Cardiac Output and Heart Failure Overview

Cardiac Output Explained

• Cardiac output (CO) is the amount of blood the heart pumps per minute
• CO depends on heart rate, contractility (force of heart muscle contraction), preload (amount of blood in ventricle before contraction), and afterload (pressure the heart must overcome to open the aortic valve and eject blood)
• Stroke volume multiplied by heart rate equals cardiac output
• Alterations in these factors can lead to decreased ventricular function and heart failure (HF)
• Low heart rate results in low CO, even with normal stroke volume
• High afterload requires the heart to work harder, reducing stroke volume and CO
• Diuretics reduce preload by decreasing fluid volume
• Vasodilators (nitrates) reduce afterload by widening blood vessels, making it easier for the heart to pump
• Inotropic drugs (digoxin) improve myocardial contractility, which increases stroke volume

Heart Failure and Cardiac Output

• Heart failure (HF) is an abnormal syndrome with impaired cardiac pumping or filling
• HF leads to reduced exercise tolerance, diminished quality of life, and shortened life expectancy
• HF can be caused by interference with normal CO regulation mechanisms

Pulmonary Embolism and Cardiac Output

• Acute PE, a pulmonary vasculature obstruction, is usually caused by a thrombus
• Acute PE is serious and life-threatening
• PE can lead to hemodynamic instability, including sustained hypotension, hypoxia, and altered consciousness
• PE can also impact CO

Types of Heart Failure

• Systolic heart failure: Left ventricle loses ability to contract forcefully, causing a pumping problem
• Diastolic heart failure: Left ventricle stiffens and can't relax or fill completely, causing a filling problem (also known as heart failure with preserved ejection fraction)
• Left-sided heart failure: Blood backs up into the left atrium and pulmonary veins, leading to pulmonary congestion
• Right-sided heart failure: Blood backs up into the right atrium and venous circulation, leading to systemic venous congestion and peripheral edema. Often a consequence of left-sided failure but can also be caused by right ventricular infarction

Classifying Heart Failure

• New York Heart Association Functional Classification system categorizes heart failure into four classes based on patient's tolerance for physical activity
• Class 1: No limitations, ordinary activities don't cause fatigue, shortness of breath, palpitations, or chest pain
• Class 2: Slight limitations, ordinary activities lead to fatigue, shortness of breath, palpitations, or chest pain
• Class 3: Marked limitations, fatigue, shortness of breath, palpitations, or chest pain during activities
• Class 4: Unable to perform any physical activity without discomfort; symptoms even at rest, increased with activity

Clinical Manifestations

• Left-sided HF symptoms: Decreased cardiac output (fatigue, weakness, oliguria, angina, dizziness, confusion, restlessness, tachycardia, palpitations, pallor, weak peripheral pulses), pulmonary congestion (cough, worse at night, dyspnea, crackles/wheezes in lungs, frothy, pink-tinged sputum, tachypnea)
• Right-sided HF symptoms: Systemic congestion (jugular vein distension, increased/decreased blood pressure, enlarged/distended liver/spleen, anorexia, nausea, distended abdomen, dependent edema, swollen hands/fingers, polyuria at night)

Heart Failure Complications

• Pleural effusion: Fluid buildup in the space surrounding the lungs
• Dysrhythmias: Irregular heart rhythms, most commonly atrial fibrillation. This can reduce cardiac output and increase stroke risk

Management of Heart Failure

• Acute HF: Goal is to stabilize patient and improve left ventricle function; strategies include reducing intravascular volume and venous return (preload), decreasing afterload, improving gas exchange and oxygenation, increasing cardiac output, and reducing anxiety
• Chronic HF: Focus is on treating the underlying cause, maximizing cardiac output, reducing cardiac workload, managing comorbidities (like arrhythmias, hypertension, coronary artery disease), promoting physical rest, and emotional well-being (including nutrition and medication management)

Nursing Care in Heart Failure

• Assessment: Identify signs and symptoms of HF, monitor vital signs, fluid status, and activity tolerance.
• Diagnosis: Develop nursing diagnoses related to decreased cardiac output, activity intolerance, fluid volume excess, and knowledge deficit.
• Planning: Develop individualized care plans to improve symptoms, enhance exercise tolerance, ensure medication adherence.
• Implementation: Administer medications, monitor I&O, provide oxygen therapy, educate patients and families.
• Evaluation: Evaluate effectiveness of interventions, modify care plan as needed.

Long-Term Management and Nursing Considerations

• Cardiac rehabilitation programs are encouraged for chronic HF; include education, supervised exercise, and peer support programs to improve quality of life and management of HF.
• Patients should be educated about the importance of following a low-sodium diet and how to read food labels to identify hidden sources of sodium.

Understanding and Managing Pulmonary Embolism (PE)

• PE: Blockage of pulmonary arteries typically caused by a blood clot (thrombus) traveling from deep veins in the body, usually legs,(DVT)
• PE severity ranges from acute (potentially life threatening, possibly with low blood pressure) to submassive (unstable PE, with sustained low blood pressure) to massive (most severe, sustained low blood pressure, pulselessness or profound bradycardia with shock symptoms)
• Key risk factors are venous stasis (slowing of blood flow), endothelial injury (damage to blood vessels), and hypercoagulability (blood prone to clotting)
• Clinical presentations: pleuritic chest pain (worsens with breathing), dyspnea, tachypnea, tachycardia, unilateral lower extremity edema, calf tenderness, hemodynamic instability

Diagnosing PE

• Clinical assessment, lab tests, and imaging studies; history and physical exam are crucial.
• Chest X-ray (CXR) to rule out other conditions.
• Cardiac biomarkers can be elevated in PE, but not diagnostic
• D-dimer test can suggest clot presence. The test may be elevated also with other conditions.
• CTPA (gold standard) is imaging for PE diagnosis
• Echocardiogram (ECHO) is used to assess heart function

This quiz explores the concept of cardiac output (CO) and its critical role in heart function. It covers factors affecting CO, the implications of heart failure, and the impact of conditions like pulmonary embolism on cardiac performance. Test your understanding of these key cardiovascular principles!