ECG criteria
- Deep negative T waves («cerebral T waves») in precordial leads V2–V6, often maximal in V3–V4
- T waves are wide and symmetric; depth varies and can sometimes be very large, but there is no validated quantitative threshold — the magnitude itself does not confirm the diagnosis
- Prolongation of the QT/QTc interval, which can be significant in severe cases
- ST-segment elevation or depression is possible, sometimes marked and mimicking STEMI; interpretation requires correlation with clinical presentation, serial ECGs, troponin, and echocardiography
- A prominent U wave may be present; this sign is non-specific and requires checking potassium, magnesium, heart rate, and drug therapy
- Sinus bradycardia or sinus tachycardia; other rhythm disturbances are possible
- Variable onset and gradual evolution of changes over days to weeks; this temporal course alone does not rule out ACS
- Absence of reciprocal changes is possible but unreliable as a differentiating feature: it does not rule out ACS, and their presence does not rule out a neurogenic pattern — the diagnosis is established based on the totality of data
What it looks like on ECG
The classic sign is the so-called «cerebral» T waves: deep, wide, symmetric negative T waves, especially in chest leads V2–V6. Typically, maximum negativity is found in V3–V4, but changes may also involve limb leads. There is no validated quantitative depth threshold for diagnosis — both moderate and very deep T waves occur, and depth per se does not point toward or against SAH.
The QT interval is usually prolonged, and QTc may exceed 500 ms or even reach very high values. This is one of the risk factors for ventricular arrhythmias, including torsades de pointes.
The ST segment in neurogenic injury can vary: minor deviations as well as pronounced elevation or depression can occur, sometimes formally meeting STEMI criteria and mimicking acute coronary occlusion. Such a presentation requires the parallel exclusion of both intracranial haemorrhage and acute coronary occlusion — one does not rule out the other. A prominent U wave often appears, sometimes fusing with the T wave and complicating QT measurement.
The rhythm may be altered: sinus bradycardia (in increased intracranial pressure, Cushing's reflex) or sinus tachycardia (in sympathetic activation); supraventricular and ventricular premature beats are possible.
| Parameter | Typical finding |
|---|---|
| T wave | Deep, wide, symmetric, negative, V2–V6 |
| QT/QTc | Prolonged, sometimes significantly |
| ST | Variable: from minor deviation to a picture mimicking STEMI |
| U wave | Often prominent |
| Rhythm | Bradycardia or tachycardia, arrhythmias possible |
Changes appear anywhere from the first hours to several days after haemorrhage and regress gradually, usually over days to weeks; this temporal course is variable and by itself does not reliably differentiate a neurogenic pattern from a true myocardial infarction.
Mechanism
Subarachnoid haemorrhage causes central autonomic nervous system dysregulation and a pronounced sympathoadrenal surge of catecholamines (norepinephrine) from myocardial sympathetic nerve endings and the adrenal glands, involving hypothalamic, insular, and brainstem structures. The most typical mechanism of ECG changes is neurogenic catecholaminergic cardiomyocyte injury (microfocal necrosis of contractile fibers, contraction band necrosis) without coronary artery occlusion.
Excess catecholamines disrupt ventricular repolarisation processes, which is reflected on the ECG as deep T-wave inversion and QT prolongation. Simultaneously, troponin may rise and regional myocardial contractility may decrease (neurogenic stress-induced cardiomyopathy, pathogenetically close to Takotsubo-like cardiomyopathy). At the same time, true myocardial ischemia, coronary spasm, and concomitant ACS do occur in such patients and are not ruled out by the mere presence of SAH — they must be checked clinically, with serial troponins, echocardiography, and coronary angiography when indicated.
Causes
- Subarachnoid haemorrhage (aneurysmal and non-aneurysmal)
- Other acute central nervous system lesions with a similar mechanism: intracerebral haemorrhage, severe traumatic brain injury, ischemic stroke (less common), meningitis/encephalitis with mass effect
- Increased intracranial pressure of any etiology
- Conditions with marked sympathetic stress (catecholamine storm) — pheochromocytoma, severe emotional/physical stress as a pathogenetic analogue
Differential diagnosis
- Myocardial ischemia/infarction, including STEMI: neurogenic injury can present with ST changes and deep T waves, up to a picture formally mimicking STEMI; the absence of reciprocal changes does not rule out ACS, and their presence does not rule out SAH. Differentiation is based on clinical presentation (sudden severe headache, meningeal signs, neurological deficit), serial ECGs, troponin, echocardiography, head CT, and coronary angiography when indicated.
- Wellens' syndrome: biphasic or deep symmetric T-wave inversion predominantly in V2–V4 (less commonly broader, V1–V6), typically during the pain-free period following a chest pain episode, in the absence of acute infarction signs; clinical presentation is angina, not neurological deficit. T-wave depth and symmetry are not reliable differentiators from cerebral T waves; when in doubt, urgent evaluation of coronary pathology is necessary.
- Takotsubo cardiomyopathy: transient regional left ventricular dysfunction is detected, usually extending beyond a single coronary artery territory; the apical variant with ballooning hypokinesia is most common, but mid-ventricular, basal (reverse), and focal variants are possible. The ECG picture of negative T waves and QT prolongation is similar to cerebral T waves and pathogenetically close to them; differentiation requires echocardiography/ventriculography, coronary assessment, and clinical context (emotional stress vs. neurological catastrophe).
