Pulmonary Embolism: CT-ANGIOGRAPHY Dr Kisembo Harriet Nalongo Consultant Radiologist Mulago National Hospital Complex

Pulmonary Embolism: Pathogenesis Result of dislodged thrombus, most commonly in the venous system of the lower extremities (90%). Emboli lodge in pulmonary vessels too narrow to permit through-flow. Morbidity due to:Post-occlusion ischemia Cor pulmonale due to increased pulmonary artery presure

Urgency of Diagnosis Annual U.S. incidence of pulmonary embolism is 300,000 Annual U.S. mortality from the disease is 50,000 Untreated disease is associated with 30% mortality Treatment reduces mortality to 2-8% Carson, JL, Kelley, MA, Duff A, et al. “The clinical course of pulmonary embolism: One year follow-up of PIOPED patients.” NEJM 1992, 326:

Risk Factors for Pulmonary Embolism (PIOPED-1990) Immobilization Surgery within the last three months Stroke History of DVT/known Hypercoagulable disorder Malignancy The PIOPED Investigators. Value of the ventilation/perfusion scan in acute pulmonary embolism. Result of the prospective investigation of pulmonary embolism diagnosis (PIOPED). JAMA 1990, 263: 2753.

CTA: Anatomical Considerations Interpretation of CTA involves opacification of pulmonary arteries. A systematic evaluation of all arteries is necessary. Arteries accompany branches of the bronchial tree, and one vessel is associated with each segment of the lung (ten on right, eight on left).

PE clinical s/s Signs Symptom Dyspnea 73% Pleuritic chest pain 66%s Tachypnea 70% Rales 51% Tachycardia 30% S4 24% Fever 14% Clinical Manifestations of DVT 30% EKG changes 70% T wave inversions on EKG 49% Symptom Dyspnea 73% Pleuritic chest pain 66%s Cough 37% Hemoptysis 13% Stein, PD, Saltzman HA, Weg, JG. “Clinical Characteristics of patients with acute pulmonary embolism.” Am J Cardiol 1991, 68: 1723

Diagnostic imaging The choice of diagnostic tests depends on the: Clinical probability of PE, Condition of the patient, Availability of diagnostic tests, Risks of iodinated contrast material, Radiation exposure Cost.

What modalities are used to investigate possible PE? Venous ultrasound (evaluation for DVT) V/Q scan CTA Pulmonary arteriogram

What is the purpose of getting a plain CXR when PE is suspected? To exclude other diagnoses (e.g, pneumothorax, pneumonia, CHF, rib fracture) as the cause of dyspnea or hypoxia

CT ANGIOGRAPHY Indications for Pulmonary CT Angiogram Clinical, laboratory, or radiologic finding suggestive of PE. Cardiac or lung disease excludes nuclear V/Q scan. Unsatisfactory V/Q scan, or inconclusive. Immediate diagnosis of PE is needed. Chest x-ray is not sufficiently clear to perform V/Q scan. Pulmonary hypertension secondary to PE. Prior history of PE with current symptoms.

CT ANGIOGRAPHY Fast helical CT scanning of the pulmonary vasculature Accurately timed intravenous injection of contrast media Rapid data acquisition during accurately timed intravenous delivered contrast agent to the vessels. Modern 16, 64, 128, and 256 slice and faster scanners make nearly motion free images of the pulmonary vasculature and lung parenchyma. Axial acquired images can then be reconstructed using various techniques in coronal and sagittal planes if needed.

CT Angiography Procedure: Contrast-enhanced spiral CT to evaluate pulmonary vessels Iodinated contrast media is injected intravenously Helical CT allows for the evaluation of the entire chest in a single breath hold. For main, lobar, and segmental arteries: sensitivity of 90% (60%-100% range in various studies) and specificity of 90% (80%-100% range). For subsegmental arteries, sensitivity is reduced (sensitivity range of 53%-100% for all pulmonary emboli). Ryu, JH, Swensen, SJ, Olso, EJ, Pellikka, PA, “Diagnosis of Pulmonary Embolism With Use of Computed Tomographic Angiography.” Mayo Clinical Proceedings, 76(1): 59-65, 2001.

CTA Findings for Pulmonary Embolism Acute Embolism: Centrally located filling defect Vessel occlusion Vessel distension Chronic Embolism Eccentric filling defect, often contiguous with vessel wall (+/-) calcification Garg, K, “CT of Pulmonary Thromboembolic disease,” Radiologic Clinics of North America 2002 40(1): 111-122

CTA: Discussion Recent data has demonstrated low morbidity (<2.0%) in patients untreated after negative CTA. Role of subsegmental emboli in causing morbidity is still undefined. Multi-head CT scanners now allow for faster scanning and better demonstration of segmental and subsegmental pulmonary vessels. CTA offers a method of direct visualization of the pulmonary vessels and lung parenchyma using diagnostic x-ray images. Multidetector row helical CT scanning offers the most sensitive and accurate diagnosis of pulmonary embolus.

CTA: PE case 1: 61Y F: cough x 1/12, dyspnoea x 4 /7, tachypnoe 4/7 and fever x 1/12.

Bilateral PE disease 38Y Male: c/o Chest pain Bilateral PE disease 38Y Male: c/o Chest pain. Cardiac echo showed a right sided strain

Minimizing the Uncertainty Multiple algorithms have been established to confirm or rule out PE in patients whose diagnosis is uncertain based on V/Q scan and clinical presentation, thereby minimizing the need for diagnostic pulmonary angiography. D-dimer measurements: Measurements are highly sensitive but very non-specific. Noninvasive lower extremity ultrasoundUltrasound has a high sensitivity (89%-100%) and specificity (89%- 100%) for DVT Anticoagulation of patients positive for DVT would be therapeutic for an undiagnosed PE Worsley, DF, Alavi, A. “Radionuclide Imaging of Acute Pulmonary Embolism.” Radiologic Clinics of North America 2001, 39(5): 1035

Lower Extremity Non-Invasive Ultrasound: DVT Criteria Primary diagnostic criteria is non- compressible vein Secondary criteria: Echogenic thrombus in lumen Venous distension Lack of Doppler signal No response to Valsalva with backwards flow or augmentation with forward flow The diagnostic approach to acute venous thromboembolism. Clinical Practice guideline. Am J Respir Crit Care Med, 1999

Lower Extremity Non-Invasive Study: Deep Venous Thrombosis Popliteal vein NO DVT DVT

A HIGH INDEX OF SUSPICION AND CTA CAN SAVE A LIFE THANK YOU