Liposome-Encapsulated Hemoglobin Attenuates Cardiac Dysfunction and Sympathetic Activity During Hypohemoglobinemic Shock

Liposome-Encapsulated Hemoglobin Vesicle Improves Persistent Anti-arrhythmogenesis through Improving Myocardial Electrical Remodeling and Modulating Cardiac Autonomic Activity in a Hemorrhagic Shock-Induced Rat Heart Model

OBJECTIVE

Shock heart syndrome (SHS) is associated with lethal arrhythmias (ventricular tachycardia/ventricular fibrillation, VT/VF). We investigated whether liposome-encapsulated human hemoglobin vesicles (HbVs) has comparable persistent efficacy to washed red blood cells (wRBCs) for improving arrhythmogenesis in the subacute to chronic phase of SHS.

METHODS

Optical mapping analysis (OMP), electrophysiological study (EPS), and pathological examinations were performed on blood samples from Sprague-Dawley rats following induction of hemorrhagic shock. After hemorrhagic shock, the rats were immediately resuscitated by transfusing 5% albumin (ALB), HbV, or wRBCs. All rats survived for 1 week. OMP and EPS were performed on Langendorff-perfused hearts. Spontaneous arrhythmias and heart rate variability (HRV) were evaluated using awake 24-h telemetry, cardiac function by echocardiography, and pathological examination of Connexin43.

RESULTS

OMP showed significantly impaired action potential duration dispersion (APDd) in the left ventricle (LV) in the ALB group whereas APDd was substantially preserved in the HbV and wRBCs groups. Sustained VT/VF was easily provoked by EPS in the ALB group. No VT/VF was induced in the HbV and wRBCs groups. HRV, spontaneous arrhythmias, and cardiac function were preserved in the HbV and wRBCs groups. Pathology showed myocardial cell damage and Connexin43 degradation in the ALB group, all of which were attenuated in the HbV and wRBCs groups.

CONCLUSION

LV remodeling after hemorrhagic shock caused VT/VF in the presence of impaired APDd. Similar to wRBCs, HbV persistently prevented VT/VF by inhibiting persistent electrical remodeling, preserving myocardial structures, and ameliorating arrhythmogenic modifying factors in the subacute to chronic phase of hemorrhagic shock-induced SHS.

Intraosseous infusion of liposome-encapsulated hemoglobin (HbV) acutely prevents hemorrhagic anemia-induced lethal arrhythmias and its efficacy persists with preventing proarrhythmic side effects in subacute phase of severe hemodilution model

BACKGROUND

Artificial oxygen carriers (HbV) can treat hemorrhagic shock with lethal arrhythmias (VT/VF). No reports exist on subacute HbV's effects.

METHODS

Acute and subacute resuscitation effects with anti-arrhythmogenesis of HbV were studied in 85% blood exchange rat model (85%-Model). Lethal 85%-Model was created by bone marrow transfusion and femoral artery bleeding in 80 SD rats in HbV-administered group (HbV-group), washed erythrocyte-administered group (wRBC-group), and 5% albumin-administered group (ALB-group). Survival rates, anti-arrhythmic efficacy by optical mapping analysis (OMP) with electrophysiological stimulation (EPS) in Langendorff heart, cardiac autonomic activity by heart rate variability (HRV) and ventricular arrhythmias by 24-hour electrocardiogram telemetry monitoring (24h-ECG) in awake, and left ventricular function by echocardiography (LVEF) were measured.

RESULTS

All rats in HbV- and wRBC-groups survived for 4 weeks whereas no rats in ALB-group. HbV and wRBC acutely suppressed VT/VF in Langendorff heart through ameliorating action potential duration dispersion (APDd) analyzed by OMP with EPS. For subacute analysis, 50% blood exchange by 5% albumin was utilized (ALB-group 50). Subacute salutary effect on APDd and VT/VF inducibility was confirmed in HbV- and wRBC-groups. 24h-ECG showed that HbV and wRBC suppressed none-sustained VT (NSVT) and sympathetic component of HRV (LF/HF) with preserved LVEF (HbV-group, wRBC-group vs. ALB-group 50;NSVT numbers/days, 0.5±0.3, 0.4±0.3 vs. 3.9±1.2*; LF/HF, 1.1±0.2, 0.8±0.2 vs. 3.5±1.0*;LVEF, 84±5, 83±4, vs. 77±4%*; *p<0.05).

