S2: Heart Failure

Question 1

What is Heart Failure?

Answer 1

It is a clinical syndrome (collection of sign and symptoms) caused by inability of the heart to supply sufficient blood flow to meet the body’s need

Question 2

List mechanical causes of pump failure

Answer 2

• Impaired ventricular function
• Pressure overload of ventricle
• Inflow obstruction of ventricle
• Valvular disease
• Volume overload of ventricle

Question 3

What diseases cause impaired ventricular function?

Answer 3

• Myocardial infarction

- Cardiomyopathy

Question 4

What diseases cause impaired pressure overload of ventricle?

Answer 4

• Systemic hypertension

- Pulmonary hypertension

Question 5

What diseases cause inflow obstruction of ventricle?

Answer 5

• Restrictive cardiomyopathy (heart is small and cannot stretch to allow blood in)
• Diastolic heart failure
• Mitral stenosis

Question 6

What diseases cause Valvular disease?

Answer 6

• Aortic stenosis/regurgitation
• Mitral stenosis/regurgitation
• Tricuspid stenosis/regurgitation

Question 7

What diseases cause Volume overload of ventricle?

Answer 7

• Ventricular and Atrial septal defect (VSD and ASD) –> too much blood on one side of the heart
• Patent ductus arteriosus (PDA)

Question 8

What are the 3 ways Heart Failure can be classified?

Answer 8

1. Reduced ejection fraction, preserved ejection fraction or midrange ejection fraction
2. Acute or Chronic
3. Left ventricular failure vs Right ventricular failure

Question 9

Describe class I and class IV of the NYHA Functional Class for heart failure

Answer 9

Class I : No limitations even with physical activity

Class IV: Inability to carry out any physical activity without discomfort. Symptoms also during rest - this is severe heart failure.

Question 10

Why is heart failure increasing?

Answer 10

• HF is very strongly related to age and we live in an aging population in the UK.
• The other major factor for increasing prevalence of HF is better treatment for HF so it is no longer a fatal condition but a long term condition so patients with HF will live longer.

Question 11

What are the compensatory mechanisms of a weakened heart?

Answer 11

1. Ventricular dilation - natural (to maintain SV at reduced ejection fraction because there is a larger volume to start with)
2. Increased myocardial contractility (sympathetic drive increases in surviving parts of the heart)
3. Myocardial hypertrophy
   - cardiac failure –> sustained increase in chamber radius (dilation)
   - Laplace’s law ( radius decreases increases CO)
4. Renin-Angiotensin-Aldosterone System (RAAS) - increasing BV and therefore pressure for a short term solution
5. Sympathetic Stimulation

Question 12

Describe Deleterious effects of prolonged compensatory mechanism

Answer 12

1. Continuous sympathetic activation:β-adrenergic downregulation and desensitization ‘immune’ (less inotropic response)
2. Increased heart rate:Increased metabolic demands which will increase myocardial cell death
3. Increased preload:Beyond limits of Starling’s law (ventricular dilation), pressure is transmitted to pulmonary vasculature leading to pulmonary oedema
4. Increased total peripheral resistance:Higher afterload leading to decreased stroke volume and cardiac output
5. Continuous neurohumoral activation:Chronically elevated angiotensin-II and aldosterone trigger production of cytokines, which stimulate macrophages and stimulate fibroblasts resulting in myocardial remodelling which leads to loss of contractility.

Question 13

Describe the frank-starlings curve

Answer 13

• In health, increased filling of the ventricle (heart will dilate) results in increased force of contraction. SV increases as LVEDV increases
• In heart failure this mechanism fails, as the ventricle is over-stretched reducing ability to cross-link actin and myosin filaments (weaken).

Question 14

Describe ventricle dilation as a compensatory mechanism for HF

Answer 14

• CO = SV x HR
• The ventricle dilates to maintain SV
• When this compensatory mechanism is exhausted, the pressure in the stretched ventricle steadily increases resulting in restriction to filling (back pressure into LA - pulmonary oedema) and increased venous pressures
• Preload can be reduced by vasodilators (GTN) and diuretics

Question 15

What are the two main drugs prescribe for heart failure?

Answer 15

Beta blockers which block sympathetic NS and reduce HR and contractility

Ace inhibitors which block the activation of RAAS which decreases afterload, preload and Na+ and H2O retention.

Question 16

What does angiotensin II cause?

Answer 16

• Vasoconstriction
• Stimulation of thirst at hypothalamus
• Increased aldosterone secretion increases water retention via sodium reabsorption

Question 17

What is congestive heart failure?

Answer 17

Left and secondary RV failure - most people have this compared to just L or R failure - isolated HF.

It is when left heart failure also causes right heart failure.

Question 18

Describe right ventricular failure

Answer 18

Right ventricular failure where right ventricle is weak, this will cause increased back pressure in the RA which feed into the venous system which drain into the right side of the heart (superior and inferior vena cava). When this blood is congested and at high BP (increase JVP), oedema in the legs will occur and start at the ankle and work its way up. Right pleural effusion will occur before left. Ascites which is the accumulation of protein containing ascitic fluid in the abdomen can occur. – > fluid congestion seen

Question 19

Describe left ventricular failure

Answer 19

Left ventricular pressure causes increased pressure in LA so there is backflow into the pulmonary veins which are draining the lungs which causes pulmonary oedema (pooling of fluid within the alveoli). The volume of blood needed to develop pulmonary oedema is very little and it has a severe effect compared to RV failure where usually the patient has a larger volume of fluid in their oedema.

Question 20

Is RV failure or LV failure worse?

Answer 20

The most life threatening is LV failure

Question 21

Causes of right hear failure

Answer 21

1. Left heart failure (in congestive heart failure)
2. Pulmonary artery hypertension (e.g. in lung disease, COPD, pulmonary embolism)
3. Arrhytmogenic right ventricular cardiomyopathy (rare)
4. Tricuspid valve disease (AF) - (rare)

Question 22

Symptoms and signs of left ventricular failure

Answer 22

Symptoms:

• Dyspnoea (shortness of breath SOB)
• Orthopnoea (SOB lying flat - if able to lie flat it is a sign that its the heart not the lungs)
• Paroxysmal nocturnal dyspnoea (Sudden SOB at night)

Signs:
- Pulmonary Oedema

Question 23

Describe the biomarker:NTproBNP for HF

Answer 23

• Extremely sensitive test for HF and will not miss any cases
• Cheap
• Not specific and is often mildly raised in other conditions (AF, hypertension, chest infections)
• If elevated and heart failure is suspected an echocardiogram must be carried out
• Useful for follow up not just diagnosis

Question 24

What is done if BNP test is normal?

Answer 24

We look for other causes of breathlessness

Question 25

What is biventricular pacing?

Answer 25

• Progressive
• Many have left bundle branch block where wiring to the left side of the heart is blocked resulting in late contraction of distal LV compared to RV - discoordinated contraction which enhances the hemodynamic consequences of LV systolic dysfunction
• LV based pacing may reverse this leading to haemodynamic and clinical benefit

Question 26

Treatment for HF patient

Answer 26

• Cardiac resynchronisation therapy
• Heart transplant
• Left ventricular assist devices (mechanical pumps)
• Palliative care
• Biventricular pacing