OBJECTIVE: To test the operational viability of and validate the 4-second exercise test (4sET) protocol in the orthostatic position (ORTHO). METHODS: The ORTHO protocol, an alternative to the conventional protocol (CYCLO), was used. The ORTHO protocol consists of performing sudden exercise in the orthostatic position -- accelerated stationary walking (alternate upward flexion of the thighs) -- from the fourth to the eighth second of a 12-second maximum inspiratory apnea, instead of rapid cycling without load. The adimensional cardiac vagal index (CVI) was calculated using the ratio between the longest RR interval (RRB) -- the one immediately before, or the first during exercise -- and the shortest RR interval during exercise -- usually the last (RRC) -- measured on electrocardiographic tracings at a 10-ms resolution. Forty-seven individuals (40+/-17 years, 169+/-9 cm, 72+/-14 kg) of both sexes, healthy or unhealthy, randomly underwent 3 consecutive repetitions of the 2 protocols, the first being performed only to acquaint patients with the procedure. RESULTS: Although differences in the CVI were found in both protocols (1.48+/-0.04 vs 1.42+/-0.04; P<0.001), no physiological relevance was observed. In 5 (11%) cases, a clinically significant difference between the ORTHO and CYCLO protocols was observed for CVI. The results of RRB, RRC, and CVI in the 2 protocols were strongly correlated, being 0.84, 0.85, and 0.93, respectively (P<0.001). CONCLUSION: The 4sET performed in the orthostatic position proved to be a valid option for assessing the vagal cardiac tonus in laboratories lacking a cycloergometer, without jeopardizing clinical interpretation. In addition to simplicity and applicability, the procedure also provides low operational costs.
OBJECTIVE: To test the operational viability of and validate the 4-second exercise test (4sET) protocol in the orthostatic position (ORTHO). METHODS: The ORTHO protocol, an alternative to the conventional protocol (CYCLO), was used. The ORTHO protocol consists of performing sudden exercise in the orthostatic position -- accelerated stationary walking (alternate upward flexion of the thighs) -- from the fourth to the eighth second of a 12-second maximum inspiratory apnea, instead of rapid cycling without load. The adimensional cardiac vagal index (CVI) was calculated using the ratio between the longest RR interval (RRB) -- the one immediately before, or the first during exercise -- and the shortest RR interval during exercise -- usually the last (RRC) -- measured on electrocardiographic tracings at a 10-ms resolution. Forty-seven individuals (40+/-17 years, 169+/-9 cm, 72+/-14 kg) of both sexes, healthy or unhealthy, randomly underwent 3 consecutive repetitions of the 2 protocols, the first being performed only to acquaint patients with the procedure. RESULTS: Although differences in the CVI were found in both protocols (1.48+/-0.04 vs 1.42+/-0.04; P<0.001), no physiological relevance was observed. In 5 (11%) cases, a clinically significant difference between the ORTHO and CYCLO protocols was observed for CVI. The results of RRB, RRC, and CVI in the 2 protocols were strongly correlated, being 0.84, 0.85, and 0.93, respectively (P<0.001). CONCLUSION: The 4sET performed in the orthostatic position proved to be a valid option for assessing the vagal cardiac tonus in laboratories lacking a cycloergometer, without jeopardizing clinical interpretation. In addition to simplicity and applicability, the procedure also provides low operational costs.
Authors: Bruno M Silva; Lauro C Vianna; Ricardo B Oliveira; Djalma R Ricardo; Claudio Gil Soares Araújo Journal: Eur J Appl Physiol Date: 2007-12-18 Impact factor: 3.078
Authors: Claudio Gil Araújo; Claudia Lucia Barros de Castro; João Felipe Franca; Plínio Santos Ramos Journal: Arq Bras Cardiol Date: 2015-03-27 Impact factor: 2.000