@VitalsignsMOOC first week thoughts cardiac stuff

This is proven to be an interesting class so far. Initially I thought it might prove too simplistic and certainly the gaps between clinical practice, medicine, academia, and engineering are huge, but its cool seeing things from another sectors point of view.

A few thoughts:

Plastic heart models are pretty sucky… but then again everything is a compromise when it comes to models, and even more so plastic ones. 🙂 Had I not had experience with pacers, the models would seemingly create a ton of disconnects… but cadaver lab on day 1 would likely be too intimidating, so I guess plastics models are a reasonable compromise. Alas, we do have youtube, and spending an hour viewing an open heart surgery reinforced a ton of material.

Human Heart from wikipedia

Wiggers diagrams are incredibly helpful to understand the the cardiac cycle. Alas, there is a lot of information where in google is less than helpful. This is probably due to my rabbit trailing outside the scope of the course…

Things like the dicrotic notch and wave explanations are crazy from an engineering point of view. If measured right at the aorta, one would have the expansion of the aorta as well as the impulse response of the aortic valve and reflected waves returning from other structures.. short of something being highly tuned, my gut feel is some level of ringing would occur in this. On the other hand, if the aorta pressure is measured further away from the heart itself, one would also have reflected fluid momentum playing havoc with the measurement. Is this damped by the elastic nature of the aorta? Are there chemical processes dicking around with the aorta’s modulus of elasticity? What about the degradation of the aorta and valves over time? Alas, these are questions outside the scope of the course.

Heart sounds are tricky and the teaching of them apparently more so. We heard one example, and even after cycling through it a few times, it was still a bugger to pick up the difference.  Alas, youtube was friendly in this case.

This video covers locations in a cool way… marked up tshirts 🙂

This doctor is incredibly entertaining and he takes complex material and makes it simple, in this case location as well as sounds.

We still have the issue with what on earth are these things supposed to sound like? Alas, a helpful person in the forums shared the following link which presents mp3’s of a number of problems.


ECG’s were briefly touched upon with one bit being that a 12 lead ECG only uses 10 electrodes. In electronics we have conventional current and electron flow… which causes no small amount of confusion as they are reversed.

In medicine it seems everywhere you turn there are legacy terms and some insane need for backwards compatibility that creates endless amounts of circle chasing. Do we really need 3 names for the left atrioventricular valve (bicuspid, mitral). Do we really need to use the term leads when its really a mapping of the electric fields in different planes of reference? And whats with the chart recorder legacy stuff? Such is why I’m not in medicine LOL

A fellow student provided a link to a cool ECG trainer / simulator…

AV Node delay timing in response to exercise is crazy stuff… I remember some of this from pacer discussions, but just as there was ambiguity back then, it appears its still quite vague today. (Tone plays a role such that sometimes it need to roll forwards in othertimes reverse. Granted, this is outside the scope of the course… but seeing the AV node time mention as 0.1 sec brought back memories. Iirc, it was just a tad over that figure, but there are many ways to look at it… AV free running rate is tweaked 20% if memory serves.

Evaluation A multiple choice test was used for purposes of evaluation. The questions were reasonably easy, but did require some level of thought rather than just the parroting back of information. The ultimate test of my knowledge will be if I can draw and annotate a human heart, draw and explain a Wiggons diagram, identify heart sounds, and interpret ECG traces in May 2015. I can do none of the above to 100% correct standards currently, as such requires more practice then a few hours of videos and studies will provide for… but such will be my means of review of the course material to prevent forgetting it.

All in all an interesting class this week. Next week is on blood pressure. I wonder if we will learn the history of the old wives tale of salt bringing about high blood pressure. Its an interesting myth with a tad of truth mixed in just enough to create lots of confusion.

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