Better Exercise Capacity Can Lessen Mortality From a First MI

Pam Harrison

February 09, 2016

BALTIMORE, MD — Patients with greater exercise capacity are at the lowest risk for early death associated with a first acute MI, suggests a retrospective analysis based on the longitudinal Henry Ford Exercise Testing Project (the FIT Project) cohort[1].

"With greater exercise capacity, not only do you have fewer heart attacks, but if you do have one, you are more likely to survive," according to senior author Dr Michael J Blaha (Johns Hopkins University, Baltimore, MD).

"We could hypothesize that fitness eliminates the small MIs. Patients still have the big ones, but this study suggests that fitness may be making the bigger MIs smaller," Blaha speculated for heartwire from Medscape.

Fitness may increase a patient's physiologic reserve so they suffer less permanent damage to the heart or, in this case, death, from the same magnitude of heart attack had they been less fit, according to Blaha. "I think who we are talking about here are people with an elevated risk for MI either from an early family history or in those with subclinical atherosclerosis," he said.

The analysis, published February 1, 2016 in Mayo Clinic Proceedings, with lead author Dr Gabriel Shaya (Johns Hopkins University), included a subset of the overall study cohort consisting of 2086 patients without a history of MI. At baseline, all patients underwent "routine, clinically referred, symptom-limited maximal treadmill stress testing following the standard Bruce protocol," according to the report.

Exercise capacity was categorized on the basis of peak metabolic equivalents (METs) achieved during a graded treadmill test of less than 6 METs; 6 to 9 METs; 10 to 11 METs; and 12 or more METs.

Early mortality was defined as all-cause mortality within 28, 90, or 365 days of the first acute MI, and the mean time from the exercise test to the MI was 6.1 years.

Overall, 10.6% of the cohort had died 28 days after their MI, as had 15.7% of the group by 90 days and 24.5% of the group at 365 days post-MI. However, the proportion of patients who experienced early mortality at all three time points steadily decreased as exercise capacity increased.

When investigators analyzed exercise capacity as a continuous variable, "each additional 1-MET increment in exercise capacity was associated with an 8% to 10% reduction in risk in early mortality after a first MI," Shaya and colleagues point out.

Unadjusted Proportion of Patients Who Experienced Early Mortality After Their MI Based on MET Category

Exercise capacity (METS) 28 d post-MI (%) 90 d post-MI (%) 365 d post-MI (%)
<6 13.9 21.8 33.4
6–9 10.7 15.9 24.4
10–11 6.9 8.8 14.4
≥12 6 6.6 12.6

"If patients ask me, 'What can I do to prevent what happened to my dad, who died of an MI at an early age?' I can now say to them, 'If you increase your fitness now before you have a heart attack, not only should you have fewer heart attacks, but should you have a heart attack, you are more likely to survive it and have less morbidity after it," Blaha said. "And patients are comforted knowing that they aren't condemned to the same fate as their family member who unfortunately had a sudden fatal heart attack."

The authors had no relevant financial relationships.

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