cd /tmp/workspace && python3 -c " import pdfplumber with pdfplumber.open('/tmp/workspace/attachments/54d24003-e35b-49d4-a35b-9c892b9663e1/Heart.pdf') as pdf: print(f'Total pages: {len(pdf.pages)}') for i, page in enumerate(pdf.pages): text = page.extract_text() print(f'--- PAGE {i+1} ---') print(text) print() "

mkdir -p /tmp/workspace/heart-notes && cat > /tmp/workspace/heart-notes/Heart_Study_Notes.md << 'ENDOFNOTES' # HEART & PERICARDIUM — Study Notes ### BD Chaurasia's Human Anatomy, Vol. 2 (Thorax) — Chapter 18 --- ## 1. INTRODUCTION - Heart = conical hollow **muscular** organ in the **middle mediastinum**, enclosed in pericardium. - Greek: *cardia* → cardiac; Latin: *cor* → coronary - Position: Obliquely behind body of sternum + adjoining costal cartilages. - **1/3rd to the right** of median plane, **2/3rd to the left**. - **Four chambers**: RA, LA, RV, LV - Atria lie **above and behind** ventricles. - Separated by: - Atria from ventricles → **atrioventricular (coronary) groove** - Atria from each other → **interatrial groove** - Ventricles from each other → **interventricular groove** (anterior + posterior parts) ### Measurements | Parameter | Value | |-----------|-------| | Shape | Conical/Pyramidal | | Length (base to apex) | 12 cm | | Width (broadest) | 8-9 cm | | Weight (male) | 300 g | | Weight (female) | 250 g | --- ## 2. EXTERNAL FEATURES ### Direction - **Apex**: downwards, forwards, to the left - **Base (posterior surface)**: backwards ### Surfaces (Gray's Anatomy 42nd edn) 1. **Anterior/Sternocostal** 2. **Inferior/Diaphragmatic** 3. **Right pulmonary** 4. **Left pulmonary** *(Previous concept: 3 surfaces — anterior, inferior, left)* ### Borders | Border | Formation | |--------|-----------| | **Right** | Right atrium (RA); from SVC to IVC | | **Left** | Mainly LV + partly left auricle; from apex to left auricle | | **Inferior** | Mainly RV + small LV near apex; from IVC to apex. Has *Incisura apicis cordis* near apex | | **Upper** | Both atria (chiefly LA); overlapped by pulmonary trunk + aorta | --- ## 3. GROOVES / SULCI ### 3a. Atrioventricular (Coronary) Sulcus Circular groove separating atria from ventricles: - **Anterior part**: - *Right half*: oblique, between right auricle + RV → lodges **right coronary artery** - *Left part*: small, between left auricle + LV → lodges **circumflex branch of left coronary artery** - **Posterior part**: between base and diaphragmatic surface → lodges **coronary sinus** ### 3b. Interatrial Groove - Faintly visible posteriorly; hidden anteriorly by aorta + pulmonary trunk. ### 3c. Anterior Interventricular Groove - Nearer to left margin; runs downwards and to the left. ### 3d. Posterior Interventricular Groove - On diaphragmatic (inferior) surface; nearer to right margin. - Two IVGs meet at inferior border near apex. > **Crux of the Heart** = meeting point of interatrial, atrioventricular, and **posterior** interventricular grooves. --- ## 4. APEX OF HEART - Formed entirely by **left ventricle** - Direction: downwards, forwards, to the left - Location: **left 5th intercostal space**, 9 cm lateral to midsternal line, just medial to midclavicular line ### Clinical Points - **Apex impulse**: outward thrust during ventricular systole at above location - **Apex beat**: felt at site of apex impulse - In children < 2 years: apex in left **4th** ICS at midclavicular line - **Dextrocardia**: apex on right side (may be part of *situs inversus*) --- ## 5. BASE (POSTERIOR SURFACE) - Formed mainly by **left atrium** + small part of right atrium - Openings: 4 pulmonary veins (→ LA) + SVC + IVC (→ RA) - Level: **T5–T8** vertebrae (lying); descends 1 vertebra in erect posture - Separated from vertebral column by: pericardium, right pulmonary veins, oesophagus, aorta --- ## 6. SURFACES (Detail) | Surface | Formation | |---------|-----------| | **Anterior/Sternocostal** | Mainly RA + RV; partly LV + left auricle. Uncovered area behind cardiac notch = *area of superficial cardiac dullness* | | **Inferior/Diaphragmatic** | Left 2/3rd = LV; Right 1/3rd = RV. Traversed by posterior IVG | | **Left surface** | Mostly LV + upper end = left auricle. Upper part crossed by coronary sulcus | | **Right surface** | Rounded, formed by right atrial wall. Sulcus terminalis separates it from anterior surface | --- ## 7. RIGHT ATRIUM (RA) **Position**: Right upper chamber; receives venous blood from whole body; pumps to RV through tricuspid orifice. ### External Features - Elongated vertically: SVC at top, IVC at bottom - Upper end → **right auricle** (covers root of ascending aorta, overlaps infundibulum of RV) - **Sulcus terminalis**: shallow groove on right border (SVC to IVC); internally → **crista terminalis** - Upper part contains **SA node** - Right AV groove separates RA from RV; lodges right coronary artery + small cardiac vein ### Inlets/Tributaries 1. Superior vena cava 2. Inferior vena cava 3. Coronary sinus 4. Anterior cardiac veins 5. Venae cordis minimae (Thebesian veins) 6. Sometimes right marginal vein ### Internal Features — Three Parts: #### A. Smooth Posterior Part (Sinus Venarum) - Derived from **right horn of sinus venosus** - SVC opens at upper end - IVC opens at lower end; guarded by **Eustachian valve** (guides IVC blood → LA via foramen ovale in embryo) - **Coronary sinus** opens between IVC opening and tricuspid orifice; guarded by **thebesian valve** - **Venae cordis minimae**: small foramina in all 4 chamber walls - **Intervenous tubercle of Lower**: small projection on posterior wall, just below SVC opening (directs SVC blood → RV in embryo) - **Triangle of Koch**: bounded by ostium of coronary sinus + septal leaflet of tricuspid valve + tendon of Todaro. **AV node lies at its apex** #### B. Rough Anterior Part (Pectinate Part) + Auricle - Derived from **primitive atrial chamber** - **Musculi pectinati**: transverse muscular ridges; arise from crista terminalis, run forwards/downwards toward AV orifice (like teeth of a comb) - In auricle: muscles interconnected as reticular network #### C. Interatrial Septum - Derived from septum primum + septum secundum - Shows **fossa ovalis**: shallow saucer-shaped depression in lower part = site of embryonic septum primum - **Annulus/Limbus fossa ovalis**: prominent margin; lower free edge of septum secundum; deficient inferiorly - Remains of foramen ovale = small slit-like valvular opening (normally occluded after birth) --- ## 8. RIGHT VENTRICLE (RV) **Position**: Triangular chamber; receives blood from RA; pumps to lungs via pulmonary trunk. Forms inferior border + 2/3rd sternocostal + 1/3rd inferior surface. ### Internal Features #### Two Parts: - **Inflowing part**: rough, has trabeculae carneae; develops from **proximal bulbus cordis** - **Outflowing part (Infundibulum)**: smooth, upper conical, gives rise to pulmonary trunk; develops from **midportion of bulbus cordis** - Separated by **supraventricular crest (infundibuloventricular crest)** #### Two Orifices: - **Tricuspid orifice** (right AV orifice) — guarded by tricuspid valve - **Pulmonary orifice** — guarded by pulmonary valve #### Trabeculae Carneae (3 types): 1. Ridges (fixed elevations) 2. Bridges 3. **Papillary muscles** (pillars) — attached to ventricular wall at one end; other end → chordae tendineae → tricuspid valve cusps - **Anterior**: largest - **Posterior/inferior**: small, irregular - **Septal**: number of small nipples - Each papillary muscle attached to contiguous sides of **two cusps** #### Septomarginal Trabecula (Moderator Band) - Muscular ridge from ventricular septum to base of anterior papillary muscle - Contains **right branch of AV bundle** #### Key Facts: - Cavity = **crescentic** in section (due to IVS bulging forward) - Wall thickness ratio RV:LV = **1:3** ### Interventricular Septum (IVS) - Placed obliquely: one surface faces forwards+right; other faces backwards+left - **Membranous part** (upper): thin; separates both ventricles + RA from LV - **Muscular part** (lower): thick; separates two ventricles; indicated by anterior + posterior IVGs --- ## 9. LEFT ATRIUM (LA) **Position**: Quadrangular; posterior. Receives oxygenated blood from 4 pulmonary veins; pumps to LV via mitral orifice. ### External Features - Left auricle projects anteriorly to overlap infundibulum of RV - Forms left 2/3rd of base; greater part of upper border; parts of sternocostal, left surfaces, left border - Posterior surface = anterior wall of **oblique sinus of pericardium** ### Internal Features - Anterior wall = interatrial septum; shows **fossa lunata** (= fossa ovalis of RA) - Posterior wall: two pulmonary veins on each side - Greater part: **smooth walled** (derived from absorbed pulmonary veins) - **Musculi pectinati** only in auricle (as reticulum); this part from primitive atrial chamber - Additional tributaries: venae cordis minimae ### RA vs LA Comparison | Feature | Right Atrium | Left Atrium | |---------|-------------|-------------| | Receives | Venous blood | Oxygenated blood from lungs | | Pushes to | RV (via tricuspid) | LV (via bicuspid/mitral) | | Forms | Right border, part of sternocostal + small part of base | Major part of base | | Enlarged in | Tricuspid stenosis | Mitral stenosis | --- ## 10. LEFT VENTRICLE (LV) **Position**: Receives oxygenated blood from LA; pumps into aorta. Forms apex, part of sternocostal surface, most of left border + left surface, left 2/3rd of diaphragmatic surface. ### Internal Features #### Two Parts: - **Lower rough part**: with trabeculae carneae; from primitive ventricle of heart tube - **Upper smooth part (aortic vestibule)**: gives origin to ascending aorta; from **midportion of bulbus cordis**; between membranous IVS and anterior/aortic cusp of mitral valve #### Two Orifices: - **Mitral orifice** — guarded by mitral (bicuspid) valve - **Aortic orifice** — guarded by aortic valve #### Key Facts: - **Two well-developed papillary muscles**: anterior + posterior - Chordae tendineae from BOTH muscles attached to BOTH cusps of mitral valve - Cavity = **circular** in cross-section - Walls = **3× thicker** than RV ### RV vs LV Comparison | Feature | RV | LV | |---------|----|----| | Wall thickness | Thinner (1/3 of LV) | Much thicker (3×) | | Pushes blood to | Lungs only | Top of body to toes | | Papillary muscles | 3 small | 2 strong | | Cavity shape | Crescentic | Circular | | Contains | Deoxygenated blood | Oxygenated blood | | Sternocostal surface | 2/3rd | 1/3rd | | Diaphragmatic surface | 1/3rd | 2/3rd | --- ## 11. VALVES OF THE HEART ### Two Pairs: 1. **Atrioventricular valves**: tricuspid (3 cusps) + mitral/bicuspid (2 cusps) 2. **Semilunar valves**: aortic + pulmonary (each with 3 semilunar cusps) ### Atrioventricular Valves — Components - **Fibrous ring**: for attachment of cusps - **Cusps**: folds of endocardium + intervening fibrous tissue layer - Flat; project into ventricular cavity - Attached margin + free margin; atrial surface (smooth) + ventricular surface (rough, irregular) - Free margins and ventricular surfaces rough due to chordae tendineae attachment - **Chordae tendineae**: connect free margins + ventricular surfaces of cusps to papillary muscle apices - Prevent eversion of free margins + limit ballooning toward atrium #### Tricuspid Valve: - 3 cusps: **anterior** (largest), **posterior/inferior**, **septal** - Papillary muscles: anterior (largest), inferior (smaller, irregular), septal (multiple small elevations) #### Mitral/Bicuspid Valve: - 2 cusps: **large anterior/aortic