A 76-year-old male with a history of chronic uncontrolled hypertension presents to the emergency room following an episode of syncope. He reports that he felt lightheaded and experienced chest pain while walking his dog earlier in the morning. He notes that he has experienced multiple similar episodes over the past year. A trans-esophageal echocardiogram demonstrates a thickened, calcified aortic valve with left ventricular hypertrophy. Which of the following heart sounds would likely be heard on auscultation of this patient?

Crescendo-decrescendo murmur radiating to the carotids that is loudest at the right upper sternal border

Diastolic rumble following an opening snap with an accentuated S1

Early diastolic high-pitched blowing decrescendo murmur that is loudest at the left sternal border

Holosystolic murmur radiating to the axilla that is loudest at the apex

Midsystolic click that is loudest at the apex

A 65-year-old male with a history of coronary artery disease and myocardial infarction status post coronary artery bypass graft (CABG) surgery presents to his cardiologist for a routine appointment. On physical exam, the cardiologist appreciates a holosystolic, high-pitched blowing murmur heard loudest at the apex and radiating towards the axilla. Which of the following is the best predictor of the severity of this patient's murmur?

Enhancement with hand grip maneuver

A 61-year-old man comes to the physician because of a 3-month history of fatigue and progressively worsening shortness of breath that is worse when lying down. Recently, he started using two pillows to avoid waking up short of breath at night. Examination shows a heart murmur. A graph with the results of cardiac catheterization is shown. Given this patient's valvular condition, which of the following murmurs is most likely to be heard on cardiac auscultation?

High-pitched, holosystolic murmur that radiates to the axilla

High-frequency, diastolic murmur heard best at the 2nd left intercostal space

Harsh, late systolic murmur that radiates to the carotids

Blowing, early diastolic murmur heard best at the Erb point

Rumbling, delayed diastolic murmur heard best at the cardiac apex

A 64-year-old man presents to the emergency department because he has been experiencing increased shortness of breath for the last 2 weeks. Specifically, he says that he can barely walk up the stairs to his apartment before he feels winded. In addition, he has been waking up at night gasping for breath and has only been able to sleep propped up on 2 more pillows than usual. Physical exam reveals jugular venous distention as well as pitting lower extremity edema. Which of the following abnormal sounds will most likely be heard in this patient?

Extra heart sound in early diastole

Extra heart sound in late diastole

Parasternal holosystolic murmur

A 52-year-old man comes to the physician for a routine health maintenance examination. He has not seen a physician for 10 years. He works as a telemarketer and does not exercise. Cardiac examination shows a dull, low-pitched sound during late diastole that is best heard at the apex. The sound is loudest in the left lateral decubitus position and during end-expiration. Which of the following is the most likely cause of this finding?

Concentric left ventricular hypertrophy

Fusion of mitral valve leaflets

Seventy-two hours after admission for an acute myocardial infarction, a 48-year-old man develops dyspnea and a productive cough with frothy sputum. Physical examination shows coarse crackles in both lungs and a blowing, holosystolic murmur heard best at the apex. ECG shows Q waves in the anteroseptal leads. Pulmonary capillary wedge pressure is 23 mm Hg. Which of the following is the most likely cause of this patient’s current condition?

Rupture of the chordae tendineae

Rupture of the ventricular free wall

Postmyocardial infarction syndrome

Rupture of the interventricular septum

A 65-year-old man is brought to the emergency department with central chest pain for the last hour. He rates his pain as 8/10, dull in character, and says it is associated with profuse sweating and shortness of breath. He used to have heartburn and upper abdominal pain associated with food intake but had never experienced chest pain this severe. He has a history of diabetes, hypertension, and hypercholesterolemia. His current medication list includes amlodipine, aspirin, atorvastatin, insulin, valsartan, and esomeprazole. He has smoked 1 pack of cigarettes per day for the past 35 years. Physical examination reveals: blood pressure 94/68 mm Hg, pulse 112/min, oxygen saturation 95% on room air, and BMI 31.8 kg/m2. His lungs are clear to auscultation. An electrocardiogram (ECG) shows ST-segment elevations in the inferior leads. The patient is discharged home after 3 days on aspirin, clopidogrel, and atenolol in addition to his previous medications. He is advised to get an exercise tolerance test (ETT) in one month. A month later at his ETT, his resting blood pressure is 145/86 mm Hg. The pre-exercise ECG shows normal sinus rhythm with Q waves in the inferior leads. After 3 minutes of exercise, the patient develops chest pain that is gradually worsening, and repeat blood pressure is 121/62 mm Hg. No ischemic changes are noted on the ECG. What is the most appropriate next step?

