DMS 100 cardiac lecture 2 of 2

1. Introduction to Transthoracic Echocardiograms (TTE)

  • Moving images (clips, real-time loops) are used to visualize the dynamically beating heart.

  • Loop acquisition can vary by seconds or number of cardiac cycles.

2. Objectives for Cardiac Imaging

  • Define the purpose of an echocardiogram.

  • Identify indications for various echocardiography exams.

  • Name different types of echocardiography exams.

  • Compare capabilities and limitations of transthoracic echo.

  • Describe required instrumentation for optimal exams and images.

  • Recognize cardiac scan planes and screen orientation (differs from general ultrasound).

  • Identify cardiac views and structures within each view.

  • Demonstrate basic scanability during lab and practice proper ergonomics.

  • Capture required images for assignments.

3. Purpose of Cardiac Ultrasound Exams

  • Physician Assessment: Allows physicians to view internal heart structures, assess functionality and structure (anatomy), and investigate physiology (blood flow, contractility, relaxation).

  • Method: Sound beams are sent into internal heart structures.

  • Evaluates:

    • Size of chambers.

    • Thickness and mobility of valve leaflets.

    • Thickness of cardiac muscle (myocardium, endocardium, pericardium).

    • Contractility and pumping action of atria and ventricles.

  • Advantages:

    • Fast and easy to evaluate.

    • One of the most affordable imaging exams.

    • Very portable.

    • Relatively painless (except for a tender "sweet spot" between the breasts/on the breastbone).

  • Duration: Typically 30-60 minutes; longer for pathology or technically difficult patients.

4. Echocardiographer Credentials and Interpreting Physicians

  • Credentialing Organizations:

    • ARDMS: Registered Diagnostic Cardiac Sonographer (RDCS) credential.

    • CCI: Registered Cardiac Sonographer (RCS) credential.

  • Interpreting Physicians: Primarily cardiologists (non-invasive or invasive), occasionally internists.

    • Cardiologists focus on treating the heart and cardiovascular system, including great vessels, rhythm disorders, coronary arteries, heart attacks, and heart defects.

5. Indications for Cardiac Studies

  • Chest pain or shortness of breath (can be radiating or caused by other issues).

  • Pericardial effusion (fluid around the heart, inside the pericardium) – important to differentiate from pleural effusion or ascites.

  • Heart murmurs (suggestive of valve problems, often multiple valves).

  • Ventricular function (assessing diastolic and systolic action).

  • Congenital heart disease (e.g., "hole in the heart," absent valves/leaflets, improper chamber formation, great vessel problems); used for diagnosis and follow-up post-surgery.

  • Masses in chambers or on valves (e.g., blood clots, tumors, vegetations from infective agents).

6. Types of Cardiac Exams

  • Transthoracic Echo (TTE):

    • Most common type.

    • External source, beam sent into chest wall from outside.

    • Requires acoustic gel to break air barrier.

  • Transesophageal Echo (TEE):

    • Second most utilized type.

    • Intracavitary transducer (patient swallows it into esophagus).

    • Provides close proximity to the heart, allowing detection of small, subtle, or difficult-to-see abnormalities.

    • Performed with mild sedation.

  • 3D (4D) Echo:

    • Provides full volume imaging or real-time zoom for detailed views of valve leaflets (4th dimension is the beating heart).

  • Specialty Echos:

    • Adult Echo: Primary focus of the program.

    • Pediatric and Congenital Echo.

    • Fetal Echo: Specialty area, often requiring additional training.

  • Stress Echocardiograms:

    • Performed when patients exhibit symptoms (e.g., chest pains, palpitations) under demand, but are fine at rest.

    • Treadmill Stress Echo: Patient exercises to maximal heart rate to assess muscle contraction.

    • Pharmacological Stress Echo: Medicine administered to increase heart rate, mimicking exercise effects.

  • Contrast Echo:

    • Invasive, contrast agent administered.

    • Improves visualization of walls and motion in technically difficult patients.

