Cardiology Study Guide

📖 Core Concepts Cardiology – Medical specialty focused on the heart & vascular system; deals with diagnosis & treatment of CAD, heart failure, valvular disease, arrhythmias. Heart chambers & valves – RA, RV, LA, LV; four valves (tricuspid, pulmonary, mitral, aortic) ensure unidirectional flow. Electrical conduction – SA node → atrial depolarization → AV node (delay) → His‑Purkinje system → ventricular depolarization. Mechanical cycle – Systole: ventricular contraction → blood ejection; Diastole: ventricular relaxation → filling. Preload & Afterload – Preload = end‑diastolic wall stretch; Afterload = resistance left ventricle must overcome to eject blood. Coronary artery disease (CAD) – Atherosclerotic plaque narrows coronary arteries → ischemia, angina, MI. Heart failure (HF) – Inability of heart to supply adequate output; classified by ejection fraction (reduced vs preserved). Arrhythmias – Disturbances of rhythm: tachycardia, bradycardia, irregular. Key types: AFib, atrial flutter, VT, VF, AV block. Cardiac arrest – Sudden loss of effective pump function; most often VF/VT secondary to CAD. Hypertension – Chronic BP ≥ 140 mm Hg systolic or ≥ 90 mm Hg diastolic; major risk factor for CAD, HF, stroke. --- 📌 Must Remember Normal BP range: 100–140 mm Hg systolic / 60–90 mm Hg diastolic. SA node = natural pacemaker (≈ 60–100 bpm). First‑line CAD therapy – aspirin + beta‑blocker ± statin ± nitrate. HF guideline drugs – ACE‑I/ARB, β‑blocker, MRA, diuretic; add sacubitril/valsartan or SGLT2‑I when indicated. Primary PCI = standard of care for ST‑elevation MI (STEMI). AFib stroke prevention – DOACs (Rely, ROCKET‑AF, ARISTOTLE) ≥ warfarin safety. Implantable cardioverter‑defibrillator (ICD) reduces mortality in symptomatic HF (SCD‑HeFT). Cardiac arrest algorithm – Immediate CPR → early defibrillation (VF/pulseless VT) → advanced life support. Preload dependence – ↑ venous return ↑ stroke volume (Frank‑Starling). --- 🔄 Key Processes Electrical Conduction Sequence SA node fires → atrial depolarization (P wave). Impulse reaches AV node → brief delay. Bundle of His → right/left bundle branches → Purkinje fibers → ventricular depolarization (QRS). Repolarization → T wave. Cardiac Cycle (one heartbeat) Isovolumetric contraction: AV valves close → pressure rises, no volume change. Ejection phase: Aortic/pulmonary valves open → blood ejected (stroke volume). Isovolumetric relaxation: Semilunar valves close → pressure falls, volume unchanged. Filling phase: AV valves open → ventricular filling (preload). Acute MI Management 1️⃣ 12‑lead ECG → identify STEMI. 2️⃣ Activate cath lab → primary PCI ≤ 90 min. 3️⃣ Give aspirin + P2Y12 inhibitor + anticoagulant. 4️⃣ Initiate β‑blocker, ACE‑I, statin (if not contraindicated). Cardiac Arrest Algorithm Check responsiveness & pulse → if absent, start CPR (100 compressions/min). Attach AED/defibrillator → shock if VF/pulseless VT. Continue cycles → epinephrine 1 mg every 3‑5 min, consider amiodarone for refractory VF. --- 🔍 Key Comparisons Stable vs Unstable Angina Stable: predictable, triggered by exertion, relieved by rest. Unstable: occurs at rest or with minimal exertion, longer duration, higher MI risk. Atrial Fibrillation vs Atrial Flutter AFib: irregularly irregular ventricular response; no distinct saw‑tooth waves. Flutter: regular “saw‑tooth” atrial activity ( 300 bpm); ventricular response often 2:1. Ventricular Tachycardia vs Ventricular Fibrillation VT: organized, rapid ventricular rhythm (≥ 100 bpm); may be hemodynamically stable. VF: chaotic, no effective cardiac output; immediate defibrillation