A series of new studies published in this week’s Journal of the American Medical Association underscore the complicated nature of new recommendations that could potentially change the basic ways that doctors treat high cholesterol and high blood pressure—two major risk factors for heart disease. They also raise a subject that we physicians don’t like to talk about: our emotional reluctance to change habits that we have relied upon for decades.
The historical record is full of instances in which doctors—wedded to earlier understandings of disease—have disregarded scientific advances. A particularly good example is the opening of diseased blood vessels to prevent heart attacks, a story told in the 2013 book, Broken Hearts: The Tangled History of Cardiac Care, by David S. Jones. Revisiting Jones’ story can help modern physicians—and their patients—avoid reflexive thinking and carefully incorporate new insights.
Jones chronicles the changing understandings of coronary artery disease, which is the buildup of cholesterol and other abnormal substances in the blood vessels surrounding the heart. For most of the 20th century, physicians believed heart attacks resulted from the progressive clogging, or occluding, of these arteries. After all, they knew from autopsy studies that patients experienced chest pain—also known as angina—when vessels were more than 80 to 90 percent closed. There was simply not enough oxygen getting to the heart.
They also knew that coronary artery surgery, in which unobstructed blood vessels from elsewhere in the body were used to bypass the affected areas, relieved the angina. So did angioplasty, introduced in the late 1970’s, in which doctors used balloons and stents to clean out and keep open clogged arteries.
So it made sense to conclude that bypassing or opening diseased blood vessels would also prevent heart attacks (during which there is complete occlusion of a particular vessel and resultant death of heart tissue). Once vessels became about 95 percent occluded, doctors believed, a tiny blood clot could obstruct them entirely. Alleviating obstructions became the gospel for prevention.
As early as the 1930’s, however, there were naysayers. Some physicians believed heart attacks resulted from some type of rupture within the vessel; how much occlusion was present did not matter. Over the succeeding decades, researchers confirmed that this theory was indeed true. The rupture of plaques containing fat, cholesterol, calcium, and other substances caused heart attacks. Drugs such as statins that lowered cholesterol levels and stabilized these plaques, thus prevented heart attacks.
Yet, as Jones describes, cardiologists have been remarkably slow to abandon the old hypothesis, continuing to perform hundreds of thousands of bypass operations and angioplasties annually not only in the setting of heart attacks (when they are appropriate) but also to try to prevent them. In his book, Jones points out that a 2011 study found that as many as 85 percent of angioplasties were elective and non-emergent.
Jones readily admits there are financial reasons for the continued use of these procedures. Bypass and angioplasty make money for physicians and hospitals. But other explanations—what he terms “emotional and psychological”—are more interesting and especially relevant to current debates about treating high cholesterol and hypertension.