Pathophysiology of Heart Failure

Question 1

Systolic ventricular dysfunction

Answer 1

• heart fills to same volume
• impaired contractility
• decreased ejection fraction to less than 40%

Question 2

Diastolic ventricular dysfunction

Answer 2

• impaired diastolic relaxation
• decreased ventricular filling
• decrease in SV and CO

Question 3

What factors can result in systolic dysfunction?

Answer 3

• increased contractility (IHD, cardiomyopathy)
• volume overload (valvular incompetence)
• pressure overload (valvular stenosis/hypertension)

Question 4

What factors can result in diastolic dysfunction?

Answer 4

• impedance of ventricular expansion (constrictive pericarditis)
• increased wall thickness (hypertrophy)
• delayed diastolic relaxation (aging/ischaemia)
• increased HR

Question 5

Effect of right heart failure

Answer 5

• congestion of peripheral tissues can result in:
• oedema and ascites
• liver congestion impairing function
• GI tract congestion causing anorexia/GI distress/weight loss

Question 6

Effect of left heart failure

Answer 6

• decreased cardiac output which can cause:
• activity intolerance/decreased tissue perfusion
• cyanosis/signs of hypoxia

and

• pulmonary congestion which can cause:
• orthopnea
• cough with frothy sputum
• paroxysmal nocturnal dyspnea

Question 7

What can cause right ventricular dysfunction?

Answer 7

• conditions impeding flow into lungs:
• pulmonary hypertension
• valve damage
• pumping ability of right ventricle:
• cardiomyopathy
• infarction
• left ventricular failure
• congenital heart defects

Question 8

What can cause left ventricular dysfunction?

Answer 8

• hypertension
• acute MI
• aortic/mitral valve stenosis/incompetence
• increase in pulmonary pressure

Question 9

What is the disadvantage of compensatory mechanisms?

Answer 9

They help maintain cardiac output in the early stages of heart failure but later on contribute to the worsening of the condition

Question 10

What are the compensatory mechanisms of heart failure?

Answer 10

• Frank-Starling mechnism
• RAAS
• sympathetic activity

Question 11

Problem with Frank-Starling compensatory mechanism

Answer 11

• decrease in ventricular emptying
• increase in vascular volume leads to increase in EDV
• increases muscle stretch and O2 consumption
• heart cannot meet demands
• increase in arterial pressure

Question 12

Problem with sympathetic activity compensatory mechanism

Answer 12

• tachycardia and vasoconstriction
• decreases perfusion of tissues
• causes cardiac arrythmias and renin release
• increases workload of the heart which can cause ischaemia/damage to myocytes/decreased contractility
• desensitisation of B-receptors
• increase in arterial pressure

Question 13

Problem with Renin-angiotensin compensatory mechanism

Answer 13

• decrease in renal blood flow triggers release of renin
• increases angiotensin II formation
• results in vasoconstriction and aldosterone release
• Na+ and water reabsorption increases due to decreased flow to kidneys and aldosterone
• angiotensin II and aldosterone also causes fibroblast and collagen deposition in ventricles
• increases stiffness and decreases contractility of the heart

Question 14

What needs to be targeted for treatment options of heart failure?

Answer 14

• increase cardiac contractility
• decrease preload/afterload to decrease cardiac work demand (by relaxing vascular smooth muscle/decreasing blood volume)
• inhibit RAAS
• prevent inappropriate increase in HR