Myocardial lesions following experimental intracranial hemorrhage: prevention with propranolol

Early cardiovascular function and associated hemodynamics in adults with isolated moderate-severe traumatic brain injury: A pilot study

BACKGROUND

While cardiac dysfunction has been described following traumatic brain injury (TBI), its association with systemic and cerebral hemodynamics is not known. We examined the contemporaneous relationship between early cardiac function with systemic and cerebral hemodynamic parameters after moderate-severe TBI.

METHODS

Bedside transthoracic echocardiography (TTE) and transcranial Doppler (TCD) ultrasonography were performed within 24 h in patients > 18 years with isolated moderate-severe TBI. Systemic hemodynamic parameters were quantified using routine monitoring [heart rate and mean arterial pressures (MAP)] and calculation from echocardiographic data [stroke volume index (SVI), cardiac index (CI), and systemic vascular resistance index (SVRI)]. Systolic dysfunction was defined using TTE as global longitudinal strain (GLS) > -16%. Mean middle cerebral artery velocity (FVm) was the measure of cerebral hemodynamics and quantified using TCD.

RESULTS

Among 15 patients [mean age 43 ± 13 years, GCS 5 ± 3, 73% male], 15 TTE and 15 TCD exams were performed simultaneously. Five (33%) patients had systolic dysfunction, with significantly worse GLS (median [IQR] -12.1% [-14.1, -12] vs. -19.1% [-19.9, -17.7], p = 0.004). Median (IQR) MAP was 97 (89, 107) mmHg, SVI (29.0 [20.5, 31.0] mL m^-2), and CI (2.83 [2.05, 3.10] L/min m^-2) were low to normal, while SVRI (2704 dyne sec/cm⁵ m^-2 [2210, 4084]) was normal to high. None of the patients had abnormal TCDs. Higher GLS (reduced systolic function) was associated with lower SVI (r² = 0.274, p = 0.03) but not other parameters.

CONCLUSION

Systemic hemodynamic parameters were consistent with an early catecholamine-excess state. While reduced systolic function was associated with lower SVI, there was no relationship with reduced cerebral perfusion, possibly due to normal MAP.

Danhong Injection Protects Against Hypertension-Induced Renal Injury Via Down-Regulation of Myoglobin Expression in Spontaneously Hypertensive Rats

BACKGROUND/AIMS

High blood pressure is a major risk factor for chronic kidney disease. Currently, single-target anti-hypertensive drugs are not designed for high blood pressure-related organ damages. Danhong injection (DHI), made from the aqueous extracts of Radix Salviae miltiorrhizae and Flos Carthamus tinctorius, has various pharmacological effects, including BP lowering in SHR, mediated by the reduction of vascular remodeling and the up-regulation of Kallikrein-kinin system published recently by our team, yet if it renders renal protection remains unknown. The current study demonstrated a protective role of DHI in renal injury caused by hypertension and identified its molecular targets in the kidney of spontaneously hypertensive rats (SHR).

METHODS

Adult SHR and age/gender-matched normotensive Wistar-Kyoto (WKY) rats were treated with DHI, Losartan, or saline for 4 weeks. Serum levels of Creatinine (CRE), Micro-albumin (mAlb), Beta2-microglobulin (β2-MG), and Uric acid (UA) were detected using ELISA kits. Renal pathology was examined by hematoxylin and Eosin (H&E) stains. Microarray analysis was performed on kidney tissues, and gene expression changes were validated by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analyses.

RESULTS

Renal histopathological scores showed that SHR exhibited serious kidney injury compared to normotensive WKY rats. The intervention with DHI potently suppressed the renal injury biomarker (KIM-1) and kidney lesions compared to the untreated hypertensive subjects. Microarray analysis revealed that among the 124 genes that were differentially expressed by DHI treatment in SHR kidney, down-regulation of renal myoglobin (Mb) gene was the most prominent and was subsequently confirmed by qRT-PCR and Western blot analysis.

CONCLUSION

Hypertension-induced renal injury in SHR may be alleviated by DHI in part by local suppression of Kidney injury molecule-1 and down-regulation of Myoglobin. However, if this effect is independent of the known anti-hypertensive action of DHI in blood vessel remains to be determined.

Hypertension After Severe Traumatic Brain Injury: Friend or Foe?

Traumatic brain injury (TBI) is a major public health problem, with severe TBI contributing to a large number of deaths and disability worldwide. Early hypotension has been linked with poor outcomes following severe TBI, and guidelines suggest early and aggressive management of hypotension after TBI. Despite these recommendations, no guidelines exist for the management of hypertension after severe TBI, although observational data suggests that early hypertension is also associated with an increased risk of mortality after severe TBI. The purpose of this review is to discuss the underlying pathophysiology of hypertension after TBI, provide an overview of the current clinical data on early hypertension after TBI, and discuss future research that should test the benefits and harms of treating high blood pressure in TBI patients.

Brain-Heart Interaction: Cardiac Complications After Stroke

Neurocardiology is an emerging specialty that addresses the interaction between the brain and the heart, that is, the effects of cardiac injury on the brain and the effects of brain injury on the heart. This review article focuses on cardiac dysfunction in the setting of stroke such as ischemic stroke, brain hemorrhage, and subarachnoid hemorrhage. The majority of post-stroke deaths are attributed to neurological damage, and cardiovascular complications are the second leading cause of post-stroke mortality. Accumulating clinical and experimental evidence suggests a causal relationship between brain damage and heart dysfunction. Thus, it is important to determine whether cardiac dysfunction is triggered by stroke, is an unrelated complication, or is the underlying cause of stroke. Stroke-induced cardiac damage may lead to fatality or potentially lifelong cardiac problems (such as heart failure), or to mild and recoverable damage such as neurogenic stress cardiomyopathy and Takotsubo cardiomyopathy. The role of location and lateralization of brain lesions after stroke in brain-heart interaction; clinical biomarkers and manifestations of cardiac complications; and underlying mechanisms of brain-heart interaction after stroke, such as the hypothalamic-pituitary-adrenal axis; catecholamine surge; sympathetic and parasympathetic regulation; microvesicles; microRNAs; gut microbiome, immunoresponse, and systemic inflammation, are discussed.

Association of Early Hemodynamic Profile and the Development of Systolic Dysfunction Following Traumatic Brain Injury

BACKGROUND

While systolic dysfunction has been observed following traumatic brain injury (TBI), the relationship between early hemodynamics and the development of systolic dysfunction has not been investigated. Our study aimed to determine the early hemodynamic profile that is associated with the development of systolic dysfunction after TBI.

