Answer

Neurogenic Stunned Myocardium

Discussion
Neurogenic stunned myocardium (NSM) is myocardial injury and dysfunction which takes place suddenly after different types of acute brain injury have been experienced. This may be caused by the autonomic nervous system imbalance. Unfortunately, this diagnosis is still highly confused with other cardiovascular illnesses since it is a manifestation of possible neurological illness with features of a heart disease. These neurologic events are what encourage cardiac abnormalities experienced in a patient. These events may feature strokes and seizures that lead to sympathetic actions and dysregulation of the autonomic system that will trigger myocardial injury. Its resulting presentation showcased by the patient will include increased troponin levels, improper functioning of the left ventricular system, and even ECG changes.
The findings tend to be quite similar to other cardiovascular conditions which is what triggers missed diagnosis. This is worsened by the fact that the diagnosis is reached through an exclusion method based on clinical presentation. Thus, the clinical presentation alone should not be used to efficiently distinguish between various conditions which is why further evaluation is needed. According to Kenigsberg et al. (2019), once the differentiation is achieved, it will be easier to evaluate the potential cardiac transplantation donors who have already experienced irreversible neurological damage.
After a patient suffers from stroke, the dysfunction of the autonomic system and severe cardiac issues tend to be linked to the insular cortex. This part plays an important role in the balancing of the nervous systems, which includes the cardiovascular system (Hawkes & Hocker, 2018). The insula is responsible for the control of the cardiovascular system. As Biso et al. (2017) notes, this happens through the baroreceptors which work by altering the blood pressure status and heart rate as required. Hence, whenever the insula is stimulated, the result is an alteration of the aforementioned occurrences. Also, any lesions present in the insular cortex will trigger an increase in norepinephrine release that causes the left ventricular system to dysfunction (Zahid et al., 2020). It is important to realise that whenever the insular cortex is stimulated, there will be an increased incidence of cardiovascular morbidity and mortality.
According to Ali et al. (2018), patients who suffer from neurological events such as stroke and seizures may develop NSM that may be asymptomatic for quite some time. Thus, the condition can be easily missed. However, the increased levels of troponin may be the only available sign of cardiac damage. This can be detected even when the patient is not experiencing any chest pains or showing any abnormalities on the ECG (Rimaz et al., 2019). It is argued that around 53% of patients who suffer from acute ischemic stroke also showcased increased troponin levels (Ali et al., 2018). However, out of this percentage, only 6% were actually diagnosed with myocardial infarction (Ali et al., 2018). For the patients with no obvious coronary heart disease, only 3% had increased troponin levels (Ali et al., 2018). This represents a very low percentage, showing that the troponin can be used as a reliable indicator for NSM.
Ali et al. (2018) also notes that the electrocardiographic features can also be used to properly differentiate NSM from other conditions and reach the correct diagnosis. Of all the patients suffering from cerebral infarction, about 60-90% also showcased abnormal ECG findings (Ali et al., 2018). The second most common finding is a T-wave inversion. The highly prevalent abnormal rhythm is atrial fibrillation, just before sinus tachycardia (Biso et al., 2017). Hence, as Ali et al. (2018) states, approximately 8% of the cerebral infarction patients also showcased various instances of T-wave inversions. This shows that it is also an important consideration when seeking the right diagnosis.
Learning Points
• NSM is a common condition that is also clinically impactful.
• More research is still required to refine the clinical approach taken to diagnose this condition.
• Once an effective approach can be determined, it will be easier to rule out any intrinsic cardiac injury, therefore optimizing donor candidacy after brain death.
• Increased levels of troponin, abnormal ECG findings (T wave inversion), and left ventricular system to dysfunction may be used to effectively diagnose this condition.