In his recent (2017) book, Timothy Jennings writes of the dangers of unrecognized heart issues:

Hypertension—high blood pressure—has been called the silent killer, but medical professionals didn't always realize this. In fact, some doctors argued that hypertension was a made-up disorder that didn't need to be treated at all. For instance, in 1931 Dr. J.H. Hay proclaimed, "The greatest danger to a man with high blood pressure lies in its discovery, because then some fool is certain to try and reduce it."

Tragic results followed from this idea. Consider the true case of Frank. Frank was diagnosed with hypertension in 1937 at the age of fifty-four. His blood pressure was 162/98 and was considered by physicians at the time to be "mild hypertension." No treatment was initiated. By 1940, his blood pressure was running 180/88. In 1941, his pressure was 188/105. He was encouraged to cut back on smoking and work. But his condition didn't improve.

By 1944, his pressure was running higher, and he suffered a series of small strokes. This was followed by classic symptoms of heart failure, so he was placed on a low-salt diet with hydrotherapy and experienced some improvement.

But by February 1945, his pressure was 260/145, and on April 12, 1945, he complained of a severe headache with his blood pressure measuring at 300/190. He lost consciousness and died later that day at the age of sixty-three. Perhaps you know him better as Franklin Delano Roosevelt, the thirty-second president of the United States.

Unrecognized problems (like sin, for instance) can cause devastating results. But it is much worse when the professionals who are supposed to identify and treat the problem deny it even exists.