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Pulmonary Embolism

From Tintinalli's Emergency Medicine, Chapter 60: Thromboembolism, by Jeff Kline:

The hallmark of PE is dyspnea unexplained by ausculatory findings, ECG changes, or obvious diagnosis on chest radiograph. Here, dyspnea refers to new-onset shortness of breath, either at rest or with minimal exertion. Second to dyspnea, chest pain with pleuritic features represents the second most common symptom of PE, although about one half of all patients diagnosed with PE in the ED have no complaint of chest pain. The definition of pleuritic chest pain is pain in the thorax between the clavicles and the costal margin that increases with cough or breathing, and is not purely substernal and not manifested from the skin or muscle. In theory, PE must cause pulmonary infarction to incite pleuritic inflammation, but most patients with PE and pleuritic chest pain have no radiographic evidence of pulmonary infarction. Overt pulmonary infarction can inflict severe focal pain, which the patient may localize by pointing with one finger on the rib cage or costal margin. PE that causes infarction in basilar lung segments can manifest as referred pain to either shoulder or can mimic biliary or ureteral colic. Proximal PE without infarction can also cause chest pain that increases with breathing, but the patient may not describe focal pain. Although about 20% of ED patients with PE complain of substernal chest pain, the presence of isolated substernal chest pain should not be considered a reason to evaluate a patient for PE. Large PE can cause epigastric pain, probably from right ventricular wall and pericardial stretching, as well as right ventricular ischemia. In addition to pain and dyspnea, approximately 5% to 8% of patients with PE in the ED present with near or full syncope, new-onset seizure (or convulsion-like activity), or new-onset confusion.1,22,23 PE probably causes altered mentation by impairing cardiac output and causing hypoxemia resulting in cerebral hypoxia. Because approximately 15% of persons have a patent foramen ovale, PE that increases right-sided pressures can lead to right-to-left transit of thrombotic material in the atria, with subsequent brain infarctions, and strokelike findings, which constitute the paradoxical embolism syndrome.

On physical examination, abnormal vital signs may suggest acute cardiopulmonary stress: tachycardia, tachypnea, a low pulse oximetry reading, and sometimes a mild increase in body temperature. Unfortunately, PE does not predictably alter any vital sign. For example, approximately one half of patients with proven PE have a heart rate of <100 beats/min at diagnosis. The mechanism of altered vital signs results is obstruction to blood flow and clot-derived autocoids, which together stimulate adrenergic efferents to the heart and cause ventilation–perfusion mismatch on the lungs. Thus, it would seem logical that a larger PE would cause greater alterations in vital signs. However, a plot of the percentage vascular obstruction (determined from imaging methodologies) versus the first measured heart rate or pulse oximetry reading (with the patient breathing room air) demonstrates no significant correlation (see plot example in Figure 60-1). Other relevant observations to make on physical examination include body temperature, condition of the lungs and heart, and condition of the extremities. Although approximately 10% of patients with PE have an oral temperature of >38°C (100.4°F), <2% of patients with PE have a temperature of >39.2°C (102.5°F). Most patients with PE have clear lungs on auscultation. Wheezes or bilateral rales decrease the probability of PE in favor of the alternative diagnoses of bronchospasm or pneumonia. One exception is pulmonary infarction, which tends to produce rales over the affected lung segment.24 On heart examination, expert auscultators may occasionally hear a right ventricular S3 or a split S2with a loud second sound. The presence of an indwelling catheter in the arm clearly increases the probability of axillary vein thrombosis, although it is less clear whether dialysis catheters or pacemaker wires also increase risk of symptomatic PE.

Clinical Prediction Rules

Pulmonary Embolism Rule-Out Criteria (PERC) (Kline et al. J Thromb Haem. 2004.; 2:1247-55):

  1.  age < 50 years
  2.  heart rate < 100 beats per minute
  3.  room air oxygen saturation ≥ 95%
  4.  no prior DVT or PE
  5.  no recent trauma or surgery (4 weeks)
  6.   no hemoptysis
  7.   no exogenous estrogen
  8.   no clinical signs suggestive of DVT

If all 8 present: 1% VTE @45d (Kline et al. J Thromb Haemost. 2008 May;6(5):772-80)

Well's Score for PE (Wells et al. Thromb Haemost. 2000;83:416-420):

Clinically suspected DVT:                                        3.0 points 
Alternative diagnosis is less likely than PE:               3.0 points 
HR > 100:                                                              1.5 points 
Immobilization/surgery in previous four weeks:           1.5 points 
History of DVT or PE:                                              1.5 points 
Hemoptysis:                                                           1.0 points 
Malignancy (treatment for within 6 months, palliative): 1.0 points

< 2: 2.9% PE
2-6: 15.8% PE        } Pooled data from outpatients
> 6: 40.8% PE             (Ceriani et al. J Thromb Haemost. 2010;8:957-70)

≤ 4 and neg d-dimer: 0.5% non-fatal VTE @ 3mo (van Belle et al. JAMA. 2006 Jan 11;295(2):172-9)

Revised Geneva Score (Ann Intern Med 2006;144:165) and
Simplified Revised Geneva Score (Arch Intern Med 2008;168:2131):

                     Revised                     Simplified   

Age >65:                                                                                 1                                1
DVT or PE in Past:                                                                   3                                1
Surgery with General or Leg Fracture (within 1 month):                2                                1
Active Cancer (or cured <1y):                                                    2                                1
Unilateral Lower Limb Pain:                                                       3                                1
Hemoptysis:                                                                            2                                1 
Heart Rate 75-94:                                                                     3                                1
>=95:                                                                                      5                                2
Pain on lower limb deep venous palpation AND unilateral edema:  4                                1

                0-3: 8% PE                  0-1: 7.7% PE

                4-10: 29% PE              2-4: 29.4% PE

                ≥11: 74% PE               5-7:64.3% PE




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