Sympathetic hyperactivity early after unstable angina (72 bursts/100 beats) and AMI (83 bursts/100 beats) was elevated compared to controls (51 bursts/100 beats), normalizing by 6 and 9 months.
Observational (n=57)
Does sympathetic neural hyperactivity occur and how does it normalize over time following unstable angina compared to acute myocardial infarction?
Sympathetic hyperactivity occurs after both unstable angina and acute myocardial infarction, but is less severe and normalizes faster (6 months vs 9 months) in unstable angina.
Impaired autonomic function occurs after AMI (acute myocardial infarction) and UA (unstable angina), which may be important prognostically. However, the pattern of sympathetic nerve hyperactivity has been investigated only after AMI. We aimed to quantify central sympathetic output to the periphery in patients with UA, investigate its progress over time relative to that after uncomplicated AMI and to explore the mechanisms involved. Muscle sympathetic nerve activity (MSNA) assessed from multiunit discharges and from single units (s-MSNA) was obtained in matched patients with UA ( n =9), AMI ( n =14) and stable CAD (coronary artery disease, n =11), patients with chest pain in which AMI was excluded (NMI, n =9) and normal controls (NCs, n =14). Measurements were obtained 2-4 days after UA or AMI, and repeated at 3 monthly intervals until they returned to normal levels. The respective MSNA and s-MSNA early after UA (72+/-4.0 bursts/100 beats and 78+/-4.2 impulses/100 beats respectively) were less than those after AMI (83+/-4.4 bursts/100 beats and 93+/-5.5 impulses/100 beats respectively). Relative to the control groups of NCs (51+/-2.7 bursts/100 beats and 58+/-3.4 impulses/100 beats respectively) and patients with CAD (54+/-3.7 bursts/100 beats and 58+/-3.9 impulses/100 beats respectively) and NMI (52+/-4.5 bursts/100 beats and 59+/-4.9 impulses/100 beats respectively), values returned to normal after 6 months in UA (55+/-5.0 bursts/100 beats and 62+/-5.5 impulses/100 beats respectively) and 9 months after AMI (60+/-3.8 bursts/100 beats and 66+/-4.2 impulses/100 beats respectively). In conclusion, both UA and AMI result in sympathetic hyper-activity, although this is of smaller magnitude in UA and is less protracted than in AMI. It is suggested that this hyperactivity is related to the degree of left ventricular dysfunction and reflexes.
Graham et al. (Tue,) conducted a observational in Unstable angina and acute myocardial infarction (n=57). Unstable angina and acute myocardial infarction vs. Stable CAD, non-myocardial infarction chest pain, and normal controls was evaluated on Muscle sympathetic nerve activity (MSNA) and single-unit MSNA (s-MSNA). Sympathetic hyperactivity early after unstable angina (72 bursts/100 beats) and AMI (83 bursts/100 beats) was elevated compared to controls (51 bursts/100 beats), normalizing by 6 and 9 months.