Most sudden cardiovascular deaths in women occur without previous symptoms. Although screening asymptomatic men with exercise testing has been shown to have a mortality benefit, it is not known whether this benefit applies to women. Mora and colleagues investigated whether exercise testing variables were independent predictors of all-cause mortality or cardiovascular death in women.
The study enrolled participants from the Lipid Research Clinics Prevalence Study and included 2,994 asymptomatic women between 30 and 80 years of age. Participants underwent exercise testing using a Bruce treadmill protocol. Cardiovascular risk factors such as diabetes and hypertension were assessed and used to stratify risk according to the 1998 Framingham risk equation.
During a mean follow-up of 20.3 years, there were 427 deaths (14 percent) from any cause, including 147 deaths (34 percent of all deaths) from cardiovascular causes. Peak exercise and heart rate recovery (HRR) diverged early and continued to diverge over the study period, with a graded increase in mortality for decreasing quintiles of exercise capacity and HRR. After age adjustment, the effects of exercise capacity, HRR, failure to achieve target heart rate, and exercise-induced ventricular arrhythmia on cardiovascular and all-cause mortality were similar in magnitude to the effects of traditional cardiovascular risk factors. For exercise capacity and HRR, there was a strong and graded association between decreasing quintiles and age-adjusted cardiovascular risk and all-cause mortality. Exercise-induced ST-segment depression of at least 1 or 2 mm did not predict cardiovascular death. Women who were below the median with respect to exercise capacity and HRR had a 3.5-fold increased risk of cardiovascular death compared with women who were above the median for both variables. The majority of women had low Framingham risk scores at baseline; within this low-risk group, risk remained lowest when women performed at greater than the median on one or both variables, exercise capacity and HRR.
This study demonstrates that exercise capacity and HRR are strong, graded, and independent predictors of cardiovascular and all-cause mortality, while ST-segment depression is not. Treadmill testing has a potential role for further risk stratification in asymptomatic women with low or intermediate Framingham risk scores. One limitation of the study is that it is unclear to what extent the treadmill testing represents a modifiable risk factor.