Avaliação Cardiodinâmica Não Invasiva por Cardiografia de Impedância durante o Teste de Caminhada de Seis Minutos em Pacientes com Insuficiência Cardíaca / Non-Invasive Assessment of Cardiodynamics by Impedance Cardiography during the Six-Minute Walk Test in Patients with Heart Failure

Resumo Fundamento O Teste de Caminhada de seis Minutos (TC6M) é comumente usado para avaliar pacientes com insuficiência cardíaca. No entanto, vários fatores clínicos podem influenciar a distância percorrida pelos pacientes no teste. A cardiografia de impedância (CI) na avaliação morfológica é uma ferramenta útil para avaliar a hemodinâmica cardíaca de maneira não invasiva. Objetivo Este estudo teve como objetivo comparar as respostas de aceleração e desaceleração do Débito Cardíaco (DC), da Frequência Cardíaca (FC), e do Volume Sistólico (VS) ao TC6M de indivíduos com insuficiência cardíaca e fração de ejeção reduzida (ICFEr) com as de controles sadios. Métodos Este é um estudo transversal observacional. O DC, a FC, o VS e o Índice Cardíaco (IC) foram avaliados antes, durante e após o TC6M por CI. O nível de significância adotado na análise estatística foi 5%. Resultados Foram incluídos 27 participantes (13 com ICFEr e 14 controles sadios). A aceleração do DC e da FC foi significativamente diferente entre os grupos (p<0,01 e p=0,039, respectivamente). Encontramos diferenças significativas no VS, no DC e no IC entre os grupos (p<0,01). A regressão linear mostrou uma contribuição deficiente do VS à mudança no DC no grupo com ICFEr (22,9% versus 57,4%). Conclusão O principal resultado deste estudo foi o fato de que indivíduos com ICFEr apresentaram valores mais baixos de aceleração do DC e da FC durante o teste de exercício submáximo em comparação a controles sadios. Isso pode indicar um desequilíbrio na resposta autonômica ao exercício nessa condição.

Abstract Background The six-minute walk test (6MWT) is commonly used to evaluate heart failure (HF) patients. However, several clinical factors can influence the distance walked in the test. Signal-morphology impedance cardiography (SM-ICG) is a useful tool to noninvasively assess hemodynamics. Objective This study aimed to compare cardiac output (CO), heart rate (HR), and stroke volume (SV) acceleration and deceleration responses to 6MWT in individuals with HF and reduced ejection fraction (HFrEF) and healthy controls. Methods This is a cross-sectional observational study. CO, HR, SV and cardiac index (CI) were evaluated before, during, and after the 6MWT assessed by SM-ICG. The level of significance adopted in the statistical analysis was 5%. Results Twenty-seven participants were included (13 HFrEF and 14 healthy controls). CO and HR acceleration significantly differed between groups (p<0.01; p=0.039, respectively). We found significant differences in SV, CO and CI between groups (p<0.01). Linear regression showed an impaired SV contribution to CO change in HFrEF group (22.9% versus 57.4%). Conclusion The main finding of the study was that individuals with HFrEF showed lower CO and HR acceleration values during the submaximal exercise test compared to healthy controls. This may indicate an imbalance in the autonomic response to exercise in this condition.

Continuous Aerobic Training and High Intensity Interval Training Increase Exercise Tolerance in Heart Failure Patients: A Retrospective Study

Abstract Background: Conventional aerobic training is the first choice in cardiac rehabilitation for patients with chronic heart failure (CHF). However, high-intensity interval training (HIIT) may be an alternative, although it has little evidence. Objectives: To evaluate the effect of continuous aerobic training (CAT) or HIIT on exercise tolerance in CHF patients. Methods: Retrospective study with 30 patients, of both genders, members of a 10-week CAT or HIIT program. The control group (CON) consisted of patients who did not participate voluntarily in the program. Peak oxygen uptake (VO2peak), thresholds (LV1 and LV2), and ventilatory efficiency in the production of dioxide (VE/VCO2 slope), oxygen uptake efficiency (OUES), and VO2 recovery kinetics were analyzed. A two-way or repeated measures ANOVA was used, followed by Fisher's post-hoc test (p<0.05). Results: After 10 weeks of training, the CAT group increased the treadmill speed at LV1 (p=0.040), while the HIIT increased both the speed (p=0.030) and incline of the treadmill (p<0.001) for VO2peak and LV2, as well as the total time of the cardiopulmonary test. The VE/VCO2 slope was lower than that predicted for CAT (p=0.003) and HIIT (p=0.008). There was no change in VO2peak, recovery of heart rate (HR), and VO2, VE/VCO2, and OUES in both groups. Conclusions: After 10 weeks, both CAT and HIIT increased the tolerance to physical exercise. However, HIIT showed improvement in more parameters, differently from CAT.