Cardiovascular System Review

Cardiovascular System

Normal Blood Flow

• Blood flows from the venous system into the right side of the heart.

• Preload: The amount of blood entering the right side of the heart.

• Sequence:

  • Right atrium

  • Right ventricle

  • Lungs (for oxygenation)

  • Left atrium

  • Left ventricle (the strongest pump)

  • Aorta (the first and largest artery)

• Arteries deliver oxygenated blood throughout the body.

• When oxygen is depleted, blood returns to the venous system, and the cycle repeats.

Right-Sided Heart Failure

• Blood is not properly moved forward, leading to a backward flow into the venous system.

• The blood backs up into the venous system.

• Backflow to the left side is only possible with a septal defect.

Left-Sided Heart Failure

• The heart isn't pumping blood effectively, so blood flows backward into the lungs.

• Understanding normal blood flow is crucial for comprehending heart failure.

Cardiac Output

• Cardiac output = Heart Rate \times Stroke Volume

• Decreased cardiac output leads to:

  • Inadequate perfusion

  • Brain: Altered Level of Consciousness (LOC)

  • Heart: Chest pain

  • Skin: Cold and clammy

  • Lungs: Wet lung sounds

  • Peripheral pulses: Weak or absent

  • Kidneys: Reduced urine output

• Cardiac output primarily reflects the function of the left ventricle.

• If heart rate drops (e.g., to 30 bpm), blood pressure decreases due to reduced volume.

• Compensatory mechanisms attempt to raise blood pressure to at least 90 mmHg for vital organ perfusion.

Factors Affecting Cardiac Output

• Heart Rate:

  • Extremely low heart rate reduces cardiac output.

  • Extreme tachycardia (e.g., 250 bpm) impairs ventricular filling and reduces cardiac output.

• Arrhythmias:

  • Arrhythmias are problematic when they affect cardiac output.

  • Ventricular tachycardia (V tach), ventricular fibrillation (V fib), and asystole are critical because they result in no cardiac output.

  • Atrial fibrillation (A fib) may be tolerated if cardiac output is maintained.

• When reporting rhythm changes to a doctor, include signs and symptoms of adequate cardiac output.

• When cardiac output drops, volume is reduced, leading to lower blood pressure but compensatory mechanisms should kick in to elevate blood pressure.

Chronic Stable Angina

• Decreased blood flow to the myocardium leads to ischemia, causing chest pain or pressure, usually due to coronary artery disease.

• Pain is typically brought on by exertion (low oxygen).

• Relief: Rest and/or sublingual nitroglycerin.

• Nitroglycerin:

  • Causes venous and arterial vasodilation.

  • Decreases preload and afterload, reducing workload on the heart.

  • Dilates coronary arteries, increasing blood flow to the myocardium.

  • Administer one tablet every five minutes, up to three doses.

  • Instruct patients to remove cotton from the container.

  • Do not swallow; administer sublingually for rapid absorption.

  • Store in a dark, glass bottle; keep dry and cool.

  • May or may not cause a burning or fizzing sensation.

  • Side Effect: Headache.

  • Renew every six months.

  • Expect a drop in blood pressure.

  • Never leave a patient after administering nitroglycerin because of potential instability.

• Beta Blockers:

  • Examples provided.

  • Decrease blood pressure, pulse, and myocardial contractility.

  • Reduce the workload of the heart.

• Calcium Channel Blockers:

  • Decrease blood pressure.

  • Dilate coronary arteries, improving blood flow to the heart muscle.

• Aspirin:

  • Has an antiplatelet effect.

• Patient Education:

  • Avoid isometric exercises.

  • Avoid overeating.

  • Rest frequently.

  • Avoid excess caffeine or drugs that increase heart rate.

  • Wait two hours after eating to exercise.

  • Dress warmly in cold weather; avoid temperature extremes.

  • Take nitroglycerin prophylactically.

  • Sit down before taking nitroglycerin to prevent falls.

  • Stop smoking; lose weight.

  • Decrease the workload on the heart.

Acute Coronary Syndromes

• Includes myocardial infarction (MI) and unstable angina.

• Angina becomes more unstable and unpredictable as it worsens.

• Decreased blood flow to the myocardium leads to both ischemia and necrosis.

• Pain may occur at any time, even during sleep.

• Many MIs take place in the early morning hours because REM sleep causes physiological stress.

• Rest and nitroglycerin will not relieve the pain.

• Signs and Symptoms:

  • Classic: Pressure in the chest, radiating to the left side.

  • Atypical: Pain in the left jaw, back pain (especially in women), elbow pain, indigestion, fainting.

  • Cold and clammy skin, dropping blood pressure (indicating decreased cardiac output).

  • Increased white blood cell count and temperature due to inflammation.

  • EKG changes.

  • Vomiting (due to vagus nerve stimulation from severe pain).

• Cardiac Enzymes:

  • CPK and LDH Isoenzymes are needed.

  • CKMB: Most sensitive indicator of myocardial damage, indicating heart muscle damage.

• Troponin:

  • High specificity for myocardial cell injury.

  • Always normal in non-cardiac muscle diseases.

  • Elevates sooner and stays elevated longer than other markers.

  • Detectable 3-6 hours after the onset of chest pain, lasts for 6-8 days after heart damage.

• Troponin is the most helpful marker when the patient delays seeking help.

• Treatment:

  • Aspirin should be given immediately upon arrival to the emergency department for any form of chest pain.

  • Morphine IV: Drug of choice for pain relief during an MI, also acts as a vasodilator, decreasing workload on the heart.

• MONA (for initial treatment of chest pain):

  • Morphine

  • Oxygen

  • Nitroglycerin

  • Aspirin (given in no specific order).

• Life-Threatening Arrhythmias:

  • V Fib (most common).

  • Pulseless V tach

  • Asystole

• Defibrillation is essential for V fib (early defibrillation).

• Drugs to Treat Arrhythmias:

  • Lidocaine: Sign of toxicity is any neuro change.

    • Has a very short half life.

  • Amiodarone: Side effect is hypotension and other arrhythmias.

    • Other arrhythmias lead to decreased cardiac output.

• Positioning:

  • Head-up position decreases workload on the heart and increases cardiac output.

  • Lying flat increases workload because the heart pumps uphill.

Percutaneous Coronary Intervention (PCI)

• Includes percutaneous transluminal coronary angioplasty (PTCA), angioplasty, and stents.

• Major Complications: MI and bleeding.

• Angioplasty: Can be used for single and double vessel disease.

• If problems occur, the patient will need surgery.

• Chest pain after the procedure requires immediate doctor notification because this may mean re-occlusion.

Coronary Artery Bypass Graft (CABG)

• Performed for multiple blockages or left main occlusion.

• Left main occlusion results in the death of the left ventricle due to lack of blood supply, leading to zero cardiac output and sudden death.

Cardiac Rehabilitation

• Smoking cessation.

• Stepped care plan.

• Diet changes: No fat, no salt, low cholesterol.

  • Shop the perimeter of the grocery store.

• Avoid isometrics.

• Avoid Valsalva maneuver (can stimulate the vagus nerve, causing bradycardia and potentially asystole).

  • No straining and give colase (stool softener).

• Resuming Sexual Activity Post-MI:

  • Safe when the patient can walk around the block or climb a flight of stairs without discomfort.

  • Safest time of day is morning (8 - 9 am, after being well rested).

  • Best exercise is walking.

  • Teach the signs and symptoms of heart failure, such as ankle edema, shortness of breath, weight fain and confusion.

  • If a patient becomes a cardiac cripple, counseling may be needed.