Background: Myocardial ischemic contracture compromises the hemodynamic effectiveness of cardiopulmonary resuscitation (CPR). Its most severe form, referred to as stone heart, is considered to be beyond the limit of resuscitation. However, accurate assessment of the ischemic contracture severity is challenging during CPR. We investigated, in a swine model, whether hemodynamic parameters, including end-tidal carbon dioxide (ETCO2), are predictive of the ischemic contracture severity during consistent quality CPR.
Methods: We retrospectively analyzed 96 datasets for ETCO2, arterial pressure, left ventricular (LV) wall thickness, and the percent of measured end-diastolic volume (%EDV) relative to EDV at the onset of ventricular fibrillation from eight pigs. Animals underwent advanced cardiovascular life support based on resuscitation guidelines.
Results: During CPR, LV wall thickness progressively increased while %EDV progressively decreased. Systolic and diastolic arterial pressure and ETCO2 were significantly correlated with LV wall thickness and %EDV. Linear mixed effect models revealed that, after adjustment for baseline covariates, systolic and diastolic arterial pressure were not predictive factors for LV wall thickness or %EDV. ETCO2 was a significant predictive factor for LV wall thickness (P = 0.014) and %EDV (P = 0.013). However, it could explain only 6.1% and 14.2% of the total variance of LV wall thickness and %EDV in our models, respectively.
Conclusions: ETCO2 was a significant predictive factor for the severity of ischemic contracture. However, it explained only a small proportion of the variance of ischemic contracture severity.

2 - Haemodynamic parameters during cardiopulmonary resuscitation in estimating the degree of ischaemic contracture