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Mechanical restitution curves reflect post-ischemic stunning in pigs
Knut E Kjørstad1, Dag Ole Nordhaug, Christian Korvald
1Department of Cardiothoracic and Vascular Surgery, University Hospital North Norway, Tromsø, Norway. knutck@fagmed.uit.no
Scandinavian Cardiovascular Journal : SCJ
|August 16, 2005
Summary
The time constant of mechanical restitution (T(MRC)) increased in pigs with stunned left ventricles (LV), suggesting T(MRC) can identify reversible LV dysfunction after ischemia. This may serve as a clinical LV performance index.
Area of Science:
- Cardiovascular Physiology
- Cardiac Mechanics
- Myocardial Stunning
Background:
- The time constant of mechanical restitution (T(MRC)) is linked to calcium handling and increases in left ventricular (LV) failure.
- Its utility in identifying transient LV dysfunction, or stunning, remains largely unexplored.
Purpose of the Study:
- To investigate if T(MRC) can detect post-ischemic, reversible LV dysfunction (stunning).
Main Methods:
- Myocardial stunning was induced in pigs via coronary artery occlusions.
- Left ventricular pressure-volume loops were measured using a pressure-volume catheter.
- Mechanical restitution curves (MRCs) were analyzed using maximal first derivative of pressure (CR(dP/dtmax)) and stroke work (CR(SW)) as contractile response measures.
Main Results:
- Following stunning, mean arterial pressure, stroke volume, and dP/dtmax decreased.
- MRCs derived from CR(dP/dtmax) showed an increased T(MRC) in all animals.
- MRCs derived from CR(SW) demonstrated an increased T(MRC) in seven out of eight animals.
Conclusions:
- Ischemia-reperfusion significantly alters MRCs, as reflected by changes in T(MRC).
- The MRC concept shows promise as a clinical index for assessing left ventricular performance, particularly in cases of stunning.