required. Thiazide Diuretic vs ACE Inhibitor (HTN first line) Thiazide: reduces volume → lowers BP; especially effective in salt‑sensitive patients. ACE‑I: blocks RAAS → reduces afterload & remodeling; preferred in diabetes, CKD. --- ⚠️ Common Misunderstandings “All chest pain = MI.” Many non‑cardiac causes (GERD, musculoskeletal) mimic angina; use characteristics (radiation, exertional trigger, relief with rest) and ECG/biomarkers. “Beta‑blockers are contraindicated in acute HF.” They are harmful in decompensated HF but improve mortality once the patient is stabilized. “A normal stress test rules out CAD.” Sensitivity ≈ 70%; a negative test does not exclude disease in high‑risk patients. “All atrial fibrillation patients need warfarin.” DOACs are now first‑line unless contraindicated. --- 🧠 Mental Models / Intuition “Pump‑and‑Pipe” – Think of the heart as a pump (ventricular contractility) and the coronary arteries as pipes; blockage (pipe) reduces flow → ischemia → pump dysfunction. Frank‑Starling Curve – Visualize preload on the x‑axis, stroke volume on the y‑axis; a steep slope = good contractility, flattening = failing heart. “V‑shaped Arrhythmia Decision Tree” – Upper branch: rate > 100 bpm → assess stability → treat (β‑blocker, cardioversion, ablation). Lower branch: rate < 60 bpm → evaluate AV block → consider pacing. --- 🚩 Exceptions & Edge Cases Hypertension treatment threshold – Benefit of medication in mild HTN (140–159/90–99 mm Hg) is less certain; lifestyle may suffice. Aspirin in primary prevention – Not universally recommended; weigh bleeding risk. ICD in non‑ischemic HF – SCD‑HeFT showed benefit, but patients with NYHA class I may not need ICD. Statins in elderly > 75 y – Evidence of benefit persists but monitor for polypharmacy and myopathy. --- 📍 When to Use Which Revascularization choice – Primary PCI: STEMI or high‑risk NSTEMI with ongoing ischemia. CABG: Multi‑vessel disease, left main disease, diabetes with complex anatomy. Anti‑arrhythmic drug selection – Rate control (β‑blocker, diltiazem, digoxin) for AFib with rapid ventricular response. Rhythm control (amiodarone, flecainide) in symptomatic paroxysmal SVT or when rate control fails. Imaging modality – Echocardiography: First‑line for structural assessment, valve disease, EF. Cardiac MRI: Tissue characterization (fibrosis, infiltrative disease). CT coronary angiography: Low‑risk CAD assessment. Hypertension drug class – Thiazide + ACE‑I/ARB: First‑line combo for most patients. Calcium‑channel blocker: Add if BP remains uncontrolled or in isolated systolic hypertension. --- 👀 Patterns to Recognize Chest pain + exertion + relief with rest → classic stable angina pattern. Palpitations with irregularly irregular pulse → think AFib. Sudden loss of pulse + no breathing → cardiac arrest → immediate CPR & shockable rhythm check. Elevated JVP + peripheral edema + reduced EF on echo → systolic HF. BP ≥ 140/90 mm Hg + ≥ 2 risk factors → initiate lifestyle + pharmacotherapy. --- 🗂️ Exam Traps “All patients with AFib need a warfarin target INR 2–3.” Newer DOACs are preferred unless contraindicated. “Beta‑blockers are first‑line for all hypertension.” They are not first‑line unless specific comorbidities (post‑MI, angina). “A normal resting ECG rules out CAD.” CAD can be silent; stress testing or imaging may be required. “Ventricular tachycardia always requires immediate defibrillation.” Stable VT may be treated with antiarrhythmics; only pulseless VT/VF needs shock. “Statins are only for secondary prevention.” Primary prevention in high‑risk patients is also evidence‑based (4S trial). ---