a simple, widely available, easily
  accessible, noninvasive, and cost-effective
  diagnostic technique providng a useful additional
  method in cases in which PE is suspected.