Diurnal Variations of Neurocardiac Rhythms In Acute Myocardial Infarction Markad V. Kamath, PhD, and Ernest L. Fallen, MD
To determine the diurnal pattern of cardiac autonomic tone in acute myocardial infarction (AMI), this study examined the power spectrum of heart rate (HR) variability in 24 patients during a single 24-hour segment within 4 days of AMI. Patients were nonrandomly allocated to a group (n = 14) without autonomic drugs and to a group (n = 10) already receiving fl blockers at the time of AMI. Wth use of autoregressive modeling, the power spectrum of HR variability was computed from continuous l-hour electrocardiographic segments recorded at equally spaced intervals; 7 to 8 A.M., 3 to 4 P.M., and 11 to 12 P.M. All patients were supine, awake and pain free during recordings. There were no differences in HR, HR variance or the low-frequency peak power (0.06 to 0.1 Hz) from one temporal sequence to another. For the patients not taking /I blockers, the high-frequency peak power (0.2 to 0.36 Hz) or vagal component increased significantly from 3 ~.m.to 11 P.M. (28~t 11 to 45k20 beats/ min* - Hz-l, p 30 minutes) ischemic pain; electrocardioDecember 31, 1990;revisedmanuscript receivedMarch 14, 1991, and graphic changeswith typical evolution of pathologic Q acceptedMarch 17. waves or persistent symmetrical T-wave inversion or Address for reprints: Ernest L. Fallen, MD, McMaster University both; 22 successivesamplesof creatine kinase-MB levMedical Centre, 1200 Main St. W. Hamilton, Ontario, Canada L8N 325. els >lO% of a total creatine kinase >250 IU. Of the 24
CIRCADIAN RHYTHMS IN ACUTE MI 155
r
TABLE I Clinical And Demographic Data Without p Blockers (n = 14)
With p Blockers
(n = 10)
p Value
61 r 6.8 911
NS NS
10 04 1698 + 1097
6 2I 9882 777
NS NS
58%
35%
NS
13 1 78.2 f 11.3
10 I 0 59.5 f 7.5
NS
Age (years) Men/women Site of myocardial infarction
65 2 8.1 12/l
Inferior Non-Q-wave Anterior Peak creatine kinase (IU) Receivedthrombolytic therapy Killip class Iorll Ill or IV Heart rate (beats/min)
To determine the diurnal pattern of cardiac autonomic tone in acute myocardial infarction (AMI), this study examined the power spectrum of heart rate (HR) variability in 24 patients during a single 24-hour segment within 4 days of AMI. Patients were nonrandomly allocated to a group (n = 14) without autonomic drugs and to a group (n = 10) already receiving fl blockers at the time of AMI. Wth use of autoregressive modeling, the power spectrum of HR variability was computed from continuous l-hour electrocardiographic segments recorded at equally spaced intervals; 7 to 8 A.M., 3 to 4 P.M., and 11 to 12 P.M. All patients were supine, awake and pain free during recordings. There were no differences in HR, HR variance or the low-frequency peak power (0.06 to 0.1 Hz) from one temporal sequence to another. For the patients not taking /I blockers, the high-frequency peak power (0.2 to 0.36 Hz) or vagal component increased significantly from 3 ~.m.to 11 P.M. (28~t 11 to 45k20 beats/ min* - Hz-l, p 30 minutes) ischemic pain; electrocardioDecember 31, 1990;revisedmanuscript receivedMarch 14, 1991, and graphic changeswith typical evolution of pathologic Q acceptedMarch 17. waves or persistent symmetrical T-wave inversion or Address for reprints: Ernest L. Fallen, MD, McMaster University both; 22 successivesamplesof creatine kinase-MB levMedical Centre, 1200 Main St. W. Hamilton, Ontario, Canada L8N 325. els >lO% of a total creatine kinase >250 IU. Of the 24
CIRCADIAN RHYTHMS IN ACUTE MI 155
r
TABLE I Clinical And Demographic Data Without p Blockers (n = 14)
With p Blockers
(n = 10)
p Value
61 r 6.8 911
NS NS
10 04 1698 + 1097
6 2I 9882 777
NS NS
58%
35%
NS
13 1 78.2 f 11.3
10 I 0 59.5 f 7.5
NS
Age (years) Men/women Site of myocardial infarction
65 2 8.1 12/l
Inferior Non-Q-wave Anterior Peak creatine kinase (IU) Receivedthrombolytic therapy Killip class Iorll Ill or IV Heart rate (beats/min)
