Left ventricular unloading before reperfusion reduces endothelin-1 release and calcium overload in porcine myocardial infarction

Application of Cardiovascular Physiology to the Critically Ill Patient

OBJECTIVES

To use the ventricular pressure-volume relationship and time-varying elastance model to provide a foundation for understanding cardiovascular physiology and pathophysiology, interpreting advanced hemodynamic monitoring, and for illustrating the physiologic basis and hemodynamic effects of therapeutic interventions. We will build on this foundation by using a cardiovascular simulator to illustrate the application of these principles in the care of patients with severe sepsis, cardiogenic shock, and acute mechanical circulatory support.

DATA SOURCES

Publications relevant to the discussion of the time-varying elastance model, cardiogenic shock, and sepsis were retrieved from MEDLINE. Supporting evidence was also retrieved from MEDLINE when indicated.

STUDY SELECTION, DATA EXTRACTION, AND SYNTHESIS

Data from relevant publications were reviewed and applied as indicated.

CONCLUSIONS

The ventricular pressure-volume relationship and time-varying elastance model provide a foundation for understanding cardiovascular physiology and pathophysiology. We have built on this foundation by using a cardiovascular simulator to illustrate the application of these important principles and have demonstrated how complex pathophysiologic abnormalities alter clinical parameters used by the clinician at the bedside.

Fyn Signaling in Ischemia-Reperfusion Injury: Potential and Therapeutic Implications

Ischemic stroke caused by arterial occlusion is the most common type of stroke and is one of the leading causes of disability and death, with the incidence increasing each year. Fyn is a nonreceptor tyrosine kinase belonging to the Src family of kinases (SFKs), which is related to many normal and pathological processes of the nervous system, including neurodevelopment and disease progression. In recent years, more and more evidence suggests that Fyn may be closely related to cerebral ischemia-reperfusion, including energy metabolism disorders, excitatory neurotoxicity, intracellular calcium homeostasis, free radical production, and the activation of apoptotic genes. This paper reviews the role of Fyn in the pathological process of cerebral ischemia-reperfusion, including neuroexcitotoxicity and neuroinflammation, to explore how Fyn affects specific signal cascades and leads to cerebral ischemia-reperfusion injury. In addition, Fyn also promotes the production of superoxide and endogenous NO, so as to quickly react to produce peroxynitrite, which may also mediate cerebral ischemia-reperfusion injury, which is discussed in this paper. Finally, we revealed the treatment methods related to Fyn inhibitors and discussed its potential as a clinical treatment for ischemic stroke.

Mechanical Unloading of the Left Ventricle before Coronary Reperfusion in Preclinical Models of Myocardial Infarction without Cardiogenic Shock: A Meta-Analysis

Aim: to compare a conventional primary reperfusion strategy with a primary unloading approach before reperfusion in preclinical studies. Methods: we performed a meta-analysis of preclinical studies. The primary endpoint was infarct size (IS). Secondary endpoints were left ventricle end-diastolic pressure (LVEDP), mean arterial pressure (MAP), heart rate (HR), cardiac output (CO). We calculated mean differences (MDs) and associated 95% confidence intervals (CIs). Sensitivity and subgroup analyses on the primary and secondary endpoints, as well as a meta-regression on the primary endpoint using the year of publication as a covariate, were also conducted. Results: 11 studies (n = 142) were selected and entered in the meta-analysis. Primary unloading reduced IS (MD −28.82, 95% CI −35.78 to −21.86, I2 96%, p < 0.01) and LVEDP (MD −3.88, 95% CI −5.33 to −2.44, I2 56%, p = 0.02) and increased MAP (MD 7.26, 95% CI 1.40 to 13.12, I2 43%, p < 0.01) and HR (MD 5.26, 95% CI 1.97 to 8.55, I2 1%, p < 0.01), while being neutral on CO (MD −0.11, 95% CI −0.95 to 0.72, I2 88%, p = 0.79). Sensitivity and subgroup analyses showed, overall, consistent results. The meta-regression on the primary endpoint demonstrated a significant influence of the year of publication on effect estimate. Conclusions: in animal models of myocardial infarction, a primary unloading significantly reduces IS and exerts beneficial hemodynamic effects compared to a primary reperfusion.