METHODS

We conducted a prospective cohort study among patients under 65 years old without cardiac comorbidities who sustained moderate-severe TBI. Transthoracic echocardiography was performed within the first day after TBI to assess for systolic dysfunction. Hourly systolic blood pressure (SBP), mean arterial pressure (MAP), heart rate, and confounding clinical variables (sedatives, fluid balance, vasopressors, and osmotherapy) were collected during the first 24 h following admission. Multivariable linear mixed models assessed the early hemodynamic profile in patients who developed systolic dysfunction, compared to patients who did not develop systolic dysfunction.

RESULTS

Thirty-two patients were included, and 7 (22 %) developed systolic dysfunction after TBI. Patients who developed systolic dysfunction experienced early elevation of SBP, MAP, and heart rate, compared to patients who did not develop systolic dysfunction (p < 0.01 for all comparisons). Patients who developed systolic dysfunction experienced a greater rate of decrease in SBP [-10.2 mmHg (95 % CI -16.1, -4.2)] and MAP [-9.1 mmHg (95 % CI -13.9, -4.3)] over the first day of hospitalization, compared to patients who did not develop systolic dysfunction (p < 0.01 for both comparisons). All sensitivity analyses revealed no substantial changes from the primary model.

CONCLUSIONS

Patients who develop systolic dysfunction following TBI have a distinctive hemodynamic profile, with early hypertension and tachycardia, followed by a decrease in blood pressure over the first day after TBI. This profile suggests an early maladaptive catecholamine-excess state as a potential underlying mechanism of TBI-induced systolic dysfunction.

Cardiac Arrhythmias and Abnormal Electrocardiograms After Acute Stroke

Cardiac arrhythmias and electrocardiogram (ECG) abnormalities occur frequently but are often underrecognized after strokes. Acute ischemic and hemorrhagic strokes in some particular area of brain can disrupt central autonomic control of the heart, precipitating cardiac arrhythmias, ECG abnormalities, myocardial injury and sometimes sudden death. Identification of high-risk patients after acute stroke is important to arrange appropriate cardiac monitoring and effective management of arrhythmias, and to prevent cardiac morbidity and mortality. More studies are needed to better clarify pathogenesis, localization of areas associated with arrhythmias and practical management of arrhythmias and abnormal ECGs after acute stroke.

Cardiac Dysfunction After Neurologic Injury: What Do We Know and Where Are We Going?

Recent literature has implicated severe neurologic injuries, such as aneurysmal subarachnoid hemorrhage, as a cause of cardiac dysfunction, impaired hemodynamic function, and poor outcomes. Mechanistic links between the brain and the heart have been explored in detail over the past several decades, and catecholamine excess, neuroendocrine dysfunction, and unchecked inflammation all likely contribute to the pathophysiologic process. Although cardiac dysfunction has also been described in other disease paradigms, including septic shock and thermal injury, there is likely a common underlying pathophysiology. In this review, we will examine the pathophysiology of cardiac dysfunction after neurologic injury, discuss the evidence surrounding cardiac dysfunction after different neurologic injuries, and suggest future research goals to gain knowledge and improve outcomes in this patient population.

Stress-induced cardiomyopathy

OBJECTIVES

Reversible stress-induced cardiac dysfunction is frequently seen as a complication of a multitude of acute stress states, in particular neurologic injuries. This dysfunction may be difficult to distinguish between that caused by myocardial ischemia and may impact both the treatment strategies and prognosis of the underlying condition. Critical care practitioners should have an understanding of the epidemiology, pathophysiology, clinical characteristics, precipitating conditions, differential diagnosis, and proposed treatments for stress-induced cardiomyopathy.

DATA SOURCES

MEDLINE database search conducted from inception to August 2014, including the search terms "tako-tsubo," "stress-induced cardiomyopathy," "neurogenic cardiomyopathy," "neurogenic stress cardiomyopathy," and "transient left ventricular apical ballooning syndrome". In addition, references from pertinent articles were used for a secondary search.

STUDY SELECTION AND DATA EXTRACTION

After review of peer-reviewed original scientific articles, guidelines, and reviews resulting from the literature search described above, we made final selections for included references and data based on relevance and author consensus.

DATA SYNTHESIS

Stress-induced cardiomyopathy occurs most commonly in postmenopausal women. It can be precipitated by emotional stress, neurologic injury, and numerous other stress states. Patients may present with symptoms indistinguishable from acute coronary syndrome or with electrocardiogram changes and wall motion abnormalities on echocardiogram following neurologic injury. Nearly all patients will have an elevated cardiac troponin. The underlying etiology is likely related to release of catecholamines, both locally in the myocardium and in the circulation. Differential diagnosis includes myocardial infarction, myocarditis, neurogenic pulmonary edema, and nonischemic cardiomyopathy. Although the natural course of stress-induced cardiomyopathy is resolution, treatment strategies include sympathetic blockade and supportive care.

CONCLUSIONS

Stress-induced cardiomyopathy may mimic myocardial infarction and is an important condition to recognize in patients with underlying stress states, particularly neurologic injuries.

Central dexmedetomidine attenuates cardiac dysfunction in a rodent model of intracranial hypertension

PURPOSE

To determine if central sympathetic blockade by dexmedetomidine, a selective alpha(2) adrenergic receptor agonist, prevents cardiac dysfunction associated with intracranial hypertension (ICH) in a rat model.

METHODS

Following intracisternal administration of dexmedetomidine (1 microg.microL(-1), 10 microL volume) or the stereoisomer levomedetomidine (1 microg.microL(-l), 10 microL volume) in halothane-anesthetized rats, a subdural balloon catheter was inflated for 60 sec to produce ICH. Intracranial pressure, hemodynamic, left ventricular (LV) pressures and electrocardiographic (ECG) changes were recorded. Plasma and myocardial catecholamines and malondialdehyde (MDA) levels were measured.

