Early cardiac damage after subarachnoid hemorrhage in rats

Subarachnoidal hemorrhage related cardiomyopathy: an overview of Tako-Tsubo cardiomyopathy and related cardiac syndromes

INTRODUCTION

Subarachnoid hemorrhage (SAH) is caused by a ruptured intracranial aneurysm leading to acute extravasation of blood into the subarachnoid space. SAH has an incidence of 6.3 per 100,000 persons per year in Europe and accounts for 5% of all strokes. SAH occurs at a relatively young age and has poor clinical outcomes and high mortality rates. Cardiac syndromes are regularly seen in patients with acute neurologic disease including SAH. These cardiac complications of SAH are associated with increased morbidity and mortality and present in a large variety and severity.

AREAS COVERED

The main goal of this review is to describe the SAH-related cardiac syndromes. Secondly, we will provide an overview of the underlying pathophysiology regarding the development of cardiac syndromes. Thirdly, we will describe the impact of cardiac syndromes on patient outcome.

EXPERT OPINION

Of all neurology patients, SAH patients have the highest risk of developing takotsubo syndrome (TTS), occurring in about 0.8-30% of patients. Both TTS and neurogenic stunned myocardium have many similarities on echocardiographic evaluation. In European Cardiology consensus, SAH is recognized as a primary cause of TTS.

Traumatic brain injury has not prominent effects on cardiopulmonary indices of rat after 24 hours: hemodynamic, histopathology, and biochemical evidence

BACKGROUND

Accidents are the second reason for mortality and morbidity in Iran. Among them, brain injuries are the most important damage. Clarification of the effects of brain injuries on different body systems will help physicians to prioritize their treatment strategies. In this study, the effect of pure brain trauma on the cardiovascular system and lungs 24 hours post trauma was assessed.

METHODS

Male Wistar rats (n = 32) were divided into sham control and traumatic brain injury (TBI) groups. In TBI animals, under deep anesthesia, a blow to the head was induced by the fall of a 450 g weight from 2 m height. Twenty four hours later, heart electrocardiogram and functional indices, cardiac troponin I, IL-6, TNF-, IL-I in tissue and serum, and the histopathology of heart and lung were assessed.

RESULTS

The results showed that none of the functional, biochemical, inflammatory, and histopathology indices was statistically different between the two groups at 24 hours post TBI. Indices of impulse conduction velocity in atrium (P wave duration and P-R interval) were significantly longer in the TBI group.

CONCLUSION

Overall, no important functional and histopathologic disturbances were found in heart and lung of TBI group after 24 hours. If the data is reproduced in human studies, the medical team could allocate their priority to treatment of brain disorders of the victim in the first 24 hours of pure TBI and postpone extensive assessment of heart and lung health indices to later time, thus reducing patient and health system expenditures.

Early activation of myocardial matrix metalloproteinases and degradation of cardiac troponin I after experimental subarachnoid hemorrhage

BACKGROUND

Matrix metalloproteinases (MMPs) are involved in acute myocardial dysfunction by degrading several intracellular contractile proteins, including cardiac troponin I (cTnI). Here, we examined the temporal profiles of MMPs and cTnI in plasma and myocardial tissue in the acute stage of subarachnoid hemorrhage (SAH).

MATERIALS AND METHODS

SAH was induced by the endovascular suture method in rats. Intracranial pressure and left ventricular (LV) function were recorded. Plasma cTnI and MMPs were measured at 0, 5, 15, 30, 60, 120, and 180 minutes after SAH. Myocardial cTnI and MMP activities were quantified at 30, 60 and 180 min after SAH from homogenized hearts.

RESULTS

SAH-induced rats showed a marked decline in -LV dP/dt(max) (index of LV diastolic function). Plasma samples revealed a noticeable increase in cTnI and pro-MMP-9 activities over the course of 180 minutes. In myocardial tissue, there was a marked increase in pro-MMP-9, pro-MMP-2 activities and expression of activated MMP-2. Western blot analysis revealed a striking decrease in cTnI content and increase in cTnI degradation in myocardium. Simultaneous cTnI depletion and MMP-2 expression in myocardium was detected by immunohistochemistry as early as 30 minutes after SAH. MMPs correlated with -LV dP/dt(max) (% of baseline) both in plasma and in myocardial tissue. Furthermore, activated MMP-2 activity correlated positively with cTnI degradation in myocardium.

CONCLUSIONS

Early activation of MMPs was observed in myocardium and plasma following SAH. Activated MMP-2 may regulate proteolytic cTnI and contribute to myocardium stunning injury in SAH rats.

Effects of gender on heart injury after intracerebral hemorrhage in rats

Intracerebral hemorrhage (ICH)-induced brain injury is less in female than in male rats, and estrogen can reduce such injury in males. Myocardial injury occurs after ischemic and hemorrhagic stroke, and the current study investigated the effects of gender on heart injury after ICH in rats. In the first part of the study, male and female rats had an intracerebral injection of 100 μL autologous blood, and sham-operated rats had a needle insertion. In the second part of the study, male rats were treated with 17β-estrodiol or vehicle 2 h after ICH. All rats were then killed after 3 days and heart samples collected for histology and Western blot analysis. ICH caused heart injury, including petechial hemorrhage in male and female rats. To quantify heart stress following ICH, heat shock proteins (HSP) 32 and 27 were measured by Western blot analysis. We found that heart HSP-32 levels were higher in female compared to male rats after ICH (p<0.01), but there was no effect of gender in sham-operated rats (p>0.05), nor were there gender differences in myocardial HSP27 levels. Treatment with 17β-estrodiol increased HSP-32 levels in male ICH rats (p<0.05). In conclusion, an ICH results in heart injury by an unknown mechanism. Gender and estrogen affect the heart response to ICH.

Detrimental consequences of brain injury on peripheral cells

Acute brain injury and brain death exert detrimental effects on peripheral host cells. Brain-induced impairment of immune function makes patients more vulnerable to infections that are a major cause of morbidity and mortality after stroke, trauma, or subarachnoid hemorrhage (SAH). Systemic inflammation and organ dysfunction are other harmful consequences of CNS injury. Brain death, the most severe consequence of brain injury, causes inflammatory changes in peripheral organs that can contribute to the inferior outcome of organs transplanted from brain-dead donors. Understanding of the mechanisms underlying the detrimental effects of brain injury on peripheral organs remains incomplete. However, it appears that sympathetic nervous system (SNS)-activation contributes to elicit both inflammation and immunodepression. Indeed, norepinephrine (NE)-induced production of chemokines in liver and other organs likely participates in local and systemic inflammatory changes. Conversely, catecholamine-stimulated interleukin-10 (IL-10) production by blood monocytes exerts immunosuppressive effects. Activation of the hypothalamic-pituitary-adrenal axis (HPA) by increased inflammatory cytokines within the brain is a significant component in the CNS-induced immune function inhibition. Non-neurologic consequences of brain injury show impressive similarities regardless of the brain insult and appear to depend on altered neuroimmune circuits. Modulation of these circuits could reduce extra-brain damage and improve patient outcome in both vascular and traumatic brain injury.