Cardiology
Chest Pain Assessment and Acute Coronary Syndrome
Understanding Chest Pain Etiology
Chest pain can originate from multiple anatomical structures. A systematic approach by anatomical layer helps narrow the differential diagnosis:
| Layer | Common Conditions |
|---|---|
| Skin & Subcutaneous | Laceration, herpes zoster, cellulitis |
| Musculoskeletal | Costochondritis, muscle strain, rib fractures |
| Pleural | Pleurisy, pneumothorax, pneumonia |
| Pericardium | Pericarditis, pericardial effusion, tamponade |
| Cardiac | Acute coronary syndrome, myocarditis, acute heart failure |
| Esophageal | Gastroesophageal reflux disease, esophageal spasm, perforation |
| Aortic | Aortic dissection, thoracic aortic aneurysm |
| Abdominal | Biliary colic, pancreatitis, peptic ulcer disease |
| Psychiatric | Anxiety disorder, panic attacks |
Angina Classification Systems
Diamond Classification (Typicality of Angina)
The Diamond classification helps stratify the probability that chest pain represents true anginal discomfort:
- 3 of 3 typical features: Substernal location + Provoked by exertion + Relieved by nitroglycerin or rest = Typical angina
- 2 of 3 typical features = Atypical angina
- 1 of 3 typical features = Non-anginal chest pain
Clinical Pearl
Use this classification to guide your pretest probability assessment before ordering additional diagnostic testing.
Canadian Cardiovascular Society Grading
This scale quantifies functional limitations from angina:
| Grade | Characteristics |
|---|---|
| I | Chest pain only with strenuous or prolonged exertion |
| II | Mild limitation; pain with light exertion (climbing stairs, walking >2 blocks) |
| III | Marked limitation; pain with ordinary activities (walking 1-2 blocks on flat surface) |
| IV | Unable to perform any activity without symptoms; pain at rest |
Initial Assessment and Workup
Time-Critical Actions
All chest pain patients require an EKG within 10 minutes of arrival.
Immediate Diagnostic Tests
- Electrocardiogram — obtain within 10 minutes
- Complete blood count — assess for anemia or infection
- Comprehensive metabolic panel — electrolytes, renal function, glucose
- Oxygen saturation — by pulse oximetry
- Chest radiograph — assess for alternative diagnoses
- Cardiac telemetry — continuous monitoring for arrhythmias
- Initial troponin — high-sensitivity troponin preferred
Serial Testing Protocol
- Repeat EKG at 2-3 minutes if initial is normal or nondiagnostic and clinical suspicion remains high
- Serial troponin measurements at 4-6 hour intervals for at least 2 measurements
- Troponin may be normal in the first 3 hours of symptom onset
EKG Localization of Myocardial Infarction
Understanding which coronary artery corresponds to EKG changes guides your assessment:
| EKG Leads | Myocardial Region | Likely Culprit Artery |
|---|---|---|
| V1–V2 | Septal wall | Left anterior descending |
| V3–V4 | Anterior wall | Left anterior descending |
| I, aVL | Lateral wall | Left circumflex or LCx diagonal |
| V5–V6 | Lateral wall | Left circumflex |
| II, III, aVF | Inferior wall | Right coronary artery |
| V4R | Right ventricle | Right coronary artery |
| V1–V3 (ST depression) | Posterior wall (reciprocal) | Right coronary or left circumflex |
RV Infarction Clue
If inferior STEMI is present, always check lead V4R for ST elevation suggesting right ventricular involvement.
