The Question is from neet-zoology body-fluids-and-circulation regulation-of-cardiac-activity, and it was created by the author Mr. BALACHANDRA.N

Question

A patient exhibits a significantly reduced stroke volume despite a normal heart rate. Which of the following factors is LEAST likely contributing to this condition?

Mr. BALACHANDRA.N · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Stroke Volume and its Determinants
 **Related Topics**: Cardiac Output, Preload, Afterload, Contractility, Heart Failure
 **Prerequisites**: Understanding of cardiac physiology, particularly the Frank-Starling Law.
## SOLUTION PATHWAY
**Given Information**:
  Reduced stroke volume
  Normal heart rate
**Method & Steps**:
 1. Analyze the factors affecting stroke volume.
  Reasoning: Stroke volume (SV) is the amount of blood ejected from the left ventricle per beat.  It's determined by preload, afterload, and contractility.  $SV = EDV - ESV$, where EDV is end-diastolic volume and ESV is end-systolic volume.  Cardiac output (CO) is the product of heart rate (HR) and stroke volume: $CO = HR 	imes SV$.
  Formula/Rule:  Frank-Starling Law:  Increased preload leads to increased stroke volume (within physiological limits).
 2. Evaluate each option's impact on stroke volume.
  Working:
        * **Decreased myocardial contractility:** This directly reduces the force of ventricular contraction, leading to a lower stroke volume.
        * **Increased afterload:**  Higher resistance to ejection increases the pressure the ventricle must overcome, reducing the amount of blood ejected (lower SV).
        * **Increased venous return:** This increases preload (EDV), which typically increases stroke volume according to the Frank-Starling mechanism.
        * **Impaired ventricular filling:** This reduces preload (EDV), thus lowering the stroke volume.
  Key Point:  The question asks for the factor LEAST likely to contribute to reduced stroke volume.
 3. Identify the least likely contributor.
  Result: Increased venous return (option C) is the least likely contributor because it typically increases stroke volume.
  Verification:  All other options directly or indirectly lead to reduced stroke volume.  Increased venous return is the only option that should increase SV.
 ## OPTION ANALYSIS
A :x: Decreased myocardial contractility directly reduces stroke volume.
B :x: Increased afterload makes it harder for the heart to pump blood, reducing stroke volume.
C ✓: Increased venous return increases preload and therefore stroke volume.
D :x: Impaired ventricular filling reduces the amount of blood available to be ejected, thus decreasing stroke volume.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing preload and afterload: Understanding the difference between the volume of blood entering the ventricle (preload) and the resistance the ventricle faces when ejecting blood (afterload) is crucial.
  2.Ignoring the Frank-Starling Law: This law explains the relationship between preload and stroke volume, which is central to understanding this question.
 **Quick Tips**:
  1.Remember the factors that affect stroke volume (preload, afterload, contractility).
  2.Visualize the cardiac cycle and how each factor influences the amount of blood ejected.

Mr. BALACHANDRA.N · Answer

Decreased myocardial contractility

Mr. BALACHANDRA.N · Answer

Increased afterload

Mr. BALACHANDRA.N · Answer

The correct Option is "Increased venous return"

Mr. BALACHANDRA.N · Answer

Impaired ventricular filling

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