  • Echo-Guided Interventional Procedures:

    • Ultrasound used to guide procedures (e.g., pericardiocentesis for fluid removal, stent placement).

    • Resynchronization Therapy: Used to restore heart rhythm in cases of dyssynchrony (AV or SA node out of rhythm).

7. Cardiac Ultrasound Anatomy

7.1. Thoracic Protection and Heart Position

  • Rib Cage: Clavicle, intercostal spaces are important for transducer placement.

    • Parasternal views: Often in 3rd or 4th intercostal space.

    • Apical views: Often in 6th or 7th intercostal space.

  • Sternum: Parasternal views are typically to the left of the sternum.

  • Heart Position: Sits in a left anterior oblique orientation within the chest.

7.2. Internal Structures of the Heart

  • Chambers:

    • Right Atrium (RA)

    • Left Atrium (LA)

    • Right Ventricle (RV)

    • Left Ventricle (LV)

  • Measurements (Examples):

    • Left Atrium (LA) diameter: Usually less than 4.1 cm.

    • Left Ventricle (LV) diameter: Usually less than 6 cm.

    • Deviations can indicate dilation or atrophy.

    • RA and RV are generally smaller than their left-heart counterparts.

  • Valves:

    • Pulmonary Valve: Most superior valve.

    • Tricuspid Valve: Most inferior valve (slightly more inferior than mitral, due to RV wrapping around LV).

    • Aortic Valve.

    • Mitral Valve (Bicuspid): Only valve with two leaflets/cusps.

    • Leaflets vs. Cusps:

    • Atrioventricular (AV) valves (tricuspid and mitral) have pliable leaflets, tethered by chordae tendineae and papillary muscles.

    • Semilunar valves (aortic and pulmonary) have semi-lunar cusps (small pockets).

    • Terms are often used interchangeably, but are technically different.

  • Other Structures:

    • Chordae (chordae tendineae).

    • Interatrial Septum (IAS).

    • Interventricular Septum (IVS).

    • Trabeculae Carinae: Ridges inside ventricular walls aiding blood expulsion and valve closure.

    • Papillary Muscles.

    • Valve Annulus.

  • Coronary Sinus: The last venous structure and most deoxygenated blood in the heart before returning to the right atrium.

7.3. Relational Anatomy Review (Apical Four Chamber View Example)

  • Left Ventricle (LV) free wall (lateral wall) is lateral to the Interventricular Septum (IVS).

  • Interatrial Septum (IAS) is superior to the IVS (when viewing from apex to base).

  • Apex is inferior to the base of the heart.

  • Right Atrium (RA) and Left Atrium (LA) are typically isoechoic (similar echogenicity).

7.4. Screen Orientation in Echo

  • Orientation Notch: Located on the right side of the imaging screen (differs from general/vascular imaging where it's on the left).

  • Apical View Orientation: Top of image represents inferior structures (apex), bottom represents superior structures (base).

    • With notch (indicator) on the right, it correlates to the patient's left side on the image, making the right side of the image the patient's right.

8. Exam Preparation and Instrumentation

8.1. Pre-Exam Preparation

  • Guidelines and Protocol: Follow general rules for measurements, views, color, and spectral use.

  • Environment: Safe, quiet, well-lit initially for patient interaction, then dimmed for optimal ultrasound imaging (ambient lighting or total darkness).

8.2. Patient Positioning

  • Left Lateral Decubitus: Ideal position; patient on left side, upper body slightly elevated, right shoulder turned in.

    • Head down to avoid chest muscle strain, which can hinder intercostal access.

    • Why left lateral: Heart rolls forward, closer to chest wall, shortening beam path and improving imaging (especially through breast tissue).

  • Supine: Used for subcostal and suprasternal views, or if patient cannot tolerate left lateral decubitus.

  • Patient Instructions: Explain procedure, talk throughout, and check for comfort/pain.

8.3. Sonographer Positioning (Ergonomics)

  • Left-Hand Scanning: Machine to patient's left, sonographer facing patient.

  • Right-Hand Scanning: Machine to patient's right, sonographer behind patient (can be challenging for apical views on larger patients).