Risk Stratification Scores
TIMI Risk Score for Unstable Angina/NSTEMI
Calculate points (0-7 total) and correlate with mortality risk:
| Criterion | Points |
|---|---|
| Age ≥65 years | 1 |
| ≥3 cardiac risk factors | 1 |
| Known CAD (stenosis ≥50%) | 1 |
| Aspirin use in past 7 days | 1 |
| ST-segment deviation ≥0.5 mm | 1 |
| Elevated cardiac biomarkers | 1 |
| Severe angina (≥2 episodes in 24h) | 1 |
Risk stratification: 0-1 points = low risk, 2-4 points = intermediate risk, 5-7 points = high risk
GRACE Risk Score
The GRACE score incorporates multiple variables to predict in-hospital and 6-month mortality. Consult scoring tools/nomograms for accurate calculation. Generally:
- Score <140 = Low risk
- Score 140–200 = Intermediate risk
- Score >200 = High risk
Understanding Troponin Elevation
Elevated cardiac troponin indicates myocardial injury but does not specify etiology:
| Type | Mechanism | Examples |
|---|---|---|
| Type 1 | Atherosclerotic plaque rupture with thrombosis | STEMI, NSTEMI |
| Type 2 | Myocardial supply-demand mismatch | Sepsis, anemia, hypertensive crisis, tachyarrhythmia, hypoxia |
| Non-MI elevation | Other myocardial processes | Heart failure, myocarditis, renal failure, pulmonary embolism, sepsis |
Critical Insight
Elevated troponin requires correlation with clinical context, EKG findings, and imaging to determine true MI versus other causes of myocardial injury.
Stress Testing Modalities
| Test Type | Indications | Limitations |
|---|---|---|
| Exercise stress test | Intermediate pretest probability, interpretable EKG, able to exercise | Cannot perform if unable to exercise; unreliable with baseline EKG abnormalities |
| Pharmacologic stress (adenosine/regadenoson) | Unable to exercise, need imaging component | Contraindicated in severe asthma/COPD (adenosine) |
| Dobutamine stress echo | Unable to exercise, need structural assessment | Induces demand ischemia; contraindicated in uncontrolled HTN or tachyarrhythmia |
| Coronary CTA | Low-intermediate pretest probability, assess for alternative diagnosis | Radiation exposure, contrast allergy risk, poor image quality with high heart rate |
Acute Coronary Syndrome Treatment
STEMI Protocol
Time is Myocardium
Door-to-balloon time goal: <90 minutes for primary percutaneous coronary intervention.
Immediate management:
- Aspirin — 325 mg (loading), then 81 mg daily indefinitely
- Anticoagulation — unfractionated heparin IV bolus/drip or enoxaparin 0.5 mg/kg IV bolus
- Beta-blocker — if HR >50 and SBP >90 mmHg
- Nitroglycerin — 0.4 mg sublingual, repeat every 5 minutes as needed for symptom relief
- Primary PCI — mechanical revascularization within 90 minutes, or
- Fibrinolysis — if PCI unavailable; initiate within 30 minutes (thrombolytic agents: alteplase, reteplase, tenecteplase)
NSTEMI/Unstable Angina Treatment
Medical management:
- Aspirin — 325 mg loading dose, then 81 mg daily
- P2Y12 inhibitor — clopidogrel 600 mg loading (then 75 mg daily), prasugrel, or ticagrelor
- Anticoagulation — unfractionated heparin drip or LMWH (enoxaparin 1 mg/kg SQ BID)
- Oxygen — only if SaO2 <90%
- Nitroglycerin — 0.4 mg sublingual every 5 minutes, transition to IV infusion if ongoing symptoms
- Beta-blocker — (hold if HR <55 or SBP <100)
- High-intensity statin — atorvastatin 80 mg daily or rosuvastatin 40 mg daily
- ACE inhibitor/ARB — initiate at 1-2 days post-infarction if tolerated
Invasive Strategy
Most NSTEMI patients benefit from early invasive evaluation (cardiac catheterization within 12-72 hours depending on risk stratification).