The combination approach with Rho-kinase inhibition and mechanical circulatory support in myocardial ischemia-reperfusion injury: Rho-kinase inhibition and ventricular unloading

Background

It remains unclear whether the Rho-kinase (ROCK) inhibition in combination with mechanical circulatory support (MCS) had a synergic protective effect on myocardial ischemia (MI)/reperfusion injury in therapeutic strategies for acute myocardial infarction (AMI). We report the results of an approach using a rat model consisting of a miniaturized cardiopulmonary bypass (CPB) and AMI.

Methods

A total of 25 male Wistar rats were randomized into 5 groups: (1) Sham: a suture was passed under the left anterior descending artery (LAD) creating no MI. A vehicle solution (0.9% saline) was injected intraperitoneally. (2) Myocardial ischemia (MI) + vehicle (MI + V): LAD was ligated for 30 min and reperfused for 120 min, followed by administration of vehicle solution. (3) MI + fasudil (MI + F): the work sequence of group 2, but the selective ROCK inhibitor fasudil (10 mg/kg) was administered instead. (4) MI + V + CPB: CPB was initiated 15 min after the ligation of the LAD to the end of the reperfusion, in addition to the work sequence in group 2. (5) In the MI + F + CPB group, the work sequence of group 4, but with fasudil administration (10 mg/kg).

Results

Measurements of cardiac function through conductance catheter indicated that the drop of + dP/dt after reperfusion was moderately limited in MI + F + CPB (vs. MI + V, dP/dt p = 0.22). The preload recruitable stroke work was moderately improved in the MI + F + CPB (p = 0.23) compared with the corresponding control animals (MI + V). Phosphorylated protein kinase B expression in the MI + V + CPB and MI + F + CPB was higher than that in MI + V (p = 0.33).

Conclusion

Therefore, fasudil administration with MCS resulted in a moderately better left ventricular performance.

Early experience with donation after circulatory death heart transplantation using normothermic regional perfusion in the United States

OBJECTIVE

This pilot study sought to evaluate the feasibility of our donation after circulatory death (DCD) heart transplantation protocol using cardiopulmonary bypass (CPB) for normothermic regional reperfusion (NRP).

METHODS

Suitable local DCD candidates were transferred to our institution. Life support was withdrawn in the operating room (OR). On declaration of circulatory death, sternotomy was performed, and the aortic arch vessels were ligated. CPB was initiated with left ventricular venting. The heart was reperfused, with correction of any metabolic abnormalities. CPB was weaned, and cardiac function was assessed at 30-minute intervals. If accepted, the heart was procured with cold preservation and transplanted into recipients in a nearby OR.

RESULTS

Between January 2020 and January 2021, a total of 8 DCD heart transplants were performed: 6 isolated hearts, 1 heart-lung, and 1 combined heart and kidney. All donor hearts were successfully resuscitated and weaned from CPB without inotropic support. Average lactate and potassium levels decreased from 9.39 ± 1.47 mmol/L to 7.20 ± 0.13 mmol/L and 7.49 ± 1.32 mmol/L to 4.36 ± 0.67 mmol/L, respectively. Post-transplantation, the heart-lung transplant recipient required venoarterial extracorporeal membrane oxygenation for primary lung graft dysfunction but was decannulated on postoperative day 3 and recovered uneventfully. All other recipients required minimal inotropic support without mechanical circulatory support. Survival was 100% with a median follow-up of 304 days (interquartile range, 105-371 days).

CONCLUSIONS

DCD heart transplantation outcomes have been excellent. Our DCD protocol is adoptable for more widespread use and will increase donor heart availability in the United States.