  • Ergonomic Right-Hand Scanning: Sonographer on patient's left, machine at other end, potentially using a dropout table for better lateral apical views.

  • Ambidexterity: Highly recommended due to varying clinical environments (SICU, ICU, ER, OR).

  • Ergonomic Adjustments: Adjust bed height, monitor height, seat, and use wedge pillows (triangle wedges covered with paper cases behind patient's back to maintain left lateral decubitus).

8.4. Patient Apparel and Skin Prep

  • Transthoracic Exam Prep: No fasting, normal eating/drinking, take meds as usual. Wear what they want (usually change to gown/cape).

    • Women given front-opening gown; encouraged to wear non-sports bras or remove them. Draping for privacy.

    • Men may also request gowns due to cold.

  • Avoidance: Scented lotions or perfumes (can cause agitation, gel residue, hinder ECG lead adhesion).

8.5. Instrumentation Details

  • Transducer:

    • Phased array (sector) transducer used.

    • Best for deeper structures due to lower frequency range.

    • Pie-shaped profile: Tightly grouped crystals that spread out in the far field, providing good near-field resolution.

  • Imaging Modes: 2D, Doppler (color and spectral), and M-mode (most times).

  • Frequency Range: 1-8 MHz; 1-5 MHz for adults, 8 MHz for pediatric/smaller adults.

9. Control Panel Optimization

9.1. 2D Image Optimization

  • Overall Gain (7): Located above the trackball; adjusts overall image brightness.

  • Depth (9): Located to the right of the trackball; adjusts imaging depth.

    • Parasternal views: Approximately 12-16 cm.

    • Apical and Subcostal views: Approximately 16-22 cm.

  • Focal Zones: Placed at or just below the area of interest.

  • Time Gain Control (TGC): Adjusts gain at specific depths using slide pods.

    • Cardiac typically uses a "backward C" configuration: less gain in the near field, more in the midfield, and less in the far field (due to the naturally bright pericardium).

  • Lateral Gain: Adjusts gain vertically; often called "smiley face" (boosting outside corners).

    • Used to improve visualization of lateral and septal walls, especially in apical views.

9.2. Frequency Fusion (2D Control Button)

  • A button that, when turned, offers three settings: Penetration, General, and Resolution.

  • Allows selection of various frequencies within the transducer's bandwidth (e.g., 1-5 MHz) to optimize for either better resolution (higher frequencies) or better penetration (lower frequencies) based on patient habitus.

  • Sends and receives at the same selected frequency.

9.3. Harmonic Imaging (Tissue Harmonics/Second Harmonics)

  • Allows sending at one frequency and receiving at another (e.g., sends at 1.3 MHz, receives at 2.6 MHz).

  • Provides improved resolution and good penetration simultaneously.

  • Reduces noise and artifact.

  • When activated (button turns orange), can still choose harmonic with Resolution, General, or Penetration settings.

9.4. M-Mode (Motion Mode)

  • Function: Provides a one-dimensional display of cardiac structures' motion over time.

  • Mechanism: A single sample volume line is placed across structures; the motion along this line is graphed.

  • Temporal Resolution: Excellent for rapidly moving structures (e.g., valves), enabling detection of subtle abnormalities.

  • Controls: M-mode gain, sweep speed (number of cardiac cycles displayed), and TGCs.

  • Display: Shows structures like the RV, interventricular septum, LV, mitral valve leaflets (anterior often V-shaped, posterior often W-shaped), and posterior wall moving through systole and diastole.

  • EPSS (Endpoint Septal Separation): Measures the relaxation phase distance of the mitral valve from the septal wall; indicative of LV function.

10. Electrocardiogram (ECG) Monitoring

  • Necessity: Always required with echo; timing is crucial for interpreting cardiac function.

  • Type: 3-lead ECG used (not 12-lead like diagnostic studies).

  • Lead Placement:

    • Right Arm (RA): Below right clavicle, near right shoulder, within rib cage frame.