Heart Failure: Classification and Management
Heart Failure Types and Definitions
Heart failure is classified along multiple dimensions:
Ejection Fraction-Based Classification
| Classification | EF Range | Pathophysiology |
|---|---|---|
| HFrEF (reduced) | <40% | Systolic dysfunction; dilated ventricle with poor contractility |
| HFmrEF (mildly reduced) | 40–49% | Intermediate systolic function |
| HFpEF (preserved) | ≥50% | Diastolic dysfunction; normal EF but impaired filling |
Structural Classification
- Systolic HF: Decreased contractility; EF typically <40%
- Diastolic HF: Preserved contractility; impaired relaxation or increased stiffness
Output Classification
- Forward failure: Inadequate perfusion to organs (low cardiac output)
- Backward failure: Venous congestion upstream of failing ventricle
- High-output failure: Excessive metabolic demand (sepsis, thyrotoxicosis, anemia, pregnancy)
NYHA Functional Classification and Treatment Strategy
| Class | Description | Symptoms | Baseline Treatment |
|---|---|---|---|
| I | Asymptomatic | No limitation with ordinary activity | ACE-I/ARB + Beta-blocker |
| II | Mild symptoms | Limitation with strenuous activity | + Loop diuretic PRN |
| III | Moderate symptoms | Limitation with ordinary activity | + Aldosterone antagonist or ISDN/hydralazine combo |
| IV | Severe symptoms | Symptoms at rest or with minimal activity | Palliative care consideration; cardiac transplant evaluation |
Warm-Cold and Wet-Dry Classification
This classification helps categorize hemodynamic status and guides therapy:
Common Precipitants of Acute Decompensation
Remember "ADHF" — Acute Decompensated Heart Failure precipitants:
- Adherenc issues (medication or dietary nonadherence)
- Dietary indiscretion (excessive sodium or fluid intake)
- Ischemia (acute MI triggering acute failure)
- Arrhythmias (new-onset atrial fibrillation or other dysrhythmia)
- Hypertensive crisis (acute elevation in afterload)
- Renal failure (reduced diuretic efficacy, volume retention)
- Fluid overload from other sources (transfusions, IV medications)
- Infection (pneumonia, UTI, other systemic infection)
- Endocrine (thyroiditis, hyperthyroidism)
Additionally: Use of NSAIDs, cocaine, discontinuation of guideline-directed medical therapy
Diagnostic Workup
Essential labs and imaging for all decompensated HF:
| Test | Utility |
|---|---|
| CBC | Assess for anemia (may worsen HF), infection |
| CMP | Electrolytes, renal function, glucose |
| BNP or NT-proBNP | <300 pg/mL excludes HF; >900 makes HF likely; 300–900 indeterminate |
| TSH | Rule out thyroid dysfunction as reversible cause |
| EKG | Assess for ischemia, arrhythmia, chamber enlargement |
| Chest X-ray | Evaluate pulmonary edema, cardiomegaly, alternative diagnoses |
| Transthoracic echocardiogram | Assess EF, diastolic function, valve pathology, RV function |
Management by Hemodynamic Category
Universal Measures (All Patients)
- Sodium restriction: <2 grams daily
- Fluid restriction: <2 liters daily (more restrictive in severe hyponatremia)
- Daily weights: Target body weight; alert if gain >2–3 lbs in 1–2 days
- Intake/output monitoring: Document all sources
- Continue guideline-directed medical therapy if blood pressure permits
Congestion ("Wet" Status) — LMNOP Protocol
When pulmonary or peripheral edema is present, use the LMNOP mnemonic:
| Intervention | Details |
|---|---|
| Lasix (Furosemide) | Start 40–160 mg IV Q12H; typically 2.5x home oral dose. Titrate to euvolemia. |
| Morphine | 2–4 mg IV; improves dyspnea via vasodilation + anxiolysis. Use caution in hypotension/hypoxia. |
| Nitrates | Nitroglycerin IV (goal SBP >100) or isosorbide; improves preload + afterload. |
| Oxygen | Target SpO2 ≥90%; use cautiously to avoid hypercapnia in COPD overlap. |
| Position | Elevate head of bed 30–45°; improves ventilation. |
Loop diuretic equivalents (approximate for calculating doses):
| Agent | Equivalent Dose |
|---|---|
| Furosemide (Lasix) | 20 mg IV = 40 mg PO |
| Torsemide | 20 mg (more potent than furosemide) |
| Bumetanide | 1 mg (most potent, short duration) |
Diuretic Dosing Pitfall
Do not use the same IV dose as home PO dose. IV furosemide is approximately 2.5 times more potent than oral.