RESULTS

After levomedetomidine administration, subdural balloon inflation precipitated an increase in mean arterial pressure (149 +/- 33% of baseline), heart rate (122 +/- 19% of baseline), LV systolic pressure (LVP), LV end-diastolic pressure (LVEDP), LV developed pressure (LVDP), LV dP/dtmax and rate pressure product (RPP) (132 +/- 19%, 260 +/- 142%, 119 +/- 15%, 126 +/- 24% and 146 +/- 33% of baseline value, respectively). ICH decelerated LVP fall (tau), as tau increased from 7.75 +/- 1.1 to 14.37 +/- 4.5 msec. Moreover, plasma norepinephrine levels were elevated (169 +/- 50% of baseline) and there was the appearance of cardiac dysrhythmias and other ECG abnormalities. This response was transient and cardiac function deteriorated in a temporal manner. Intracisternal dexmedetomidine prevented the rise in plasma norepinephrine, blocked the ECG abnormalities, and preserved cardiac function. Moreover, dexmedetomidine attenuated the rise in MDA levels.

CONCLUSIONS

The results demonstrate that dexmedetomidine attenuates cardiac dysfunction associated with ICH. Our results provide evidence for the role of central sympathetic hyperactivity in the development of cardiac dysfunction associated with ICH.

The effect of total spinal anesthesia on cardiac function in a large animal model of brain death

Brain death (BD) causes cardiac dysfunction in organ donors, attributable to the catecholamine storm that occurs with raised intracerebral pressure (ICP). However the direct contribution of the spinal sympathetics has not been well described. We examined the effect of total spinal anesthesia (TSA) on cardiac function in a large animal model of BD. Eighteen pigs were allocated to 3 experimental groups: Group 1, the saline-treated control group; Group 2, TSA administered prior to BD; and Group 3, TSA administered 30 min after BD. Inflation of an intracerebral balloon-tipped catheter was used to induce BD. Ventricular function was assessed using a pressure–volume loop catheter and magnetic resonance imaging. Serum catecholamine levels were assessed with high performance liquid chromatography. Inflation of the intracerebral balloon-tipped catheter was associated with a dramatic rise in heart rate and blood pressure, along with increased concentrations of serum epinephrine and norepinephrine. This phenomenon was not observed in Group 2. In Group 1, there was a significant decline in contractility, whereas groups 2 and 3 saw no change. Group 2 had greater contractile reserve than groups 1 and 3. Our data demonstrate the central role of spinal sympathetics in the hemodynamic response to raised ICP. Further work is required to determine the utility of TSA in reversing cardiac dysfunction in BD donors.

Perioperative hypothermia (33 degrees C) does not increase the occurrence of cardiovascular events in patients undergoing cerebral aneurysm surgery: findings from the Intraoperative Hypothermia for Aneurysm Surgery Trial

BACKGROUND

Perioperative hypothermia has been reported to increase the occurrence of cardiovascular complications. By increasing the activity of sympathetic nervous system, perioperative hypothermia also has the potential to increase cardiac injury and dysfunction associated with subarachnoid hemorrhage.

METHODS

The Intraoperative Hypothermia for Aneurysm Surgery Trial randomized patients undergoing cerebral aneurysm surgery to intraoperative hypothermia (n = 499, 33.3 degrees +/- 0.8 degrees C) or normothermia (n = 501, 36.7 degrees +/- 0.5 degrees C). Cardiovascular events (hypotension, arrhythmias, vasopressor use, myocardial infarction, and others) were prospectively followed until 3-month follow-up and were compared in hypothermic and normothermic patients. A subset of 62 patients (hypothermia, n = 33; normothermia, n = 29) also had preoperative and postoperative (within 24 h) measurement of cardiac troponin-I and echocardiography to explore the association between perioperative hypothermia and subarachnoid hemorrhage-associated myocardial injury and left ventricular function.

RESULTS

There was no difference between hypothermic and normothermic patients in the occurrence of any single cardiovascular event or in composite cardiovascular events. There was no difference in mortality (6%) between groups, and there was only a single primary cardiovascular death (normothermia). There was no difference between hypothermic and normothermic patients in postoperative versus preoperative left ventricular regional wall motion or ejection fraction. Compared with preoperative values, hypothermic patients had no postoperative increase in cardiac troponin-I (median change 0.00 microg/l), whereas normothermic patients had a small postoperative increase (median change + 0.01 microg/l, P = 0.038).

CONCLUSION

In patients undergoing cerebral aneurysm surgery, perioperative hypothermia was not associated with an increased occurrence of cardiovascular events.

Improvement of Donor Myocardial Function after Treatment of Autonomic Storm During Brain Death

BACKGROUND

In experimental brain death models, autonomic storm (AS) triggers severe myocardial dysfunction, which can be attenuated by pharmacologic treatment. The aim of this study was to determine the incidence of AS in a cohort of human organ donors and to evaluate the potential interest of AS treatment on myocardial function, cardiac harvesting and transplantation.

METHODS

The cohort consisted of 152 patients. Among them, 46 patients were initially considered as potential cardiac donors (main criteria: age < 60 years, no history of cardiac disease). AS diagnosis included increased systolic arterial pressure > 200 mm Hg associated with tachycardia >140 beats/min. Heart acceptance criteria were associated creatine kinase (CK), troponin Ic, and left ventricle ejection fraction (LVEF) estimated by echocardiography and visual inspection.

RESULTS

AS was observed in 29 patients (63%). Hypertension was treated in 12 patients (esmolol n = 6, urapidil n = 5, nicardipine). Cardiac harvesting was performed in 28 donors (61%). LVEFs were significantly higher after AS treatment (no AS: 55.4 +/- 13.4%, untreated AS: 49.0 +/- 18.8%, treated AS: 63.9+ +/- 10.3%, P = 0.049). AS treatment was found to be independently associated with LVEF in > 50% of the cases (P = 0.034). Treatment of AS or the lack of AS were associated with an increased probability of successful cardiac transplantation (OR = 8.8; 95% CI 2.1-38.3, P = 0.002).

CONCLUSIONS

Treatment of hypertension during AS may attenuate brain death-induced myocardial dysfunction and increase the number of available cardiac grafts.

Cardiac troponin I release after severe scorpion envenoming by Tityus serrulatus

Eight children aged 2-9 years, with signs and symptoms of severe scorpion envenoming by Tityus serrulatus were studied. All patients showed clinical manifestations of cardiac dysfunction, with ECG and echocardiographic alteration and five developed pulmonary edema. Troponin I levels were normal in all patients on admission, except for two who arrived later, and increased thereafter, with maximum values being observed 24-36 h after the sting. The detection of TnI in patients with severe scorpion envenoming, and the observed temporal pattern and serum levels meet the criteria established for the diagnosis of acute myocardial infarction. The rapid reversibility of cardiac dysfunction, together with the normalization of the enzymatic, ECG and echocardiographic data, indicates the occurrence of an acute myocardial lesion without underlying or associated coronary disease.

