Blood cardioplegia in the senescent heart

Age- and gender-related differences in the del Nido cardioprotection protocol

BACKGROUND

The evidence regarding the impact of patient's age and gender on del Nido cardioplegia cadioprotection capability in adults is strongly limited.

METHODS

A group of 75 patients undergoing aortic valve replacement (AVR) with del Nido cardioplegia was divided into Group 1 (male) and Group 2 (female). Creatine kinase (CK-MB isoenzyme) and high sensitivity troponin T (hs-TnT) values at 24 hours and 48 hours, occurrence of cardiac activity during crossclamp and ventricular fibrillation (VF) during reperfusion were compared. The impact of age on hs-TnT,CK-MB, VF during reperfusion and cardiac activity during crossclamp was investigated using regression models.

RESULTS

No difference between the groups was reported in 24-hour CK-MB (median 15.57 ng/ml; IQR 12.13-22.82 ng/mL vs 13.97; 12.09-17.147 ng/mL; p= .168), 48-hour CK-MB (6.19; 4.22-7.71 ng/mL vs 6.07;4.56-7.06 ng/mL; p= .707), 24-hour hs-TnT (259.2; 172.0-376.9 pg/mL vs 193.0; 167.8-351 pg/mL.1; p= .339), 48-hour hs-TnT (169.1; 124.9-293.0 pg/mL vs 159.2; 123.12-211.77 pg/mL; p= .673), VF during reperfusion (25% vs 18,5%; p= .774) and cardiac activity during arrest (39.6% vs 37.1%; p= 1.0). Values of CK-MB at 24 hours, hs-TnT at 24 hours and hs-TnT at 48 hours were not dependent on age. The CK-MB at 48 hours was dependent on age (p=.039). Probit regression failed to reveal the impact of patients' age on post-clamp VF occurrence ( p=.11) or electrical activity during arrest (p=.57) .

CONCLUSIONS

Basing on study results, it can be hypothesised that the del Nido cardioplegia provides adequate myocardial protection in AVR patients regardless of age and gender.

Buckberg's blood cardioplegia for protection of adult and senile myocardium in a rat in vitro model of acute myocardial infarction

BACKGROUND

In patients undergoing surgical myocardial revascularization for acute myocardial infarction, excellent myocardial protection can be achieved by blood cardioplegia. We investigated the influence of age on cardiac function, metabolism, and infarct size using Buckberg's blood cardioplegia (BCP).

METHODS

The hearts of male Wistar rats ("adult", age 3 months, n = 8; "senile", age 24 months, n = 8) were excised and mounted on a blood-perfused isolated heart apparatus. An acute myocardial infarction was induced by coronary artery ligation for 30 min before aortic clamping and infusion of Buckberg's BCP. Throughout the experiment, functional parameters were recorded: coronary blood flow (normalized by heart weight), left ventricular peak developed pressure (LVpdP), and positive and negative derived left ventricular pressure over time (dLVPdt_max and dLVPdt_min). Oxygen consumption (MVO₂) and lactate production of the hearts were calculated. The infarct size after 90 min of reperfusion (in % of the area at risk) was measured with triphenyl tetrazolium chloride staining of the myocardium.

RESULTS

The baseline coronary flow normalized by heart weight was significantly lower in the senile hearts (1.6 ± 0.4 ml/(min ∗ g)) compared with the adult hearts (2.0 ± 0.3 ml/(min ∗ g); p = 0.04). After 90 min of aortic clamping, hemodynamic function of senile hearts recovered better than that of adult hearts: LVpdP (adult 57% of baseline [BL]; senile 88% BL; p = 0.044) and dLVPdt_max (adult 74% BL, senile 102% BL; p = 0.12). In contrast, myocardial infarct size was similar between the adult (26%) and senile (21%; p = 0.45) hearts, and coronary flow recovered to a similar extent (55% BL and 58% BL, respectively). During reperfusion, MVO₂ (80% BL and 81% BL) and lactate production (1.2 and 1.3 μmol/min) were similar in the two groups.

CONCLUSION

After acute myocardial infarction in a rat model, hearts recovered function after reperfusion with Buckberg's BCP solution. Hearts from aged animals recovered better than those from younger animals.