CONCLUSIONS

Collectively, HbV has sustained antiarrhythmic effect in subacute 85%-Model by ameliorating electrical remodeling and improving arrhythmogenic modifying factors (HRV and LVEF). These findings are useful in now continuing clinical trials of HbV.

Liposome-encapsulated hemoglobin (HbV) transfusion rescues rats undergoing progressive lethal 85% hemorrhage as a result of an anti-arrhythmogenic effect on the myocardium

Liposome-encapsulated hemoglobin vesicles (HbV) can serve as a blood substitute with oxygen-carrying capacity comparable to that of human blood and lethal hemorrhage is associated with lethal arrhythmias. To investigate the resuscitation effect of HbV on lethal hemorrhage and anti-arrhythmogenesis, we performed optical mapping analysis (OMP) and electrophysiological study (EPS) in graded blood exchange (85% blood loss) in the rat model. We also measured cardiac autonomic activity, as assessed by heart rate variability (HRV), and changes in plasma norepinephrine and left ventricle ejection fraction (LVEF) by echocardiography. Pathological study on Connexin43 was performed. A 5% albumin (ALB group), washed rat erythrocytes (wRBC group), and HbV (HbV group) were used as a resuscitation fluid. The survival effects over 24 hours were examined. All rats died in the ALB group, whereas almost all survived for 24-hours period in wRBC and HbV groups. OMP showed impaired action potential duration dispersion (APDd) in the ALB group, whereas normal APDs in HbV and wRBC groups. Lethal arrhythmias were induced by EPS in the ALB group, but not in wRBC and HbV groups. HRV indices, LVEF, Connexin43 were preserved in HbV and wRBC groups. Lethal hemorrhage causes lethal arrhythmias in the presence of impaired APDd. HbV acutely rescues lethal hemorrhage by preventing lethal arrhythmias and preserving arrhythmogenic factors.

Myocardial Electrical Remodeling and the Arrhythmogenic Substrate in Hemorrhagic Shock-Induced Heart: Anti-Arrhythmogenic Effect of Liposome-Encapsulated Hemoglobin (HbV) on the Myocardium

INTRODUCTION

Prolonged low blood pressure <40 mmHg in hemorrhagic shock (HS) causes irreversible heart dysfunction, 'Shock Heart Syndrome' (SHS), which is associated with lethal arrhythmias (ventricular tachycardia or ventricular fibrillation [VT/VF]) leading to a poor prognosis.

METHODS

To investigate whether the liposome-encapsulated human hemoglobin oxygen carrier (HbV) is comparable in effectiveness to autologous washed red blood cells (wRBCs) for improving arrhythmogenic properties in SHS, optical mapping analysis (OMP), electrophysiological study (EPS), and pathological examinations were performed in Sprague-Dawley rat hearts obtained from rats subjected to acute HS by withdrawing 30% of total blood volume. After acute HS, the rats were immediately resuscitated by transfusing exactly the same amount of saline (SAL), 5% albumin (5% ALB), HbV, or wRBCs. After excising the heart, OMP and EPS were performed in Langendorff-perfused hearts.

RESULTS

OMP showed a tendency for abnormal conduction and significantly impaired action potential duration dispersion (APDd) in both ventricles with SAL and 5% ALB. In contrast, myocardial conduction and APDd were substantially preserved with HbV and wRBCs. Sustained VT/VF was easily provoked by a burst pacing stimulus to the left ventricle with SAL and 5% ALB. No VT/VF was induced with HbV and wRBCs. Pathology showed myocardial structural damage characterized by worse myocardial cell damage and Connexin43 with SAL and 5% ALB, whereas it was attenuated with HbV and wRBCs.

CONCLUSIONS

Ventricular structural remodeling after HS causes VT/VF in the presence of APDd. Transfusion of HbV prevents VT/VF, similarly to transfusion of wRBCs, by preventing electrical remodeling and preserving myocardial structures in HS-induced SHS.