Cardiovascular Disorders
Learning Objectives
By the end of this topic, you should be able to:
- Classify heart failure by ejection fraction and explain the compensatory mechanisms that eventually decompensate
- Differentiate stable angina, unstable angina, NSTEMI, and STEMI on clinical, ECG, and biomarker grounds
- Stage hypertension using current thresholds and select an appropriate first-line agent based on compelling indications
- Recognize the major arrhythmias by their ECG signature and outline the immediate management priority for each
- Identify red-flag presentations (chest pain, syncope, sudden dyspnea) that demand urgent cardiac workup
- Avoid the common exam traps that link symptoms, drugs, and diagnoses incorrectly
Quick Answer
Cardiovascular disorders are diseases of the heart and blood vessels — chiefly hypertension, ischemic heart disease, heart failure, and arrhythmias — and together they are the leading cause of death worldwide. They matter because they share overlapping risk factors (smoking, diabetes, dyslipidemia, hypertension itself) and because early recognition changes outcomes dramatically: a STEMI treated within 90 minutes has a fraction of the mortality of one treated late. For exams, the core skill is pattern recognition — matching a symptom cluster, ECG finding, or biomarker pattern to the correct diagnosis and immediate next step.
Heart Failure
Definition. Heart failure (HF) is a clinical syndrome in which the heart cannot pump enough blood to meet the body's metabolic demands, or can only do so at abnormally high filling pressures.
Classification by ejection fraction (EF) — this is the axis examiners love:
- HFrEF (reduced EF, ≤40%) — the pump itself is weak (systolic dysfunction), classically from prior MI or dilated cardiomyopathy
- HFmrEF (mildly reduced EF, 41–49%) — an intermediate category
- HFpEF (preserved EF, ≥50%) — the muscle contracts fine but the stiff, hypertrophied ventricle cannot relax and fill properly (diastolic dysfunction), classically from long-standing hypertension in an older patient
Why it matters. The EF split isn't academic — it decides therapy. HFrEF has a robust evidence base for the "four pillars" (ACE-I/ARB/ARNI, beta-blocker, mineralocorticoid receptor antagonist, SGLT2 inhibitor), all shown to cut mortality. HFpEF, by contrast, has far fewer mortality-reducing drugs; management leans on treating congestion and comorbidities.
Left- vs right-sided failure. Left heart failure backs up into the lungs — dyspnea, orthopnea, paroxysmal nocturnal dyspnea, crackles. Right heart failure backs up into the systemic venous system — raised JVP, hepatomegaly, peripheral (pitting) edema, ascites. In practice, left-sided failure is the most common cause of right-sided failure, since a congested pulmonary circuit raises pressure the right ventricle must work against.
Common misunderstanding. Students often assume "heart failure" means the heart has stopped or is about to stop — it hasn't. It means the heart's output is inadequate for demand, a chronic and often manageable state, not a terminal event by itself. Another frequent error: assuming a normal EF rules out heart failure — HFpEF patients have completely normal ejection fractions.
Real-world example. A 70-year-old woman with decades of poorly controlled hypertension presents with exertional breathlessness. Her echo shows EF 60% but a thickened, stiff left ventricle with impaired relaxation on Doppler — this is HFpEF, and her treatment centers on diuresis and blood pressure control rather than the HFrEF drug pillars.
Ischemic Heart Disease
Definition. Ischemic (coronary) heart disease results from an imbalance between myocardial oxygen supply and demand, almost always due to atherosclerotic narrowing of the coronary arteries.
The spectrum, from stable to catastrophic:
- Stable angina — predictable exertional chest pain relieved by rest or nitrates; caused by a fixed plaque limiting flow under demand
- Acute coronary syndrome (ACS) — an unstable plaque ruptures and triggers thrombosis; this splits into:
- Unstable angina — ischemic symptoms at rest, normal troponin, no permanent damage yet
- NSTEMI — same as above but troponin is raised, indicating actual myocyte death
- STEMI — complete coronary occlusion with ST elevation on ECG and raised troponin; the true emergency
Why it matters. STEMI is a "door-to-balloon" emergency — every 30-minute delay in reperfusion measurably worsens survival. NSTEMI/unstable angina are managed urgently but not with immediate thrombolysis, since there's no artery that thrombolysis can reopen if it's not fully occluded, and thrombolysis in this setting carries bleeding risk without proportional benefit.
