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Blood Clots That Can Kill

Medically Reviewed by

A narrative description of the problems of thrombophlebitis and pulmonary embolism based on two real life cases from the medical literature (names have been changed).

Case 1:

Suzan, a 28-year-old accountant, had been married for five years. She considered herself lucky because she was nearing an uncomplicated pregnancy after having previous multiple miscarriages. In the fall of 1983, Suzan gave birth to a baby boy. One week after returning home, she experienced pain and swelling of the left calf. Due to the persistence of symptoms, she went to the local hospital emergency department and was told that she had a pulled muscle. The physician on duty advised her to rest her leg for a few days and told her not to worry as these symptoms would rapidly subside. The next day, the leg felt better but, while having dinner, she suddenly felt short of breath and collapsed unconscious on the kitchen floor. She was brought to the hospital by ambulance where she was pronounced dead on arrival.

Case 2:

Dr F. was a 65-year-old, recently retired, family practitioner. He had suffered from left arthritic pain towards the end of his career and had decided to undergo hip replacement surgery. Since he was otherwise healthy, it seemed certain that the procedure would provide improvement for him to resume his normal activities and enjoy his retirement years. The surgery went very well, and Dr F. was discharged to a rehabilitation centre for one week. Three days later, while having physiotherapy, he experienced shortness of breath, chest pain and died.

What happened to Suzan and Dr F.? They were both healthy persons who died suddenly. An autopsy showed the same cause of death in both cases: massive pulmonary embolism.

What is pulmonary embolism?

Pulmonary embolism refers to the presence of blood clots in the blood vessels of the lungs. When sufficiently large, these clots may block the passage of blood from the lungs to the heart and cause a cardiac arrest.
Fortunately, the great majority of patients with pulmonary embolism do not experience sudden death and can seek medical treatment. The most common symptoms of pulmonary embolism are a sudden onset of shortness of breath and one-sided chest pain. Typically, the chest pain is worsened by deep inspiration.
Pulmonary emboli do not occur de novo from within the lung vessels but originate from the deep veins of the legs. The deep veins of the legs are rather large veins whose role it is to bring blood back toward the heart from the lower extremities. The formation of blood clots in the deep veins of the legs is termed thrombophlebitis or, so-called, deep vein thrombosis (DBT).

Why did Dr F. and Suzan have pulmonary embolism?

Deep vein thrombosis and pulmonary embolism occur predominantly in patients who have had
major surgery, trauma, cardiac disorders, cancer, or some women taking oral contraceptives. A number of rare, inherited blood disorders predispose to deep vein thrombosis. Frequently, there is a history of thrombophlebitis in other members of the family. By coincidence, we saw Suzan’s cousin in consultation at The Montreal General Hospital, eight years after Suzan’s death. She had developed deep vein thrombosis while taking oral contraceptives. We were able to demonstrate a rare, familial type of blood disorder termed protein C deficiency. This was undoubtedly the cause of thrombophlebitis in the cases of both Suzan and her cousin. In the case of Dr F., clearly, the pulmonary embolism was caused by the trauma of hip surgery.
Trauma and major surgery are major risk factors for pulmonary embolism because the two main mechanisms underlying thrombophlebitis are present in this setting: stasis (i.e reduced blood flow in the veins) and the activation of blood clotting mechanisms. Stasis occurs as a result of the immobilization during surgery and the immediate postoperative period. Surgery activates blood clotting mechanisms as a mean of normal control of bleeding and promoting wound healing. In a sense, venous thrombosis is the result of an excessive or exaggerated normal blood clotting reaction.

Could the deaths of Suzan or Dr F. have been prevented?

Sadly enough, both these deaths could have been averted. How? In the case of Suzan, death ensued because none of the treating physicians considered the possibility of thrombophlebitis. If this diagnosis had been made, she would have been treated with anticoagulant drugs and, almost certainly, would have survived. In all likelihood, the diagnosis of thrombophlebitis was not considered because this disease is fairly uncommon in young patients. Thus, there may be a low index of suspicion. What is the lesson? If one has unexplained leg pain and swelling, particularly following trauma, major surgery or prolonged immobilization, tests for thrombophlebitis should be performed. What are these tests? Until recently, it consisted mainly of venography. Venography is a radiological examination in which a contrast substance is injected via a foot vein. The purpose of the examination is to visualize by x-rays the deep veins of the legs and establish either the presence or the absence of blood clots. More recently, there has been a shift toward noninvasive methods. Noninvasive methods are devoid of the discomfort caused by venography. The two main noninvasive techniques for diagnosing deep vein thrombophlebitis are impedance plethysmography and ultrasound examination. Both these techniques are available at The Montreal General Hospital and many other major university-teaching hospitals. With either method, a complete examination takes approximately 15 minutes.

In the case of Dr F., the key to survival would have been the use of preventive measures. Major orthopedic surgery of the leg carries a relatively high risk of thrombophlebitis and pulmonary embolism. Prevention consists of the use of low doses of anticoagulant drugs in order to prevent blood clot formation. Such preventive measures are based on the principle that much lower doses of anticoagulant drugs are required to prevent the formation of thrombophlebitis than to treat an already established clot. In experienced hands, these drugs will markedly diminish the risk of thrombophebitis and pulmonary embolism without increasing the risk of surgical bleeding or the impairment of wound healing. The reported case of Dr F. occurred at a time (not so long ago) when safe and effective preventive measures after major orthopedic surgery were non-existent.
In 1987, in collaboration with the Division of Orthopedic Surgery, we instituted at The Montreal General Hospital a program for prevention of thrombophlebitis and pulmonary embolism. During this program, not one post-surgical case of major pulmonary embolism occurred. Our program has also permitted us to evaluate newer and safer anticoagulant drugs for the prevention of thrombophlebitis and pulmonary embolism.
Which lesson can be learned from the case of Dr F.? If you undergo major orthopedic or other surgery, ask your physician for the use of preventive measures.


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