Left Ventricular Assist Devices for Acute Myocardial Infarct Size Reduction: Meta-analysis

We conducted a meta-analysis of preclinical studies that tested left ventricular assist device (LVAD) therapy for reducing myocardial infarct size in experimental acute myocardial infarction (AMI). Twenty-six articles were included with a total of 488 experimental animal subjects. The meta-analysis showed that infarct size was significantly decreased by LVAD support compared to control animals (SDM, - 2.19; 95% CI, - 2.70 to - 1.69; P < 0.001). The meta-regression analysis demonstrated a high degree of heterogeneity associated with time from coronary artery occlusion to LVAD support, which correlated positively with infarct size. Subgroup analysis suggested smaller infarct size in LVAD therapies that withdrew blood from left heart than those from right heart. The proportion of left ventricular support relative to total cardiac output was positively correlated with infarct size reduction in Impella studies. Thus, early initiation of LVAD after ischemia and effective left ventricular venting may be important factors to reduce infarct size in AMI.

Hurdles to Cardioprotection in the Critically Ill

Cardiovascular disease is the largest contributor to worldwide mortality, and the deleterious impact of heart failure (HF) is projected to grow exponentially in the future. As heart transplantation (HTx) is the only effective treatment for end-stage HF, development of mechanical circulatory support (MCS) technology has unveiled additional therapeutic options for refractory cardiac disease. Unfortunately, despite both MCS and HTx being quintessential treatments for significant cardiac impairment, associated morbidity and mortality remain high. MCS technology continues to evolve, but is associated with numerous disturbances to cardiac function (e.g., oxidative damage, arrhythmias). Following MCS intervention, HTx is frequently the destination option for survival of critically ill cardiac patients. While effective, donor hearts are scarce, thus limiting HTx to few qualifying patients, and HTx remains correlated with substantial post-HTx complications. While MCS and HTx are vital to survival of critically ill cardiac patients, cardioprotective strategies to improve outcomes from these treatments are highly desirable. Accordingly, this review summarizes the current status of MCS and HTx in the clinic, and the associated cardiac complications inherent to these treatments. Furthermore, we detail current research being undertaken to improve cardiac outcomes following MCS/HTx, and important considerations for reducing the significant morbidity and mortality associated with these necessary treatment strategies.

Mechano-chronotropic Unloading During the Acute Phase of Myocardial Infarction Markedly Reduces Infarct Size via the Suppression of Myocardial Oxygen Consumption

The oxygen supply-demand imbalance is the fundamental pathophysiology of myocardial infarction (MI). Reducing myocardial oxygen consumption (MVO₂) in acute MI (AMI) reduces infarct size. Since left ventricular (LV) mechanical work and heart rate are major determinants of MVO₂, we hypothesized that the combination of LV mechanical unloading and chronotropic unloading during AMI can reduce infarct size via synergistic suppression of MVO₂. In a dog model of ischemia-reperfusion, as we predicted, the combination of mechanical unloading by Impella and bradycardic agent, ivabradine (IVA), synergistically reduced MVO₂. This was translated into the striking reduction of infarct size with Impella + IVA administered 60 min after the onset of ischemia compared to no treatment (control) and Impella groups (control 56.3 ± 6.5, Impella 39.9 ± 7.4 and Impella + IVA 23.7 ± 10.6%, p < 0.001). In conclusion, Impella + IVA during AMI reduced infarct size via marked suppression of MVO₂. The mechano-chronotropic unloading may serve as a powerful therapeutic option for AMI.

Effect of Early Initiation of Mechanical Circulatory Support on Survival in Cardiogenic Shock

