What is the relationship between acute CNS events and cardiovascular abnormalities?
CNS events can induce cardiac abnormalities in EKG morphology and rhythm. Most commonly, these abnormalities involve the T wave (diffuse, deep inversions). Minor ST segment elevation have also been reported in leads with abnormal T waves. T wave asymmetric, characteristic outward bulge in the ascending portion. ST elevation usually less noticeable, and <3mm in most instances. T inversions are more pronounce din midprecordial and lateral precordial leads. May be found to a lesser extent in limb leads. Other EKG features in acute CNS injury include prominent U waves and QT prolongation.
Explanation for EKG findings – may involve CNS-mediated increases in sympathetic adn vagal tone, as well as actual myocardial damaage termed contraction band necrosi.
EKG changes with these disease processes can include ST segment depression, T wave inversion, PR shortening, QT prolongation, accentuation of U wave, bradyarrhythmia, and tachyarrhythmia (both ventricular and supraventricular). Derangement of autonomic nervous system activity may be responsible for these.
CNS modulates cardiac function via two pathways:
- indirect effect via humoral mediators (E and NE)
- direct effect via afferent and efferent connections with SNS and pSNS
Damage to hypothalamus may be the primary cause of autonomic dysfunction.
Hypothalamic dysfunction –> excessive humoral catecholamine production and autonomic tone –> HTN, inc cardiac O2 demand, vasospasm, ??direct toxic insult to cells –> subendocardial ischemia, microhemorrahges, focal myonecrosis –> EKG changes / enzymologic and histopathologic changes
Classic EKG changes with SAH
- first described by Byer (1947)
- symmetric, deep T-wave inversion with QT prolongation
- EKG changes seen in 72% of SAH
- arrhythmias in 91% of cases, 41% of which were serious
- subendocardial damage with myocytolysis, myofibrillar degeneration, fuchsinophilic degeneration
- CPK elevations in 40-50%
- focal or global wall motion abnormalities in ~50%
Most common EKG morphologic abnormalities associated with SAH:
Arrythmias associated with SAH:
EKG changes with acute thromboembolic stroke
- morphologic changes
- QT interval prolongation
- ST segment, and T wave abnormalities
- prominent U waves
- Rhythm abnormalities
- atrial fibrillation
- sinus tachycardia
- premature ventricular contractions
- premature atrial contractions
- sinus bradycardia + increased SBP + widened pulse pressure
- EKG changes include prominent U waves, ST segment changes, notched T waves, and prolongation of the QT interval
- result of compressive forces on the brainstem and diencephalic structures –> induces vagal and sympathetic discharges that can trigger either bradycardias or supravent / ventricular tachy-dysrhythmias
Perron, Andrew D., and William J. Brady. “Electrocardiographic Manifestations Of CNS Events”. The American Journal of Emergency Medicine 18.6 (2000): 715-720. Web.