Heart Failure

[Pages:17]Heart Failure

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Reviewed December 2021, Expires December 2023 Provider Information and Specifics available on our Website

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?2021 ?, S.A., ?, LLC

By Wanda Lockwood, RN, BA, MA

Purpose

The purpose of this course is to describe the causes of chronic heart failure, the different types and classification systems, the symptoms of right ventricular failure and left ventricular failure, compensatory mechanisms, treatment and medications as well as symptoms and treatment of acute heart failure.

Goals

Upon completion of this course, the healthcare practitioner should be able to: ? Describe the normal cardiac circulation. ? Provide definitions for cardiac terminology. ? List and describe at least 6 causes of heart failure. ? Discuss at least 5 diagnostic procedures. ? Differentiate between systolic and diastolic heart failure. ? Describe at least 7 symptoms associated with left ventricular failure. ? Describe 4 primary symptoms associated with right ventricular failure. ? Differentiate between the New York Heart Association and the American College of Cardiology-American Heart Association classification systems. ? Describe at least 5 compensatory mechanisms and the adverse effects related to these mechanisms. ? Describe at least 6 treatment approaches to chronic heart failure. ? Discuss at least 5 medications used to treat chronic heart failure. ? Explain how acute heart failure relates to chronic heart failure. ? Describe emergency treatment options for acute heart failure.

Introduction

About 5.8 million people in the United States have heart failure, with 670,000 newly diagnosed each year. Because diagnosis is often delayed, 20% die within a year of diagnosis, so early diagnosis and proper medical management are critical to survival. In a normal heart, blood flows into the right atrium from the superior and inferior vena cava. As the right ventricle relaxes after contraction, blood is pulled from the right atrium through the tricuspid valve into the right

ventricle and then propelled through the pulmonary valve and into the pulmonary artery with the next ventricular contraction. Blood circulates in the lungs to release carbon dioxide and gain oxygen and then returns by the pulmonary veins to the left atrium. From there, the blood travels through the mitral valve to the left ventricle, and with the next contraction, ejected through the aortic valve to the aorta and throughout the body.

If all the vascular pressures are correct, the heart muscle strong, the lungs functioning properly, and the valves opening and closing correctly, this process is usually extremely efficient. However, if the ventricles cannot contract strongly enough to pump blood adequately, the valves are impaired, or the ventricles are too stiff to fill properly, heart failure occurs. Heart failure is not a primary disease but can result from numerous other disorders. Heart failure is often referred to as congestive heart failure (CHF), but CHF actually refers to an end-stage of heart failure in which "congestion" of the body with pulmonary and peripheral edema occurs.

Cardiac terminology

Stroke volume Volume of blood ejected from the heart

(SV)

with each contraction.

(End-diastolic volume ? end-systolic

Values (adult)

55 ? 100 mL

Cardiac output (CO)

End-diastolic volume (EDV) End-systolic volume (ESV) Ejection fraction (Ef)

Heart rate Preload (Volume)

Afterload (Pressure/ Resistance)

Systemic vascular resistance (SVR)

volume = SV) Total volume of blood ejected from the heart in on minute. (Heart rate (HR) X SV =CO) Volume of blood in filled ventricles.

Volume of blood left in ventricles after contraction. Fraction (expressed as percentage) of blood pumped from ventricles during contraction (usually refers to left ventricle). (Ef = SV/EDV Number of heart beats per minute Degree of elasticity (stretch) in the myocardium with end-diastolic volume. Increased stretch (and volume) correlates with increased contraction. Degree of systemic vascular resistance to ventricular contractions (left ventricular ejection of blood through the aorta and systemic circulation and right ventricular ejection of blood to the pulmonary vascular system). Resistance in the peripheral vascular system to left ventricular ejection. Vascular resistance is determined by tone in small and pre-capillary arterioles and by viscosity of blood.

4.9 L /min

120 mL 50 mL 55 ? 75%

60 ? 80 BPM (Estimated with EDV--cannot be measured in vivo).

What causes heart failure?

