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Autonomic Disorders

Learn more about the autonomic disorders that we study at the Calgary Autonomic Investigation & Management Lab.

Dysautonomia

The term dysautonomia is not a diagnosis, but rather a reference to autonomic disorders as a group, in which there may be one or more very different problems with the function of the autonomic nervous system (ANS). This page provides information on a few specific disorders that we study at the Autonomic Investigation and Management Lab under the umbrella of 'autonomic dysfunction'. 

The ANS is responsible for regulating bodily functions that are not consciously directed, such as blood pressure, heart rate, respiratory rate, and metabolism. 

Orthostatic hypotension - also called postural hypotension - is a form of low blood pressure that occurs upon standing from a sitting or lying position. 

Upon standing, gravity causes blood to pool in the legs. As a result, less blood is circulating back to the heart to be pumped out, causing low blood pressure (hypotension).  

Normally, this drop in blood pressure is immediately combated by the autonomic nervous system before symptoms can occur. Specialized nerve cells called baroreceptors are located in the arteries around the heart and neck; when the pressure in the arteries drops, these cells sense the change and relay it to the brain, which signals the heart to pump faster to compensate for the decreased pressure. In addition, the baroreceptors cause the narrowing of the blood vessels, resulting in increased resistance to blood flow and, thus, increased blood pressure. 

Orthostatic hypotension occurs when there is an interruption in the body's process of restoring blood pressure upon standing. Symptoms of dizziness and lightheadedness occur when the drop in blood pressure is not immediately corrected due to decreased blood flow to the brain. While many people may experience occasional dizzy spells lasting a few seconds, a medical professional should investigate chronic or prolonged symptoms upon standing.

  1. Signs and Symptoms

    Symptoms of orthostatic hypotension typically occur shortly after standing up and generally last only a few seconds. The following signs and symptoms may indicate orthostatic hypotension if they become frequent. 

    • Feeling lightheaded or dizzy after standing up
    • Blurry vision
    • Weakness
    • Fainting (syncope)
    • Confusion
    • Nausea

  2. Testing and Diagnosis

    The goal in evaluating orthostatic hypotension is to find the underlying cause in order to determine the most appropriate treatment and potentially identify any more severe problems of the heart, brain, or nervous system. Testing often involves an examination of the cardiovascular and nervous systems. To help reach a diagnosis, one or more of the following may be recommended: 

    • Blood pressure monitoring
    • Blood tests
    • Electrocardiogram (ECG) 
    • Echocardiogram
    • Stress test
    • Tilt table test
    • Valsalva maneuver

    Diagnostically, orthostatic hypotension is defined as a blood pressure decrease of >20 mmHg in systolic blood pressure or >10 mmHg in diastolic blood pressure within two to five minutes of standing up.

  3. Treatment

    The underlying causes of orthostatic hypotension vary between patients; treatment typically aims to address the underlying health problem rather than the low blood pressure itself. Therefore, treatment plans must be tailored to each patient for maximum efficacy. Some treatments that may be effective are outlined below.

    Fludrocortisone 
    Fludrocortisone is a mineralocorticoid analogue of aldosterone. It acts on the kidney to conserve sodium and water and increases plasma volume, which raises blood pressure.

    Midodrine 
    Midodrine is an alpha-1 agonist that causes vasoconstriction and helps to decrease venous pooling. By limiting the ability of the blood vessels to expand, midodrine is able to raise standing blood pressure.

  4. Lifestyle Measures

    Lifestyle strategies are important in managing orthostatic hypotension. Some measures that may be effective are outlined below.

    Compression Stockings 
    These stockings provide compression to the legs to help decrease peripheral venous pooling and increase venous return to the heart. The most effective stockings offer at least 30-40 mmHg of compression and are waist-high. 

    Temperature 
    Many patients find that heat is a major trigger of their symptoms since it causes vasodilation - which diverts blood flow from other organs - and fluid loss through sweating - with decreased blood volume. Some patients have found that cooling vests and increasing fluid intake can help mitigate these effects somewhat.

    Diet 
    Patients with orthostatic hypotension are encouraged to increase their dietary sodium and water intake in an attempt to augment blood volume. Because eating large meals diverts blood flow to digestive organs, patients may feel worse following large meals. Therefore, they may benefit from eating several small, low-carbohydrate meals instead of a few larger ones. In addition, some patients have found that certain foods trigger their symptoms, including alcohol, caffeinated beverages, and carbohydrates.

    Physical Counter Maneuvers 
    Patients are encouraged to be observant of presyncope symptoms, including lightheadedness, dizziness, weakness, and vision changes. When these symptoms occur, patients should lie down immediately. If lying down is not possible, patients should try to move around and especially use their leg muscles. Some patients stand on their toes, others cross their legs and flex the muscles in the legs and buttocks to drive blood out of the legs and encourage blood flow from the legs to the heart. 
    Moving slowly when transitioning from lying to standing may reduce the dizziness and lightheadedness that occur with orthostatic hypotension. Rather than jumping out of bed in the morning, patients are encouraged to breathe deeply for a few minutes and slowly sit up before standing. 

