NICE, FRANCE — When pulmonary embolism is suspected, clinicians also should be looking for thromboembolic disease in the venous system, Christian J. Herold, M.D., said at the annual meeting of the Cardiovascular and Interventional Radiological Society of Europe.
“In my experience, there is limited awareness regarding the role of the lower-extremity venous system as the prime source of pulmonary embolism,” said Dr. Herold, a radiologist at the University of Vienna Medical Center.
Pulmonary embolism and deep venous thrombosis are components of the same thromboembolic disease complex, Dr. Herold stressed.
He explained that as many as 70% of patients with proven pulmonary embolism also have proximal deep vein thrombosis.
Dr. Herold said the probability of pulmonary embolism should be assessed for every patient where the condition is suspected.
Imaging studies must be done in every patient with a moderate to high probability of pulmonary embolism.
“Diagnosis is very important because mortality is very high in undiagnosed and untreated patients,” he warned, putting the death rate in these patients at 10%–30% and emphasizing that the first week can be critical. “Unfortunately … many patients go unrecognized.”
Clinicians at his institution last year examined 4,250 patients for venous thromboembolic disease, Dr. Herold reported at the meeting.
The process relies heavily on CT and an easy to follow algorithm that is taught to medical residents at the hospital.
He said alternative diagnoses should be considered since ruling out pulmonary embolism does not mean the patient is disease free.
In one study, Dr. Herold noted, 70% of patients with suspicion of pulmonary embolism did not have pulmonary embolism.
“Many had alternative diagnoses, and CT provides you this information,” Dr. Herold advised, adding that “CT has evolved into an unofficial gold standard for analyzing pulmonary arteries.”
He urged that CT angiography and CT venography both be used when venous disease is suspected. “There is information in the body that you can retrieve using the same examination, the same bolus,” he said.
His group does CT venography 3 minutes after the pulmonary artery examination. “We prefer to do discontinuous slices with 3- to 4-cm gaps,” he said. “We don't miss clots with this technique.”
According to the medical literature, he added, CT venography has a sensitivity of 95%–100% and specificity of 97%–100%. He said studies in more than 5,300 patients have shown CT angiography to have a negative predictive value of 99%–100%, and that, therefore, it can be used to rule out treatment.
The radiologist cautioned, however, that in some patients, this rule does not always hold true. “All those guidelines and rules do not really account for 100% of patients. You may have individualized exceptions. And each patient has to be treated as an individual,” Dr. Herold advised.
Diagnosing Thromboembolic Disease: Keep the Process Simple
Many combinations of tests have been promoted as ideal algorithms for diagnosing pulmonary embolisms, Dr. Herold said.
Most are too complex. He urged institutions to develop their own simple approaches. As an example, he offered the following:
▸ All patients with intermediate or high clinical probability of pulmonary embolism (independent from any other clinical or laboratory result) must be imaged.
▸ Clinical symptoms determine the region to be imaged.
▸ No further imaging is required to institute treatment in a patient whose primary examination is positive.
▸ If the patient has a moderate or high clinical probability for pulmonary embolism and the primary imaging exam is negative, assess the complementary region with CT angiography, CT venography, and ultrasound.
▸ If the patient has a low clinical probability of pulmonary embolism, D-dimer tests can help determine whether imaging is necessary.
Dr. Herold noted that most algorithms involve CT angiography, D-dimer testing, and ultrasound. Lung ventilation-perfusion scanning and pulmonary angiography are rarely used, he said.