Regional changes in myocardial acid production during ischemic arrest: a comparison of sanguineous and asanguineous cardioplegia

Custodiol-N versus Custodiol: a prospective randomized double-blind multicenter phase III trial in patients undergoing elective coronary bypass surgery

OBJECTIVE

HTK-Solution (Custodiol) is a well-established cardioplegic and organ preservation solution. We currently developed a novel HTK-based solution, Custodiol-N, which includes iron chelators to reduce oxidative injury, as well as L-arginine, to improve endothelial function. In this first in-human study, Custodiol-N compared to Custodiol in patients undergoing elective coronary artery bypass surgery. The aim of this comparison was to evaluate the safety and ability of Custodiol-N to protect cardiac tissue.

METHODS

The study was designed as a prospective randomized double-blind non-inferiority trial. Primary end-point was area under the curve (AUC) of creatine kinase MB (CK-MB) within the first 24 h after surgery. Secondary end-points included peak CK-MB and troponin-T and AUC of troponin-T release, cardiac index, cumulative catecholamine dose, ICU-stay and mortality. All values in the abstract are given as mean ± SD, p < 0.05 was considered statistically significant.

RESULTS

Early termination of the trial was performed per protocol as the primary non-inferiority end-point was reached after inclusion of 101 patients. CK-MB AUC (878 ± 549 vs 779 ± 439 h* U/l, non-inferiority p < 0.001, Custodiol vs Custodiol-N) and troponin-T AUC (12990 ± 8347 vs 13498 ± 6513 h*pg/ml, noninferiority p < 0.001, Custodiol vs Custodiol-N) were similar in both groups. Although the trial was designed for non-inferiority, peak CK-MB (52 ± 40 vs. 42 ± 28 U/l, superiority p < 0.03, Custodiol vs Custodiol-N) was significantly lower in the Custodiol-N group.

CONCLUSION

This study shows that Custodiol-N is safe and provides similar cardiac protection as the established HTK-Custodiol solution. Significantly reduced peak CK-MB levels in the Custodiol-N group in the full analysis set may implicate a beneficial effect on ischaemia/reperfusion injury in the setting of coronary bypass surgery.

A SiC microdevice for the minimally invasive monitoring of ischemia in living tissues

Monitoring of ischemia in living tissues is a field of increasing interest in many clinical settings. In this work we report for the first time anywhere the development of needle-shaped, minimally-invasive impedance probes based on silicon carbide (SiC) substrates. An in-vitro comparison of these new devices with Si-based impedance probes demonstrates that their effective operation range extends up to the 100 kHz range, thus allowing a wide-spectrum multi-frequency analysis of impedance modulus and phase angle. Furthermore, we show that, when applied to in-vivo settings, this kind of analysis yields to an accurate monitoring of ischemia, while making possible the application of more robust mathematical methods for the study of impedance in living tissues.

Aspartate and glutamate-enriched cardioplegia in left ventricular dysfunction

BACKGROUND

The effects of exogenous L-aspartate and L-glutamate-enriched cardioplegia on postoperative left ventricular functions after coronary artery bypass surgery in patients with moderate left ventricular dysfunction (left ventricular ejection fraction [LVEF]= 30-40%) were studied.

METHODS

In this prospective randomized study, 22 patients with moderate left ventricular dysfunction (mean LVEF = 37.27%+/- 3.43%), who underwent elective coronary artery bypass surgery, were examined. Isothermic substrate-enriched [L-aspartate and L-glutamate (13 mmol/L)] blood cardioplegia was used in 11 patients (Group AG), and cardioplegia including only potassium and sodium bicarbonate was used in 11 patients (Group C). All hemodynamic parameters for left and right heart were studied in both groups. Total perfusion time was 126.63 +/- 44.91 minutes versus 114.81 +/- 43.66 minutes (p = 0.54). The aortic cross-clamp time was 77.09 +/- 28.02 minutes versus 67.81 +/- 22.77 minutes (p = 0.4), respectively. The amount of cardioplegic solutions were 7218.2 +/- 3043.6 mL versus 5454.5 +/- 3048.1 mL (p = 0.167). Mean number of distal anastomosis were 3 +/- 0.89 versus 2.9 +/- 0.7 (p = 0.793).

RESULTS

There was no difference between both groups in intra- and postoperative periods. In coronary sinus blood gas measures, myocardial acidosis caused by the aortic cross-clamp was found to be more severe in the Group C, but delta pH (0.12 +/- 0.14 vs. 0.092 +/- 0.058; p = 0.613) and delta lactate (1.39 +/- 1.03 vs. 1.62 +/- 0.85; p = 0.579) were similar in both groups. Free oxygen radical production caused by aortic cross-clamp was significant in the Group C. Not all myocardial enzymes, but Troponin-T levels were found higher in control group than the study group (0.6 +/- 0.36 vs. 0.36 +/- 0.25; p = 0.1).

CONCLUSIONS

Although L-aspartate and L-glutamate favor myocardial metabolic functions, they do not have any affect on myocardial functional recovery in patients with moderate left ventricular dysfunction.

