4. Causes and forms of heart failure

Forms of heart failure

There are multiple ways to classify heart failure. They are:

• According to the pathomechanism
  • Systolic dysfunction heart failure
  • Diastolic dysfunction heart failure
• According to affected side
  • Left-sided heart failure
  • Right-sided heart failure
• According to the cardiac output
  • Low-output heart failure
  • High-output heart failure
• According to the timeline
  • Acute heart failure
  • Chronic heart failure

Most heart failures are chronic and low-output, and so when no specific type is specified, assume that we’re talking about that type. Acute heart failure and high-output heart failure have their own topics.

Systolic dysfunction heart failure

Systolic dysfunction HF occurs because of a problem with the systole, as the name suggests, either due to problems with ventricular emptying or ventricular contractility. Both the stroke volume and ejection fraction are reduced, due to a normal EDV but higher ESV.

Etiology:

• Reduced ventricular contractility
  • Myocardial infarction
  • Dilated cardiomyopathy
• Increased afterload
  • Systemic hypertension

Diastolic dysfunction heart failure

Diastolic dysfunction heart failure occurs when the ventricular filling during diastole is reduced. The stroke volume is reduced but ejection fraction is normal. This is possible because both the EDV and ESV are reduced, which reduces the stroke volume but keeps the ejection fraction the same.

Etiology:

• Decreased ventricular compliance
  • Ventricular hypertrophy
    • Long-standing systemic hypertension
  • Restrictive cardiomyopathy
  • Hypertrophic cardiomyopathy
  • Constrictive pericarditis
  • Pericardial tamponade
• Decreased ventricular filling
  • Pulmonary embolism
  • Defective venous return (Decreased blood volume, vena cava thrombosis)

One-sided heart failure

When only one side of the heart is failing we call it either left-sided or right-sided heart failure. However, failure of one side usually eventually causes failure of the other side, meaning that we rarely see a heart where one side is normal and the other is failing. In clinical context we mostly see biventricular heart failure instead of one-sided, however often the problems began in one of the sides.

The causes of the two will be discussed further down. Mainly, the left ventricle is affected by systemic hypertension and ischemia, while the right ventricle is mostly affected by pulmonary pathologies like COPD or pulmonary hypertension.

In left-sided heart failure the ventricle’s inability to pump out blood can cause blood to congest in the pulmonary circulation. This will cause pulmonary hypertension that will lead to right-sided heart failure. Right-sided heart failure causes the right ventricle to become enlarged, which will cause displacement of the septum so that the left ventricle will acquire an abnormal shape. This can disturb filling which will lead to left-sided heart failure.

When right-sided heart failure is caused by pulmonary pathologies we call the condition cor pulmonale.

Causes of heart failure

The biggest causes for heart failure are these:

• Ischaemic heart disease
  • Most commonly caused by coronary artery disease
  • Includes myocardial infarction
• Arterial hypertension
• Diabetes mellitus
• Heart valve defect

The following are risk factors for heart failure:

• Obesity
• Smoking
• COPD
• Haemochromatosis
• Recreational and prescription drug abuse
• Alcohol abuse

The performance of the ventricles is obviously important for the heart to pump enough blood, however there are many things that cause the ventricles to fill, contract or empty insufficiently. Their causes are different for the left and right ventricles. Usually we see a combination of these factors.

The most important are:

1. Decreased ventricular filling
2. Decrease in ventricular contractility
3. Decrease in ventricular emptying because of increased afterload.
4. Any combination of the above

Causes for decreased ventricular filling in the right ventricle:

• Pericardial tamponade
• Stenosis of tricuspid valve
• High intrathoracic or intrapleural pressure (like in pneumothorax)
• Insufficiency of right atrium contraction
• Stiff ventricular wall
• Defective venous return (ivc thrombosis, ivc compression, reduced blood volume etc)

Causes for decreased ventricular filling in the left ventricle:

• Pulmonary embolism
• Mitral stenosis or insufficiency
• Left ventricular hypertrophy
• Stiff ventricular wall
• Pericardial tamponade
• Constrictive pericarditis
• Restrictive cardiomyopathies

Causes for decreased ventricular contractility in both ventricles:

• Infarct
• Fibrosis
• Degradation caused by hypertrophy
• Congestive cardiomyopathies

Necrotic myocardium doesn’t contract at all, and nearby areas will by hypokinetic or akinetic as well.

Causes for decreased right ventricular emptying include:

• Pulmonary stenosis
• Pulmonary hypertension
• Tricuspid valve insufficiency

Causes for decreased left ventricular emptying include:

• Systemic hypertension
• Stenosis of large arteries
• Aortic valve stenosis
• Polycythaemia