USMLE Step 1 Cardiovascular Practice Questions

A pressure-volume loop of the left ventricle shows an increase in end-systolic volume without a change in end-diastolic volume. This change is most consistent with:

• (A) Increased afterload
• (B) Increased preload
• (C) Increased contractility
• (D) Decreased heart rate

Which heart sound is associated with the closure of the mitral and tricuspid valves at the beginning of ventricular systole?

• (A) S1
• (B) S2
• (C) S3
• (D) S4

An electrocardiogram (ECG) shows a regular rhythm with a heart rate of 40 bpm. P waves are present and occur regularly at a rate of 80 bpm, but there is no consistent relationship between P waves and QRS complexes. QRS complexes are wide. This pattern is most characteristic of:

• (A) Third-degree AV block (Complete heart block)
• (B) First-degree AV block
• (C) Second-degree AV block, Mobitz I (Wenckebach)
• (D) Second-degree AV block, Mobitz II

Which coronary artery most commonly supplies the sinoatrial (SA) node?

• (A) Right coronary artery (RCA)
• (B) Left anterior descending artery (LAD)
• (C) Left circumflex artery (LCX)
• (D) Posterior descending artery (PDA)

According to the Frank-Starling mechanism, an increase in venous return directly leads to:

• (A) Increased stroke volume
• (B) Decreased stroke volume
• (C) Increased heart rate
• (D) Decreased contractility

Which parameter is calculated as the difference between end-diastolic volume (EDV) and end-systolic volume (ESV)?

• (A) Stroke Volume (SV)
• (B) Cardiac Output (CO)
• (C) Ejection Fraction (EF)
• (D) Mean Arterial Pressure (MAP)

Administration of a beta-1 adrenergic receptor agonist would be expected to cause which of the following effects on the heart?

• (A) Increased heart rate and increased contractility
• (B) Decreased heart rate and decreased contractility
• (C) Increased heart rate and decreased contractility
• (D) Decreased heart rate and increased contractility

On an ECG, the P wave represents:

• (A) Atrial depolarization
• (B) Ventricular depolarization
• (C) Ventricular repolarization
• (D) AV nodal delay

Which vessel type accounts for the largest proportion of total peripheral resistance (TPR) in the circulatory system?

• (A) Arterioles
• (B) Capillaries
• (C) Venules
• (D) Large arteries

What is the primary intrinsic mechanism responsible for autoregulation of blood flow in vital organs like the brain and kidneys, ensuring relatively constant flow despite changes in perfusion pressure?

• (A) Myogenic response
• (B) Metabolic regulation
• (C) Endothelial factors (e.g., NO)
• (D) Neural control (sympathetic)

The second heart sound (S2, 'dub') is associated with the closure of which valves?

• (A) Aortic and pulmonary valves
• (B) Mitral and tricuspid valves
• (C) Mitral and aortic valves
• (D) Tricuspid and pulmonary valves

A decrease in arterial blood pressure sensed by baroreceptors leads to which compensatory response?

• (A) Increased sympathetic outflow and decreased parasympathetic outflow
• (B) Decreased sympathetic outflow and increased parasympathetic outflow
• (C) Increased sympathetic and parasympathetic outflow
• (D) Decreased sympathetic and parasympathetic outflow

Which type of blood vessel has the largest total cross-sectional area in the systemic circulation?

• (A) Capillaries
• (B) Arterioles
• (C) Venules
• (D) Aorta

What does the QRS complex on an ECG represent?

• (A) Ventricular depolarization
• (B) Atrial depolarization
• (C) Ventricular repolarization
• (D) Atrial repolarization

Pulse pressure is defined as the difference between:

• (A) Systolic pressure and diastolic pressure
• (B) Mean arterial pressure and central venous pressure
• (C) Systolic pressure and mean arterial pressure
• (D) Diastolic pressure and central venous pressure

Which ion current is primarily responsible for the pacemaker potential (phase 4 depolarization) in the SA node?

• (A) Funny current (If - mixed Na+/K+ influx)
• (B) Fast sodium current (INa)
• (C) L-type calcium current (ICa-L)
• (D) Delayed rectifier potassium current (IK)

Increased contractility (inotropy) of the left ventricle would shift the pressure-volume loop in which direction?

• (A) Upward and to the left
• (B) Downward and to the right
• (C) Only upward
• (D) Only to the left

The T wave on an ECG represents:

• (A) Ventricular repolarization
• (B) Atrial repolarization
• (C) Ventricular depolarization
• (D) Papillary muscle contraction

Which physiological factor is the primary determinant of coronary blood flow?

• (A) Myocardial oxygen demand
• (B) Aortic diastolic pressure
• (C) Sympathetic nervous system activity
• (D) Parasympathetic nervous system activity

During which phase of the cardiac cycle does most coronary blood flow to the left ventricle occur?

• (A) Diastole
• (B) Systole
• (C) Isovolumetric contraction
• (D) Isovolumetric relaxation

What is the approximate formula for calculating Mean Arterial Pressure (MAP)?

