EMT Cardiology and Circulatory Review

Sympathetic Nervous System and Beta Receptors

• Beta Receptors Categorization:     * Beta 1 Receptors: These are primarily located in the heart. A common mnemonic to remember this is that humans have one heart, so Beta 1 affects the heart.     * Beta 2 Receptors: These are primarily located in the lungs. Humans have two lungs, so Beta 2 affects the lungs. Activation of these receptors causes bronchodilation, allowing more oxygen and air to enter the body.

• Sympathomimetic Medications:     * These are medications given at the basic EMT level that mimic the effects of the sympathetic nervous system.     * Epinephrine: Affects the sympathetic nervous system to increase heart rate and blood pressure.     * Albuterol: Primarily targets Beta 2 receptors to induce bronchodilation.

Myocardium and Cellular Respiration

• Definition of Myocardium: Broken down into "myo" (muscle) and "cardium" (heart), meaning the heart muscle. It requires a continuous, uninterrupted supply of oxygen and nutrients to pump blood efficiently.

• Aerobic Respiration:     * Definition: The process of breaking down glucose to create energy in the presence of oxygen.     * Output: Typically produces a large amount of energy, approximately $36$ to $38$ molecules of ATP (Adenosine Triphosphate).     * Byproducts: Water ($H_2O$) and Carbon Dioxide ($CO_2$). Both are easily handled and expelled by the body through exhalation.

• Anaerobic Respiration:     * Definition: The breakdown of glucose into energy without the presence or use of oxygen.     * Output: Significantly less efficient, producing only $2$ molecules of ATP.     * Byproducts: Lactic acid. This byproduct affects the pH of cells and the body, leading to an acidic state.     * Implications: Inability to get oxygen to cells leads to a pH shift (acidosis), which eventually causes cellular death. This is often the cause of soreness after a workout but is life-threatening when it occurs in vital organs.

Cardiac Output and Compensation

• The Cardiac Output Equation: $CO = HR \times SV$     * $CO$ (Cardiac Output): The volume of blood passing through the heart (ejected) in one minute.     * $HR$ (Heart Rate): The number of times the heart beats per minute.     * $SV$ (Stroke Volume): The amount of blood pushed out of the pump with each individual contraction.

• Homeostasis and Compensation:     * The body seeks to maintain a static cardiac output to meet oxygen and glucose demands.     * Example Scenario: In a trauma case (e.g., a gunshot wound leading to heavy bleeding), blood volume drops, causing a decrease in stroke volume ($SV$). To maintain the same cardiac output ($CO$), the body compensates by increasing the heart rate ($HR$).     * Short-term Compensation: Primarily achieved through increasing heart rate or constricting arteries and veins (decreasing the size of the "tubing").

Anatomy of the Circulatory System

• The Vascular Tree Analogy:     * The Aorta is the "trunk" of the tree, approximately the size of a garden hose.     * Arteries are the large branches.     * Arterioles are the smaller branches.     * Capillaries are the "leaves." This is the level where gas exchange occurs. Oxygen leaves the red blood cells to enter tissue cells, and $CO_2$ is picked up for expulsion.

• Venous Return: After the capillaries, blood travels through venules (small) then into veins (larger) back toward the heart.

• Coronary Arteries: These arteries surround the exterior of the heart. Despite the heart being a pump for the whole body, the myocardium itself must be fed by oxygenated blood via these specific vessels. Obstructions here lead to "having a coronary" or a heart attack.

• Major Arteries for Pulse Checks:     * Femoral Artery: Located in the groin.     * Brachial Artery: Located in the upper arm.     * Radial Artery: Located at the wrist.     * Carotid Artery: Located in the neck.

• Composition of Blood:     * Red Blood Cells (RBCs): Carry oxygen.     * White Blood Cells (WBCs): Fight infection.     * Platelets: Responsible for clotting.     * Plasma: The liquid medium carrying sugars, electrolytes, and other necessities.

Blood Pressure and Pulse Dynamics

• Systolic Blood Pressure: The "top number." It represents the maximum pressure in the system when the heart contracts and pushes a pulse wave through the arteries.

• Diastolic Blood Pressure: The "bottom number." It represents the pressure in the system when the heart is at rest, refilling between beats.

• Pulse Assessment (Field Estimates): While not a hard rule, the presence of certain pulses often suggests minimum systolic blood pressure thresholds:     * Radial Pulse: Strong presence usually suggests a systolic pressure above $90\,mmHg$.     * Brachial Pulse: Suggests a systolic pressure around $70\,mmHg$.     * Carotid Pulse: Suggests a systolic pressure around $40$ to $50\,mmHg$.

• Central vs. Peripheral Pulses:     * Central: Carotid, Femoral (near the body's trunk).     * Peripheral: Radial, Brachial, Dorsalis Pedis (Pedal pulse).

Pathophysiology of Cardiac Distress

• Ischemia: A decrease in blood flow to the heart tissue, causing the heart to send pain signals. It is often the precursor to tissue death.

• Infarction: Actual cellular death of the heart muscle. A Myocardial Infarction (MI) is the medical term for a heart attack. Dead heart cells cannot regenerate; "Time is Muscle."

• Atherosclerosis: The buildup of plaque within an artery, narrowing the "pipe" and decreasing blood flow. This creates "pinch points" where clots can easily lodge.

• Thromboembolism: A blood clot floating through the blood vessels. This is a major concern in patients with Atrial Fibrillation (AFib), as their hearts tend to produce clots that can lead to AMI, pulmonary embolisms, or strokes.

