Differing patterns of cardiac parasympathetic activity and their evolution in selected patients with a first myocardial infarction.
OBJECTIVE
The purpose of the study was to compare cardiac parasympathetic activity during the early and convalescent phases of acute anterior and inferior myocardial infarction.


BACKGROUND
Previous studies have shown that cardiac parasympathetic activity may vary with the site of infarction and that recovery may occur after infarction.


METHODS
Cardiac parasympathetic activity was measured from 24-h electrocardiograms by counting the number of times that successive RR intervals (counts) differed by > 50 ms. Recordings began within 12 h of admission and at 7, 42 and 140 days after acute myocardial infarction in 20 patients (mean age 57 +/- 7.9 years). All patients were treated with streptokinase, aspirin and oral beta-adrenergic blocking agents.


RESULTS
For the entire group, mean total 24-h RR counts increased from 592 (range 78 to 3,812) at 48 h to 648 (range 109 to 5,473) at 7 days, 1,145 (range 162 to 6,268) at 42 days and 1,958 (range 344 to 9,632) at 140 days. Patients with anterior infarction had significantly lower counts (mean 277, range 78 to 2,708; n = 11) compared with those with inferior infarction (mean 2,172, range 897 to 3,812; n = 9) at 48 h (p < 0.05). There was no significant difference in counts between patients with anterior (mean 1,051, range 212 to 6,268) and inferior (mean 1,321, range 162 to 3,265) infarction after 42 or after 140 days (anterior: mean 1,655, range 344 to 9,632; inferior: mean 2,588, range 1,700 to 5,767).


CONCLUSIONS
These data suggest that after anterior myocardial infarction there is impaired cardiac parasympathetic function that improves within 6 weeks, whereas in inferior infarction there is relative preservation of cardiac parasympathetic function.
Flapan
A D
AD
Department of Cardiology, Royal Infirmary, Edinburgh, Scotland.
Wright
R A
RA
Nolan
J
J
Neilson
J M
JM
Ewing
D J
DJ
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000294:innervation* / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology*; D013997:Time Factors; D014630:Vagus Nerve / Q000503:physiopathology*