Intrathecal lidocaine prevents cardiovascular collapse and neurogenic pulmonary edema in a rat model of acute intracranial hypertension

Sympathetic hyperactivity during sudden intracranial hypertension leads to cardiovascular instability, myocardial dysfunction, and neurogenic pulmonary edema. Because spinal anesthesia is associated with sympatholysis, we investigated the protective effects of intrathecal lidocaine in a rodent model. Halothane-anesthetized rats were given a 10-microL intrathecal injection of saline (n = 10) or lidocaine 1% (n = 6). A subdural balloon catheter was inflated for 60 s to produce intracranial hypertension. Hemodynamics were monitored, and hearts and lungs were harvested for histological examination. In Saline versus Lidocaine-Treated rats, peak mean arterial blood pressure during balloon inflation was 115 +/- 4 mm Hg versus 78 +/- 8 mm Hg (P < 0.05), mean arterial blood pressure 30 min after balloon deflation was 47 +/- 2 mm Hg versus 67 +/- 3 mm Hg (P < 0.05), and lung weight was 1.54 +/- 0.03 g versus 1.41 +/- 0.04 g (P < 0.05), respectively. Cardiac dysrhythmias and electrocardiographic changes were more frequent in the Saline-Treated group (P < 0.05). Saline-Treated rats had extensive, hemorrhagic pulmonary edema, whereas the Lidocaine-Treated rats had only patchy areas of lung abnormality. Histological changes in the myocardium were rare, and no difference was found between the two groups. We conclude that intrathecal lidocaine prevents cardiovascular collapse and neurogenic pulmonary edema in a rat model of acute intracranial hypertension.

IMPLICATIONS

In a rat model of intracranial balloon inflation, intrathecal lidocaine prevented cardiovascular collapse and neurogenic pulmonary edema. Descending neural pathways are involved in the development of cardiopulmonary complications associated with acute intracranial hypertension.

Regional myocardial perfusion after experimental subarachnoid hemorrhage

BACKGROUND AND PURPOSE

The pathophysiology of cardiac injury after subarachnoid hemorrhage (SAH) remains controversial. Data from animal models suggest that catecholamine-mediated injury is the most likely cause of cardiac injury after SAH. However, researchers also have proposed myocardial ischemia to be the underlying cause, as a result of coronary artery disease, coronary artery spasm, or hypertension and tachycardia. To test the hypothesis that SAH-induced cardiac injury occurs in the absence of myocardial hypoperfusion, we developed an experimental canine model that reproduces the clinical and pathological cardiac lesions of SAH and defines the epicardial and microvascular coronary circulation.

METHODS

Serial ECG, hemodynamic measurements, coronary angiography, regional myocardial blood flow measurements by radiolabeled microspheres, 2D echocardiography, and myocardial contrast echocardiography were performed in 9 dogs with experimental SAH and 5 controls.

RESULTS

Regional wall motion abnormalities were identified in 8 of 9 SAH dogs and 1 of 5 controls (Fisher's Exact Test, P=0.02) but no evidence was seen of coronary artery disease or spasm by coronary angiography and of significant myocardial hypoperfusion by either regional myocardial blood flow or myocardial contrast echocardiography.

CONCLUSIONS

In this experimental model of SAH, a unique form of regional left ventricular dysfunction occurs in the absence of myocardial hypoperfusion. Future studies are justified to determine the cause of cardiac injury after SAH.

Concurrent subarachnoid haemorrhage and myocardial injury

PURPOSE

Subarachnoid haemorrhage is frequently associated with myocardial injury and dysfunction. This report describes such a case, reviews the understanding of this phenomenon, and discusses the implications for timing of surgical clipping of intracranial aneurysm in patients with concurrent myocardial damage.

CLINICAL FEATURES

A 64-yr-old women presented with syncope and congestive heart failure. A diagnosis of subarachnoid haemorrhage was made three days following the initial diagnosis of myocardial infarction. The patient presented for clipping of an intracranial aneurysm on day 36, after her cardiac status had stabilized. No new myocardial ischaemic events occurred, either intra-operatively or post-operatively. Ultimate neurological recovery was poor.

CONCLUSIONS

This case report demonstrates four important aspects of the clinical course of patients with concurrent subarachnoid haemorrhage and myocardial damage: 1) On presentation, cardiac features may predominate, and delay diagnosis and treatment of the underlying subarachnoid haemorrhage. 2) Left ventricular dysfunction, although dramatic, is usually transient. 3) There is confusion regarding the appropriate cardiac risk assessment and management in such patients when presenting for surgery. 4) Long-term morbidity is most often related to neurological, not medical, complications.

Brain ischemia and gastric mucosal damage in spontaneously hypertensive rats: the role of arterial vagal adrenoceptors

Brain ischemia is often accompanied by acute gastric lesions. To clarify the underlying mechanism, the influence of acute ischemic insult to the brain on gastric hemodynamics and mucosal integrity was examined in spontaneously hypertensive rats. One hour after brain ischemia, gastric mucosal blood flow decreased to 71% of the preischemic levels in the control rats but was preserved significantly better, at 94 and 108%, in the prazosin-treated and guanethidine-treated rats, respectively. Vagotomy almost abolished the decrease in gastric mucosal blood flow during cerebral ischemia. Intragastric 0.6 N hydrochloric acid administered just after reperfusion induced more severe hemorrhagic ulcers in the control than in the prazosin-treated and vagotomized groups. These results suggest that noradrenergic neurons acting through alpha1-adrenoceptors contributes to the decrease in gastric mucosal blood flow, and the subsequent disturbed integrity of the gastric mucosa, through the vagal adrenergic pathway during brain ischemia in spontaneously hypertensive rats.

Hormonal and hemodynamic changes in a validated animal model of brain death

OBJECTIVE

To examine the hormonal and hemodynamic changes in a validated animal model of brain death.

DESIGN

Prospective, controlled study.

SETTING

Experimental research laboratory.

SUBJECTS

Adult male mongrel dogs (n = 10).

