The diagnosis of heat syncope is done during a physical examination. During the physical exam the practitioner will test the blood pressure of the patient, and the pulse. If the patient is experiencing heat syncope the blood pressure will be low, and the pulse will be elevated. Observation of excess sweating will also be a key sign. Finally, the practitioner will ask questions figuring out the history of the patient's symptoms. If the patient developed symptoms while engaging in physical activity and high temperatures it will then be a true case of heat syncope.

In addition to the mechanism described above, a number of other medical conditions may cause syncope. Making the correct diagnosis for loss of consciousness is difficult. The core of the diagnosis of vasovagal syncope rests upon a clear description of a typical pattern of triggers, symptoms, and time course.

It is pertinent to differentiate lightheadedness, seizures, vertigo, and low blood sugar as other causes.

In people with recurrent vasovagal syncope, diagnostic accuracy can often be improved with one of the following diagnostic tests:

- A tilt table test (results should be interpreted in the context of patients' clinical presentations and with an understanding of the sensitivity and specificity of the test)

- Implantation of an insertable loop recorder

- A Holter monitor or event monitor

- An echocardiogram

- An electrophysiology study

Treatment for reflex syncope focuses on avoidance of triggers, restoring blood flow to the brain during an impending episode, and measures that interrupt or prevent the pathophysiologic mechanism described above.

The basic treatment for heat syncope is like that for other types of fainting: the patient is positioned in a seating or supine position with legs raised. Water containing salt, or another drink containing electrolytes, is administered slowly, and the patient is moved to a cooler area, such as the shade.

The affected person should rest and recover, because heat syncope can lead to heat stroke or heat exhaustion.

The tilt table test is an evaluative clinical test to help identify postural hypotension, a common cause of presyncope or syncope. A tilt angle of 60 and 70 degrees is optimal and maintains a high degree of specificity. A positive sign with the tilt table test must be taken in context of patient history, with consideration of pertinent clinical findings before coming to a conclusion.

Accurate determination of core temperature often requires a special low temperature thermometer, as most clinical thermometers do not measure accurately below . A low temperature thermometer can be placed in the rectum, esophagus or bladder. Esophageal measurements are the most accurate and are recommended once a person is intubated. Other methods of measurement such as in the mouth, under the arm, or using an infrared ear thermometer are often not accurate.

As a hypothermic person's heart rate may be very slow, prolonged feeling for a pulse could be required before detecting. In 2005, the American Heart Association recommended at least 30–45 seconds to verify the absence of a pulse before initiating CPR. Others recommend a 60-second check.

The classical ECG finding of hypothermia is the Osborn J wave. Also, ventricular fibrillation frequently occurs below and asystole below . The Osborn J may look very similar to those of an acute ST elevation myocardial infarction. Thrombolysis as a reaction to the presence of Osborn J waves is not indicated, as it would only worsen the underlying coagulopathy caused by hypothermia.

If a person with heat exhaustion gets medical treatment, Emergency Medical Technicians (EMTs) or doctors and/or nurses may also:

- Give them supplemental oxygen

- Give them intravenous fluids and electrolytes if they are too confused to drink and/or are vomiting

When ambient temperature is excessive, humans and many animals cool themselves below ambient by evaporative cooling of sweat (or other aqueous liquid; saliva in dogs, for example); this helps prevent potentially fatal hyperthermia. The effectiveness of evaporative cooling depends upon humidity. Wet-bulb temperature, which takes humidity into account, or more complex calculated quantities such as wet-bulb globe temperature (WBGT), which also takes solar radiation into account, give useful indications of the degree of heat stress and are used by several agencies as the basis for heat-stress prevention guidelines. (Wet-bulb temperature is essentially the lowest skin temperature attainable by evaporative cooling at a given ambient temperature and humidity.)

A sustained wet-bulb temperature exceeding 35 °C is likely to be fatal even to fit and healthy people unclothed in the shade next to a fan; at this temperature, environmental heat gain instead of loss occurs. , wet-bulb temperatures only very rarely exceeded 30 °C anywhere, although significant global warming may change this.

In cases of heat stress caused by physical exertion, hot environments, or protective equipment, prevention or mitigation by frequent rest breaks, careful hydration, and monitoring body temperature should be attempted. However, in situations demanding one is exposed to a hot environment for a prolonged period or must wear protective equipment, a personal cooling system is required as a matter of health and safety. There is a variety of active or passive personal cooling systems; these can be categorized by their power sources and whether they are person- or vehicle-mounted.

