Overall, the positive effect of the hot shot interval on recovery of the macroergic phosphates is almost completely lost in the subsequent KH perfusion interval. The apparently contradictory functional recovery of these hearts remained significantly improved. During the cardioplegic hot shot, the temporary high energy phosphate recovery must be closely related to the very low energy demand of the arrested myocardium. In the ensuing KH reperfusion interval, the high energy requirement of the beating heart causes a gradual loss of the apparent improvement in the recovery of macroergic phosphates. As discussed in the case of the beating heart groups, the final myocardium recovery probably reflects the slow recovery in creatine kinase activity .
WBCP hot shot: The first confirmation of the benefits of WBCP (ie, group 3) came from a study on the resuscitative efficiency of blood-based hot shot perfusates carried out by Rosenkranz et al . Our result of superior recovery of WBCP (group 3) compared with diluted-blood hot shot (group 2) is supported by the earlier findings . Acar et al reasoned that the noncardioplegic blood-based hot shot is accompanied by a rise in coronary vascular resistance leading to oxygen delivery deficiency.
On the other hand, the diluted blood group, group 2, displayed a near normal phosphocreatine:ATP ratio (approximately 1.5), probably as a result of improved ATP recovery relative to that of group 1. With about equal calcium ion content for group 1 and group 2 perfusates, the apparent difference in recovery of the ATP pool between the two groups may be related to suboptimal postischemic activity of creatine kinase and the presence of increased amounts of toxic oxygen metabolites in postischemic cells . It was suggested that the well established beneficial antioxidant and free radical scavenging properties of blood attenuate the drop in creatine kinase activity and, hence, the observed high recovery of ATP in group 2 hearts during the hot shot stage. Continue reading
Metabolic results in the present study point to two distinct postischemic cases related to the apparent oxygen demand of the heart. The first case involves the ‘beating’ heart condition of control groups 1 and 2, with high oxygen demand and intermediate metabolic recovery, and the second involves the ‘arrested’ heart condition of groups 3 to 5, with low oxygen demand and high metabolic recovery.
Following an episode of global ischemia, the myocardial tissue is injured as a result of a number of damaging cellular processes, including oxygen deprivation, lack of metabolic substrates, calcium overloading, intracellular acidosis, tissue swelling, etc. To be able to minimize further damage to the postischemic tissue, the hot shot intervention has to be applied early in the reperfusion interval. Naturally, for a spontaneous and effective resuscitation of the heart, the composition of the hot shot intervention perfusate is very important.
Hemodynamic recovery: As indicated from the metabolic results discussed above, the respective recovery of LVDP and +dP/dt parameters for groups 3 to 5 were significantly better than those recorded for groups 1 and 2. Similarly, cardiac work, expressed as the LVDP-heart rate product, was significantly better for groups 3 to 5 than for groups 1 and 2. Within the ‘cardioplegic’ groups, groups 3 to 5, no statistically significant intergroup differences were observed. Continue reading
Intracellular pH: During the preischemic period, the recorded mean pH of the tissue was initially 7.06±0.07 (n=41), decreasing to 6.11±0.11 after 10 to 12 mins of global ischemia. Intracellular Pi peak, indicating an acidic pH, still noticeable in spectra taken early in the hot shot period, completely disappeared by the end of the hot shot stage of reperfusion. An exception was observed for the group 1 hearts that maintained residual ‘acidic’ Pi signal even in spectra taken at the end of the reperfusion period (Figure 1, bottom trace). These spectra displayed two Pi peaks, corresponding to acidic and normal pH values of6.10±0.15 and 6.97±0.09, respectively. Continue reading
The five groups of hearts can be divided into two distinct subgroups, based on metabolic results obtained during the hot shot period (Table 2). One subgroup comprises the three oxygenated cardioplegic interventions, which displayed superior recovery of the phosphocreatine cellular pool, reaching 120% (group 5) and 140% (groups 3 and 4) by the end of the first reperfusion stage (hot shot). The second subgroup comprises groups 1 and 2, which displayed inferior recovery of the phosphocreatine pool (43% and 61%, respectively). The same division, in the degree of recovery, is also evident from analysis of ATP results (Table 2). One notable exception is the warm blood group diluted with KH, group 2, that unexpectedly displayed superior recovery of ATP. All groups reached peak recovery levels within the first 10 mins of the hot shot regimen, and further reperfusion with the same solution did not yield improved recoveries. Continue reading
Metabolic results: For each group, changes were recorded in the steady state cellular pools of phosphocreatine and ATP that occurred during the experimental protocol (Table 2). As expected, and confirmed by the spectra, a drastic decrease in cellular phosphocreatine and ATP with concurrent increase in Pi was indicated during myocardial ischemia (Figure 1). The phosphocreatine signal disappeared from the spectrum early in the ischemic episode, while the ATP signal was slower to disappear and became undetectable at the end of the ischemic interval. Continue reading
Typical coronary flow rates of approximately 20 mL/min were measured in all hearts during the preischemic KH perfusion. To ensure uniform functional assessment criteria for the studied hearts, approximately 10% of the mounted hearts were rejected before ischemia was induced, for which coronary flow rates of 15 mL/min or less and LVSP of 60 mmHg or less were recorded. The uniform status of the studied hearts was manifested by the very similar time lapses it took the mounted hearts to reach ischemic contracture plateau (see next section) from the onset of no-flow ischemia (18.7±0.5, 18.4±0.7, 19.4±0.6, 18.3±0.4, and 19.3±1.0mins for groups 1 to 5, respectively). Moreover, no statistically significant difference was found among the five groups, and the mean ischemic time for all 41 hearts together was 18.8±0.4 min. If your health is of the utmost importance to you, it’s a good idea to visit the best canadian family pharmacy offering highest quality medications with generous discounts and fast delivery right to the doorstep, with full guarantees of your satisfaction.