  What normally occurs when a person stands up is the brain sends a message to the heart to increase the heart rate to bring up the blood from the legs (a normal response) to supply the brain & upper part of the body. This is the body's normal way to combat the natural effects of gravity. However with NMH the brain sends the message that the heart rate should be slowed down and the blood vessels dilate causing a drop in both the heart rate and blood pressure. This reflex does not occur when the person first stands up as in Orthostatic Hypotension but occurs after the person has been standing for an extended period of time. (People with severe cases have symptoms after standing for a shorter period of time.) This drop in blood pressure can lead to several symptoms which includes: Fainting Recurrent lightheadedness or feeling faint or weak. Unusual difficulty with prolonged fatigue after a modest amount of physical activity which can last 24 to 72 hours and could interfer with many daily activities. Muscle aches which can coincide with the fatigue. Headaches Mental confusion (difficulty concentrating, staying on task, paying attention, easily distracted or finding the right words) often described as a "mental fog". Feeling clammy or heated. These symptoms can be triggered by a number of things which includes: After prolonged periods of quiet upright posture such as standing in a long line, standing in the shower or sitting up for a long time. After being in a warm environment (Ex. hot shower or bath, sauna, being outside on a hot humid summer day, or in a hot crowded room) After emotionally stressful events such as when scared or anxious Some get symtoms after eating (blood diverts to the intestines Working out side in moderate heat (ex. spreading a lot pine needles or mowing the yard) can also bring on symptoms. Everyone is suspectible to activation of the vaso-vagal reflex causing NMH symptoms but each person's susceptibility is effected by genetic make-up, dietary factors, psychological make-up and acute triggers such as infections and allergies. A person is determined to have a clinical case of NMH when there is sufficiently early triggering of this refex to cause symptoms. However as with any medical condition the severity or degree of the symptoms may vary from person to person. Some people are genetically predisposed to NMH. Research has shown it tends to run in families. One common problem identified with people with NMH is a low salt in their diet. Salt helps retain fluid in the blood vessels and help maintain blood pressure. Salt can cause blood pressure to be higher (which isn't good for those with hypertension) which does decrease problems with blood pressure which tends to get too low as in NMH. NMH is diagnosed by using the tilt table test which reveals a drop in blood pressure and may reveal a drop in heart rate. (I have found some medical literature (and MD's) determine a person has NMH when both the heart rate and blood pressure drops a certain amount while others report a drop in blood pressure alone signifies NMH.) Basically the tilt table test measures heart rate and blood pressure while lying down (during resting state), then standing at a 70 degree angle for 45 minutes. The person is lowered while medication, such as isoproterenol, is administered through an IV to increase the heart rate to about 10% above the resting heart rate and then the patient is returned to the 70 degree angle for 15 minutes. The third part of the test the medication is increased to farther increase the heart rate then the person is returned to the upright position for 10 minutes. Technically the environment is suppost to be quiet and non-stimulating to eliminate distractions and the patient is requested to fast after midnight prior to the test (to reduce chance of vomiting). The patient is strapped on the table to hold the patient on the table in case of fainting and also to decrease the human nature of compensating for the blood pooling in the legs by figeting. Thoughout the test the nurse or technician monitors the patient's symptoms. The tilt table test is determined to have a positive result for NMH if there is a significant drop in blood pressure (ex. 60/30) and a drop in heart rate. However some consider a positive diagnosis with a drop in blood pressure but not necessarily a drop in heart rate. Symptoms brought on by this test may include nausea, vomiting, feeling faint or weak, vision becoming blackened, popping sound in ears, anxiety or fear, fainting, and fibromyalgia symptoms for 2-3 days after the test (feeling weak & shaky, muscle weakness or pain upon slight exertion (ex. walking up flight of stairs). This pain may last only a few minutes or last longer. NMH can be treated by adjusting the diet and if symptoms are bothersome medication can be prescribed by your doctor. Many people compensate to decrease symptoms by avoiding situations (like hot baths) that trigger symptoms, move around rather than stand or sit for extended periods of time. If they are stuck in a line or long meeting they may "fidget" by moving their legs to increase blood flow upward. Other ways you may reduce symptoms is decrease stress, increase exercise and increase fluid intake. Some people will increase their salt intake a little. However with some medical conditions, such as high blood pressure you should limit salt intake. Some research has shown a link between NMH and CFS however some research did not support these findings. Therefore research will likely continue to see if there is a link between these 2 conditions. Some people who suffer fatigue have found that NMH is the cause of their fatigue which with proper treatment found the fatigue did improve. Some found that treatment did not improve the fatigue.  Return to Conditions that cause dizziness Other links on NMH General information brochure on neurally mediated hypotension and its treatment Neurally Mediated / Neurocardiogenic Syncope National Dysautonomia Research Foundation's site Two research studies on NMH Research press release on NMH and CFS The connection between chronic fatigue syndrome and neurally mediated hypotension ORTHOSTATIC INTOLERANCE There are 2 types discussed in this artical. "There are many types of OI, but two forms have been linked with CFIDS in research studies: NMH and postural orthostatic tachycardia syndrome (POTS)." NMH is a precipitous drop (at least 20-25 mm Hg) in systolic blood pressure when standing. The blood pressure drop is accompanied or preceded by an increase in symptoms. POTS is a rapid increase in heart rate (pulse) of more than 30 beats per minute (bpm) from baseline, or to more than 120 bpm total, during the first 10 minutes of standing. It is also known as chronic orthostatic intolerance, or COI. Postural Orthostatic Tachycardia Syndrome Extensive information on POTS and related conditions. Orthostatic Intolerance Extensive amount of information on orthostatic abnormalities especially found in CFS. Also includes tilt table test and other tests used to detect orthostatic abnormalities. General information on NMH by the Neurally Mediated Hypotension Working Group Johns Hopkins Hospital Orthostatic stress "People with Postural Orthostatic Tachycardia Syndrome (POTS) and Neurally Mediated Hypotension (NMH) have a difficult time obtaining appropriate medical care and are often subject to rude treatment by doctors and medical workers. Aside for a few advanced centers with specialized autonomic dysfunction clinics (Johns Hopkins, Mayo Clinic, Vanderbilt University, Medical College of Ohio), the medical community does not seem to want to take the time to understand the phenomena of chronic orthostatic intolerance. Here is a quick mind experiment that can help physicians appreciate the problems patients with these dysautonomia disorders face every day." Several abstracts of research on NMH, CFS and FM Neurally Mediated Hypotension and Chronic Fatigue Syndrome Peter C. Rowe, MD, and Hugh Calkins, MD, Baltimore, Maryland. Based on a talk (by PCR) given at the American Association for Chronic Fatigue Syndrome, October 1996. Dr. Rosner's research. His surgery is controversial but researchers are now researching his theory. Michelle Aiken's story of NHM Robyn's web page on NMH Teri's NMH Page Our FM & CFIDS World Additional information on NMH Borderline or subclinical case of NMH When symptoms are mild and doesn't cause medical concern. Want to participate in a tilt table research study? If you do decide to do this, take it from experience, be sure to research what you are getting into and what this test reveals. Read my experience with this. Another person's experience with a true positive response to the test. University of Michigan Health System fact sheet on the tilt table test These sites should give you a basic understanding about what the tilt table test is, what to expect and what the aftermath could involve if you have a positive test result.   |