cusp** + **small posterior cusp** - Anterior cusp lies between mitral and aortic orifices - Mitral cusps: smaller and thicker than tricuspid #### Key Notes: - Valves **closed during ventricular systole** by apposition of atrial surfaces near serrated margins - AV valves competent due to active contraction of papillary muscles pulling chordae tendineae - Blood vessels: only in fibrous ring + basal 1/3rd; central 2/3rd nourished directly from blood in cavity ### Semilunar Valves (Aortic + Pulmonary) - Both similar; 3 semilunar-shaped cusps each - Free margin of each cusp has central **fibrous nodule** + thin smooth **lunule** on each side - **Closed during ventricular diastole** (each cusp bulges toward ventricular cavity) - Vessel walls opposite cusps slightly dilated = **aortic/pulmonary sinuses** - Coronary arteries arise from **anterior** and **left posterior aortic sinuses** ### Clinical — Valve Pathologies | Condition | Meaning | |-----------|---------| | Stenosis | Narrowing of valve orifice due to cusp fusion | | Incompetence/Regurgitation | Dilatation of orifice or stiffening of cusps → back-flow | | Valvuloplasty | Surgical valve replacement | **Heart Sounds**: - **1st sound (LUB)**: closure of AV valves - **2nd sound (DUB)**: closure of semilunar valves --- ## 12. FIBROUS SKELETON OF HEART ### Components: 1. **Four fibrous rings**: surrounding 2 AV orifices + aortic + pulmonary orifices 2. **Tendon of infundibulum**: fibrous septum connecting pulmonary ring to aortic ring 3. **Right fibrous trigone** (*trigonum fibrosum dextrum*): where right + left AV rings fuse 4. **Left fibrous trigone** (*trigonum fibrosum sinistrum*): where aortic + left AV rings fuse > AV fibrous rings are in the form of the **figure of 8**. No muscular continuity between atria + ventricles across rings — conducting system required. Only connection via AV bundle. ### Functions: 1. **Support**: attachment to cardiac musculature 2. **Discontinuity**: separates atrial and ventricular musculature → conducting system needed 3. **Maintains valvular function**: supports cusps, maintains unidirectional blood flow --- ## 13. CONDUCTING SYSTEM ### Parts: 1. **SA node** (Keith-Flack) 2. **AV node** (Tawara) 3. **AV bundle of His** → right and left branches 4. **Subendocardial plexus of Purkinje fibres** ### SA Node (Pacemaker) - Horseshoe-shaped - Location: **upper part of sulcus terminalis**, just below opening of SVC - Rate: **70-100 beats/min** - Initiates heartbeat ### AV Node - Smaller than SA node - Location: **lower part of atrial septum**, just above opening of coronary sinus (apex of Triangle of Koch) - Rate: **40-60 beats/min** ### AV Bundle (Bundle of His) - ONLY muscular connection between atrial + ventricular musculature - Begins as AV node → crosses AV ring → descends along posteroinferior border of membranous IVS - At upper border of muscular septum → divides into right and left branches: - **Right branch**: down right side of IVS → large part enters **moderator band** → reaches anterior wall of RV → Purkinje fibres - **Left branch**: descends on left side of IVS → distributed to LV → Purkinje fibres ### Purkinje Fibres - Form subendocardial plexus - Large pale fibres; striated only at margins - Usually possess **double nuclei** - Rate: **20-35 beats/min** ### Blood Supply of Conducting System - **Right coronary artery**: supplies whole conducting system **except** left branch of AV bundle - **Left coronary artery**: supplies SA node in **40%** of individuals ### Internodal Tracts (SA → AV node) | Tract | Connection | Route | |-------|-----------|-------| | **Anterior (Bachmann)** | Anterosuperior SA → AV node | In front of SVC → along interatrial septum | | **Middle (Wenckebach)** | Posteroinferior SA → AV node | Behind orifice of SVC → along interatrial septum | | **Posterior (Torel)** | Posteroinferior SA → AV node | Along crista terminalis + valve of IVC | ### Clinical Points | Term | Definition | |------|-----------| | Sinus rhythm | SA node as pacemaker; 70 beats/min | | Tachycardia | Rapid pulse / increased heart rate | | Bradycardia | Slow pulse / decreased heart rate | | Arrhythmia | Irregular heart rate | | Palpitation | Consciousness of one's heartbeat | | Heart block | Loss of blood supply to AV node/bundle of His → ventricles dissociated from SA node; atria contract at 70/min, ventricles at 25-30/min | --- ## 14. ARTERIES SUPPLYING THE HEART (CORONARY ARTERIES) ### General Features 1. Blood flows through coronary arteries during **diastole** 2. Left coronary is **larger** in calibre; supplies more myocardium 3. Functionally **end arteries** (anastomose but cannot compensate for each other in thrombosis) 4. Dominance determined by artery giving **posterior interventricular artery** 5. Sympathetic stimulation: **dilates** intramuscular arteries; **constricts** epicardial arteries 6. Prone to **atherosclerosis** --- ### RIGHT CORONARY ARTERY (RCA) **Origin**: Anterior aortic sinus (ascending aorta) **Course**: - **1st segment**: Passes forwards + right → between root of pulmonary trunk + right auricle → down right anterior coronary sulcus to junction of right + inferior borders - **2nd segment**: Winds round inferior border → diaphragmatic surface → runs backwards + left in **right posterior coronary sulcus** → crux of heart - **Terminates**: Anastomoses with circumflex branch of LCA at crux (60%) **Branches**: | Branch | Supply | |--------|--------| | Atrial branches (anterior, posterior, lateral) | Right atrium; **SA nodal artery** (from RCA in 60%, from circumflex LCA in 40%) | | Right conus artery | Forms *annulus of Vieussens* with similar branch from LCA around pulmonary trunk | | Ventricular branches | Sternocostal surface (anterior group); diaphragmatic surface (posterior group) | | Right marginal artery | Along inferior border to apex | | Posterior interventricular branch | In posterior IVG; gives septal branches (posteroinferior 1/3rd of IVS), nodal branch (AV node, 60%), ventricular branches | **Area of Distribution**: - Right atrium - Greater part of RV (except near anterior IVG) - Small part of LV near posterior IVG - Posterior 1/3rd of IVS - Whole conducting system **except** part of left branch of AV bundle --- ### LEFT CORONARY ARTERY (LCA) **Origin**: Left posterior aortic sinus (ascending aorta); **larger** than RCA **Course**: - Runs forwards + left → emerges between pulmonary trunk + left auricle - Here gives **anterior interventricular branch** (continues in groove) - Continuation = **circumflex artery** **Anterior Interventricular Artery (LAD — Left Anterior Descending)**: - Descends along anterior IVG - Turns around inferior heart border → enters posterior IVG → anastomoses with posterior IVA **Circumflex Artery**: - Runs left in left anterior coronary sulcus - Winds round left border → left posterior coronary sulcus - Terminates by anastomosing with RCA near posterior IVG **Branches**: *LAD (Anterior interventricular artery)*: | Branch | Supply | |--------|--------| | Anterior ventricular branches | Sternocostal surface of RV + LV | | Diagonal artery | Largest anterior ventricular artery | | Left conus artery | Pulmonary conus | | Septal branches | Anterior 2/3rd of IVS | *Circumflex artery*: | Branch | Supply | |--------|--------| | Ventricular branches | Stercocostal, left, inferior surfaces of LV | | Atrial branches | Adjacent left atrium | | SA nodal artery | SA node in 40% individuals | | Left marginal artery | Runs along left heart border toward apex | | Posterior interventricular artery | Circumflex continues as posterior IVA in 10-20% | | Kugel's artery | Atrial branch; anastomoses with similar