The primary risk factors for heart failure are coronary artery disease and advancing age, but a number of different disorders may bring about heart failure. If disorders associated with increased risk are diagnosed early and treated, heart failure may be averted in some cases.

Common causes of heart failure

Coronary artery Decreases oxygenation of the heart muscle, interfering with

disease (60%) the conduction system that stimulates the heart to contract

and with the ability of the ventricles to properly contract.

Myocardial

May cause structural damage that interferes with function of

infarction

heart muscle or may interfere with conduction system.

Remodeling of left ventricle is common after MI.

Cardiomyopathy ? Hypertrophic: Causes thickened ventricular walls with

inability to effectively pump blood throughout the body

Congenital heart defects Valvular disease

Diabetes mellitus Hypertension Arrhythmias

Chronic kidney disease Obesity

and may cause arrhythmias that further impair contractions. ? Dilated: Causes damage to heart muscle (from coronary artery disease, MI, myocarditis), which weakens and dilates ventricles, interfering with ability to contract. ? Restrictive: Causes stiffened heart muscles that cannot contract adequately.

? May interfere with flow of blood through the heart, oxygenation, and/or ability of the heart to pump.

? Stenosis: Increases the work of the heart muscle to circulate blood, causing hypertrophy as the heart tries to overcome the restriction.

? Insufficiency (regurgitation): Increases the work of the heart muscle, causing enlargement (dilation) and decreased pumping ability.

Associated with hyperlipemia and atherosclerosis, increasing work of the heart. Hyperglycemia may impair cardiac muscle. Increases systemic vascular resistance to blood flow, increasing work of heart. Interfere with the ability of the heart to effectively circulate blood, so heart works harder but less effectively. May decrease cardiac output and increase workload and oxygen demands of the myocardium. Resulting hypertension increase systemic vascular resistance and retention of sodium and water increases workload on the heart. Left ventricular hypertrophy common as the heart works harder to supply the body with adequate amounts of oxygenated blood.

In addition to diseases and disorders that can cause heart failure, a number of precipitating factors may lead to heart failure:

? Anemia stimulates the heart to increase cardiac output to compensate for decreased oxygen-carrying capacity.

? Infection increases need for tissue oxygenation, stimulating increased cardiac output.

? Malnutrition may impair cardiac function by decreasing myocardial muscle mass and ability to contract.

? Hypervolemia increases preload and causes volume load on right ventricle.

? Pulmonary embolism increases pulmonary pressure, exerting increased pressure on the right ventricle and causing right ventricular hypertrophy and failure.

Diagnosis

Because heart failure results from another disease process, the first step in diagnosis is to determine the underlying cause with a complete history and physical examination.

? Blood gases, chemistries, and liver function tests: Help identify underlying cause and damage related to HF.

? Chest X-ray: Identifies an enlarged heart or indications of pulmonary edema.

? Echocardiogram: Shows valve function, flow of blood through heart, and ejection fraction (to help differentiate between diastolic and systolic heart failure). Most common test for EF.

? Electrocardiogram: Identifies cardiac damage, arrhythmias. ? Exercise stress testing: Shows functional limitations. ? Plasma natriuretic peptide levels: Correlate with degree of LV dysfunction. ? Nuclear imaging studies, MRI, cardiac catheterization: May be indicated in

some patients.

How is heart failure described?

Heart failure may be described in relation to the type of impairment--pumping (systole) or filling (diastole)--or by the primary site of impairment--right or left ventricular. In most cases, biventricular failure occurs as heart failure progresses, but heart failure most commonly first begins with left ventricular /systolic failure, which leads to right ventricular failure although signs of heart failure may become more evident with right ventricular failure.

Systolic failure (Pumping)

Most heart failure derives from systolic failure, or the inability of the heart to adequately pump blood because of a defect in the ventricles. Typically, the left ventricles cannot generate adequate pressure to eject blood through the aorta. The most common causes of systolic failure are those that interfere with contractility, such as myocardial infarction, hypertension, cardiomyopathy, and valvular heart disease. Evaluation of the ejection fraction (EF) differentiates systolic from diastolic failure. Systolic failure is associated with a decrease in EF ................
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