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Common Congenital Heart Lesions - page 83 / 126





83 / 126

83 of 126

Pathophysiology of Heart Failure

Divided into systolic and diastolic dysfunction.

Systolic Dysfunction: heart failure that results from an abnormality of ventricular emptying. Results in decreased ability of ventricle to eject blood

  • Caused by impaired contractility or excessive afterload

  • Accounts for 2/3 of heart failure

  • Conditions that impaire CTY: MI, myocardial ischemia, volume overload (MR and AR),

dilated cardiomyopathy

  • Conditions that increase afterload: Aortic stenosis and hypertension

Etiology: Impaired contractility is caused by:

  • 1.

    destruction of myocytes

  • 2.

    abnormal myocyte function

  • 3.


Increased afterload is caused by pressure overload, which resistance to flow

Pathophysiology: a decrease in contractility causes a decrease in SV and an increase in end-systolic volume and pressure. During the next cardiac cycle, the ventricle receives a normal amount of blood from the lungs, resulting in an increased end-diastolic volume and pressure (increased preload.) Increased preload results in an increase in SV (Frank- Starling) and a reduction in end-systolic volume. However, increased preload cannot completely compensate for the decreased CTY and ejection fraction, so end-systolic volume remains higher than normal. The increased diastolic pressure is transmitted to the LA and the pulmonary veins and capillaries. If pulmonary capillary hydrostatic pressure rises above 20mmHg, then fluid collects in the interstitum of the lungs and causes pulmonary congestion.

CTYÆ SVÆ ↑↑ ESVÆ ↑↑ preload Æ SVÆ ESV. However, ESV is still higher than normal, therefore: EDP and VÆ pulm hydrostatic P Æ congestion

For increased afterload, increased resistance to flow results in pressure overload, which causes a decrease in stroke volume and an increase in end-systolic volume and a subsequent increase in end-diastolic volume and pressure. Leads to increased pulmonary capillary hydrostatic pressure and pulmonary congestion.

afterloadÆ resistanceÆ SVÆ ESVÆ EDV/ PÆ pulm hydrostatic PÆ congestion

Remember: systolic dysfunction results from problem with ventricular emptying (ESV)

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