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🫀 Complete Cardiovascular Pathology Lecture

(Pages 308-317 — Explained for a Non-Medical Learner)

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PAGE 308 — CORONARY ARTERY DISEASE & ANGINA

First, let's understand the basics

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ANGINA (Chest Pain)

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1. Stable Angina

"Chest pain due to ischemic myocardium 2° to coronary artery narrowing or spasm; no necrosis. Stable — usually 2° to atherosclerosis (≥70% occlusion); exertional chest pain in classic distribution resolving with rest or nitroglycerin."

• Ischemic myocardium — "ischemic" means not enough blood supply. "Myocardium" is the heart muscle. So ischemic myocardium = heart muscle being starved of blood.
• 2° to means "secondary to" or "caused by." So this chest pain is caused by...
• Atherosclerosis (≥70% occlusion) — Atherosclerosis is the build-up of fatty plaques inside artery walls, like rust building up inside a pipe. When at least 70% of the artery is blocked, enough blood still flows at rest, but during exercise (when the heart needs more fuel), it can't get enough - causing pain.
• Exertional chest pain — pain that comes ON WITH EXERCISE or exertion.
• Classic distribution — the pain typically spreads to the left arm, jaw, or shoulder (because pain signals travel along shared nerve pathways).
• Resolves with rest or nitroglycerin — When you stop exercising, demand drops, pain goes away. Nitroglycerin is a drug that dilates (widens) blood vessels, temporarily increasing blood flow.
• No necrosis — No heart muscle is dying yet. This is just a warning sign.
• No cardiac biomarker elevation — Biomarkers like Troponin are proteins that leak into the blood ONLY when heart cells die. In stable angina, no cells are dying, so no biomarkers are elevated.

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2. Unstable Angina

"Thrombosis with incomplete coronary artery occlusion; ↑ in frequency or intensity of exertional chest pain or any chest pain at rest. No cardiac biomarker elevation (vs non-ST-segment elevation MI [NSTEMI])."

• Thrombosis — a blood clot has now formed ON TOP of the atherosclerotic plaque. This makes the blockage much worse, sometimes suddenly.
• Incomplete coronary artery occlusion — the artery is not 100% blocked yet. There's still some blood getting through.
• ↑ in frequency or intensity — the chest pain is getting worse, happening more often, or now happening even at rest (not just with exercise). This is a RED FLAG - it means the disease is progressing.
• Chest pain at rest — this is dangerous. Even without any extra demand, the blood supply is so compromised that the heart can't get enough oxygen just sitting still.
• No cardiac biomarker elevation — still no cells are dying. This differentiates it from a heart attack.

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3. Vasospastic Angina (Prinzmetal or Variant Angina)

"Occurs at rest 2° to coronary artery spasm; transient ischemic ST changes on ECG. Tobacco smoking is a major risk factor. Triggers include cocaine, amphetamines, alcohol, triptans. Treat with Ca²⁺ channel blockers, nitrates, and smoking cessation (if applicable)."

• Vasospasm — "vaso" = vessel, "spasm" = sudden involuntary contraction. So the coronary artery SQUEEZES SHUT on its own (even without a blockage!). It's like someone pinching your garden hose suddenly.
• Occurs at rest — it happens when you're not exercising, often at night or early morning. This distinguishes it from stable angina.
• ST changes on ECG — the ECG (electrocardiogram - a recording of the heart's electrical activity) shows temporary abnormalities during the spasm.
• Triggers: cocaine, amphetamines, alcohol, triptans — these are all substances that can cause blood vessel spasm. Cocaine is notorious for causing coronary spasms and heart attacks even in young people with no blockages.
• Calcium channel blockers — calcium causes muscle cells (including blood vessel walls) to contract. Block the calcium, and the vessel walls relax and stop spasming. Nitrates work similarly by relaxing blood vessels.

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PAGE 308 — MYOCARDIAL INFARCTION (Heart Attack)

"Most often due to an acute coronary syndrome (ACS): rupture of coronary artery atherosclerotic plaque → acute thrombosis. MI can also occur with prolonged supply-demand mismatch (eg, stable angina → prolonged tachycardia and hypotension from pneumonia → elevated troponin but no acute plaque rupture)."

• Acute Coronary Syndrome (ACS) — umbrella term for unstable angina, NSTEMI, and STEMI. The final common event is usually a plaque rupture.
• Plaque rupture → acute thrombosis — the fatty plaque (think of it like a pimple inside the artery) suddenly BURSTS OPEN. Your body sees this as an injury and sends clotting factors. A large blood clot (thrombus) forms instantly, completely blocking the artery. Blood flow stops. Heart muscle downstream begins to die within minutes.
• Supply-demand mismatch — sometimes there's no rupture. If your heart is racing very fast (tachycardia) due to a fever/infection like pneumonia, it needs more oxygen. If at the same time your blood pressure is low (hypotension) so less blood is being pumped, the heart muscle can die from not getting enough oxygen even without a new clot. Troponin (the dying-cell marker) rises in this case too.

