DMS 100 Cardiac Lecture 1 of 2
Introduction to Cardiac Scanning
Welcome to the DMS Program
Instructor: Professor Jackie Turner, specializing in cardiovascular/echo courses.
Objective: Introduce cardiac scanning over two lectures.
Key Differences in Cardiac Sonography
Orientation (relation to heart vs. body) and sonographic terms differ from general imaging.
Emphasis on real-time clips and images due to the heart being a real-time, beating structure.
Shift from acquiring still frames (freezing and capturing) to real-time loops in this module, performed by cardiovascular sonographers.
Heart Evaluation Focus
Evaluation of cardiac anatomy.
Assessment of physiology: how well blood flows through the heart.
Correlation with ECG (electrocardiogram) findings.
Core Chapter Objectives
Recognize Normal Cardiac Anatomy:
Identify normal cardiac anatomy and surrounding structures within ultrasound images.
Describe Cardiac Physiology:
Explain the heart's function and blood flow through a normal anatomical and physiological heart.
Recognize Circulatory System Components:
Review the components of the circulatory system (should be a review from A&P 1 & 2).
Users are encouraged to pre-read or review A&P cardiovascular sections for detailed information.
Identify Basic Cardiac Rhythms:
Recognize basic cardiac rhythms that are associated with echocardiographic findings.
Introduce Cardiac Imaging in Scan Lab:
Practical introduction to cardiac imaging techniques in the scan lab.
Overview of Cardiac Anatomy & Physiology
Heart Chambers
Four chambers: two upper atria, two lower ventricles.
Septa:
Interatrial septum: separates the two atria.
Interventricular septum: partition between the two ventricles.
Heart Valves
Atrioventricular (AV) Valves (between atria and ventricles):
Right side: Tricuspid valve (3 leaflets or cusps) connects the right atrium and right ventricle.
Left side: Bicuspid valve (also called mitral valve due to resemblance to a Bishop's two-sided mitre or hat) connects the left atrium and left ventricle.
Semilunar (SL) Valves (at the opening of great vessels):
Pulmonary valve: at the opening of the pulmonary trunk.
Aortic valve: at the opening of the aorta.
Named semilunar due to their crescent moon shape.
Valve Support Structure
Leaflets of AV valves are connected to fibrous tissue called chordae tendineae.
Chordae tendineae are attached to papillary muscles.
Contraction and relaxation of these muscles cause the valves to open and close.
Heart Sounds
The characteristic "double-up" sound of the heartbeat is produced during the closing of the heart valves.
Heart Wall Thickness
Varies with function.
Atria walls: thinner, as blood is pumped only into adjacent ventricles.
Ventricle walls:
Left ventricle (LV): thicker than the right ventricle (RV) because it pumps blood a greater distance at higher pressure.
Specialized Cardiac Tissue (Electrical Conduction System)
Components: Sinoatrial (SA) node, Atrioventricular (AV) node, Bundle of His, and Purkinje fibers.
Properties: These fibers are auto-excitable, meaning they can generate electrical activity without external stimuli.
Function: This auto-excitability makes the heart beat continuously.
Interaction of Electrical and Mechanical Components
ECG (electrical component): represents the electrical activity (conduction system) of the cardiac cycle.
Echocardiogram (mechanical component): shows the actual working part of the cardiac cycle (systole and diastole), including muscle contraction, relaxation, and valve motion.
Cardiac Anatomy: A Detailed Look
Importance of Relational Anatomy
Essential for successful sonographers to understand and recognize internal and external structures.
Graphic representation shows electrical activity traveling down the Bundle of His into the Purkinje fibers.
Internal Structures
Right Heart: Tricuspid valve (three leaflets). RAT
Left Heart: Mitral valve (bicuspid) LAB
Valves (viewed from apex up):
Pulmonary valve (or pulmonic valve): takes blood from the right ventricle to the lungs.
Aortic valve: tucked away behind the pulmonary valve.
External Structures
Internal jugular vein.
Carotid arteries (lateral to the thyroid, derived directly from the heart).
Great vessels: Aorta.
Heart positioned between the two lungs, protected by the rib cage.
Intercostal spaces: crucial for transducer placement to get the ultrasound beam to the heart, avoiding bone/ribs which cause channeling.
