Scanning the Lungs For Blood Clots

DIAGNOSIS Scanning the Lungs For Blood Clots Whenever a large blood clot blocks the artery leading from the heart to the lungs, the result is so dramatic and catastrophic -- in many cases, fatal --that doctors find the difficulty relatively easy to diagnose. But small clots that block some of the smaller arterial branches are far more common than such massive pulmonary embolisms. The trouble is, they are so hard to detect that the true nature of the illness is often missed. Patients complain of shortness of breath, they faint frequently, and they may collapse after exertion, leaving their doctors baffled. Now, atomic medicine is coming to the aid of chest physicians and embolism patients with an ingenious and relatively simple diagnostic procedure.

The clots do not show clearly on X rays, and neither do the dead areas of lung surface beyond them. But Dr. George V. Taplin of U.C.L.A. figured that he could spot them with a radioactive substance, which after injection into the veins would pile up at the arterial roadblocks while flowing freely through normal blood vessels. The next problem was to find a radioactive chemical that would do the job, and then disappear harmlessly--preferably a substance that occurs naturally in the human body.

24-Hour Flush. Working with the radiopharmaceutical division of E. R. Squibb & Sons, Dr. Taplin found what he wanted: human albumin, but in a special form made up of large molecules too big to pass through the lungs' blood filters, and laced with radioactive iodine. Dr. Taplin proved in dogs that these macro-molecules would jam up in the clot-closed arteries, stay there long enough to take their own picture on an X-ray plate, then break up into the normal, small-molecule form of albumin and pass into the bloodstream.

Dr. Henry N. Wagner Jr. of Johns Hopkins Hospital became the first human guinea pig to try the "Albumatope" injection on himself. He has since used it, with iodine 131, to get revealing scintillation-scan pictures of 225 patients, with no ill effects. Dr. Taplin himself has now used the technique for more than 150 patients. He employs iodine 125. The safety of the method is attested by the fact that the radiation dose each patient receives is much less than he would get from special chest X rays for this purpose. And the minute amount of radioactive iodine is flushed out of his body within 24 hours.

What to Do. Once they have an accurate diagnosis, doctors can decide what the patient needs. In the severest cases, surgery with the heart-lung machine is called for; in others, oxygen to tide patients over a crisis. But for most victims, drugs are enough: heparin to guard against the formation of new clots, norepinephrine to keep up the blood pressure. Dr. Wagner has high hopes for a new enzyme to dissolve old clots.

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