The Comparison Table (Stable Angina vs Unstable Angina vs NSTEMI vs STEMI)

• NSTEMI = Non-ST-Elevation Myocardial Infarction. Partial thickness heart attack. The inner layer of the heart wall (subendocardium) dies, but not the full thickness.
• STEMI = ST-Elevation Myocardial Infarction. Full thickness heart attack. The entire wall from inside to outside (transmural) dies. This is the most severe type.
• Subendocardial — "sub" = below, "endo" = inside, "cardial" = heart. So this is the layer just below the inner lining of the heart chamber.
• Transmural — "trans" = through, "mural" = wall. The whole wall is involved - all the way through.
• ST elevation / ST depression — On an ECG, your heart's electrical activity makes a wave pattern. The "ST segment" is a flat portion of that wave. When heart muscle is dying/damaged, this segment shifts up (elevation in STEMI) or down (depression in NSTEMI/unstable angina).
• T-wave inversion — the T-wave normally points up; when it flips downward, it signals ischemia.
• Pathologic Q waves — Q waves are normal in small amounts but become wide and deep (pathologic) when a full-thickness infarction leaves a scar. They represent electrically "dead" zones.

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PAGE 309 — EVOLUTION OF MYOCARDIAL INFARCTION (What happens over time after a heart attack)

Stage 1: 0-24 Hours

• Wavy fibers (0-4 hrs) — the dead muscle fibers appear wavy and stretched. This is one of the earliest signs. Normal muscle fibers are straight.
• Early coagulative necrosis (4-24 hrs) — "coagulative" means the proteins inside the cells have solidified/coagulated (like cooking an egg white). The cells are dead but their shape is still preserved for now.
• Cell content released into blood, edema, hemorrhage — as cells die and their walls break down, proteins (including troponin) spill into the bloodstream. Fluid accumulates (edema = swelling) and small bleeding (hemorrhage) occurs.
• Reperfusion injury — this is very important and counterintuitive! When you restore blood flow to a previously blocked area (with a stent or clot-busting drugs), the sudden rush of oxygen actually causes additional damage through:
  • Free radicals — highly reactive oxygen molecules that damage cell membranes (like rust damaging metal)
  • ↑ Ca²⁺ influx — calcium floods into cells suddenly
  • Hypercontraction of myofibrils (dark eosinophilic stripes) — the muscle fibers seize up violently. These appear as dark pink bands under the microscope.

• Ventricular arrhythmia — the dying tissue sends out chaotic electrical signals, disrupting the heart's rhythm. This is the #1 cause of death in the first hour.
• HF = Heart Failure. The damaged pump can no longer pump efficiently.
• Cardiogenic shock — the heart is so damaged it can't pump enough blood to maintain blood pressure. Organs start failing. This is life-threatening.

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Stage 2: 1-3 Days

• Extensive coagulative necrosis — the dead zone is now larger and more obvious.
• Acute inflammation with neutrophils — neutrophils are white blood cells, your body's first responders. They arrive to clean up dead tissue. You can see them flooding the area under the microscope.

• Pericarditis — inflammation of the pericardium (the sac surrounding the heart).
• Fibrinous — fibrin (a clotting protein) is deposited on the outer surface of the heart.
• This happens because the dead surface of the heart irritates the pericardial sac. Patients feel sharp chest pain that worsens with breathing and improves when leaning forward.

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Stage 3: 3-14 Days - THE MOST DANGEROUS PERIOD

• Macrophages, then granulation tissue at margins — macrophages (another type of immune cell, the "janitors" of the body) arrive after the neutrophils to eat up the dead debris. Granulation tissue (new scar-forming tissue with blood vessels and fibroblasts) begins forming at the edges.

1. Free wall rupture → tamponade — the softened, digested heart wall can literally TEAR OPEN. Blood pours into the pericardial sac. This is called cardiac tamponade - the sac fills with blood, compresses the heart, and it cannot beat. Rapidly fatal without emergency treatment.
2. Papillary muscle rupture → mitral regurgitation — papillary muscles are small muscles inside the heart that hold the mitral valve (a valve between two left-side chambers) in place. If they rupture, the valve flops open and blood flows backward. This is called mitral regurgitation. Acute, severe mitral regurgitation causes sudden heart failure.
3. Interventricular septal rupture due to macrophage-mediated structural degradation → left-to-right shunt — the septum is the wall between the left and right ventricles (pumping chambers). If it ruptures, blood flows from the high-pressure left side to the low-pressure right side (left-to-right shunt). This floods the lungs.
4. LV pseudoaneurysm (risk of rupture) — "pseudo" = false. This is a contained rupture where blood leaks through the wall but is held in by the adherent pericardium (the surrounding sac). Unlike a true aneurysm, a pseudoaneurysm's wall does NOT contain any heart muscle layers - just scar/pericardium. High risk of complete rupture.

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Stage 4: 2 Weeks to Several Months — HEALING

1. Postcardiac injury syndrome (Dressler syndrome) — weeks to months later, the immune system attacks the pericardium, causing pericarditis. This is an autoimmune reaction: cardiac antigens (proteins from the dead heart tissue) were released into the bloodstream, and the immune system made antibodies against them, which then attack the pericardium.
2. Heart failure (HF) — a large area of scar tissue can no longer contract. If too much of the heart is scarred, the pump fails.
3. Arrhythmias — scar tissue can be a source of abnormal electrical circuits.
4. True ventricular aneurysm (risk of mural thrombus) — the scarred wall is weak and bulges outward during each contraction (dyskinesia = moving abnormally). Blood can pool in this bulging area and form a thrombus (clot), which can break off and travel to the brain causing a stroke.

