Study Stack - Cardio Master Notes Table Review

Cardiac Anatomy and Physiology Fundamentals

The cardiology curriculum provided is based on the U.S. Department of Transportation National Standard Curriculum. A cardiac workup is indicated for any patient presenting with a pulse and a clinical problem extending from the hips to the head, typically involving a 12/15 Lead ECG.

Key anatomical and physiological definitions include:

Anastomosis: The communication or connection between two or more vessels.
Collateral Circulation: The communication and connection between one or more vessels providing alternative pathways for blood flow.
Poiseuille's Law: States that blood flow through a vessel is directly proportional to the radius of the vessel to the fourth power.
Chordae Tendineae: Fibrous cords that anchor the leaflets of the bicuspid (mitral) and tricuspid valves. These are attached to the Papillary muscles within the ventricles.
Semi-lunar Valves: Refers specifically to the Aortic valve and the Pulmonic valve.
Pectinate Muscles (musculi pectinate): Comb-like parallel ridges of muscle found in the anterior part of the right atrium that increase contraction power without adding significant weight to the heart.
Foramen Ovale: A hole in the atrial septum that serves as part of the fetal blood circulation.

The Cardiac Cycle and Hemodynamics

The cardiac cycle describes the sequence of events occurring between the end of one heart contraction and the end of the next. The most common cause of death in patients experiencing chest pain/myocardial infarction is a lethal heart dysrhythmia.

Phases of the Cardiac Cycle

Diastole: The first phase of the cardiac cycle where the heart relaxes and the ventricles fill with blood. During this phase, the pulmonic and aortic valves close (S2, Dub), and the coronary arteries are perfused.
Systole: The second phase where the myocardium contracts and the heart pumps blood. This involves the closing of the tricuspid and bicuspid valves (S1, Lub).

Hemodynamic Equations and Variables

Ejection Fraction (EF): The percentage of blood pumped from the ventricles compared to the total amount remaining at the end of diastole.
- Equation: $\text{Amount of blood pumped out} \div \text{Total amount of blood in the ventricle}$
- Example: $100\,mL - 40\,mL = 60-70\%$
- Normal range: $60-70\%$
- Heart Failure: < 45\%
Preload: The volume or pressure of blood in the ventricles at the end of diastole (End Diastolic Volume). Increasing preload via IV fluids generally increases the Ejection Fraction.
Afterload: The resistance the heart must pump against to open the aortic valve. It represents the ventricular workload and can be adjusted with Vasoconstrictors or Vasodilators.
Contractility: The ability of muscle cells to shorten. The ion primarily responsible for contractility is Calcium. It can be increased via medications.
Stroke Volume (SV): The amount of blood pumped out in one contraction.
- Average SV: Between $70\,mL$ and $100\,mL$ (average $70\,mL$ ).
- Influencing Factors: Preload, Afterload, and Contractility.
Cardiac Output (CO): The volume of blood pumped out in one minute.
- Equation: $SV \times HR$
Blood Pressure (BP) Equation: $HR \times SV \times \text{Systemic Vascular Resistance (SVR)}$
Starling Law of the Heart: Known as the "rubber band effect"; the more the myocardium is stretched, the more forceful the subsequent contraction will be (up to a certain point).

Physiological Terminology and Peptides

Chronotropy: Refers to cardiac heart rate and the speed of electrical impulses from the SA node.
Inotropy: Refers to the force of myocardial contraction.
Dromotropy: Refers to the conduction velocity or speed of electrical impulses traveling through conduction pathways.
ANP (Atrial Natriuretic Peptides): Manufactured, stored, and released by atrial muscle cells in response to atrial distention and stimulation.
BNP (Brain Natriuretic Peptide): Secreted by the ventricles in response to excessive stretching of the ventricular myocytes.

Cardiac Electrophysiology and the Action Potential

Cardiac cells maintain specific electrical potentials and follow distinct phases during an action potential.

Cardiac Contractile Cells

Resting Potential: $-90\,mV$
Action Potential Threshold: $-85\,mV$
Phase 0: Depolarization; caused by fast Sodium channels opening or a rapid influx of sodium.
Phase 2: Calcium enters the cell.
Phase 3: Repolarization; caused by the efflux of Potassium.
Phase 4: Sodium/Potassium pumps actively move ions back to their resting locations.

Autorhythmic (Pacemaker) Cells

Sodium: Gets the cell from resting potential to action potential.
Phase 0: Depolarization; caused by a rapid influx of Calcium.
Phase 3: Repolarization; caused by the efflux of Potassium.

Electrocardiography (ECG) Interpretation

Normal ECG Parameters

P Wave: Nice and round.
- Limb leads: Maximum amplitude $2.5\,mm$ , $0.25\,mV$ , or $2.5\,\text{small boxes}$ .
- Precordial (chest) leads: Maximum amplitude $3\,mm$ or $0.15\,mV$ .
PRI (P-R Interval): Duration between $0.12$ and $0.20\,second$ . A PRI longer than $0.20\,second$ indicates the impulse is held too long at the AV node.
QRS Complex: Duration between $0.04$ and $0.12\,seconds$ ( $1-3\,\text{small boxes}$ ).
T Wave:
- Limb leads: Maximum amplitude $5\,mm$ .
- Chest leads: Maximum amplitude $10\,mm$ .
ECG Paper: One small vertical box represents $1\,mm$ .
Rate Measurement (Regular Rhythms): $HR = 1500 \div \# \text{small boxes between R intervals}$ .