Novel cardioprotection strategies for the aged heart: evidence from pre-clinical studies

The incidence of cardiovascular disease is rising as the population ages. This has led to an increase in the need to perform cardiac surgery in older patients. However, aged hearts are particularly susceptible to reperfusion injury following periods of myocardial ischaemia that occur during cardiac surgery. Indeed, older adults experience myocardial dysfunction and reduced survival post-surgery compared to younger people and certain groups, including older women and frail older adults, are at particular risk. This highlights the need to design cardioprotective strategies specifically for the ageing heart. Cardioprotection during surgery is often accomplished by perfusing the heart with chemical arresting agents, known as cardioplegic solutions. New protective strategies have been developed and tested in animal models, where cardioplegic solutions have been modified by changing their temperature, chemical components and/or the frequency of delivery. In addition, drugs designed to activate cardioprotective mechanisms or to inhibit mechanisms involved in injury have been added to improve the efficacy of these solutions. However, most experimental studies have developed and optimized cardioplegic solutions in hearts from younger male animals. This review discusses pre-clinical models used to optimize cardioplegic solutions, with an emphasis on the few studies that have used hearts from older animals. Pharmacologic agents that have been shown to enhance the benefits of cardioplegia in younger hearts and could, in theory, protect vulnerable older hearts are also considered. We emphasize the need to conduct studies in frail older animals of both sexes to facilitate translation of laboratory-based observations to the clinic.

Protecting the aged heart during cardiac surgery: single-dose del Nido cardioplegia is superior to multi-dose del Nido cardioplegia in isolated rat hearts

Background:

Aged hearts are particularly vulnerable to reperfusion injury. We recently showed that single-dose del Nido cardioplegia was superior to ‘standard’ multi-dose 4:1 blood cardioplegia in aged rat hearts. This study seeks to determine if multi-dose del Nido cardioplegia offers additional benefits over single-dose del Nido cardioplegia.

Methods:

Functional recovery after 60 min of cardioplegic arrest was assessed in isolated, working, senescent rat hearts. Single-dose del Nido cardioplegia (n=14) was compared to multi-dose del Nido cardioplegia (n=12) delivered every 20 min.

Results:

Troponin release during reperfusion was similar in the single (0.263±0.056 ng/ml) and multi-dose groups (0.261±0.055 ng/ml). Although functional recovery was similar early after reperfusion (stroke work 91±6 ml*mmHg*g−1 vs. 91±8 ml*mmHg*g−1 for single- vs. multi-dose), it declined over time in the multi-dose group (71±9 vs. 43±9 ml*mmHg*g−1 at 60 min, p=0.0175)

Conclusions:

In aged rat hearts, a single-dose del Nido cardioplegia strategy results in superior functional recovery compared to a multi-dose del Nido cardioplegia strategy.

Differences in ischemic damage between young and old hearts--Effects of blood cardioplegia

OBJECTIVE

Senescent patients exhibit an elevated perioperative risk for cardiac dysfunction, hemodynamic depression and subsequent cardiac death compared to young patients. Despite the fact that a growing proportion of cardiac surgery patients are octogenarians, cardioplegic regimes remain comparable across patients of all ages. We compared the hemodynamic performance, metabolic parameters and ultrastructural changes in adult and senescent rat hearts after application of Buckberg's blood cardioplegia (BCP) to evaluate differences between the age groups regarding postischemic myocardial function and cellular ultrastructure.

METHODS

Hearts of adult (young adult group, 3-4 months) and senescent (old group, 24 months) male Wistar rats were excised and inserted into a blood perfused isolated heart apparatus (Langendorff perfusion). After a stabilization period of 30 min, in 16 adult and 16 senescent hearts, Buckberg BCP was administered antegradely and repeated every 20 min. Six young adult and 3 senescent hearts served as ischemia control. After an aortic clamping time of 90 min an antegrade hot shot was administered. During reperfusion ex vivo cardiac functional parameters were recorded, including coronary blood flow, left ventricular developed pressure (LVDP) and velocity of myocardial contraction or relaxation (+/-dp/dt). Oxygen consumption and lactate production of the hearts were calculated. After perfusion fixation, the hearts of five rats in each BCP group and 3 rats in each ischemia group were investigated for cellular edema and mitochondrial damage by morphometry using transmission electron microscopy.