• (A) MAP = Diastolic Pressure + 1/3 (Pulse Pressure)
• (B) MAP = Systolic Pressure + 1/3 (Pulse Pressure)
• (C) MAP = (Systolic Pressure + Diastolic Pressure) / 2
• (D) MAP = Cardiac Output x Total Peripheral Resistance

A physiological splitting of the S2 heart sound is typically heard during:

• (A) Inspiration
• (B) Expiration
• (C) Valsalva maneuver
• (D) Standing up quickly

Nitric oxide (NO) released from endothelial cells causes vasodilation primarily by:

• (A) Increasing cGMP levels in vascular smooth muscle
• (B) Increasing cAMP levels in vascular smooth muscle
• (C) Blocking calcium channels in vascular smooth muscle
• (D) Activating potassium channels in vascular smooth muscle

Which condition would cause a shift of the cardiac function curve (relating cardiac output to right atrial pressure) upward and to the left?

• (A) Increased contractility
• (B) Increased total peripheral resistance
• (C) Decreased blood volume
• (D) Cardiac tamponade

The PR interval on an ECG represents the time taken for:

• (A) Conduction from the SA node through the AV node to the ventricles
• (B) Ventricular depolarization
• (C) Atrial depolarization
• (D) Ventricular repolarization

In a healthy individual standing up from a lying position, what is the initial hemodynamic change and the subsequent baroreflex response?

• (A) Initial drop in BP, followed by increased HR and vasoconstriction
• (B) Initial rise in BP, followed by decreased HR and vasodilation
• (C) Initial drop in BP, followed by decreased HR and vasodilation
• (D) Initial rise in BP, followed by increased HR and vasoconstriction

What is represented by the dicrotic notch (incisura) on an aortic pressure tracing?

• (A) Closure of the aortic valve
• (B) Opening of the aortic valve
• (C) Closure of the mitral valve
• (D) Peak systolic pressure

Which factor directly increases myocardial oxygen consumption the most?

• (A) Increased ventricular wall tension (afterload and preload)
• (B) Increased heart rate
• (C) Increased contractility
• (D) Increased coronary blood flow

Ejection Fraction (EF) is calculated as:

• (A) (Stroke Volume / End-Diastolic Volume) x 100%
• (B) (Stroke Volume / End-Systolic Volume) x 100%
• (C) (Cardiac Output / Heart Rate) / End-Diastolic Volume
• (D) (End-Diastolic Volume - End-Systolic Volume) / Cardiac Output

Activation of parasympathetic nerves (vagus nerve) to the heart primarily affects which structure, leading to decreased heart rate?

• (A) Sinoatrial (SA) node
• (B) Ventricular myocardium
• (C) Purkinje fibers
• (D) Arterioles

Total Peripheral Resistance (TPR) is primarily determined by the resistance in which vessels?

• (A) Arterioles
• (B) Capillaries
• (C) Venules
• (D) Large arteries

A patient has a blood pressure of 140/80 mmHg. What is their approximate Mean Arterial Pressure (MAP)?

• (A) 100 mmHg
• (B) 110 mmHg
• (C) 120 mmHg
• (D) 93 mmHg

Which cardiac biomarker begins to rise earliest after the onset of an acute myocardial infarction?

• (A) Troponin I or T
• (B) CK-MB
• (C) Myoglobin
• (D) LDH-1

What is the effect of angiotensin II on systemic arterioles?

• (A) Potent vasoconstriction
• (B) Potent vasodilation
• (C) No significant effect
• (D) Variable effect depending on tissue bed

An S3 heart sound is often associated with:

• (A) Rapid ventricular filling in early diastole (volume overload)
• (B) Atrial contraction against a stiff ventricle (pressure overload)
• (C) Closure of the semilunar valves
• (D) Closure of the AV valves

Cardiac output is the product of:

• (A) Heart Rate and Stroke Volume
• (B) Mean Arterial Pressure and Total Peripheral Resistance
• (C) End-Diastolic Volume and Ejection Fraction
• (D) Systolic Pressure and Diastolic Pressure

A widened pulse pressure (e.g., 160/60 mmHg) is most characteristic of which condition?

• (A) Aortic regurgitation
• (B) Aortic stenosis
• (C) Mitral stenosis
• (D) Cardiac tamponade

Which ion channelopathy is associated with Long QT Syndrome, increasing the risk of Torsades de Pointes?

• (A) Mutations in potassium channels (e.g., KCNQ1, KCNH2)
• (B) Mutations in sodium channels (e.g., SCN5A)
• (C) Mutations in calcium channels (e.g., CACNA1C)
• (D) Mutations in chloride channels (e.g., CFTR)

An S4 heart sound is associated with:

• (A) Atrial contraction against a stiff, noncompliant ventricle
• (B) Rapid ventricular filling in early diastole
• (C) Closure of the AV valves
• (D) Vibration of papillary muscles

What is the primary mechanism by which digoxin increases cardiac contractility?

• (A) Inhibition of Na+/K+-ATPase, leading to increased intracellular calcium
• (B) Activation of beta-1 adrenergic receptors
• (C) Opening of L-type calcium channels
• (D) Inhibition of phosphodiesterase