Category Archives: Science

Science

Stages of Heart Failure

As I read academic articles, I mark things that I don’t know or haven’t heard of as a reminder to look them up.

One thing that’s been popping up in paper after paper about heart resynchronization therapy is the New York Heart Association (NYHA) heart failure classification system. The Heart Failure Soceity of America (HFSA?) has a summary of the classes with their symptoms on this page.

I’m already learning about the ways in which patients are evaluated for treatment based on their NYHA classification, and finding out that some of the “best practices” employed by physicians are being revealed as incorrect.

Once I get through the first round of papers and patents (yes, patents), it’s time to dig into the references. I have about 5 more initial papers and maybe 8 patents to read, and then I start pulling more. Overlaps notwithstanding this can be a very deep and wide search. Imagine if I start with five papers, and each has five interesting references. Then I’m up to 30 papers. You might guess that the next generation would bring the total to around 180 papers, but by the time you get back three generations things usually start to narrow again. I’m guessing I’ll probably have to consider around 30-50 papers for the purpose of this exam.

What about leads?

Part of my exam asks about leads. This has brought something to my attention: I don’t really know much about ICD leads. I’ve seen them, held them, I know that they have different numbers of electrodes and different ways of staying put, and I’ve seen them implanted, but now I’m going to have to learn a lot more about their functions, constructions, and applications.

Qualifier Phase 1: Online Research

I’m guessing if I turned in an open-book qualifier response based entirely on about.com and wikipedia I’d probably fail, but I think these sorts of sites have an important role in the research: somewhere to start from. I’m using Freemind to organize what I find.

I’ve begun by searching wikipedia (found nothing) and then moved rapidly straight to Google, where I found a few appropriate results:

What is Cardiac Resynchronization Therapy? | Medtronic Cardiology

Cardiac resynchronization therapy (CRT) is a proven treatment for selected patients with heart failure-induced conduction disturbances and ventricular dyssynchrony. When used in combination with stable, optimal medical therapy, CRT is designed to reduce symptoms and improve cardiac function by restoring the mechanical sequence of ventricular activation and contraction.

Medtronic’s very brief and heavily product-focused page nevertheless has a neat animation of a failing heart before and after resynchronization therapy. Dr. Richard Fogoros gets a little more in-depth on About.com:

Cardiac resynchronization therapy – CRT

CRT uses uses a specialized pacemaker to re-coordinate the action of the right and left ventricles in patients with heart failure.
…
In approximately 30% of patients with heart failure, an abnormality in the heart’s electrical conducting system (called an “intraventricular conduction delay” or bundle branch block) causes the two ventricles to beat in an asynchronous fashion. That is, instead of beating simultaneously, the two ventricles beat slightly out of phase. This asynchrony greatly reduces the efficiency of the ventricles in patients with heart failure, whose hearts are already damaged.

CRT re-coordinates the beating of the two ventricles by pacing both ventricles simultaneously. This differs from typical pacemakers, which pace only the right ventricle.

I was looking for information on clinical indications for administration of CRT. Apparently the roots of the problem are in bundle branch block. I’d say I’m off to a pretty good start!

My Qualifying Exam

Today begins the open-book portion of my qualifying exam, which I think makes me a Ph.D. Student as opposed to a Graduate Student if I pass.

My topic of research, for which I have one week, is Cardiac Resynchronization Therapy. I think I’ll post some of my findings here as I go. That way, I’ll have a record of my research, and any of you who might be interested in the subject can get up to speed along with me.

On my mark, get set, go.

Electron Band Structure in Germanium… a lie?

Someone tells it like it is, or at least pretends to… the 100%-real data is nice (read the whole article, it’s not all in the quote below)Kovar/Hall;

Electrons in germanium are confined to well-defined energy bands that are separated by “forbidden regions” of zero charge-carrier density. You can read about it yourself if you want to, although I don’t recommend it. You’ll have to wade through an obtuse, convoluted discussion about considering an arbitrary number of non-coupled harmonic-oscillator potentials and taking limits and so on. The upshot is that if you heat up a sample of germanium, electrons will jump from a non-conductive energy band to a conductive one, thereby creating a measurable change in resistivity. This relation between temperature and resistivity can be shown to be exponential in certain temperature regimes by waving your hands and chanting “to first order”.