More Information

Postural Orthostatic Tachycardia Syndrome (POTS) is defined as a chronic state (>6 months) of consistent orthostatic tachycardia (>30 bpm heart rate increment from lying to standing) and typical symptoms that are worse on standing and are relieved by lying down. The heart rate elevation in POTS typically occurs in the absence of significant orthostatic hypotension (>20/10 mmHg blood pressure drop from lying to standing). Patients with vasovagal syncope rarely meet the criteria we use for POTS.

  1. Signs and Symptoms

    The following signs and symptoms may indicate POTS if they are experienced for longer than six months.

    Upright posture symptoms may include: 

    • Visual changes 
    • Discomfort in the head and neck 
    • Throbbing of the head 
    • Poor concentration ("brain fog") 
    • Tiredness 
    • Weakness 
    • Occasional fainting 
    • Nausea 
    • Chest discomfort 
    • Shortness of breath
    • Lightheadedness, palpitations, and tremulousness during standing

    Other symptoms that have been reported in patients with POTS include: 

    • Abdominal discomfort and bloating 
    • Constipation 
    • Diarrhea 
    • Changes in sweating 
    • Sleep problems 
    • Sense of anxiety

  2. Testing and Diagnosis

    Testing for patients with orthostatic intolerance includes tests of the cardiovascular and nervous systems. Some procedures are designed to examine specific parts of these systems, and others are intended to evoke patient symptoms in a controlled setting where doctors can monitor the physiology responsible for the symptoms. 

    Diagnostically, POTS is defined as a sustained heart rate increment of >30 beats/minute within 10 minutes of standing without orthostatic hypotension (the blood pressure does not decrease by more than 20/10 mmHg). This may be accompanied by symptoms of cerebral hypoperfusion and autonomic overactivity that are relieved by lying down. 

  3. Treatment

    The causes and pathophysiology of POTS vary between patients. Because of this, not all patients will respond the same way to a treatment. Therefore, treatment plans must be tailored to each patient for maximum efficacy. Some treatments that may be effective are outlined below. 

    High-salt diet  
    Because low blood volume is found in many patients with POTS, patients are encouraged to increase their salt intake by up to 10 grams/day in an attempt to increase plasma volume. Ideally, this can be done with diet alone, but prescription 1 g salt tablets can be given to supplement sodium intake. An increase in water intake should accompany this measure. 

    Exercise 
    Exercise, including both aerobic and resistance training, has been shown to be beneficial for patients with POTS. It helps to reverse "deconditioning" and can also increase blood volume. Vigorous exercise can sometimes acutely increase symptoms and fatigue. Therefore, patients are encouraged to start slow and gradually increase exercise as tolerated.  
    Research on the benefits of exercise can be found at PubMed. 

    Fludrocortisone  
    Fludrocortisone is a mineralocorticoid that is an analogue of aldosterone. It acts on the kidney to conserve sodium and water and is used to increase plasma volume, especially in patients with measured or suspected low blood volume.

    Propranolol  
    Propranolol is a beta blocker that blocks receptors for epinephrine and norepinephrine to prevent the physiological effects of these catecholamines (produced by the sympathetic nervous system). Propranolol has been shown to decrease heart rate and acutely improve symptoms in patients with POTS.  
    The use of beta blockers in POTS is controversial, but some patients who have previously failed beta-blocker therapy have had success with propranolol.  
    Research on the effects and benefits of propranolol can be found at PubMed. 

    Desmopressin  
    Desmopressin (DDAVP) is an antidiuretic that decreases urine production by increasing water reabsorption in the kidneys; DDAVP therefore increases fluid retention and plasma volume. In addition, DDAVP has been shown to decrease standing heart rate, improve symptoms, and decrease the change in heart rate with standing without significantly changing blood pressure.  
    Side effects associated with DDAVP include headaches, edema, and hyponatremia (low salt concentration in the blood). Patients with POTS are encouraged to drink copious amounts of water, and DDAVP causes free water retention. Therefore, it is theoretically possible that regular use in POTS could lead to severe hyponatremia. Caution should be exercised in using DDAVP regularly without data from long-term studies that evaluate the side effects associated with regular use; patients using DDAVP are instructed to take no more than one dose per week. 
    Research on the effects and benefits of DDAVP can be found at PubMed. 

    Pyridostigmine  
    Pyridostigmine is an acetylcholinesterase inhibitor that decreases the degradation of the neurotransmitter acetylcholine. Pyridostigmine has been found to decrease standing heart rate and improve symptoms in patients with POTS. 
    Research on the effects and benefits of Pyridostigmine can be found at PubMed.