- Hypokalemia: flattened or biphasic T waves with a prominent U wave, combined with characteristic laboratory potassium changes.
- Drug poisoning with QT-prolonging agents: QT prolongation is present, but typical neurological symptoms are absent; T-wave depth and clinical context differ.
Clinical significance and management
ECG changes in SAH are clinically significant for two reasons: first, they can mimic acute coronary syndrome, including STEMI, and lead to diagnostic errors; second, marked QT prolongation increases the risk of ventricular tachyarrhythmias, including torsades de pointes, especially in the setting of electrolyte disturbances (common in SAH) and certain medications.
The physician should: perform an unenhanced head CT immediately if SAH is suspected. If CT is performed more than 6 hours after symptom onset or if high clinical suspicion persists (sudden severe headache, meningeal signs, altered consciousness) despite a negative CT, consider lumbar puncture for xanthochromia/erythrocytes or an alternative diagnostic pathway according to local protocol — a single negative CT does not always completely rule out SAH. CT angiography or digital subtraction angiography is performed to search for the bleeding source (aneurysm) after SAH is confirmed or for specific indications; a negative CT angiography does not rule out the haemorrhage itself. Evaluation for possible ACS should be conducted in parallel rather than delayed: serial ECGs, troponin, echocardiography, and coronary angiography as indicated. Do not administer antithrombotic therapy before ruling out intracranial haemorrhage unless risks and indications are urgently discussed in a multidisciplinary team. Additionally, electrolytes (potassium, magnesium) must be monitored and corrected, and rhythm monitored in the acute phase due to arrhythmia risk.
Common interpretation errors
- Interpreting deep negative T waves or ST elevation/depression definitively as ischemia/MI or, conversely, as purely neurogenic — without parallel evaluation of both directions
- Prescribing antiplatelet/anticoagulant therapy to a patient with suspected ACS without ruling out intracranial haemorrhage is an extremely dangerous error
- Ignoring QT prolongation and the associated risk of arrhythmias, especially with concomitant hypokalemia
- Relying on the absence of reciprocal changes or atypical evolution stages to reliably rule out myocardial infarction
- Underestimating the U wave, leading to incorrect measurement of the true QT duration
1. Which ECG finding is most characteristic of subarachnoid hemorrhage?
The classic sign of cerebral injury is diffuse deep and wide inverted T waves, typically without coronary occlusion, although concomitant ACS must be ruled out separately.
2. What is the underlying mechanism of ECG changes in subarachnoid hemorrhage?
Central autonomic nervous system dysregulation triggers a sympathetic catecholamine storm that damages cardiomyocytes and impairs repolarization, usually without coronary occlusion.
3. What is the correct management strategy for newly detected deep inverted T waves with suspected intracranial catastrophe?
Ruling out intracranial hemorrhage is critical because antithrombotic therapy in undiagnosed SAH is extremely dangerous, but ACS evaluation must proceed concurrently rather than being delayed.
Frequently asked questions
How do "cerebral" T waves differ from those in myocardial infarction?
Widespread deep and wide T waves in chest leads support a neurogenic pattern but are not specific: a similar picture can occur in MI, takotsubo cardiomyopathy, hypertrophy, and electrolyte disturbances. Reliable differentiation relies on the clinical context (acute neurological symptoms), serial ECGs, troponin, echocardiography, and head CT data, rather than the T wave morphology alone.
Are ECG changes in subarachnoid hemorrhage dangerous?
QT prolongation creates a risk of ventricular arrhythmias, including torsades de pointes. Furthermore, the ST-T pattern in SAH can occasionally mimic STEMI, which poses a bidirectional risk: erroneous antithrombotic therapy in a patient with intracranial hemorrhage and, conversely, missing true ACS if all changes are attributed to a neurological cause.
When do these ECG changes appear and disappear?
The onset timeline is variable—from the first hours to several days after hemorrhage. Resolution is also gradual and variable, typically taking days to weeks; the time course alone does not reliably distinguish between a neurogenic pattern and true infarction.
Does troponin rise in subarachnoid hemorrhage?
Yes, moderate troponin elevation can occur due to catecholamine-mediated myocardial microinjury and a neurogenic stress cardiomyopathy component. This does not rule out true ischemia or ACS—serial troponin assessment, echocardiography, and clinical correlation are required.
Is coronary angiography necessary with such ECG changes?
The decision is made individually and in a multidisciplinary manner, taking into account the overall clinical picture, serial ECGs, troponin dynamics, and echocardiography. Pronounced ST changes or a STEMI-mimicking pattern may require emergency coronary angiography concurrently with SAH management, rather than instead of it.
ECG Course
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Related terms
More in the section "Pericardium, Lungs, Brain and Others"
Sources
- Surawicz B., Knilans T. Chou's Electrocardiography in Clinical Practice, 6th ed.
- Goldberger A.L. Clinical Electrocardiography: A Simplified Approach
- Orlov V.N. Guide to Electrocardiography
Educational material for medical students and physicians. Does not replace clinical guidelines and physical examination; the ECG must always be interpreted in conjunction with the clinical picture.