The Adams-Stokes Syndrome is defined as an abrupt, transient loss of consciousness due to a sudden but pronounced decrease in the cardiac output, which is caused by a sudden change in the heart rate or rhythm. This definition does not include vasovagal syncope or epilepsy although patients with Stokes-Adams syncope may have seizures during periods of cerebral ischemia. Although partial or complete heart block is usually present during asymptomatic periods, many arrhythmias may produce syncopal episodes with or without the presence of previously established complete heart-block. “Arrhythmia-induced syncope” is a more specific term and includes the primary cause of the decreased cerebral blood flow.
Sudden collapse into unconsciousness due to a disorder of heart rhythm in which there is a slow or absent pulse resulting in syncope (fainting) with or without convulsions.
In this condition, the normal heartbeat passing from the upper chambers of the heart to the lower chambers is interrupted. This results in a condition called a “heart block.” When a heart block occurs, the heart rate usually slows considerably. This can cause inadequate blood flow to the brain and result in fainting.
Episodic cardiac arrest and syncope due to failure of normal and escape pacemakers, with or without ventricular fibrillation; the principal manifestation of severe heart attack.
Etiology of Adams-Stokes Syndrome
With congenital heart block, it has been described as being precipitated by bradycardia or tachycardia.
- Heart block may result from:
- Myocardial infarction.
- Fibrosis (usually associated with ischemia).
- Atrioventricular (AV) nodal disease.
- Structural or valvular heart disease.
- Electrolyte disturbance.
- Rheumatic diseases including ankylosing spondylitis, Reiter’s syndrome, rheumatoid arthritis, scleroderma.
- Infiltrative processes including amyloidosis, sarcoidosis, tumors, Hodgkin’s disease, multiple myeloma.
- Stokes-Adams attacks have been described as due to:
- Chronic or paroxysmal AV block in 50-60% of patients.
- Sino-atrial (SA) block in 30-40% of patients.
- Paroxysmal supraventricular tachycardia or atrial fibrillation in up to 5% of patients.
What are the Clinical Features of Adams-Stokes Syndrome
The clinical manifestations of arrhythmia-induced syncope depend upon the duration and
type of underlying arrhythmia as well as the status of the cerebral circulation. Symptoms of
arrhythmia-induced syncope vary from slight faintness to loss of consciousness, with or’without convulsions.
Characteristically, during the attack, there is an initial pallor. Following the resumption of the normal circulation, there is usually a facial flush due to reactive hyperemia. The absence of an aura tends to separate seizures occurring during Stokes-Adams syncope from seizures of primary cerebral origin.
Stokes-Adams seizures usually commence and terminate abruptly. The patient may resume a previous conversation or activity without being aware of the pause produced by the period of arrhythmia-induced cerebral ischemia. A slow or very rapid pulse during the
period of unconsciousness points toward the correct diagnosis. Electrocardiographic monitoring during a syncopal episode demonstrates the’responsible rhythm and makes appropriate therapy possible.
Electrocardiographic Mechanisms in Adams-Stokes Syndrome
At one time ventricular standstill was thought to be the sole mechanism responsible for StokesAdams syncope and it is still considered the most frequent underlying rhythm disturbance. However, it is now established that Stokes-Adams attacks may also be due to extreme bradycardia or to a variety of tachyarrhythmias, particularly ventricular tachycardia and ventricular fibrillation. Continuous monitoring has demonstrated that several electrocardiographic mechanisms may produce syncope in the same patient.
The arrhythmias responsible for Stokes-Adams syncope may be divided into seven groups:
1. A sudden interruption of atrioventricular impulse transmission causing transient asystole.When the cardiac rhythm changes from a sinus mechanism or incomplete A-V block to complete heart block, a period of asystole often occurs before the junctional or ventricular pacemaker assumes rhythmicity at its inherent rate. This “warm-up period” varies from ten to ninety seconds and is termed the “pre-automatic” pause.
2. Atrial standstill with the failure of the junctional pacemaker resulting in ventricular asystole. When sinoatrial node impulse formation ceases and the A-V junctional tissue fails to assume rhythmicity, ventricular asystole results. This mechanism for Strokes-Adams syncope may occur in patients with inferior wall myocardial ischemia and may be influenced by vagal hyperactivity. This is an uncommon mechanism of arrhythmia-induced syncope.
3. Asystole in the presence of established heart block. This arrhythmia may result from a shift in the pacemaker below the area of nonconduction to still a lower focus resulting in a period of asystole resembling the “preautomatic pause.
4. Paroxysmal ventricular tachycardia or fibrillation in the presence of complete heart block. A slow heart rate during complete heart block predisposes to rapid impulse formation from ectopic foci. Either ventricular tachycardia or fibrillation may then ensue with syncope resulting.
5. Paroxysmal ventricular tachycardia or fibrillation during normal A-V conduction. These arrhythmias are most frequently observed in patients with acute myocardial infarction but have also caused syncopal episodes in patients with apparently normal hearts.
6. Supraventricular arrhythmias. Supraventricular tachycardias and bradycardias associated with syncopal episodes have been demonstrated by continuous electrocardiographic monitoring in many patients with the Stokes-Adams syndrome. Frequently the sinus bradycardia predisposes to episodic supraventricular tachycardia (“bradycardia-tachycardia syndrome’). In patients with coronary artery, disease tachycardia increases myocardial oxygen demands and decreases left coronary artery diastolic blood flow, often decreasing cardiac output despite the increase in heart rate. Syncopal episodes may result.