Stop exercise and order a coronary angiography

Stop exercise and order a pharmacological stress test

Stop exercise and order an echo stress test

Continue exercise since ECG does not show ischemic changes

Repeat exercise tolerance testing after one month

A 19-year-old woman comes to the physician for a routine health maintenance examination. She appears well. Her vital signs are within normal limits. Cardiac auscultation shows a mid-systolic click and a grade 3/6, late-systolic, crescendo murmur that is best heard at the cardiac apex in the left lateral recumbent position. After the patient stands up suddenly, the click is heard during early systole and the intensity of the murmur increases. Which of the following is the most likely underlying cause of this patient's examination findings?

Congenital interventricular communication

Dystrophic valvular calcification

Valve function during cardiac cycle for USMLE Step 3: High-Yield Physiology Lessons

Cardiac Valves - The Heart's Doors

Function: Ensure unidirectional blood flow by opening and closing in response to pressure gradients.
Types: Atrioventricular (Mitral, Tricuspid) & Semilunar (Aortic, Pulmonary).

Anatomy of the four cardiac valves

⭐ Exam Favorite: Valve opening is a silent, passive process. The characteristic heart sounds (S1, S2) are produced by the forceful closure of the valves, which causes blood turbulence.

📌 Mnemonic for valve location/blood flow: Try Pulling My Aorta (Tricuspid → Pulmonary → Mitral → Aortic).

Valves in Systole - The Big Squeeze

Initiation (Isovolumetric Contraction):
- Ventricular pressure rapidly ↑, exceeding atrial pressure.
- Mitral and Tricuspid (AV) valves SNAP SHUT.
- This closure creates the S1 heart sound (“lub”).
- Aortic and Pulmonic (semilunar) valves remain closed.
Ejection Phase:
- Ventricular pressure continues to ↑, exceeding aortic/pulmonary artery pressure.
- Aortic and Pulmonic valves are forced OPEN.
- Blood is forcefully ejected from the ventricles into the aorta and pulmonary artery.

⭐ The mitral component (M1) of the S1 sound slightly precedes the tricuspid component (T1) because left ventricular contraction starts earlier.

Cardiac Cycle: Valve Function and Heart Phases

Valves in Diastole - The Chill Phase

Semilunar (Aortic & Pulmonary) Valves → CLOSED
- As ventricles relax, ventricular pressure falls below the pressure in the aorta and pulmonary artery.
- This pressure gradient reversal snaps the semilunar valves shut.
- Closure creates the S2 heart sound ("dub"), marking the beginning of diastole.
Atrioventricular (Mitral & Tricuspid) Valves → OPEN
- When ventricular pressure drops below atrial pressure, the AV valves drift open.
- Allows for passive, low-pressure ventricular filling from the atria.
- This initial filling phase is responsible for most (~80%) of the ventricular volume.

Cardiac Cycle: Pressure, Volume, and Valve Events

⭐ In diastolic heart failure, the ventricle is stiff and non-compliant. This impairs its ability to relax and fill properly, leading to ↑ end-diastolic pressure even with a normal blood volume.

Heart Sounds - Lub-Dub Dub

S1 (Lub): Closure of mitral & tricuspid (AV) valves. Marks the start of systole. Loudest at the apex.
S2 (Dub): Closure of aortic & pulmonic (SL) valves. Marks the end of systole. Loudest at the base.

Chest auscultation areas for heart sounds

⭐ Physiological Splitting of S2: During inspiration, decreased intrathoracic pressure increases venous return to the right ventricle. This delays pulmonic valve (P2) closure, causing a split sound after the aortic valve (A2) closes.

Pathological Sounds:
- S3 (Ventricular Gallop): Early diastole. Associated with volume overload (e.g., CHF). 📌 Mnemonic: "SLOSH-ing-in".
- S4 (Atrial Gallop): Late diastole. Stiff, noncompliant ventricle (e.g., LVH). 📌 Mnemonic: "a-STIFF-wall".

High‑Yield Points - ⚡ Biggest Takeaways

Valve closure is a passive process driven by pressure gradients, producing the main heart sounds.

S1 ("lub") marks the start of systole with the closure of the mitral and tricuspid valves.

S2 ("dub") signals the beginning of diastole with the closure of the aortic and pulmonic valves.

Valve opening is normally silent.

Stenosis obstructs forward flow, creating a pressure gradient.

Regurgitation causes backward (retrograde) flow through an incompletely closed valve.

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