I do appreciate your concerns since you have undergone so many tests without a definite diagnosis. It appears as though you have a fall in blood pressure only when you are exercising (exercise induced hypotension).
This fall in BP is usually due to blockage in heart arteries, valvular heart disease, abnormal enlargement of heart, abnormal heart rhythms such as supraventricular or ventricular tachycardia or due to abnormal function of the autonomic nervous system (vaso-vagal syncope). Of these the heart related causes have been ruled out in your case. However, a holter test should be performed which should include days prior to running, during run and post running. Sometimes a holter test is able to capture arrhythmias missed during stress test.
However, vaso-vagal syncope needs to be looked into. Blood pressure monitoring, head-upright tilt table test, ambulatory blood pressure recording through holter are all required for diagnosis. Also, plasma noradrenaline levels may need to be measured post exercise.
Other factors which should be looked into are hyperthermia during exercise causing major dilatation of the blood vessels of the skin to release the excess heat. Hypoglycemia during exercise is another possibility and blood sugar should be tested immediately at the onset of symptoms. Also it is very important to measure arterial blood gases like oxygen and carbondioxide to rule out hypoxia and hypercapnia, respectively.
Make a conscious effort to drink fluids (not plain water but juice, lemonade, soups, herbal tea, etc), and eat at regular intervals. Normally this helps. Isometric and aerobic exercises should be built into your daily routine to build up the strength of blood vessels in order to avoid the fall in blood pressure while you exercise.
Please discuss the above factors with your doctor. Hope you can continue to run as you could two years ago! Good Luck and take care!
Tests of autonomic function were clean, and so was tilt-table test. Vaso-vagal syncope also usually occurs with drop in HR, right? Not increase, like my symptoms.
Blood gases were also monitored during long treadmill test - all normal. Cardiologist had me taking extra salt and water to no avail, so ruled out dehydration. Also got my body close to hyponatremia during run to see if it would change symptoms - no.
I have taken carbohydrate gels when symptoms occur with no change, so rules out hypoglycemia.
Symptoms occur less often in cold weather (<40F), but still have occurred. And, symptoms have not occurred in 70+ weather. Does this rule out hyperthermia?
So, items not ruled out are:
holter monitor for arrhythmias
check plasma noradrenaline levels after exercise
Yes, looks like hypothermia is ruled out.
rise and heart rate and respiratory rate is a normal response to exercise. Usually the blood pressure also increases. However if there is ventricular or supraventricular tachycardia then the BP may fall. Also, since all episodes of running do not cause a fall in BP, it is important to wear a holter for some weeks while you try running.
Also, if the adrenaline/nor adrenaline release is not in tandem with the exercise, then BP may fall.
So, yes, these two aspects should be looked into.
please read hypothermia as hyperthermia
I confirmed with cardiologist that there was NO ventricular or supraventricular tachycardia when BP fell.
Hmm --The fall in BP is due to three main reasons: The muscles of legs do not contract enough at some point of time and this reduces blood flow to heart and reduces cardiac output and thus the BP. The second reason is dilatation of blood vessels of skin. The third reason is lactic acid accumulation in muscles which causes dilatation of blood vessels. Sometimes no cause is found in athletes and they need to find out the minimum distance they can run without an 'episode'.
All I can suggest is that on days you run, please chart what you eat, the quantity of water you drink, and the level of exercise you do--miles you run, how you warm up and how you cool down. Either wear a holter on every run or get an ECG soon after an episode. Also you need to know you blood lactic acid, blood oxygen level and blood carbon dioxide level and blood electrolytes immediately after an 'episode'.
The only other link I can visualize from the information shared by you is raised histamine post exercise. This can also cause dilatation of limb blood vessels causing dramatic fall in BP. Hence, this needs to be followed up. Some types of diets (you need to consult a nutrition expert for this) and warm up exercises can help reduce the histamine level post or during aerobic exercise. Anti-histamines may be prescribed in severe cases.
I am sorry, but beyond this, I cannot really help you much on net.
I took an H1 and an H2 anti-histamine for several months and cromolyn sodium immediately prior to running - no help. So, we ruled out high histamine as cause. And, I completely changed my diet for periods of time, including fasting, low-histamine foods, and 6 weeks of raw fruit and veggies, with no change. I kept a full diet log for several weeks and found no pattern. I did not, however, track water intake. I will do that for the next couple of weeks.
Since problem can occur after only 2 easy miles (0% anaerobic) into a run, lactic acid buildup is unlikely to be the cause, right?
A fourth possible reason for BP drop is carotid body tumor, which was checked via scan.
I will arrange with local Dr to do blood work after I run around their office for a few miles. I also purchased a BP wrist cuff to monitor BP more closely during runs - will use arm across the chest/heart method. I will also try 20 minute fast-walk warm ups so skin capillaries dilate before running to see if it changes occurrence of episodes.
Will keep you updated on the test results.
Fast-walked for 20 min while monitoring BP & HR.
Rest: BP=115/84, HR=63. Temp 78F with 70% relative humidity. Wore long sleeve black shirt to maximize capillary response.
12' 126/93 & 105
18' 137/88 & 134
21' started jogging, slow pace
23' 126/86 148
28' 120/80 155
36' HR at 166 and couldn't get BP reading twice. Then 115/90 with HR at 137.
41' HR at 162 and couldn't get BP reading one. Then 124/92 with HR=144.
Felt weak and a little nausea, lightheaded. Sweating to point of dripping some.
Decided to take temp because of your comment about hyperthermia and temp at 96F.
As body "cooled off" (stopped sweating) body temp rose.