Caring for the Critical Cardiac Patient

Cardiovascular System Overview

• Function: Delivers oxygenated blood to tissues and returns deoxygenated blood to the heart.

• Heart's Role: Propels blood from left side into the aorta for systemic circulation, providing nutrients and oxygen.

• Cardiac Output: Varies with metabolic demands; increases with activity, decreases at rest.

• Venous Return: Blood returns to the right heart via the superior and inferior vena cava, then to lungs for gas exchange.

Anatomy and Physiology of the Heart

• Key Structures:

  • Right pulmonary arteries

  • Left pulmonary arteries

  • Aorta

  • Superior vena cava

  • Inferior vena cava

  • Various heart chambers (atria and ventricles)

  • Valves (tricuspid, bicuspid/mitral, aortic, pulmonary)

  • Layers of the heart wall (endocardium, myocardium, epicardium)

Vascular System

• Components: Arteries, veins, and capillaries.

• Blood Transport:

  • Arteries carry oxygenated blood.

  • Veins return deoxygenated blood to the heart.

• Functions:

  • Delivery of oxygenated blood to tissues.

  • Removal and transport of waste products.

  • Return of circulatory volume;

  • Return of lymph fluid to circulation.

Cardiac Conduction System

• Key Characteristics:

  • Automaticity: Cardiac cells generate impulses independently (e.g., SA Node: 60-100 bpm).

  • Excitability: Ability to respond to stimuli.

  • Conductivity: Transmission of impulses among cardiac tissue.

• Conduction Pathway: SA Node → AV Node → Bundle of His → Bundle Branches → Purkinje Fibers.

Cardiac Conduction Pathway Details

1. SA Node fires (initiating heartbeat).

2. Impulse spreads through atrial myocardium.

3. Travels to the AV Node.

4. Leaves the AV Node via the Bundle of His.

5. Travels through Bundle Branches.

6. Extends into ventricular tissue via Purkinje fibers.

Key Terms in Cardiac Function

• Diastole: Relaxation phase; filling of ventricles.

• Systole: Contraction phase; ejection of blood.

• Cardiac Output: Heart Rate (HR) x Stroke Volume (SV); normal output: 4 to 8 L/min.

ECG and Dysrhythmias

• ECG: Graphic representation of the heart's electrical activity.

• Lead II: Best for rhythm determination.

• Waves: P (atrial depolarization), QRS (ventricular depolarization), T (ventricular repolarization), U (rare).

• ECG Interpretation:

  • Assess rate, rhythm, presence of waves, and intervals.

Cardiac Dysrhythmias

• Defined: Irregularities in conduction pathways or electrical impulse disorders.

• Symptoms: Palpitations, hypotension, diaphoresis, shortness of breath, syncope.

Treatments for Cardiac Dysrhythmias

• Cardioversion: Controlled electrical discharge to restore normal rhythm.

• Defibrillation: Uncontrolled electrical discharge during any cardiac cycle.

• Pacemaker: Manages heart rhythm (temporary or permanent).

Supraventricular Tachycardia (SVT)

• Originates above ventricles; narrow QRS complex, 150-250 bpm.

• Treatment: Adenosine, cardioversion.

Heart Blocks

• Types: First Degree, Second Degree (Type I & II), and Third Degree.

• Management: Often only symptomatic treatment; can need pacing or other interventions.

Myocardial Infarction (MI)

• Definition: Destruction of heart muscle due to insufficient oxygen (atherosclerosis is common cause).

• Types: Stable angina, unstable angina, NSTEMI, STEMI.

• Symptoms: Chest pain, shoulder or arm pain, jaw pain, shortness of breath, diaphoresis.

Nursing Care for Myocardial Infarction

• Diagnostics: Troponins, ECG, and cardiac enzymes.

• Management: O2, pain control, medications (antiplatelet, anticoagulation, thrombolytics).

Valvular Disease Assessment & Management

• Types: Stenosis, insufficiency, regurgitation.

• Symptoms: Mimic congestive heart failure (CHF); fatigue, palpitations, edema.

• Management: Medications and surgical interventions.

Heart Failure Overview

• Classification: Based on ejection fraction (normal 55-70%).

• Symptoms: SOB, JVD, edema.

• Diagnostics: Lab tests, imaging, and hemodynamic monitoring.

• Management: Medications (diuretics, ACE inhibitors, beta blockers).

Infective Endocarditis

• Causes: IV drug use, bacterial infections.

• Symptoms: Fever, heart murmur, signs of heart failure.

• Diagnostics: Blood cultures, echocardiography.

Nursing Actions for Infective Endocarditis

• Administer IV antibiotics, monitor vitals, provide patient education.

Cardiomyopathy Types

• Dilated: Most common; leads to heart failure.

• Hypertrophic: Can lead to sudden cardiac death.

• Restrictive: Impaired filling due to stiffening of cardiac muscles.

Aneurysms Overview

• Locations: Thoracic and abdominal aortic aneurysms.

• Complications: Dissection and rupture are critical.

Cardiogenic Shock

• Cause: Inadequate myocardial contractility; often secondary to MI.

• Symptoms: Low output, hypotension, organ dysfunction.

• Management: Identification and treatment of underlying causes, supportive measures, surgical interventions.