Cardiac Dysfunctions in Neurocritical Care

Authors:

Umair Hamid MD,

Antony Thomas

Introduction

• Studies have indicated that patients with Traumatic or Atraumatic, brain injury are more prone to develop cardiac dysfunction within their hospital stay

• Cardiac Dysfunctions if developed are linked to increased mortality as well as short term and long term complications.

• Stroke related cardiac dysfunctions can happen, even in the absence of an overt heart disease

• The severity of brain injury correlates with the severity of cardiac dysfunction.

• In this chapter, we will review the basis as well as prevention of these dysfunctions

• The point to note here is that data on this topic is still scarce and the recommendations are still not as strong

Neuroanatomy

Intrinsic Cardiac Autonomic Control

• Sensory receptors in the heart are distributed throughout myocardial, pericardial, and epicardial tissue and at the junction of atria and great veins.

• Transmission through vagal afferent from above mentioned receptors to nucleus of solitary tract in the medulla

• Intrinsic nervous system of heart also plays role in autonomic control apart from CNS involvement called the cardiac ganglionic plexus (CGP).

• CGP is dominantly cholinergic; main neuromodulators involved are norepinephrine, epinephrine, acetylcholine, nitric oxide (NO), vasoactive intestinal peptide (VIP), neuropeptide Y, and intermedin.

Extrinsic Nerve Supply to Heart

• Parasympathetic nerve supply to heart has its preganglionic neurons located dominantly in nucleus ambiguus and lesser extent in dorsal medial nucleus of vagus nerve

• Sympathetic nerve supply to the heart arises from cardiac plexus, a bundle of nerves at arch of aorta.

• These nerves in plexus are post ganglionic projections arise from paravertebral sympathetic ganglions.

• Paravertebral sympathetic ganglions which receive inputs from higher centers exit CNS via upper 5 T-spine segments as preganglionic fibers.

• Insular cortex damage is associated with arrythmia, disruption in diurnal blood pressure variation, myocardial injury, and breathing disorders during sleep.

• Cardiovascular autonomic dysfunction is mainly related to increased sympathetic activity via the right hemisphere of the insular cortex

• Impaired autonomic cardiac control may occur following injury to brain regions such as the prefrontal cortex. For example, using a combination of electroencephalographic dynamics and instantaneous HR estimates to study emotional processing and cardiovascular autonomic responses in brain areas such as the prefrontal cortex and amygdala infract

• Interomediolateral column at T1-T5 is modulated by rostral ventrolateral medulla and paraventricular nucleus of hypothalamus.

• The involvement of brainstem in cardiac dysfunction has already been discussed in this chapter

A significant correlation was established between the clinical manifestations of brainstem compression and sinus arrhythmias, multifocal premature ventricular contractions, couplets, and ventricular tachycardias. An explanation for this correlation may be found in the localization of the autonomous cardiovascular centers in the hypothalamus and brainstem. Transtentorial herniation frequently leads to a bilateral lesion of these structures. However, the cardiac arrhythmias are only a partial phenomenon within a complex cardiovascular reaction.

Pathophysiology

• Sympathetic Over dominance
• Sympathetic over dominance can cause excess catecholamine concentration at the nerve terminals
• Etiology is focal damage or dysfunction of CNS structures controlling autonomic outflow
• Increased cAMP activation and ER Dysfunction → Calcium influx → Altered actin myosin interaction → altered myocardial contraction (consistent contraction) → Disturbance of rate and rhythm + Myocardial necrosis
• Increased K+ Outflow through delayed rectifiers > Shortening APD and increasing heterogeneity☆ → Disturbance of rate and rhythm + Myocardial necrosis
• Sustained increase in SVR > decreased endothelial vasodilator agents → Myocardial ischemia
• ☆Further explanation
• Heart rate = Action Potential Duration + Diastolic Interval(DI).
• Increased sympathetic dominance will shorten both APD as well as DI.
• Shortening of DI has a separate effect on APD, as through negative Feedback, in order to control Heart Rate, it will prolong APD in next cycle. This phenomenon of APD dependency on DI is known as Restitution of APD.
• This alternative short and long APD, is known as AP Alternans, and increases the susceptibility to arrhythmias.
• AP duration can be prolonged to the extent that a new stimulus may arise while myocardial cells are still in refractory period of AP → malignant arrythmia (this process corresponds to QT prolongation

• Activation of HPA + Other factors:
• Activation of HPA → Cortisol + Inflammatory mediators → Increased myocardial centrality + Increased oxidative stress + Increased vascular contractility → Myocardial necrosis + Coronary demand ischemia.
• Several Factors lead to sympathetic over dominance and increased activation of HPA
• Structural damage
• Excessive stimulation
• Mental stress
💡
Trigeminocardiac Reflex is a common cause of hemodynamic disturbance during supratentorial surgery. It manifests as bradycardia and hypotension during stimulation of any of the branches of the trigeminal nerve. It can also be associated with asystole, gastric hypermotility, and apnea.
Source: Ijaz, M. K. Brainstem Reflexes During Neurosurgery: An Overview.

