Asunto(s)
Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Insuficiencia Cardíaca , Volumen Sistólico , Chile/epidemiología , Ecocardiografía Doppler , Métodos Epidemiológicos , Insuficiencia Cardíaca/epidemiología , Insuficiencia Cardíaca/etiología , Insuficiencia Cardíaca/fisiopatología , Hospitalización , Hipertensión/complicaciones , Hipertensión/epidemiología , Hipertensión/fisiopatología , Distribución por Sexo , Volumen Sistólico/fisiologíaRESUMEN
BACKGROUND AND AIM OF THE STUDY: Autonomic dysfunction may be a risk factor for the generation of arrhythmias and sudden death in patients with severe aortic stenosis; thus, patients with this condition were studied to assess cardiac autonomic function. METHODS: Twelve patients (five males, seven females; mean age 63 +/- 13 years) with severe symptomatic aortic stenosis before and after aortic valve replacement, were compared with a control group matched by age and sex. In the study group, mean fractional shortening was 36.5 +/- 5% and maximal aortic gradient 94.7 +/- 12 mmHg, assessed echocardiographically. Autonomic dysfunction was evaluated by following heart rate variability in both time and frequency domains. Spectral analysis was assessed at very low frequency (VLF: 0.017-0.05 Hz), low frequency (LF: 0.05-0.15 Hz) and high frequency (HF: 0.15-0.50 Hz). Heart rate variability was analyzed during three intervals, between 6:00-8:00 am (morning), 14:00-16:00 (afternoon) and 02:00-04:00 (night), and re-evaluated at 8-10 months after aortic valve replacement. RESULTS: Compared with controls, patients with aortic stenosis presented a significantly lower heart rate variability in the morning and afternoon, analyzed either by time or frequency domain: 50 +/- 22 versus 132 +/- 52 ms (p < 0.05); VLF 5.0 +/- 1.5 versus 7.9 +/- 1.4 ln (ms)2 (p < 0.05); LF 4.9 +/- 1.7 versus 7.5 +/- 1.8 ln (ms)2 (p < 0.05); HF 5.3 +/- 1.4 versus 7.5 +/- 1.8 ln (ms)2 (p < 0.05). Results at night showed a similar tendency, but were not statistically significantly different. At 8-10 months after aortic valve replacement, heart rate variability was increased significantly during the morning, from 50 +/- 22 to 79.5 +/- 22 ms (p < 0.05); VLF from 5.0 +/- 1.5 to 6.7 +/- 0.8 ln (ms)2 (p < 0.05); LF from 4.9 +/- 1.7 to 6.2 +/- 1.3 ln (ms)2 (p < 0.05). HF values tended to increase, though not significantly so. During the remainder of the day there was also a non-statistically significant increment in all values of heart rate variability. CONCLUSIONS: The study results suggest that patients with severe symptomatic aortic stenosis present with autonomic dysfunction that tends to normalize within the first year of valve replacement.
Asunto(s)
Estenosis de la Válvula Aórtica/fisiopatología , Ritmo Circadiano/fisiología , Frecuencia Cardíaca/fisiología , Estenosis de la Válvula Aórtica/diagnóstico por imagen , Estenosis de la Válvula Aórtica/cirugía , Sistema Nervioso Autónomo/fisiopatología , Electrocardiografía Ambulatoria , Femenino , Estudios de Seguimiento , Corazón/inervación , Corazón/fisiopatología , Implantación de Prótesis de Válvulas Cardíacas , Humanos , Masculino , Persona de Mediana Edad , Pronóstico , UltrasonografíaRESUMEN
The analysis of heart rate variability studies the normal oscillatory changes of the cardiac cycle. These changes are periodical or incidental and are controlled by humoral, sympathetic and parasympathetic stimuli. Frequency domain and time domain are the methods most used to assess heart rate variability. Time domain analyses variations of cardiac cycle using the standard deviation of RR intervals in 24 hours (SDRR) and the percentage of difference between adjacent normal RR intervals of more than 50 ms (pNN50). Frequency domain, converts beat to beat fluctuation of heart rate into different components of frequency by a fast Fourier transformation. They are classified, according to their magnitude, in high frequency (> 0.15 Hz), low frequency (0.04-0.15 Hz), very low frequency (0.003-0.04 Hz) and extremely low frequency (< 0.003 Hz). The high frequency fluctuations are predominantly related to parasympathetic activity whereas the low frequency fluctuations are related to sympathetic and parasympathetic activity. The physiology of very low and extremely low frequency fluctuations remains unclear. Many reports have shown that a decrease in heart rate variability after myocardial infarction may independently identify patients at risk for sudden death. However, the physiopathologic basis of these findings is not yet elucidated.