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Common Congenital Heart Lesions - page 84 / 126





84 / 126

84 of 126

Diastolic Dysfunction: heart failure that results from an abnormality in diastolic relaxation or ventricular filling.

  • Accounts for 1/3 of heart failure

  • Causes of impaired ventricular relaxation: LVH, hypertrophic cardiomyopathy,

restrictive cardiomyopathy, myocardial ischemia, fibrosis

  • Causes of impaired filling: Mitral Stenosis, pericardial constriction to tamponade

Etiology: Impaired diastolic relaxation is an active, energy-dependent process. Any condition that inhibits energy delivery to ventricles will impair diastolic relaxation (ex: acute myocardial ischemia.)

Impaired ventricular filling is caused by increased stiffness of the ventricular wall (ex: fibrosis, LVH)

Pathophysiology: decreased compliance of ventricle requires higher pressure to push blood from the atria into the ventricles during diastole. Elevated pressure is transmitted to the pulmonary vasculature (causing pulmonary congestion) or systemic vasculature (causing peripheral edema.)

ComplianceÆ EDPÆ hydrostatic PÆ pulmonary congestion or edema

**Both systolic and diastolic dysfunction can result in right and left-sided heart failure.

Right-sided heart failure: Key differences from left-sided failure

  • 1.

    RV has thin walls and is very compliant. Therefore, it can accept lots of blood without big increases in pressure

  • 2.

    RV ejects against the low-pressure pulmonary vasculature. Therefore, it cannot tolerate large increases in afterload, and conditions that cause sudden increase in afterload (ex: pulmonary embolism) will cause right-sided heart failure.

  • 3.

    Most common cause of R-sided heart failure: left-sided heart failure (increased pulmonary pressure)

  • 4.

    Cor pulmonade: right-sided heart disease secondary to pulmonary dysfunction, major cause of isolated right heart failure

  • 5.

    Right heart failure causes left heart failure: decreased outflow from right ventricle results in decreased flow to the LA, causing decreased SV

Compensatory Mechanisms

Heart failure results in a decrease in SV and CO. As a result, BP falls (hypotension.) All of the following compensatory mechanisms are things that the body does to raise BP.

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