New Technology Draws 3-D Map Of Heart

By Lawrence Surtees, The Canadian Press

TORONTO, Jun 27, 1999 (The Canadian Press via COMTEX) -- Cardiologists at St. Michael's Hospital in Toronto are charting new territory inside the heart with a unique catheter that heralds a radical advance in the treatment of coronary artery disease.

Equipped with tiny sensors on its tip, the device -- called a Noga catheter -- enables heart doctors to produce three-dimensional maps of both the mechanical and electrical functions of the muscle of the heart's main pumping chamber.

And soon, the Toronto heart doctors hope to use another version of the catheter equipped with a needle to provide a dramatic treatment for patients with blocked arteries, like Dale Woodcock.

He has already had two bypass operations to restore blood flow to a region of his heart muscle starved by a blocked coronary artery.

The 58-year-old says he is easily winded by exertion, and has had to give up playing his favourite sport, hockey, in favour of golf. Woodcock, who runs a glass company in Oshawa, Ont., was the third Canadian to have the inside of his heart examined with the experimental Noga catheter.

Now, Woodcock is a candidate for an experimental procedure that will use the Noga catheter to inject genes into damaged heart muscle, spurring the growth of new blood vessels that will circumvent a potentially lethal blockage.

He's not expecting to play a pick-up game of hockey any time soon, but Woodcock is hoping that he'll be able to walk a golf course, instead of driving a cart. ''I'm willing to try it, and look forward to any improvement it may offer.''

Dr. Duncan Stewart, head of the cardiology division at St. Michael's, says the Noga catheter is the ideal non-surgical way to insert genes into the heart muscle. The only other method is to cut the patient's chest open.

Stewart expects to obtain permission later this summer to begin the Canadian portion of a landmark North American-wide trial of the therapy with Parke-Davis, the pharmaceutical arm of Warner-Lambert Co. They hope to begin the tests this fall.

Cardiologists consider this research to be one of the most promising new developments to treat cardiovascular disease -- the biggest killer of Canadians.

''If gene therapy delivered via a non-surgical approach is proven effective, it will transform the way we treat many patients today,'' says Dr. Martin Leon, chairman of the Cardiology Research Foundation at Washington Hospital Center in Washington, D.C.

The Noga catheter was invented by a group of Israeli researchers, who sold their company, Biosense Inc., to the Cordis Corp. unit of U.S.-based medical equipment giant Johnson and Johnson in 1997.

Because it does not use any radioactive dye to produce its images, the catheter overcomes the shortcomings of angiograms -- a cardiac catheterization technique now widely used.

Angiography is limited to producing images of the heart's own arteries and a vague silhouette of the background heart muscle.

But the Noga method gives cardiologists much more detailed information about the heart muscle. Because Noga eliminates the need for X-ray devices, it is safer for both patient and doctor.

Instead of dye, the Noga catheter uses a low-level electromagnetic field to detect the movement of the catheter tip, which is equipped with several tiny sensors.

As the catheter is threaded into the left ventricle, a detector connected to a computer workstation detects changes in the position of the sensors on the Noga's tip. And that enables a cardiologist to generate three-dimensional images of the chamber inside a patient's heart.

But the Noga catheter measures much more than just position.

Each time the catheter tip is placed against the wall of the heart chamber, the sensors measure the electric voltage of the heart muscle cells, recording the information on a map. If the tip is held in place during a full heart beat, the Noga system measures the force of the heart muscle at the same point on a second map.

It is when those two maps are compared that cardiologists obtain an improved tool to precisely diagnose the impact of coronary artery disease.

If an area of heart muscle deprived of blood supply by a blocked artery is dead -- or infarcted -- then the Noga maps will show no voltage and no movement. However, an area of muscle that has no movement yet still has electric impulses is termed ischemic -- damaged by chronic disease -- and reparable, says Dr. Stewart.

His team is the first in Canada to use the Noga procedure on humans. So far, they have made Noga maps of three patients, including Woodcock. Although the use of Noga is still in its infancy, Stewart's team believes it will prove to be a more reliable tool to identify dormant muscle and to better target their treatments.