Which of the following statements are true of pulmonary embolism?

B. In the majority of patients pulmonary emboli are ultimately lysed in situ without the administration of pharmacologic agents.

C. The preferred therapy for most patients is intravenous heparin

DISCUSSION: Although many patients develop pulmonary embolism postoperatively, the majority of such lesions reported in most series do not follow operation. These patients develop thromboembolism as a complication of an underlying condition such as congestive heart failure, cerebrovascular accident, malignancy, chronic infection, and a variety of other debilitating diseases. Generally, postoperative patients comprise approximately one third of those with pulmonary embolism. Serial pulmonary scans following pulmonary embolism generally show gradual clearing of the emboli with reestablishment of perfusion in the occluded vessels. Depending on the magnitude of the embolism, most patients show the clearing at the end of a month to 6 weeks. The presence of persistent congestive heart failure, chronic infection, and atelectasis retard thrombolysis. This dissolution of emboli is generally agreed to be caused by naturally circulating thrombolysins. In fewer than 1% of cases the emboli persist and often increase with the passage of time, with the development of chronic pulmonary embolism leading to severe respiratory insufficiency, chronic cor pulmonale, pulmonary hypertension, right ventricular failure, and death. The majority of patients with pulmonary embolism are managed by continuous intravenous heparin. Thrombolytic agents are generally reserved for the management of extensive thromboembolism in patients with a stable cardiovascular system. Thrombolytic agents are generally withheld from postoperative patients until at least the fifth postoperative day, or preferably later. Earlier administration of these agents is apt to produce bleeding at the operative site. While it may occasionally be indicated to proceed earlier, it is generally best to wait until the thrombi in the vessels divided at the time of the surgical procedure have become organized.