Because of the broad variety of operating conditions, these devices must meet specific requirements concerning their rate and duration of cooling, their power source, and their adherence to health and safety regulations. Among other criteria are the user's need for physical mobility and autonomy. For example, active-liquid systems operate by chilling water and circulating it through a garment; the skin surface area is thereby cooled through conduction. This type of system has proven successful in certain military, law enforcement, and industrial applications. Bomb-disposal technicians wearing special suits to protect against improvised explosive devices (IEDs) use a small, ice-based chiller unit that is strapped to one leg; a liquid-circulating garment, usually a vest, is worn over the torso to maintain a safe core body temperature. By contrast, soldiers traveling in combat vehicles can face microclimate temperatures in excess of 65 °C and require a multiple-user, vehicle-powered cooling system with rapid connection capabilities. Requirements for hazmat teams, the medical community, and workers in heavy industry vary further.

First aid for heat exhaustion includes:

- Moving the person to a cool place

- Having the patient take off extra layers of clothes

- Cooling the patient down by fanning them and putting wet towels on their body

- Having them lie down and put their feet up if they are feeling dizzy

- Having them drink water or sports drinks – but only if they are awake, not confused nor vomiting

- Turning the person on their side if they are vomiting

The underlying cause must be removed. Mild hyperthemia caused by exertion on a hot day may be adequately treated through self-care measures, such as increased water consumption and resting in a cool place. Hyperthermia that results from drug exposure requires prompt cessation of that drug, and occasionally the use of other drugs as counter measures. Antipyretics (e.g., acetaminophen, aspirin, other nonsteroidal anti-inflammatory drugs) have no role in the treatment of heatstroke because antipyretics interrupt the change in the hypothalamic set point caused by pyrogens; they are not expected to work on a healthy hypothalamus that has been overloaded, as in the case of heatstroke. In this situation, antipyretics actually may be harmful in patients who develop hepatic, hematologic, and renal complications because they may aggravate bleeding tendencies.

When body temperature is significantly elevated, mechanical cooling methods are used to remove heat and to restore the body's ability to regulate its own temperatures. Passive cooling techniques, such as resting in a cool, shady area and removing clothing can be applied immediately. Active cooling methods, such as sponging the head, neck, and trunk with cool water, remove heat from the body and thereby speed the body's return to normal temperatures. Drinking water and turning a fan or dehumidifying air conditioning unit on the affected person may improve the effectiveness of the body's evaporative cooling mechanisms (sweating).

Sitting in a bathtub of tepid or cool water (immersion method) can remove a significant amount of heat in a relatively short period of time. It was once thought that immersion in very cold water is counterproductive, as it causes vasoconstriction in the skin and thereby prevents heat from escaping the body core. However, a British analysis of various studies stated: "this has never been proven experimentally. Indeed, a recent study using normal volunteers has shown that cooling rates were fastest when the coldest water was used." The analysis concluded that cool water immersion is the most-effective cooling technique for exertional heat stroke. No superior cooling method has been found for non-exertional heat stroke. Thus, aggressive ice-water immersion remains the gold standard for life-threatening heat stroke.

When the body temperature reaches about 40 °C, or if the affected person is unconscious or showing signs of confusion, hyperthermia is considered a medical emergency that requires treatment in a proper medical facility. In a hospital, more aggressive cooling measures are available, including intravenous hydration, gastric lavage with iced saline, and even hemodialysis to cool the blood.

No formal diagnostic criteria exist. A diagnosis of Inappropriate sinus tachycardia is primarily one of exclusion and the following may be observed:

- Exclusion of all other causes of sinus tachycardia

- Common forms of supraventricular tachycardia (SVT) must be excluded

- Normal P wave morphology

- A resting sinus tachycardia is usually (but not always) present

- Nocturnal dip in heart rate

- Inappropriate heart rate response on exertion

- Mean heart rate in 24hrs >95 bpm

- Symptoms are documented to be due to tachycardia

- Hypotension is occasionally observed

- Syncope (fainting) is occasionally reported

The diagnosis of hypotension is made by first obtaining a blood pressure, either non-invasively with a sphygmomanometer or invasively with an arterial catheter (mostly in an intensive care setting). If the MAP (Mean Arterial Pressure) is <65mmHg, this is generally considered hypotension.

For most adults, the healthiest blood pressure is at or below 120/80 mmHg. A small drop in blood pressure, even as little as 20 mmHg, can result in transient hypotension.

Evaluation of vasovagal syncope is done with a tilt table test.

ECG characteristics

- Rate: Less than 60 beats per minute.

- Rhythm: Regular.

- P waves: Upright, consistent, and normal in morphology and duration.

- P-R Interval: Between 0.12 and 0.20 seconds in duration.

- QRS Complex: Less than 0.12 seconds in width, and consistent in morphology.

Mild disease can be treated with fluids by mouth. In more significant disease spraying with mist and using a fan is useful. For those with severe disease putting them in lukewarm water is recommended if possible with transport to a hospital.

Prevention includes avoiding medications that can increase the risk of heat illness (e.g. antihypertensives, diuretics, and anticholinergics), gradual adjustment to heat, and sufficient fluids and electrolytes.

