Change in Physical Activity and Cardiac Structure over 10 Years: The Multi-Ethnic Study of Atherosclerosis.

INTRODUCTION: Physical activity (PA) is inversely associated with risk of heart failure and cardiovascular disease (CVD), whereas increased left ventricular (LV) mass and mass to volume (m:v) ratio are unfavorable CVD risk factors. We assessed whether changes in leisure time PA were associated with longitudinal changes in cardiac structure in a community-based population. METHODS: We included 2779 Multi-Ethnic Study of Atherosclerosis participants, free of baseline CVD, who had available data on PA and cardiac magnetic resonance imaging at examinations 1 (2000-2002) and 5 (2010-2012). Physical activity was measured by a Typical Week PA Survey and converted to MET-minutes per week of moderate+vigorous activity. We used linear mixed effect models to estimate the associations of baseline and change in PA with baseline and change in cardiac structure, adjusting for CVD risk factors and body size. RESULTS: At baseline, the mean age was 59 yr, 53% were women, and 58% of nonwhite race/ethnicity. During average 10-yr follow-up, and after accounting for baseline PA levels, the highest quintiles of PA increase were significantly associated with increases in LV mass (2.3 g; 95% confidence interval [CI], 0.4-4.2), LV end-diastolic volume (4.7 mL; 95% CI, 2.4-7.0), and stroke volume (3.3 mL; 95% CI, 1.6-5.1), but lower M:V ratio (-2.9; 95% CI, -5.0 to -0.8) compared with the lowest quintiles. Increasing exercise PA was associated with increases in LV diameter and reductions in M:V ratio, whereas occupational PA was associated with increases in m:v ratio. Increasing PA over 10 yr was also associated with greater risk of eccentric dilated LV hypertrophy at examination 5. CONCLUSIONS: After accounting for baseline PA, greater positive changes in leisure-time PA levels were associated with a more eccentric-type of LV remodeling pattern over 10 yr. The clinical implications of such findings remain to be determined.

Sex-Specific Maximum Predicted Heart Rate and Its Prognosis for Mortality and Myocardial Infarction.

PURPOSE: Maximum predicted heart rate (MPHR) is traditionally calculated by (220 - age). However, this formula's validity has been questioned in women. The purpose of this study was to derive sex-specific formulas for MPHR in a clinical population and compare their prognostic significance with the traditional formula. METHODS: This was a retrospective cohort of adults referred for exercise treadmill testing between 1991 and 2009. Peak heart rate versus age was plotted by sex, and linear regression analysis was used to derive sex-specific MPHR formulas. Cox models were used to calculate risk of death and myocardial infarction (MI) based on attainment of 85% MPHR using both formulas. RESULTS: Of 31,090 patients (mean ± SD, age = 55 ± 10 yr), there were 2824 deaths over 11 ± 5 yr. MPHR was best estimated by 197 - 0.8 × age for women and 204 - 0.9 × age for men (P interaction < 0.001). Compared with the sex-specific formulas, the traditional formula overestimated peak heart rate by 12 ± 2 bpm in women and 11 ± 1 bpm in men. There were 1868 patients (6%) who achieved the target heart rate using the sex-specific formulas but not with the traditional formula. Achievement of ≥85% MPHR was similarly associated with lower risk of death (adjusted hazard ratio = 0.76 [95% confidence interval = 0.60-0.97] vs 0.75 [0.62-0.90]) and MI (0.71 [0.47-1.06] vs 0.79 [0.57-1.10]) for the sex-specific versus traditional formula. CONCLUSIONS: In patients referred for exercise treadmill testing, sex-specific formulas more accurately estimated peak heart rate than the traditional MPHR formula, reclassified 6% of stress tests from inadequate to adequate, and were similarly associated with risk of MI and death.