That's exactly the reason I started researching. The more literature I look through, the more it shows that the type of strength training Karas suggests is effective for heart health. I even found an article where Dr. Ken Cooper (he's Bush's doc and considered the "father of aerobics") agrees.
Here's part of what it said:
"'I've tried to be the guiding light,' he said, 'but I have to change my recommendations bases on the undeniable scientific evidence.' In 1968, he believed that a high level of aerobic fitness was a requirement for a long healthy life and that to achieve it, people had to walk three miles in less than 45 minutes, five days a week, or run two miles in less than 20 minutes, four times a week. But now he is convinced that people don't have to be aerobically fit to stay healthy. 'Overtraining might not only be unnecessary but might even be harmful,' said Dr. Cooper"
"At work with: Dr. Kenneth H. Cooper; the Fit Commandment" NY Times