Cardiovascular pathology (3)

Question 1

What is characteristic of right heart failure and what is congestive heart failure?

Answer 1

• much less common than left heart failure
• by convention, term RHF is usually reserved for cases developing in absence of left-sided heart failure
• ie. we don’t use the term ‘right heart failure’ when the right heart failure is secondary to left heart failure

Overall, the most common cause of RHF is as a consequence of LHF, when it is called congestive heart failure (or biventricular heart failure)

Question 2

Acute right heart failure is much less common than acute left heart failure. What is the most common cause of acute right heart failure?

Answer 2

• massive pulmonary embolism
• causing sudden blockage of major pulmonary artery or the pulmonary bifurcation (saddle embolus)
• pressure in pulmonary arterial system rises dramatically
• ie development of pulmonary hypertension
• the right heart does not have enough time to undergo compensatory changes
• so cannot generate enough force to maintain CO
• results in acute right heart failure
• presents clinically as circulatory collapse, shock and/or instantaneous death

An MI involving right ventricle but sparing the left ventricle is another important (but less common) cause of acute right heart failure

Question 3

What is pulmonary hypertension?

Answer 3

• pulmonary hypertension refers to inc in BP in pulm vasculature (pulmonary arteries, veins, capillaries)
• it is defined as resting mean pulmonary artery pressure at or above 25 mmHg
• normal is in range of 18-25mmHg

Question 4

Chronic right heart failure again is much less common than chronic left heart failure.

What are the clinical features of chronic right heart failure?

Answer 4

• elevated JVP
• hepatomegaly
• ascites
• peripheral oedema

Question 5

Preceding the development of chronic heart failure, the right ventricle is damaged slowly over a period of time.

What are causes of slow damage to the right ventricle?

Answer 5

• lung diseases!
  
  • COPD
  • pulm fibrosis (diffuse parenchymal lung diseases)
  • recurrent small pulmonary emboli

These lung diseases damage the RV by causing pulmonary hypertension

Question 6

What changes does the slow damage in chronic RHF allow for within the myocardium?

Answer 6

• enough time for compensatory right ventricular hypertrophy
• allows it to effectively ‘push harder’ against increased pressure in pulmonary circulation
• RV hypertrophy maintains cardiac output in face of increased pressure in the pulmonary circulation

eventually the myocardium becomes irreversibly damaged + the RV decompensates, resulting in chamber dilatation and the onset of progressive right heart failure

Question 7

What is cor pulmonale?

Answer 7

• term used to indicate right heart failure due to lung disease (incl diseases of the pulm vessels):
  
  • massive PE -> acute cor pulmonale
  • COPD, pulm fibrosis or recurrent small PEs -> chronic cor pulmonale

The link between lung disease and development of right heart failure is that the lung disease causes pulmonary hypertension (ie increased pressure in the pulm circulation)

Question 8

What is the commonest cause of cor pulmonale?

Answer 8

COPD

Question 9

PEs are often classified as non-massive and massive.

Describe features of a non-massive PE

Answer 9

• due to a medium-sized embolus
• occluding a segmental pulmonary artery
• results in a segment of lung being ventilated but not perfused
• AKA ventilation/perfusion defect
• consequently -> respiratory compromise
• manifests are pulmonary infarction +/- pleuritis and effusion
• clinically: pleuritic CP + dyspnoea, maybe haemoptysis due to infarction of non-perfused lung tissue, maybe pleural rub, crackles + effusion

Question 10

What are features of a massive PE?

Answer 10

• due to massive embolus occluding proximal pulm artery or the pulmonary artery bifurcation (‘saddle embolus’)
• -> blood cannot enter lungs
• -> sudden inc in resistance to pulmonary BF
• -> sudden pulmonary hypertension
• right side of heart doesn’t have time to compensate
• -> onset of acute right heart failure (cor pulmonale)
• also, blood cannot pass through lungs -> decreased filling of left side of heart + therefore decreased left ventricular output
• presents as haemodynamic compromise in form of shock, collapse + sudden death
• O/E -> tachycardia, hypotension, raised JVP, RV heave, normal chest examination, low O₂ sats

Question 11

The third presentation of pulmonary embolsim is in the form of recurrent small PEs.

What are recurrent small PEs?

Answer 11

• each individual episode is usually subclinical (ie does not result in symptoms)
• but over time, the multiple small emboli occlude arterioles
• resulting in gradual occlusion of pulmonary arterial bed
• leading to gradual development of pulmonary hypertension
• bc onset is gradual, heart has time to undergo compensatory RVH
• eventually RV will decompensate + RHF (cor pulmonale) ensues

Question 12

What are the most common causes of cor pulmonale?

Answer 12

Question 13

In summary, what are the most common causes of left and right heart failure?

Answer 13