Sinus bradycardia, sinoatrial block, and sinoatrial arrest may cause syncope in patients with
heart disease who are unable to increase stroke volume sufficiently to maintain adequate cerebral blood flow.
7. Combined forms. Uncommonly, paroxysmal tachyarrhythmias may be followed by a period of asystole due to a delay in automaticity of pacemakers which have been suppressed during the tachycardia. The recognition that different electrocardiographic
mechanisms may produce syncope in the same patient on different occasions is important
Differential diagnoses of Adams-Stokes Syndrome
This is the differential diagnosis of syncope and includes the following:
- Epilepsy (in case of convulsions).
- Vasovagal fainting.
- Carotid sinus hypersensitivity.
- Orthostatic hypotension.
- A fast tachyarrhythmia (may also reduce cardiac output but does not usually have the same brief but dramatic effect).
- Drop attacks.
- Transient ischaemic attack.
- Syncope due to hypoperfusion – eg, due to hypovolaemia.
Clinical Presentation of Adams-Stokes Syndrome
- There is a collapse, usually without warning.
- Loss of consciousness is usually between about 10 and 30 seconds.
- Pallor, followed by flushing on recovery, can be reported.
- Some seizure-like activity sometimes occurs if the attack is prolonged.
- If anyone manages to check the pulse during an episode, it will be slow, usually less than 40 beats per minute.
- Recovery is fairly rapid, although the patient may be confused for a while afterward.
- Typically, complete (third-degree) heart block is seen on the ECG during an attack but other ECG abnormalities such as Tachy-Brady syndrome have been reported. (The separate article ECG Identification of Conduction Disorders describes a complete heart block in more detail.)
- Attacks can happen a number of times in one day.
- They are not posture-related.
Diagnosis of Adams-Stokes Syndrome
- History of other episodes.
- Past medical history, including the history of heart disease.
- Drug history: establish whether medication might be contributing.
- Blood pressure examination (supine and standing).
- Cardiovascular examination.
- 12-lead ECG: this may be normal by the time the patient is seen or may show heart block or ischaemic changes; 24-hour ECG may show changes during attacks.
- Routine haematological and biochemical investigations.
- If underlying heart disease is suspected, this should be investigated appropriately.
- If seizure activity has been witnessed, the possibility of epilepsy should be investigated.
Treatment of Adams-Stokes Syndrome
The aim of therapy for arrhythmia-induced syncope is threefold:
- prompt restoration of the circulation during cardiac arrest,
- restoration of an intrinsic cardiac rhythm adequate to maintain cerebral blood flow
- prevention of recurrent episodes.
Medical Treatment of Adams-Stokes Syndrome
The medical therapy of complete heart block includes the correction of potential contributing factors such as acidosis and hyperkalemia. The sympathomimetic drugs,
which include parenteral epinephrine, oral ephedrine, and isoproterenol by either route of
administration, are primarily indicated when ventricular asystole or bradycardia occurs in
complete heart block and intracardiac pacing are unavailable. These agents act by increasing A-V conduction, increasing the rate of the ventricular pacemaker and shifting the lower pacemaker to a higher focus in the common bundle or A-V junctional tissue. During an attack of arrhythmia-induced syncope due to bradycardia, isoproterenol should be given by intravenous infusion during electrocardiogram monitoring so that its administration can be rapidly terminated if ventricular irritability results. The vagolytic agent atropine may increase the ventricular rate in complete heart block complicating a recent inferior wall myocardial infarction. Atropine is often successful in the treatment and prevention of Stokes-Adams syncope due to sinus bradycardia, sinoatrial block, and bradycardia-tachycardia syndrome.
Steroids through their anti-inflammatory and hypokalemic effects have been occasionally successful in improving A-V conduction in patients with complete heart block due to myocarditis or acute myocardial infarction.The trisodium salt of ethylenediamine-tetraacetic
acid, a calcium-chelating agent, has been used in the treatment of complete heart block due to digitalis intoxication when electrical pacing is unavailable.Pacemaker therapy. Because of the unpredictable, potentially fatal nature of StokesAdams attacks and the inconsistent results and frequent complications with drug therapy, electrical pacing has become the treatment of choice when syncope occurs in patients with complete heart block.
The general indications for pacemaker insertion include
- complete heart block associated with congestive heart failure
- complete heart block with Stokes-Adams syncope
- complete heart block following acute anterior or inferior wall myocardial infarction
- partial A-V block (second-degree block) complicating anterior wall myocardial infarction
- postsurgical complete heart block.
Recent reports have demonstrated the feasibility of suppressing episodes of ventricular
tachycardia and fibrillation in patients with normal A-V conduction by pacing the atrium
or the ventricle at a rate faster than that present between episodes of ventricular tachyarrhythmia. Electrical pacing has been employed successfully in combination with propranolol and cardiac sympathectomy in the treatment of otherwise unresponsive ventricular arrhythmias. Rapid atrial pacing has been used successfully in the treatment of supraventricular tachycardias including atrial flutter and paroxysmal atrial tachycardia.
In patients with syncopal attacks due to ventricular tachycardia or ventricular fibrillation
complicating complete heart block, the emergency insertion of a ventricular pacemaker is
strongly indicated. A ventricular pacemaker is the only means available for the long-term prevention of ventricular tachyarrhythmias in patients with heart block. If transient ventricular asystole complicates complete heart block a ventricular pacemaker is also indicated. A single Stokes-Adams attack in a patient with complete heart block is sufficient reason for pacemaker insertion.
Management of Adams-Stokes Syndrome
- Reversible causes such as drug toxicity should be addressed.
- Underlying heart disease should be managed appropriately.
- A cardiac pacemaker may be required