The role and timing of percutaneous mechanical circulatory support (MCS) devices in the treatment of acute myocardial infarction complicated by cardiogenic shock (AMICS) are not well understood. We sought to evaluate patient characteristics and predictors of outcomes in patients presenting with AMICS supported with an axial flow percutaneous MCS device; 287 consecutive unselected patients enrolled in the catheter-based ventricular assist device registry presenting with AMICS who underwent percutaneous coronary intervention (PCI) were included in this analysis. All patients were supported with either the Impella 2.5 or Impella CP. Mean patient age was 66 ± 12.5 years, 76% were men, and mean left ventricular ejection fraction was 25 ± 12%. Before receiving MCS, 80% of patients required inotropes or vasopressors and 40% were supported with intra-aortic balloon pump; 9% of patients were under active cardiopulmonary resuscitation at the time of MCS implantation. Survival to discharge was 44%. In a multivariate analysis, early implantation of a MCS device before PCI (p = 0.04) and before requiring inotropes and vasopressors (p = 0.05) was associated with increased survival. Survival was 66% when MCS was initiated <1.25 hours from shock onset, 37% when initiated within 1.25 to 4.25 hours, and 26% when initiated after 4.25 hours (p = 0.017). Survival was 68%, 46%, 35%, 35%, and 26% for patients requiring 0, 1, 2, 3, and ≥4 inotropes before MCS support, respectively (p <0.001). In conclusion, MCS implantation early after shock onset, before initiation of inotropes or vasopressors and before PCI, is independently associated with improved survival in patients presenting with AMICS.

Total Mechanical Unloading Minimizes Metabolic Demand of Left Ventricle and Dramatically Reduces Infarct Size in Myocardial Infarction

Background

Left ventricular assist device (LVAD) mechanically unloads the left ventricle (LV). Theoretical analysis indicates that partial LVAD support (p-LVAD), where LV remains ejecting, reduces LV preload while increases afterload resulting from the elevation of total cardiac output and mean aortic pressure, and consequently does not markedly decrease myocardial oxygen consumption (MVO₂). In contrast, total LVAD support (t-LVAD), where LV no longer ejects, markedly decreases LV preload volume and afterload pressure, thereby strikingly reduces MVO₂. Since an imbalance in oxygen supply and demand is the fundamental pathophysiology of myocardial infarction (MI), we hypothesized that t-LVAD minimizes MVO₂ and reduces infarct size in MI. The purpose of this study was to evaluate the differential impact of the support level of LVAD on MVO₂ and infarct size in a canine model of ischemia-reperfusion.

Methods

In 5 normal mongrel dogs, we examined the impact of LVAD on MVO₂ at 3 support levels: Control (no LVAD support), p-LVAD and t-LVAD. In another 16 dogs, ischemia was induced by occluding major branches of the left anterior descending coronary artery (90 min) followed by reperfusion (300 min). We activated LVAD from the beginning of ischemia until 300 min of reperfusion, and compared the infarct size among 3 different levels of LVAD support.

Results

t-LVAD markedly reduced MVO₂ (% reduction against Control: -56 ± 9%, p<0.01) whereas p-LVAD did less (-21 ± 14%, p<0.05). t-LVAD markedly reduced infarct size compared to p-LVAD (infarct area/area at risk: Control; 41.8 ± 6.4, p-LVAD; 29.1 ± 5.6 and t-LVAD; 5.0 ± 3.1%, p<0.01). Changes in creatine kinase-MB paralleled those in infarct size.

Conclusions

Total LVAD support that minimizes metabolic demand maximizes the benefit of LVAD in the treatment of acute myocardial infarction.

Endothelin-1 release during the early phase of reperfusion is a mediator of myocardial reperfusion injury

PURPOSE

In acute myocardial infarction, left ventricular (LV) unloading reduces endothelin-1 (ET-1) release. We tested that endogenous ET-1 released during acute myocardial infarction might mediate ischemia/reperfusion (I/R) injury by stimulating increased intracellular calcium concentration, [Ca(2+)]i, and apoptosis.

METHODS

Rabbits were subjected to 1 h of coronary artery occlusion followed by 3 h of reperfusion. Unloading was initiated 15 min prior to reperfusion and was maintained during reperfusion. The control group was subjected to reperfusion. Animals were treated with ET-1 receptor antagonist BQ123. In parallel, isolated rabbit cardiomyocytes subjected to simulated I/R with or without ET-1 or BQ123, intracellular Ca(2+) and cell death were assessed with flow cytometry.

RESULTS

LV unloading prior to reperfusion reduced myocardial ET-1 release at 2 h of reperfusion. Infarct size was reduced in unloaded and BQ123 groups versus controls. LV unloading and BQ123 treatment reduced the percentage of apoptotic cells associated with increases in Bcl-2 protein levels in ischemic regions. BQ123 reduced both ET-1-induced [Ca(2+)]i increase and cell death for myocytes subjected to stimulated I/R.

