Cardiovascular

Based on the sources provided, here is the etiology and pathophysiology of the inflammatory, valvular, and coronary artery diseases of the heart, as well as congestive heart failure, acute pulmonary edema, dysrhythmias, and pacemaker/AICD:

B. Etiology/Pathophysiology

1. Inflammatory Disease of the Heart

  • a. Pericarditis:

    • Pericarditis is an inflammation of the pericardium, the outer fibroserous sac surrounding the heart.

    • Acute pericarditis involves an increase in inflammation and fluid buildup.

    • Chronic constrictive pericarditis involves scarring that fuses the visceral and parietal pericardia together, leading to decreased ventricular filling.

    • Causes of acute pericarditis include infections (viral, bacterial), myocardial injury, cardiac trauma, and myocardial infarction (MI).

    • Causes of chronic pericarditis include tuberculosis (TB), cancer (metastases), radiation and chemotherapy, and autoimmune diseases like rheumatic fever and SLE.

  • b. Myocarditis:

    • Myocarditis is a focal or diffuse inflammation of the myocardium, the middle, muscular layer of the heart responsible for contraction.

    • The pathophysiology involves the myocardium being damaged by infectious or non-infectious causes, leading to inflammation.

    • This inflammation can cause hypertrophy or fibrosis, resulting in decreased contractility, dilation, and pinpoint hemorrhages.

    • Causes include viral and bacterial infections (like influenza and Covid), rheumatic fever, radiation therapy, chronic alcohol use, parasitic infections, and yeast.

  • c. Endocarditis:

    • Endocarditis is an infection of the heart valves, endocardium (inner layer of the heart), or cardiac prosthesis.

    • The pathophysiology involves vegetative growths on the valves, endocardial lining, or endothelial layer of blood vessels.

    • These growths can break off and embolize to the spleen, central nervous system (CNS), kidneys, extremities, and lungs.

    • Causes include invasive procedures (including dental procedures), IV drug use, previously damaged valves (rheumatic fever), piercings, and indwelling central lines like PICCs and ports.

2. Valvular

  • Valves open and close due to pressure gradients, ensuring unidirectional blood flow. Disruptions can involve stenosis (narrowing), insufficiency (regurgitation or incomplete closure), or prolapse (stretching backward).

  • a. Mitral:

    • Mitral Stenosis: Narrowing of the mitral valve between the left atrium (LA) and left ventricle (LV). This decreases blood flow from the LA to the LV, causing LA dilation and increased pressure, leading to blood backup into the lungs and potentially pulmonary hypertension and right-sided heart failure. The main cause is rheumatic heart disease (rheumatic fever).

    • Mitral Insufficiency: The mitral valve doesn't close completely, causing blood to flow back into the LA during systole. This leads to LA and LV hypertrophy and eventually left-sided heart failure. Causes include rheumatic fever, endocarditis, severe left heart failure, and uncontrolled hypertension.

    • Mitral Valve Prolapse: One or both mitral valve leaflets bulge into the LA during systole. Many individuals are asymptomatic.

  • b. Aortic:

    • Aortic Stenosis: Valve cusps become fibrotic and calcify, leading to narrowing of the aortic valve opening between the LV and the aorta. This causes LV hypertrophy, decreased cardiac output, myocardial ischemia, and eventually can lead to atrial fibrillation and right-sided heart failure. Causes include rheumatic fever, congenital malformations, and aging due to atherosclerosis and calcification.

    • Aortic Insufficiency: The aortic valve fails to close completely, allowing blood to back up into the LV during diastole. This leads to LV hypertrophy and failure, and can eventually cause right ventricular failure. Causes include rheumatic fever, endocarditis, blunt chest trauma, valve calcification, and chronic hypertension.

  • c. Tricuspid/d. Pulmonic: Dysfunctions of the tricuspid (separates the right atrium from the right ventricle) and pulmonic (separates the right ventricle from the pulmonary artery) valves are rare in adults and are usually due to congenital anomalies.

3. Coronary Artery Disease (CAD)

  • Also called Coronary Heart Disease, CAD is an occlusive disorder where the major coronary arteries supplying the myocardium are partially or completely blocked.

  • a. Angina Pectoris: Chest pain resulting from ischemia (lack of oxygen) due to a partially obstructed coronary artery.

