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Cardiac Output Versus Pacing Rate at Rest and with Exercise in Dogs with AV Block
Author(s) -
WESSALE JERRY L.,
GEDDES LESLIE A.,
FEARNOT NEAL E.,
JANAS WOLFGANG,
GROTE LEE
Publication year - 1988
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.1988.tb04553.x
Subject(s) - medicine , cardiology , heart rate , treadmill , cardiac output , cardiac pacing , impedance cardiography , rest (music) , hemodynamics , blood pressure , stroke volume
To achieve maximum benefit from exercise (rate)‐responsive pacing in subjects with sinus node dysfunction and AV block, it is necessary to determine the pacing rate (HR) which produces maximum cardiac output (CO) under specified exercise conditions. However, the CO‐HR relationship for exercise has not been systematically investigated. To permit determination of the optimum HR, CO was measured at rest and with exercise for different pacing rates. Seven dogs with complete AV block and permanently implanted ventricular pacemakers were exercised on a treadmill for 5 min at each of our pacing rates (55, 76. 101, 116/min) and at two constant exercise levels (225 and 560 kg‐m/min). CO was determined by impedance cardiography during the resting state preceding exercise and during a brie/period (10–20 s) immediately after exercise, and was expressed as a percent of the CO determined at rest with HR ‐ 55/min. A three‐phase pattern of CO versus HH appears of exist for exercise as for rest. For exercise, starting from a low HR, CO increases markedly; a “plateau” is reached during which moderate increase in CO is achieved by increasing HR. At very rapid pacing rates, CO may actually decrease with further increase in HR. The results of this study suggest that a subject‐specific optimum HR exists for each constant exercise level. Moreover, the methodology employed in the study is applicable to the identification of optimum HR for any exercise (rate)‐responsive pacemaker.