Diaphragm: sits inferior to the heart, dividing the thoracic cavity from the abdominal cavity.
Echocardiography Focus
Main function is to image internal structures: chambers, supporting apparatus of each valve, valves themselves, and blood flow through chambers and great vessels.
Coronary arteries: not a primary goal; usually seen best with MRI, though dilatation can sometimes be seen on echo.
Major Internal Structures and Blood Flow:
Inferior Vena Cava (IVC): brings deoxygenated blood from lower body/extremities back to the heart.
Superior Vena Cava (SVC): brings deoxygenated blood from upper body/extremities (including brain) back to the heart.
Right Atrium (RA).
Tricuspid valve: with chordae and papillary muscles.
Right Ventricle (RV).
Pulmonic valve (trileaflet).
Main Pulmonary Artery (MPA): divides into pulmonary arteries (four total) that go to the lungs.
Pulmonary veins: bring oxygenated blood back from the lungs (two on left, two on right) to the left atrium.
Left Atrium (LA).
Mitral valve.
Left Ventricle (LV).
Aortic valve.
Aorta: takes oxygenated blood to the body.
Anatomy Review: Diagrams and Sonographic Correlation
Identifying Chambers in Diagrams:
Diagram shows: 1. Right Atria, 2. Right Ventricle, 3. Left Atria, 4. Left Ventricle.
Understanding relationship between chambers is critical for interpreting sonographic images, as left and right sides can look similar.
Transverse (Short Axis) Views:
Cross-sections of the heart, slicing horizontally instead of longitudinally.
Allows visualization of valves at different levels (more superiorly at the base near great vessels).
Order of valves from superior to inferior (not always to scale in schematics):
Pulmonic valve: most superior (often tucked behind aorta).
Aortic valve: sits a little inferior to pulmonic.
Mitral valve: on the left side, separates LA and LV.
Tricuspid valve: sits most inferiorly (mitral and aortic valves are not straight across from tricuspid).
ASK QUESTION ON THISSSSS
Note on Schematics: some diagrams may not be precisely to scale, which requires careful interpretation.
Muscle Layers of the Heart
Three primary layers (from outer to inner):
Pericardium: outermost layer, fibrous, protective shell.
Sonographically: presents very hyperechoic/echogenic, similar to the diaphragm in composition.
Myocardium: middle layer, "meat of the heart," muscle responsible for contraction and expansion (most work).
Endocardium: innermost layer, delicate, divider between blood and heart tissue.
The pericardium itself has several layers (not detailed here).
Valve and Chamber Movement
Schematic demonstrating how valves open/close and how heart chambers move during systole and diastole, in response to electrical impulses.
Gross Anatomy and Heart Position in the Chest
Importance of Depth and Position
Gross anatomy helps understand how deep the heart resides within the chest wall.
Cadaver heart: shows anterior wall, posterior wall, apex (generally leftward).
Heart's Oblique Position
The heart sits in a left anterior oblique position in the chest, not straight up and down.
The right side of the heart is more anterior than the left side.
Sequential Slicing (2 cm per slice demonstration)
First slice: Reveals posterior wall, right atria (RA), superior vena cava (SVC), and a bit of the tricuspid valve.
Due to the heart's anterior oblique position, more of the right heart chambers are seen from an anterior approach.
Second slice: Shows more of the great vessels, right heart (tricuspid valve, right ventricle), and a small portion of the left ventricle (LV).
The left atria (LA) is tucked away posteriorly and not seen much yet.
Third slice: Reveals more of the LA and LV, the interventricular septum, chordae, papillary muscles anchoring the tricuspid valve, and the RA.
The RA appears smaller than the LV, reflecting the LV's role as the main pumping chamber with thicker walls.
Fourth slice: Starts to look more like a four-chamber heart, with great vessels (SVC, pulmonary veins, possible division of aorta and main pulmonary artery), RA, RV, interventricular septum, LV, and LA.
The interatrial septum is tucked behind.
Final slice (after cutting away great vessels): Shows the full LA, mitral valve (with papillary muscles and chordae), interventricular septum, and RA.
Depth for Imaging
Approximately 12-16 cm from the scanline for parasternal window.
Approximately 16-20 cm from the scanline for apical window (to reach the base of the heart).
