Sunday, September 16, 2007

Heart Transplant? Pacemaker?

A while ago I asked my cardiologist alternatives to all the medication and the lack of exercise tolerance. We talked briefly about a heart transplant, but this was almost immediately discounted. Firstly to be eligible for a heart transplant I would need to be in advanced heart failure, clearly this is not the case at the moment. If it was (hypothetically) done anyway there could be an improvement in some parts of my quality of life, but I would be trading some known, and well managed, problems for others. As I understand it, transplant patients need to be on anti organ rejection drugs (immunosuppressants), pretty much for the rest of their lives. These can make feel pretty grotty, and susceptible to other infections. So if I were to go into heart failure again, this might be a consideration, but I will try my best to stay healthy and avoid this.

We also discussed the possibility of a pacemaker, my heart rhythm is not normal. This most easily noticed by feeling my pulse, it will be regular for some time and then suddenly speed up for a few beats and then slow down again. If I remember correctly that's not really the problem though. Before I get into the pacemaker story, I'll try explain, again I think, how the heart works, but this time with a little more emphasis on nerve impulses (I'm not a doctor, so I could be getting this all wrong).

The heart has four chambers, two atria and two ventricles. Blood is pulled into the (smaller) atria at the top of the heart and then pumped into the (bigger) ventricles at the bottom of the heart. The ventricles then contract to pump blood all the way around the body. The timing of all these contractions is controlled by a set of nerve pathways around the heart. The heartbeat is generated by a special group of cells, the sinoatrial (SA) node, in the right atrium, this group sends an electrical signal out that contracts the heart muscles, starting with the atria. The signal is passed through nerve pathways down the atrium to the atrioventricular (AV) node, this node passes the signal on to the ventricles. Here comes the clever bit, for the best operation, the atria should be empty before the ventricles contract, so this AV node has a special property. It delays the signal for about 0.1 seconds, this ensures that the atria have contracted and primed the ventricles before they, in turn, beat. 

So what about my heart? Well my atria are beating way too fast, so I guess something went pear-shaped and my SA node is now going ballistic. I have atypical atrial flutter, so according to what I have read my atria could beat at above 340bpm. It is caused by a self sustaining circular neural pathway passing a signal around the heart. My atria are "tired" they don't actually contract anymore (well that is unless they have somehow fixed themselves since my last ECG). Of course a  whole heart beating at that speed would be pretty scary and probably not good for you and would also get "tired", unless you are a humming bird. The AV node fixes this, it only allows a certain number of these beats through every minute. This maximum is where you get your maximum heart rate from (roughly 220 minus your age).  Still my heart beating at 190 bpm all day would still be really uncomfortable, I don't think it ever did actually get to that pace even when I was sick, but I might be wrong. Anyway I have medication (beta blockers) which brings this max down even further, it seems my max heart rate is about 150 bpm. I have no idea why my resting heart rate is about 65.

Anyway, this arrhythmia bothered my cardiologist and we discussed options to fix it. I think I have mentioned my numerous cardioversions and the attempted cardioablation, so I won't say more about those here, except that both treatments failed. So if this rhythm problem becomes dangerous to my health, the only other option is to (if I remember correctly) destroy my AV node (burn it away) and implant a pacemaker which would only stimulate my ventricles. I'm not sure what that will mean for exercise etc, but I assume there is someway for the pacemaker to realise that you need greater cardiac output and speed up the heart rate. So far it's been decided that my heart is still good enough, with my current medication, not to do anything that drastic, so I don't need to worry about running out of battery power just yet, hehehe 


Andy Hadfield said...

You've been SCRUBBED! :)

Check it out...

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