This study analyzed, with spectral techniques, the effects of atenolol or metroprolol on RR interval variability in 20 patients 4 weeks after the first uncomplicated myocardial infarction. Beta blocker-induced bradycardia was associated with a significant increase in the average 24 hour values of RR variance (from 13,886 ± 1,479 to 16,728 ± 1,891 ms2) and of the normalized power of the high-frequency component (from 22 ± 1 to 28 ± 2 normalized units), whereas the low-frequency component was greatly reduced (from 60 ± 3 to 50 ± 3 normalized units). When considering day and nighttime separately, the effects of both drugs were more pronounced in the daytime. In addition, a marked attenuation was observed in the circadian variation of the low-frequency component after β blockade. As a result, the early morning increase of the spectral index of sympathetic modulation was no longer detectable. These results indicate that β-blocker administration has important effects on RR interval variability and on its spectral components. The observed reduction in signs of sympathetic activation and the increase in vagal tone after β blockade help to explain the beneficial effects of these drugs after myocardial infarction. However, the potential clinical relevance of the increase in RR variance remains to be established.
|Titolo:||Effects of beta blockers (atenolol or metroprolol) on heart rate variability after acute myocardial infarction|
MALLIANI, ALBERTO (Penultimo)
LOMBARDI, FEDERICO (Ultimo)
|Settore Scientifico Disciplinare:||Settore MED/11 - Malattie dell'Apparato Cardiovascolare|
|Data di pubblicazione:||1994|
|Digital Object Identifier (DOI):||10.1016/0002-9149(94)90400-6|
|Appare nelle tipologie:||01 - Articolo su periodico|