Heart rate responses to deep breathing and 4-seconds of exercise before and after pharmacological blockade with atropine and propranolol

Abstract

Two autonomic tests which evaluate cardiac vagal activity, the respiratory sinus arrhythmia and the newer 4-second exercise test, have been compared. From electrocardiograph tracings, respiratory sinus arrhythmia was quantified by the ratio between the longest R-R interval during expiration and the shortest one during inspiration (E/I ratio), and the 4-second exercise test by the ratio between the last R-R interval before and the shortest one during exercise (B/C ratio). In 29 healthy subjects there was a correlation (R = 0.60, p less than 0.05) between the responses to the two tests. In a group of six healthy subjects the same tests were performed after autonomic blockade with intravenous atropine and/or propranolol. The heart rate rise during the 4-second exercise test was nearly abolished by atropine (mean +/- SD) (B/C: control = 1.53/0.33; after atropine = 1.04/0.03), whereas RSA was diminished to a lesser extent (E/I: control = 1.59/0.24; after atropine = 1.13/0.07). beta-adrenoceptor blockade did not affect the test ratios (after propranolol: B/C = 1.51/0.33 and E/I = 1.45/0.14). Successive tests during the following hour after atropine infusion showed a somewhat faster recovery of the respiratory sinus arrhythmia than the heart rate acceleration induced by the 4-second exercise test (p less than 0.05). We conclude that there may be some difference in the mechanisms which contribute to the heart rate changes in these two autonomic cardiovascular tests; these remain to be clarified. The 4-second exercise test may be an alternative to the respiratory sinus arrhythmia test in the non-invasive evaluation of cardiac parasympathetic activity.

Validação do teste de exercício de 4 segundos em posição ortostática

“…The 4sET is based on eliminating the vagal cardiac tonus in the first seconds of rapid exercise involving large muscle groups. The 4sET is a pharmacologically validated autonomic test, whose finality is the isolated analysis of the vagal modulation of heart rate in the initial transient of dynamic exercise 12 . Since it was reported, 4sET has been applied in the clinical area in some sports medicine and cardiology laboratories, in addition to being used as an instrument of scientific investigation in the research developed by our group 11,[13][14][15][16][17][18] and also by other research centers 19 .…”

Associação entre transientes inicial e final de frequência cardíaca no teste de exercício

“…In 1992, T4s was pharmacologically validated for the assessment of CVA, by means of analysis of the initial rapid transient HR response (rest-exercise transition) 20 . In short, T4s consists of pedaling an unloaded leg cycle ergometer (CatEye EC-1600, CatEye, Japan) as fast as possible, from the 4th to the 8th second of a 12-second inspiratory breath-hold.…”

Teste de sentar-levantar: apresentação de um procedimento para avaliação em Medicina do Exercício e do Esporte

“…Ao longo dos últimos anos, temos desenvolvido e proposto vários procedimentos para avaliação em Medicina do Exercí-cio e do Esporte 16,24,25 . O presente artigo apresenta um novo procedimento, correspondendo a uma proposta metodológica para avaliação simplificada e de rápida execução da aptidão muscular funcional mínima para a autonomia.…”