# Heart rate doubling

• Medical

## Main Question or Discussion Point

A long time ago I read somewhere that people with low heart rates (e.g. athletes) can experience a doubling of their heart rates when they get older (sort of bifurcation in which a single heart beat evolves into two heart beats).

I tried to find out more about this phenomena but I didn't find anything. So, I was wondering if this is a common phenomena in people with low resting heart rates (below 40 beats per minute).

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Tsu
Gold Member
I checked this with one of my ER docs for you. He said that it is not a common phenomenon as people age, but may be one more in keeping with maintaining the athletic abilities. Normal heart rate is 80-100, so as one ages AND cuts back on their athletic abilities, their heart rate will most likely go up. However, a very active 60+ y/o can have a heart rate of 50-80.

I'm not sure I know what you mean when you're talking about a 'sort of bifurcation in which a single heart beat evolves into two heart beats'. Bifurcation means the splitting or branching of one thing into two things. What would be bifurcating here? The heart rate would only increase to be more efficient as one ages and decreases their athletic abilities. It wouldn't cause one beat to become two.

Astronuc
Staff Emeritus
I tried to find out more about this phenomena but I didn't find anything. So, I was wondering if this is a common phenomena in people with low resting heart rates (below 40 beats per minute).
A heart rate of 40-50 would be normal in a highly trained athelete at rest. When I was playing sports and running daily, my rest heart rate was between 40-50. Now its about 90. If I exercise, e.g. running, it increases to about 130.

berkeman
Mentor
Maybe by "bifurcation" he is refering to A-fib? That could appear to be a splitting of a single heartbeat into more....

http://www.americanheart.org/presenter.jhtml?identifier=4451

That AHA article didn't discuss athletes or any other group being predisposed to developing A-fib, though.

I looked a little for possible predispositions for A-fib, and found these:

Caffeine may actually help avoid A-fib http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2257921

Mutations in the Connexin 40 Gene http://www.cardiologyonline.com/journal_articles/Mutations_in_the_connexin.htm

This is the best article I found so far: "Epidemiology of Atrial Fibrillation: Risk Factors and Hazards"
http://www.fac.org.ar/cvirtual/cvirteng/cienteng/epeng/epc0005i/ikannel.htm
In the Framingham Study only hypertension and diabetes were significant independent predictors of AF increasing the risk 1.5 fold. Because of its high population prevalence, hypertension is responsable for more AF (14%) than any other risk factor. Overt cardiac conditions impose a substantially greater risk than the cardiovascular risk factors with heart failure imposing a risk factor adjusted hazard of 4.5 in men and 5.9 in women. Valvular heart disease also imposed a major hazard that was greater for women (HR= 3,4) than men (HR= 1. 8). Myocardial infarction increased the risk factor adjusted AF hazard by only 40% and only in men.
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Moonbear
Staff Emeritus
Gold Member
You wouldn't count atrial fibrillation as a splitting of heartbeats though, as it's only an irregular pattern of one component of a heart beat.

Here's an example showing the EKG for normal sinus rhythm and for someone with an atrial fibrillation. http://sprojects.mmi.mcgill.ca/cardiophysio/atrialfibrillation.htm [Broken]

An increase in heart rate above normal would be a tachycardia, not a fibrillation. But, as Tsu mentioned, the "normal" range for heart rate can be from about 60-100 (with most falling between 70-80) bpm. So, it wouldn't require any abnormalities in cardiac function for someone who is athletic and young with a heart rate around 50 to seem to double their heart rate as they get older and out of shape and have a heart rate around 100.

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berkeman
Mentor
You wouldn't count atrial fibrillation as a splitting of heartbeats though, as it's only an irregular pattern of one component of a heart beat.