Table 1: Effects of Neurotransmitters on the Heart

Etiology & Classification

• Cardiac Dysfunctions can be classified as follows

Table 2: Classification of Cardiac Dysfunctions

Table 3: Prognostic Importance of Cardiac Dysfunction

Clinical Syndromes

Impaired Electrical Activity of Heart

• QTc prolongation in most common; high mortality seen in patients with QTc seen in lead V6

• Abnormal T-waves or "Cerebral T-waves": T-wave inversion ≥5 mm in depth in ≥4 contiguous precordial leads

Cardiac Arrest and Sudden Death

• Most commonly seen in acute aneurysmal SAH patients

• In ischemic type, more commonly seen in subacute or delayed phase of stroke.

• SUDEP (Sudden Unexpected Death in Epilepsy) seen with seizures has 1.2 per 1000 patients per year.

Stress Cardiomyopathies

• Stress cardiomyopathy first described in 1980 as myofibrillar necrotic lesions of heart found at autopsy of physical assault patients but no other internal organ injury

• Acute chest pain presentation temporally related to emotional stress

• Ventriculography showed apical and diaphragmatic akinesia along with hyperkinesia of basal segment resulting in apical ballooning

• Peculiar shape of myocardium (see below) was similar to 'Takotsubu' or Octopus trapping pot.

Figure 1: Takotsubo Cardiomyopathy

Neurogenic Stunned Myocardium(NSM)

• Defined as acute left ventricular dysfunction triggered by acute neurologic condition.

• Can present with left ventricular ejection fraction reduction significantly or normal left ventricular EF with regional wall motion abnormality; can been seen commonly after acute subarachnoid hemorrhage

• Other risk factors for NSM in acute SAH include female sex, ST elevation anterior leads, high troponin, cocaine or meth use history, or posterior circulation aneurysms.

Risk Factors:

• Preexisting heart disease

• Increased burden of cardiac risk factors i.e. smoking, obesity, hypertension, sedentary life style, high cholesterol etc.

• Factors that increase electrical instability
• Obstructive sleep apnea
• Diabetes
• Electrolyte imbalance
• Drugs that prolong QTc

Prevention and Therapeutic Options

• Balance electrolyte disturbances

• Avoid QTc prolonging drugs

• Factors increasing coronary demand such as hypertension, tachyarrhythmia should be aggressively managed

• Beta blockers and renin angiotensin pathway inhibitors might work in some cases

• Centrally acting sympathetic blockers such as clonidine has shown to prevent cardiac dysfunctions

• Vagal nerve stimulation

• Inotropes such as dobutamine is preferred than vasopressors in management of cardiac dysfunctions after Stroke.

• Several other novel treatments are being studied.

Further Reading

• Raad, B., & Sila, C. (2011). Cardiac manifestations of neurologic disorders. CONTINUUM: Lifelong Learning in Neurology, 17(1), 13-26.

• Ibrahim, M. S., Samuel, B., Mohamed, W., & Suchdev, K. (2019). Cardiac dysfunction in neurocritical care: an autonomic perspective. Neurocritical care, 30(3), 508-521.

References

• Krishnamoorthy, V., Mackensen, G. B., Gibbons, E. F., & Vavilala, M. S. (2016). Cardiac dysfunction after neurologic injury: what do we know and where are we going?. Chest, 149(5), 1325-1331.

• Tahsili-Fahadan, P., & Geocadin, R. G. (2017). Heart–brain axis: effects of neurologic injury on cardiovascular function. Circulation research, 120(3), 559-572.

• van der Bilt, I., Hasan, D., van den Brink, R., Cramer, M. J., van der Jagt, M., van Kooten, F., ... & Rinkel, G. (2014). Cardiac dysfunction after aneurysmal subarachnoid hemorrhage: relationship with outcome. Neurology, 82(4), 351-358.

• Krishnamoorthy, V., Sharma, D., Prathep, S., & Vavilala, M. S. (2013). Myocardial dysfunction in acute traumatic brain injury relieved by surgical decompression. Case reports in anesthesiology, 2013

• S. Oppenheimer and D. Cechetto, “The insular cortex and the regulation of cardiac function,” Comprehensive Physiology, vol. 6, no. 2, pp. 1081–133, 2016.

• G. Orlandi, S. Fanucchi, G. Strata, L. Pataleo, L. Landucci Pellegrini et al., “Transient autonomic nervous system dysfunction during hyperacute stroke,” Acta Neurologica Scandinavica, vol. 102, no. 5, pp. 317–321, 2000.

• G. Valenza, A. Greco, C. Gentili, A. Lanata, L. Sebastiani, D. Menicucci et al., “Combining electroencephalographic activity and instantaneous heart rate for assessing brain-heart dynamics during visual emotional elicitation in healthy subjects,” Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, vol. 374, no. 2067, 2016.