Vascular Medicine. Thomas Zeller

clinical probability of pulmonary embolism and deep venous thrombosis is estimated as described above.

      ECG

      

Right axis deviation

      

Sinus tachycardia: 50%

      

ST segment changes (particularly V1–V4): 40%

      

Right bundle-branch block: 15%

      

S_IQ_III type: 15%

      

P pulmonale: 5%

      Laboratory findings

      

Blood gas analysis (BGA): hypoxemia despite hyperventilation (Po₂ ↓, Pco₂ ↓)

      

d-dimers (microplate ELISA, VIDAS ELISA, Simpli-RED®):

      – Negative findings (< 500 μg/L) practically exclude pulmonary embolism; i.e., in 30% of patients with emergency admission, but fewer than 10% of inpatients, pulmonary embolism can be excluded using d-dimer assessment.

      – Caution: d-dimers are also raised in infection, inflammation, carcinoma, status post surgery, cardiac insufficiency and renal insufficiency, acute coronary syndrome, pregnancy, and sickle-cell crisis.

      – Troponin: evidence of hemodynamically significant pulmonary embolism, right ventricular enlargement, right cardiac ischemia

      

Coagulation tests:

      – Protein C

      – Protein S

      – Angiotensin III

      – APC resistance

      – Rheumatism serology, including anticardiolipin

      Chest x-ray

      Nonspecific changes include:

      

Atelectasis/infiltrate: 80%

      

Pleural effusion: 50%

      

Elevation of the diaphragm (unilateral): 30%

      

Vascular asthenia: 20%

      

Prominent pulmonary artery segment: 15%

      

Hilar vessel truncation (Westermark sign): 10%

      

Wedge-shaped solidification near the pleura (pulmonary infarction): 10%

      An unremarkable chest x-ray does not exclude pulmonary embolism.

      Diagnosis of deep venous thrombosis

      

B-image ultrasound with compression testing, color duplex ultrasonography (see section B 1.2, diagnosis of DVT)

      

Phlebography

      

      Table 2.2–1 Pathophysiology of pulmonary embolism.

Pulmonary artery obstruction → afterload increase for RV → walltension ↑, RV ischemia, RV decompensation, acute cor pulmonale →RV output ↓, RV volume ↑, septal deviation → LV preload ↓, cardiac output ↓ → RV coronary perfusion ↓ → right heart failure

Inhomogeneous perfusion → wasted ventilation → hypoxemia

Released mediators (thromboxane A2, serotonin, fibrinopeptides, leukotriene) → vasoconstrictio

      RV, right ventricle; LV, left ventricle.

      Table 2.2–2 Clinical probability of pulmonary embolism (adapted from Perrier).

High (80–100%)	Risk factor present, otherwise unexplained dyspnea, pleuritic pain, gas exchange disturbance or abnormalities on chest x-ray
Intermediate (20–79%)	Neither high nor low probability of pulmonary embolism
Low (0–19%)	No risk factors present, clinical symptoms and findings explicable by other causes

      Table 2.2–3 Severity of pulmonary embolism (adapted from Grosser).

      BP, blood pressure.

      Echocardiography (transthoracic echocardiography, transesophageal echocardiography)

      

Acute right ventricular load:

      – Dilated, hypokinetic RV

      – Raised RV/LV ratio

      – Deviation of the intraventricular septum in LV

      – Dilated proximal pulmonary arteries

      – Regurgitation via the tricuspid valve (jet: 2.5–2.8 m/s)

      – Dilated inferior vena cava without collapse on inspiration

      

Evidence of an embolus in transit

      

Exclusion of differential diagnoses:

      – Myocardial infarction

      – Valvular insufficiency

      – Hypovolemia

      – Endocarditis

      – Aortic dissection

      – Pericardial tamponade

      Ventilation–perfusion scintigraphy

      Only applicable with normal findings (15%) → exclusion of pulmonary embolism, high-probability finding (13%) → treatment. When ventilation–perfusion scintigraphy is not diagnostic—i.e., in approximately 70% of cases—further diagnostic procedures are necessary.

      Spiral CT

      

High sensitivity (94%) and specificity (94%) in embolism of the main trunk of the pulmonary artery and segmental arteries

      

Evidence of right ventricular dilation

      It is recommended that spiral CT should be used in combination with the clinical findings, laboratory