Comparative Analysis of Views (ASK IF THIS IS WHAT A TRANSVERSE VIEW WOULD LOOK LIKE 24:24)
Comparison of gross anatomy, anatomical renditions, and sonographic images.
Short axis (transverse) cross-sectional cuts of the heart.
Anatomical view shows left atrial appendage (blood reservoir lateral to LA), right atrial appendage.
Mitral valve (only two-leaflet valve).
Aortic valve (superior to mitral, three cusps: right coronary, non-coronary, left coronary).
Pulmonary trunk.
Tricuspid valve.
View is from the base looking down into the heart.
Terminology Distinction: "Cusps" for semilunar valves (pulmonic, aortic) due to small pockets for blood reservoir; "leaflets" for atrioventricular valves (mitral, tricuspid).
Anatomic drawing clarifies that semilunar valves are closed during diastole (ventricles resting), while AV valves are open (blood flows from atria to ventricles).
Mitral valve in transverse/short axis looks like a "fish mouth" (or bass fish mouth) due to its two cusps.
Sonographic Image (Mirror Image):
Due to flipping, the sonographic image of the transverse view differs from anatomical drawings.
Structures seen: tricuspid valve, right atrium, aortic valve (three cusps), right ventricular outflow tract (leading to pulmonic valve and main pulmonary artery), left atrium (below aortic valve).
Apical Window
Location: Down at the apex of the heart, out laterally, different from the parasternal window (near the sternum).
Cadaver View from Apical Approach:
Lungs pulled away, revealing mediastinum and fibrous, yellowish pericardium.
Structures visible: right inferior vena cava (RIVC), right superior vena cava (RSVC) entering RA, tricuspid valve, RV (more anterior), main pulmonary trunk (with pulmonic valve).
Left side is more posterior and often not fully seen in this cut.
Great vessels: Aorta (hollow in cadaver), main pulmonary artery/trunk.
Sonographic View from Apical Window: 28:57
The apex appears superior in the image because it is the first structure intersected by the ultrasound beam.
Ventricles are seen before the atria (near field vs. far field).
Structures: Right Ventricle (RV), Right Atrium (RA), Tricuspid valve, Left Ventricle (LV), Mitral valve, Left Atrium (LA).
Myocardium, bright pericardium, and thin endocardium are visible.
Cardiac Physiology: Function and Electrical Conduction
Definition:
Study of the healthy, unimpaired function of the heart, encompassing blood flow, myocardial structure, and the electrical conduction system.
ECG (Electrocardiogram): The Electrical Component
Represents the electrical activity.
Normal cardiac rhythm: Evenly spaced QRS, T, and P waves.
Timing between cardiac cycles should be equivocal; uneven spacing indicates arrhythmia.
Heart's Energy and Oxygen Needs
Like all muscles, the heart requires energy and oxygen.
Electrical stimuli from SA and AV nodes "shock" the myocardium, causing contraction (systole) and relaxation (diastole).
QRS complex corresponds to systole; T and P waves are part of diastole (resting/filling).
Echocardiogram: The Mechanical Component
Represents the physical contraction and relaxation of the muscle and the motion of the valves.
Mechanical activity is a direct result of the electrical system's actions on the heart.
Allows observation of changes in cardiac pressures, valve opening/closing, and blood volume ejected with each heartbeat.
The Circulatory System: Blood Flow Pathway
Heart's Role:
Pumps blood throughout the body, controls heart rate, and maintains blood pressure.
Analogized as a house with walls, rooms, doors (valves), plumbing (vessels), and an electrical system.
Pathway of a Drop of Blood (Deoxygenated Blood to Lungs):
Returns from Brain/Upper Body via SVC; from Lower Body via IVC.
Both SVC/IVC empty into the Right Atrium (RA).
Passes through the Tricuspid valve into the Right Ventricle (RV).
Note: Pressures are lower in the right heart; RV walls are less thick as its purpose is to pump blood to the lungs.
Passes through the Pulmonic valve into the Main Pulmonary Artery (MPA) and then into the Pulmonary Arteries (to left and right lungs).
Pathway of a Drop of Blood (Oxygenated Blood to Body):
Replenished with oxygen in the lungs.
Returns to the Left Atrium (LA) via the four Pulmonary Veins (two from left lung, two from right lung).
