Heart failure Flashcards
what is the differences between systolic and diastolic dysfunction?
systolic dysfunction is related to impaired contractile properties whereas diastolic dysfunction is related to the inability of the ventricle to fill because of decreased volume (due muscle hypertrophy, the walls of the ventricles cant stretch)
what are the consequences of heart failure ?
- in left ventricular failure, left atrial and pulmonary venous pressures and volumes increase. This pulmonary congestion can lead to pulmonary edema and shortness of breath (dyspnea)
- Right ventricular failure, whether alone or as a consequence of left ventricular failure, causes blood volume to increase in the systemic venous circulation leading to elevated venous pressures and systemic edema.
- Reduced perfusion of the kidneys decreases sodium and water excretion, which in turn causes blood volume to increase, which further increases venous pressures (and edema)
what are the compensatory mechanisms in heart failure
- increased blood volume serves as an important compensatory mechanism to increase cardiac preload which helps to maintain stroke volume through the Frank-Starling mechanism (the more you stretch out the ventricle, the stronger the force of contraction to eject blood out)
- Neurohumoral activation is a very important compensatory mechanism because it helps to maintain arterial pressure. Neurohumoral responses include activation of sympathetic adrenergic nerves and the renin-angiotensin-aldosterone system, and increased release of antidiuretic hormone (vasopressin) and atrial natriuretic peptide. The net effect of these neurohumoral responses is to produce arterial vasoconstriction (to help maintain arterial pressure), venous constriction (to increase venous pressure), cardiac stimulation, and increased blood volume.
explain what happens in heart failure with reduced ejection fraction?
heart failure with reduced ejection fraction is when there is systolic dysfunction results from a loss of intrinsic contractility and is generally associated with a dilated ventricle.
in heart failure with reduced ejection fraction, why is increasing preload not useful in increasing stroke volume ?
because in HFrEF, preload is already elevated due to ventricular dilation as a result of ventricular remodeling and increased blood volume. therefore, increasing preload further does not necessarily increase stroke volume (since the spring is already broken).
Furthermore, increasing preload will exacerbate pulmonary or systemic congestion and edema
explain what happens in heart failure with preserved ejection fraction?
This type of ventricular failure is related to impaired ventricular filling caused by hypertrophied (less compliant) ventricles or by impaired ventricular relaxation.
Hypertrophy can result from chronic hypertension or aortic valve stenosis.
Diastolic dysfunction can also occur due to stiffening of the ventricular wall (restrictive cardiomyopathy) caused by fibrosis
These patients will often have normal or near normal ejection fractions, and therefore this type of failure is referred to as heart failure with preserved ejection fraction (HFpEF)
what happens to the end-diastolic pressure and volume in heart failure with preserved ejection fraction vs reduced ejection fraction
Diastolic dysfunction results in large increases in ventricular end-diastolic pressure, which can lead to pulmonary edema. Despite a large end-diastolic pressure, the end-diastolic volume may actually be reduced because of the decreased ventricular compliance.
In systolic dysfunction, ventricular end-diastolic pressure is low due to the fact that the end-diastolic volume is high as a result of dilation
what are the 3 most important drugs classes used in heart failure?
Diuretics
ace inhibitors
beta blockers
explain the rationale for the use of Diuretics in heart failure?
Heart failure leads to activation of the renin-angiotensin-aldosterone system, which causes increased sodium and water retention by the kidneys. This in turn increases blood volume and contributes to the elevated venous pressures associated with heart failure, which can lead to pulmonary and systemic edema. The primary use for diuretics in heart failure is to reduce pulmonary and/or systemic congestion and edema, and associated clinical symptoms (e.g., shortness of breath - dyspnea).
Although diuretics reduce ventricular preload this generally does not significantly reduce stroke volume because the depressed Frank-Starling curve in systolic dysfunction is relatively flat at high preload volumes and pressures.
in patient with HF with preserved ejection fraction, diuretics are given cautiously because removing too much volume can significantly reduce end-diastolic volume and therefore stroke volume in a stiff ventricle
explain the rationale for the use of ACEI in heart failure
ACE inhibitors have proven to be very effective in the treatment of heart failure caused by systolic dysfunction (i.e., heart failure with reduced ejection fraction; HFrEF)). Beneficial effects of ACE inhibition in HFrEF include:
Reduced afterload, which enhances ventricular stroke volume and improves ejection fraction.
Reduced preload, which decreases pulmonary and systemic congestion and edema.
Reduced sympathetic activation, which has been shown to be deleterious in heart failure.
Improving the oxygen supply/demand ratio primarily by decreasing demand through the reductions in afterload and preload.
Prevents angiotensin II from triggering deleterious cardiac remodeling
explain the rationale for the use of beta blockers
by improving ventricular relaxation and reducing heart rate (which permits more time for filling). They also promote regression of cardiac hypertrophy, reduce arterial pressure and improve coronary blood flow
why HF patient with fluid retention cannot start beta blocker
the patient must be stable before they can be started on beta blocker, this means:
they must have no physical evidence of fluid retention hence it would be essential to manage them with a diuretic first if they do have fluid retention
I think beta blocker reduces the force of contraction and heart rate, if there is fluid accumulation, the heart require to pump harder in order to overcome that high pressure in the circulation but the cant wont be able to do that in presence of beta blocker, so cardiac output is significant reduced
Counselling points for HF patients
Advise patient on medicine adherence;
- Patient is less compliant on taking their diuretics bc it makes them go to the toilet quite often, and when they are outside they need to make sure hey know where the nearest toilet
- Keep their dosing regime as simple as possible, and make sure the patient is educated about what to do when they missed a dose
- older patients may need more frequent monitoring for side effects so they also may be less willing to take medication because of the side effects
- Patient self management of symptoms: encourage patient to keep an eye on their daily weight if it’s increasing - it may be a sign that they’re getting fluid retention and they need to up their dose of their diuretic . They should report any weight gain of more than 1.5-2 kg
- they should also report there’s any increase in shortness of breath or fluid accumulation bc it may be signs of worsening of the heart failure and they may need to increase their doses
Advice and care of women who are planning a pregnancy or are pregnant:
Refer women who are planning a pregnancy or are pregnant to the specialist multidisciplinary heart failure team;
ACEi = should be avoided in pregnancy as it can adversely affect fetal blood pressure and renal function, and can even cause skull defects
Beta blockers = should be avoided in pregnancy bc it can cause neonatal hypoglycemia and bradycardia
Patient should be offered to attend an cardiac rehabilitation program - ensure that they are attending the problem and is counselled on the benefits of it - The program is designed to help you improve your health and recover from a heart attack, other forms of heart disease or surgery