RESULTS

While recovery of cardiac function after 90 min of unprotected ischemia was significantly impaired in senescent hearts, functional recovery after ischemia protected by BCP was similar in adult and senescent hearts. Mitochondrial ultrastructure was severely damaged in both age groups after 90 min ischemia, but well preserved in both BCP groups. The qualitative analysis was confirmed by the morphometric cellular edema index and the volume-to-surface ratio of the mitochondria. Myocardial oxygen consumption was highest and lactate production was lowest in senescent hearts.

CONCLUSION

Senescent rat hearts were more susceptible to unprotected ischemia/reperfusion injury than young adult hearts. When protected by BCP, we found no difference in hemodynamic performance between adult and senescent hearts indicating preserved myocardial protection even in senescent individuals.

Calciphylaxis in the absence of renal failure and hyperparathyroidism in a nonagenarian

Calciphylaxis is a rare, potentially life-threatening syndrome of progressive cutaneous necrosis from calcium deposition. It is well described in uraemic diseases. However, its mechanism is poorly understood and information on non-uraemic causes is lacking. This is the first report of a biopsy-proven non-uraemic calciphylaxis in a nonagenarian.

Impaired macrophage migration inhibitory factor-AMP-activated protein kinase activation and ischemic recovery in the senescent heart

BACKGROUND

Elderly patients are more sensitive than younger patients to myocardial ischemia, which results in higher mortality. We investigated how aging affects the cardioprotective AMP-activated protein kinase (AMPK) signaling pathway.

METHODS AND RESULTS

Ischemic AMPK activation was impaired in aged compared with young murine hearts. The expression and secretion of the AMPK upstream regulator, macrophage migration inhibitory factor (MIF), were lower in aged compared with young adult hearts. Additionally, the levels of hypoxia-inducible factor 1alpha, a known transcriptional activator of MIF, were reduced in aged compared with young hearts. Ischemia-induced AMPK activation in MIF knockout mice was blunted, leading to greater contractile dysfunction in MIF-deficient than in wild-type hearts. Furthermore, intramyocardial injection of adenovirus encoding MIF in aged mice increased MIF expression and ischemic AMPK activation and reduced infarct size.

CONCLUSIONS

An impaired MIF-AMPK activation response in senescence thus may be attributed to an aging-associated defect in hypoxia-inducible factor 1alpha, the transcription factor for MIF. In the clinical setting, impaired cardiac hypoxia-inducible factor 1alpha activation and consequent reduced MIF expression may play an important role in the increased susceptibility to myocardial ischemia observed in older cardiac patients.

Cardiac and metabolic effects of hypothermia and inhaled hydrogen sulfide in anesthetized and ventilated mice

OBJECTIVE

To test the hypothesis whether inhaled hydrogen sulfide amplifies the effects of deliberate hypothermia during anesthesia and mechanical ventilation as hypothermia is used to provide organ protection after brain trauma or circulatory arrest. Awake mice inhaling hydrogen sulfide exhibit reduced energy expenditure, hypothermia, and bradycardia despite unchanged systolic heart function. In rodents, anesthesia alone causes decreased metabolic rate and thus hypothermia and bradycardia.

DESIGN

Prospective, controlled, randomized study.

SETTING

University animal research laboratory.

SUBJECTS

Male C57/B6 mice.

INTERVENTIONS

After surgical instrumentation (central venous, left ventricular pressure-conductance catheters, ultrasound flow probes on the portal vein and superior mesenteric artery), normo- or hypothermic animals (core temperature = 38 degrees C and 27 degrees C) received either 100 ppm hydrogen sulfide or vehicle over 5 hrs (3 hrs hydrogen sulfide during normothermia).

MEASUREMENTS AND MAIN RESULTS

During normothermia, hydrogen sulfide had no hemodynamic or metabolic effect. With or without hydrogen sulfide, hypothermia decreased blood pressure, heart rate, and cardiac output, whereas stroke volume, ejection fraction, and end-diastolic pressure remained unaffected. Myocardial and hepatic oxidative deoxyribonucleic acid damage (comet assay) and endogenous glucose production (rate of appearance of 1,2,3,4,5,6-13C6-glucose) were similar in all groups. Hypothermia comparably decreased CO2 production with or without inhaled hydrogen sulfide. During hypothermia, inhaled hydrogen sulfide increased the glucose oxidation rate (derived from the expiratory 13CO2/12CO2 ratio). This shift toward preferential carbohydrate utilization coincided with a significantly attenuated responsiveness of hepatic mitochondrial respiration to stimulation with exogenous cytochrome-c-oxidase (high-resolution respirometry).