branch of RCA along anterior wall of atria | **Area of Distribution**: - Left atrium - Greater part of LV (except near posterior IVG) - Small part of RV near anterior IVG - Anterior 2/3rd of IVS - Part of left branch of AV bundle --- ### CARDIAC DOMINANCE | Type | Artery giving posterior IVA | |------|---------------------------| | Right dominant (usual) | Right coronary artery | | Left dominant (~10%) | Circumflex artery of LCA | --- ### ANASTOMOSES OF CORONARY ARTERIES #### Interarterial - In IVS - Kugel's arteries near crux - **Annulus of Vieussens** around pulmonary trunk - Better in older persons #### Arteriovenous - Blocked artery blood flows back into veins → coronary sinus - Coronary branches → sinusoids → coronary sinus - Venae cordis minimi open directly into right-sided chambers #### Extracardiac Anastomoses (with): 1. Vasa vasorum of aorta 2. Vasa vasorum of pulmonary arteries 3. Internal thoracic arteries 4. Bronchial arteries 5. Pericardiacophrenic arteries *(Last 3 anastomose through pericardium; may open up when both coronary arteries obstructed)* --- ## 15. VEINS OF THE HEART **Most drain into Coronary Sinus**; anterior cardiac veins + venae cordis minimae drain directly into RA. ### Coronary Sinus - Largest vein; in **left posterior coronary sulcus**; about **2-3 cm** long - Ends in posterior wall of **right atrium** ### Tributaries of Coronary Sinus: | Vein | Accompanies | Drains | |------|-------------|--------| | **Great cardiac vein** | Anterior IVA then circumflex artery | Left end of coronary sinus; receives left marginal vein | | **Middle cardiac vein** | Posterior IVA | Middle part of coronary sinus | | **Small cardiac vein** | Right coronary artery (right posterior coronary sulcus) | Right end of coronary sinus | | **Posterior vein of LV** | Diaphragmatic surface of LV | Coronary sinus | | **Oblique vein of LA (Marshall)** | Posterior surface of LA | Left end of coronary sinus; develops from left common cardinal vein (duct of Cuvier) | ### Draining Directly into RA: - **Right marginal vein**: accompanies marginal branch of RCA; may drain into small cardiac vein or directly to RA - **Anterior cardiac veins**: 3-4 small veins on anterior wall of RV - **Venae cordis minimae (Thebesian veins)**: valveless; numerous; present in all 4 chambers; more on right side > **Clinical**: Venae cordis minimae more numerous on right side — may explain why left-sided infarcts are more common. --- ## 16. LYMPHATICS OF HEART - Accompany coronary arteries → form **two trunks** - **Right trunk**: ends in **brachiocephalic nodes** - **Left trunk**: ends in **tracheobronchial lymph nodes** (at bifurcation of trachea) --- ## 17. NERVE SUPPLY OF HEART ### Parasympathetic (Vagus) - **Cardioinhibitory**: slow down heart rate ### Sympathetic (T1–T5 spinal cord) - **Cardioacceleratory**: increase heart rate; dilate coronary arteries ### Cardiac Plexuses: #### Superficial Cardiac Plexus - Location: Below arch of aorta, in front of right pulmonary artery - Formed by: - Superior cervical cardiac branch of **left sympathetic chain** - Inferior cervical cardiac branch of **left vagus nerve** - Branches: To right coronary artery; communicating branch to deep cardiac plexus; communicating branch to left anterior pulmonary plexus #### Deep Cardiac Plexus - Location: In front of bifurcation of trachea; behind arch of aorta - Formed by: - All cardiac branches from all cervical + upper thoracic sympathetic ganglia - Cardiac branches of vagus + recurrent laryngeal nerves (except those forming superficial plexus) - Branches: Right + left halves → to RA + LA; right + left coronary plexuses; communicating branches to right + left anterior pulmonary plexuses ### Cardiac Pain Pathway - Pain fibres via sensory sympathetic cardiac nerves → **T1-T5 segments** of spinal cord via dorsal