Note: Pulmonary veins are posterior to the heart, with a slightly longer travel path to the LA.
Passes through the Mitral valve into the Left Ventricle (LV).
Passes through the Aortic valve into the Aorta.
Aorta distributes blood:
To upper body and brain (via carotids, innominate, subclavian arteries).
To abdomen and lower extremities (via descending aorta, passing behind LA/LV, through diaphragm, bifurcating into iliacs).
Blood returns via the venous system, completing the cycle.
Cardiac Conduction System: Electrical Impulses
Specialized Muscle Cells:
A group of specialized muscle cells in the heart walls that send signals to cause contraction.
Normal Excitation Pathway:
Sinoatrial (SA) Node: "Pacemaker of the heart"; originates normal excitation.
Propagates through both atria.
Generates 70-80 pulses per minute (normal rate).
Atrioventricular (AV) Node:
Impulse pauses for approximately 0.1 seconds at the AV node.
This pause allows the ventricles to fill with blood.
Atrial depolarization spreads to the AV node, connecting atria to ventricles.
Bundle of His:
Electrical impulse travels from the AV node through the Bundle of His.
Purkinje Fibers:
Bundle of His branches into Purkinje fibers.
These fibers excite the myocardium around both ventricles, ensuring coordinated contraction.
Left ventricle (LV) requires significant excitation due to its thicker myocardium and role in pumping blood to the entire body.
Impact of Conduction Abnormalities:
Any deviation from the normal SA node firing rate (slower or faster) can impair myocardial contraction ability.
SA or AV node dysfunctions affect the firing sequence and, consequently, the mechanical contractility of the heart (visible on echocardiogram).
does the SA node start firing after diastole?
After diastole, the SA node does indeed begin to fire, initiating the next cardiac cycle by generating an action potential that leads to atrial contraction. This firing is critical as it sets the rhythm for the heart and ensures that the atria contract before the ventricles, allowing for effective blood flow and optimal cardiac output.
Arrhythmias and ECG Tracings
ECG/EKG Terminology:
Electrocardiogram (ECG) and EKG are the same; "K" is used in some countries (e.g., UK) for "kardio."
In the United States, "ECG" is technically preferred.
ECG Interpretation:
Monitors the heart's electrical activity.
Typically involves 12 to 15 lead placements to monitor different electrical tracings.
Cardiovascular students receive advanced ECG training to correlate rhythms with mechanical echocardiogram findings.
Key ECG Waves and Intervals:
P wave: Represents atrial depolarization (activation/contraction).
Small deflection wave, starts at SA node, travels to RA then LA, followed by relaxation towards AV node.
PR interval: Time between the first deflections of the P wave and the QRS complex.
Prolonged or shortened intervals can indicate disease or arrhythmia (dysrhythmia).
ECG graph paper boxes represent specific time intervals.
QRS complex: Represents ventricular contraction (depolarization), followed by blood ejection.
Electrical fibers travel to both ventricles.
T wave: Represents ventricular repolarization (resting/filling phase).
Cardiac muscles are completely repolarized during diastole.
Normal Sinus Rhythm:
A normal heartbeat where all cardiac cycles are equally spaced and occur due to normal SA and AV node firing.
"Sinus rhythm" inherently implies a normal rhythm, making "normal sinus rhythm" somewhat redundant.
Common Arrhythmias/Dysrhythmias:
Tachycardia: A fast heartbeat, heart rate above 60 BPM.
Shortened diastolic interval, more QRS complexes per time period.
Bradycardia: A slow heartbeat.
Longer diastolic interval, fewer cardiac cycles per time period.
Can cause insufficient blood output to the body and brain.
Irregular Heartbeat (Arrhythmia/Dysrhythmia):
Sporadic, can speed up or slow down, unpredictable timing.
"Arrhythmia" means "without rhythm" (chaotic); "dysrhythmia" means "bad rhythm." Often used interchangeably.
Specific Dysrhythmias and Their Implications
Atrial Fibrillation (A-fib):
Most common chronic arrhythmia.
Characterized by erratic and chaotic atrial electrical activity, with atrial rates of 400-600 BPM (compared to normal 70-80 BPM).
Atrial rapid firing leads to ventricles pumping faster, causing a tachycardic event.
