The first clue is often the catastrophe itself: a fatal heart attack. But the events that set the stage for disaster, like those preceding an earthquake, have been occurring for years beneath the surface, painless and unnoticed. The culprit is silent ischemia, an intermittent interruption of blood flow to the heart, which kills tens of thousands of seemingly healthy Americans each year. Doctors estimate that the condition, undetected, exists in an additional 3 million to 4 million people known to have heart disease and further increases the likelihood they will suffer a heart attack.
Although silent ischemia was identified nearly two...