Lead Anatomy

Septal (Middle): Leads V1 and V2.
Anterior: Leads V3 and V4.
Inferior: Leads II, III, and aVF.
Higher Left Lateral: Leads I and aVL.
Lower Left Lateral: Leads V5 and V6.

Coronary Artery Perfusion

LAD (Left Anterior Descending): Feeds the anterior wall of the left ventricle; known as the Widow maker.
RCA (Right Coronary Artery): Feeds the inferior wall of the heart.
LCX (Left Circumflex): Feeds the left lateral wall.
LMCA (Left Main Coronary Artery): A blockage here results in the entire left ventricle losing its blood supply.

Trauma Systems and Surveillance

Registry: The health care surveillance process put in place for trauma systems.
Surveillance Process: Includes Data Collection, Data Analysis, Data Interpretation, and Dissemination.
Surveillance Definition: The collection of data to identify the existence, significance, and characteristics of a disease process.
Trauma Triage Criteria: Standards established by medical direction to determine which patients require urgent transport to a trauma center.
Level 2 Facility: Commits resources to common trauma emergencies with 24/7 surgical capability.
Index of Suspicion: The mental summation of anticipated injuries based on event analysis.
Transport Decision Tree Elements: Glasgow Coma Scale, anatomy of injury, and physical findings.
The Golden Period: The concept reminding EMS to hasten care and delivery to the Emergency Department.

Hemorrhage and Shock

Shock is considered the ultimate killer of trauma victims. Penetrating trauma occurs when an object enters the body and exchanges energy directly with human tissue.

Classes of Hemorrhage

Class 1: Initial $15\% \text{ loss } (750\,mL)$ .
Class 2: Compensated $15-30\% \text{ loss } (750\,mL - 1500\,mL)$ . Patient is anxious/restless with cool, clammy skin. Pulse pressure will noticeably narrow.
Class 3: Decompensated $30-40\% \text{ loss } (1500\,mL - 2000\,mL)$ .
Class 4: Irreversible >40\% \text{ loss } (>2000\,mL).

Cardiovascular and Coagulation Notes

Capacitance System: Refers to the Veins.
Arteries: Consist of three layers (Tunica Adventitia Extera, Tunica Media, Tunica Intima). They carry blood from the heart to body tissues.
Coagulopathy: A condition where the blood's ability to clot is impaired.
Clotting Process:
1. Vascular phase (smooth muscle contracts).
2. Platelet phase (platelets and collagen aggregate).
3. Coagulation phase (fibrin blood clot).
Beck's Triad: Distended Jugular Veins, Distant (Muffled) Heart Sounds, and Decreased arterial blood pressure (Hypotension). Indicates Pericardial Tamponade.
Mean Arterial Pressure (MAP): The correct measurement for peripheral vascular resistance.
CUPS Acronym: Critical (Cardiac/Respiratory arrest), Unstable (Life issues), Potentially Unstable (High risk of deteriorating), Stable (No immediate threat to life).
Waddell's Triad: Ankle injuries, Abdominal/chest injuries, Head injury, and Pelvis/Femur injury.

Specialized Traumatic Conditions

Crush Syndrome and Hyperkalemia

Crush Syndrome: Usually occurs when a body part is trapped/crushed for longer than $4\,hours$ .
Rhabdomyolysis: Leads to elevated potassium levels (Hyperkalemia).
Hyperkalemia S&S: Peaked T waves on ECG, pain, firm/tense limb, loss of muscle function, swelling, low BP, and dark/bloody urine.
Treatment:
- Calcium Chloride: First-line medication ( $500-1000\,mg$ slow IV over $3\,minutes$ ). It temporarily blocks potassium to prevent arrhythmias.
- Sodium Bicarbonate: Also used for suspected hyperkalemia.

Compartment Syndrome

Most common location: Distal leg, anterior compartment.
The 6 P's:
1. Pain (The first P)
2. Pins and needles (Paresthesia)
3. Pallor
4. Paralysis
5. Pulselessness
6. Pretty cold (Poikilothermia)

Notable Clinical Findings

Venous Bleeding: Typically dark red and "blowing" (oozing).
Tourniquets: Use can lead to the accumulation of lactic acid, potassium, and anaerobic metabolites.
Blood Volume: In infants/young children, it is proportionally $20\% \text{ greater}$ than in adults.
Head Injuries: Expiratory $CO_2$ levels in intubated head-injured patients should not drop below $30$ .
Atrial Fibrillation: The most common heart problem most people eventually develop. Cardioversion or pharma intervention is usually required if the ventricular rate is above $150\,bpm$ .
Sinus Rhythms:
- Sinus Arrest: SA node fails; multiple dropped beats; cadence is thrown off upon restart.
- Sinus Pause: SA node fails; only one dropped beat; cadence is thrown off upon restart.
- Sinus Block: Electrical impulse fails to leave SA node; multiple dropped beats; cadence remains on track upon restart.