embolus"- Harrison 18th/1972"Puisus paradoxus (a decrease in systolic BP during inspiration) is a norma! sign unless exaggerated to > 10 mm Hg.The most common cause of pulsus paradoxus is asthma and chronic obstructive pulmonary disease, though its presence may be a critical component to the diagnosis of pericardial tamponade"- CMDT06/314"Pericardial ejfusion: Pulsus paradoxus-a greater than 10 mm Hg decline in systolic pressure during inspiration due to further impairment of LV filling-is the classic finding, but it may also occur with obstructive lung disease"- CMDT06/409"Cardiac tamponade: The second characteristic hemodynamic finding is the paradoxical pulse, an abnormally large decline in systemic arterial pressure during inspiration (usually defined as a >10 mm Hg drop in systolic pressure). Other causes of pulsus paradoxus include constrictive pericarditis, pulmonary embolus, and pulmonary> disease with large variation in intrathoracic pressure. In severe tamponade the arterial pulse is impalpable during inspiration"- Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 8th ed.Table (Harrison): Features that Distinguish Cardiac Tamponade from Constrictive Pericarditis and Similar Clinical DisordersCharacteristicTamponadeConstrictive PericarditisRestrictive CardiomyopathyRVMIClinical Pulsus paradoxus Jugular veinsCommonUsually absentRareRareProminent y descentAbsentUsually presentRareRareProminent x descentPresentUsually presentPresentRareKussmaul's signAbsentPresentAbsentPresentThird heart soundAbsentAbsentRareMay be presentPericardial knock ElectrocardiogramAbsentOften presentAbsentAbsentLow ECG voltageMay be presentMay be presentMay be presentAbsentElectrical altemans EchocardiographyMay be presentAbsentAbsentAbsentThickened pericardiumAbsentPresentAbsentAbsentPericardial calcificationAbsentOften presentAbsentAbsentPericardial effusionPresentAbsentAbsentAbsentRV sizeUsually smallUsually normalUsually normalEnlargedMyocardial thicknessNormalNormalUsually increasedNormalRight atrial collapse and RVDCPresentAbsentAbsentAbsentIncreased early filling, |mitral flow velocityAbsentPresentPresentMay be presentExaggerated respiratory variation in flow velocity CT/MRIPresentPresentAbsentAbsentThickened/catcific pericardium Cardiac catheterizationAbsentPresentAbsentAbsentEqualization of diastolic pressuresUsually present Usually present Usually absent Absent or Cardiac biopsy helpful?NoNoSometimespresent NoAbbreviations: RV, right ventricle; RVM1, right ventricular myocardial infarction; RVDC, right ventricular diastolic collapse; ECG, electrocardiograph.">