---

Infective Endocarditis

---

Definition & The Lesion

• The low-pressure side of a ventricular septal defect
• Mural endocardium (damaged by aberrant jets or foreign bodies)
• Intracardiac devices (pacemakers, defibrillators, CIEDs)

---

Classification

---

Epidemiology

• Incidence: ~15 cases per 100,000 population/year in developed countries (rising)
• USA: ~10,000–20,000 new cases/year
• ~25–35% of NVE cases are health care-associated in developed countries
• 16–30% of all cases are prosthetic-valve infections
• Recent acceleration in mortality in ages 25–44 years, linked to opioid use disorder and injection drug use
• S. aureus is now the most common causative organism in developed countries

---

Predisposing Conditions

• Mitral valve prolapse (especially with regurgitation)
• Degenerative valvular disease
• Injection drug use
• Congenital heart disease (uncorrected VSD)
• Previous endocarditis

• Rheumatic heart disease
• Hypertrophic obstructive cardiomyopathy (HOCM)
• Coarctation of the aorta
• Complex cyanotic congenital heart disease

---

Etiology & Microbiology

• Early PVE (<2 months): S. aureus dominates — perioperative contamination
• Late PVE (>2 months): spectrum resembles community-acquired NVE (S. aureus, viridans streptococci); oxacillin-resistant coagulase-negative staphylococci common

---

Clinical Features

Symptoms

• Fever (most common), rigors, night sweats, malaise, anorexia, weight loss
• New or worsening cardiac murmur (critical finding)
• Symptoms of heart failure in severe cases

Peripheral Manifestations (embolic/immunologic)

Neurological Complications

• 15–20% of patients develop stroke or stroke-like symptoms
• Major vessel embolism, cranial nerve palsies, visual field defects, toxic-metabolic encephalopathy

---

Diagnosis

Modified Duke Criteria (the clinical gold standard)

1. Positive blood cultures — typical organisms (S. aureus, viridans streptococci, HACEK, S. gallolyticus, enterococci) from ≥2 separate cultures; or persistently positive cultures; or single positive for Coxiella burnetii (Q fever)
2. Evidence of endocardial involvement — positive echocardiogram (vegetation, abscess, new partial dehiscence of prosthetic valve) OR new valvular regurgitation

1. Predisposing heart condition or injection drug use
2. Fever ≥38°C
3. Vascular phenomena (arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, Janeway lesions)
4. Immunologic phenomena (glomerulonephritis, Osler nodes, Roth spots, positive rheumatoid factor)
5. Microbiologic evidence not meeting major criteria
6. Echocardiographic findings not meeting major criteria

• Definite IE: 2 major, or 1 major + 3 minor, or 5 minor criteria
• Possible IE: 1 major + 1 minor, or 3 minor criteria
• Rejected: firm alternative diagnosis, resolution with ≤4 days antibiotics, or no pathologic evidence at surgery/autopsy

Blood Cultures

• Obtain ≥3 sets from separate sites (aerobic + anaerobic each) before starting antibiotics
• In stable/subacute patients — defer empirical therapy until cultures obtained
• In sepsis/haemodynamic compromise — culture first, then treat immediately

Non-culture Diagnostics (Duke-ISCVID 2023 updates)

• PCR/nucleic acid testing from blood for C. burnetii, Bartonella spp., Tropheryma whipplei — major criterion
• Indirect immunofluorescence IgG ≥1:800 for Bartonella — major criterion
• Next-generation (shotgun metagenomic) sequencing — promising but currently only minor criterion for non-standard organisms

Echocardiography

---

Complications

• Heart failure — most common indication for surgery; due to valve destruction
• Perivalvular extension — abscess, fistula, pseudoaneurysm (especially aortic valve)
• Embolic events — stroke (15–20%), systemic emboli (spleen, kidney, coronary arteries)
• Mycotic aneurysms — from seeding of arterial walls
• Metastatic infection — septic arthritis, osteomyelitis, epidural abscess, splenic abscess
• Immune complex disease — glomerulonephritis, Osler nodes, Roth spots
• Conduction abnormalities — new PR prolongation suggests perivalvular abscess

---

Treatment

Antimicrobial Principles

• Bactericidal agents are required (not bacteriostatic)
• Parenteral therapy for full course in most cases
• Duration: typically 4–6 weeks (2 weeks for selected low-risk NVE)
• Synergistic combinations often used (e.g., β-lactam + aminoglycoside)
• A multispecialty IE team (cardiologist, cardiac surgeon, infectious disease specialist) is recommended

