Claudia Lucia Barros de Castro

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

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 < 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). β-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 < 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.

Acurácia de critérios para vagotonia no eletrocardiograma de repouso de 12 derivações: uma análise com curvas ROC

Accuracy of vagotonia criteria in the 12-lead resting electrocardiogram: analysis with ROC curves Objective: To determine sensitivity (Sens), specificity (Spec), positive (PPV) and negative (NPV) predictive value, and accuracy of different electrocardiographic criteria for vagotonia. Methods: Seventy-four Olympic athletes (51 male and 23 female; age = 24 ± 5 years) underwent an evaluation consisting of a 12-lead resting electrocardiogram (ECG), and an assessment of cardiac vagal tone () by the 4-second cycling exercise testing (4-s ET), with the B/C index utilized as the gold standard. The 4-s ET is a wellRESUMO Objetivo: Determinar a sensibilidade, a especificidade, os valores preditivos positivo e negativo e a acuracia de diferentes criterios eletrocardiograficos para vagotonia. Metodos: Foram avaliados 74 atletas olimpicos brasileiros (51 homens e 23 mulheres) com idade entre 16 e 42 anos (24 ± 5 anos), tendo sido realizados, entre outros exames, um ECG de repouso de 12 derivacoes e uma avaliacao do tonus vagal cardiaco (TVC) pelo teste de exercicio sem carga de quatro segundos (T4s), cujo indice B/C (indicativo da magnitude do TVC) foi utilizado como padrao-ouro. O T4s e um teste que se baseia no mecanismo da taquicardia inicial do exercicio e foi anteriormente padronizado e validado como capaz de avaliar o TVC sem influencia do componente simpatico. Dados de 10 atletas foram excluidos devido a presenca de criterios ecocardiograficos para hipertrofia ventricular esquerda, ainda que provavelmente fisiologica. Com o auxilio de curvas ROC (receiver operating characteristic), selecionou-se o ponto de corte com a melhor combinacao entre sensibilidade (Sens) e especificidade (Esp) para cada variavel do ECG, calculando-se os

Evaluating cardiac vagal activity on a conventional electrocardiogram.

OBJECTIVE To determine the viability of using a conventional electrocardiogram (ECG) tracing for assessment of CVA. METHODS We retrospectively analyzed 1395 individuals (995 males), aged 46 +/- 17.2 years (mean +/- standard deviation) with conventional ECG tracings to measure the delta RR (which represents the difference in milliseconds (ms) between the greatest and smallest RR interval) and results of a second autonomic parasympathetic evaluation, the 4-second exercise test (T4s), that quantifies CVA by the cardiac vagal index (CVI). ROC curves were obtained to determine the values of Delta RR for a closer correlation with sensitivity and specificity for 1.20 and 1.95 ms, the low and high CVA cutoff points, respectively. RESULTS The delta RR levels correlated significantly with those of the CVI (r=0.40; p<0.001). We identified < or = 60 and > or = 120 ms as the best cutoff points for low and high CVA. Sensitivity was 75% and 57%, specificity was 62% and 79%, and the areas of the ROC curves were 0.76 and 0.74, respectively. CONCLUSION The visual measurement of delta RR on an ECG tracing seems to be a valid quick preliminary clinical evaluation of CVA and can be useful in medical offices, emergency units, or situations in which the use of more sophisticated methods may not be feasible, appropriate, or convenient.

4-Second Exercise Test: Reference Values for Ages 18-81 Years.

Background Physiological reflexes modulated primarily by the vagus nerve allow the heart to decelerate and accelerate rapidly after a deep inspiration followed by rapid movement of the limbs. This is the physiological and pharmacologically validated basis for the 4-s exercise test (4sET) used to assess the vagal modulation of cardiac chronotropism. Objective To present reference data for 4sET in healthy adults. Methods After applying strict clinical inclusion/exclusion criteria, 1,605 healthy adults (61% men) aged between 18 and 81 years subjected to 4sET were evaluated between 1994 and 2014. Using 4sET, the cardiac vagal index (CVI) was obtained by calculating the ratio between the duration of two RR intervals in the electrocardiogram: 1) after a 4-s rapid and deep breath and immediately before pedaling and 2) at the end of a rapid and resistance-free 4-s pedaling exercise. Results CVI varied inversely with age (r = -0.33, p < 0.01), and the intercepts and slopes of the linear regressions between CVI and age were similar for men and women (p > 0.05). Considering the heteroscedasticity and the asymmetry of the distribution of the CVI values according to age, we chose to express the reference values in percentiles for eight age groups (years): 18–30, 31–40, 41–45, 46–50, 51–55, 56–60, 61–65, and 66+, obtaining progressively lower median CVI values ranging from 1.63 to 1.24. Conclusion The availability of CVI percentiles for different age groups should promote the clinical use of 4sET, which is a simple and safe procedure for the evaluation of vagal modulation of cardiac chronotropism.

Cardiorespiratory Optimal Point in Professional Soccer Players: A Novel Submaximal Variable During Exercise

Mailing Address: Christina Grüne de Souza e Silva Rua Professor Rodolpho Paulo Rocco, 255 8o andar Cidade Universitária, Campus do Fundão. Postal Code: 21941-913, Rio de Janeiro, RJ Brazil. E-mail: christina.g.dss@gmail.com Cardiorespiratory Optimal Point in Professional Soccer Players: A Novel Submaximal Variable During Exercise Christina Grüne de Souza e Silva,1,2 Claudia Lucia Barros de Castro,3 João Felipe Franca,3 Altamiro Bottino,4 Jonathan Myers,2 Claudio Gil Soares de Araújo3 Instituto do Coração Edson Saad, Universidade Federal do Rio de Janeiro,1 Rio de Janeiro, RJ Brazil Veterans Affairs Palo Alto Health Care System/Stanford University,2 Palo Alto, California USA Clínica de Medicina do Exercício, CLINIMEX,3 Rio de Janeiro, RJ Brazil São Paulo Futebol Clube,4 São Paulo, SP Brazil

Aerobic Exercise and The Heart: Discussing Doses

The recent and exciting images of the 2016 Olympic and Paralympic Games in Rio will be forever imprinted in our minds. Hundreds of world, Olympic, continental and national records were conquered with a combination of discipline, resilience, competitiveness and overcoming challenges. Overcoming them in every sense – a result of thousands of hours of training that ensure exceptional aerobic performance from athletes with powerful and extremely healthy hearts. The theme of aerobic exercise and the heart has never been so in evidence. Thus, in the perspective of this Olympic legacy, it is very appropriate to address the relation between aerobic exercise and the heart in the Brazilian Archives of Cardiology. More specifically, it is important to discuss the most suitable posology or dosage of exercise for adults in the context of primary and secondary prevention of cardiovascular diseases. Succinctly, the objective of this viewpoint to discuss and delimit the therapeutic range of the aerobic exercise dose for the heart and make suggestions about how this dose can be individualized according to certain criteria and objectives.