Learning Outcomes
By the end of this section, you should be able to:
- 19.1.1 Describe the pathophysiology of heart failure and ventricular dysfunction.
- 19.1.2 Identify clinical manifestations associated with heart failure and ventricular dysfunction.
- 19.1.3 Identify etiology and diagnostic studies related to heart failure and ventricular dysfunction.
Pathophysiology of Heart Failure
The importance of cardiac output cannot be stressed enough; it is necessary for every organ in the body. Cardiac output is a function of heart rate (HR) and stroke volume (SV): . Normal resting CO is 4–5 liters per minute. Heart rate is the number of times the heart beats per minute. Stroke volume is the amount of blood pumped out of the left ventricle with each heartbeat. Stroke volume is a function of preload, afterload, and contractility. Preload is the volume of blood returning to the heart, afterload is the amount of pressure that the left ventricle must push against, and contractility is the ability of the left ventricle to squeeze or pump blood. Stroke volume is often measured by ejection fraction, or the percentage of blood that is pumped out of the left ventricle with each beat (Hajouli & Ludhwani, 2022). It is important to note that the entire volume of the left ventricle is not pumped out with each beat; a small portion remains in the chamber. Factors affecting cardiac output can be seen in Figure 19.2.
In order for the heart to produce adequate stroke volume, the left ventricle must be able to fill well (preload) and squeeze well (contractility). Contractility requires adequate muscle tissue (adequate cardiac myocytes), which must receive an adequate blood supply. So, the heart itself is dependent on cardiac output.
Heart failure occurs when the heart is no longer able to generate an adequate cardiac output. Heart failure is a result of ventricular dysfunction; something has affected ventricular preload or contractility in such a way that the ventricle is no longer able to expel blood effectively (Malik et al., 2022). This leads to decreased perfusion of all tissues. There are two ways in which the heart is not able to maintain cardiac output. One is caused by a reduced ejection fraction and is called heart failure with reduced ejection fraction (HFrEF). The other, called heart failure with preserved ejection fraction (HFpEF), occurs when the actual ejection fraction is not reduced but cardiac output is still decreased.
Heart Failure with Reduced Ejection Fraction
Heart failure with reduced ejection fraction is a problem stemming from inadequate contractility. It is the most common type of heart failure. There are multiple causes of HFrEF, including coronary artery disease and acute myocardial infarction (AMI). Both cause decreased oxygenation to the individual cardiac muscle cells or cardiac myocytes. Because the cardiac myocytes have less oxygen than they need, they are not able to contract well. In the case of an AMI, the myocytes have had their oxygen supply cut off, and so there is cell death. Dead myocytes don’t contract at all.
Hypertension is also a common cause of HFrEF. Long-standing untreated hypertension increases afterload and causes the left ventricle to work harder to eject blood. Initially, the left ventricle can hypertrophy (thicken) to push against the increased resistance (see Figure 19.3). After many years, the left ventricular hypertrophy can’t keep up with the increased resistance, and the heart is unable to maintain an adequate cardiac output. Because contractility and afterload are considered part of systole, this was traditionally referred to as systolic heart failure.
Heart Failure with Preserved Ejection Fraction
Heart failure with preserved ejection fraction stems from muscle stiffness. As people age, muscles can become stiff and not move as well as they did in younger years. This also can happen to the left ventricle; the muscle tissue can become stiff, which does not allow for adequate ventricular opening. If the ventricles cannot open well, then they cannot fill well. If the ventricle cannot fill well, this decreases preload, which then decreases stroke volume.
Recall that ejection fraction (EF) is the percentage of blood pumped from the heart with each beat (EF is defined as blood ejected from the left ventricle divided by total volume of blood in the left ventricle at the end of diastole). In HFpEF, less blood fills the ventricle during diastole (thus there is lower total volume at the end of diastole/lower preload, the denominator in the above equation), and less blood is pumped out of the left ventricle (lower stroke volume and thus lower cardiac output, the numerator in the above equation). Therefore, both the denominator and numerator of the equation change proportionally and the ratio, or ejection fraction, remains the same despite cardiac output being lower. Hence the name heart failure with preserved ejection fraction. Because preload is considered part of diastole (or ventricular filling), this type of heart failure traditionally was referred to as diastolic heart failure.
The main treatment for HFpEF is control of hypertension and other comorbidities, if present. (Hypertension is discussed in more detail in Antihypertensive and Antianginal Drugs.) Nearly all pharmacologic treatments for heart failure are specific to heart failure with reduced ejection fraction. The Pharmacologic Treatment of Heart Failure section will pertain to heart failure with reduced ejection fraction.
