Professor of Genomics, The Scripps Translational Science Institute; Author, The Patient Will See You Now
Simplistic Disease Progression

The leading killer diseases—heart and cancer—don’t follow old dogma.

The two leading causes of death are heart attacks and cancer. For much too long we’ve had the wrong concept about the natural history of these conditions.

There are common threads for these two diseases: People generally don’t die of cholesterol buildup in their arteries (atherosclerosis) unless they have a heart attack or stroke; similarly, cancer rarely causes death unless it metastasizes.

For decades, it was believed that cholesterol build up inside an artery supplying the heart muscle followed a slow, progressive development. As the plaque grew bigger and bigger, as the theory goes, it eventually would clog up the artery and cause interruption of blood supply—a heart attack. That turned out not to be true at all, since it’s the minor cholesterol narrowings that are, by far, the most common precursors to a heart attack. The heart attack results from a blood clot as the body tries to seal a sudden crack in the wall of the artery. The crack is an outgrowth of inflammation. It doesn’t cause any symptoms until a blood clot forms and heart muscle is starved for oxygen. That’s why people who have heart attacks often have no warning symptoms or can have a perfect exercise stress test but keel over days later.

There’s a second concept regarding heart attacks that should be more widely known. The media often mislabel a sudden death or a heart rhythm problem as a “heart attack.” That’s wrong. A heart attack is defined by loss of blood supply to the heart. If that leads to a chaotic heart rhythm it can result in death. But most people with heart attacks have chest pain and other symptoms. Separately, a person can have an electrical heart rhythm event without anything to do with atherosclerosis and that can cause death. That is not a heart attack.

With a better understanding of what is a heart attack and its basis, more recently, cancer is following suit. The longstanding dogma was that cancer slowly progresses over years until it starts to spread throughout the body. But now it has been shown that metastasis can indeed occur with early lesions, defying the linear model of cancer’s natural history. We knew that mammography picks up early breast cancer, for example, but that has not had a meaningful impact on saving lives. So much for the simplistic notion for how cancer develops, perhaps one of the reasons it has been so difficult to treat.

With the global health burden so largely explained by these two killer diseases, it is vital we raise awareness and reboot our preventive strategies in the future.