INTERVENTIONS

Brain death was induced by inflation of a subdural balloon in ten mongrel dogs weighing 23 to 30 kg and validated neuropathologically. The hearts were instrumented with micromanometers and ultrasonic flow probes to measure cardiovascular changes. No inotropic or vasoactive support was given. Hemodynamic stability was maintained with intravenous fluids. Blood samples and hemodynamic readings were collected before and after the induction of brain death.

MEASUREMENTS AND MAIN RESULTS

A Cushing reflex, followed by a hyperdynamic response and diabetes insipidus, occurred in every animal following brain death. Mean arterial pressure, heart rate, contractility, and cardiac output increased to > 350 mm Hg, 230 beats/min, 4200 mm Hg/sec, and 2.8 L/min, respectively, at the peak of this phenomenon before returning to baseline. A plasma catecholamine surge was observed in every animal 15 mins after brain death, while the circulating concentrations of the pituitary gland hormones vasopressin and adrenocorticotrophic hormone decreased significantly after 15 and 45 mins of brain death, respectively, and continued to decrease throughout the experiments. Circulating triiodothyronine, thyroxine, and glucagon concentrations decreased significantly (p < .01) from 0.58 +/- 0.05 ng/mL, 2.20 +/- 0.15 micrograms/dL, and 49.7 +/- 9.1 pg/mL, respectively, to 0.34 +/- 0.03 ng/mL, 1.14 +/- 1.14 micrograms/dL, and 6.9 +/- 1.4 pg/mL, respectively, 420 mins after brain death. The hematocrit increased significantly 15 mins after brain death and then gradually decreased throughout the duration of the experiments.

CONCLUSIONS

In a validated animal model of brain death, significant decreases in the circulating concentrations of stress hormones, as well as hemodynamic instability, occurred after brain death. Measurements of plasma adrenocorticotrophic hormone and vasopressin values may be useful as diagnostic predictors of brain death. Furthermore, the observed changes may contribute to organ dysfunction after brain death and may necessitate hormonal as well as inotropic and vasoactive support to maintain donor organ function in the clinical setting.

Nitric oxide in brain death related cardiovascular dysfunction

PURPOSE

Nitric oxide (NO) is a major regulator of vascular tone, blood pressure, and blood flow, and plays a significant role in disease states associated with hemodynamic alterations. However, the role of NO in association with the effects of brain death (BD) has not yet been evaluated.

METHODS

In 17 mongrel dogs (23 to 31 kg), right atrial serum measurements of nitrite and L-arginine as well as NO ex vivo tissue nitrite extraction were performed at baseline (0), and 120, 240, and 360 minutes after BD. The hearts were instrumented with micromanometers, transonic flow probes, and ultrasonic dimension transducers to determine systolic function and to analyze the pulmonary vasculature flow characteristics by Fourier analysis. Brain death was induced by inflation of a subdurally placed balloon and validated neuropathologically. The results are expressed as mean and standard error of the mean (+/- SEM) (P < .05, paired t-test).

RESULTS

Right and left ventricular function deteriorated significantly (P < .001) by 37% (+/- 10) and 22% (+/- 7) respectively following BD. Pulmonary and systemic vascular resistance as well as pulmonary impedance decreased significantly over 6 hours after BD. Pulsatile flow, a potent stimulant of NO release, converted significantly to more steady flow. Myocardial NO extraction values remained unchanged after BD and serum L-arginine decreased from 12.84 mu g/L (+/- 0.60) to 11.77 mu g/L (+/- 0.55).

CONCLUSIONS

The decreases in pulmonary and systemic vascular resistance, pulmonary impedance, and cardiac function associated with BD are not related to major changes in the NO pathway. NO may not play a key role in the early changes after BD.

Myocardial beta-adrenergic receptor function and high-energy phosphates in brain death--related cardiac dysfunction

BACKGROUND

Cardiac failure remains an important problem after heart transplantation and may be associated with events that occur during brain death (BD) before transplantation. In this study, cardiac function is studied after BD, and biochemical evaluation of myocardial high-energy phosphates and the beta-adrenergic receptor system is presented.

METHODS AND RESULTS

The hearts of 17 mongrel dogs (23 to 31 kg) were instrumented with flow probes, micromanometers, and ultrasonic dimension transducers to measure ventricular pressure and volume relationships. In a validated canine BD model, systolic right and left ventricular (RV/LV) function was analyzed by load-insensitive measurements during caval occlusion (preload-recruitable stroke work, PRSW). The beta-adrenergic receptor (BAR) density, adenylate cyclase (AC) activity, and myocardial ATP and creatine phosphate (CP) were measured before and 6 to 7 hours after BD. Results are expressed as mean +/- SEM (*P < .05 versus baseline, paired two-tailed Student's t test). Myocardial function deteriorated significantly from baseline PRSW (RV, 22 +/- 1 erg x 10(3); LV, 75 +/- 4 erg x 10(3)) by 37 +/- 10% for the RV (P < .001) and 22 +/- 7% for the LV (P < .001). BAR density increased from 282 +/- 42 to 568 +/- 173 fmol/mg for the RV and from 291 +/- 64 to 353 +/- 56 fmol/mg for the LV. Isoproterenol-stimulated AC activity was also significantly enhanced after BD. ATP and CP, however, remained unchanged after BD compared with baseline values before BD.

CONCLUSIONS

BD causes significant systolic biventricular dysfunction. The loss of ventricular function after BD was more prominent in the right ventricle and may contribute to early postoperative RV failure in the recipient. These injuries occurred despite BAR system upregulation after BD. Global myocardial ischemia is unlikely, since ATP and CP remained normal before and after BD.

Endocrine changes and metabolic responses in a validated canine brain death model

PURPOSE

Endocrinologic and metabolic changes after brain death (BD) have not yet been investigated in a validated animal model. Therefore, the effects of BD on hormonal and metabolic function were studied in 10 dogs (23 to 31 kg).

METHODS

BD was induced by intracranial pressure increase and validated neuropathologically. Plasma concentrations of pituitary, thyroid, adrenal, and pancreatic hormones were measured pre/post BD. The results are expressed as mean (+/- SEM).

