STEMI vs NSTEMI
Acute coronary syndromes
▼
| Feature | STEMI | NSTEMI |
|---|---|---|
| ECG | ST elevation | ST depression / T-wave inversion / normal |
| Troponin | Elevated | Elevated |
| Occlusion | Complete | Partial |
| Urgent Rx | Primary PCI (<120 min) | Medical management first |
| Antiplatelet | Aspirin + Ticagrelor | Aspirin + Ticagrelor |
| Angiography | Immediate | Within 72h (or sooner if high risk) |
| Thrombolysis | If PCI not available | NOT indicated |
💡 Key point: Both have raised troponin. The difference is the ECG. STEMI = ST elevation = emergency PCI. NSTEMI = no ST elevation = medical management first.
Left vs Right Heart Failure
Different sides, different symptoms
▼
| Feature | Left Heart Failure | Right Heart Failure |
|---|---|---|
| Cause | IHD, hypertension, aortic/mitral valve | Left HF (most common), COPD, PE, pulm HTN |
| Congestion | Pulmonary (lungs) | Systemic (body) |
| Symptoms | Breathlessness, orthopnoea, PND, cough | Ankle oedema, ascites, hepatomegaly, raised JVP |
| Signs | Bibasal crackles, S3 gallop, tachycardia | Pitting oedema, hepatomegaly, raised JVP |
| CXR | Pulmonary oedema, cardiomegaly, effusions | May be normal |
💡 Remember: Left = Lungs. Right = Rest of body. Most common cause of right HF is left HF.
Asthma vs COPD
Obstructive airway diseases
▼
| Feature | Asthma | COPD |
|---|---|---|
| Age | Young (<40) | Older (>40) |
| Smoking | Not always | Almost always |
| Reversibility | Fully reversible | Partially reversible |
| FEV1/FVC | <0.7 (reversible with bronchodilator) | <0.7 (persistent) |
| Diurnal variation | Yes (worse morning/night) | No |
| Atopy | Common (eczema, hayfever) | Uncommon |
| First-line | SABA + low-dose ICS | SABA/SAMA PRN → LABA/LAMA |
| O2 target | 94-98% | 88-92% |
⚠️ COPD patients: Target SpO2 88-92%. High-flow O2 can suppress respiratory drive and worsen CO2 retention.
Type 1 vs Type 2 Diabetes
Different causes, different management
▼
| Feature | Type 1 | Type 2 |
|---|---|---|
| Cause | Autoimmune beta cell destruction | Insulin resistance + relative deficiency |
| Age | Young (<30 usually) | Older (>40, increasingly younger) |
| Onset | Acute (days-weeks) | Gradual (months-years) |
| Weight | Often thin/normal | Often overweight/obese |
| Ketosis | Common (DKA) | Rare (HHS instead) |
| C-peptide | Low/absent | Normal/high |
| Antibodies | GAD, IA-2, ZnT8 | None |
| Treatment | Insulin (always, lifelong) | Metformin → add agents → insulin |
💡 Key point: T1DM = absolute insulin deficiency (autoimmune). T2DM = insulin resistance. Both cause hyperglycaemia but management is very different.
Ischaemic vs Haemorrhagic Stroke
Critical to differentiate before treatment
▼
| Feature | Ischaemic (85%) | Haemorrhagic (15%) |
|---|---|---|
| Cause | Thrombus or embolus blocking artery | Vessel rupture (intracerebral or subarachnoid) |
| Risk factors | AF, carotid stenosis, hypertension | Hypertension, anticoagulants, AVM, aneurysm |
| Onset | Sudden focal deficit | Sudden headache + focal deficit |
| CT head | May be normal early (hypodense later) | Hyperdense (bright white) immediately |
| Treatment | Thrombolysis (alteplase <4.5h) or thrombectomy | Reverse anticoagulation, BP control, neurosurgery |
| Aspirin | 300mg after CT excludes bleed | CONTRAINDICATED |
⚠️ MUST do CT head before any treatment. Giving thrombolysis to a haemorrhagic stroke is fatal. CT first, always.
