Key result
Ischemia-reperfusion induced stunning increased the time constant of mechanical restitution based on maximal first derivative of pressure in all 8 pigs.
Why the study?
Does the time constant of mechanical restitution (T(MRC)) identify post-ischemic, reversible LV dysfunction (stunning) in a porcine model?
Does the time constant of mechanical restitution (T(MRC)) identify post-ischemic, reversible LV dysfunction (stunning) in a porcine model?
The time constant of mechanical restitution increases during post-ischemic stunning, suggesting its potential utility as an index of left ventricular performance.
Answers are grounded in this paper and cite their sources.
T(MRC) detects stunning in pigs; leaves open clinical LV performance index utility pending human studies.
OBJECTIVES: The time constant of mechanical restitution (T(MRC)), proposed to reflect changes in calcium release and uptake, has been shown to increase in left ventricular (LV) failure. In this study, we tested the hypothesis that T(MRC) also can identify post-ischemic, reversible LV dysfunction (stunning). DESIGN: Stunning was induced by a series of left main coronary artery occlusions in eight anesthetized open chest pigs. Left ventricular pressure-volume relations were assessed using a pressure-volume catheter during right atrial pacing. Mechanical restitution curves (MRCs) were constructed using two different measures of contractile response: maximal first derivative of pressure (CR(dP/dtmax)) and stroke work (CR(SW)). RESULTS: Mean arterial pressure, stroke volume and dP/dtmax were decreased 30 min after stunning. Slopes of end-systolic pressure volume relation and preload recruitable stroke work, however, showed no significant changes after stunning. For MRCs based on CR(dP/dtmax), T(MRC) increased in all eight animals. Using CR(SW), T(MRC) increased in seven out of eight pigs. CONCLUSIONS: Ischemia-reperfusion induce changes in MRCs based on CR(dP/dtmax), and CR(SW). The MRC concept may have potential as a clinical left ventricular performance index.
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Kjørstad et al. (2005) studied Post-ischemic left ventricular dysfunction (stunning) (n=8). Left main coronary artery occlusions (ischemia-reperfusion) vs. Baseline (pre-stunning) was evaluated on Time constant of mechanical restitution (T(MRC)). Ischemia-reperfusion induced stunning increased the time constant of mechanical restitution based on maximal first derivative of pressure in all 8 pigs.
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