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PAGE 310 — DIAGNOSIS OF MYOCARDIAL INFARCTION

Blood Markers

"In the first 6 hours, ECG is the gold standard. Cardiac troponin I rises after 4 hours (peaks at 24 hr) and is ↑ for 7-10 days; more specific than other protein markers."

• Troponin I — a protein found ONLY in heart muscle. When heart cells die, troponin I leaks into the blood. It's incredibly specific (only comes from heart, not from skeletal muscle). It rises around 4 hours after the attack, peaks at 24 hours, and stays elevated for 7-10 days. This long window helps diagnose heart attacks even if a patient comes in days later.

"CK-MB increases after 6-12 hours (peaks at 16-24 hr) and is predominantly found in myocardium but can also be released from skeletal muscle. Useful in diagnosing reinfarction following acute MI because levels return to normal after 48 hours."

• CK-MB — another enzyme (a protein that helps chemical reactions). "CK" = creatine kinase, "MB" = the muscle-brain isoform. It's found mostly in heart muscle but also in skeletal muscle (less specific). It rises later (6-12 hours), peaks at 16-24 hours, and importantly RETURNS TO NORMAL after 48 hours. This makes it useful for detecting a SECOND heart attack — if troponin is already elevated from the first attack, CK-MB can show if a new attack occurred.

ECG Changes

• ST elevation (STEMI) — full-thickness transmural infarct. The ST segment lifts above baseline.
• ST depression (NSTEMI, subendocardial) — partial thickness infarct. ST segment dips below baseline.
• Hyperacute (peaked) T waves — VERY early sign, within the first minutes of a heart attack. The T waves become tall and pointy.
• T-wave inversion — the T wave flips downward, indicating ischemia.
• Pathologic Q waves or poor R wave progression — indicates an old, completed transmural infarct. The scarred tissue is electrically silent, so Q waves become prominent.

ECG Localization Table

• LAD = Left Anterior Descending artery - supplies the front and a large portion of the heart. Nicknamed "the widow maker" because blockage is so deadly.
• LCX = Left Circumflex artery - supplies the lateral (side) wall.
• RCA = Right Coronary Artery - supplies the inferior (bottom) wall and often the SA/AV nodes (the heart's electrical pacemakers). Blockage can cause dangerous heart rate problems.
• ECG leads (V1-V6, I, II, III, aVL, aVF, aVR) — these are different "camera angles" that look at the heart's electricity from different directions. Like taking a photo from the front vs the side vs below.

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PAGE 311 — NARROW COMPLEX TACHYCARDIAS (Fast Heart Rate, Normal Electrical Pathway)

• Tachycardia = fast heart rate (>100 beats per minute). Normal is 60-100.
• QRS complex = the spike on an ECG that represents the ventricles contracting (the main pumping chambers). When the ventricles activate through the normal pathway (His-Purkinje system), the QRS is narrow (<120 msec). When they activate via an abnormal pathway, the QRS is wide (≥120 msec).
• Narrow QRS means the fast heart rhythm is originating ABOVE the ventricles (in the atria or AV node). This is called "supraventricular" (supra = above).
• AV node = Atrioventricular node. This is the electrical "gateway" between the upper chambers (atria) and lower chambers (ventricles). It slows down the electrical signal, giving the atria time to squeeze before the ventricles do.

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Atrial Fibrillation (AFib)

"Irregularly irregular rate and rhythm with no discrete P waves."

• P waves on ECG represent the atria contracting. In AFib, instead of one organized electrical signal, hundreds of chaotic signals fire randomly in the atria every minute. The atria just QUIVER like a bag of worms - no effective contraction.
• Irregularly irregular — the rhythm has no pattern whatsoever. Random, chaotic.
• Arrhythmogenic activity usually originates from automatic foci near pulmonary vein ostia in left atrium — the triggers most often come from tiny muscle sleeves around where the pulmonary veins (bringing oxygenated blood from lungs) enter the left atrium.

• Predisposes to thromboembolic events, particularly stroke — when the atria quiver instead of properly squeezing, blood pools and can form clots. The most dangerous clot location is the LA appendage (a small ear-shaped pouch off the left atrium). Clots can break off and travel to the brain causing stroke.
• Risk factors: hypertension, CAD, advanced age, atrial dilation — all conditions that stretch or damage the atria over time.

• A — Anti-arrhythmics or rate control
• B — Beta-blockers (slow the heart rate)
• C — Calcium channel blockers (also slow the rate)
• D — Digoxin (an old drug that slows AV node conduction)

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Multifocal Atrial Tachycardia (MAT)

"Irregularly irregular rate and rhythm with at least 3 distinct P wave morphologies, due to multiple ectopic foci in atria. Associated with underlying conditions such as COPD, pneumonia, HF."

• Ectopic foci — "ectopic" means out of place. Instead of one proper pacemaker (the SA node), multiple areas in the atria are misfiring.
• 3 distinct P wave shapes — each ectopic focus produces a differently shaped P wave on ECG. You need at least 3 different P wave shapes to diagnose MAT.
• COPD = Chronic Obstructive Pulmonary Disease (lung disease). Low oxygen levels from COPD stress the atria.

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Atrial Flutter

"Rapid succession of identical, consecutive atrial depolarization waves → 'sawtooth' appearance of P waves."