    Midodrine 
    Midodrine is an alpha-1 agonist that causes vasoconstriction and helps to decrease venous pooling. This may be beneficial as some patients have excessive blood pooling in their extremities when they are upright.

    Central Sympatholytics 
    Central sympatholytics include clonidine (Catapres) and methyldopa (Aldomet). These drugs act on the brain to decrease sympathetic nervous system tone, making them the most beneficial at stabilizing heart rate and blood pressure in patients with central hyperadrenergic POTS.

  4. Lifestyle Measures

    Lifestyle strategies are important in managing POTS. Some measures that may be effective are outlined below.

    Compression Stockings 
    These stockings compress the legs to help decrease peripheral venous pooling and increase venous return to the heart. The most effective stockings offer at least 30-40 mmHg of compression and are waist-high.

    Sleep 
    Sleep problems have recently been found to correlate to health-related quality of life in POTS. This research can be found at PubMed. Therefore, POTS patients are encouraged to practice good sleep hygiene, including: 

    • Having a set bedtime and time to wake up 
    • Avoiding alcohol, caffeine, and exercise before bed 
    • Avoiding napping when possible 
    • Optimizing bedroom comfort, including lighting and temperature

    Temperature 
    Many patients find that heat is a major trigger of their symptoms since it causes vasodilation - which diverts blood flow from other organs - and fluid loss through sweating - with decreased blood volume. Some patients have found that cooling vests and increasing fluid intake can help mitigate these effects somewhat.

    Diet 
    Patients with POTS are encouraged to increase their dietary sodium and water intake to augment blood volume. Because eating large meals diverts blood flow to digestive organs, patients with POTS may feel worse following large meals and, therefore, may benefit from eating several small meals instead of a few larger meals. In addition, some patients have found that certain foods trigger their symptoms, including alcohol, caffeinated beverages, and carbohydrates.

    Physical Counter Maneuvers 
    Patients are encouraged to observe presyncope symptoms, including lightheadedness, dizziness, weakness, and vision changes. When these symptoms occur, patients should lie down immediately. If lying down is not possible, patients should try to move around and especially use their leg muscles. Some patients stand on their toes, while others cross their legs and flex the muscles in the legs and buttocks in an attempt to drive blood out of the legs.

More Information

Vasovagal syncope (VVS) - sometimes referred to as neurally mediated syncope, neurocardiogenic syncope, or more commonly fainting - occurs when an individual faints due to their body overreacting to certain stimuli or triggers. These triggers can include things such as the sight of blood or exaggerated emotional distress. 

The body's overreaction to a given trigger causes a sudden drop in heart rate and blood pressure (hypotension). This hypotension results in decreased blood flow to the brain and loss of consciousness if sufficiently severe or presyncope if less severe. These changes in heart rate and blood pressure are due to increased parasympathetic tone and an associated inhibition of sympathetic outflow.

  1. Signs and Symptoms

    Patients may experience a number of the following symptoms just before fainting (pre-syncope):  

    • Pale skin  
    • Lightheadedness 
    • Tunnel vision 
    • Nausea 
    • Feeling warm 
    • A cold, clammy sweat 
    • Yawning 
    • Blurred vision

    During a vasovagal syncope episode, bystanders may notice:  

    • Jerky, abnormal movements 
    • A slow, weak pulse 
    • Dilated pupils

  2. Testing and Diagnosis

    Diagnosing vasovagal syncope typically involves ruling out other possible causes of fainting, particularly heart-related problems. Once these have been ruled out, a tilt table test may be used to examine the effects of postural changes on patients' heart rhythm and blood pressure. 

  3. Treatment

    In many cases, vasovagal syncope does not require treatment. Physicians may help to identify fainting triggers and discuss ways patients might avoid them. However, if patients experience vasovagal syncope frequently enough to interfere with their day-to-day quality of life, the treatments below may be effective in managing the disorder.

    Compression Stockings  
    These stockings compress the legs to help decrease peripheral venous pooling and increase venous return to the heart. The most effective stockings offer at least 30-40 mmHg of compression and are waist-high.

    Physical Counter Maneuvers  
    Patients are encouraged to be observant of presyncope symptoms, including lightheadedness, dizziness, weakness, and vision changes. When these symptoms occur, patients should lie down immediately. If lying down is impossible, patients should try use their leg muscles. Some patients stand on their toes, others cross their legs and flex the muscles in the legs and buttocks to drive blood out of the legs and encourage blood flow from the legs to the heart. 

    Temperature  
    Many patients find that heat is a major trigger of their symptoms since it causes vasodilation - which diverts blood flow from other organs - and fluid loss through sweating - with decreases blood volume. Increasing fluid intake can help mitigate these effects. 

    Surgery 
    Very rarely, inserting an electrical pacemaker to help regulate the heartbeat may help those who have not found success by ways of other treatments. 

More Information