The condition of a slow heart rate is known as Bradycardia and pertains to rates below 60 beats per minute. It can be normal for some to have a resting heart rate below 60 beats, athletes for example, some non athletes as well, and people on certain medications. Also, doing a search, the following were other reasons for Bradycardia:
"Bradycardia can be caused by:
Conditions that can slow electrical impulses through the heart. Examples include having a low thyroid level (hypothyroidism) or an electrolyte imbalance, such as too much potassium in the blood.
Some medicines for treating heart problems or high blood pressure, such as beta-blockers, antiarrhythmics, and digoxin."
Also, there are 4 chambers in a heart, two on top know as the atria, two on the bottom, known as the ventricles.
On the top of the heart is the heart's natural pacemaker, called the SA (Sino Atrial Node). This node is influenced by the body's parasympathetic nervous system, which can drastically slow the heart rate. It's also influenced by the sympathetic nervous system, which can speed up your heart rate.
Between the top of your heart and the bottom is the AV (Atrioventricular Node).
Normally the SA node discharges, the atria contract, the signal travels to the AV node, causing it to discharge, and this causes the ventricles to contract. If something interferes with the SA node discharge or conduction, the AV node will eventually discharge on its own. This will cause a slow heart rate.
When this happens, a pacemaker can be used to supply the missing or poorly conducted SA node signal.
If the SA Node or its proper conduction work some of the time, but not others, a Demand Pacemaker is used. This allows the SA node to supply the pacing of the heart much of the time.
If the SA Node or its proper conduction are no longer functioning, a pacemaker will supply all of the function of the SA Node, this is known as being Pacemaker Dependent.
I'm curious, did your doctor give you any idea what he thinks the issue is? Did he tell you the name of the phenomenon? Did your doctor send you home and arrange for a cardiology appointment?
Not to suggest that the following applies to you, but I would be remiss not to mention it. If your profile is correct and you live in Colorado, I realize the changes in the drug laws in that state. The use of the identified drug can produce Bradycardia, seemingly through the parasympathetic system. I'm not sure how long the reversible effect lasts.
Cannabis has a biphasic effect on the autonomic nervous system, depending on the dose absorbed. Low or moderate doses can increase sympathetic and reduce parasympathetic activity, producing a tachycardia and an increase in cardiac output. In contrast, higher doses inhibit sympathetic and increase parasympathetic activity, resulting in bradycardia and hypotension. Reversible ECG abnormalities affecting the P and T waves and the ST segment have been reported. It is not clear whether these changes occurred as a direct result of cannabis, independent of its effect on the heart rate.
Although supraventricular and ventricular ectopic activity can occur, life-threatening tachy- or bradyarrhythmias have not been reported. In patients with ischemic heart disease, cannabis increases the frequency of anginal symptoms at low levels of exercise. This occurs as a result of a drug-induced increase in heart rate and myocardial contractility that increases myocardial oxygen demand.
Oh no cannabis for me!! We aren't sure what us causing it. My nurse is supposed to schedule an appt with the cardiologist. He only comes down a couple times a month. It should be soon though.
I do not have any experience with a pacemaker but I know several people who use them the device seems to be unobtrusive and effective. The main concern as I understand it is a slow hear may just stop. Don't take this as anything like a diagnosis of your case, 40 is just slow not near a stop. I mention only in the belief that the safety offered by a pacemaker may be the decision point. Not sure it will keep you up at, say 60 bpm, but that may be an advantage.
I'm a 27 years old male and my heart rate gets as low as 45 when I'm sleeping, however I don't have any symptoms like you do. I do have Inappropriate Sinus Tachycardia and I'm still trying to figure out why I have a low heart rate. If you're having symptoms that's not a good thing. There probably is an explanation for your case. Just think long and hard about your options if your doc does decides that a pacemaker will help. Can't rush these things ya know. I wish you the best.