All of the following may be seen in patients of cardiac tamponade, except:
Kussmaul's sign
Pulsus paradoxus
Electrical alternans
Right ventricular diastolic collapse on echocardiogram
Kussmaul's sign is an increase rather than the normal decrease in CVP during inspiration, is most often caused by severe right-sided hea failure; it is a frequent finding in patients with constrictive pericarditis or right ventricular infarction. Kussmaul's sign is present in constrictive pericarditis and its is a clinical sign differentiating cardiac tamponade from constrictive pericarditis. Kussmaul's sign is a rare in cardiac tamponade. All other features mentioned above are associated with cardiac tamponade. So "Kussmaul's sign" is the single best answer of choice. Ref: Harrisons Principles of Internal Medicine, 16th Edition, Pages 1415-17.