Common misunderstanding. A very common exam trap: students give thrombolytics for NSTEMI. Thrombolysis is reserved for STEMI (or a STEMI-equivalent) where a specific occluded vessel can be identified on ECG. NSTEMI is managed with antiplatelets, anticoagulation, and risk-stratified angiography instead.
Real-world example. A 58-year-old smoker develops crushing central chest pain radiating to the left arm with diaphoresis. ECG shows ST elevation in leads II, III, and aVF (inferior STEMI). The correct next step isn't "start a statin and reassess" — it's immediate activation of the cath lab for primary PCI, because myocardium is dying in real time.
Arrhythmias
Definition. Arrhythmias are abnormalities of cardiac rhythm arising from disordered impulse generation (automaticity) or conduction (re-entry, block).
Key patterns to recognize:
- Atrial fibrillation — irregularly irregular rhythm, absent P waves, chaotic baseline; the leading risk is embolic stroke, so anticoagulation (guided by CHA₂DS₂-VASc score) is often as important as rate control
- Ventricular tachycardia — wide-complex tachycardia, life-threatening if sustained, especially post-MI
- Ventricular fibrillation — chaotic, no organized output, immediate cardiac arrest — defibrillate without delay
- Heart block — first-degree (prolonged PR, benign), second-degree (intermittently dropped beats — Mobitz I is usually benign, Mobitz II often needs a pacemaker), third-degree/complete (atria and ventricles beat independently — needs pacing)
Why it matters. The immediate management priority differs sharply: AF is rarely a same-minute emergency unless the patient is hemodynamically unstable; VF always is. Exam questions frequently test whether you can tell "needs a pacemaker" (Mobitz II, complete heart block) from "just observe" (first-degree block, Mobitz I in an asymptomatic patient).
Common misunderstanding. Students often treat "irregular pulse" as synonymous with AF. Frequent ectopic beats or Mobitz I block can also feel irregular; the ECG, not the pulse alone, makes the diagnosis.
Hypertension
Definition. Hypertension is persistently elevated arterial blood pressure, the single largest modifiable risk factor for cardiovascular death worldwide.
Staging (adult, in mmHg):
- Normal: under 120/80
- Elevated: 120–129 systolic and under 80 diastolic
- Stage 1: 130–139/80–89
- Stage 2: ≥140/90
Why it matters. Hypertension is silent — most patients feel nothing — yet it drives left ventricular hypertrophy, HFpEF, stroke, chronic kidney disease, and accelerated atherosclerosis. It is the textbook example of a disease where treating a number (not a symptom) saves lives.
Compelling indications drive drug choice. This is a favorite exam theme: don't just memorize "first-line agents" — match the drug to the comorbidity.
- Diabetes with proteinuria → ACE inhibitor or ARB (renoprotective)
- Heart failure with reduced EF → ACE-I/ARNI + beta-blocker (dual benefit)
- Isolated systolic hypertension in the elderly → thiazide or calcium channel blocker
- Pregnancy → labetalol, nifedipine, or methyldopa (ACE-I/ARB contraindicated — teratogenic)
Common misunderstanding. Students sometimes think ACE inhibitors are safe in all hypertensive patients. They are contraindicated in pregnancy and require caution in bilateral renal artery stenosis, where they can precipitate acute kidney injury by dropping efferent arteriolar tone.
Key Terms
| Term | Definition |
|---|---|
| Ejection fraction (EF) | Percentage of blood in the left ventricle pumped out with each contraction; the main measure distinguishing HFrEF from HFpEF |
| Troponin | Cardiac protein released into blood on myocyte injury; the key biomarker separating unstable angina (normal) from NSTEMI (raised) |
| ACS (acute coronary syndrome) | Umbrella term for unstable angina, NSTEMI, and STEMI, all caused by acute plaque rupture and thrombosis |
| Orthopnea | Breathlessness when lying flat, relieved by sitting up; a classic symptom of left-sided heart failure |
| JVP (jugular venous pressure) | Bedside marker of right atrial pressure; raised in right-sided heart failure and fluid overload |
| CHA₂DS₂-VASc | Scoring system estimating stroke risk in atrial fibrillation, used to decide whether to anticoagulate |
| Afterload | The resistance the heart must pump against; chronically raised in hypertension, driving left ventricular hypertrophy |
| Mobitz II | A second-degree heart block pattern with sudden, unpredictable dropped beats; considered high-risk and usually needs a pacemaker |
Common Mistakes
Misconception: "A normal ejection fraction means the patient does not have heart failure." Why it's wrong: EF measures systolic squeeze, not diastolic filling. A ventricle can contract normally yet be too stiff to fill, causing symptomatic congestion. Correct: HFpEF is a genuine, common form of heart failure with normal or near-normal EF; diagnosis relies on symptoms plus diastolic dysfunction on echo (and often raised natriuretic peptides), not on EF alone.
