Dive if Hypertension is Well-controlled
If you have mild, well-controlled hypertension with none of it’s complications, you have nothing to worry about if you are diving or plan to dive. Well-controlled hypertension means a pressure of less than 145/90 (160/95, BSAC) and complications of hypertension include renal failure, eye problems, coronary disease.
Because divers with a clear diagnosis of hypertension may have exaggerated responses to exertion, immersion and cold stresses they should not dive until their high blood pressure has been investigated and appropriately treated.
Acute Heart failure
Wilmshurst, in 1989, reported eleven divers with unrecognized or untreated hypertension who developed acute heart failure (with pulmonary edema) during the course of a dive in cold water.
The diver who is under treatment and is controlled on medication should be allowed to dive, if there is no target organ damage (eye, kidney or heart). Of course, consideration should be given to the interaction of diving and the medication used to treat the diver. Caveats are given for the use of beta blockers and diuretics.
Beta Blockers
If you are on B-blockers–you should have a treadmill test done and if you can exercise without chest pain, BP elevation, EKG changes or arrhythmias (and without fainting), then I would think you to be OK for sensible diving. Be sure and run this past your doctor first, however! Beta blockers blunt the response of the body to the effects of exercise and can cause syncope in the maximally challenged diver. Syncope (fainting) underwater could, of course, lead to drowning and would definitely not be good for the diver or his buddy. Divers who are in excellent physical condition should have few problems.
Beta blocker drugs have the ability to alter a divers response to the demand from a heavy workload and can limit the heart rate response, causing fainting with exercise (exertional syncope). These prospective divers should undergo stress testing to ascertain exercise capacity.
Other drugs, such as dyazides, can cause postural hypotension (positional low pressure) or low serum potassium (blood chemistry) and can dehydrate the diver, an increased risk for a decompression accident.
Hypertension a Risk factor in Coronary Artery Disease
Since hypertension is a definite risk factor in coronary artery disease and stroke, the diver with any type of hypertension needs careful evaluation of his heart and kidneys for damage. Severe hypertensives requiring complex programs to control their condition should not dive as professionals or as sport divers.