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Alterations in Cardiovascular Function and Perfusion

This document provides an exhaustive overview of cardiovascular alterations, particularly focusing on Coronary Artery Disease (CAD), Acute Coronary Syndrome (ACS), heart failure, and atrial dysrhythmias. Each section includes clinical manifestations, diagnostic criteria, and treatment protocols crucial for understanding these conditions in intermediate medical surgical contexts.

Coronary Artery Disease (CAD)

  • Definition: Atherosclerosis causes narrowing or occlusion of the arteries.

  • Pathophysiology: Decreased blood flow resulting from partially or completely blocked arteries leads to decreased oxygenation and perfusion of the myocardium.

  • Risk Factors:
      - Non-modifiable: Age, gender, family history of heart disease.
      - Modifiable: Smoking, hypertension, diabetes, hyperlipidemia, sedentary lifestyle, obesity.

Acute Coronary Syndrome (ACS)

Types of ACS

  1. Stable Angina
       - Characteristics: Angina pain arises during increased myocardial demand due to stable atherosclerotic plaque. The vessel cannot dilate sufficiently for adequate blood flow to meet myocardial demand.
       - Duration: Pain lasts a few minutes, subsiding when the precipitating factor is resolved through rest or sublingual nitroglycerin (SL NTG).
       - ECG Changes: Ischemic changes on a 12-lead ECG display ST segment depression or T wave inversion, returning to normal once blood flow is restored and pain alleviated.

  2. Unstable Angina
       - Characteristics: Angina occurs at rest or progresses rapidly over a brief time; pain is new onset, occurring with increased frequency, duration, or less effort than in stable angina.
       - Duration: Pain lasts more than 10 minutes.
       - ECG Changes: Displays ST depression and/or T wave inversion indicating ischemic changes. Immediate treatment is necessary.

  3. NSTEMI (Non-ST Segmented Myocardial Infarction)
       - Characteristics: Result of plaque rupture and thrombus formation leading to partial occlusion and injury to the subendocardial myocardium.

  4. STEMI (ST-Segment Myocardial Infarction)
       - Characteristics: Characterized by complete occlusion of the blood vessel lumen, resulting in transmural injury and infarction of myocardial tissue, reflected by ECG changes and an increase in troponins.
       - ECG Indicators: Shows hyperacute T waves or ST elevation alongside elevated troponin levels.

Ischemia and Cardiovascular Changes

  • Demand Ischemia: Indicates conditions without infarct; ECG remains relatively normal.

  • Supply Ischemia: May present with normal or inverted T waves, or ST depression.

Clinical Manifestations of ACS

  • Common Symptoms:
      - Angina: Tightness, pressure, or pain in the midsternal area, often radiating to the left arm, neck, jaw, or back.
      - Pain associated with activity in stable angina versus pain at rest in unstable angina.

  • Special Considerations: Female patients, seniors, and clients with diabetes may experience atypical presentations.

Additional Symptoms Associated with Myocardial Infarction

  • Nausea and Vomiting: Elicit reflexes from severe pain.

  • Fever: A systemic inflammatory response from heart cell death, measured up to 100.4°F (38°C) within the first two days following the event.

Complications of Myocardial Infarction

  • Dysrhythmias: Most common complication, present in 80% to 90% of microinfarction patients, arising from ischemia, electrolyte imbalances, or sympathetic nervous system stimulation.

  • Risk Factors for Death: Ventricular tachycardia (VT) and ventricular fibrillation (VF) are leading causes of death during the prehospitalization period.

Management of STEMI

  • Emergency Response: The goal is to reopen the blocked artery within 90 minutes following symptom onset.

  • Interventions: Utilize cardiac catheterization, followed by percutaneous coronary intervention (PCI), thrombolytics, or stent placement to restore blood flow.

Treatments in ACS

Medications

  • Acute Management:
      - Pain relief via morphine or fentanyl.
      - Nitrates to reduce heart workload.
      - Thrombolytics to dissolve clots.
      - Antiplatelet agents and anticoagulants to prevent further clotting.
      - Supplemental oxygen as needed.

  • Chronic Management:
      - ACE Inhibitors: Help to decrease blood pressure and reduce heart workload.
      - Beta Blockers: Reduce heart rate and myocardial oxygen demand.
      - Calcium Channel Blockers and Statins: Manage blood pressure and lipid levels, respectively.

Lifestyle and Nutritional Therapy

  • Healthy Habits: Emphasize smoking cessation, a heart-healthy diet, weight maintenance, regular physical activity, and sufficient quality sleep (7-9 hours).

  • Dietary Adjustments:
      - NPO until stable (pain-free, no nausea); advance diet to include low salt and low-saturated fat foods.

Atrial Dysrhythmias

  • Substances Affecting Cardiac Function: Sodium, Calcium, Potassium, and Magnesium are critical in cardiovascular physiology.

Normal Sinus Rhythm

  • The standard rhythm in a healthy heart, indicating proper electrical conduction through the atria and ventricles.