CONCLUSIONS

In anesthetized and mechanically ventilated mice, inhaled hydrogen sulfide did not amplify the systemic hemodynamic and cardiac effects of hypothermia alone. The increased aerobic glucose oxidation together with the reduced responsiveness of cellular respiration to exogenous cytochrome-c stimulation suggest that, during hypothermia, inhaled hydrogen sulfide improved the yield of mitochondrial respiration, possibly via the maintenance of mitochondrial integrity. Hence, inhaled hydrogen sulfide may offer metabolic benefit during therapeutic hypothermia.

Age- and gender-related differences in ischemia/reperfusion injury and cardioprotection: effects of diazoxide

BACKGROUND

Recent studies have demonstrated that aging is associated with reduced tolerance to ischemia and that the aged (not senescent) female heart has greater susceptibility to ischemia as compared with the aged male heart. Previously, we have shown that ischemia can be modulated with cardioplegia in the male heart; however, efficacy in the female heart was unknown.

METHODS

In this study, male and female mature (15 to 20 weeks) aged (>32 months) rabbit hearts (n = 134) were subjected to Langendorff perfusion. Control hearts were perfused for 180 minutes. Global ischemia hearts received 30 minutes of equilibrium, 30 minutes of global ischemia, and 120 minutes of reperfusion. Cardioplegia +/- diazoxide was infused separately, 5 minutes before global ischemia.

RESULTS

Global ischemia significantly decreased postischemic functional recovery and significantly increased infarct size in the mature and aged male and female heart (p < 0.05 versus control). The effects of global ischemia were significantly exacerbated (p < 0.05) in the aged heart as compared with the mature heart. Cardioplegia +/- diazoxide significantly increased postischemic functional recovery and significantly decreased infarct size in mature male and female hearts, but these effects were significantly decreased in the aged heart (p < 0.05) and in the aged female as compared with the aged male heart.

CONCLUSIONS

Postischemic functional recovery and infarct size are affected by age but not by gender. The cardioprotection afforded by cardioplegia is affected by age and gender with a strong age-by-gender interaction for end-diastolic pressure and infarct size. Our results indicate that currently optimized cardioplegia protocols effective in the male heart are not as efficacious in the aged female heart.

Response of the Senescent Heart to Stress: Clinical Therapeutic Strategies and Quest for Mitochondrial Predictors of Biological Age

The aging heart has an impaired response to many kinds of stress. In clinical practice, there is a need for senescence-specific therapies to protect against stress and for biochemical markers of senescence to identify those patients most in need of therapy. In isolated rat hearts, in human tissues, and in a clinical trial, we have shown previously that coenzyme Q(10) has the ability to protect the heart against stress especially in senescence. We recently have devised a regimen of therapy to protect the senescent heart against stress, combining metabolic therapy (coenzyme Q(10), alpha lipoic acid, magnesium orotate, and omega 3 polyunsaturated fatty acids) with physical exercise and mental stress reduction. The preliminary results of this program are promising. In an endeavor to predict the likely response of individual senescent hearts to stress, we correlated the tissue load of mitochondrial DNA deletions and total cellular mitochondrial DNA copy number in human cardiac tissue with recovery of the same tissue from ischemia/reperfusion stress. We found that these mitochondrial markers actually were less predictive of impaired response to stress than age alone. We conclude that the aging heart has a diminished capacity to recover from stress that is not readily predictable by cardiac content of intact mitochondrial DNA and that this recovery can be improved by metabolic therapy combined with physical exercise and mental stress reduction.

Adenosine-enhanced ischemic preconditioning provides myocardial protection equal to that of cold blood cardioplegia

BACKGROUND

We recently described a novel myoprotective protocol-adenosine-enhanced ischemic preconditioning (APC)-that extends the protection of ischemic preconditioning (IPC) by both reducing myocardial infarct size and enhancing postischemic functional recovery in the isolated perfused heart. In the present report the efficacy of APC in the blood-perfused heart was investigated and compared with that of cold blood cardioplegia (CBC).