Afterload Reduction
When systolic dysfunction is present without hypotension:
- ACE inhibitor (e.g., lisinopril) or ARB (e.g., losartan)
- Hydralazine + isosorbide dinitrate combination — particularly beneficial in African Americans
- IV nitroglycerin — for acute afterload reduction
Cardiogenic Shock Management
- ICU-level care required
- Inotropic support:
- Dobutamine 2–20 mcg/kg/min (increases contractility + decreases afterload)
- Milrinone 0.25–0.75 mcg/kg/min (phosphodiesterase-3 inhibitor; inotrope + vasodilator)
- Vasopressors: Norepinephrine or dopamine if hypotensive despite inotropes
- Mechanical support: Intra-aortic balloon pump, percutaneous ventricular assist device, extracorporeal membrane oxygenation (ECMO)
- Renal replacement therapy: Consider if oliguria develops
- Urgent cardiology/transplant consultation
Documentation in the Medical Record
Every HF encounter should clearly document:
- Current NYHA functional class
- Type of HF (systolic vs. diastolic, ischemic vs. nonischemic)
- Most recent ejection fraction and date of last echocardiogram
- Dry weight (helps guide diuretic dosing on future visits)
- Current medication regimen with doses
- Renal function and electrolytes from most recent labs
- Volume status assessment (wet vs. dry)
Atrial Fibrillation: Diagnosis, Risk Stratification, and Management
Classification of Atrial Fibrillation
| Category | Duration | Clinical Notes |
|---|---|---|
| Paroxysmal | <48 hours; self-terminates | May progress to persistent AF over time |
| Persistent | >7 days; requires intervention for termination | Sustained but not permanent |
| Long-standing persistent | >1 year on anticoagulation | Chronicity increases structural remodeling |
| Permanent | Accepted by patient and provider as indefinite | Reversion not pursued |
Additionally, classify as valvular (structural valve disease or prosthetic) or nonvalvular (all other cases), as this affects anticoagulation choice.
Etiology of Atrial Fibrillation
Identifying the Trigger
Finding and treating the underlying cause is as important as rate/rhythm control.
Cardiac causes: - Heart failure (systolic or diastolic) - Cardiomyopathy (ischemic or nonischemic) - Myocardial infarction or active ischemia - Valvular disease (mitral stenosis particularly) - Atrial myxoma or other structural abnormality
Pulmonary causes: - COPD or other chronic lung disease - Pneumonia or acute respiratory infection - Pulmonary embolism - Obstructive sleep apnea
Metabolic/Endocrine causes: - Thyrotoxicosis or hyperthyroidism - Elevated catecholamines (pheochromocytoma)
Exogenous triggers: - Alcohol (chronic heavy use or acute binge) - Cocaine or other stimulants - Caffeine excess - Theophylline
Neurogenic causes: - Subarachnoid hemorrhage - Acute stroke - Traumatic brain injury
Acute Rate Control
When the patient is hemodynamically stable and rapid ventricular response requires rate control, use IV agents:
| Agent | IV Dosing | Mechanism | Notes |
|---|---|---|---|
| Verapamil | 5–10 mg IV bolus; may repeat in 15 min | Calcium channel blocker | Fast onset; contraindicated if hypotensive or heart failure |
| Diltiazem | 0.25 mg/kg IV bolus; repeat if needed | Calcium channel blocker | Alternative to verapamil with less negative inotropy |
| Metoprolol | 5–15 mg IV Q6H | Beta-blocker | Slower onset than IV calcium blockers |
| Esmolol | 0.5 mg/kg bolus, then infusion | Ultra-short-acting beta-blocker | Use when rapid reversibility desired |
