Cardiopulmonary exercise testing in the early-phase of myocardial infarction

To evaluate and to compare the cardiorespiratory and metabolic variables at the ventilatory anaerobic threshold level (AT) and at submaximal cardiopulmonary exercise testing (CPET) in both, healthy volunteers and in patients in the early phase after acute myocardial infarction (AMI).

Twenty-six volunteers underwent a submaximal or symptom-limited cardiopulmonary exercise testing (CPET) on a cycle ergometer and were divided into AMI group (AMIG=12, 56.33±8.65 years) and healthy group (CG=14, 53.33±3.28 years). The primary outcome measures were the cardiorespiratory and metabolic variables obtained at the peak workload and at the AT of the CPET. Statistical test: independent Student's t-test, α=5%.

The AMIG presented lower values at the AT and the peak workload of the CPET compered to the CG: power in watts (91.06±30.10 and 64.88±19.92; 154.93±34.65 and 120.40±29.60); VO2 mL.kg-1.min-1 (17.26±2.71 and 12.19±2.51; 25.39±5.73 and 19.41±5.63); VCO2 L/min-1 (1.43±0.31 and 0.93±0.23; 2.07±0.43 and 1.42±0.36), VO2 L/min-1 (1.33±0.32 and 1.00±0.23; 1.97±0.39 and 1.49±0.36); VE L/min-1 (42.13±8.32 and 27.51±5.86; 63.07±20.83 and 40.82±11.96); HR (bpm) (122.96±14.02 and 103.46±13.38; 149.67±13.77 and 127.60±10.04), double product (DP) (bpm.mmHg.min-1) (21835.86±3245.93 and 17333.25±2716.51; 27302.33±3053.08 and 21864.00±2051.48), respectively. The variable oxygen uptake efficiency slope (OUES L/min) was lower in the AMIG (1.79±0.51) than the CG (2.26±0.37). The AMIG presented neither ECG alterations nor symptoms that limited the CPET.

The results suggest that patients with AMI Killip class I presented lower functional capacity and DP compared to the CG without presenting ischemic alterations. Thus, the study suggests that submaximal CPET can be applied at an early stage to evaluate cardiorespiratory status since it is both safe and highly sensitive to detect changes.