| Cardiologist Katherine Wu scans MRI images in search of dangerous post-heart-attack blockages. |
The heart attack's finished. The patient's received tPA or streptokinase to unblock branches of cardiac arteries. Those vessels are now cleared and, after a careful recovery period, the patient should be fine, right? Not always. A recent series of MRI studies of patients, conducted by a team of cardiologists including Katherine C. Wu, M.D., and Joao A.C. Lima, M.D., show the smaller vessels -- arterioles and capillaries -- can remain blocked long after the crisis of an MI has passed. The vessels are clogged by clumps of white blood cells and other debris that accumulate after an attack. And the often-subtle damage to heart muscle from this microvessel blockage leads to a silent remodeling of ventricular tissue that not only cuts heart efficiency but also makes it vulnerable to complications such as congestive heart failure or another attack.
"Patients with blocked arterioles had many more problems within two years of a heart attack than those without, even though their major vessels were all open," Lima says. The good news is that such patients are now far easier to spot, with a simpler technique than MRI. Using the contrast medium Albunex, Wu and Lima use ultrasound to locate the blocked vessels. The machines can easily be wheeled to the patient's bedside, and results are typically quicker in coming than with MRI. One benefit of knowing small vessels remain blocked, says Lima, "is that we can single out which patients to watch. We can advise them to cut back their risk factors with strong evidence to back us up. We're currently screening both our own patients, after an MI, and those who've been treated elsewhere for their heart attacks." As for preventing the blockages in the first place, Lima says useful drugs are in the last testing stages. —Marjorie Centofanti
Hopkins Medical News, Summer 1999
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