| Digoxin | 0.5 mg IV, then 0.25 mg Q6H | Vagomimetic + AV nodal blocker | Narrow therapeutic window; less preferred acutely |
| Amiodarone | 150 mg IV over 10 min, then infusion | Antiarrhythmic (class III) | Last-line if others contraindicated or ineffective |
Maintenance Rate Control
Outpatient oral agents for rhythm control:
- Beta-blockers (metoprolol ER, atenolol, carvedilol)
- Calcium channel blockers (diltiazem ER, verapamil ER)
- Digoxin (if significant HFrEF or sedentary lifestyle)
Target heart rate depends on symptoms and function:
| Scenario | Target HR |
|---|---|
| Symptomatic AF with EF >40% | <80 bpm at rest; <110 with moderate activity |
| Asymptomatic AF with EF >40% | <110 bpm (lenient rate control) acceptable |
| AF with HFrEF (EF <40%) | <80 bpm preferred |
Stroke Risk Stratification: CHA₂DS₂-VASc Score
This score predicts stroke risk and guides anticoagulation intensity:
| Risk Factor | Points |
|---|---|
| Congestive heart failure or LV dysfunction | 1 |
| Hypertension (on treatment) | 1 |
| Age ≥75 years | 2 |
| Diabetes mellitus | 1 |
| Stroke/TIA/thromboembolism history | 2 |
| Vascular disease (MI, peripheral artery disease, aortic plaque) | 1 |
| Age 65–74 years | 1 |
| Sex category (female) | 1 |
Anticoagulation recommendations:
| Score | Recommendation |
|---|---|
| 0 (male) or 1 (female) | No anticoagulation; consider aspirin 75–325 mg daily |
| 1 (male) or 2 (female) | Anticoagulation or aspirin (shared decision-making) |
| ≥2 (male) or ≥3 (female) | Oral anticoagulation indicated |
Bleeding Risk: HAS-BLED Score
Identifies patients at higher bleeding risk while on anticoagulation:
| Risk Factor | Points |
|---|---|
| Hypertension (uncontrolled) | 1 |
| Abnormal renal/liver function | 1 |
| Stroke history | 1 |
| Bleeding history | 1 |
| Labile INR (if on warfarin) | 1 |
| Elderly (age >65) | 1 |
| Drug use (NSAIDs, antiplatelet) or alcohol excess | 1 |
Interpretation:
- Score <3: Low bleeding risk
- Score ≥3: Assess risk vs. benefit; do not withhold anticoagulation, but monitor closely
Anticoagulation Options
Anticoagulation is Essential
Most AF patients with CHA₂DS₂-VASc ≥2 require anticoagulation to reduce stroke risk by ~60%.
| Agent | Dosing | Monitoring | Key Advantages | Limitations |
|---|---|---|---|---|
| Dabigatran | 150 mg BID (110 mg BID if high bleeding risk) | No routine labs; check renal function baseline | Rapid onset/offset; predictable PK | Dyspepsia; GI bleed risk; must take intact |
| Rivaroxaban | 20 mg daily with food (15 mg if CrCl 15–30) | No routine labs; check renal function baseline | Once daily; can open capsule if needed | Food interaction; GI bleed risk |
| Apixaban | 5 mg BID (2.5 mg BID if ≥2 of: age ≥60, weight ≤60 kg, Cr ≥1.5) | No routine labs; check renal function baseline | Lowest GI bleed risk; twice-daily convenient for some | Twice-daily dosing |
| Edoxaban | 60 mg daily (30 mg if weight <60 kg, CrCl 15–50, or concurrent strong P-gp inhibitor) | No routine labs | Once daily | More strokes if CrCl >95; less data in valvular AF |
| Warfarin | Dose adjusted for INR 2–3 | INR monitoring (initially frequent, then q4 weeks) | Decades of safety data; reversible with vitamin K | Dietary interactions; narrow therapeutic window; frequent monitoring |
| Aspirin | 75–325 mg daily | No monitoring | Readily available | Inferior efficacy vs. anticoagulants; used only if AC contraindicated |