The voice said, Cry. And he said What shall I cry?

All flesh is grass, and all the goodliness thereof is as the flower of the field:

The grass withereth, the flower fadeth, because the spirit of the Lord bloweth upon it. Surely the people is grass. Isaiah, Chap. 40, V. 6, 7

The heart is an aching mystery in medicine, even when doctors can move a heart from a dead man to a dying man, even when they can hold a heart in their hands while a machine does its work. Doctors can cut away the heart's arteries and put elastic tubes in their place. They can make a heart out of plastic and sew it into your body.

What they can not do is tell us why a flower fades at full bloom.

Jon Walash was 16, soon to be 17, as strong as an offensive lineman need be, as agile as a wrestler need be. In July, he ran a mile at wrestling camp carrying a buddy on his back. In August, he dropped dead at the mile mark on a routine 1 1/2-mile run at Robinson High School. Simply feel dead. No sound of pain. His father said the Lord wanted Jon.

The ache of inexplicable death ran deep through athletes, parents and coaches, all forced to ask the question they avoid: What about me?Can it happen to me, to my son, to my player? Can I be alive one second, dead the next?

The answer, like the heart, is a mystery, an enigma of darkness whose shadows can not be chased away. But five doctors in Washington have done a study suggesting that a death such as Jon Walsh's likely is directly attributable to heart disease. If a person has heart disease, such a death could come at any time.

Jon Walsh, should his death fit the established pattern, might have died the next week doing something less strenuous than running a mile with a buddy on his back.

Something like walking to his car.

Drs. William Roberts, Barry Maron, Douglas Rosing, Stephen Epstein and Hugh McAllister -- all associated either with the National Institutes of Health or the Armed Forces Institute of Pathology -- co-authored an article entitled, "Sudden Death in Young Athletes." It appeared in the August 1980, issue of The American Journal of Cardiology.

The doctors put together research on the "sudden and unexpected deaths" of 29 young, active athletes who "epitomize the conditioned, health segment of society." The athletes were 13 to 30 years old, from junior high to professional football, and they had been in competition at least two years.

"In 28 of the 29 athletes," the article said, "death occurred suddenly without warning and was virtually instantaneous; the other athlete survied 12 hours in a terminal state after her collapse."

Of the 29 athletes, 28 had heart disease.

Of the 28, 22 almost certainly died of it.

Of those 22, 14 had one specific disease.

That disease, hypertrophic cardiomyopathy, is practically never discovered until somebody falls dead with it.

At the moment of such death, the heart that helped an athlete move smoothly and gracefully is itself moving clumsily, its muscle cells disorganized and uncoordinated. the heart is in panic. The muscle is out of control, twitching instead of beating rhythmically. For too long it has worked too hard, the victim of disease, and now it is saying it can't do this any more.

The medical term for the heart's panic is ventricular fibrillation.

The heart disease in the 29 cases was apparent in structural cardiovascular abnormalities.

The hearts weren't built right. At conception, the heart is no more than a simple tube. By the first month, the tube is twisting and dividing to form the heart's arteries and chambers. Before the construction is complete, some 900 errors are possible.

Hypertrophic cardiomyopathy means the heart muscle is enlarged and diseased. The heart has two large chambers. The left ventricle sends blood through the body, the right ventricle sends it to the lungs for purification. The ventricles are divided by the ventricular septum, a wall of muscle. That wall, in 10 of these 14 fatal instances, was enlarged and diseased. In the other four cases, the outside ventricular wall was thickened.

So diseased, the ventricles work too hard. A normal heart pumps five liters of blood a minute; the hypertrophic heart may pump five liters in half a minute. It may pump 80 percent of its capacity in the first half of a contraction. It can not do this indefinitely, as the 14 deaths studied show.

The other eight deaths were caused by ruptured aorta (two), atherosclerotic coronary disease (three) and anomalous origin of the left coronary artery (three). Atherosclerosis is thickening of the arteries. To say an artery has an anomalous origin means it begins in the wrong place in the heart, fouling up the works.

And no one knows why.

"Hypertrophic cardiomyopathy tends to be in pretty strong, healthy-looking people," said Dr. Roberts this week. "That is the cruelest irony of all."

What the doctors know is that hypertrophic cardiomyopathy, along with several variations of heart disease, is congenital. It happened when all that twisting and dividing was going on.

"It is a heart muscle disease of unknown cause, but it is a familial thing," Roberts said. One of the 29 athletes died after a brother's sudden and unexpected death. "To any family with such a death, I say this: The rest of the family has to be checked out. Everyone should have an echocardiogram done."

Had an echocardiographic examination been done on the 14 young athletes, death might have been prevented.

The echocardiogram is a new instrument of medicine, only a dozen years in use. It operates similarly to sonar, bouncing sound waves off the heart to make a picture of sorts. It is the only device that can give evidence of the thickening of the heart muscle that is symptomatic of hypertrophic cardiomyopathy.

Screening of athletes by personal and family history, physical examination, electrocardiogram and echocardiogram would have identified as diseased most of the 29 athletes in their study, according to the five Washington doctors.

"However," they wrote, "routine comprehensive screening of this type would probably be impractical."

"It would be pretty expensive," Dr. Roberts said, "to do an echocardiogram."

The cost would be about $100.

And the test is no guarantee of safety against sudden death.

Athletes and joggers get the frightening publicity, but housewives and dentists die of heart attacks every day.

"I go to the D.C. morgue onace a month to see cases of sudden death," Roberts said. "Sudden death, as the first manifestation of heart disease, is very common."

Hypertrophic cardiomyopathy was first diagnosed only 20 years ago, Roberts said, and the prescribed treatment of the drug propranolol is debatable.

He would advise getting out of competitive athletics.

Of the 29 sudden deaths, 22 occurred during an athletic event or training. Two deaths happened during or just after mild exertion not related to athletics. The other five athletes died during sedentary activities.

"Circumstantial evidence would suggest that competitive athletics contributes to the deaths," Roberts said. "The logic is that these diseased hearts work too hard under resting conditions and are probably aggravated under exercise."

Aggravated, the hearts panic. Ventricular fibrillation begins. An electric-shock defibrillator sometimes stops the panic. The patient lives.

Might athletic teams be wise to have defbrillators within reach?

"You'd have to have an ambulance with paramedics at the side of each athlete 24 hours a day," said Roberts.

The flower can fall from high bloom at any moment. Could Jon Walsh, if he had hypertrophic cardiomyopathy, have died walking to his car?

"Absolutely," the doctor said.