ECG: P wave can be absent or replaced by fibrillatory waves (rapid, chaotic waves).
Consequences: Heart works harder, leading to hypertrophy (thickening of myocardial walls).
Can cause cardiomyopathy (myocardial dysfunction) and congestive heart failure (CHF).
CHF involves fluid buildup around the heart/lungs, impairing pumping efficiency.
Atrial Flutter:
"Sawtooth pattern" on ECG.
Atria beat too quickly, resulting in a fast but usually regular rhythm.
SA node fires chaotically and too fast but consistently.
Both A-fib and Atrial Flutter can lead to severe problems and potentially death.
Ventricular Tachycardia (V-tach):
Appears as "mounds" on ECG.
A very serious condition: rapid heartbeat originating in the heart's lower chambers (ventricles).
Electrical problems occur at the ventricles, Purkinje fibers, or Bundle of His, even if atria/SA/AV nodes are normal.
Can lead to fainting, cardiac arrest, or sudden death.
Ventricular Fibrillation (V-fib):
An emergency requiring immediate medical attention, a frequent cause of sudden cardiac death.
Rapid, chaotic electrical signals replace coordinated ventricular contraction.
Heart cannot pump blood effectively, leading to immediate shutdown (no blood/oxygen to organs).
ECG: No identifiable P, QRS, or T waves; appears as a wavy line.
Rate can be 150-500 beats per minute.
Indicates near death; immediate code activation is necessary in clinical settings.
Correlation of Mechanical Abnormalities with ECG and Echo
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Conduction Abnormalities and Heart Disease:
Normal sinus rhythm vs. A-fib (inconsistent SA firing, closer intervals).
Relationship between arrhythmia and cardiomyopathy can be complex (chicken or egg scenario).
Right Bundle Branch Block (RBBB):
Delay or blockage in electrical impulse pathway to the heart.
Can result in myocardial infarction (heart attack) due to damage or necrosis (death) of cardiac muscle.
Necrosed tissue cannot contract/relax, impairing blood ejection.
Dilated Cardiomyopathy:
Myocardial pathology, can be genetic or due to other factors.
Characterized by dilated ventricles and atria due to excessive blood volume; heart struggles to eject blood.
Can lead to A-fib, V-tach, or Left Bundle Branch Block (LBBB).
Valve Impairments:
Leaky valves (Regurgitation): Valves (e.g., mitral) do not close completely during their designated phase (e.g., systole), causing blood to leak backward into a preceding chamber (e.g., LA).
Blood leakage can be visualized with color Doppler.
Causes heart murmurs.
Valvular Stenosis: Calcium buildup around a valve prevents it from opening fully.
Also causes heart murmurs.
Murmurs are abnormal sounds detected during auscultation, indicating unusual blood movement across valves (leakage or restricted opening).
Assessing Cardiac Physiology with Echocardiography
Doppler Techniques
Color Doppler: Assesses the direction and pattern of blood flow.
Example: In parasternal long axis view, regurgitation (blood leaking back into LA, away from transducer) is visible as abnormal flow.
Normal flow direction in the left heart: LA through mitral valve to LV.
Regurgitation means blood that should be ejected is not, causing the ventricle to pump harder and potentially leading to wall hypertrophy.
Spectral Doppler (Pulse Wave and Continuous Wave):
Provides definitive measurements of blood velocity and timing.
Pulse Wave Doppler: Uses a sample gate (e.g., across the mitral valve) to generate flow patterns like the E and A waves.
Normally, the A wave (atrial kick) is smaller than the E wave (early diastolic filling), but reversal can indicate disease.
Continuous Wave Doppler: Constantly fires and receives, allowing measurement of high-velocity flow along an entire line (e.g., across the aortic valve).
Can detect flow towards or away from the transducer, identifying abnormal flow (e.g., aortic regurgitation flowing abnormally towards the transducer).
Importance: Understanding the normal pathway of blood flow is crucial to recognizing abnormalities with both color and spectral Doppler.
Cardiac Ultrasound Imaging: Scan Planes and Windows
Cardiac Scan Planes
Differ from general imaging (longitudinal/transverse).
Long Axis Views: Based on the heart's own anatomy, from apex (inferior) to base (superior).
Short Axis Views (Cross-Sectional): Perpendicular (90 degrees) to the long axis, slicing the heart like a loaf of bread.