    • Left Arm (LA): Below left clavicle, near left shoulder, within rib cage frame.

    • Left Leg (LL) / Ground: Placed below the diaphragm, lateral to the apical window to avoid interference with scanning.

    • Important to find soft spots (between ribs), avoid bony prominences and hairy/perspiring skin for good connection.

  • Goal: Obtain a clear QRS complex and accurate tracing.

  • Lab Lead Colors: White for right, Black for left, Red for ground.

  • Ed Toven's Triangle: Conceptual triangle for optimal lead placement to form a good conduction pathway through the heart.

  • ECG Relationship to Echo: Electrical activity (ECG) precedes mechanical activity (echo).

    • QRS complex corresponds to systole and mitral valve closure.

    • P wave and T wave (diastole) correspond to leaflet opening.

    • Perfect alignment is not expected, but significant dyssynchrony (misalignment) indicates a problem.

11. Cardiac Screen Orientation and Transducer Clock Analogy

  • Cardiac Preset: Automatically configures the ultrasound system with the indicator on the right side of the screen.

  • Clock Analogy: Used to describe transducer orientation on the chest wall (12:00 at chin, 6:00 at belly button, 3:00 to patient's left, 9:00 to patient's right).

    • Parasternal Long Axis: Notch towards 11:00 (patient's right shoulder).

    • Image orientation: Anterior to posterior (top to bottom), superior to inferior (top to bottom).

    • Parasternal Short Axis: Rotate transducer clockwise 90 degrees to 1:00 (patient's left shoulder).

    • Apical Views: Notch towards 3:00 (towards the bed, patient's left side).

  • Heart-as-Walnut Analogy: Apex is tapered, base is flatter. Beam passes through anterior wall, visualizing internal structures and posterior wall.

12. Sonography Scan Lab Overview

  • Cardiac Windows: Suprasternal, Parasternal, Apical, Subcostal.

  • Patient Position: Left lateral decubitus ideal, supine if necessary.

  • Probe: Small footprint, sector display, frequency range usually 1.5 to 3.6 MHz.

  • Preset: Select Cardiac preset to ensure correct image orientation (indicator on right).

  • Adjustments: Optimal gain, focus, depth, and TGC settings.

    • Depth: Parasternal (12-16 cm), Apical/Subcostal (16-22 cm).

13. Comparing 2D and M-Mode

  • Similarities: Both visualize anatomical details.

  • 2D Imaging:

    • Provides real-time, cross-sectional views of the heart.

    • Wider field of view, best for assessing overall structure and function.

  • M-Mode Imaging:

    • Provides detailed measurements of specific structures in one dimension (line of sight) over time.

    • Excellent temporal resolution, best for rapidly moving structures (e.g., valves).

    • Can identify small or subtle abnormalities that may be missed in 2D.

14. Doppler Imaging (Color and Spectral)

14.1. Color Flow Imaging

  • Based on pulse wave Doppler principles.

  • Displays intracavitary blood flow using a BART (Blue Away, Red Towards) color map only.

    • The color map is never flipped in echo (unlike vascular/abdomen).

  • Helps identify areas of blood flow and fastest red blood cell velocities for spectral Doppler placement.

14.2. Spectral Doppler (Pulse Wave & Continuous Wave)

  • Pulse Wave (PW) Doppler:

    • Measures red blood cell velocities at a particular site and depth using a sample gate.

    • Pros: Good range resolution.

    • Cons: Limitation on maximum velocity, leading to aliasing (PRF limit).

  • Continuous Wave (CW) Doppler:

    • Constantly sends and receives sound waves, evaluating all red blood cells along the line of sight (sample volume).

    • Pros: Very accurate measurements for high velocities (no aliasing, scale can go off the roof).

    • Cons: Poor range resolution, resulting in cluttered spectral windows.

  • Angle of Insonation: Always set to 0^ ext{o} in echo (parallel to flow) – never changed to 45^ ext{o} – 60^ ext{o}.

15. Cardiac Imaging Protocol (Sample)

  • Systematic Approach: Move from 2D observations to specific color and spectral assessments, then take measurements.

