Association between heart rate at rest and myocardial perfusion in patients with acute myocardial infarction undergoing cardiac rehabilitation - a pilot study

Introduction: This study was conducted to determine if there was a link among heart rate at rest (rHR), muscle volume changes, and single photon emission computed tomography (SPECT) parameters after 6-month cardiac rehabilitation in patients with acute myocardial infarction (AM)). Material and methods: Twenty-nine consecutive AMI patients (mean age: 63.0 +/- 9.1 years) who received appropriate percutaneous coronary intervention on admission were enrolled. Tc-99m-Sestamibi myocardial SPECT images were obtained at the early (30 min) and delayed (4 h) phases after tracer injection at 2 weeks (OM) and 6 months (6M) after the onset of AMI. Within a few days of SPECT, all patients underwent cardiopulmonary exercise test for evaluation of cardiac rehabilitation effects. Before the initiation of exercise test, leg muscle volume was measured. All patients were stratified into the >= 70 beats per minute (bpm) (n = 15) or <70 bpm (n = 14) group based on rHR at 6M. Results: There were no significant differences in the recanalization time, peak cardiac enzyme, or initial left ventricular ejection fraction between the two groups. After the 6-month training, the muscle volume changes in the lower limbs (<70 bpm, 0.23 +/- 0.22; >= 70 bpm, -0.07 +/- 0.26, p < 0.05) were significantly greater in the < 70 bpm group than the >= 70 bpm group. The decreased rate of rHR had a significant correlation with the improved global severity (r = 0.62, p = 0.001) and extent (r = 0.48, p = 0.017) of left ventricle evaluated by Tc-99m-Sestamibi myocardial SPECT delayed phase. Conclusions: The result of this preliminary study demonstrated that improved myocardial perfusion was closely related to decreased rHR after cardiac rehabilitation.