Crohn's vs Ulcerative Colitis
Inflammatory bowel diseases
▼
| Feature | Crohn's Disease | Ulcerative Colitis |
|---|---|---|
| Location | Mouth to anus (anywhere) | Rectum → colon only (continuous) |
| Pattern | Skip lesions (patchy) | Continuous inflammation |
| Depth | Transmural (full thickness) | Mucosa/submucosa only |
| Diarrhoea | Often non-bloody | Bloody diarrhoea + mucus |
| Pain | RIF pain (terminal ileum) | LIF pain, tenesmus |
| Complications | Fistulae, strictures, abscesses | Toxic megacolon, colorectal cancer |
| Histology | Granulomas, transmural inflammation | Crypt abscesses, pseudopolyps |
| Smoking | Makes it WORSE | Protective (but dont recommend!) |
| Surgery | Not curative (recurs) | Curative (colectomy) |
💡 Mnemonic: Crohn's = CHRISTMAS: Cobblestoning, High temp, RIF pain, Intestinal fistulae, Skip lesions, Transmural, Mouth-to-anus, Abscess, Strictures.
ACE Inhibitors vs ARBs
When to use which
▼
| Feature | ACE Inhibitor (-pril) | ARB (-sartan) |
|---|---|---|
| Mechanism | Blocks ACE enzyme | Blocks AT1 receptor |
| Example | Ramipril, Lisinopril | Losartan, Candesartan |
| Cough | Yes (bradykinin accumulation) | No (no effect on bradykinin) |
| Angioedema | Rare but serious | Very rare |
| Hyperkalaemia | Yes | Yes |
| First-line? | Yes (HF, diabetes, CKD) | If ACEi not tolerated (cough) |
| Pregnancy | Contraindicated | Contraindicated |
| Monitoring | U&Es before + 1-2 weeks after | Same |
💡 Key point: ACEi first-line. If dry cough → switch to ARB. Never combine ACEi + ARB (ONTARGET trial = harm).
Upper vs Lower GI Bleed
Location changes everything
▼
| Feature | Upper GI Bleed | Lower GI Bleed |
|---|---|---|
| Location | Above ligament of Treitz | Below ligament of Treitz |
| Presentation | Haematemesis, melaena, coffee-ground vomit | Fresh red blood PR, maroon stool |
| Common causes | Peptic ulcer, varices, Mallory-Weiss | Diverticulosis, colorectal cancer, haemorrhoids |
| Investigation | OGD within 24h | Colonoscopy, CT angiography |
| Scoring | Glasgow-Blatchford (pre), Rockall (post) | No standard score |
| Urea | Raised (digested blood) | Normal |
💡 Key point: Melaena (black tarry stool) = upper GI bleed. Fresh red blood PR = usually lower. Raised urea with normal creatinine = upper GI bleed.
Hypothyroid vs Hyperthyroid
Too little vs too much
▼
| Feature | Hypothyroid | Hyperthyroid |
|---|---|---|
| Cause | Hashimoto's (autoimmune), post-surgery, iodine deficiency | Graves' disease, toxic nodule, thyroiditis |
| TSH | ↑ High | ↓ Low |
| T4/T3 | ↓ Low | ↑ High |
| Weight | Weight gain | Weight loss |
| Heart rate | Bradycardia | Tachycardia, AF |
| Temperature | Cold intolerance | Heat intolerance |
| Skin | Dry, coarse, puffy | Warm, sweaty, thin |
| Mood | Depression, fatigue | Anxiety, irritability, tremor |
| Bowels | Constipation | Diarrhoea |
| Treatment | Levothyroxine (lifelong) | Carbimazole → radioiodine or surgery |
💡 Remember: Hypo = everything SLOW. Hyper = everything FAST. TSH is the first-line screening test.
Sensitivity vs Specificity
Understanding diagnostic tests
▼
| Feature | Sensitivity | Specificity |
|---|---|---|
| Question | How good at detecting disease? | How good at ruling out disease? |
| Formula | TP / (TP + FN) | TN / (TN + FP) |
| High value means | Few false negatives | Few false positives |
| Best for | Screening tests | Confirmatory tests |
| If negative | Rules OUT disease (SnNOut) | — |
| If positive | — | Rules IN disease (SpPIn) |
💡 SnNOut: High Snensitivity + Negative result = rules Out. SpPIn: High Specificity + Positive result = rules In.