Classification and Staging of Heart Failure
Heart failure is diagnosed based on ejection fraction and symptoms. The American Heart Association (AHA)/American College of Cardiology (ACC)/Heart Failure Society of America (HFSA) Guidelines state that a normal ejection fraction is between 50% and 70% (Heidenreich et al., 2022). If a person has an ejection fraction of less than 40%, a diagnosis of heart failure with reduced ejection fraction is made. Heart failure with mildly reduced ejection fraction means that a person has symptoms of heart failure but the ejection fraction is between 41% and 50%. Heart failure with preserved ejection fraction is diagnosed when there are symptoms of heart failure but the ejection fraction is still in the normal range (see Table 19.1).
| Type of Heart Failure | Criteria |
|---|---|
| Heart failure with reduced ejection fraction (HFrEF) | Left ventricular ejection fraction ≤40% |
| Heart failure with mid-range ejection fraction (HFmrEF) | Left ventricular ejection fraction 41%–49% with symptoms of heart failure |
| Heart failure with preserved ejection fraction (HFpEF) | Left ventricular ejection fraction ≥50% with symptoms of heart failure |
Heart failure is staged based on risk and evidence of structural damage (see Table 19.2). The Pharmacologic Treatment of Heart Failure section will pertain to Stage C: Symptomatic Heart Failure.
| Stage A At Risk for Heart Failure |
Stage B Pre–heart Failure |
Stage C Symptomatic Heart Failure |
Stage D Advanced Heart Failure |
|---|---|---|---|
| Clients are at risk for heart failure but don’t have signs or symptoms or any damage to the pumping ability of the heart. | Clients don’t have signs or symptoms of heart failure but do have some type of damage to the pumping ability of the heart. | Clients have signs and/or symptoms of heart failure and have damage to the pumping ability of the heart. | Clients have significant signs and/or symptoms of heart failure that interrupt activities of daily living and often cause hospitalization. |
Diagnostics
It can be difficult to diagnose heart failure because it is based on symptom recognition. People often have symptoms but don’t recognize them as a manifestation of heart failure. In order for heart failure to be diagnosed, a health care provider must do a thorough history and physical exam. If there are signs and symptoms of heart failure, the provider will order an echocardiogram. In an echocardiogram, sound waves are used to assess how well the heart is pumping and to determine the heart’s ejection fraction. Other tests that may be performed include an electrocardiogram to assess cardiac rhythm and blood work. Typical blood work includes a basic metabolic profile, which will include information on electrolytes and kidney function. One other blood test that is often included is a brain natriuretic peptide (BNP) to determine whether the heart is undergoing increased stretch. When cardiac myocytes are stretched too far, they release BNP (Novack & Zevitz, 2022). This test often helps providers determine the stage of heart failure.
Clinical Manifestations
Heart failure often occurs after another disease process has damaged the cardiovascular system. The most common causes of HFrEF are coronary artery disease, acute myocardial infarction, and prolonged hypertension. The most common cause of HFpEF is aging. Therefore, heart failure is often a disease of older clients, though it is not exclusive to that age group. Symptoms associated with heart failure include shortness of breath, edema, exercise intolerance, and fatigue. Often people with heart failure have an increased heart rate due to the body’s compensatory mechanisms. Remember: . If stroke volume is decreased, then the body will compensate by increasing heart rate.
Nonpharmacologic Treatment of Heart Failure
Nonpharmacologic treatments for heart failure include sodium restriction. A sodium-restricted diet (less than 2000 mg of sodium per day) may help maintain euvolemia (normal blood volume) and prevent clients from becoming overloaded with fluid (which presents as pitting edema in the extremities, abdominal edema, and/or pulmonary edema). It is also important for people with heart failure to eat a healthy diet and exercise as well as they are able. Additionally, smoking cessation, reduced or no use of alcohol, and self-monitoring of signs and symptoms may be helpful.
Dietary Modification
Dietary modification for clients with heart failure are similar to those for clients with hypertension (see Antihypertensive and Antianginal Drugs). Clients with heart failure should follow a 2000 mg/day sodium-restricted diet and are often instructed to record the amount of sodium they consume daily. Clients should be instructed on how to read Nutrition Facts labels on food in order to determine the amount of sodium per serving or per container. Clients should be made aware that most processed foods are very high in sodium. Fast food, processed frozen meals, and canned foods all have very high sodium content. The client can be referred to the American Heart Association’s recipe collection for low-sodium, heart-healthy meals.
