Biochemical Test To Help Diagnose Aortic Dissection

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The summary below is from the full report titled "Diagnostic Implications of Elevated Levels of Smooth-Muscle Myosin Heavy-Chain Protein in Acute Aortic Dissection. The Smooth Muscle Myosin Heavy Chain Study." It is in the 3 October 2000 issue of Annals of Internal Medicine (volume 133, pages 537-541). The authors are T Suzuki, H Katoh, Y Tsuchio, A Hasegawa, M Kurabayashi, A Ohira, K Hiramori, Y Sakomura, H Kasanuki, S Hori, N Aikawa, S Abe, C Tei, Y Nakagawa, M Nobuyoshi, K Misu, T Sumiyoshi, and R Nagai.

What is the problem and what is known about it so far?

The aorta is the largest blood vessel, bringing blood from the heart to the rest of the body. Aortic dissection is a potentially deadly condition in which the muscular wall of the aorta becomes torn. Diagnosing aortic dissection quickly and accurately is very important since this condition needs to be treated immediately. Unfortunately, the condition can be difficult to diagnose. Doctors ordinarily use special imaging studies to diagnose aortic dissection, but these studies are not always immediately available and can be time-consuming. The authors of this study have developed a blood test that measures a substance (smooth-muscle myosin heavy-chain protein) that is released from the muscular wall of the aorta into the blood when dissection occurs. Finding large amounts of this substance might help in the diagnosis of aortic dissection, but the usefulness of the test for that purpose is not known.

Why did the researchers do this particular study?

To determine how well a rapid (30-minute) test of circulating smooth-muscle myosin heavy-chain protein diagnoses aortic dissection.

Who was studied?

95 patients with acute aortic dissection from eight major medical centers in Japan. The diagnosis was confirmed in all patients by special imaging studies. The study also included 131 healthy volunteers who presented for a routine health examination and 48 persons who were within 3 hours of having had a heart attack. (The symptoms of a heart attack can be very much like those of aortic dissection.)

How was the study done?

The researchers measured blood levels of smooth-muscle myosin heavy-chain protein in the patients in all three groups.

What did the researchers find?

The levels of the protein were much higher in patients with dissection than in healthy volunteers or persons who had just had a heart attack. The test appeared to be most helpful in patients who were tested within 3 hours of developing symptoms or who had aortic dissections close to the heart rather than farther away from it. The researchers also determined the blood level of the protein (2.5 µg per milliliter) that best distinguished patients with aortic dissection from the comparison patients.

What were the limitations of the study?

This study was small, and doctors did not actually use this test to make treatment decisions since all of the patients with dissection were also proven to have this condition by imaging studies. The test is still preclinical, and a larger group of patients with sudden chest pain will need to be studied to confirm its usefulness.

What are the implications of the study?

A rapid test of circulating smooth-muscle myosin heavy-chain protein seems potentially useful in helping to diagnose aortic dissection.