Lec 16- Cardiac failure Flashcards
What is HF
- HF is an inability of the heart to deliver blood and therefore O2 at a rate commensurate with the requirements of the metabolising tissue dispute normal or increased cardiac filling pressures
- May be chronic or acute
Why might HF occur
- myocardial
- valvular
- pericardial
- endocardial
- electrical problems
- Or a combo of these
How common is HF
- Incidence 1 new case/1000 people/ year (increases to 10/1000/1 in >85)
- Prevalence ranges from 3-20 cases/1000 (increases to 80/1000 in >75)
- Male to remale ratio 2:1
- Median age is 76
- Average GP will see 20 people a year with HF (4 will be admitted to hospital and 2 will die in next 4 years)
- HF accounts for more than 4% of all medical admission and more than 1% of NHS budget
- Prevalence of HF is increasing because of improved treatment of CHD and ageing population
Risk factor
- Age
- Some viral infections
- Congenital heart defects
- Medical conditions; CHD;MI;HTN; sleep apnoea; valvular hearth disease
- Some medical conditions: rosiglitazone; pioglitazone; NSAIDS some HTN and chemotherapy
- Obesity
- Smoking
- Alcohol
Pre-load
- Pre-load measures the pressure that drives the blood into the left ventricle, prior to contraction
- It depends on the venous pressure and the rate of venous return
- Pre-load is a measure of how much blood returns to the heart to pump
- Excessive preload damages the heart muscle
Afterload
- After-load measures the pressure that the heart must overcome to pump blood out into the circulation
- i.e. to open the aortic and pulmonary artery valves
- It is largely dependant on aortic pressure
- The higher the after-load, the less blood the heart can pump
Cardiac function curve
- How well can the heart pump blood out through the body
- Right atrial pressure (Pr measures blood returning to the heart
- (to the left is enhanced; to the middle is normal; to the right is depressed)
- These curves show the effects of increasing Pra (pressure Right Atria) on cardiac output (cardiac function)
- CO can be enhanced by increasing HR and inotropy or by decreasing after load
What happens in HF
- Cardiac and systemic vascular curves combined. Point A is normal
- Changes in cardiac output (CO) and Pra in response to cardiac failure and compensatory increases in blood volume (vol) and SVR and decreased venous compliance (Cv)
- A normal operating point; B, decreased cardiac performance; C, compensatory increase in SVR coupled with increased Vol and reduced Cv
- The process of increasing CO damages the heart by expanding it, therefore CO will decrease, this acts in a vicious cycle
Cardiac remodelling
- Increased number of myocytes in response to strain
- Initially some improvement in contraction
- As mass continues to increase, ventricle wall thickness increases, the heart changes shape and become less able to contract. Diastolic filling impaired
- Reduced by inhibitors of angiotensin and aldosterone
- An elarged heart may be seen on X-ray
Cardiac remodelling
- Increased number of myocytes in response to strain
- Initially some improvement in contraction
- As mass continues to increase, ventricle wall thickness increases, the heart changes shape and become less able to contract. Diastolic filling impaired
- Reduced by inhibitors of angiotensin and aldosterone
- An elarged heart may be seen on X-ray
HF, progressive worsening
-Poor ventricular function –>
-HF —>
-Decreased stroke volume and cardiac output –>
-Neurohormonal response –>
-Activation of sympathetic system and or RAAS –>
-Vasoconstriction: increase sympathetic tone; Angiotensin II; impaired NO release
Na and fluid retention: increased vasopressin and aldosterone –>
-Further stress on ventricular wall and dilation (remodelling) leading to worsening of ventricular function –>
-Further HF
Actions of angiotensin
-Angiotensinogen -renin–>
Angiotensin I -converting enzyme—>
Angiotensin II –> aldersterone —> increased preload (via increased water and sodium retention)
OR (from angiotensin II) –>increased after load by causing vascular smooth muscle contraction (this action is direct from myocytes or indirect via stimulation of sympathetic nervous system)
Cardiovascular reserve
- Degree to which CVS can increase performance in the face of increased circulatory demand and or increased after load or decreased contractility
- Max CO- resting CO = cardiac reserve
- Decreased exercise tolerance measures decreased cardiac reserve
HF syndrome symptoms
-HF is a syndrome, not a diagnosis or a disease
Cardiac dysfunction leads to clinical syndrome
-Breathlessness and fatigue
-Cough and inability to sleep flat (Fluid accumulation in lungs)
-Fluid retention (peripheral oedema and elevated JVP)
-Reduced ejection fraction (EF) on echocardiogram
clinical features
- The underlying diagnosis and aetiology must always be sought in patients presenting with HF syndrome
- This is the only way in which optimum treatment can be provided e.g. surgery; ACEI for LVSD
- It is also the reason why HF should not be recorded as the primary cause of death on a death certificate
Forms of HF
- Acute
- Chronic divided into: left ventricular systolic dysfunction (LVSD) (50% of cases)
- HF with preserved left ventricular ejection fraction (HFPEF)- myocardium is ok but something is wrong with ventricles
- Others (valve disease, arrhythmias)
Acute HF
- Often precipitated by MI
- Signs include: confusion
- severe breathlessness
- Frothy pink sputum
- Cold clammy skin
- Tachycardia
- Low BP
- Lung crepitations
- Raised JVP
- Third heart sound
Acute HF: basic measures and initial drug treatment
BASIC MEASURES
-Sit patient upright
-Remove any implicated medications
-High flow O2 to correct hypoxia
INITIAL DRUG TREATMENT
-IV loop diuretic to remove fluid
-Nitrates only if there is ischaemia, severe HTN or valvular disease
IF HEART CANT MAINTAIN PERFUSION
-Dobutamine to increase contractility
-dopamine to increase contractility and renal perfusion
-Phosphodiesterase inhibitor to increase CO
Specific treatments for causes of HF
Treat underlying conditions that may be implicated -Anaemia -Thyroid disorders -Arrhythmias Surgical corrections available: -Valve repair and replacements -Implanting pacemaker or defibrillator -structural congenital problems -Biomechanical pump (LVAD) operation -Heart transplant
Chronic HF
- Making accurate diagnosis of HF and determining its cause can be difficult: often symptoms are non-specific; people may have not symptoms of HF; clinical diagnosis is confirmed to be accurate in approx 1/2 all cases when echocardiogram is used
- The likelihood of HF in the presence of suggestive symptoms and signs is increased is there is history of MI or angina, abnormal ECG or CXR showing pulmonary congestion