RESULTS

A Cushing reflex and diabetes insipidus occurred after BD. Elevated catecholamine levels were documented after 15 minutes whereas the pituitary gland hormones vasopressin and adrenocorticotrophic hormone (ACTH) decreased significantly after 15 and 45 minutes of BD respectively. Thyroxine, triiodothyronine, and glucagon decreased significantly (P < .01) from 0.58 ng/mL (+/- 0.05), 2.20 micrograms/dL (+/- 0.15), and 49.7 pg/mL (+/- 9.1) respectively to 0.34 ng/mL (+/- 0.03), 1.14 micrograms/dL (+/- 1.14), and 6.9 pg/mL (+/- 1.4) respectively 420 minutes after BD. The hematocrit increased significantly after BD and declined toward the end of all experiments. Metabolic acidosis occurred immediately after BD and at the end of the experiments.

CONCLUSIONS

In a simple, reproducible, and reliable animal model of BD, a catecholamine storm, vasopressin and ACTH cessation, and diabetes insipidus were consistent findings. The decrease in cortisol and vasopressin levels warrant consideration of hormonal therapy.

Electrocardiographic and echocardiographic changes associated with malignant catatonia

We describe a case of malignant catatonia manifested by catatonic symptoms, fever, hemodynamic instability, and acute neurologic decline that was associated with electrocardiographic and echocardiographic abnormalities similar to those noted in patients with other central nervous system processes. The patient's electrocardiographic and echocardiographic abnormalities resolved after successful electroconvulsive therapy for the underlying neuropsychiatric disorder. The theoretic, physiologic, and clinical significances of this case are discussed.

Successful transplantation of marginally acceptable thoracic organs

OBJECTIVE

This study evaluates the efficacy of personally inspecting marginal thoracic organ donors to expand the donor pool.

SUMMARY BACKGROUND DATA

The present donor criteria for heart and lung transplantation are very strict and result in exclusion of many potential thoracic organ donors. Due to a limited donor pool, 20-30% of patients die waiting for transplantation.

METHODS

The authors have performed a prospective study of personally inspecting marginal donor organs that previously would have been rejected by standard donor criteria.

RESULTS

Fourteen marginal hearts and eleven marginal lungs were inspected. All 14 marginal hearts and 10 of the marginal lungs were transplanted. All cardiac transplant patients did well. The mean ejection fraction of the donor hearts preoperatively was 39 +/- 11% (range 15-50%). Postoperatively, the ejection fraction of the donor hearts improved significantly to 55 +/- 3% (p < 0.002). Nine of the ten lung transplant patients did well and were operative survivors. Our donor pool expanded by 36% over the study period.

CONCLUSIONS

The present donor criteria for heart and lung transplantation are too strict. Personal inspection of marginal thoracic donor organs will help to maximize donor utilization.

Electrocardiographic changes in subarachnoid hemorrhage secondary to cerebral aneurysm. Report of 70 cases

Electrocardiographic (ECG) alterations in the course of sub-arachnoid hemorrhage (SAH) have frequently been reported. The most frequent anomalies reported were lengthening of the QT interval, very negative or positive deep T waves, elevation or depression of the ST segment and the presence of U waves. We report 70 cases of SAH secondary to rupture of intracranial aneurysm (part of a larger group of 150) with ECG changes. We review the literature with particular regard to discussion of the possible pathogenesis of ECG changes and to the way they may affect the general clinical course.

Autonomic and myocardial changes in middle cerebral artery occlusion: stroke models in the rat

Stroke models in larger animals such as the cat, dog and monkey are becoming increasingly more expensive and less readily available. However, the rat is an excellent model for focal cerebral ischemia. Rats are readily available, inexpensive and their neuroanatomy and brain function have been studied extensively. Increases in plasma catecholamines and myocardial damage have been observed in clinical stroke. We examined autonomic and myocardial changes in two rat stroke models. In one model only the middle cerebral artery was occluded (MCAO) while the other model involved occlusion of both the MCA and the common carotid artery (MCAO/CCAO). Arterial blood pressure and heart rate were monitored continuously in 25 male rats (326-430 g) that underwent one of the following procedures: (1) MCAO only; (2) MCAO/CCAO; (3) CCAO only; and (4) sham occlusions (SHAM). Arterial blood samples (0.5 ml) for radioenzymatic assay of norepinephrine (NE) and epinephrine (E) were taken twice before the occlusions and at 90 and 180 min after the occlusions. The animals were perfused at the end of the experiment and the heart removed and examined histologically. Tetrazolium salts were reacted with oxidative enzymes to delineate the region of inadequate perfusion. The mean blood pressure and pulse pressure of the SHAM, MCAO/CCAO and CCAO groups significantly declined from initial values (from an average of 78 to 53 mm Hg) during the course of the experiment. However, the mean blood pressure and pulse pressure of the MCAO rats did not change during the experiment, so that the final mean blood pressure and pulse pressure were significantly higher than in the other 3 groups. The levels of both NE and E increased significantly (NE, 1443 +/- 285.9 to 4095 +/- 929 pg/ml; E, 2402 +/- 623 to 3741 +/- 1166 pg/ml) following occlusion in the MCAO group only while the other 3 groups did not change. Four of 6 hearts in the MCAO group were abnormal, showing evidence of subendocardial hemorrhage, ischemic damage or subendocardial congestion. MCAO also resulted in a consistent region of the brain with inadequate perfusion including the insular cortex. These autonomic and myocardial changes appear to mimic some of the changes seen clinically in stroke patients and provide the first acute stroke model for studying autonomic dysfunction in the rat.

Improved myocardial oxygen utilization following propranolol infusion in adolescents with postburn hypermetabolism

The purpose of this study was to determine if propranolol (0.5 mg/kg and 1 mg/kg), administered intravenously (IV) at the height of the postburn hypermetabolic response, would decrease myocardial oxygen requirements, without adversely affecting overall oxygen delivery or total body oxygen consumption. To test this hypothesis, six nonseptic patients age 17 +/- 3 years with burns over 82% +/- 11% total body surface area were given propranolol with continuous hemodynamic monitoring. Propranolol was administered to these patients 20 +/- 15 days postburn. Two clinically derived indices of myocardial oxygen consumption, pressure-work index (PWI) and rate-pressure product (RPP), were used to estimate the energy expenditure of the working heart. Both PWI and RPP were significantly decreased from baseline after 0.5 mg/kg propranolol, 31% for PWI (P less than .001) and 30% for RPP (P less than .01). Similarly, a decrease from baseline was seen after 1.0 mg/kg propranolol, 32% for PWI (P less than .001) and 35% for RPP (P less than .01). Cardiac index (L/min/m2) demonstrated no significant change [7.4 +/- 1.1 (prepropranolol), 6.5 +/- 1.3 (after 0.5 mg/kg propranolol), and 6.8 +/- 1.0 (after 1.0 mg/kg propranolol)] and exceeded the upper limits of normal (hyperdynamic state) throughout the study. Oxygen delivery index (962 +/- 209 mL/min/m2) and oxygen consumption indices [(254 +/- 78 mL/min/m2 by Fick method and 236 +/- 78 mL/min/m2 by inspired and expired gases)] were elevated at baseline and unaffected by propranolol. The decrease in PWI and RPP was achieved mainly by propranolol's effect to lower both heart rate and BP.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of blood transfusion, dopamine, or normal saline on neurogenic shock secondary to acutely raised intracranial pressure

