by CNA764

Hi everyone, i just started nursing school and have some silly questions on the treatment modalities of CHF. How does Beta-blockers work? Yeah, seriously (i'm a newbie). I know when beta-1 receptors are blocked, it not only has negative chronotropic and dromotropic effects on the heart, but also has a negative inotropic result. In a patient with systolic heart failure (heart rate < 100), wouldn't the negative inotropic effect further reduce the ejection fraction, thereby reducing cardiac output? Or does the negative chronotropic effect (due to increased time of ventricular filling) balance out this effect on the cardiac output?

I know coreg is proven to reduce mortality in CHF patients, but how? Is it because it reduces oxygen demand of the heart? And my last question (I promise): why are some CHF patients on digoxin (+ inotropic) while others are on beta-blockers (- inotropic)?

i'm a little bit confused, any insight would help!

Re: beta-blocker question

Originally Posted by CNA764

Hi everyone, i just started nursing school and have some silly questions on the treatment modalities of CHF. How does Beta-blockers work? Yeah, seriously (i'm a newbie). I know when beta-1 receptors are blocked, it not only has negative chronotropic and dromotropic effects on the heart, but also has a negative inotropic result. In a patient with systolic heart failure (heart rate < 100), wouldn't the negative inotropic effect further reduce the ejection fraction, thereby reducing cardiac output? Or does the negative chronotropic effect (due to increased time of ventricular filling) balance out this effect on the cardiac output?

I know coreg is proven to reduce mortality in CHF patients, but how? Is it because it reduces oxygen demand of the heart? And my last question (I promise): why are some CHF patients on digoxin (+ inotropic) while others are on beta-blockers (- inotropic)?

i'm a little bit confused, any insight would help!

Good Question!

OK my quick answer is:

Used to be everyone with a Dx of CHF got Dig. Not true anymore. Treatment of CHF with dig (these days) is individualized. This is mostly because there is evidence that dig has no long-term effect on mortality...BUT is useful in certain patients (mostly with Systolic heart-failure...patients with diastolic heart-failure arent afforded any benefit from dig) Probably best to look at the individual patient...do they have a Hx of a-fib/atrial-tachy-rhythm problems, systolic-vs-diastolic CHF, etc.?

And, you ask good questions about beta-blockers and their potential effect on reducing cardiac output...and the old-school cardiology thought was just that. They weren't prescribed for everyone with CHF but rather reserved for HTN, tachy-arrhythmias, etc.. BUT.. now, there is a wealth of evidence that beta-blockers do reduce mortality/morbidity in CHF (as you mentioned) and can help slow it's progression. This mechanism is mostly a matter of reducing/delaying myocardial remodeling, reducing myocardial O2 demand, etc.

So...your next assignment is to learn the difference between systolic and diastolic heart failure...

Re: beta-blocker question

Beta blockers also act on B1 receptors in kidneys, which reduces renin release and avoids some of the cardio-renal syndrome - which is also be a contributor to CHF morbidity/mortality (vasoconstriction leads to increased afterload, more oxygen demand etc etc).

Agree re systolic -v- diastolic HF etiologies and choice of drugs. For example, HCM, the cardiac muscle is large and stiff and cannot fill - beta blockers reduce HR to permit more diastolic filling time, which in turn permits better stretch on the ventricle and better output (Frank-Starling's Law)