METHODS

Cardiopulmonary bypass was instituted in 21 sheep hearts. The APC hearts (n = 6) received a bolus injection of adenosine through the aortic root at the immediate start of IPC (5 minutes of zero-flow global ischemia, followed by 5 minutes of reperfusion) before 30 minutes of global ischemia and 120 minutes of reperfusion. Nine other hearts received CBC. A control group (n = 6) received IPC only.

RESULTS

Infarct size was significantly decreased (p<0.01) in the APC (3.0%+/-0.8%) and CBC (2.6%+/-0.2%) hearts compared with the IPC hearts (16.3%+/-1.6%). The preload recruitable stroke work relation, mean arterial pressure, and the time constant of pressure decay (tau) were significantly preserved (p<0.05) in APC and CBC hearts compared with IPC hearts. No significant differences were observed between APC and CBC hearts.

CONCLUSIONS

Use of APC is as effective as CBC in significantly decreasing infarct size and enhancing post-ischemic functional recovery.

Coenzyme Q10 improves the tolerance of the senescent myocardium to aerobic and ischemic stress: studies in rats and in human atrial tissue

The inferior recovery of cardiac function after interventional cardiac procedures in elderly patients compared to younger patients suggests that the aged myocardium is more sensitive to stress. We report two studies that demonstrate an age-related deficit in myocardial performance after aerobic and ischemic stress and the capacity of CoQ10 treatment to correct age-specific diminished recovery of function. In Study 1 the functional recovery of young (4 mo) and senescent (35 mo) isolated working rat hearts after aerobic stress produced by rapid electrical pacing was examined. After pacing, the senescent hearts, compared to young, showed reduced recovery of pre-stress work performance. CoQ10 pretreatment (daily intraperitoneal injections of 4 mg/kg CoQ10 for 6 weeks) in senescent hearts improved their recovery to match that of young hearts. Study 2 tested whether the capacity of human atrial trabeculae (obtained during surgery) to recover contractile function, following ischemic stress in vitro (60 min), is decreased with age and whether this decrease can be reversed by CoQ10. Trabeculae from older individuals (> or = 70 yr) showed reduced recovery of developed force after simulated ischemia compared to younger counterparts (< 70 yr). Notably, this age-associated effect was prevented in trabeculae pretreated in vitro (30 min at 24 degrees C) with CoQ10 (400 MicroM). We measured significantly lower CoQ10 content in trabeculae from > or = 70 yr patients. In vitro pretreatment raised trabecular CoQ10 content to similar levels in all groups. We conclude that, compared to younger counterparts, the senescent myocardium of rats and humans has a reduced capacity to tolerate ischemic or aerobic stress and recover pre-stress contractile performance, however, this reduction is attenuated by CoQ10 pretreatment.

Human SERCA2a levels correlate inversely with age in senescent human myocardium

OBJECTIVES

This study sought to characterize functional impairment after simulated ischemia-reperfusion (I/R) or Ca2+ bolus in senescent human myocardium and to determine if age-related alterations in myocardial concentrations of SERCA2a, phospholamban, or calsequestrin participate in senescent myocardial dysfunction.

BACKGROUND

Candidates for elective cardiac interventions are aging, and an association between age and impairment of relaxation has been reported in experimental animals. Function of the sarcoplasmic reticulum resulting in diastolic dysfunction could be dysregulated at the level of cytosolic Ca2+ uptake by SERCA2a, its inhibitory subunit (phospholamban), or at the level of Ca2+ binding by calsequestrin.

METHODS

Human atrial trabeculae from 17 patients (45-75 years old) were suspended in organ baths, field simulated at 1 Hz, and force development was recorded during I/R (45/120 min). Trabeculae from an additional 12 patients (53-73 years old) were exposed to Ca2+ bolus (2-3 mmol/L bath concentration). Maximum +/- dF/dt and the time constant of force decay (tau) were measured before and after I/R or Ca2+ bolus and related to age. SERCA2a, phospholamban, and calsequestrin from 12 patients (39-77 years old) were assessed by immunoblot.