Clients who take certain medications for heart failure (discussed later in this chapter) should be instructed to avoid foods high in potassium, such as bananas and watermelon, as well as salt substitutes because most substitute potassium for sodium.
Physical Activity and Exercise
Clients with heart failure often experience shortness of breath and fatigue with exercise; however, they should be encouraged to exercise as much as they are able. Many clients with heart failure are not able to fully follow the exercise recommendations of the American Heart Association (see Antihypertensive and Antianginal Drugs), but they can be encouraged to follow an individualized exercise plan. As an alternative, the health care provider may enroll them in cardiac rehabilitation to build their exercise tolerance.
Smoking Cessation and Reducing Alcohol Consumption
Clients should be encouraged to stop using any tobacco products and/or alcohol. Both can cause heart failure exacerbations. For more information on smoking cessation and decreasing alcohol consumption, see Antihypertensive and Antianginal Drugs.
Self-Monitoring of Heart Failure Symptoms
Clients with heart failure should monitor their symptoms daily. This includes weighing themselves every day, monitoring how well they are breathing, assessing for lower extremity swelling, and determining their level of fatigue. Clients should notify their health care provider if they gain 2–3 pounds in one day or 5 pounds in one week or if they notice increased swelling in their extremities, difficulty breathing, and/or chest pain. The American Heart Association website (n.d.) has many interactive resources available to help clients monitor their symptoms, including a phone app.
Pharmacologic Treatment of Heart Failure
The primary goal of treatment for clients with heart failure is to reduce morbidity and mortality. Another goal is to decrease the cardiac workload and the heart’s demand for oxygen. There are five guideline-directed classifications of medications for HFrEF (Heidenreich et al., 2022):
- Medications affecting the renin-angiotensin aldosterone system:
- Angiotensin-converting enzyme inhibitors (ACE inhibitors)
- Angiotensin receptor blockers (ARBs)
- Angiotensin receptor/neprilysin inhibitors (ARNIs)
- Mineralocorticoid receptor agonists (MRAs)
- Beta-adrenergic blockers (beta blockers)
- Sodium-glucose cotransport inhibitors (SGLT2Is)
- Diuretics
ACE inhibitors, ARBs, ARNIs, and MRAs all affect some component of the renin-angiotensin-aldosterone system (RAAS) and are grouped together in Section 19.2. Beta blockers are discussed in Antihypertensive and Antianginal Drugs, but this chapter will highlight the use of them in the management of heart failure. SGLT2Is were primarily used to treat type 2 diabetes but recently were found to be useful in heart failure. Clients with heart failure often have volume overload, so it is also important to control symptoms that are caused by volume overload. Diuretics are part of first-line treatment and are used to modify symptoms of fluid volume overload.
Other drugs are also used in the treatment of heart failure. Adjunct medication therapy will be discussed in Section 19.6.
Client Teaching Guidelines
The client taking a heart failure medication should:
- Take heart failure medications as prescribed by their health care provider.
- Monitor their symptoms of heart failure daily or as directed by their health care provider and keep a record of the symptoms.
- Call their provider if they experience increased ankle swelling, difficulty breathing, and/or chest pain.
- Monitor their weight daily or as directed by the health care provider and keep a record.
- Notify their health care provider if their weight fluctuates 2 pounds in one day or 5 pounds in one week.
- Avoid alcohol, caffeine, and tobacco because these may interfere with the action of cardiovascular drugs.
The client taking heart a failure medication should not:
- Take a double dose of the heart failure drug. If the client misses a dose of their drug, they should take it as soon as they remember—unless it’s almost time for the next dose. In that case, they should wait and take the next dose at the normal time.
- Abruptly discontinue a heart failure drug without consulting with the health care provider because with some drugs this may cause rebound elevated blood pressure and an elevated pulse rate.
- Take over-the-counter (OTC) drugs and/or herbal supplements without consulting with their health care provider or pharmacist.
Other concerns:
- Heart failure drugs may cause orthostatic hypotension (a form of low blood pressure that occurs when going from a sitting or lying position to a standing position). The client should change positions slowly to prevent dizziness and fainting.
- If low blood pressure develops (feeling dizzy or lightheaded, having blurred vision, feeling weak, or fainting), the client should lie on their back with legs elevated and notify their health care provider.
- If the client is unsure about how to take their heart failure drug, they should call their health care provider or pharmacist.
- If the client is vomiting or otherwise unable to take their medications for more than one day, they should notify their health care provider.