root ganglia (mostly left side) - Same DRG also receives from medial arm, forearm, upper front of chest → **referred pain** to these areas - MI pain referred: left side of chest (3rd-6th ICS) + medial side of left upper limb (C8, T1 distribution) --- ## 18. DEVELOPMENTAL COMPONENTS | Structure | Derived From | |-----------|-------------| | Rough part of RA + right auricle | Right half of primitive atrium | | Smooth part of RA (sinus venarum) | Sinus venosus | | Crista terminalis, valve of IVC, valve of coronary sinus | Right venous valve | | Small ventral smooth part of RA | Right half of AV canal | | Anterior rough part of LA + left auricle | Left half of primitive atrium | | Posterior smooth part of LA | Absorption of pulmonary veins | | Ventral smooth part of LA | Left half of AV canal | | Rough part of RV | Proximal portion of bulbus cordis | | Smooth part of RV (infundibulum) | Conus cordis (middle bulbus cordis) | | Rough part of LV | Primitive ventricular chamber | | Smooth part of LV (aortic vestibule) | Conus cordis (middle bulbus cordis) | | Fossa ovalis | Septum primum | | Limbus fossa ovalis | Septum secundum | | Muscular IVS | Muscular ridge on floor of bulboventricular cavity | | Bulbar part of IVS | Right + left bulbar ridges from conus cordis | | Membranous IVS | Proliferation of AV cushion | | Ascending aorta + pulmonary trunk | Truncus arteriosus / distal bulbus cordis (separated by spiral septum) | > Heart fully functional by end of **2nd month** of intrauterine life. --- ## 19. CONGENITAL HEART DEFECTS ### Atrial Septal Defect (ASD) - Normally septum primum + secundum fuse → obliterate interatrial foramen - Incomplete fusion → ASD ### Ventricular Septal Defect (VSD) - Defect in formation of **membranous part** of IVS - Membranous IVS formed by: right + left bulbar ridges + proliferating posterior endocardial cushion - Improper fusion of these three → VSD - Membranous IVS of **neural crest origin** ### Fallot's Tetralogy **4 components** (mnemonic PROV): 1. **P** = Pulmonary stenosis 2. **R** = Right ventricular hypertrophy 3. **O** = Overriding of aorta 4. **V** = patent interventricular foramen (VSD) --- ## 20. ISCHAEMIC HEART DISEASE ### Classification (by severity): 1. Angina pectoris (stable and unstable) 2. Myocardial infarction 3. Heart failure 4. Arrhythmias 5. Sudden cardiac death ### Angina Pectoris - Pain: heavy, tight, gripping; typically **retrosternal**; referred to left shoulder + medial side of arm/forearm - Cause: transient (15 sec-15 min) myocardial ischemia — no necrosis - **Stable angina**: begins on exercise/physical activity - **Unstable angina**: occurs at rest; lasts > 20 minutes - Relief: **sorbitrate tablets** sublingually ### Myocardial Infarction (MI / Heart Attack) - Sudden occlusion of coronary artery branch → infarction → necrosis - Symptoms: prolonged angina (> 30 min), nausea/vomiting, shortness of breath, sweating **Commonly involved vessels**: | Vessel | Frequency | |--------|----------| | LAD (anterior IVA) | 40-50% | | Right coronary artery | 30-40% | | Left circumflex | 15-20% | ### Interventions | Procedure | Indication | |-----------|-----------| | Coronary angiography | Determines site of narrowing/occlusion | | Angioplasty + stent | Small blockage; catheter via femoral artery → aorta → coronary artery | | CABG (Coronary Artery Bypass Grafting) | Large/multiple segments; using great saphenous vein or **internal thoracic artery** as graft | --- ## 21. KEY MEMORY POINTS (PEARLS) - **Crux of heart** = meeting of interatrial + AV + posterior IVG - **Triangle of Koch** = bounded by coronary sinus ostium + septal leaflet of tricuspid + tendon of Todaro → **AV node at apex** - **Moderator band** = carries right branch of AV bundle - **SA node** = "pacemaker" (70-100/min); horseshoe shaped; in sulcus terminalis - **AV node** = 40-60/min; just above coronary sinus opening; in Triangle of Koch - **Purkinje fibres** = 20-35/min; double nuclei; large pale fibres - **Right coronary** = supplies whole conducting system except left branch of AV bundle; SA node in 60% - **Left coronary** = larger; supplies more myocardium; SA node in 40% - **LAD** = supplies anterior 2/3rd of IVS; most commonly blocked in MI (40-50%) - **Cardiac dominance** = determined by which artery gives posterior IVA (right dominant in majority) - **Mitral stenosis** → LA enlarges → compresses oesophagus → **dysphagia** - **Pericardial effusion** → cardiac tamponade → compresses cardiac chambers during diastole → ↓ cardiac output - **Coronary arteries** are **functional end arteries** (anastomose but cannot compensate in acute occlusion) - **Wall thickness ratio** = RV:LV = 1:3 - **Cavity shape**: RV = crescentic; LV = circular - **Oblique vein of LA (Marshall)** develops from duct of Cuvier (left common cardinal vein) - **Venae cordis minimae** more numerous on right side → left-sided infarcts more common --- ## 22. DIAGRAM REFERENCES (BD Chaurasia Vol 2 — Chapter 18) > Since BD Chaurasia Vol 4 (Head, Neck & Brain) is not relevant for heart anatomy, the diagrams referenced below are from **BD Chaurasia Vol 2 (Thorax)**, Chapter 18. The figures listed below correspond to diagrams in the original text: | Figure | Content | |--------|---------| | Fig. 18.1 | Pericardium layers | | Fig. 18.4/18.5 | Transverse and oblique sinuses of pericardium | | Fig. 18.11 | Gross features: sternocostal surface of heart; grooves; apex | | Fig. 18.12 | Site of apex impulse and apex beat | | Fig. 18.13 | Dextrocardia | | Fig. 18.14 | Base/posterior surface of heart | | Fig. 18.15 | Interior of right atrium (cut along sulcus terminalis) | | Fig. 18.16 | Heart: Lines of incision for dissection | | Fig. 18.17 | Interior of right ventricle (moderator band + supraventricular crest) | | Fig. 18.18 | Transverse section through ventricles (AV orifices, papillary muscles, pulmonary + aortic orifices) | | Fig. 18.19 | Interior of left atrium + left ventricle | | Fig. 18.20 | Structure of AV/tricuspid valve | | Fig. 18.21 | Structure of mitral valve | | Fig. 18.22 | Structure of aortic valve | | Fig. 18.24 | Heart from above (fibrous skeleton — tricuspid, mitral, aortic, pulmonary orifices) | | Fig. 18.25 | Conducting system of the heart | | Fig. 18.28 | Arterial supply of heart | | Fig. 18.29 | Origin of coronary arteries from aortic sinuses | | Fig. 18.30 | Transverse section of ventricles: areas supplied by two coronary arteries | | Fig. 18.32 | Pain of angina pectoris (referred pain areas) | | Fig. 18.35a/b | Veins of the heart (sternocostal surface + posteroinferior view) | | Fig. 18.36 | Superficial and deep cardiac plexuses | | Plate 18.4 | External features of heart | | Plate 18.5 | Posteroinferior view of heart | | Plate 18.6 | Borders of heart | | Plate 18.7 | Interior of right atrium | | Plate 18.8 | Internal view of right ventricle | | Plate 18.9 | Interior of left atrium + left ventricle | | Plate 18.10 | Tricuspid and mitral valves | | Plate 18.11 | Aortic valve | | Plate 18.12 | Conducting system of heart | | Plate 18.13 | Branches of coronary artery | | Plate 18.14 | Principal veins of the heart | | Flowchart 18.3 | External features of heart | | Flowchart 18.4 | Systemic vs pulmonary circulation | | Flowchart 18.5 | Right atrium features | | Flowchart 18.6 | Right ventricle features | | Flowchart 18.7 | Left ventricle features | | Flowchart 18.8 | Coronary arteries | | Flowchart 18.9 | Venous drainage of heart | | Flowchart 18.10 | Nerve supply of heart | --- *Source: BD Chaurasia's Human Anatomy, Vol. 2 — Thorax, Chapter 18: Heart and Pericardium* ENDOFNOTES echo "File written successfully" ls -la /tmp/workspace/heart-notes/