Misconception: "Chest pain plus a normal ECG rules out a heart attack." Why it's wrong: Early ischemia, non-diagnostic territory, or NSTEMI can all present with an unremarkable initial ECG; ischemic changes and troponin rises can lag behind symptom onset. Correct: Serial ECGs and troponin measurements over several hours are needed before ACS can be safely excluded — a single normal ECG is not sufficient.
Misconception: "All patients with atrial fibrillation need urgent electrical cardioversion." Why it's wrong: Most AF is managed with rate or rhythm control on a non-emergency timeline plus anticoagulation; emergency cardioversion is reserved for hemodynamic instability (hypotension, ongoing ischemia, pulmonary edema). Correct: Assess hemodynamic stability first — stable AF is worked up (echo, thyroid function, CHA₂DS₂-VASc) before any decision on rhythm strategy.
Comparison and Connections
| Feature | Stable Angina | Unstable Angina | NSTEMI | STEMI |
|---|---|---|---|---|
| Trigger | Exertion, fixed plaque | Plaque rupture, rest pain | Plaque rupture, partial occlusion | Plaque rupture, complete occlusion |
| ECG | Normal or transient ST depression on exertion | May show ST depression/T inversion | ST depression/T inversion | ST elevation |
| Troponin | Normal | Normal | Elevated | Elevated |
| Immediate action | Optimize medical therapy | Urgent risk stratification | Urgent risk stratification, antiplatelets | Emergency reperfusion (PCI/thrombolysis) |
| Feature | HFrEF | HFpEF |
|---|---|---|
| Ejection fraction | ≤40% | ≥50% |
| Primary defect | Weak contraction (systolic) | Stiff, non-relaxing ventricle (diastolic) |
| Typical cause | Prior MI, dilated cardiomyopathy | Chronic hypertension, aging, obesity |
| Mortality-reducing drugs | ACE-I/ARNI, beta-blocker, MRA, SGLT2 inhibitor | Fewer proven options; SGLT2 inhibitors help |
Practice Questions
Recall
- What blood pressure range defines Stage 2 hypertension?
- What is the key biomarker that distinguishes NSTEMI from unstable angina?
Understanding
- Explain why thrombolysis is given in STEMI but not in NSTEMI.
- Explain why left-sided heart failure commonly leads to right-sided heart failure over time.
Application
- A 65-year-old with diabetes and microalbuminuria is newly diagnosed with hypertension. Which class of antihypertensive would you start, and why?
- A patient with known AF develops sudden hypotension and pulmonary edema during a follow-up visit. What is the immediate management priority?
Analysis
- Compare HFrEF and HFpEF in terms of underlying pathophysiology and why their drug treatments differ so much.
- A patient has chest pain, a normal ECG, and a normal initial troponin. Analyze why you cannot yet discharge this patient safely, and what should happen next.
Answer guidance
- ≥140/90 mmHg.
- Troponin — elevated in NSTEMI, normal in unstable angina, since troponin rise reflects actual myocyte necrosis.
- Thrombolysis dissolves a clot occluding a specific artery, which is only demonstrable in STEMI (ST elevation localizes the occluded vessel); in NSTEMI the occlusion is often partial or in a vessel not identifiable from the ECG, and giving thrombolytics offers no proven benefit while adding bleeding risk.
- Left-sided failure raises pressure in the pulmonary circulation; the right ventricle must pump against this elevated afterload continuously, and over time it hypertrophies and eventually fails too (a "domino" effect through the pulmonary vasculature).
- An ACE inhibitor or ARB — beyond blood pressure control, these agents reduce intraglomerular pressure and slow progression of diabetic nephropathy, addressing both the hypertension and the renal protection need simultaneously.
- Treat as unstable AF: this patient needs urgent (often emergency) electrical cardioversion because hemodynamic instability, not routine rate/rhythm control, dominates the picture.
