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Response to exercise and mechanical efficiency in non‐ischaemic stunning, induced by short‐term rapid pacing in dogs: a role for calcium?
Author(s) -
De Pauw M.,
Mubagwa K.,
Hodeige D.,
Borgers M.,
Flameng W.,
Van de Voorde J.,
Heyndrickx G. R.
Publication year - 2017
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/apha.12629
Subject(s) - contractility , stunning , medicine , cardiology , myocardial stunning , inotrope , calcium , oxygen , vo2 max , fissipedia , chemistry , anesthesia , ischemia , heart rate , blood pressure , organic chemistry
Aim Rapid pacing ( RP ) is a regularly used model to induce heart failure in dogs. The aim of the study was to evaluate Ca 2+ handling, left ventricular ( LV ) contractile response during Ca 2+ administration compared to exercise, as well as oxygen consumption and mechanical efficiency after 48 h of RP . Methods Fifty‐three mongrel dogs were instrumented to measure LV pressure, LV fractional shortening, regional wall thickening and coronary blood flow. Contractile reserve was measured with isoproterenol and intravenous ( IV ) Ca 2+ administration. To assess the function of the sarcoplasmic reticulum ( SR ), post‐extrasystolic potentiation ( PESP ) and SR Ca 2+ uptake were measured. A graded treadmill test was performed in baseline and after RP ( n = 14). In a separate group of animals ( n = 5), myocardial performance and oxygen consumption were measured using a wide range of loading conditions. Results Left ventricular contractility was significantly decreased upon cessation of pacing. The contractile response to isoproterenol was blunted compared to a preserved response to IV Ca 2+ . Post‐extrasystolic potentiation was slightly increased after RP . Maximal velocity ( V max ) of SR Ca 2+ uptake was unchanged. Contractile response during exercise is attenuated after RP . External work is reduced, whereas oxygen consumption is preserved, provoking a reduced mechanical efficiency. Conclusion Forty‐eight‐hours RP provokes a reversible LV dysfunction, while the SR function and response to exogenous Ca 2+ are preserved. This is compatible with an intracellular functional remodelling to counteract Ca 2+ overload provoked by RP . Left ventricular dysfunction is accompanied by a reduced contractile reserve, but an unchanged oxygen consumption, illustrating an alteration in oxygen utilization.