Empirical Therapy (pending cultures)

• Stable/subacute: withhold antibiotics until ≥3 blood culture sets collected
• Unstable: start after blood cultures — broad-spectrum cover including S. aureus

Organism-Specific Therapy (summary)

Surgical Indications

• Heart failure due to valve dysfunction
• Fungal or highly resistant organism endocarditis
• Perivalvular extension (abscess, fistula, large vegetation with high embolic risk)
• Persistent bacteraemia/fever despite optimal antibiotic therapy (>5–7 days)
• PVE with dehiscence

• Recurrent emboli on antibiotic therapy
• Large vegetations (>10 mm) with embolic events

---

Prophylaxis

• Prosthetic valves (surgical or transcatheter)
• Previous IE
• Certain congenital heart diseases (unrepaired cyanotic CHD; repaired CHD with residual defects; repaired CHD with prosthetic material within 6 months)
• Cardiac transplant recipients with valvular disease

---

Prognosis

• In-hospital mortality: ~15–25%
• Higher mortality with: S. aureus, prosthetic valve involvement, aortic valve involvement, heart failure, perivalvular abscess, neurological complications, older age
• Injection drug user right-sided IE (S. aureus/tricuspid valve): better prognosis, mortality ~<10%
• Relapse rate after cure: ~5% for NVE, higher for PVE

---

Note: Davidson's Principles and Practice of Medicine is not available in the textbook library. This summary is compiled from Harrison's Principles of Internal Medicine, 22nd edition (2025) and Goldman-Cecil Medicine, which provide equivalent and current coverage of IE. The content reflects the updated Duke-ISCVID 2023 criteria and contemporary management.

---

Note: AK Khurana's Comprehensive Ophthalmology is not in the library. The content below is drawn from Kanski's Clinical Ophthalmology, 10th Edition — the most authoritative and comprehensive ophthalmology textbook available — which covers all the same topics in equivalent depth.

---

Cataract

---

Introduction & The Lens

• Zonules hold the lens in position
• Capsule — acellular membrane enclosing all lens material
• Epithelial cells — cuboid, beneath the anterior capsule; cells in the germinative zone divide continuously and differentiate to form lens fibres
• Lens substance — central nucleus surrounded by cortex

---

Symptoms (Effects on Vision)

• Reduced visual acuity (may initially be correctable with spectacles)
• Loss of contrast sensitivity
• Change in colour perception — difficulty perceiving blue colours
• Glare from light scattering — particularly night driving difficulty
• Monocular diplopia — especially when looking at a point source
• Poor night vision / difficulty in low-light situations

---

ACQUIRED CATARACT

Age-Related (Senile) Cataract

1. Posterior Subcapsular Cataract

• Lies just in front of the posterior capsule
• Granular or plaque-like appearance on oblique slit-lamp biomicroscopy
• Appears black and vacuolated on retroillumination
• Vacuoles are swollen migratory lens epithelial cells (bladder/Wedl cells)
• Due to its location at the nodal point of the eye → profound effect on vision even when small
• Characteristically: glare (worse with car headlights), symptoms worsen with miosis (near vision, bright sunlight)

2. Nuclear Sclerotic Cataract

• Exaggeration of normal ageing change
• Associated with myopia (increased refractive index of nucleus) → "second sight of the aged" — patient can read without glasses again
• Characterized by yellowish hue due to urochrome pigment deposition — best assessed with oblique slit-lamp beam
• Advanced: nucleus appears brown (brunescent), rarely black
• Good red reflex on retroillumination; subtle nucleus-cortex distinction visible

3. Cortical Cataract

• Involves anterior, posterior, or equatorial cortex
• Opacities start as clefts and vacuoles from cortical hydration
• Progress to typical cuneiform (wedge-shaped) or radial spoke-like opacities
• Often begin in the inferonasal quadrant
• Glare is a common symptom

4. Christmas Tree Cataract

• Uncommon
• Polychromatic needle-like formations in the deep cortex and nucleus

---

Cataract Maturity

---

Cataract in Systemic Disease

---

Secondary (Complicated) Cataract

---

Traumatic Cataract

• Blunt trauma → rosette-shaped opacity (posterior subcapsular or axial)
• Penetrating trauma → lens material exposed → rapid opacification
• Electric shock → anterior subcapsular opacification
• Radiation (infrared/ionizing) → posterior subcapsular

---

MANAGEMENT OF ACQUIRED CATARACT

Indications for Surgery

• Functional: when cataract causes sufficient visual disability to affect the patient's activities
• No objective acuity threshold mandates surgery — patient's needs and wishes guide timing
• Surgery should not be delayed until the cataract is "ripe"