    • Be flexible: If pathology is found ("follow the rabbit hole"), investigate, then return to the main protocol.

  • Documentation: Document everything accurately for physician interpretation.

  • Sample Sequence:

    • Parasternal Long Axis (PLAX): 2D, deep/shallow depth adjustments, color, M-mode, measurements, zoom.

    • Right Ventricular Inflow and Outflow Views (RVIT, RVOT).

    • Parasternal Short Axis (PSAX): Various levels (base/aortic valve, mitral valve, papillary muscles, apex).

    • Apical Views: Apical four-chamber (AP4C), Apical five-chamber (AP5C), Apical two-chamber (AP2C), Apical three-chamber (AP3C).

  • Image Count: A complete echocardiogram can involve 60 to 120 images.

16. Cardiac Windows and Views (Detailed Acquisition)

16.1. Parasternal Window

  • Parasternal Long Axis (PLAX):

    • Transducer Position: Left of sternum, notch towards 11:00 (patient's right shoulder).

    • Sweet Spot: Often in the "V" of a bikini top for women, or at/above the nipple line for less breast tissue.

    • Structures Seen: Right ventricle (RV), interventricular septum (IVS), aortic root, ascending aorta, right coronary cusp, non-coronary cusp, anterior mitral valve leaflet, posterior mitral valve leaflet, left ventricle (LV), left atrium (LA), posterior wall, descending aorta (sometimes seen posteriorly).

    • Orientation: Anterior (near field) to posterior (far field), superior (aorta) to inferior (apex).

  • Parasternal Short Axis (PSAS):

    • Transducer Position: Rotate clockwise 90 degrees from PSAL to aprox. 1:00 (patient's left shoulder).

    • Fanning: Fan superiorly to inferiorly to obtain different levels.

    • Orientation: Anterior (near field) to posterior (far field), right to left (on screen, patient's right-left).

    • Levels (from superior to inferior):

    1. Base/Aortic Valve Level: Aortic valve (often seen as "Mercedes Benz" sign), tricuspid valve, pulmonic valve.

    2. Mitral Valve Level: Often called "fish mouth" view; anterior and posterior mitral valve leaflets, IVS, RV.

    3. Papillary Muscle Level: Anterolateral and posteromedial papillary muscles within the LV.

    4. Apex Level: Most inferior, tapered view of the LV without other internal structures.

16.2. Apical Window

  • Sweet Spots: For women, often at the underwire line, lateral. For less breast tissue, lateral to the nipple line. Start lateral and work medially.

  • Apical Four Chamber (AP4C):

    • Transducer Position: Inferior on chest, notch towards 3:00 (patient's left, toward bed).

    • Orientation: Inferior (apex, near field) to superior (base, far field), left (where notch is) to right.

    • Structures Seen: Right atrium (RA), left atrium (LA), right ventricle (RV), left ventricle (LV), interatrial septum (IAS), interventricular septum (IVS), mitral valve, tricuspid valve.

    • Additional Structures (difficult to see or depending on view): Right upper pulmonary vein, left upper pulmonary vein, descending aorta, left lower pulmonary vein (right lower pulmonary vein difficult to view).

    • Angling Tip: If seeing too much aortic valve, tilt transducer beam inferiorly (tail up towards patient) to move the aortic valve out of view.

17. Lab Acquisition Tasks (Examples for the Week)

  • Acquire a real-time clip of the parasternal long axis (PSAL).

  • Obtain M-mode across the mitral valve in PSAL view, then display side-by-side with 2D.

  • Acquire a real-time clip of the parasternal short axis (PSAS) at the mitral valve level.

  • Obtain an apical four-chamber (AP4C) view in 2D, then turn on color Doppler, and place a Continuous Wave (CW) sample volume across the mitral valve for an M-shaped waveform.

18. Lab Tips

  • Systems may be set up for left or right-hand scanning; adjust as needed.

  • Ensure sufficient slack on power and internet cords if repositioning the machine.