Changes in the heart due to smoking have finally been measured.
Smoking is a major preventable cause of cardiovascular disease.
It has been established that smoking tobacco leads to an increased risk of heart failure, even in individuals without cardiovascular disease.
However, the mechanism by which tobacco damages the heart and causes cardiovascular events has not been found.
Imaging studies examining changes in heart structure associated with smoking have been carried out; however, to date, the results have been conflicting.
Some researchers have found an association with an increase in the mass of the heart's left ventricle; others found no change and others still found a reduction in mass.
The importance of the left ventricle
The left ventricle is of particular interest to tobacco researchers because it is a vital player in the pumping system of the heart. The left ventricle's wall is predominantly made of muscle, so, like any muscle, it increases in size in response to being worked harder.
Certain health factors can increase the heart's workload and, consequently, the thickness of the left ventricle wall (left ventricle hypertrophy); these factors include some heart conditions and high blood pressure.
In an attempt to produce a clearer picture, a team of researchers recently examined the hearts of thousands of individuals from the Atherosclerosis Risk in Communities (ARIC) Study. They were drawn from four communities in the United States: Forsyth County, NC; Jackson, MS; the suburbs of Minneapolis, MN; and Washington County, MD.
With an average age of 75.5, none had obvious signs of cardiovascular disease. Through questionnaires, the researchers gauged how long each participant had smoked and calculated how many cigarettes they had smoked over their lifetime.
Of the 4,580 individuals, 287 (6.3 percent) were current smokers, 2,316 (50.5 percent) were former smokers, and 1,977 (43.2 percent) had never smoked.
To ensure the results were only charting the interaction between smoking and cardiac events, the investigators accounted for multiple factors within their analysis, including race, age, body mass index, diabetes, blood pressure, and alcohol consumption.
Measuring smoking's impact on the heart
Each participant underwent an echocardiogram - a scan that uses high-frequency sounds to create an image of the heart and nearby blood vessels. When the scans were assessed, it became clear that within the group that smoked, the walls of their left ventricles were significantly thicker.
"These data suggest that smoking can independently lead to thickening of the heart and worsening of heart function, which may lead to a higher risk for heart failure, even in people who don't have heart attacks."
Dr. Wilson Nadruz Jr., Ph.D., lead author
The data showed a clear relationship between the amount of tobacco smoked, the size of the left ventricle wall, and a reduction in pumping function; as Dr. Nadruz says, "the more people smoke, the greater the damage to the heart's structure and function, which reinforces the recommendations stating that smoking is dangerous and should be stopped."
However, the news was not all bad. According to Dr. Scott Solomon, senior study author and professor of medicine at Harvard Medical School and Brigham and Women's Hospital, "former smokers had similar heart structure and function compared with never smokers." In other words, after quitting smoking, the heart seems able to bring itself back within normal, safe parameters.
The study brings to the fore yet another stark message regarding the dangers of smoking tobacco. On the other hand, it gives smokers who are considering quitting another reason to keep trying. It is a difficult habit to kick, but once the cycle has been broken, the heart can heal.