Muscarinic antibodies and heart rate responses to dynamic exercise and to the Valsalva maneuver in chronic chagasic patients / Anticorpos muscarínicos e resposta da frequência cardíaca ao exercício dinâmico e a manobra de Valsalva na doença de Chagas crônica

We have studied the cardiac chronotropic responses to the Valsalva maneuver and to dynamic exercise of twenty chronic chagasic patients with normal left ventricular function and no segmental wall abnormalities by two-dimensional echocardiogram. The absolute increase in heart rate of the patients (Δ = 21.5 ± 10 bpm, M±SD) during the maneuver was significantly diminished when compared to controls (Δ = 31.30 ± 70, M±SD, p = 0.03). The minimum heart rate (58.24 ± 8.90 vs. 62.80 ± 10, p = 0.68) and the absolute decrease in heart rate at the end of the maneuver (Δ = 38.30 ± 13 vs. Δ = 31.47 ± 17, p = 0.10) were not different from controls. The initial heart rate acceleration during dynamic exercise (Δ = 12 ± 7.55 vs. Δ = 19 ± 7.27, M±SD, p = 0.01) was also diminished, but the heart rate recovery during the first ten seconds was more prominent in the sero-positive patients (Median: 14, Interquartile range: (9.75-17.50 vs. 5(0-8.75, p = 0.001). The serum levels of muscarinic cardiac auto-antibodies were significantly higher in the chagasic patients (Median: 34.58, Interquartile Range: 17-46.5, Optical Density) than in controls (Median: 0, Interquartile Range: 0-22.25, p = 0.001) and correlated significantly and directly (r = 0.68, p = 0.002) with early heart rate recovery during dynamic exercise. The results of this investigation indirectly suggest that, the cardiac muscarinic auto-antibodies may have positive agonist effects on parasympathetic heart rate control of chagasic patients.

Foram estudadas as respostas cronotrópicas cardíacas à manobra de Valsalva e ao exercício dinâmico de vinte pacientes chagásicos com função ventricular esquerda normal e sem alterações da contractilidade segmentar por ecocardiografia bidimensional. O aumento absoluto da frequência cardíaca dos pacientes (Δ = 21,5 ± 10 bpm, M ± DP) durante a manobra de Valsalva foi significativamente menor quando se comparava ao grupo controle (Δ = 31,30 ± 70, p = 0,03). A frequência cardíaca mínima (58,24 ± 8,90 vs 62,80 ± 10, p = 0,68) e a diminuição da frequência cardíaca absoluta no final da manobra (Δ = 38,30 ± 13 vs Δ = 31,47 ± 17, p = 0,10) não foram diferentes em comparação com o grupo controle. A aceleração inicial da frequência cardíaca durante o exercício dinâmico (Δ = 12 ± 7,55 vs Δ = 19 ± 7,27, p = 0,01) também foi menor, mas a recuperação da frequência cardíaca, durante os primeiros dez segundos, foi maior no grupo sero-positivos [mediana:14 (intervalo interquartil: 9,75-17,50) vs 5 (0 - 8,75), p = 0,001]. Os níveis séricos de auto-anticorpos muscarínicos cardíacos foram significativamente maiores nos pacientes chagásicos do que no grupo controle [(mediana: 34,58 densidade óptica (intervalo interquartil 17 - 46,5) vs (mediana: 0, intervalo interquartil 0 - 22,25) p = 0,001] e a correlação é significativa e direta (r = 0,68, p = 0,002) com o início da recuperação da frequência cardíaca durante o exercício dinâmico. Os resultados desta investigação sugerem que indiretamente, os auto-anticorpos muscarínicos cardíacos, podem ter ação agonista positiva sobre o controle parassimpático da frequência cardíaca dos pacientes chagásicos.

Muscarinic antibodies and heart rate responses to dynamic exercise and to the Valsalva maneuver in chronic chagasic patients.

We have studied the cardiac chronotropic responses to the Valsalva maneuver and to dynamic exercise of twenty chronic chagasic patients with normal left ventricular function and no segmental wall abnormalities by two-dimensional echocardiogram. The absolute increase in heart rate of the patients (Δ = 21.5 ± 10 bpm, M±SD) during the maneuver was significantly diminished when compared to controls (Δ = 31.30 ± 70, M±SD, p = 0.03). The minimum heart rate (58.24 ± 8.90 vs. 62.80 ± 10, p = 0.68) and the absolute decrease in heart rate at the end of the maneuver (Δ = 38.30 ± 13 vs. Δ = 31.47 ± 17, p = 0.10) were not different from controls. The initial heart rate acceleration during dynamic exercise (Δ = 12 ± 7.55 vs. Δ = 19 ± 7.27, M±SD, p = 0.01) was also diminished, but the heart rate recovery during the first ten seconds was more prominent in the sero-positive patients (Median: 14, Interquartile range: (9.75-17.50 vs. 5(0-8.75, p = 0.001). The serum levels of muscarinic cardiac auto-antibodies were significantly higher in the chagasic patients (Median: 34.58, Interquartile Range: 17-46.5, Optical Density) than in controls (Median: 0, Interquartile Range: 0-22.25, p = 0.001) and correlated significantly and directly (r = 0.68, p = 0.002) with early heart rate recovery during dynamic exercise. The results of this investigation indirectly suggest that, the cardiac muscarinic auto-antibodies may have positive agonist effects on parasympathetic heart rate control of chagasic patients.

Mechanisms of neurohormonal activation in chronic congestive heart failure: pathophysiology and therapeutic implications.

Patients with chronic congestive heart failure have a sequential and incessant activation of those neurohormonal systems, which control body fluids, cardiac output and systemic blood pressure. Neurohormonal activation is initially selective and regional. Generalized activation is a late event in the natural history of congestive heart failure. Although the ultimate stimulus responsible for the activation of these neurohormonal systems is unknown, a decreased cardiac output and diminished effective blood volume have been proposed as the responsible mechanisms. However, extensive clinical and experimental research suggest that cardiac remodeling and loading of low-pressure cardiac receptors with sympathetic afferents could be the triggering events followed by unloading of high-pressure carotid receptors by decreased cardiac output and diminished effective blood volume.