Ischemic Heart Disease and Conduction Disorders Notes

Unoxygenated blood enters the right side of the heart.
Blood enters through the superior and inferior vena cava into the right atrium.
It then passes through the tricuspid valve into the right ventricle.
From the right ventricle, blood goes through the pulmonic valve into the pulmonary artery and into the right and left lungs.
In the lungs, capillaries pick up oxygen.
Oxygenated blood flows through the pulmonary veins into the left atrium.
Blood passes through the mitral valve into the left ventricle.
Finally, blood goes through the aortic valve into the aortic arch and out into the body.

Coronary arteries supply oxygenated blood to the heart muscle.
The heart muscle is perfused during diastole (rest).
Main coronary arteries include the right coronary artery, the left main coronary artery, the left anterior descending artery, and the circumflex artery.
Atherosclerotic changes can occur in these coronary vessels, similar to what happens in peripheral arteries.
Pressure in coronary arteries is lower, making them prone to atherosclerotic plaque formation.
The heart requires oxygenated blood delivery and waste product removal.
Atherosclerotic plaque can accumulate in coronary arteries.

Electrical conduction is essential for the heart to contract, relax, and propel blood.
Cells depolarize and repolarize in a coordinated sequence to produce a rhythm.
Electrical impulses originate in the SA node in the right atrium.
These impulses cause depolarization of the atrial cells, then travel to the AV node.
From the AV node, impulses go down through the bundle of His and Purkinje fibers, leading to complete heart depolarization and repolarization.

An ECG measures and records the heart's electrical activity.
Cardiac impulses normally start at the SA node and stimulate other cardiac cells as they travel through the heart muscle.
Electrodes on the chest wall record electrical activity, producing a waveform.
The waveform is labeled with letters (P, QRS, T) to represent electrical conduction, depolarization, and repolarization.
- P wave: Represents depolarization of the atria.
- QRS complex: Represents depolarization of the ventricles.
- T wave: Represents repolarization of the ventricles.
- Repolarization of the atria occurs during the QRS complex but is not visible on the waveform.

Ischemia: Lack of circulation to the heart muscle.
- Can be temporary with restored perfusion.
- Prolonged ischemia can lead to myocardial infarction (heart attack), which involves cardiac tissue death.
Terms associated with ischemic heart disease: stable angina, acute coronary syndrome, unstable angina, and myocardial infarction.

Squeezing, tight chest pain due to inadequate blood flow to the myocardium.
Can be a chronic condition managed with medication or lifestyle modifications.
- Can be stable or unstable (emergency).
Symptoms may include radiating pain to the neck, jaw, upper abdomen, or arms, as well as dyspnea (shortness of breath), diaphoresis (sweating), pallor (pale skin), or weakness.

New onset of pain or progression of stable angina.
Pain is not relieved by rest or usual medications.
May feel different from usual chest pain episodes.
Requires emergency care to determine if there is a partial or complete coronary artery occlusion.

Complete occlusion of a coronary artery due to a clot or plaque rupture.
Prolonged ischemia leads to irreversible tissue death of the heart muscle.
MI is a leading cause of death in the U.S.
- Approximately 1.5 million Americans have an MI each year, with 500,000 deaths.
- Half of the deaths (250,000) occur before reaching a hospital.

Symptoms include retrosternal chest discomfort (pressure, choking, squeezing, heaviness).
Classic description: crushing pain on the left side of the chest radiating to the left shoulder and arm.
- Pain can also radiate to the jaw, neck, back, right arm, or epigastric region.
Signs evaluated by nurses include ECG changes and biomarkers in lab work.
- Biomarkers such as CKMB (CPKMB) and troponin indicate tissue death.
- Pallor (pale skin) may also be present.

Rhythm disturbances (dysrhythmias):
- AV or heart blocks
- Atrial fibrillation
- Premature ventricular contractions (PVCs)
- Lethal dysrhythmias: ventricular tachycardia (V-tach) and ventricular fibrillation (V-fib)
Papillary muscle rupture: affects valve contractility.
Thromboembolism: thrombus breaks loose and travels to other areas.
Ventricular aneurysm: weakening of the ventricular wall, which can rupture.
Pericarditis: inflammation of the pericardial sac.
Heart failure: weakened contractility.
Cardiogenic shock: severe heart failure leading to poor perfusion and life-threatening conditions.

Caused by bacterial or fungal pathogens.
Results in vegetation or growth on the endothelium and heart valves.
Emboli from valves can break loose and travel to other areas, causing occlusions, ischemia, and infarction in other organs.
Causes damage to heart valves and can create emboli.

Inflammation of the pericardium or pericardial sac.
Inflammatory response causes capillaries to become hyperpermeable.
Fluid accumulation leads to pericardial effusion.
Excess fluid restricts heart motion, decreasing stroke volume and cardiac output.
Cardiac tamponade: extra fluid compresses the heart, decreasing blood pressure and tissue perfusion.