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Echocardiography: Telltale Images of the Heart : Non-Invasive Procedure Called an Accurate, Low-Risk Test for Deadly Disease

July 22, 1986|PATRICK MOTT

The shape pulsating on the small video screen looks like some type of dangerous microbe, a movie shot through the lens of a microscope. Actually, it is far worse.

With computer-generated dotted lines showing the four-chambered image, the shape can be identified as a perilously expanded human heart. It is a heart, Dr. Gus Kunelis said, that will almost surely kill its owner.

It is also a heart that did not betray its potentially deadly nature on the tape of an electrocardiogram or during a conventional treadmill stress test.

But when the 45-year-old man was tested at St. Jude Hospital & Rehabilitation Center in Fullerton using the computer-enhanced screen image, the result "was so bad that we couldn't even operate on him," Kunelis said. "And that case isn't one in a million. It's frequent enough that it is frightening."

The high-tech cardiac sleuth is called stress echocardiography, and it may help save many diseased hearts whose problems would have gone undetected, said Kunelis and Dr. Donald Mahony, who are associate director and director, respectively, of St. Jude's Non-Invasive Lab.

The technique is called "non-invasive," Mahony said, because it requires no injections or catheters.

Detects 'Silent Killer'

The procedure is designed to detect coronary artery disease, particularly myocardial ischemia, the so-called "silent killer" artery blockage that often causes sudden death. Echocardiography is being hailed in many cardiology circles as safe, accurate, inexpensive and easy, and Mahony said physicians "are going through here like a revolving door" to learn how to administer the test. The St. Jude lab is the only medical facility in Orange County performing the stress echo test. It is also offered at Harbor-UCLA Medical Center in Torrance, UCLA Medical Center, Loma Linda Medical Center and Desert Hospital in Palm Springs.

The test uses ultrasound waves to form a video image of the heart. The waves echo from the heart's surface to a sensing device that measures the volume of blood expelled after each contraction and the motion of the heart wall. The waves are produced by a transducer, which is placed at different angles to the heart outside the patient's chest.

It's called a stress test because the patient lies on his back and pedals a bicycle chain-wheel mechanism attached to the end of the table. The exercise elevates the heartbeat and allows comparisons between the heart under resting conditions and during physical exertion.

The patient also is monitored throughout the test by a blood pressure meter and a 12-lead electrocardiogram. But, Mahony said, "we can see all kinds of heart muscle defects on the echo even though the EKG is running along normally."

Mahony said he uses the supine bicycling technique at St. Jude, rather than an upright bicycle or a treadmill, because it causes a greater flow of blood to the heart and is therefore more apt to signal an abnormality.

The image on the screen is videotaped and run through a computer, which traces the outline of the heart and its chambers with white dotted lines.

Stress echocardiography has seen limited use since the early 1970s, Mahony said, but the equipment was cruder and often couldn't produce a decipherable picture. Today, however, the pictures show resolution on objects as small as a millimeter, he said.

He said a stress echo test costs about $500, about the same as a thallium scan, a series of X-rays of blood flow around the heart.

Perhaps the greatest advantage, however, is the capability of stress echocardiography to detect heart irregularities that display no warning signs or that may be missed during a resting electrocardiogram, treadmill test or thallium scan, Kunelis said.

A resting or treadmill electrocardiogram, he said, can only measure electrical impulses from the heart and therefore cannot accurately indicate such irregularities as abnormal heart wall motion or impaired blood flow. It is accurate 58% to 75% of the time in diagnosing coronary artery disease, Kunelis said. A thallium scan can also be fooled, he said. While thallium can pick up impaired blood flow in selected arteries, if all such arteries are about equally blocked the scan will appear normal, Kunelis said. It has an accuracy rate of 60% to 85%.

Echo Accuracy Rate

In 2 1/2 years, St. Jude doctors have performed about 800 stress echo tests, Mahony said, and subsequent testing to confirm the diagnosis has shown stress echo to be accurate 97% of the time.

Recently, Kunelis said, a 65-year-old man with no previous symptoms of heart disease was given a stress echocardiography test at St. Jude. He had passed a treadmill test and two thallium scans, Kunelis said. But the man's doctor believed there could be indications of heart disease and sent his patient to the Non-Invasive Lab.

"The resting part of his test was abnormal, but when we stressed him, it was horribly abnormal," Kunelis said. "He had an angiogram done, and it showed severe triple valve disease."

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