Question

A 48-year-old man with diet-controlled type 2 diabetes mellitus is being evaluated for occasional retrosternal chest pain. He has no history of hypertension, and his blood pressure measurements during office visits were always within normal limits. There is no family history of cardiovascular disease. The patient undergoes exercise treadmill stress testing. He walks for 7 minutes on the treadmill and stops due to fatigue but does not experience chest pain. His ECG does not show any abnormal changes. Heart rate ranges from 70/min at rest to 132/min at peak and mean blood pressure ranges from 95 mm Hg at rest to 112 mm Hg at peak.

Which of the following parameters was most likely decreased during peak stress compared to the resting state in this patient?

A. Cardiac output

B. Left ventricular end-diastolic pressure

C.Pulmonary artery systolic pressure

D. Systemic systolic blood pressure

E. Total systemic vascular resistance

Correct Answer: Total Systemic Vascular Resistance (TSVR) ↓

Reasoning: Vasodilation balances metabolic demands of exercising muscles.

• Framework:

  • 🔍 Start with what changes during exercise (HR, CO, BP).

  • ⚙️ Trace metabolic demands → vasodilation → TSVR ↓.

  • ⚖️ Compare incorrect options based on their mechanisms.

Exercise Induces Stress on the Cardiovascular System
⬇
⚙️ Sympathetic Nervous System Activation
🧠 Drives:

↑ Heart Rate (HR)

↑ Stroke Volume (SV)
⬇
🔍 Increased Cardiac Output (CO)
⚙️ CO = HR × SV
⬆ Ensures blood supply to muscles.
⬇
⚙️ Local Metabolic Changes in Skeletal Muscles

Analogy: Think of muscles as a "burning furnace" needing oxygen and nutrients:

↑ CO₂ (smoke)

↑ Lactate (byproduct)

↓ O₂ (fuel consumption).
⬇
⚖️ Metabolic Autoregulation → Vasodilation
🧠 Effect:

Arterioles open wide to meet muscle needs.
⬇
↓ Total Systemic Vascular Resistance (TSVR)
Correct Answer: E

Think Body as a Power Plant: Muscles (furnaces) demand more energy during exercise.

• 🔍 CO = Pump Speed × Water Volume: HR and SV rise to increase CO.

• Arterioles as Adjustable Pipes: Open wide (vasodilation) to deliver nutrients, reducing TSVR.

Explanation of Other Answers

A. Cardiac Output (CO)

• ⚙️ Mechanism: CO rises during exercise (↑ HR, ↑ SV).

• Analogy: Like turning up a water pump to meet the needs of thirsty plants.

• Incorrect: CO ↑, not ⬇️.

B. Left Ventricular End-Diastolic Pressure (LVEDP)

• ⚙️ Mechanism: ↑ Venous return = ↑ preload.

• Analogy: Think of filling a balloon; more blood stretches the ventricle.

• Incorrect: LVEDP ↑, not ⬇️.

C. Pulmonary Artery Systolic Pressure (PASP)

• ⚙️ Mechanism: ↑ CO → mild ↑ PASP to accommodate blood flow.

• Incorrect: PASP rises slightly during exercise.

D. Systemic Systolic Blood Pressure (SBP)

• ⚙️ Mechanism: ↑ CO drives ↑ SBP.

• Analogy: Like turning up the pressure in a hose to water distant plants.

• Incorrect: SBP ↑, not ⬇️.

Flashcards

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