    • Stable Angina: Often exertional and predictable, relieved by rest or nitroglycerin. It occurs when the oxygen demand of the myocardium exceeds the supply due to narrowed coronary arteries.

    • Unstable Angina: Sudden and severe chest pain that can occur at rest and is unpredictable. It is part of acute coronary syndrome and indicates a higher risk of myocardial infarction due to unstable plaque.

    • Variant Angina (Prinzmetal's angina): Caused by coronary artery spasm and can occur without evidence of CAD.

  • b. Myocardial Infarction (MI): Actual loss of cardiac muscle (necrosis) due to prolonged loss of blood flow when a coronary artery is suddenly blocked.

    • This prolonged ischemia leads to irreversible damage in the necrotic (infarction) zone.

    • The surrounding hypoxic and ischemic zone may still be viable if oxygen is restored.

    • CAD, particularly atherosclerosis with plaque rupture and thrombus formation, is the primary etiology.

4. Congestive Heart Failure (CHF)

  • Heart failure (HF) is the inability of the heart to meet the metabolic needs of the body. The pump doesn't work effectively, leading to decreased cardiac output (CO).

  • Causes can be cardiac (e.g., CHD, MI, HTN, cardiomyopathy, valvular disease) or non-cardiac (e.g., COPD, PE, severe infections, hypervolemia).

  • Two main causes are decreased contractility (e.g., after MI, cardiomyopathy) and restricted ventricular filling (e.g., tachycardia, mitral stenosis, pericarditis). Increased cellular demands (e.g., pregnancy, hyperthyroidism, fever) and volume/pressure overload (e.g., HTN, renal failure) can also contribute.

  • HF can be left-sided or right-sided. Left-sided HF is more common and often leads to blood accumulation in the left ventricle, backing into the left atrium and then the pulmonary circulation, causing pulmonary congestion. Right-sided HF often results from left-sided HF or pulmonary hypertension, causing blood to back up into the systemic venous system.

  • Diastolic HF involves a problem with the "filling" ability of the heart, while systolic HF involves a weakened heart muscle with a problem in the contraction ability.

5. Acute Pulmonary Edema

  • Acute pulmonary edema is a medical emergency often resulting from severe congestive heart failure, specifically left ventricular failure.

  • Increased pulmonary capillary pressure in the pulmonary vasculature pushes fluid into the alveoli, bronchioles, and bronchi.

  • This leads to significant respiratory distress as the patient essentially "drowns" in their own secretions.

6. Dysrhythmias

  • Cardiac arrhythmias are variations in the normal electrical pattern of the heart.

  • They range in severity from mild and asymptomatic (sinus arrhythmias) to fatal (ventricular fibrillation and asystole).

  • The severity depends on the effect on cardiac output and blood pressure.

  • Dysrhythmias occur due to disturbances in the heart's electrical conduction system, which relies on automaticity (ability to generate an impulse), conductivity (ability to pass the impulse), contractility (ability to shorten), and excitability (ability to be stimulated) of cardiac cells.

  • Examples include atrial fibrillation (multiple chaotic atrial depolarizations leading to irregular ventricular contraction and risk of thrombus), premature ventricular contractions (PVCs) (impulse starting in the ventricle), supraventricular tachycardia (SVT) (rapid heart rate originating above the ventricles), ventricular tachycardia (V-Tach) (rapid heart rate originating in the ventricles, potentially lethal), ventricular fibrillation (V-Fib) (disorganized electrical activity in the ventricles, leading to no effective cardiac output and death if untreated), and asystole (no electrical activity).

  • Factors like myocardial ischemia, MI, heart failure, electrolyte imbalances, and certain drugs can predispose to dysrhythmias.

7. Pacemaker/AICD

  • Pacemaker: Used when the heart's natural pacemaker, the sinoatrial (SA) node, is not functioning correctly. The SA node normally generates 60-100 impulses per minute. If it fails, the atrioventricular (AV) node can generate 40-60, and the Purkinje fibers 20-40. Pacemakers deliver electrical impulses to stimulate heart muscle contraction when the natural rate is too slow or irregular.

  • Automated Internal Cardiac Defibrillator (AICD): An implantable device used in patients with advanced heart failure because sudden cardiac death from dysrhythmias is common in this population. It can detect and treat life-threatening ventricular arrhythmias by delivering an electrical shock to restore a normal heart rhythm.