CONCLUSION

We propose that components of reperfusion injury involve ET-1 release which stimulates calcium overload and apoptosis. Intravenous ET-1 receptor blockade prior to reperfusion may be a protective adjunct to reperfusion therapy in acute myocardial infarction patients.

Garlicin attenuates reperfusion no-reflow in a catheter-based porcine model of acute myocardial infarction

OBJECTIVE

To evaluate whether garlicin can attenuate reperfusion no-reflow in a catheter-based porcine model of acute myocardial infarction (AMI).

METHODS

Twenty-two swine were used: six in a sham-operation group, and eight each in the control and garlicin groups. The distal part of the left anterior descending coronary artery (LAD) in the latter two groups was occluded by a dilated balloon for 2 hr, then reperfused for 3 hr. Garlicin (1.88mg/kg) was injected just before reperfusion until reperfusion for 1 hr in the garlicin group. Hemodynamic data were examined before AMI, 2 hr after occlusion, and 3 hr after reperfusion. Myocardial contrast echocardiography (MCE) and pathological staining were performed to evaluate the myocardial no-reflow area (NRA). Serum proinflammatory cytokines and endothelin (ET)-1 were examined by radioimmunoassay.

RESULTS

Left ventricular systolic pressure (LVSP) and left ventricular end-diastolic pressure (LVEDP) significantly improved in the garlicin group after reperfusion compared with the control group and also 2hr after AMI (p<0.05 for both). MCE and pathological staining both showed garlicin attenuated reperfusion NRA after AMI (p<0.05, p<0.01). Garlicin not only decreased serum interleukin (IL)-6 and tumor necrosis factor (TNF)-α after reperfusion (p<0.05 for both), but also ET-1 level (p<0.01).

CONCLUSION

Garlicin attenuated reperfusion no-reflow in our catheter-based porcrine model of AMI, possibly through decreasing serum proinflammatory cytokines and ET-1.

Endothelin-1 release in acute myocardial infarction as a predictor of long-term prognosis and no-reflow assessed by contrast-enhanced magnetic resonance imaging

BACKGROUND

No-reflow after primary percutaneous coronary intervention (PCI) in ST-elevation myocardial infarction (STEMI) is associated with poor prognosis. Endothelin-1 (ET-1) is a potent endothelium-derived vasoconstrictor that might aggravate reperfusion injury. The aim of our study was to assess the relationship between systemic ET-1 levels and the occurrence of no-reflow as well as to evaluate the prognostic value of ET-1 in a high-risk STEMI population.

METHODS

We examined 128 consecutive patients undergoing primary PCI in acute STEMI <12 hours after symptom onset. Endothelin-1 was assessed before and immediately after primary PCI. Patients were categorized into 2 groups defined by the median ET-1 level on admission. No-reflow was assessed by 3 different methods after PCI: angiographic Thrombolysis in Myocardial Infarction (TIMI) flow and myocardial blush grade, electrocardiographic ST-resolution, and microvascular obstruction (MO) measured by cardiac magnetic resonance imaging (MRI). The primary clinical end points were mortality and major adverse cardiovascular events. Clinical follow-up was conducted after a median of 19 months.

RESULTS

Patients with angiographically (TIMI flow < or =2 or TIMI flow 3 with final myocardial bush grade < or =2 after PCI), electrocardiographically (ST-resolution <30%), and MRI- (presence of MO) detected no-reflow had significantly higher ET-1 levels on admission. At multivariable logistic regression analysis, ET-1 levels on admission were the only significant predictor of MRI-detected no-reflow (P = .03) together with left ventricular ejection fraction (P = .002). An elevated ET-1 level > or = the median on admission was a significant predictor of long-term mortality.

CONCLUSIONS

Endothelin-1 on admission is associated with no-reflow and increased long-term mortality in a high-risk STEMI population reperfused by primary PCI.