- HFrEF is a problem of contractile weakness, so drugs that reduce afterload and neurohormonal activation (ACE-I, beta-blockers, MRA, SGLT2 inhibitors) directly improve pump function and have shown mortality benefit in large trials. HFpEF is a problem of ventricular stiffness — there is no "weak pump" to unload in the same way, so the same neurohormonal blockers have shown far less mortality benefit, and management instead targets symptom control (diuretics) and the comorbidities (hypertension, AF, obesity) driving the stiffness.
- Ischemic ECG changes and troponin elevation can lag hours behind symptom onset; a single normal ECG/troponin pair only excludes ACS at that moment, not over the diagnostic window. The correct next step is serial troponin measurement (e.g., at 0 and 3 hours per most protocols) and repeat ECG, with ongoing clinical monitoring, before ACS can be safely ruled out.
FAQ
Is heart failure the same as a heart attack? No. A heart attack (myocardial infarction) is a sudden event where heart muscle dies from lost blood supply. Heart failure is a chronic syndrome where the heart pumps inadequately — an MI is one of many possible causes of heart failure, but they are not the same thing.
Why does hypertension often have no symptoms? Blood vessels and organs can tolerate gradually rising pressure for years without triggering pain receptors, which is why hypertension is called a "silent" disease — damage to the heart, kidneys, and brain accumulates before symptoms like headache or vision changes appear, usually only at very high pressures.
Why is atrial fibrillation dangerous if the heart rate is controlled? Even with a controlled rate, the fibrillating atria don't contract effectively, so blood pools and can clot, particularly in the left atrial appendage. That clot can embolize to the brain and cause a stroke, which is why anticoagulation decisions are separate from rate control decisions.
Can you have a heart attack with normal cholesterol? Yes. Cholesterol is one of several risk factors; smoking, diabetes, hypertension, family history, and inflammation all contribute to plaque formation and rupture. Roughly half of MI patients have cholesterol levels considered "normal" on standard panels.
Why do doctors care so much about door-to-balloon time in STEMI? "Time is muscle" — during a complete coronary occlusion, myocardium dies progressively, and the benefit of reperfusion (PCI) shrinks with every passing minute. Guidelines target under 90 minutes from first medical contact to balloon inflation because outcomes worsen measurably beyond that window.
Quick Revision
- Heart failure is classified by ejection fraction: HFrEF (≤40%), HFmrEF (41–49%), HFpEF (≥50%)
- Left heart failure → pulmonary symptoms (dyspnea, orthopnea); right heart failure → systemic congestion (edema, raised JVP, hepatomegaly)
- HFrEF has four mortality-reducing drug classes: ACE-I/ARNI, beta-blocker, MRA, SGLT2 inhibitor
- ACS spectrum: unstable angina (normal troponin) → NSTEMI (raised troponin, no ST elevation) → STEMI (raised troponin + ST elevation)
- Only STEMI gets thrombolysis/primary PCI as emergency reperfusion; NSTEMI/UA get risk-stratified urgent management
- Door-to-balloon target for STEMI: under 90 minutes
- Hypertension staging: Stage 1 = 130–139/80–89 mmHg; Stage 2 = ≥140/90 mmHg
- Match antihypertensive to compelling indication: ACE-I/ARB for diabetic nephropathy, ACE-I + beta-blocker for HFrEF, avoid ACE-I/ARB in pregnancy
- Atrial fibrillation: irregularly irregular rhythm with absent P waves; anticoagulate based on CHA₂DS₂-VASc, not just rate control
- Ventricular fibrillation is an immediate defibrillation emergency; Mobitz II and complete heart block usually need pacing
- A single normal ECG/troponin cannot exclude ACS — serial testing is required
- Hypertension is often asymptomatic ("silent killer") but drives LVH, HFpEF, stroke, and CKD over time
Related Topics
Prerequisites: Cardiovascular system anatomy and physiology (cardiac cycle, conduction system), basic ECG interpretation
Related Topics: Diabetes mellitus (shared risk factor and vascular complications), Chronic kidney disease (both cause and consequence of hypertension), Stroke and cerebrovascular disease
Next Topics: Respiratory disorders (overlap with cardiac dyspnea and cor pulmonale), Pharmacology of cardiovascular drugs, Emergency medicine approach to chest pain and acute decompensated heart failure