Dalen and Dexter1 rightly emphasized the importance and the difficulty of diagnosing pulmonary embolism. The importance rests with the facts that the condition is frequent in hospitalized patients and that it is potentially lethal, constituting one of the three most common causes of death at the authors' hospital.
The diagnosis is difficult because pulmonary embolism is a great masquerader. Thus, Dalen and Dexter named four different clinical syndromes: (1) pulmonary infarction, (2) acute cor pulmonale, (3) acute, unexplained dyspnea, and (4) aggravation of preexisting left ventricular failure. The diagnosis is assisted, of course, when a source for emboli is identified, such as evidence of phlebothrombosis in the deep veins of the calf (calf tenderness, positive Homans sign, slight cyanosis of the leg and prominence of superficial veins when the legs are dependent, an abnormal phlebogram).
In the table accompanying their essay, the authors listed the important emergency diagnostic tests
Hussey HH. Pulmonary Embolism. JAMA. 1973;226(11):1351. doi:10.1001/jama.1973.03230110043012