A 70-year-old man presented to a medical clinic for a routine follow-up. He has had hypertension for 20 years and is currently on multiple anti-hypertensive medications. The blood pressure is 150/100 mm Hg. The remainder of the examinations were within normal limits. Echocardiography showed some changes in the left ventricle. What is the most likely reason for the change?

Disordered growth of the cardiac cells

Increase in number of normal cardiac cells

Replacement of cardiac cells into stronger red fiber skeletal cells

An 80-year-old African American male presents complaining of worsening shortness of breath that occurs during his weekly round of golf. He also notes he has been waking up at night "choking and gasping for air", though he has been able to gain some relief by propping his head on a stack of pillows before he goes to bed. Upon auscultation, a low frequency, early diastolic gallop is heard over the apex while the patient rests in the left lateral decubitus position. This finding is most consistent with which of the following?

Left ventricular eccentric hypertrophy

Left ventricular concentric hypertrophy

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

On cardiology service rounds, your team sees a patient admitted with an acute congestive heart failure exacerbation. In congestive heart failure, decreased cardiac function leads to decreased renal perfusion, which eventually leads to excess volume retention. To test your knowledge of physiology, your attending asks you which segment of the nephron is responsible for the majority of water absorption. Which of the following is a correct pairing of the segment of the nephron that reabsorbs the majority of all filtered water with the means by which that segment absorbs water?

Proximal convoluted tubule via passive diffusion following ion reabsorption

Distal convoluted tubule via passive diffusion following ion reabsorption

Distal convoluted tubule via aquaporin channels

Thick ascending loop of Henle via passive diffusion following ion reabsorption

Collecting duct via aquaporin channels

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

Isovolumetric contraction and relaxation for USMLE Step 3: High-Yield Physiology Lessons

Isovolumetric Contraction (IVC) - The Big Squeeze

Definition: Initial phase of systole. Ventricles contract against closed valves, so ventricular volume is constant (iso- = same, -volumetric = volume).
Events:
- Starts immediately after mitral/tricuspid (AV) valves close (producing S1 heart sound).
- Ventricles contract, causing left ventricular pressure to rise sharply from <10 mmHg to ~80 mmHg.
- Ends when ventricular pressure exceeds aortic/pulmonic pressure, forcing semilunar valves to open.
EKG Correlation: Corresponds to the QRS complex.

Wiggers Diagram: Isovolumetric Contraction & Relaxation

⭐ The duration of IVC is a key indicator of myocardial contractility. It is prolonged by conditions that increase afterload (like hypertension) as the ventricle needs more time to build pressure.

Isovolumetric Relaxation (IVR) - The Chill Out Phase

Definition: Period between aortic valve closure and mitral valve opening.
Events:
- Ventricles relax after ejecting blood; pressure plummets (diastole).
- All valves (aortic, pulmonary, mitral, tricuspid) are closed.
- Ventricular volume remains constant at its lowest level (End-Systolic Volume or ESV).
Heart Sounds: Aortic valve closure creates the second heart sound (S2).
Pressure Changes: Aortic pressure shows a brief rise (dicrotic notch) from valve closure recoil.

⭐ The v-wave of the jugular venous pressure (JVP) trace peaks during IVR, reflecting the atria filling against a closed tricuspid valve.

Left Ventricular Pressure-Volume Loop

Pressure-Volume Loop - Mapping the Squeeze

Represents one complete cardiac cycle for the left ventricle. The area within the loop signifies the ventricular stroke work.

Cardiac pressure-volume loop with phases and valve events

Phase A → B (Isovolumetric Contraction): Mitral valve closes (S1). Ventricle contracts, pressure ↑, volume is constant.
Phase B → C (Ejection): Aortic valve opens. Ventricle ejects blood. Volume ↓.
Phase C → D (Isovolumetric Relaxation): Aortic valve closes (S2). Ventricle relaxes, pressure ↓, volume is constant.
Phase D → A (Filling): Mitral valve opens. Ventricle fills with blood. Volume ↑.

⭐ Exam Favorite: Increased afterload (e.g., hypertension) causes an ↑ in aortic pressure. The ventricle must generate more pressure to open the aortic valve, leading to a ↑ ESV and a ↓ stroke volume, narrowing the PV loop.

Clinical Correlations - Pressure Problems

↑ Afterload (e.g., Hypertension, Aortic Stenosis):
- LV must generate much higher pressure to overcome aortic/systemic resistance.
- Prolongs the isovolumetric contraction phase.
- Leads to concentric hypertrophy over time.
Impaired Myocardial Relaxation (e.g., Diastolic Dysfunction, LVH):
- A stiff ventricle relaxes slowly, increasing the time for pressure to fall.
- Prolongs the isovolumetric relaxation phase.
- Can lead to elevated left atrial pressure.

PV loops: increased afterload and diastolic dysfunction

⭐ In severe aortic stenosis, isovolumetric contraction is markedly prolonged because the LV must generate extreme pressure (e.g., >180 mmHg) to force open the calcified, stenotic aortic valve.

High‑Yield Points - ⚡ Biggest Takeaways

Isovolumetric contraction is the interval between mitral valve closure (S1) and aortic valve opening.

During this phase, all four heart valves are closed, and ventricular pressure rapidly increases while volume is constant.

It aligns with the QRS complex on an EKG.

Isovolumetric relaxation occurs after aortic valve closure (S2) and ends with mitral valve opening.

All valves are again closed as ventricular pressure sharply falls with no change in volume.

This phase corresponds to the latter part of the T wave.

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