Relationship Between Inspiratory Muscle Capacity and Peak Exercise Tolerance in Patients Post-myocardial Infarction

Objective: The study objective was to evaluate inspiratory muscle endurance in patients post-myocardial infarction without respiratory muscle weakness and its correlation with peak exercise capacity.

Methods: Ten patients who recently had a myocardial infarction (recent infarction group [RIG]), 9 patients who less recently had a myocardial infarction (less recent infarction group [LIG]), and 12 healthy subjects (control group [CG]) underwent a cardiopulmonary exercise test and respiratory endurance protocol. Analysis of variance with post hoc Dunn comparisons was used to contrast performances on all tests, and Pearson's correlation was used to determine associations between variables.

Results: The RIG presented lower maximal incremental pressure and oxygen consumption than the CG (P < .01). There was a positive correlation between peak oxygen uptake and both maximal inspiratory pressure (.68, P < .001) and maximal incremental pressure (.65, P < .001) in the RIG.

Conclusion: The RIG showed lower maximal incremental pressure, which is related to peak exercise capacity. This novel relationship in functional capacity can indicate the need to improve muscle endurance in these patients even in the absence of inspiratory muscle weakness.