Preoperative Assessment

• Visual acuity (Snellen chart)
• Cover test — exclude amblyopia (guarded prognosis) or risk of postoperative diplopia
• Pupillary responses — cataract never produces an RAPD; its presence implies posterior pole pathology
• Exclude dacryocystitis, blepharitis, ectropion (infection risk → endophthalmitis)
• Corneal endothelial count — cornea guttata → risk of decompensation; specular microscopy + pachymetry
• Anterior chamber depth — shallow AC → difficult surgery
• Pupil dilation — poorly dilating pupil needs planning (mydriatic drops, intracameral agents, iris hooks)
• Lens: nuclear cataracts = hard (more phaco power); black nuclei may need ECCE
• Pseudoexfoliation → weak zonules (phako-donesis), fragile capsule, poor mydriasis
• Fundus examination — AMD may limit visual outcomes; ultrasonography if fundus not visible

Surgical Techniques

1. Intracapsular Cataract Extraction (ICCE) — Historical

• Cryoprobe removes entire lens with capsule
• Largely abandoned; reserved for subluxated lenses

2. Extracapsular Cataract Extraction (ECCE)

• Large anterior capsulotomy → large limbal incision (8–10 mm) → nucleus expressed → cortex aspirated → IOL in capsular bag
• Requires suturing → can induce significant corneal astigmatism
• Still used for very dense/black nuclei

3. Manual Small-Incision Cataract Surgery (MSICS)

• Variant of ECCE for high-volume, resource-limited settings
• Small self-sealing sclerocorneal tunnel; no suturing required
• Comparable visual outcomes to phaco; faster and cheaper

4. Phacoemulsification (Standard in high-income countries)

• Ultrasound energy emulsifies the nucleus through a small (~2.5 mm) incision
• Phacodynamics:
  • Irrigating bottle height — maintains AC pressure
  • Aspiration flow rate (AFR) — volume removed per minute; high AFR = faster but riskier (surge)
  • Vacuum — determines grip on lens material; high vacuum → less power needed
  • Post-occlusion surge — sudden outflow when occlusion breaks → capsular rupture risk

1. Clear corneal incision (main + side-port)
2. Viscoelastic injection
3. Continuous curvilinear capsulorhexis (CCC) — circular anterior capsule opening
4. Hydrodissection + hydrodelineation
5. Nuclear disassembly (divide and conquer / stop and chop / phaco chop)
6. Cortical aspiration
7. IOL implantation in capsular bag
8. Wound hydration/sealing

Intraocular Lenses (IOL)

---

CONGENITAL CATARACT

Epidemiology

• Occurs in ~3 in 10,000 live births
• 1/3 associated with systemic disease, 1/3 inherited, 1/3 unknown
• 2/3 are bilateral
• Autosomal dominant (AD) is the most common inherited form
• Unilateral cataracts: usually sporadic, otherwise healthy infants

Aetiology

Morphological Types

• Blue dot (cerulean) — tiny blue-white opacities; usually visually insignificant
• Nuclear — dense central opacity
• Coronary — peripheral spoke-like opacities around nucleus
• Lamellar (zonular) — affects a specific lamella with radial 'riders'; most common visually significant type
• 'Oil droplet' — central droplet appearance; characteristic of galactosaemia
• Sutural — follows anterior or posterior Y suture; seen in Nance-Horan carriers
• Anterior polar — flat or projects into AC; associations: persistent pupillary membrane, aniridia, Peters anomaly
• Posterior polar — closely integrated with posterior capsule; very high surgical risk of dehiscence

Investigations

• Screen for intrauterine infections (all unilateral + bilateral)
• Urine for reducing substance after milk (galactosaemia); amino acids (Lowe)
• Fasting blood glucose, serum calcium/phosphorus
• Red blood cell GALT and galactokinase levels
• Chromosome analysis if dysmorphic features

Treatment

• Timing is critical — must treat early to prevent stimulus deprivation amblyopia
• Surgery before 4 weeks of age → higher risk of juvenile glaucoma
• Bilateral dense cataracts: surgery between 4–10 weeks of age
• Unilateral dense cataracts: surgery within 6–8 weeks of birth; followed by aggressive occlusion therapy (patching) of fellow eye to treat amblyopia
• IOL implantation: deferred until ~2 years of age in most centres (aphakic contact lens in the interim)
• Optical correction + amblyopia treatment must continue post-operatively

---