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Kinetics of cycle length dependence of ventricular repolarization: effect of autonomic blockadeINTRODUCTION: Beat-to-beat adaptation of ventricular repolarization duration to cardiac cycle length and autonomic activity has not been previously characterized in the spontaneously beating human heart. METHODS AND RESULTS: The ECG of 14 healthy subjects was recorded from the supine and upright positions. Autonomic blockade was accomplished by atropine and propranolol. RR and RT intervals were measured by a computer algorithm, and the impulse response (h) from RR to RT computed. In the supine position the maximal adjustment of the RT interval occurred in the first beat following a change in cycle length (hpeak = 17.8 +/- 1.6 msec/sec), but continued to be detectable for 3.8 seconds (2.9-4.7 sec). Propranolol attenuated the peak impulse response to 15.8 +/- 4.0 msec/sec (P = NS). In the standing position the peak impulse response was increased to 25.2 +/- 5.0 msec/sec (P = 0.004 vs supine), and the impulse response duration (hdur) shortened to 1.4 seconds (1.3-1.6). This was reversed by beta blockade (hpeak = 10.7 +/- 3.6 [P = 0.005 vs standing]; hdur = 5.5 sec [4.8-6.1]). Parasympathetic and combined autonomic blockade resulted in too little residual heart rate variability to estimate the impulse response accurately. The slope of the regression of delta RT and delta RR in the supine position was 0.0177 +/- 0.0016, which was closely correlated with the peak impulse response (r = 0.91). CONCLUSIONS: System identification techniques can assist in characterizing the cycle dependence of ventricular repolarization and may provide new insights into conditions associated with abnormal repolarization.
Document ID
20050000229
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Raeder, E. A.
(Health Sciences Center SUNY at Stony Brook 11794, United States)
Albrecht, P.
Perrott, M.
Cohen, R. J.
Date Acquired
August 22, 2013
Publication Date
March 1, 1995
Publication Information
Publication: Journal of cardiovascular electrophysiology
Volume: 6
Issue: 3
ISSN: 1045-3873
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Clinical Trial
NASA Discipline Regulatory Physiology
Non-NASA Center

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