People with POTS will show a marked rise in heart rate within 10 minutes of standing or being tilted 60° head-up on a tilt table, without a corresponding decrease in blood pressure. A variety of autonomic tests are employed to exclude autonomic disorders that could underlie symptoms, while endocrine testing is used to exclude hyperthyroidism and rarer endocrine conditions. Electrocardiography is normally performed on all patients to exclude other possible causes of tachycardia. In cases where a particular associated condition or complicating factor are suspected, other non-autonomic tests may be used: echocardiography to exclude mitral valve prolapse, and thermal threshold tests for small-fiber neuropathy.

Testing the cardiovascular response to prolonged head-up tilting, exercise, eating, and heat stress may help determine the best strategy for managing symptoms. POTS has also been divided into several types (see § Causes), which may benefit from distinct treatments. People with neuropathic POTS show a loss of sweating in the feet during sweat tests, as well as impaired norepinephrine release in the leg, but not arm. This is believed to reflect peripheral sympathetic denervation in the lower limbs. People with hyperadrenergic POTS show a marked increase of blood pressure and norepinephrine levels when standing, and are more likely to suffer from prominent palpitations, anxiety, and tachycardia.

It is usually recommended not to declare a person dead until their body is warmed to a near normal body temperature of greater than , since extreme hypothermia can suppress heart and brain function. Exceptions include if there is an obvious fatal injuries or the chest is frozen so that it cannot be compressed. If a person was buried in an avalanche for more than 35 minutes and is found with a mouth packed full of snow without a pulse, stopping early may also be reasonable. This is also the case if a person's blood potassium is greater than 12 mmol/l.

Those who are stiff with pupils that do not move may survive if treated aggressively. Survival with good function also occasionally occurs even after the need for hours of CPR. Children who have near-drowning accidents in water near can occasionally be revived, even over an hour after losing consciousness. The cold water lowers the metabolism, allowing the brain to withstand a much longer period of hypoxia. While survival is possible, mortality from severe or profound hypothermia remains high despite optimal treatment. Studies estimate mortality at between 38% and 75%.

In those who have hypothermia due to another underlying health problem, when death occurs it is frequently from that underlying health problem.

The treatment for hypotension depends on its cause. Chronic hypotension rarely exists as more than a symptom. Asymptomatic hypotension in healthy people usually does not require treatment. Adding electrolytes to a diet can relieve symptoms of mild hypotension. A morning dose of caffeine can also be effective. In mild cases, where the patient is still responsive, laying the person in dorsal decubitus (lying on the back) position and lifting the legs increases venous return, thus making more blood available to critical organs in the chest and head. The Trendelenburg position, though used historically, is no longer recommended.

Hypotensive shock treatment always follows the first four following steps. Outcomes, in terms of mortality, are directly linked to the speed that hypotension is corrected. Still-debated methods are in parentheses, as are benchmarks for evaluating progress in correcting hypotension. A study on septic shock provided the delineation of these general principles. However, since it focuses on hypotension due to infection, it is not applicable to all forms of severe hypotension.

1. Volume resuscitation (usually with crystalloid)

2. Blood pressure support with a vasopressor (all seem equivalent with respect to risk of death, with norepinephrine possibly better than dopamine). Trying to achieve a mean arterial pressure (MAP) of greater than 70 mmHg does not appear to result in better outcomes than trying to achieve a MAP of greater than 65 mm Hg in adults.

3. Ensure adequate tissue perfusion (maintain SvO2 >70 with use of blood or dobutamine)

4. Address the underlying problem (i.e., antibiotic for infection, stent or CABG (coronary artery bypass graft surgery) for infarction, steroids for adrenal insufficiency, etc...)

The best way to determine if a person will benefit from fluids is by doing a passive leg raise followed by measuring the output from the heart.

OI is "notoriously difficult to diagnose." As a result, many patients have gone undiagnosed or misdiagnosed and either untreated or treated for other disorders. Current tests for OI (Tilt table test, autonomic assessment, and vascular integrity) can also specify and simplify treatment. (See Dr. Julian Stewart's article, "Orthostatic Intolerance: An Overview" for a more detailed description of OI tests.)

Affected patients demonstrate no structural problems of the heart upon echocardiographic, CT or MRI imaging.

CPVT diagnosis is based on reproducing irregularly shaped ventricular arrhythmias during ECG exercise stress testing, syncope occurring during physical activity and acute emotion, and a history of exercise or emotion-related palpitations and dizziness with an absence of structural cardiac abnormalities.

Because its symptoms are usually only triggered when the body is subjected to intense emotional or physical stress, the condition is often not detected by the traditional methods of electrophysiologic examination such as a resting electrocardiogram.