Variants of Sinus Rhythm

  1. Sinus Bradycardia: A slow heart rate resulting from increased vagal tone or decreased sympathetic activity.

  2. Sinus Tachycardia: Fast heart rate resulting from increased sympathetic stimulation.

Premature Atrial Contractions (PAC)

  • Definition: Benign rhythm abnormalities arising from early electrical impulses from irritated atrial tissue.

  • Manifestations: Palpitations or a sensation that the heart "skips a beat".

  • Treatment: Monitor for dyshythmias, withholding stimulants; beta blockers may be prescribed.

First Degree Heart Block

  • Definition: A delay in the conduction of electrical signals through the right atrium to the AV node, characterized by a PR interval exceeding 0.20 seconds.

Supraventricular Tachycardia (SVT)

  • Characteristics: Narrow complex tachycardia resulting from impulses above the AV node, causing excessive atrial excitability and rapid heart rate.

  • Treatment Options: Include vagal maneuvers, IV administration of adenosine, and non-dihydropyridine calcium channel blockers like diltiazem or beta blockers like metoprolol.

Atrial Fibrillation and Flutter

  1. Atrial Fibrillation
       - Rhythm: Chaotic, exhibiting irregular heartbeats that result in abnormal filling and emptying of cardiac chambers. Potential absence of discernable P waves on ECG.
       - Complications: Increased risk for decreased cardiac output and thromboembolism.

  2. Atrial Flutter
       - Rhythm: Characterized by a sawtooth pattern, discernible P waves not corresponding to QRS complexes.
       - Complications: Similar risks for decreased cardiac output and thromboembolism.

Diagnostics for Atrial Dysrhythmias

  • Blood tests (TSH, CBC, glucose levels), ECG, and echocardiograms, including transesophageal echocardiograms to identify clots.

Treatment for Atrial Dysrhythmias

  • Procedures: Synchronized cardioversion and catheter ablation are common interventions.

  • Medications: Include beta blockers, calcium channel blockers, amiodarone, and digoxin; anticoagulants like heparin, warfarin, apixaban, dabigatran, and rivaroxaban.

Heart Failure

  • Definition: A syndrome characterized by the ventricles' inability to fill or eject blood effectively, leading to insufficient systemic circulation.

Risk Factors for Heart Failure

  • Non-modifiable: Family history, aging.

  • Modifiable: Chronic pulmonary disease, CAD, hypertension, diabetes, obesity, and alcohol abuse.

Types of Heart Failure

  1. Left-Sided Heart Failure
       - Most prevalent form; results from impaired left ventricle function, leading to pressure buildup in the pulmonary vasculature, and pulmonary congestion and edema.

  2. Right-Sided Heart Failure
       - Ineffective right ventricular pumping, leading to systemic fluid accumulation. Often a complication of left-sided heart failure, but can arise from right ventricular infarction, pulmonary embolism, or cor pulmonale.

Compensatory Mechanisms in Heart Failure

  • Neurohormonal Response: As cardiac output decreases, perceived volume reduction incites compensatory mechanisms:
      1. Sympathetic Nervous System Activation: Results in increased blood pressure and heart rate.
      2. Renin-Angiotensin-Aldosterone System Activation: Promotes sodium and water retention increasing circulation volume, peripheral vasoconstriction, and BP enhancement.
      3. Antidiuretic Hormone Release: Encourages water reabsorption, maintaining volume.

  • Dilation: Enlargement of heart chambers occurs overtime under elevated pressure in the left ventricle, initially effective but ultimately inadequate and leads to reduced cardiac output.

  • Hypertrophy: Adaptive increase in muscle mass and thickness of the heart walls. Effective initially, but over time can lead to contractility deficits, elevated oxygen demands, and dysrhythmic risks.

Congestive Heart Failure (CHF): Diagnostic Studies

  • Establish and address underlying causes of CHF through: echocardiograms (evaluate ejection fraction, heart valves, and chambers), ECG, chest x-ray, cardiopulmonary exercise tests, and heart catheterization.

  • Brain Natriuretic Peptide (BNP): Levels increase in response to pressure changes within the cardiac system; helpful for diagnosis.

CHF: Treatment Strategies

  • Pharmacologic Agents:
      - Cardiac glycosides, ACE inhibitors, ARBs, beta blockers, potassium-sparing diuretics, and other diuretics to help manage symptoms.

Nutrition

  • Adhere to a low sodium diet, restricting intake to 2 g/day.

  • Fluid restrictions may be necessary in advanced heart failure.

  • Daily weight monitoring is crucial to track fluid retention; a gain of 3 pounds over 2 days or 5 pounds over a week should prompt immediate reporting to healthcare personnel.

Critical Thinking Questions

  1. How might these disorders manifest differently in geriatric patients?

  2. Why would older patients be a higher concern when afflicted with these cardiovascular disorders?

  3. What nursing interventions are essential for managing older patients facing these disease processes?