Adaptation to Low-Intensity Exercise on a Cycle Ergometer by Patients With Acute Myocardial Infarction Undergoing Phase I Cardiac Rehabilitation

BACKGROUND: The adaptation of patients with acute myocardial infarction (AMI) to a phase I rehabilitation program has not been widely assessed. METHODS AND RESULTS: Forty-two male patients (62+/-8 years) with AMI were classified as exercise tolerant (group A, n=25) or excessive response (systolic blood pressure (SBP) increase >30 mmHg during exercise; group B, n=17). Hemodynamic parameters during exercise using a cycle-ergometer were monitored for the first 3 days. The power of low- and high-frequency components (LF: 0.05-0.2 Hz; HF: 0.2-1 Hz) was analyzed by heart rate variability. Anxiety status was assessed using the Spielberger's State-Trait Anxiety Inventory. Patients in group B were significantly older, had lower cardiac function and a longer hospitalization than group A (p<0.05, respectively). The excessive elevation of SBP on Day 1 decreased and became <30 mmHg on Day 3 in group B. The decreases in HF during exercise on Days 1 and 3 were significantly smaller in group B than in group A (p<0.05 and p<0.05, respectively). The LF/HF ratio on Day 1 was significantly higher in group B than in group A (p<0.05). In group B, the anxiety score before exercise was significantly higher than that at the time of discharge (p<0.05), whereas there was no change in group A. CONCLUSION: Factors influencing a significant elevation of blood pressure during phase I rehabilitation are age, physical deconditioning, imbalance of autonomic nervous activity and anxiety.