Alterations of first derivative of apexcardiogram indices during induced changes of heart rate.
The aim of this study is to investigate the effects of HR changes, induced by a variety of causes, on left ventricular performance as assessed by the first derivative of apexcardiogram indices. Ten males, mean age 29.6 +/- 8.1 years, without evidence of heart disease were studied. In all subjects tachycardia was induced by 1) administration of atropine (1 mg bolus IV), 2) administration of isoprenaline (0.5-0.25 micrograms/min IV) and 3) treadmill exercise test according to Bruce protocol. The blood pressure (BP) was determined before and every 60 sec during each test. Drawings of the first derivative of apexcardiogram were obtained before and at the peak of HR and the indices a/b, ef/ZN and b/ef were determined.


RESULTS
the increase of HR was similar (about 30% from baseline) in each test. Exercise test caused more pronounced increase of BP compared to the administration of isoprenaline while administration of atropine was not followed by significant changes of BP. Administration of isoprenaline caused similar but more vigorous alterations of the first derivative of apexcardiogram indices (significant increase of b/ef and decrease of a/b and ef/ZN indices) compared with the exercise test. Administration of atropine caused no significant changes of these indices.


CONCLUSIONS
in this study it was found that the effects of various causes of tachycardia on LV performance, as assessed by the indices studied, are not uniform; this may reflect different mechanisms involved in the induction of tachycardia by different causes. These results suggest that the alterations of the indices assessed in this study can detect dysfunction(s) of the LV; it is also possible that the type of alteration induced, could provide information regarding causal relationships of this impairment.
Boudonas
G
G
2nd Department of Internal Medicine, Aristotelian University of Thessaloniki, Hippokration Hospital, Greece.
Lefkos
N
N
Efthimiadis
A
A
Styliadis
I G
IG
Aroditis
K
K
D000328:Adult; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000502:physiology; D005080:Exercise Test; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D007702:Kinetocardiography; D008297:Male; D016277:Ventricular Function, Left / Q000502:physiology*
D001285:Atropine; D007545:Isoproterenol