• Sawtooth pattern — instead of random chaos (like AFib), atrial flutter has a very organized, regular, fast circuit going around and around the atrium (usually 300 times/minute). On ECG this looks like teeth of a saw - regular, identical, rapid flutter waves.
• Reentry circuit around tricuspid annulus — the electrical signal loops in a circle around the tricuspid valve ring (the ring where the tricuspid valve sits in the right atrium). Like a car going round and round a roundabout.
• 4:1 sawtooth pattern — typically the AV node blocks 3 out of every 4 flutter waves (so ventricular rate = 75/min if atrial rate is 300). This protective blocking prevents the ventricles from also beating 300 times/minute.
• Treatment: Same rate control as AFib, plus possible catheter ablation (burning the reentry circuit with a catheter to stop the loop permanently).

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Paroxysmal Supraventricular Tachycardia (PSVT)

"Most often due to a reentrant tract between atrium and ventricle, most commonly in AV node. Commonly presents with sudden-onset palpitations, lightheadedness, diaphoresis."

• Reentrant tract — like atrial flutter but the loop involves both the atrium and ventricle. Electrical signal goes down one pathway, comes back up another, creating a continuous loop.
• Paroxysmal — comes and goes suddenly. You can be perfectly fine, then suddenly your heart races at 150-250 bpm for minutes to hours, then stops just as suddenly.
• Diaphoresis = profuse sweating.
• Treatment: Slowing AV nodal conduction via:
  • Vagal maneuvers — bearing down (Valsalva), bearing, or pressing on carotid arteries. These activate the vagus nerve which slows the AV node.
  • Adenosine — a drug that temporarily blocks the AV node.
  • Catheter ablation — definitive cure.

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Wolff-Parkinson-White (WPW) Syndrome

"Most common type of ventricular preexcitation syndrome. Abnormal fast accessory conduction pathway from atria to ventricle (bundle of Kent) bypasses rate-slowing AV node..."

• Bundle of Kent — in WPW, a person is BORN with an extra electrical wire connecting the atria directly to the ventricles, bypassing the AV node. Think of it as an underground shortcut.
• Preexcitation — the ventricles get excited (activated) EARLIER than normal because the signal doesn't have to wait at the AV node speed bump.
• Delta wave — the bundle of Kent conducts faster than normal, creating a slurred, gradual upstroke at the start of the QRS complex. This slurred initial part is the delta wave - a hallmark of WPW.
• Shortened PR interval — PR interval is the time between atria firing and ventricles firing. Since the bundle of Kent bypasses the AV node delay, the PR interval is shorter than normal.
• Widened QRS — because the ventricles activate through an abnormal, slower route (cell-to-cell spread from the early activation point).
• Reentry circuit → supraventricular tachycardia — the normal AV node path and the bundle of Kent together form a loop, enabling reentrant tachycardia.
• Treatment: Procainamide, ibutilide — these drugs slow conduction in the accessory pathway.
• AVOID AV nodal-blocking drugs (adenosine, calcium channel blockers, beta-blockers) — if you block the AV node in WPW, all the electrical signals go through the fast bundle of Kent to the ventricles at very high rates (200-300/min), which can cause ventricular fibrillation and death!

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PAGE 312 — WIDE COMPLEX TACHYCARDIAS & HEREDITARY CHANNELOPATHIES

Wide Complex Tachycardias

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Ventricular Tachycardia (V-Tach)

"Typically regular rhythm, rate ≥100. Most commonly due to structural heart disease (eg, cardiomyopathy, scarring after myocardial infarction). High risk of sudden cardiac death."

• Rate over 100 bpm, regular, wide QRS complexes.
• Scar tissue from old heart attacks creates abnormal electrical circuits.
• The ventricles beating fast and inefficiently = the heart can barely pump. Risk of degrading into ventricular fibrillation (next).

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Torsades de Pointes

"Polymorphic ventricular tachycardia. Shifting sinusoidal waveforms. May progress to ventricular fibrillation. Long QT interval (eg, sinus bradycardia, congenital long QT syndromes) predisposes to torsades de pointes."

• "Torsades de pointes" is French for "twisting of the points." On ECG, the QRS complexes appear to twist around the baseline - the amplitude (height) shifts up and down in a sinusoidal (wave-like) pattern.
• Long QT interval — the QT interval represents how long it takes the ventricles to recharge after each beat. If this is prolonged, the ventricles are "vulnerable" to firing prematurely, triggering torsades.
• Treatment: Magnesium sulfate (IV), defibrillation if unstable.

• Anti-Arrhythmics (class Ia and III), Arsenic
• Biotics (antibiotics: macrolides, fluoroquinolones)
• Cychotics (antipsychotics: haloperidol), Chloroquine
• Depressants (TCAs = tricyclic antidepressants), Diuretics (thiazides)
• Emetics (ondansetron - anti-nausea drug)
• Fungals (Fluconazole)
• Navir (protease inhibitors for HIV)
• Opioids (methadone specifically)

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Ventricular Fibrillation (V-Fib)

"Disorganized rhythm with no identifiable waves. Treatment: fatal without immediate CPR and defibrillation."