Role of myocardial temperature measurement in monitoring the adequacy of myocardial protection during cardiac surgery

Inadequate myocardial protection continues to be encountered despite improved methods of cardioplegia delivery. Although myocardial temperature is commonly monitored to assess the adequacy of cardioplegia delivery, its relationship to the metabolic status of the myocardium has not been investigated. We prospectively reviewed patients who underwent valvular heart surgery with blood (n = 47) or crystalloid (n = 48) cardioplegia and continuous measurement of intraoperative myocardial tissue pH and temperature. We previously demonstrated a high correlation (r = 0.99) between extracellular myocardial pH, levels of intracellular hydrogen ion concentration, and a lowering of tissue ATP during coronary occlusion. Clinically, optimal metabolic protection was defined as the absence of myocardial tissue acidosis during the period of aortic occlusion as quantified by a temperature-corrected integrated mean pH of 6.8 or greater, which has been shown to be predictive of a favorable postoperative outcome. Age, bypass time, myocardial temperature, myocardial tissue pH at the onset of aortic occlusion, cross-clamp time, and volume of cardioplegia were not significantly different between blood and crystalloid groups. Linear regression analysis demonstrated no significant correlation between mean myocardial tissue pH and the corresponding mean myocardial temperature in either group during aortic occlusion. There was also no correlation between the mean myocardial tissue pH and volume of cardioplegia delivered in both groups. These data demonstrate wide intercardiac and intracardiac variability in the degree of regional tissue acidosis encountered during of hypothermic cardioplegia. Cardioplegia delivery guided by measurement of myocardial temperature or by standardized protocol did not prevent the occurrence of tissue acidosis and thus, did not ensure optimal metabolic protection of the heart. In 95 patients undergoing valvular heart surgery with cold blood or crystalloid cardioplegia, there was no correlation between myocardial tissue pH and mycardial temperature or between myocardial tissue pH and volume of cardioplegia administered. Temperature is a poor indicator of the metabolic state of the myocardium.

Proper timing of blood cardioplegia in infant lambs: superiority of a multiple-dose regimen

BACKGROUND

In the pediatric and infant age groups, it is unclear whether repeated infusions of blood cardioplegia solution during ischemic arrest are beneficial or detrimental when compared with a single-dose regimen.

METHODS

Twenty lambs (aged 6 to 7 weeks) were placed on cardiopulmonary bypass. A miniature glass-tip electrode measured myocardial pH and hydrogen ion concentration, [H+], in the anterior wall. The aorta was clamped for 2 hours. Group S (n = 10) received a single dose of blood cardioplegia solution. Group M (n = 10) received multiple doses of blood cardioplegia solution at 20-minute intervals.

RESULTS

The amount of [H+] generated during the cross-clamp period was greater in group S than in group M (39.2 +/- 10.1 nmol/L versus 0.4 +/- 1.4 nmol/L, p < 0.008). The percent increase in the time constant, tau, an index of diastolic relaxation, was more prolonged after cardiopulmonary bypass in group S when compared with group M (51.4% +/- 2.8% versus 6.4% +/- 3.0%, p < 0.0001). Similarly, the percent decrease in end systolic elastance, a measure of systolic contractility, was greater in group S after cardiopulmonary bypass when compared with group M (29.5% +/- 1.4% versus 7.3% +/- 1.3%, p < 0.0001).

CONCLUSIONS

In this infant lamb model, multiple doses of blood cardioplegia solution provided superior metabolic preservation and hemodynamic support after 2 hours of aortic clamping when compared with a single-dose regimen.

Effects of cold and warm blood cardioplegia assessed by myocardial pH and release of metabolic markers

The optimal temperature of blood cardioplegia remains controversial. Interstitial myocardial pH was monitored online with a probe that was inserted in the anterior wall of the left ventricle. Venous pH, lactate production, and creatine kinase and troponin T release were measured in coronary sinus blood obtained in 14 dogs after ischemic arrest periods of 5, 10, 20, and 40 minutes with warm (n = 7; mean myocardial temperature, 35 degrees +/- 2 degrees C) and cold (n = 7; mean myocardial temperature, 12 degrees +/- 1 degree C) blood cardioplegic protection. Blood cardioplegic solution was delivered at a rate of 100 mL/min during the 10 minutes between each ischemic arrest. The interstitial myocardial pH decreased significantly (p < 0.05) from 7.1 +/- 0.3 to 6.53 +/- 0.3 after ischemia in animals perfused with warm blood cardioplegia and from 7.04 +/- 0.3 to 6.64 +/- 0.1 in those receiving cold blood cardioplegic protection; however, the difference between the groups was not significant (p > 0.05). Lactate production and creatine kinase and troponin T release increased significantly after ischemia, but there was no difference in the changes between the warm and cold blood cardioplegia groups. In conclusion, ischemia caused significant changes in all variables measured, and these changes were directly proportional to the duration of ischemia. However, there was no significant difference (p > 0.05) in the myocardial metabolic changes between the warm and cold blood cardioplegia groups in terms of the duration of ischemic arrest studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Current status of cardiac surgery: a 40 year review

Cardiac surgery has undergone dramatic advancements during the past 3 decades. The introduction of cardiopulmonary bypass and cardioplegic arrest ushered in the true era of open heart surgery. Bioprostheses and mechanical valves as well as techniques for valve reconstruction permit routine repair or replacement of stenotic and regurgitant native valves. Progress in the disciplines of mechanical and electrical engineering has led to the development of pocket watch-sized, physiologically responsive pacemakers as well as a variety of circulatory assist devices that include the intraaortic balloon pump, ventricular assist device and total artificial heart. The synthesis of cardiotonic and vasoactive drugs and advancements in anesthetic management, postoperative monitoring and nursing care greatly facilitate perioperative patient management. This summary of state of the art cardiac surgery begins with a brief historical background followed by a review of recent advances in six main categories: coronary artery disease, acquired valvular heart disease, congenital cardiac disease, cardiac transplantation, myocardial preservation and mechanical circulatory assistance. In conducting the review of recent literature, particular attention was directed to large clinical series that document the results of contemporary surgical procedures, novel therapeutic approaches to current clinical problems and unresolved controversies in the field of cardiac surgery. The abundance of surgical literature and constraints on the length of this article do not permit an exhaustive review. Apologies are extended to clinicians and laboratory investigators whose important contributions to the understanding and treatment of cardiac disease are not included herein.