Heart failure is regrettably much more complicated than that; you could give yourself a hernia lifting textbooks on the subject...


Alert: Probably more than you wanted to know about digitalis (foxglove)

Digitalis has many different effects on the heart, known by their Greek names:

inotropic - makes the muscle contract more vigorously (faster and stronger); that's the primary benefit

chronotropic - makes the rate faster in spontaneously-active pacemaker-like cells, so that too much makes an excessively fast heart. (But as the heart failure is relieved by the inotropic benefit, the heart doesn't have to work as hard, and then it can slow down a bit. It's only a secondary effect of the digoxin.)

dromotropic - makes the conduction of impulses from atria to ventricles slower, so that if there is Atrial Fibrillation and the ventricles are going too fast, digoxin will slow it. (That's another place where the slowing-down comes into play.)

bathmotropic - makes the individual cells more irritable, so they may give extra beats more frequently. Can be dangerous, or merely annoying but harmless, or not even noticed!

I feel like a real dinosaur now - those Greek names aren't even in the current textbooks of pharmacology any more! Too abstruse for our times, I suppose. The properties of the drug remain unchanged, though

Except for the irritability part, these are generally beneficial for a person with a failing heart. Unfortunately it's very easy to tip over into excess since the difference between "enough" and "too much" is quite small: the drug has a "narrow toxic/therapeutic ratio."

We use other things too for relieving the various symptoms of heart failure: diuretics for fluid retention; "ACE inhibitors" to permit more "circulation-per-squeeze" without using any more energy; "beta-blockers" so the heart isn't running on overdrive continuously. Digoxin has become an "add-on" drug. And of course there is more public awareness of what causes the problem in the first place, as well as more effective medicines, leading to better control of smoking, of blood pressure, of cholesterol, and of diabetes, and therefore to less coronary artery disease to have to treat.

It's interesting that the chief cause of heart disease in Withering's day (rheumatic fever; rheumatic heart disease) is virtually unheard-of today in this country, so that we're largely dealing with a diffferent set of problems.

Getting back to "digitalis," the extract of D. purpurea: it's actually a combination of a lot of related compounds called digitalis glycosides (dozens, I was told) which differ only by minor changes in the structure of the parent compound and the associated sugar part but have great variation in effects. Nowadays the drug has been standardized and synthesized, and isn't obtained from the plant any more. The most common preparation is "digoxin," only recently available as a generic but even the venerable brand Lanoxin (r) is very inexpensive by today's standards.