• The ventricles are just quivering chaotically with hundreds of tiny uncoordinated electrical circuits. No proper contractions. Zero effective pumping. Zero cardiac output.
• This is cardiac arrest. Brain damage begins in 4-6 minutes without CPR.
• CPR = Cardiopulmonary Resuscitation (chest compressions to manually pump the heart).
• Defibrillation = delivering a massive electrical shock to the heart to "reset" all those chaotic circuits simultaneously, allowing the normal pacemaker to restart.

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Hereditary Channelopathies

"Inherited mutations of cardiac ion channels → abnormal myocardial action potential → ↑ risk of ventricular tachyarrhythmias and sudden cardiac death (SCD)."

• Ion channels — tiny pores in heart cell membranes that let sodium (Na⁺), potassium (K⁺), and calcium (Ca²⁺) flow in and out. This flow is what creates the electrical signal (action potential) that makes the heart beat.
• Channelopathy = disease of ion channels. A genetic mutation makes the channel work abnormally.

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Brugada Syndrome

"Autosomal dominant; most commonly due to loss of function mutation of Na⁺ channels. ↑ prevalence in Asian males. ECG pattern of pseudo-right bundle branch block and ST-segment elevations in leads V₁-V₂. Prevent SCD with ICD."

• Autosomal dominant — you only need ONE copy of the mutated gene (from one parent) to have the condition.
• Loss of function of Na⁺ channels — sodium channels that normally help start the action potential are defective. This creates an abnormal electrical pattern.
• ICD = Implantable Cardioverter-Defibrillator. A small device implanted in the chest that monitors the heart rhythm 24/7 and delivers a shock if it detects ventricular fibrillation. It's essentially a permanent defibrillator inside you.

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Congenital Long QT Syndrome

"Most commonly due to loss of function mutation of K⁺ channels (affects repolarization). Romano-Ward syndrome — autosomal dominant, pure cardiac phenotype (no deafness). Jervell and Lange-Nielsen syndrome — autosomal recessive, sensorineural deafness."

• K⁺ channels = potassium channels. These help the heart cell RECHARGE after each beat. If defective, recharging takes too long → long QT.
• Romano-Ward: Just the heart problem, inherited from ONE parent.
• Jervell and Lange-Nielsen: Inherited from BOTH parents (recessive), causes BOTH long QT AND congenital deafness because the same potassium channels are important in the inner ear.

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Sick Sinus Syndrome

"Age-related degeneration of SA node. ECG can show bradycardia, sinus pauses (delayed P waves), sinus arrests (dropped P waves), junctional escape beats."

• SA node = Sinoatrial node. This is the heart's natural pacemaker, in the upper right atrium. It normally fires 60-100 times per minute and starts every heartbeat.
• Sick sinus syndrome — the SA node wears out with age. It fires too slowly (bradycardia = slow heart rate), pauses too long between beats, or sometimes stops altogether.
• Junctional escape beats — when the SA node fails, the AV junction (the area around the AV node) steps up as a backup pacemaker and fires at its own slower rate (40-60 bpm). These are "escape" beats — the heart's emergency backup system preventing complete cardiac arrest.

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PAGE 313 — CONDUCTION BLOCKS (Heart Blocks)

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First-Degree AV Block

"Prolonged PR interval (>200 msec). Treatment: none required (benign and asymptomatic)."

• PR interval = the time for signal to travel from SA node through atria, through AV node, to ventricles. Normal is 120-200 msec.
• In first-degree block, the AV node is slow but NEVER completely fails. Every signal gets through, just delayed. Like a slow but reliable security guard who always eventually lets you pass.
• Benign - no treatment needed.

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Second-Degree AV Block, Mobitz Type I (Wenckebach)

"Progressive lengthening of PR interval until a beat is 'dropped' (P wave not followed by QRS complex). Variable RR interval with a pattern (regularly irregular). Treatment: none required (usually asymptomatic)."

• Each successive PR interval gets a little longer, longer, longer... until eventually one P wave fires but NO QRS follows (the beat is "dropped"). Then the cycle resets.
• Regularly irregular — it follows a pattern. Like a traffic light that gets progressively slower then resets.
• Usually occurs at the level of the AV node itself.
• Generally benign, often no treatment needed.

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Second-Degree AV Block, Mobitz Type II

"Dropped beats that are not preceded by a change in PR interval. May progress to 3rd-degree block, as it usually indicates a structural abnormality such as ischemia or fibrosis. Treatment: usually a pacemaker."

• Unlike Wenckebach, the PR interval stays CONSTANT. But occasionally a P wave just doesn't get through at all - a beat is suddenly dropped without warning.
• This indicates damage BELOW the AV node (in the bundle branches), which is more serious.
• Can suddenly progress to complete (3rd degree) heart block. Usually needs a pacemaker (an implanted device that sends electrical pulses to make the heart beat at a normal rate).

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Third-Degree (Complete) AV Block

"P waves and QRS complexes rhythmically dissociated. Atria and ventricles beat independently of each other. Atrial rate > ventricular rate. May be caused by Lyme disease. Treatment: pacemaker."

• The AV node is completely blocked. No signal gets through from atria to ventricles.
• The atria beat at their own rate (driven by SA node, ~70-80/min).
• The ventricles beat at their own SLOW rate driven by a "escape pacemaker" lower in the conduction system (~30-40/min).
• On ECG: P waves march at one rate, QRS complexes march at a slower rate - COMPLETELY INDEPENDENT of each other. This is called "AV dissociation."
• Lyme disease — the bacteria Borrelia burgdorferi (spread by tick bites) can infect the conduction system and cause complete heart block.
• Requires a pacemaker.

