Pulmonary embolism The risk factors for pulmonary embolism are the risk factors for thrombi formation within the venous circulation.The most common site for DVT: Calf veinsMost common source of pulmonary emboli: proximal vein of lower extremity (femoropopliteal and iliac vein)Calf venous thrombosis is itself associated with a low risk for embolism but when the thrombosis progresses proximally to involve the larger veins then the risk factors become very highClinical featuresFactors for clinical assessment of pulmonary embolismSymptoms: dyspnoea (MC), chest pain, hemoptysis, coughSigns: tachypnoea (MC), fever, unilateral leg swelling, wheeze, pleural friction rubClinical signs and symptoms of DVTAn alternative diagnosis is less likely than pulmonary embolismHea rate > 100/minImmobilization or previous surgery in 4 weeksPrevious DVT/PEHemoptysisMalignancy (on treatment, treatment in past 6 months)ECG changesDiagnosisFeatures suggesting acute right hea strain on ECG occur relatively infrequently, these include :Acute right axis detionP pulmonaleRight bundle branch blockInveed T wavesST segment changeECG changes highly predictive (but found in <12% pts) S wave in lead IQ wave in lead IIIInveed T wave in lead III (S1Q3T3)S wave in lead I, II, and III (S1S2S3)D-dimer is an excellent screening test for the diagnosis of PE Best investigation when there is clinical suspicion of PE: Multidetector Contrast CTLung scanning is now a second line diagnostic test for PE.Pulmonary angiography is the gold standard for the diagnosis of PE ECG changesDiagnosisFeatures suggesting acute right hea strain on ECG occur relatively infrequently, these include :Acute right axis detionP pulmonaleRight bundle branch blockInveed T wavesST segment changeECG changes highly predictive (but found in <12% pts) S wave in lead IQ wave in lead IIIInveed T wave in lead III (S1Q3T3)S wave in lead I, II, and III (S1S2S3)D-dimer is an excellent screening test for the diagnosis of PE Best investigation when there is clinical suspicion of PE: Multidetector Contrast CTLung scanning is now a second line diagnostic test for PE.Pulmonary angiography is the gold standard for the diagnosis of PE (Refer: Harrison's Principle of Internal Medicine, 18thedition, pg no- 2174)