Acute Coronary Syndrome (ACS)

• Angina Pectoris:     * Occurs when oxygen demand exceeds the supply. Typically caused by narrowed arteries during exertion.     * Stable Angina: Triggered by exercise/exertion; relieved by rest or Nitroglycerin.     * Unstable Angina: Does not stabilize with rest; carries a higher risk and presents similarly to an AMI.     * Pain Description: Often described as a crushing or squeezing sensation in the chest.

• Acute Myocardial Infarction (AMI):     * Actual death of myocardium. Does not always require exertion to begin and is not typically relieved by rest or Nitroglycerin.     * Treatment Goals: Restoration of blood flow via Thrombolytics (clot-busting drugs) or Angioplasty (catheterization with a balloon and stent).

Signs, Symptoms, and Patient Presentations

• Classic vs. Atypical Symptoms:     * Traditional (Men): Heavy pressure ("elephant on chest"), pain radiating to the left arm, jaw, or neck, shortness of breath, and nausea.     * Atypical (Women/Elderly): May describe back pain between the shoulder blades, epigastric pain, or simply "heaviness" or weakness in an arm (e.g., the case of the 90-year-old woman).

• Significant Physical Findings:     * Diaphoresis: Cold, clammy sweat during rest is a high-index indicator of cardiac issues.     * Syncope: Fainting suggests a major disruption in cardiac output.     * Pink Frothy Sputum: A very late, critical sign of severe heart failure/pulmonary edema ("circling the drain").     * Impending Doom: A psychological feeling where the patient explicitly states they are going to die (e.g., the dementia patient who predicted his death accurately).

• Pulse Abnormalities:     * Tachycardia: Heart rate above $100\,bpm$.     * Bradycardia: Heart rate below $60\,bpm$.     * Irregular Rhythms: Can be "regularly irregular" (patterned extra beats like PVCs) or "irregularly irregular" (chaotic like V-Fib).

Cardiac Rhythms and Defibrillation

• Shockable Rhythms (AED Awareness):     * Ventricular Tachycardia (V-Tach): Organized but lethal rhythm from the ventricles; may or may not have a pulse.     * Ventricular Fibrillation (V-Fib): Chaotic, quivering state with no organized contraction; never has a pulse.

• Non-Shockable Rhythms:     * Asystole: Flat line; no electrical activity. Usually follows a long period of ischemia/V-Fib.     * Pulseless Electrical Activity (PEA): The electrical system is firing, but the mechanical pump is not responding.

• Defibrillation Mechanism: It is NOT "jump-starting" the heart (as depicted by George Clooney in General Hospital). It is a "hard boot" that stops all electrical activity simultaneously so the natural pacemaker (SA Node) can hopefully resume control.

Congestive Heart Failure (CHF)

• Right-Sided Heart Failure:     * Backs up into the body.     * Symptom: Dependent Edema (swelling in the legs). In severe cases, "weeping edema" or "pitting edema" (where a finger divot remains) occurs.     * Common Meds: Lasix (furosemide) or "water pills."

• Left-Sided Heart Failure:     * Backs up into the lungs.     * Symptom: Pulmonary Edema, recognized by crackles or rales in the lung bases.     * Paroxysmal Nocturnal Dyspnea: Inability to lay flat; patients often sleep propped on pillows or in recliners to avoid drowning in their own fluid.

Hypertensive Emergencies

• Threshold: Systolic pressure acutely at or above $180\,mmHg$.

• Symptoms: Sudden severe headache, "bounding" pulse (feeling like a kangaroo in the wrist), tinnitus (ringing in ears), and visual disturbances (spots).

• Complications: Stroke or a Dissecting Aortic Aneurysm (tearing sensation in the chest or back).

• Abdominal Aortic Aneurysm (AAA): May present as a "ripping" back pain and a pulsatile mass in the abdomen. Palpate very gently.

EMT Field Management and Pharmacology

• Aspirin:     * Dose: $324\,mg$ (usually four $81\,mg$ baby aspirins).     * Action: Antiplatelet aggregator (makes platelets "slippery") to prevent clots from growing larger.

• Nitroglycerin:     * Dose: $0.4\,mg$ sublingual (tablet or spray). Max $3$ doses per National Registry.     * Action: Vasodilator; decreases workload of the heart.     * Contraindications: Systolic BP < 100\,mmHg, Head injury, or use of Erectile Dysfunction (ED) meds (Viagra, Cialis) within $24$-$48$ hours.     * Safety: Always wear gloves (it is transdermal).

• CPAP: Used for pulmonary edema to push fluid out of the alveoli via positive pressure.

ECG Lead Placement and Special Devices

• Limb Leads (4-Lead):     * White (RA): Right Arm / Right Shoulder.     * Black (LA): Left Arm / Left Shoulder.     * Green (RL): Right Leg / Lower Abdomen.     * Red (LL): Left Leg / Lower Abdomen.     * Mnemonic: White on right, smoke (black) over fire (red), clouds (white) over grass (green).

• Implanted Devices:     * Pacemaker: Regulates heart rate (usually set to $60$-$65\,bpm$). Avoid placing AED pads directly over the bulge.     * AICD (Implanted Defibrillator): Automatically shocks V-Tach/V-Fib. Safe to touch the patient during the shock.     * LVAD (Left Ventricular Assist Device): A mechanical pump. Patients will have no palpable pulse and a constant mechanical whirring sound in the chest. Always transport their external battery packs.