Cardiovascular System on Step 1: Physiology First, Disease Second

Scope and time budget

Twenty-five questions is just over one 30-minute block. In a 12-week plan, cardiovascular and gastrointestinal can share a week, with cardiovascular getting the larger part. The system pays back preparation in other rows: hemodynamics supports renal physiology, shock and sepsis sit in the multisystem row, and venous thromboembolism connects to blood and respiratory content. See the respiratory and renal page for the overlap.

What is tested

• Structure. Cardiac anatomy, embryology and the coronary circulation.
• Function. The cardiac cycle, pressure-volume loops, ECG basics, cardiac output, preload, afterload and the Frank-Starling mechanism.
• Blood pressure control. Baroreceptors, the renin-angiotensin-aldosterone system, hypertension and antihypertensive drugs.
• Coronary and heart failure disease. Ischemic heart disease and acute coronary syndromes, heart failure pathophysiology and drug therapy.
• Rhythm and valves. Arrhythmias and antiarrhythmic drugs, valvular disease and murmurs.
• Congenital and inflammatory disease. Congenital heart disease, cardiomyopathies, myocarditis, pericardial disease, infective endocarditis and rheumatic fever.
• Vascular disease. Atherosclerosis and lipid-lowering drugs, aortic aneurysm and dissection, peripheral arterial disease, shock with hemodynamic monitoring, venous thromboembolism and cardiac tumors.

Anchor facts and US conventions

• Core equations. Cardiac output = stroke volume x heart rate. Mean arterial pressure = diastolic pressure plus one third of pulse pressure. Ejection fraction = stroke volume / end-diastolic volume.
• STEMI localization. ST elevation in II, III and aVF points to the inferior wall (right coronary artery). I, aVL and V5-V6 point to the lateral wall (left circumflex). V1-V4 point to the anterior wall (left anterior descending).
• Heart failure with reduced ejection fraction. ACE inhibitors, ARBs or sacubitril-valsartan, beta-blockers (carvedilol, metoprolol succinate, bisoprolol), mineralocorticoid antagonists and SGLT2 inhibitors reduce mortality. This is the standard teaching based on American Heart Association and related guidance.
• Diuretics at the bedside. Loop diuretics block the Na-K-2Cl cotransporter. Thiazides block the Na-Cl cotransporter and can raise calcium. Spironolactone blocks aldosterone receptors and can cause hyperkalemia.
• Anticoagulation. Warfarin and INR, heparin and aPTT, with protamine and vitamin K as the respective reversal agents.
• Infective endocarditis. Staphylococcus aureus is the leading cause in people who inject drugs. The valve involved and the underlying risk factor often decide the answer.
• Conventions. Blood pressure in mm Hg, lipids in mg/dL, and US generic names such as epinephrine and norepinephrine.

Three typical traps

1. Memorizing murmurs by name only. Stems describe the sound, its timing (systolic or diastolic), location and maneuver response. Know how Valsalva, squatting, handgrip and inspiration change each murmur, and why, from the changes in preload and afterload.
2. Misreading a pressure-volume loop. Loops are tested as pictures. Practice labeling the four phases and then predicting how the loop shifts with increased preload, increased afterload or increased contractility. Do not rely on a memorized "answer" for a given picture.
3. Confusing a drug's goal with its adverse effect. Beta-blockers, calcium channel blockers, ACE inhibitors, nitrates and antiarrhythmics each have a mechanism, a benefit and a signature toxicity (for example cough with ACE inhibitors, or bradycardia and heart block with non-dihydropyridine calcium channel blockers). Questions ask for the toxicity far more often than the mechanism.

How to revise this system

• Start with physiology. Draw the cardiac cycle, the Wiggers diagram and a pressure-volume loop until you can reproduce them. Then derive the effects of changing a variable.
• Build a murmur table. Timing, location, radiation, cause, maneuver response.
• Table the cardiac drugs. Class, mechanism, key use, key adverse effect. Include antihypertensives, antiarrhythmics by class, lipid-lowering drugs, nitrates and inotropes.
• Link to ECG. Learn only the patterns Step 1 expects: ST elevation by territory, atrial fibrillation, heart block, and a few conduction abnormalities.
• Practice with mixed blocks. Cardiovascular items often include renal or endocrine findings. Mixed blocks teach you to spot those links.

See the study plan guide for where this system sits in the schedule.

What the questions look like

Expect a vignette with vital signs, an examination finding (often a murmur or an edema description) and sometimes an ECG or a graph. The final question asks for the mechanism, the diagnosis, the effect of a drug on a hemodynamic variable or the adverse effect of a treatment. Our practice bank uses original vignettes in the same format, with conventional units and five options, and it does not reuse official or recalled material. The Step 1 hub shows all the systems and weights, and the high-yield topics guide collects the cross-system equations.

Hemodynamics: a short drill

Practice predicting direction of change without numbers. If preload rises, what happens to stroke volume by the Frank-Starling mechanism? If afterload rises, what happens to stroke volume and end-systolic volume? If contractility falls, what happens to the pressure-volume loop width? Writing arrows (up, down, no change) beside five variables for each condition is faster than recalling a formula, and it is what many Step 1 stems actually require.

Do the same for shock: classify it as hypovolemic, cardiogenic, distributive or obstructive, and write the expected change in cardiac output, systemic vascular resistance and central venous pressure for each. Four rows with three arrows each is a compact table that serves the cardiovascular row and the multisystem row at the same time.

Finish with the coronary arteries. Know which vessel supplies the sinoatrial node, the atrioventricular node and the posterior descending artery in a right-dominant heart, because ischemia questions often ask which vessel is blocked from the territory affected.