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Effects of posture on cardiac autonomic nervous activity in patients with congestive heart failure

Shoichi Miyamoto, MD^*, Masatoshi Fujita, MD, FACC, Hiroyuki Sekiguchi, PhD, Yoshiaki Okano, MD, Noritoshi Nagaya, MD^||, Kinzo Ueda, MD^*, Shun-ichi Tamaki, MD^*, Ryuji Nohara, MD^¶, Shigeru Eiho, PhD and Shigetake Sasayama, MD, FACC^¶

^* Division of Cardiology, Takeda Hospital, Kyoto, Japan
College of Medical Technology, Kyoto University, Kyoto, Japan
Department of Systems Science, Graduate School of Informatics, Kyoto University, Kyoto, Japan
Clinical Laboratory Medicine, Kyoto University Hospital, Kyoto, Japan
^|| Division of Cardiology, National Cardiovascular Center, Osaka, Japan
^¶ Department of Cardiovascular Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan

View larger version (28K): [in a new window]   Figure 1 (Upper panel) The placement of the tilt switches in the sensor unit. Four tilt switches are placed inside the box. The two switches (HL, HR) are used to detect the recumbent positions. When the body turns sideways more than 30 degrees, one of these switches turns on. Consequently, it changes the frequency of the oscillator output. Another pair of switches (VL, VR) can be used to detect whether the patient is standing or not. In the case of standing (or lying in the prone position), both switches turn off; as a result, the oscillator is stopped. (Lower panel) An example of the recorded waves. The output voltage of the pulse is 3 mV peak-to-peak, with the frequency selectable between 0.5, 1, and 2 Hz depending on the combination of the status of the tilt switches. Each frequency of 0.5, 1, and 2 Hz corresponds to the left lateral decubitus position, supine position, and right lateral decubitus position, respectively.

View larger version (24K): [in a new window]   Figure 2 (a) Representative power spectra of RR intervals during various recumbent positions in a normal subject and (b) a patient with CHF. In the normal subject, there were no significant differences in the normalized high-frequency power among the three recumbent positions. In contrast, in the patient with CHF, normalized high-frequency power was highest when the right lateral decubitus position was obtained, followed in decreasing order by the supine and left lateral decubitus positions. HF/total power = normalized high-frequency power; LF/total power = normalized low-frequency power; LF/HF = low-frequency/high-frequency power.