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Bundle Branch Block

"Interruption of conduction of normal left or right bundle branches. Affected ventricle depolarizes via slower myocyte-to-myocyte conduction from the unaffected ventricle, which depolarizes via the faster His-Purkinje system."

• Bundle branches — the left and right "wires" that carry the signal from the Bundle of His to each ventricle.
• If one branch is blocked, that ventricle can't receive the signal normally. Instead, the signal comes slowly from the OTHER ventricle, cell by cell (like a relay across a field rather than through a fiber-optic cable).
• This slow cell-to-cell spread widens the QRS complex (≥120 msec).
• Left Bundle Branch Block (LBBB) — on ECG, V1 shows a deep S wave, V6 shows a tall broad R wave. Pattern: "WiLLiaM" (in V1: W shape, in V6: M shape for LBBB).
• Commonly caused by cardiomyopathy (heart muscle disease), infiltrative diseases, or aging.

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Premature Atrial Contraction (PAC)

"Extra beats arising from ectopic foci in atria instead of the SA node. Often 2° to ↑ adrenergic drive (eg, caffeine consumption). Benign, but may increase risk for atrial fibrillation and flutter. Narrow QRS complex with preceding P wave on ECG."

• Ectopic focus — a rogue cell somewhere in the atrium fires on its own before the SA node gets a chance.
• Adrenergic drive — adrenaline (epinephrine and norepinephrine) makes heart cells more excitable. Caffeine, stress, and stimulants increase adrenergic drive, making ectopic beats more common.
• On ECG: a normal-looking beat comes early, with a differently-shaped P wave (because it originated from a different location than normal).

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Premature Ventricular Contraction (PVC)

"Ectopic beats arising from ventricle instead of the SA node. Shortened diastolic filling time → ↓ SV compared to a normal beat. Prognosis is largely influenced by underlying heart disease. Wide QRS complex with no preceding P wave on ECG."

• Diastole = the relaxation phase when the ventricle fills with blood. If a beat comes too early (PVC), the ventricle hasn't had time to fill completely.
• SV = Stroke Volume, the amount of blood pumped per beat. Less filling → less pumping → reduced stroke volume.
• On ECG: wide, bizarre QRS complex appearing early, with no P wave before it (because it didn't start in the atria).
• Most people have occasional PVCs (you feel them as a "skipped beat" or "flip-flop" sensation). Benign in healthy hearts, but can be dangerous in damaged hearts.

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PAGE 314 — COMPLICATIONS AFTER MI (Post-Infarction Timeline Table)

• Pericardial friction rub — when the inflamed pericardial layers rub against each other, a scratchy sound (like walking on fresh snow) is heard with a stethoscope.
• Pericardial effusion — fluid accumulating in the pericardial sac.
• Cardiac tamponade — the pericardial sac fills with fluid/blood, squeezing the heart so it cannot fill or pump.
• VSD = Ventricular Septal Defect — a hole in the wall between ventricles.
• Murmur — abnormal heart sound caused by turbulent blood flow (through a hole, leaky valve, etc.).
• Syncope = fainting.
• Mural thrombus — a clot that forms ON the wall of a heart chamber (especially inside an aneurysm where blood stagnates).
• Dyskinesia — "dys" = abnormal, "kinesia" = movement. The scarred aneurysm wall paradoxically BULGES OUT when the rest of the heart squeezes inward.

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PAGE 315 — ACUTE CORONARY SYNDROME TREATMENTS & CARDIOMYOPATHIES

ACS Treatments

• Anticoagulation (heparin) — prevents clot from growing
• Antiplatelet therapy (aspirin + ADP receptor inhibitors like clopidogrel) — prevents platelets from clumping
• Beta-blockers — slow heart rate, reduce oxygen demand
• ACE inhibitors — protect the heart long-term
• Statins — lower cholesterol, stabilize plaques
• Nitroglycerin — dilates blood vessels
• +/- morphine — for pain relief

• Same as above PLUS most importantly reperfusion therapy (opening the blocked artery)
• PCI (Percutaneous Coronary Intervention) = preferred - threading a catheter with a small balloon and stent through blood vessels to physically open the blocked artery. "Percutaneous" = through the skin.
• Fibrinolysis = "clot-busting" drugs (second choice if PCI not available fast enough)
• If the RCA is blocked (right coronary artery occlusion), careful with nitroglycerin - the right ventricle depends heavily on preload (filling pressure), and nitroglycerin reduces preload, causing shock.

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Cardiomyopathies (Diseases of the Heart Muscle)

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Dilated Cardiomyopathy (DCM)

"Most common cardiomyopathy (90% of cases). Often idiopathic or familial."

