CVS-204 Week-3 Lecture Notes: Heart Murmurs, S₂ Splitting, Exam Logistics
Course & Administrative Logistics
- Attendance sheet circulating – everyone must sign.
- Slides for all content have been resent. If you did not receive them, verify you are on the instructor’s roster.
- Exam Schedule
- Week 4 → CVS-204 first didactic exam ("100s" section): next week
- Protocol (lab/scan) practical → next Friday of Week 4
- Total of two exams in the 4-week block (didactic + protocol).
- Respondus LockDown Browser
- Required for all written exams.
- Works on Windows & Mac laptops; iPads are NOT allowed in CV department testing.
- A PDF with download instructions and an optional tutorial video will be emailed.
- Must be downloaded/installed by next Monday (before first "100s" test).
- Launch sequence on test day: open Respondus → it automatically launches Canvas → exam appears under course CVS-204 as a published quiz.
Study Scope for Upcoming Exam
- Textbook chapters: 1, 2, and 4 only.
- Chapter 1 – Anatomy review
- Chapter 2 – Lymphatic & basic vascular physiology
- Chapter 4 – Introduction to ECG/Conduction (only material already covered in lecture).
- Stop reading exactly where lecture slides end. Later sections are intentionally omitted to avoid overload.
- No labeling diagrams on this exam.
- Content emphasis
- Cardiac chambers, valves, coronary arteries & veins, moderator band, conduction system, cardiac cycle, and murmurs/splitting phenomena.
Cardiac Anatomy & Review Points
- Moderator Band
- Located in the right ventricle (RV) near the apex.
- Acts like a “rubber band.” Prevents RV over-expansion; snaps ventricle back after systole.
- Coronary vessels – know basic origins and territories (reviewed last week).
- Conduction system – students should recognise each major segment and its basic function (SA node → Internodal → AV node → Bundle of His → Right & Left bundle branches → Purkinje network).
Heart Sounds Primer
- ("lub") – closure of mitral + tricuspid (AV) valves at start of ventricular systole.
- ("dub") – closure of aortic (A2) + pulmonic (P2) (semilunar) valves at end of systole.
- A2 = aortic valve closure sound.
- P2 = pulmonic valve closure sound.
- Normal physiology: very slight split of A2 then P2 during inspiration, single fused sound during expiration.
Physiologic & Pathologic Splitting of S2
- Key concept: Timing between A2 and P2 varies with respiration and pathology.
Normal (Physiologic) Splitting
- Expiration – valves close almost simultaneously (single sound).
- Inspiration – negative intrathoracic pressure ↑ venous return to RV → RV ejection prolonged → P2 occurs slightly after A2 (two quick successive sounds).
Wide (Widened) Splitting
- A2–P2 gap larger in both inspiration & expiration.
- Etiology
- Right Bundle Branch Block (RBBB) – delayed RV activation.
- Pulmonic Stenosis – prolonged RV ejection.
- Auscultation graph: A2 then noticeably later P2 for both respiratory phases, with a marginally greater delay during inspiration.
Fixed Splitting
- A2–P2 interval unchanged by respiration (identical delay during inspiration & expiration).
- Classic cause: Atrial Septal Defect (ASD) – constant left-to-right shunt equalizes RV/LV stroke volumes.
Paradoxical (Reversed) Splitting
- Order reverses – P2 precedes A2 during expiration; they fuse or nearly fuse during inspiration.
- Causes
- Left Bundle Branch Block (LBBB) – delayed LV activation.
- Severe Aortic Stenosis – prolongs LV ejection.
Quick Audio Mnemonics (as played in class)
- Normal ⇒ crisp "lub-dub lub-dub".
- Wide ⇒ distinctly spaced "lub-d…ub" in every breath.
- Fixed ⇒ symmetric spacing regardless of breath.
- Paradoxical ⇒ "lub-dub" becomes "lubd-ub" (fused on inspiration).
Major Murmurs & Representative Audio Characteristics
(Website link with audio clips will be emailed to class)
| Condition | Hemodynamics | Classic Auscultation Clue |
|---|---|---|
| Early Aortic Stenosis | Mild cusp calcification → partial obstruction | Lower-pitched, earlier systolic ejection click; softer closure (A2). |
| Late/Severe Aortic Stenosis | Marked calcification → narrow orifice | Harsh, crescendo–decrescendo systolic murmur; delayed, diminished A2. |
| Pulmonic Stenosis | RV outflow obstruction | Similar to AS but heard best LSB 2nd ICS; widened S2 split. |
| Mitral Regurgitation (MR) | Retrograde flow LV→LA in systole | High-pitched blowing holosystolic “hiss,” often radiates to axilla. |
| Aortic Regurgitation (AI) | Diastolic backflow aorta→LV | Long, decrescendo diastolic “blowing” murmur; bounding pulse; wide PP. |
| Mitral Stenosis (MS) | Thickened mitral leaflets | Low-frequency diastolic rumble preceded by opening snap. |
| Benign/Functional Flow Murmur | No structural disease | Soft, short, early- to mid-systolic; varies with position; normal S2. |
| Atrial Septal Defect (ASD) | Interatrial shunt | Continuous whooshing plus fixed S2 split; sounds like constant flow. |
| Ventricular Septal Defect (VSD) | Interventricular shunt | Loud harsh holosystolic; lower pitch than ASD (closer to apex). |
| Patent Ductus Arteriosus (PDA) | Aorta↔Pulmonary artery shunt | "Machinery" continuous murmur; obscures valve closure sounds. |
Audio descriptors used in class:
- “Crisp snap” = normal valve excursion/closure.
- “Deeper / dull” = calcified or stenotic valve (reduced excursion).
- “Long drawn-out jet” = regurgitant flow (AI, MR).
- “Constant washing sound” = shunt murmurs (ASD, PDA).
Clinical Integration & Workflow
- Physicians auscultate → detect abnormal split or murmur → order echocardiogram.
- Sonographer’s role
- Confirm suspected pathology (e.g.
- colour Doppler across ASD/VSD
- measure gradients across stenotic valve using ).
- Assess secondary effects (chamber enlargement, pressure overload).
- Understanding murmur timing helps target protocols (e.g., add RVOT colours if wide split suggests PS).
Frequently Asked Classroom Q&A
- Q: "Will we be tested on capillary gas exchange details?"
A: No – focus only on macroscopic flow through heart. - Q: "Do we need exact bundle branch block pathways?"
A: Know major limbs (RBB, LBB) and implications for S2 splitting patterns. - Q: "Moderator band location/function?"
A: Right ventricle; limits over-distension, analogous to chordae at the apex. - Q: "Meaning of A2 / P2 labels?"
A: A2 = second (S2) component from Aortic valve; P2 = pulmonic component.
Study Tips from Instructor
- Read textbook only up to content covered on slides.
- Re-listen to provided audio clips repeatedly; link heart sound → pathology.
- Visualize auscultation graphs (hand-drawn in lecture) to fix timing differences.
- Expect multiple-choice questions rather than labeling.
- Practise Respondus launch BEFORE exam day.