Question

A 49-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: E. Total Systemic Vascular Resistance (TSVR)

🧠 Resting State:

⬇️

Normal cardiovascular baseline:

HR: 70/min, BP: 95 mm Hg, Normal TSVR.

⬇️

🧠 Exercise Initiation → ↑ Oxygen Demand in Skeletal Muscles:

Skeletal muscle activity ↑ metabolic demand.

↑ Local metabolite release (e.g., adenosine, CO₂, lactate).

⬇️

Vasodilation of arterioles (driven by metabolites)

⬇️

TSVR ↓ to maintain blood flow to muscles.

⬇️

🧠 Compensatory Mechanisms →

↑ Heart Rate (70 → 132/min).

↑ Stroke Volume initially (↑ Venous return).

↑ Cardiac Output (CO = HR × SV).

⬇️

🧠 Effects on Systemic BP:

Systolic BP ↑ (95 → 112 mm Hg): Driven by ↑ CO but limited by ↓ TSVR.

Diastolic BP may remain stable or slightly ↓ due to vasodilation.

⬇️

Other Clinical Findings Explained:

• No chest pain: Adequate coronary perfusion (no ischemia).

• Normal ECG: Exercise-induced cardiac workload is well-compensated.

• BP changes: Reflect normal exercise physiology (↑ CO, ↓ TSVR).

Explanation of Other Answers

Cardiac Output (A):

• ↑ during exercise to deliver more oxygenated blood to muscles.

Left Ventricular End-Diastolic Pressure (B):

• Remains stable or slightly ↑ due to enhanced venous return and ventricular compliance.

Pulmonary Artery Systolic Pressure (C):

• ↑ as cardiac output increases and more blood flows through the pulmonary circulation.

Systemic Systolic Blood Pressure (D):

• ↑ due to increased CO, despite TSVR ↓.

Flashcards

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