RESULTS

Functional results indicated that maximum +/-dF/dt and tau were prolonged in senescent (>60 years) human myocardium after I/R (p < 0.05). Calcium bolus increased the maximum +/-dF/dt and decreased tau in younger, but not older patients (p < 0.05). SERCA2a and the ratio of SERCA2a to either phospholamban or calsequestrin were decreased in senescent human myocardium (p < 0.05).

CONCLUSIONS

Senescent human myocardium exhibits decreased myocardial SERCA2a content with age, which may, in part, explain impaired myocardial function after either I/R or Ca2+ exposure.

Effect of intermittent warm blood cardioplegia on functional recovery after prolonged cardiac arrest

BACKGROUND

There is some evidence that continuous warm blood cardioplegia offers good myocardial protection; however, the effects of interrupting cardioplegia remain controversial. To study this, we compared the effects of continuous and intermittent antegrade warm (37 degrees C) blood cardioplegia on functional recovery after prolonged cardiac arrest (180 minutes).

METHODS

Twenty-four juvenile pigs were randomly assigned into four groups. Group 1 received continuous cardioplegia, group 2 underwent several periods of 15 minutes of cardioplegia interrupted by 5 minutes of normothermic ischemia, and group 3 underwent several periods of 10 minutes of cardioplegia interrupted by episodes of 10 minutes. The hearts of group 4 received no cardioplegia. Left ventricular systolic function was assessed from fractional left ventricular shortening and percentage left ventricular wall thickening, and left ventricular diastolic function was determined from the time constant of relaxation and the constant of myocardial stiffness.

RESULTS

Systolic and diastolic functions were slightly depressed 1 and 2 hours after cross-clamp removal in all four groups, without significant differences among the groups.

CONCLUSIONS

These data suggest that antegrade warm blood cardioplegia can be interrupted for up to 10 minutes without obvious negative effects on left ventricular function in the normal myocardium, provided that the intermittent doses of cardioplegia are sufficient to restore the metabolic demands of the arrested myocardium.

Physiological and cellular mechanisms of myocardial protection

BACKGROUND

Despite 40 years of clinically successful open heart surgery, cardiac surgeons continue to seek the ideal myoprotective strategy to minimize perioperative myocardial damage and maximize clinical outcome. Although crude measures, such as length of hospital stay or operative mortality rate, may provide useful administrative data, the ultimate outcome measure of significance to the patient is the lack of operatively induced myocellular injury.

METHODS

An ideal biological marker would thus quantitate the number of viable and functioning myocytes remaining postoperatively. The purpose of the present review was to develop the theoretical framework for modern approaches to intraoperative myocardial protection when considering the fundamental principles of physiological and cellular ischemic mechanisms.

RESULTS AND CONCLUSIONS

It is hoped that this review provides insight into the implementation of these fundamental concepts developed at the University of Illinois and applied in our present experiences in advanced myocardial muscle mechanics and molecular biology.

Is the preconditioning response conserved in senescent myocardium?

BACKGROUND

Senescent myocardium differs from adult myocardium at both functional and cellular levels. To adjudicate the efficacy of ischemic preconditioning as an alternative or adjuvant myoprotective strategy a reproducible, age-independent, intact laboratory model is necessary.

METHODS

Adult (0.5 to 1.0 years) and senescent (5.7 to 8.0 years) sheep underwent 60 minutes of normothermic regional ischemia with 150 minutes of reperfusion. Group II (adult-ischemic preconditioning) and group IV (aged-ischemic preconditioning) underwent preconditioning with three 5-minute episodes of normothermic regional ischemia. Group I (adult-control) and group III (aged-control) were not preconditioned.

RESULTS

Risk size and infarct size weights were delineated by monastryl blue pigment infusion and buffered tetrazolium solution. Ischemic preconditioning was evidenced by an infarct size reduction of 54% for adult sheep and 47% for senescent sheep (p < 0.01 versus age-matched controls; p = not significant for adult versus senescent).

CONCLUSIONS

The data suggest that the cellular pathways involved with the preconditioning response are well preserved in senescent myocardium and support the utility of the ovine heart model to investigate the clinical relevance of ischemic preconditioning for the increasingly aged population presently undergoing cardiac operations.