What is the primary effect of an intra-aortic balloon pump (IABP) on blood pressure?

Intra-aortic Balloon Pump Effects on Hemodynamics

The intra-aortic balloon pump (IABP) increases diastolic pressure while decreasing afterload, which is its primary hemodynamic effect. 1

Mechanism of Action

The IABP operates through counterpulsation, which creates specific hemodynamic effects:

• Inflation Phase (Diastole):

  • Increases diastolic aortic pressure by 80-83% 2
  • Enhances coronary blood flow velocity (67-115% increase) 2
  • Improves diastolic coronary perfusion 1

• Deflation Phase (Systole):

  • Decreases systolic aortic pressure (6% reduction) 2
  • Reduces left ventricular afterload 3, 1
  • Decreases myocardial work and oxygen consumption 1

Analysis of Answer Options

Let's analyze each option in the question:

a) Increases pulmonary wedge pressure - INCORRECT

• IABP decreases left ventricular filling pressures by reducing afterload and improving cardiac output 3

b) Increases afterload - INCORRECT

• IABP decreases afterload through balloon deflation just before systole 3, 1

c) Increases diastolic pressure - CORRECT

• IABP significantly increases diastolic pressure (80-83% from baseline) 2
• This is a primary mechanism by which IABP improves coronary perfusion 1

d) Increases duration of systole - INCORRECT

• IABP does not affect the duration of cardiac cycle phases 1

e) Decreases duration of diastole - INCORRECT

• IABP does not shorten diastole; it augments diastolic pressure without changing timing 1, 2

Clinical Implications

The hemodynamic effects of IABP translate to several clinical benefits:

• Improved coronary perfusion during diastole 2
• Reduced myocardial oxygen demand due to decreased afterload 1
• Increased forward cardiac output in acute severe mitral regurgitation 3
• Decreased regurgitant volume in valvular pathologies 3

Important Considerations

• IABP is most effective when coronary stenosis has been relieved, as it cannot significantly improve flow beyond critical stenoses 4
• The greatest benefit in coronary flow augmentation occurs in patients with hypotension (systolic BP ≤90 mmHg) 2
• While historically recommended for cardiogenic shock, recent evidence challenges routine use in this setting 3
• IABP is contraindicated in aortic regurgitation, as the increased diastolic pressure would worsen regurgitation 1

In summary, the IABP's primary hemodynamic effect is increasing diastolic pressure while simultaneously decreasing afterload, creating a favorable oxygen supply/demand balance for the myocardium.