An experimental model to simulate acutely raised intracranial pressure due to a rapidly expanding intracranial space-occupying lesion was used to produce neurogenic shock. Forty-one rats in neurogenic shock (defined as a mean systemic arterial pressure (SAP) of less than 60 mm Hg) were subjected to various treatments to increase the mean SAP to a level of more than 80 mm Hg. The control group with neurogenic shock received no treatment, and the six treatment groups received infusions of: whole blood, packed cells, plasma, normal saline, dopamine, or a combination of dopamine and saline. Detrimental effects were observed after transfusion of packed cells or whole blood, which caused further deterioration of mean SAP. Although dopamine or the combination of dopamine and saline were both effective (p = 0.0001) for reversing hypotension, the combination was the most effective. If this rat paradigm correlates with human disease, these results indicate that, in the absence of hypovolemia, neurogenic shock due to acute intracranial hypertension should be treated with a combined transfusion of dopamine and normal saline, but not blood since the latter could have a detrimental effect.

Dopamine treatment of locally procured donor hearts: relevance on postoperative cardiac histology and function

Administration of catecholamines can lead to myocyte damage. Dopamine treatment is often used in potential cardiac donors to attain hemodynamic stability. Donor hearts exposed to dopamine are rejected or selected for transplantation without clearly defined criteria. A prospective study was undertaken to analyze the clinical relevance of dopamine-induced myocardial lesions in 25 hearts (21 male, 4 female; 15-40 years, mean: 26 +/- 7) that were later used for transplantation. Donors were divided into those who had received dopamine and those who had not. Dopamine doses ranged from 2-12.5 micrograms/kg/min (mean: 6.3 +/- 3). Time of administration was 3-26 hours (mean: 16 +/- 8). Use of dopamine was unrelated to donor electrocardiographic findings, intra- or postoperative death, or difficulty coming off by-pass. Postoperatively, filling pressures were similar in both groups of patients at 2 and 10 days postoperatively. Left ventricular ejection fraction was similar in the two groups. Dopamine requirements were significantly higher in the dopamine-treated hearts (P = 0.05). Histologic findings at first biopsy revealed infiltration and cell damage in a similar proportion of patients in both groups.

IN CONCLUSION

donor hearts exposed to dopamine can be accepted for transplantation if doses ranging from 2-12.5 micrograms/kg/min have been administered up to 24 hours.

Increased intracranial pressure elicits hypertension, increased sympathetic activity, electrocardiographic abnormalities and myocardial damage in rats

Intracranial pressure was increased in 59 rats by inflating a subdural balloon to a total mass volume of 0.3 ml. The increase in intracranial pressure ranged from 75 to greater than 500 mm Hg. With few exceptions, mean arterial pressure increased to as high as 227 mm Hg during the increase in intracranial pressure. Significant increases in plasma catecholamines, major electrocardiographic changes and a considerably shortened survival time were observed only in the rats that demonstrated an increase in mean arterial pressure greater than 50 mm Hg. A perfusion study with liquid silicone rubber (Microfil) revealed dilated irregular myocardial vessels with areas of focal constriction consistent with microvascular spasm. Histologic examination of the myocardium revealed widespread patches of contraction band necrosis and occasional contraction bands in the smooth muscle media of large coronary arteries. These observations suggest that myocardial damage after suddenly increased intracranial pressure resulted both from exposure to toxic levels of catecholamines and from myocardial reperfusion. Extension of these studies to humans suggests that a detailed assessment of myocardial function should be performed in victims of severe brain injury. Myocardial dysfunction may be a major determinant of the patient's prognosis or may render the heart unsuitable for transplantation.

Renal blood flow in acute cerebral ischemia in spontaneously hypertensive rats: effects of alpha- and beta-adrenergic blockade

The influences of acute cerebral ischemia on renal hemodynamics were examined in spontaneously hypertensive rats in which cerebral ischemia was induced by bilateral carotid artery occlusion. Renal and cerebral blood flow were measured with a hydrogen clearance technique. Either phenoxybenzamine (0.5 mg/kg body wt) or propranolol (2 mg/kg) was given i.v. immediately after ischemia was induced to examine the drugs' effects on cerebral and renal hemodynamics. One hour after ischemia, cerebral blood flow was markedly reduced to 5, 3, and almost 0% of the preischemic value in the untreated, phenoxybenzamine-treated, and propranolol-treated rats, respectively. In contrast, renal blood flow at that time was decreased to 65, 88, and 67%, respectively. The calculated renal vascular resistance was similarly increased to 151% in the untreated and 136% in the propranolol-treated rats, but decreased to 82% in the phenoxybenzamine-treated rats. The present results indicate that in acute cerebral ischemia renal blood flow was considerably decreased with concomitant increased renal vascular resistance, and that such reduction in renal blood flow was minimized by alpha-adrenergic blockade but not by beta-blockade. It is concluded that activation of the alpha-adrenergic system in acute cerebral ischemia causes renal vasoconstriction.

Subarachnoid hemorrhage: frequency and severity of cardiac arrhythmias. A survey of 70 cases studied in the acute phase

The frequency and severity of cardiac arrhythmias were studied in 70 patients with spontaneous subarachnoid hemorrhage investigated prospectively with 24-hour Holter monitoring. Patients were less than 70 years old and without clinical and/or ECG signs of previous heart disease; Holter monitoring was initiated within 48 hours of subarachnoid hemorrhage. Arrhythmias were detected in 64 of the 70 patients (91%). Twenty-nine of the 70 patients (41%) showed serious cardiac arrhythmias; malignant ventricular arrhythmias, i.e., torsade de pointe and ventricular flutter or fibrillation, occurred in 3 cases. Serious ventricular arrhythmias were associated with QTc prolongation and hypokalemia. No correlation was found between the frequency and severity of cardiac arrhythmias and the neurologic condition, the site and extent of intracranial blood on computed tomography scan, or the location of ruptured malformation. The extremely high incidence of cardiac arrhythmias, sometimes serious, in the acute period after subarachnoid hemorrhage and the absence of clinical and radiologic predictors make systematic continuous ECG monitoring compulsory to improve the overall results of subarachnoid hemorrhage, irrespective of early or delayed surgical treatment.

