From the Guidelines
Early IABP deflation decreases coronary perfusion time. When an intra-aortic balloon pump (IABP) is used, the timing of inflation and deflation is critical for maximizing therapeutic benefit. The balloon normally inflates during diastole, which increases coronary perfusion by augmenting diastolic pressure. According to the study by 1, the use of IABP in patients with acute myocardial infarction complicated by cardiogenic shock did not show improved survival compared to conservative care, but the timing of device insertion and variability of shock severity may have influenced the results.
The IABP’s main mechanism of action is a reduction of afterload and increased diastolic coronary perfusion via electrocardiogram triggered counterpulsation, as stated in the study by 1. When the balloon deflates too early in the cardiac cycle, it shortens the period of increased diastolic pressure, thereby reducing the time available for coronary perfusion. This premature deflation fails to provide the full intended benefit of diastolic augmentation that supplies oxygen-rich blood to the coronary arteries.
Proper IABP timing should maintain inflation throughout diastole to optimize coronary blood flow, especially important in patients with compromised cardiac function who require enhanced myocardial oxygen delivery. Key points to consider include:
- The IABP reduces heart work and myocardial oxygen consumption, favourably modifying the balance of oxygen demand/supply 1.
- Early deflation would not primarily affect myocardial workload, end diastolic pressures, or peripheral vascular resistance as significantly as it affects coronary perfusion time.
- The protective mechanisms associated with MCS in AMI are supported by extensive preclinical data beginning in the late 1970s 1.
In clinical practice, it is essential to prioritize the timing of IABP inflation and deflation to maximize the therapeutic benefits and minimize potential complications. The study by 1 highlights the importance of considering the timing of device insertion and the severity of shock when using IABP in patients with acute myocardial infarction complicated by cardiogenic shock.
From the Research
Effects of Early IABP Deflation
- Early IABP deflation can have several effects on the cardiovascular system, including:
- Decrease in coronary perfusion time: Early deflation can reduce the time available for coronary perfusion, which can negatively impact myocardial oxygen supply 2, 3.
- Increase in myocardial workload: Premature deflation can increase afterload during early ejection, leading to increased myocardial workload 3.
- Increase in peripheral vascular resistance: Late deflation can increase afterload during early ejection, which can lead to increased peripheral vascular resistance 3.
- No direct effect on augmented end diastolic pressures: The available evidence does not suggest a direct effect of early IABP deflation on augmented end diastolic pressures.
Mechanisms and Effects
- The intraaortic balloon pump (IABP) works by augmenting diastolic coronary perfusion pressure and reducing systolic afterload, which can improve myocardial oxygen supply-demand ratio and increase cardiac output 4.
- Properly timed IABP can decrease left ventricular end-systolic volume and pressure, and increase stroke volume and stroke work 3.
- However, timing errors, such as premature inflation or late deflation, can have negative effects on left ventricular performance and mechanical dyssynchrony 3.