Effects of Intra-Aortic Balloon Pump on Hemodynamics
The intra-aortic balloon pump (IABP) primarily increases diastolic pressure through balloon inflation during diastole, while decreasing afterload through balloon deflation just before systole. 1
Hemodynamic Effects of IABP
The IABP works through the principle of counterpulsation, producing several key hemodynamic effects:
- Increases diastolic pressure: The balloon inflates during diastole, causing a significant increase in diastolic pressure (approximately 80-83% augmentation) 1, 2
- Decreases afterload: The balloon deflates just before systole, reducing left ventricular afterload, which decreases myocardial work and oxygen consumption 1, 3
- Decreases pulmonary wedge pressure: By reducing afterload and improving cardiac output, IABP decreases left ventricular filling pressures 1
- Increases coronary blood flow: IABP significantly augments coronary blood flow velocity, particularly in patients with hypotension (systolic BP ≤90 mmHg) 1, 2
Timing Effects
- The IABP does not increase the duration of systole
- It does not decrease the duration of diastole
- Rather, it works within the cardiac cycle to optimize hemodynamics by:
- Augmenting diastolic pressure during balloon inflation
- Reducing systolic pressure during balloon deflation
Clinical Significance
The hemodynamic effects of IABP translate to several clinical benefits:
- Improved coronary perfusion due to increased diastolic pressure 1, 2
- Reduced myocardial oxygen demand due to decreased afterload 1, 3
- Increased forward cardiac output, particularly beneficial in acute severe mitral regurgitation 1
- Decreased regurgitant volume in valvular pathologies 1
Important Considerations
- IABP is most effective when coronary stenosis has been relieved, as it cannot significantly improve flow beyond critical stenoses 1, 4
- The greatest benefit in coronary flow augmentation occurs in patients with hypotension (systolic BP ≤90 mmHg) 1, 2
- In normal myocardium, IABP may actually decrease coronary blood flow by 8.4±2.2%, likely due to decreased myocardial oxygen demand from reduced afterload 5
- During reperfusion after ischemia, IABP increases coronary blood flow by 8-23.5%, suggesting it might help mitigate the no-reflow phenomenon 5
Contraindications
- Absolute contraindications include aortic regurgitation (even mild), aortic dissection, and aortic aneurysm 1, 3
- Relative contraindications include severe aortic stenosis and advanced peripheral and aortic vascular disease 1
In summary, of the options presented in the question, the IABP increases diastolic pressure (option c) while decreasing afterload (contrary to option b). It does not increase pulmonary wedge pressure (contrary to option a), increase duration of systole (contrary to option d), or decrease duration of diastole (contrary to option e).