Key result
In patients treated for acute myocardial infarction with left ventricular ejection fraction ≥40%, peak oxygen uptake was significantly correlated with peak arteriovenous oxygen difference (r = 0.68, p < 0.001) and percent predicted heart rate (r = 0.28, p = 0.01).
Why the study?
Exercise intolerance after acute myocardial infarction predicts worse prognosis, but its underlying causes are complex and poorly studied.
What are the determinants of exercise intolerance assessed by CPET-SE in patients treated for AMI with LVEF ≥40%?
Cross-Sectional (n=81)
No
What are the determinants of exercise intolerance assessed by CPET-SE in patients treated for AMI with LVEF ≥40%?
Effect estimate: r = 0.68
p-value: p=<0.001
Exercise capacity in post-AMI patients with LVEF ≥40% is primarily related to chronotropic response and peripheral oxygen extraction rather than peak stroke volume.
Peripheral factors and chronotropy may predominate in post-AMI exercise intolerance with LVEF ≥40%; hypothesis-generating for targeted interventions.
Exercise intolerance after acute myocardial infarction (AMI) is a predictor of worse prognosis, but its causes are complex and poorly studied. This study assessed the determinants of exercise intolerance using combined stress echocardiography and cardiopulmonary exercise testing (CPET-SE) in patients treated for AMI. We prospectively enrolled patients with left ventricular ejection fraction (LV EF) ≥40% for more than 4 weeks after the first AMI. Stroke volume, heart rate, and arteriovenous oxygen difference (A-VO2Diff) were assessed during symptom-limited CPET-SE. Patients were divided into four groups according to the percentage of predicted oxygen uptake (VO2) (Group 1, <50%; Group 2, 50-74%; Group 3, 75-99%; and Group 4, ≥100%). Among 81 patients (70% male, mean age 58 ± 11 years, 47% ST-segment elevation AMI) mean peak VO2 was 19.5 ± 5.4 mL/kg/min. A better exercise capacity was related to a higher percent predicted heart rate (Group 2 vs. Group 4, p <0.01), higher peak A-VO2Diff (Group 1 vs. Group 3, p <0.01) but without differences in stroke volume. Peak VO2 and percent predicted VO2 had a significant positive correlation with percent predicted heart rate at peak exercise (r = 0.28, p = 0.01 and r = 0.46, p < 0.001) and peak A-VO2Diff (r = 0.68, p <0.001 and r = 0.36, p = 0.001) but not with peak stroke volume. Exercise capacity in patients treated for AMI with LV EF ≥40% is related to heart rate response during exercise and peak peripheral oxygen extraction. CPET-SE enables non-invasive assessment of the mechanisms of exercise intolerance.
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Smarż et al. (2021) conducted a cross-sectional in Acute myocardial infarction (AMI) (n=81). Exercise capacity (percent predicted VO2) vs. Lower vs higher exercise capacity groups was evaluated on Correlation between peak oxygen uptake (VO2) and peak arteriovenous oxygen difference (A-VO2 Diff) (r = 0.68, p=<0.001). In patients treated for acute myocardial infarction with left ventricular ejection fraction ≥40%, peak oxygen uptake was significantly correlated with peak arteriovenous oxygen difference (r = 0.68, p < 0.001) and percent predicted heart rate (r = 0.28, p = 0.01).
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