Holter detection of cardiac arrhythmias in intracranial subarachnoid hemorrhage

To determine the frequency and severity of cardiac arrhythmias in intracranial subarachnoid hemorrhage, 120 nonselected patients were prospectively studied by 24-hour Holter monitoring. Arrhythmias were found in 96 of 107 patients (90%) with adequate Holter recording: ventricular premature complexes in 49, nonsustained ventricular tachycardia in 5, supraventricular premature complexes in 29, paroxysmal supraventricular tachycardia or atrial fibrillation in 9, sinoatrial block and arrest in 29, second-degree atrioventricular block in 1, atrioventricular dissociation in 4 and idioventricular rhythm in 2. Life-threatening ventricular arrhythmias (torsades de pointes-type ventricular tachycardia) occurred in 4 patients, degenerating into either ventricular flutter or fibrillation in 2. ST-segment changes suggestive of acute transitory myocardial ischemia were found in 8 patients (1.5 mm or more of ST depression in 7 patients and 1.5 mm or more of ST elevation in 1 patient). The frequency and severity of arrhythmias were significantly higher in patients studied within 48 hours of subarachnoid hemorrhage; serious ventricular arrhythmias were associated with QTc prolongation more than 550 ms and with hypokalemia less than 3.5 mEq/liter. No correlation was found between age, clinical condition, site and extent of subarachnoid hemorrhage and either the occurrence or severity of arrhythmias. The results of our study indicate an extremely high incidence of arrhythmias, sometimes serious, in subarachnoid hemorrhage, especially in the first 48 hours after hemorrhage. Continuous electrocardiographic monitoring is therefore mandatory.

Prevention of myocardial injury by pretreatment with verapamil hydrochloride prior to experimental brain death: efficacy in a baboon model

Systemic and pulmonary hemodynamics were studied in two groups of Chacma baboons following the induction of brain death. Group A was a control group of 11 animals who underwent brain death. They showed significant increments of mean systemic arterial, left atrial, and pulmonary arterial pressures; of systemic vascular resistance, heart rate, and pulmonary artery blood flow; and a reduction in aortic blood flow during the induction of brain death. As a result of increased sympathetic nervous system activity, areas of myocardial cell necrosis occurred in 73% of the animals and pulmonary edema in 36%. Group B consisted of five animals that were pretreated with verapamil hydrochloride infused over a period of 30 minutes prior to the induction of brain death (mean dosage, 0.26 mg/kg). Except for a rise in heart rate, no significant changes occurred in systemic or pulmonary hemodynamics, and no myocardial or pulmonary histopathological changes were seen. These findings would indicate that verapamil hydrochloride prevents both the peripheral and central hemodynamic changes that result from increased sympathetic activity associated with the induction of brain death, and thus prevents myocardial structural damage, which may be associated with increased calcium uptake by the myocyte.

Cardiovascular regulation and lesions of the central nervous system

The central nervous system has an important role in the second-to-second regulation of cardiac activity and vasomotor tone. Central lesions that lead to a disturbance in autonomic activity tend to cause electrocardiographic and pathological evidence of myocardial damage, cardiac arrhythmias, and disturbances of arterial blood pressure regulation. To a great extent such cardiovascular disturbances result from alterations in sympathetic activity. Similar alterations in sympathetic activity can occur under conditions of emotional stress and precipitate cardiac arrhythmias that can themselves lead to the syndrome of sudden death. Experimental and clinical evidence suggests that central neural mechanisms may be involved in this important human syndrome, but no central lesion has yet been identified to account for it. Recent experimental evidence, derived from hypertension research, suggests that chemical disturbances in the central nervous system, without accompanying structural lesions, may be found to explain cardiovascular disturbances such as sudden death and hypertension.

Myocardial damage from acute cerebral lesions

Autopsy findings in 58 patients with intracranial lesions were compared with those in 50 control patients for myocardial damage, characterised by a change from a myofibrillar to a granular staining pattern, using a histochemical method for succinic dehydrogenase. Transmurally scattered foci of damaged myocardial fibres were significantly more common (p less than 0.01) in patients with intracranial lesions (62%) compared to controls (26%). No victims of sudden violent deaths showed these cardiac lesions. Focal myocardial damage required at least six hours to develop after onset of the acute neurological event and was not observed after the second week. It was associated with lesions producing a rapid increase in intracranial pressure and was usually absent in patients with slowly enlarging or small cerebral lesions. Similar myocardial changes were seen in patients in the control group dying from prolonged shock or other forms of acute circulatory or metabolic failure. The postulated mechanism of cardiac damage in these patients is increased levels of plasma catecholamines secondary to rapidly increasing intracranial pressure, irrespective of the cerebral pathology.

A pharmacological analysis of autonomic pathways mediating myocardial disturbances originating in a lateral hypothalamic area of the cat

A study was made of the mechanisms mediating autonomic changes resulting from stimulation of a site in the lateral hypothalamic area (LHA). This site, when stimulated, induced angina-like ECG disturbances similar to those observed in some cases of brain traumas. These ECG changes were often associated with other autonomic changes, such as pressor response, tachycardia (in some cases bradycardia), nictitating membrane (NM) contraction and pupillary dilatation. Most symptoms were sympathetic: they were largely abolished by spinal cord section between C1 and C2, but were not affected by vagotomy, except that bradycardia was converted to tachycardia. Adrenal catecholamines were not involved since adrenal vein ligation was without effect. Hexamethonium (5-10 mg/kg) prevented pressor response and tachycardia in most cats but only partly protected against ECG changes and NM contractions. Atropine methyl nitrate (0.2 mg/kg) abolished the remaining ECG abnormalities and NM tension. The beta-receptor antagonists, propranolol and practolol (50 micrograms/kg) completely prevented the ECG changes induced either by isoprenaline or LHA stimulation. It is concluded that the symptoms induced by LHA stimulation result from noradrenaline release in the target organs.