Presyncope is a state of lightheadedness, muscular weakness, blurred vision, and feeling faint (as opposed to a syncope, which is actually fainting). Presyncope is most often cardiovascular in cause. In many people, lightheadedness is a symptom of orthostatic hypotension. Orthostatic hypotension occurs when blood pressure drops significantly when the patient stands from a supine (horizontal) or seatted position. If loss of consciousness occurs in this situation, it is termed syncope.

Presyncope is frequently reported in people with autonomic dysfunctions such as the postural orthostatic tachycardia syndrome (POTS).

POTS has a favorable prognosis when managed appropriately. Symptoms improve within five years of diagnosis for many patients, and 60% return to their original level of functioning. About 90% of people with POTS respond to a combination of pharmacological and physical treatments. Those who develop POTS in their early to mid teens during a period of rapid growth will most likely see complete symptom resolution in two to five years. Outcomes are more guarded for adults newly diagnosed with POTS. Some people do not recover, and a few even worsen with time. The hyperadrenergic type of POTS typically requires continuous therapy. If POTS is caused by another condition, outcomes depend on the prognosis of the underlying disorder.

IST has been treated both pharmacologically and invasively, with varying degrees of success. IST, in and of itself, is not indicative of higher rates of mortality, and non-treatment is an option chosen by many if they have minimal symptoms.

Some types of medication tried by cardiologists and other physicians include: beta blockers, selective sinus node I channel inhibitors (ivabradine), calcium channel blockers and antiarrhythmic agents. Some SSRI drugs are also occasionally tried and also treatments more commonly used to treat postural orthostatic tachycardia syndrome such as fludrocortisone. This approach is very much "trial-and-error". Patients with IST are often intolerant to beta blockers. A new selective sinus node inhibitor ivabradine is also being used to treat IST.

Invasive treatments include forms of catheter ablation such as sinus node modification (selective ablation of the sinus node), complete sinus node ablation (with associated implantation of a permanent artificial pacemaker) and AV node ablation in very resistant cases (creation of iatrogenic complete heart block, necessitating implantation of a permanent artificial pacemaker).

However invasive treatments can also make the symptoms worse, not cure it. Treatment should be chosen with care as the patient could become in need of a pacemaker or have more extensive symptoms.

Most patients experience an improvement of their symptoms, but for some, OI can be gravely disabling and can be progressive in nature, particularly if it is caused by an underlying condition which is deteriorating. The ways in which symptoms present themselves vary greatly from patient to patient; as a result, individualized treatment plans are necessary.

OI is treated both pharmacologically and non-pharmacologically. Treatment does not cure OI; rather, it controls symptoms.

Physicians who specialize in treating OI agree that the single most important treatment is drinking more than two liters (eight cups) of fluids each day. A steady, large supply of water or other fluids reduces most, and for some patients all, of the major symptoms of this condition. Typically, patients fare best when they drink a glass of water no less frequently than every two hours during the day, instead of drinking a large quantity of water at a single point in the day.

For most severe cases and some milder cases, a combination of medications are used. Individual responses to different medications vary widely, and a drug which dramatically improves one patient's symptoms may make another patient's symptoms much worse. Medications focus on three main issues:

Medications that increase blood volume:

- Fludrocortisone (Florinef)

- Erythropoietin

- Hormonal contraception

Medications that inhibit acetylcholinesterase:

- Pyridostigmine

Medications that improve vasoconstriction:

- Stimulants: (e.g., Ritalin or Dexedrine)

- Midodrine (ProAmatine)

- Ephedrine and pseudoephedrine (Sudafed)

- Theophylline (low-dose)

- Selective serotonin reuptake inhibitors (SSRI's - Prozac, Zoloft, and Paxil)

Behavioral changes that patients with OI can make are:

- Avoiding triggers such as prolonged sitting, quiet standing, warm environments, or vasodilating medications

- Using postural maneuvers and pressure garments

- Treating co-existing medical conditions

- Increasing fluid and salt intake

- Physical therapy and exercise unless contraindicated by an underlying condition such as chronic fatigue syndrome where traditional exercise can worsen the condition

Heat cramps, a type of heat illness, are muscle spasms that result from loss of large amount of salt and water through exercise. Heat cramps are associated with cramping in the abdomen, arms and calves. This can be caused by inadequate consumption of fluids or electrolytes. Frequently, they don't occur until sometime later, especially at night or when relaxing. Heavy sweating causes heat cramps, especially when the water is replaced without also replacing salt or potassium.

Although heat cramps can be quite painful, they usually don't result in permanent damage, though they can be a symptom of heat stroke or heat exhaustion. Heat cramps can indicate a more severe problem in someone with heart disease or if they last for longer than an hour.

In order to prevent them, one may drink electrolyte solutions such as sports drinks during exercise or strenuous work or eat potassium-rich foods like bananas and apples. When heat cramps occur, the affected person should avoid strenuous work and exercise for several hours to allow for recovery.