Here's an example showing the EKG for normal sinus rhythm and for someone with an atrial fibrillation. http://sprojects.mmi.mcgill.ca/cardiophysio/atrialfibrillation.htm [Broken]

An increase in heart rate above normal would be a tachycardia, not a fibrillation. But, as Tsu mentioned, the "normal" range for heart rate can be from about 60-100 (with most falling between 70-80) bpm. So, it wouldn't require any abnormalities in cardiac function for someone who is athletic and young with a heart rate around 50 to seem to double their heart rate as they get older and out of shape and have a heart rate around 100.
Great website, Moonbear, thanks for the link. From the EKGs, it looks like I was thinking more of Atrial Flutter, not A-fib. When taking some patient's pulse, I've definitely felt what seemed like some missing beats, mixed with some double-beats. It's not an overall doubling of heart rate (which I guess is what the OP was asking about), but rather an irregular rhythm containing what feel like some double beats.

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Moonbear
Staff Emeritus
Gold Member
Great website, Moonbear, thanks for the link. From the EKGs, it looks like I was thinking more of Atrial Flutter, not A-fib. When taking some patient's pulse, I've definitely felt what seemed like some missing beats, mixed with some double-beats. It's not an overall doubling of heart rate (which I guess is what the OP was asking about), but rather an irregular rhythm containing what feel like some double beats.
If you're detecting the irregular rhythm in the pulse, that would more likely be a left ventricular problem, not atrial. Blood being pumped out into general arterial circulation is coming from the left ventricle, so the pulse you feel is the pattern of the left ventricle pumping the blood through the body. Generically, feeling a combination of missed and rapid beats would be a ventricular arrhythmia.

The atrial problems are something that someone with a trained ear could pick up by listening to heart sounds with a stethoscope, or in the EKGs, but not just by feeling for an arterial pulse.

berkeman
Mentor
Blood being pumped out into general arterial circulation is coming from the left ventricle, so the pulse you feel is the pattern of the left ventricle pumping the blood through the body. Generically, feeling a combination of missed and rapid beats would be a ventricular arrhythmia.
Makes perfect sense. Thanks, MB.

Andy Resnick
There's also Long QT syndrome:

http://en.wikipedia.org/wiki/Long_QT_syndrome

The timing pulse can kinda-sorta bifurcate, leading to ventricular arrythmia and death. Most deaths occur during bradycardia (slow heartbeat)- while sleeping, for example.

Tsu
Gold Member
Long QT syndrome is usually hereditary. There are acquired forms, also, but none have to do with being an athlete as a youth... Use of the antibiotic erythromycin is one of the ways to 'acquire' it. More googling of this will give you more info.

Tsu
Gold Member
Great website, Moonbear, thanks for the link. From the EKGs, it looks like I was thinking more of Atrial Flutter, not A-fib. When taking some patient's pulse, I've definitely felt what seemed like some missing beats, mixed with some double-beats. It's not an overall doubling of heart rate (which I guess is what the OP was asking about), but rather an irregular rhythm containing what feel like some double beats.
You know, that sounds somewhat consistant with mitral valve prolapse (MVP). I have MVP and my heart will frequently skip a beat and give 'double beats' as well. It feels weird.

Moonbear
Staff Emeritus
Gold Member
You know, that sounds somewhat consistant with mitral valve prolapse (MVP). I have MVP and my heart will frequently skip a beat and give 'double beats' as well. It feels weird.
MVP will certainly give you strange "flutter" sensations. I don't know how (or if) that would show up on an EKG though (as you must know, diagnosis is confirmed by ultrasound exam of the heart after detection of a murmur). I guess that's why we have all these other diagnostic tests like EKG, ultrasound, etc., because a lot of things can feel the same to the patient.

Tsu
Gold Member
MVP will certainly give you strange "flutter" sensations. I don't know how (or if) that would show up on an EKG though (as you must know, diagnosis is confirmed by ultrasound exam of the heart after detection of a murmur). I guess that's why we have all these other diagnostic tests like EKG, ultrasound, etc., because a lot of things can feel the same to the patient.
My 12-lead EKG showed that I'm throwing both PVC's and PAC's, but I am also not sure if that is related to my MVP - and yes, the MVP was dx'd by echocardiography. It still feels weird...