Chapter 12: Heart Disease: Overview of Pathophysiology

Question 1

Although many diseases can involve the heart and blood vessels, [8,] [9] cardiovascular
dysfunction results from one or more of six principal mechanisms, most with detectable
morphologic manifestations:

Answer 1

• Failure of the pump
• Obstruction to flow
• Regurgitant flow
• Shunted flow
• Disorders of cardiac conduction
• Rupture of the heart or a major vessel

Question 2

What happens when there is Failure of the pump?

Answer 2

Failure of the pump.

In the most common circumstance, the cardiac muscle contracts weakly, and the chambers cannot empty properly.

In some conditions, the muscle cannot
relax sufficiently to permit ventricular filling.

Question 3

What happens when there is Obstruction to flow?

Answer 3

Obstruction to flow.

Lesions can obstruct blood flow through a vessel (e.g.,
atherosclerotic plaque) or prevent valve opening or otherwise cause increased
ventricular chamber pressure (e.g., aortic valvular stenosis, systemic hypertension, or
aortic coarctation).

In the case of a valvular blockage, the increased pressure overworks
the chamber that pumps against the obstruction.

Question 4

What happens when there is Regurgitant flow ?

Answer 4

Regurgitant flow. In this situation, at least part of the output from each contraction flows
backward, adding a volume workload to each of the chambers (e.g., left ventricle in
aortic regurgitation; left atrium and left ventricle in mitral regurgitation).

Question 5

What happens when there is Shunted flow?

Answer 5

Shunted flow .

Blood can be diverted from one part of the heart to another (e.g., from the left ventricle to the right ventricle), through defects that may be congenital or
acquired (such as following myocardial infarction).

Shunted flow can also occur between
blood vessels, as in patent ductus arteriosus

Question 6

What happens when there is cardiac conduction disorder?

Answer 6

Disorders of cardiac conduction .

Conduction defects or arrhythmias due to
uncoordinated generation of impulses (e.g., atrial or ventricular fibrillation) lead to nonuniform and inefficient contractions of the muscular walls.

Question 7

What happens when there is Rupture of the heart or a major vessel?

Answer 7

Rupture of the heart or a major vessel

In such circumstances (e.g., a gunshot wound
through the thoracic aorta), there is massive bleeding into body cavities or externally.

Question 8

Most cardiovascular disease results from a complex interplay of genetics and environmental
factors that disrupt networks of genes and signaling pathways that control morphogenesis,
myocyte survival and response to injury, biomechanical stress responses, contractility, or
electrical conduction. [10]

For example, the pathogenesis of many congenital heart defects involves an underlying genetic abnormality whose expression is modified by environmental or maternal factors (see later).

Moreover, genes that control the development of the heart mayalso regulate the response of the heart to aging or to various types of injuries and stresses.

As
we will discuss, certain types of adult-onset heart disease have a predominantly genetic basis,
and it is suspected that genetic polymorphisms in the same genes (or other genes in the same
pathways) are likely to modify the risk of many forms of heart disease.

These genetic
discoveries are providing new insights into the molecular causes of heart disease and are likely
to increasingly become part of its diagnosis and classification.