• Dilated = the heart chambers get stretched and enlarged (dilated), like a balloon that's been overinflated and can't spring back.
• The heart walls become thin and the heart pumps weakly (systolic dysfunction).
• Systolic dysfunction = the heart can't squeeze properly (ejection fraction is reduced).
• Causes: Alcohol (most common acquired cause), drugs (doxorubicin - a chemotherapy drug, cocaine), viral infections (Coxsackie B virus), Chagas disease (parasitic infection common in South America), ischemia (CAD), hemochromatosis (too much iron deposited in heart), thyrotoxicosis (overactive thyroid), wet beriberi (vitamin B1 deficiency), peripartum cardiomyopathy (after pregnancy), familial/genetic (TTN gene mutation - titin protein defect).
• Findings: Heart failure, S3 heart sound (a "gallop" sound = sign of a dilated, failing heart), systolic regurgitant murmur (mitral valve doesn't close properly because the ring has stretched), dilated heart on echocardiogram (heart ultrasound), balloon appearance on CXR (chest X-ray).
• Eccentric hypertrophy — sarcomeres (the contractile units) are added in series (end-to-end), making the heart longer and thinner. Like stretching taffy.
• Treatment: Salt restriction, ACE inhibitors/ARBs, beta-blockers, diuretics (remove excess fluid), spironolactone, ICD, heart transplant in severe cases.
• Stress cardiomyopathy (Takotsubo, "broken heart syndrome") — a unique variant where extreme emotional or physical stress causes the heart's apex (bottom tip) to balloon outward while the base contracts normally. Caused by a sudden surge of adrenaline. The heart looks like a Japanese octopus trap (takotsubo) on imaging.

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Hypertrophic Cardiomyopathy (HCM)

"60-70% of cases are familial, autosomal dominant (most commonly due to mutations in genes encoding sarcomeric proteins, such as myosin binding protein C and β-myosin heavy chain). Causes syncope during exercise and may lead to sudden death (eg, in young athletes) due to ventricular arrhythmia."

• Hypertrophic = the heart muscle gets thicker (hypertrophy), like an overdeveloped muscle.
• Sarcomeric proteins — the molecular machinery of muscle contraction. Mutations cause the muscle to overgrow.
• Concentric hypertrophy — sarcomeres added in parallel (side-by-side), making the wall thicker. Like adding more lanes to a road.
• Diastolic dysfunction — the thick, stiff heart can't RELAX and fill properly, even though it squeezes fine.
• Syncope during exercise — when you exercise, your heart rate rises and filling time decreases. The already thick, stiff heart fills even less, output drops, and you faint.
• Sudden cardiac death in young athletes — the thickened wall creates abnormal electrical patterns leading to ventricular fibrillation during intense exercise. The #1 cause of sudden cardiac death in young athletes in the US.

• The septum is asymmetrically thickened and bulges into the left ventricular outflow tract (the channel blood exits through to the aorta).
• Systolic anterior motion of the mitral valve — during contraction, the mitral valve leaflet gets sucked toward the septum (Venturi effect), further blocking outflow.
• Dynamic obstruction → dyspnea, syncope.
• Treatment: Beta-blockers or calcium channel blockers (verapamil) - these SLOW the heart rate, giving more time to fill. Avoid drugs that decrease preload (diuretics, vasodilators, nitroglycerin) - less filling makes the obstruction WORSE. ICD if high risk.

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Restrictive/Infiltrative Cardiomyopathy

"Postradiation fibrosis, Löffler endocarditis, Endocardial fibroelastosis, Amyloidosis, Sarcoidosis, Hemochromatosis (PLEASe Help!)"

• Restrictive = the heart walls become stiff and non-compliant (they can't stretch to fill with blood). The ventricle is like a rigid box - it restricts filling.
• Diastolic dysfunction ensues (can't fill properly).
• Amyloidosis — abnormal protein (amyloid) deposits between heart cells, making the heart stiff. Causes low-voltage ECG despite thick myocardium (because amyloid doesn't conduct electricity well, paradoxically making the ECG look small despite a thick heart).
• Löffler endocarditis — associated with hypereosinophilic syndrome. Eosinophils (a type of white blood cell) infiltrate the myocardium, causing fibrosis.

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PAGE 316 — HEART FAILURE

Heart Failure (HF) — The Basics

"Clinical syndrome of cardiac pump dysfunction → congestion and low perfusion."

• Dyspnea = difficulty breathing (from fluid in the lungs).
• JVD (Jugular Venous Distension) = the neck veins bulge visibly because pressure is backed up from the failing right heart.
• Pitting edema = swelling in legs/ankles that leaves a "pit" or dent when you press it. Fluid has leaked out of blood vessels into tissue.
• Rales = crackling sounds heard with a stethoscope when fluid in the lungs crackles during breathing.
• S3 heart sound = an extra "gallop" sound early in diastole, caused by rapid filling of a dilated, failing ventricle.

Types of Heart Failure

• The heart can't squeeze hard enough.
• Ejection fraction (EF) = percentage of blood in the ventricle that gets pumped out per beat. Normal ≥55%. HFrEF: <40%.
• Cause: ischemia/MI, dilated cardiomyopathy.
• Graph shows reduced contractility - the pressure-volume loop is shifted.

• The heart can squeeze fine, but can't RELAX to fill properly.
• EF is preserved (≥50%) but the heart is stiff.
• Cause: hypertension, hypertrophic cardiomyopathy, restrictive cardiomyopathy.
• Graph shows reduced compliance (steeper pressure-volume curve).

