Syncope (medicine)

A 1744 oil painting by Pietro Longhi called Fainting
Syncope from bradycardia
ECG showing HOCM
Long QT syndrome
A short PR in Wolff–Parkinson–White syndrome
Type 2 Brugada ECG pattern

Loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery.

- Syncope (medicine)

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Too fast or too slow.

Ventricular fibrillation (VF) showing disorganized electrical activity producing a spiked tracing on an electrocardiogram (ECG)
Broad classification of arrhythmias according to region of heart required to sustain the rhythm
Normal sinus rhythm, with solid black arrows pointing to normal P waves representative of normal sinus node function, followed by a pause in sinus node activity (resulting in a transient loss of heartbeats). Note that the P wave that disrupts the pause (indicated by the dashed arrow) does not look like the previous (normal) P waves – this last P wave is arising from a different part of the atrium, representing an escape rhythm.

In more serious cases, there may be lightheadedness, passing out, shortness of breath or chest pain.


Slow resting heart rate, commonly under 60 beats per minute (BPM) as determined by an electrocardiogram.

Sinus bradycardia seen in lead II with a heart rate of about 50BPM
Illustration comparing the ECGs of a healthy person (top) and a person with bradycardia (bottom): The points on the heart where the ECG signals are measured are also shown.

In some people, bradycardia below 60 BPM may be associated with fatigue, weakness, dizziness, sweating, and fainting.

Pulmonary embolism

Blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism).

A lung illustration depicting a pulmonary embolism as a thrombus (blood clot) that has travelled from another region of the body, causes occlusion of the pulmonary bronchial artery, leading to arterial thrombosis of the superior and inferior lobes in the left lung
A deep vein thrombosis as seen in the right leg is a risk factor for PE
A Hampton hump in a person with a right lower lobe pulmonary embolism
Selective pulmonary angiogram revealing clot (labeled A) causing a central obstruction in the left main pulmonary artery. ECG tracing shown at the bottom.
Electrocardiogram of a person with pulmonary embolism, showing sinus tachycardia of approximately 100 beats per minute, large S wave in Lead I, moderate Q wave in Lead III, inverted T wave in Lead III, and inverted T waves in leads V1 and V3.
Histopathology of a pulmonary artery from autopsy. It shows a fat embolism (seen as multiple empty globular spaces on this H&E stain since its processing dissolves fat). There is a bone marrow fragment in the middle, and multiple single hematopoietic cells in the blood, being evidence of fracture as the source of the embolism.
Used inferior vena cava filter.
Large saddle embolus seen in the pulmonary artery (white arrows).
On CT scan, pulmonary emboli can be classified according to the level along the arterial tree.
Segmental and subsegmental pulmonary emboli on both sides
CT pulmonary angiography showing a "saddle embolus" at the bifurcation of the main pulmonary artery and thrombus burden in the lobar arteries on both sides.
Pulmonary embolism (white arrow) that has been long-standing and has caused a lung infarction (black arrow) seen as a reverse halo sign.

Severe cases can lead to passing out, abnormally low blood pressure, obstructive shock, and sudden death.

Long QT syndrome

Condition in which repolarization of the heart after a heartbeat is affected.

ECG showing typical pattern of inherited Long QT syndrome (LQT1). A QT interval of >480 ms is considered abnormally long.
Acquired long QT syndrome
Electrocardiograms from a single family showing unaffected family member (top), Romano Ward syndrome (middle) and Jervell and Lange-Nielsen syndrome (bottom).
Cellular mechanisms leading to arrhythmias in long QT syndrome
Measurement of the QT interval with normal and prolonged QT intervals
Range of QT intervals expected in healthy males, healthy females, and those with long QT syndrome.
Characteristic ECG patterns associated with the three major subtypes of inherited Long QT syndrome
T-wave alternans in an individual with long QT syndrome

It results in an increased risk of an irregular heartbeat which can result in fainting, drowning, seizures, or sudden death.


Low blood pressure.

If the blood pressure is sufficiently low, fainting (syncope) may occur.


Sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes.

A young boy coughing due to pertussis causing whooping cough.
Coughing is viewed as a public health issue.

Acute complications include cough syncope (fainting spells due to decreased blood flow to the brain when coughs are prolonged and forceful), insomnia, cough-induced vomiting, subconjunctival hemorrhage or "red eye", coughing defecation and in women with a prolapsed uterus, cough urination.


Period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain.

Generalized 3 Hz spike and wave discharges in EEG
An individual who has bitten the tip of their tongue while having a seizure
An EEG can aid in locating the focus of the epileptic seizure.

Conditions that look like epileptic seizures but are not include: fainting, nonepileptic psychogenic seizure and tremor.

Aortic dissection

Injury to the innermost layer of the aorta allows blood to flow between the layers of the aortic wall, forcing the layers apart.

Dissection of the descending part of the aorta (3), which starts from the left subclavian artery and extends to the abdominal aorta (4). The ascending aorta (1) and aortic arch (2) are not involved in this image.
Blood penetrates the intima and enters the media layer.
Histopathological image of dissecting aneurysm of the thoracic aorta in a patient without evidence of Marfan syndrome: The damaged aorta was surgically removed and replaced by artificial vessel, Victoria blue & HE stain.
Diagnostic algorithm of aortic dissection
Aortic dissection on CXR: Note is made of a wide aortic knob.
MRI of an aortic dissection
1 Aorta descendens with dissection
2 Aorta isthmus
Closure of the lumen of a Type B aortic dissection following medical management
CT with contrast demonstrating aneurysmal dilation and a dissection of the ascending aorta (type A Stanford)
Chest CT with descending (type B Stanford) aortic dissection (red circle)
Type A dissection with pericardial effusion as a result.

Less common symptoms that may be seen in the setting of AD include congestive heart failure (7%), fainting (9%), stroke (6%), ischemic peripheral neuropathy, paraplegia, and cardiac arrest.


Process of producing an electrocardiogram , a recording of the heart's electrical activity.

ECG of a heart in normal sinus rhythm
Normal 12-lead ECG
A 12-lead ECG of a 26-year-old male with an incomplete right bundle branch block (RBBB)
A patient undergoing an ECG
An EKG electrode
Proper placement of the limb electrodes. The limb electrodes can be far down on the limbs or close to the hips/shoulders as long as they are placed symmetrically.
Placement of the precordial electrodes
The limb leads and augmented limb leads (Wilson's central terminal is used as the negative pole for the latter in this representation)
Diagram showing the contiguous leads in the same color in the standard 12-lead layout
QRS is upright in a lead when its axis is aligned with that lead's vector
Schematic representation of a normal ECG
Measuring time and voltage with ECG graph paper
Animation of a normal ECG wave
Formation of limb waveforms during a pulse
An early commercial ECG device (1911)
ECG from 1957
Use of real time monitoring of the heart in an intensive care unit in a German hospital (2015), the monitoring screen above the patient displaying an electrocardiogram and various values of parameters of the heart like heart rate and blood pressure

Symptoms such as shortness of breath, murmurs, fainting, seizures, funny turns, or arrhythmias including new onset palpitations or monitoring of known cardiac arrhythmias


Heart rate that exceeds the normal resting rate.

ECG showing sinus tachycardia with a rate of about 100 beats per minute
12 lead electrocardiogram showing a ventricular tachycardia (VT)

Tachycardia can lead to fainting.