Heart Position in Chest:
Left anterior oblique (leftward of the sternum, apex usually leftward).
The long axis of the heart is relative to itself, not the body (e.g., anterior, posterior, lateral walls, free wall of RV, base, apex).
Orientation terminology is specific to cardiac imaging.
Acoustic Windows (Avenues to the Heart)
Designed to bypass bony structures (rib cage) and lungs by utilizing intercostal spaces.
Main Windows:
Left Parasternal Window: To the left of the sternum, typically 3rd or 4th intercostal space.
Apical Window: More lateral, often 5th or 6th intercostal space, at the apex of the heart.
Subcostal Approach: Inferior to the xiphoid process, looking up at the heart (caution to avoid xiphoid/pushing too hard).
Suprasternal Notch: Above the sternum, below the thyroid/Adam's apple, looking down at the ascending aorta and aortic arch.
3D Nature of the Heart
As a 3D organ, the transducer must be moved to visualize structures from various angles (anterior, posterior, lateral, inferior, superior, left, right).
Probe positions vary depending on the patient, requiring finding the "best window."
Ergonomics in Cardiac Scanning
Importance:
Critical for sonographer comfort and injury prevention.
Historical debate on left-handed vs. right-handed scanning.
Current encouragement for students to be ambidextrous and practice both methods.
Recommended Scanning Positions (Caroline Coffin's Video):
Ideal: Scan from the left side of the bed using the left arm.
Set up control panel for comfortable right arm use, turn panel slightly away from the table.
Monitor close to the patient, in front of eyes (to engage patient).
Use a cushion for wrist/forearm support to maintain a straight wrist and arm, preventing flexion.
Apical Views:
Ideally use an exam table with a cutout or cushion with a cutout to allow scanning the apex from the side with a straight wrist and arm.
Subcostal and Suprasternal Views:
Stand up to keep the arm close to the body, reducing abduction.
Alternative Right-Handed Scanning (to improve ergonomics for right-handed sonographers):
Position the ultrasound system at the foot of the exam table.
Sit so both sonographer and patient face the same direction.
Adjust control panel for the left typing hand, and monitor height.
Allows for parasternal and apical views with arm/wrist support, potentially superior for lateral apical views without wrist flexion.
Note: The presenter in the video's ideal bed height for parasternals is critiqued as too low; adjusting stretcher angle is also suggested.
Professor's Perspective:
While historical recommendations favored left-hand scanning, current practice encourages finding what is safest and most comfortable for the individual sonographer.
Finding Acoustic Windows: The Circle Technique
Method:
Similar to abdominal scanning, begin with larger movements to find a starting point, then fine-tune with fanning, tilting, etc.
"Circle Survey" or "Window Shopping": A technique for new sonographers to master basics and build confidence.
Procedure:
Begin with the patient in left lateral decubitus position (though video may show supine for demonstration), then adjust as needed.
Move the transducer in a circular motion over the cardiac region.
Observe the screen for bright images, indicating a good acoustic window.
The circular motion makes it easy to return to a previously found good window if passed.
Start with gross hand movements, then make smaller manipulations to fine-tune the image once a window is found.
Benefits:
Helps stumble upon the best possible window.
Provides confidence in moving away from and returning to a good window.
Avoids working in suboptimal windows out of fear of losing the best one.
ECG Leads in Scanning
Usage:
ECG leads are always used during cardiac scans for timing purposes, not primarily for rhythm detection (unlike a 12 or 15 lead ECG).
A 3-lead system is typically used.
Placement:
One lead under the right clavicle (more lateral).
Another lead on the right side.
A third lead (ground) closer to the left, below the diaphragm (avoiding abdomen for respiration noise and apical window interference).
The three leads form a triangle.
Mnemonic for lead placement: "Smoke before Fire" (White lead on the right = Smoke, Red lead on the left = Fire, with the third lead being the ground).
Supplemental Materials and Lab Preparation
Reading Materials:
Encouraged to read supplemental materials (found in lecture/assignment sections) to help identify structures in parasternal long, parasternal short, and apical views.
Lab Activities:
Students will be obtaining approximately 4-5 images in the lab.
Prepare questions for instructors and practice cardiac views for fun and proficiency.