Anyone gone from one lead to two leads? Any changes in athletic performance?

Restoring A/V synchrony

by crustyg - 2020-07-12 03:02:28

However they can manage it, restoring A/V synchrony with an atrial lead will bring a big improvement in cardiac output, assuming healthy heart muscle.  Not only do you get much better pre-filling of the ventricles (so larger volume of blood expelled per beat) but also the heart muscle beats more powerfully (again, given the above caveat).  Heart muscle is unique in the body: up to a point, the more you stretch it, the more powerfully it contracts, irrespective of nerve input, fight-or-flight hormones.  So pre-filling the ventricles with more blood stretches the ventricular muscle so it beats more powerfully.  Control mechanisms then operate to control BP, strength of contraction etc.  For me, my 50bpm post PM gave me 50 quite small heart beats compared to 38 kicks in the chest as I was drifting off to sleep.  Athletic folk with AFib reading this might be muttering 'lucky devils' - not everyone can have this, and my EP doc tells me that the natural history of my condition leads to AFib.  Enjoying it while I can.

Your Q: it depends on the function of your SA-node.  There's a good chance that this is damaged, or doesn't respond as well as it should when you need an increased HR.  Mine is almost completely silent, so my pacing is nearly 100% dependent on the PM providing an atrial activation (I still have some escape pacing from my AV-node).  But in general *yes*, which is as it should be.  You (probably) still have an intact nerve supply to the heart, and this, combined with electrical activation from the RA, is the best way for your heart to operate.

Downside to adding in an atrial lead?  Nothing I've noticed.  Nicely embedded in RA appendage, no need for NOACs, no LV-remodelling from my apical-RV lead (it's turned off), nice little scar over my quite large extended-life PM (pros- and cons- to having a PM that might last 15years before battery replacement.  But (so far) healthy heart muscle, healthy AV-node, no nasty disease process wrecking my heart - all good.  Not everyone is so lucky.  Friends are falling by the wayside with horrible cancers, struggling daily with incurable chronic disease, being knocked off their bike by crazy kids =>hospital with multiple significant injuries, etc.  Turns out life is a lottery - who knew!

QQ

by SNORTINGDONKEY - 2020-07-12 10:55:13

Hi! Thank you for answering...

I was told that my SA node is working fine. But I guess this brings up a (hopefully not too stupid) question: 

If my SA node is beating independently and regulating the upper chambers of the heart AND I only have the AV lead to regulate the lower chambers of the heart, the heart rate that I see on my Apple Watch is what exactly?

I guess what I am saying is that, in my case, I understand that while exercising, my body might be telling the SA node to fire faster, let's assume, which it does. But then that signal pathway to the AV node is broken and so obviously the lower chambers will beat per the PM's instructions independently of the firing of the SA node. So it is possible that the SA node is firing at a rate that is tantamount to 165 bpm AND the AV node is firing signals that cap out at 130 bpm. In this scenario, how does the PM (or my Apple Watch for that matter), count the bpm?

Ventricular electrical signal will swamp atrial signal

by crustyg - 2020-07-12 12:27:11

I'm not an Apple fan, so I'm no expert on the technologies in their gadgets.  *Most* wrist HR monitors are pulseoximeters, which work by detecting changes in optical absorption, deriving a waveform from that data and using the biggest deltas to assume that each one reflects a pulse as the LV ejects blood into the aorta, and hence pushes red-cells into the small arterioles that feed the capillary beds.  Often wrong when not all LV ejections are of the same force and not very good when the optical signal is unstable due to exercise - the very first machines fitted over the pinna of the ear to give a really stable signal.

A *few* clever wrist devices seem to be able to detect the electrical activity from the heart and tease it out from the electrical activity of the skeletal muscles, and this is how chest straps work (but they have a *much* bigger heart activity signal to work from).

The answer to your Q is that ventricular activity is always what's being detected and reported by external personal devices, whether it's pulseox or electrical activity.  A doctor's 12-lead ECG might be able to report atrial rate separately from ventricular.  The signal from the atria as they depolarise is small compared to the ventricles, so whatever HR data you have it's the ventricles or specifically the LV that's being monitored.  Your two-chamber PM will be able to detect and track both, of course.  And it may well be configured to log unusual or excessively high activations separately - clever bit of kit, hence all the posts on this forum about reports showing thousands of PACs and a few PVCs - or vice versa (not so good).

And your excellent Q highlights the value of a working SA-node - it can do a better job of deciding what your HR should be, and with a properly set up dual-chamber PM, your PM will replicate the atrial activation to the ventricles and bypass the AV-node blockage.

HTH.

Atrial rate

by AgentX86 - 2020-07-12 17:04:01

A 12-lead EKG can obviously distinguish the atrial activity from ventricular.  The P-wave is the atria doing its thing. OK, that's a 1-to-1 correlation but there is the second degree heart blocks where the P-waves aren't always followed by the QRS of the ventricles depolarizing. The atrial rate and ventricular rates then differ.

Then there is Atrial flutter. An EKG can even  tell (usually) which atrium is misbehaving. In flutter, the atrial rate can be two to four times the ventricular rate, 240bpm, sometimes 300bpm.

Apple watches and the Kardia Mobile use the signal between the hands for their single lead EKG. This can't see flutter but you can see the P-wave and any conduction issue to the ventricles. They can't diagnose anything other than Afib but you can clearly see the atrial an ventricular rate differences.

Comments

by SNORTINGDONKEY - 2020-07-13 19:43:20

Thank you @crustyg and @AgentX86 for those answers...great to know this. I did check if the HR reported by my Apple Watch matches what the docs see, and it does match. FWIW, I have been doing an ECG on my watch and it says it's normal sinus rhythm.