Lasers advancing on heart problems.

Lasers advancing on heart problems

Lasers are making a rapid advance on heart disease. They have already reamed out clogged heart arteries during coronary bypass operations (SN: 11/23/85, p.327), and at the recent American Heart Association meeting in Dallas, researchers detailed initial human trials of lasers to treat erratically beating hearts as well as a simpler approach to atherosclerotic arteries.

While showing promise on two of the major problems of cardiology, lasers have their limitations. Using them to bust the clots involved in heart attacks, for instance, "would be like trying to burn Jell-O," one researcher says.

Several groups have used lasers to treat ventricular tachycardia, a condition in which part of the heart does not properly conduct the electrical signals that trigger beating. The heart contracts erratically, and death can result.

The condition is conventionally treated by drugs; for people who don't respond, operations to freeze or surgically remove the problem area are sometimes done. The laser treatment, say its developers, can benefit people whose arrhythmic areas are difficult to reach with scalpels or freezing devices, and once it is developed it may prove simpler and safer than either cutting or freezing.

Laser destruction of arrhythmias was first done a couple of years ago in France. At the Dallas meeting, Robert H. Svenson and his colleagues at the Sanger Clinic in Charlotte, N.C., described their use of the procedure in 21 patients, and Sanjeev Saksena of Newark (N.J.) Beth Israel Medical Center described its use in 12 patients. In both trials the patients had not responded to drug therapy.

In the Beth Israel procedure, worked out after years of animal trials, surgeons put patients on a bypass machine. With the hearts still beating but not pumping blood, the surgeons cut into the hearts with scalpels or lasers. They checked the heart's conduction patterns by applying electrical current and vaporized problem spots on the inner wall with lasers.

Eleven of the 12 people treated had no more tachycardia; the twelfth responded to drug therapy, says Saksena. About half of them would have been dead within a year, he estimates.

The Charlotte group used a laser tuned to kill but not vaporize the erratically firing cells. One patient died during the procedure and one shortly after; of the remaining 15, all but one appeared to be free of tachycardia, Svenson reported at the meeting.

Lasers have also been used on a more common problem, clogging of the arteries that feed the heart muscle itself. While lasers have been used point-blank during bypass surgery, the work presented at the meeting concerned laser energy delivered via fiber optics threaded through the patient's leg and up to the narrowed heart vessel.

The treatments began just a few months ago at Boston University and Northern Hospital in Sheffield, England, following use on clogged leg arteries in people. Timothy Sanborn, who heads the Boston project, says surgeons there have used a 1.7-millimeter-diameter metal tip heated to 400[deg.]C by laser light to treat seven people with coronary arteries that were 90 to 95 percent narrowed.

The device decreased the narrowing in four of the seven -- from 95 percent blocked to 20 to 30 percent. A balloon inflated in the artery pushed back the arterial walls a little more. Perforations and blood clots, which have occurred in animal trials and with human leg arteries, were not a problem, says Sanborn. "Laser thermal angioplasty in the coronary system is in its early stages," he says. "The initial results are very encouraging."

The laser, he says, may someday be used to clear out the blockage completely without the balloon follow-up; the process could prove more resistant to the reblocking that often occurs after balloon use. The advantage of lasers over balloons, says Sanborn, "is that you leave behind a very smooth arterial surface. [Plaque] is removed rather than stressed or fractured."

"The preliminary experience has indicated [lasers] can be used successfully in the human [heart]," says laser researcher Jeffrey M. Isner of Tufts University-New England Medical Center in Boston. "As recently as a year and a half ago, some people believed it couldn't be done."

When will lasers move from an experimental process to conventional therapy? "For the past six years we've been saying in two years," says George S. Abela of the University of Florida in Gainesville, who is credited with much of the research that laid the groundwork for human trials. "So I'll say in two years."