Background: In the Systolic Heart Failure Treatment With the If Inhibitor Ivabradine Trial (SHIFT), heart rate (HR) reduction with ivabradine was associated with improved survival and reduced hospitalizations in patients with heart failure (HF). The mechanisms by which elevated HR increases mortality are not fully understood. Objective: To assess the relationship of baseline HR with clinical, neurohormonal and cardiac sympathetic activity in patients with chronic HF and elevated HR. Method: Patients with chronic HF who were in sinus rhythm and had resting HR>70 bpm despite optimal medical treatment were included in a randomized, double-blind study comparing ivabradine versus pyridostigmine. This report refers to the baseline data of 16 initial patients. Baseline HR (before randomization to one of the drugs) was assessed, and patients were classified into two groups, with HR below or above mean values. Cardiac sympathetic activity was assessed by 123-iodine-metaiodobenzylguanidine myocardial scintigraphy. Results: Mean HR was 83.5±11.5 bpm (range 72 to 104), and seven (43.7%) patients had HR above the mean. These patients had lower 6-min walk distance (292.3±93 vs 465.2±97.1 m, p=0.0029), higher values of N-Terminal-proBNP (median 708.4 vs 76.1, p=0.035) and lower late heart/mediastinum rate, indicating cardiac denervation (1.48±0.12 vs 1.74±0.09, p Conclusion: Elevated resting HR in patients with HF under optimal medical treatment was associated with cardiac denervation, worse functional capacity, and neurohormonal activation. Fundamento: No SHIFT (Systolic Heart Failure Treatment With the If Inhibitor Ivabradine Trial, ou Estudo do Tratamento da Insuficiencia Cardiaca Sistolica com o Inibidor de If Ivabradina), a reducao da frequencia cardiaca (FC) com ivabradina associou-se com melhor sobrevida e reducao das hospitalizacoes em pacientes com insuficiencia cardiaca (IC). Os mecanismos pelos quais a FC elevada aumenta a mortalidade nao sao totalmente compreendidos. Objetivo: Avaliar a relacao da FC basal com atividade clinica, neuro-hormonal e simpatica cardiaca em pacientes com IC cronica e FC elevada. Metodo: Pacientes com IC cronica em ritmo sinusal e FC≥70 apesar de tratamento adequado foram incluidos em um estudo duplo-cego, randomizado, que comparou ivabradina com piridostigmina. Este artigo refere-se a dados basais dos primeiros 16 pacientes. A FC basal (antes da randomizacao para um dos medicamentos) foi avaliada, e os pacientes classificados em dois grupos, com FC abaixo ou acima dos valores medios. A atividade simpatica cardiaca foi avaliada por cintilografia com metaiodobenzilguanidina marcada com iodo 123. Resultados: A FC media foi 83,5±11,5 bpm (intervalo 72 a 104), e sete pacientes (43.7%) tinham FC acima da media. Esses pacientes apresentaram menor distância percorrida no teste de caminhada de 6 minutos (292,3±93 vs 465,2±97,1 m, p=0,0029), valores mais altos de N-terminal do pro-BNP (mediana 708,4 vs 76,1, p=0,035) e menor relacao coracao/mediastino tardia, indicando desnervacao cardiaca (1,48±0,12 vs 1,74±0,09, p Conclusao: A FC de repouso elevada em pacientes com IC em tratamento medico adequado associou-se com desnervacao cardiaca, pior capacidade funcional e ativacao neuro-hormonal.