Right Heart Failure vs Left Heart Failure

• Orthopnea — shortness of breath when lying flat. When you lie down, blood redistributes by gravity back to the heart and lungs. A failing heart can't handle this extra volume → fluid floods the lungs. Patients sleep with multiple pillows or sitting upright.
• Paroxysmal Nocturnal Dyspnea (PND) — waking up from sleep gasping. Same mechanism - lying flat for hours allows fluid to accumulate in lungs, then the patient suddenly wakes choking.
• Pulmonary edema — fluid pours into the air sacs of the lungs. Breathing becomes like drowning from inside. Contains "heart failure cells" (hemosiderin-laden macrophages) — macrophages that have eaten the red blood cells that leaked into the lungs, turning brown from the iron (hemosiderin).

• Congestive hepatomegaly — liver becomes engorged with blood backed up from the right heart. Rarely can progress to "cardiac cirrhosis" (liver scarring). Shows "nutmeg liver" appearance (mottled red-brown pattern).
• JVD — elevated venous pressure shows in neck veins.
• Peripheral edema — fluid leaks into legs, ankles, and feet.

Compensatory Mechanisms in HF (The Flowchart on Page 316)

• ↑ Sympathetic tone → releases catecholamines (epinephrine/norepinephrine):
  • Beta-1 (β₁) catecholamines → ↑ contractility (heart squeezes harder) + ↑ heart rate
  • Alpha (α₁) catecholamines → vasoconstriction (blood vessels narrow)

• Kidneys sense low blood pressure → release Renin → creates Angiotensin II
• Angiotensin II (AT1): Vasoconstriction → ↑ blood pressure
• Angiotensin II + Aldosterone + ADH (V₂): Retain sodium and water → ↑ circulating volume → ↑ venous return (preload)
• ADH (V₁): Additional vasoconstriction

• The heart has to work harder against higher resistance (afterload)
• The heart enlarges and remodels (bad structural changes)
• This leads to Deleterious cardiac remodeling (shown at the top of the flow chart)

• ACE inhibitors / ARBs — block Angiotensin II formation/action (reduce vasoconstriction and fluid retention)
• Beta-blockers — block sympathetic overdrive (except in acute decompensated HF)
• Neprilysin inhibitors (sacubitril) — increase beneficial natriuretic peptides that oppose RAAS
• Loop and thiazide diuretics — remove excess fluid (symptomatic relief)
• Aldosterone antagonists (spironolactone) — block aldosterone-driven salt retention
• SGLT2 inhibitors — newer drugs that improve both symptoms and mortality
• Hydralazine + nitrates — for patients who can't tolerate ACE inhibitors/ARBs

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PAGE 317 — SHOCK & CARDIAC TAMPONADE

Shock

Types of Shock

• CO = Cardiac Output (how much the heart pumps per minute)
• SVR = Systemic Vascular Resistance (how tight the blood vessels are)
• PCWP = Pulmonary Capillary Wedge Pressure (reflects left heart filling pressure)
• CVP = Central Venous Pressure (reflects right heart filling)
• SV = Stroke Volume (blood per beat)

• Hypovolemic shock — not enough volume (blood/fluid loss). SVR goes up (vessels constrict to maintain BP) but there's no fluid to pump. Cold and clammy.
• Cardiogenic shock — the pump has failed. Fluid backs up (high PCWP), but little gets forward. Cold and clammy.
• Obstructive shock — something is physically blocking flow (tamponade, PE, tension pneumothorax). Fluid can't get through or out of the heart.
• Distributive shock (eg, sepsis) — massive vasodilation. Blood vessels dilate so much that blood pressure falls even though the heart is pumping fine (or faster). Patient is WARM and flushed, not cold. SVR is LOW (vasodilated).

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Cardiac Tamponade

"Compression of the heart by fluid (eg, blood, effusions) → ↓ CO. Equilibration of diastolic pressures in all 4 chambers."

• Fluid fills the pericardial sac, squeezing the heart from outside. The heart can't expand to fill during diastole - it's being crushed.
• All four chambers equilibrate at the same diastolic pressure — because the external compression prevents any chamber from having a different pressure.

1. Hypotension — low blood pressure (heart can't pump)
2. Distended neck veins (JVD) — blood can't get INTO the compressed heart, so it backs up in the veins
3. Muffled/distant heart sounds — fluid surrounding the heart dampens the sounds

• ↓ in amplitude of systolic BP by >10 mmHg during inspiration
• Normally, systolic BP drops slightly with inspiration. In tamponade, this drop is exaggerated.
• During inspiration: ↑ venous return to right heart → right ventricle expands → interventricular septum bows LEFT → ↓ LV filling → ↓ stroke volume → ↓ BP.
• Also seen in: constrictive pericarditis, obstructive pulmonary disease (asthma, COPD).

• Electrical alternans — the QRS complexes alternate in height (tall, small, tall, small) because the heart is SWINGING back and forth inside the fluid-filled pericardial sac, like a pendulum. The "electrical axis" changes with each swing.
• Low-voltage QRS complexes.

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Summary: The Big Picture

1. Atherosclerosis clogs coronary arteries → Angina (chest pain warning)
2. Plaque ruptures → complete blockage → Heart Attack (MI)
3. Heart muscle dies → over days/weeks goes through stages of inflammation and healing → Scar
4. Enough scar = Heart Failure (pump doesn't work)
5. Scar = abnormal electrical circuits → Arrhythmias (dangerous rhythms)
6. All these problems can lead to Shock (organs not getting enough blood)