IABP (Intra-aortic balloon pump)
Intra-aortic balloon counterpulsation devices are positioned in the descending thoracic aorta. Depending on the manufacturer, they have balloon volumes ranging from 30 to 50 mL, balloon lengths from 16.5 to 26 cm, and shaft lengths from approximately 60 to 72 cm.
The device is inserted through the femoral artery using the standard Seldinger technique, ensuring the tip is 2 to 3 cm below the left subclavian artery. Systems of 7F to 8F are utilized. Its advantages include the feasibility of insertion in the cardiac catheterization laboratory, operating room, or at the bedside. The balloon is inflated at the aortic dicrotic notch and deflated immediately before systole. The IABP now uses helium for inflation. Helium is inert, less soluble, and potentially more toxic than the previous use of carbon dioxide in case of a gas leak in the circulation. Nevertheless, helium enables faster inflation-deflation cycles and greater timing precision.
It is essential to locate the balloon below the origin of the left subclavian artery at the upper margin and above the renal arteries at the lower. Research on this segment's length in Japanese patients revealed measurements between 21 to 25 cm, showing a strong correlation between the lengths of this segment and patient height. However, in the shorter Japanese demographic, the balloon lengths often surpassed the individual patients' 'safe zone' length.
Recommendations differ among manufacturers: a 50-mL size is typically recommended for patients taller than 6 feet (183 cm), whereas the 25-mL size is for patients shorter than 5 feet (152 cm). Recent technological advancements have introduced large diameter balloons for shorter patients (e.g., a 50-mL IABP on an 8 F shaft is now available for patients 5′ 4″ [162 cm] and taller).
Balloons are usually made from polyurethane or polyethylene, with materials selected to enable rapid inflation and deflation cycles, tolerating an average of 100,000 to 150,000 cycles per day.
IABPs are powered by intricately designed consoles featuring advanced artificial intelligence that can recognize electrocardiographic rhythms and hemodynamics. These consoles trigger balloon inflation from the ECG (including paced rhythms) or pressure waveforms.
The first significant multicenter trial was initiated after the initial positive experience with intra-aortic counterpulsation in critically ill patients experiencing cardiogenic shock (CS). This trial demonstrated notable hemodynamic benefits but only achieved a 17% survival rate to discharge. Over the next four decades, several incremental enhancements were made, leading to the implementation of a percutaneous method, the addition of a second lumen to support guidewire balloon advancement through circulation, increased automation of control consoles, and the development of progressively lower-profile and prefolded balloons.
ECG
Arterial pressure
Balloon pressure
Systolic Unloading
The pump deflates during systole, which reduces afterload and increases cardiac output. As a result, this lowers oxygen demand. While cardiac output during the ejection phase typically improves with unloading, the degree of increase in cardiac output is limited by the overall reserve of left ventricular (LV) systolic function.
Diastolic Augmentation
The pump inflates during diastole, increasing coronary perfusion pressure. However, increases in diastolic pressure, and thus coronary perfusion pressure, may not enhance coronary flow because autoregulation influences this potential. In normal patients, end organs capable of autoregulation sustain flow without significant changes.
Incorrect timing
Mild lower systolic pressure
Unssisted EDP
Assisted EDP
Correct timing
Mild lower systolic pressure with diastolic augmentation
Assisted EDP < Unassisted EDP
Early inflation (Inflation before the dicrotic notch)
Early inflation leads to elevated afterload during the late phase of left ventricular (LV) ejection, consequently impairs LV systolic function. (Balloon inflates during late systole)
Late inflation (Inflation after the dicrotic notch)
Early deflation reduces augmented left ventricular stroke volume and results in decreased peak diastolic coronary velocity.
Early deflation, occurring before left ventricular systole, causes the reversal of both coronary and other organ flows, such as in the brain, back into the aorta.
Late Deflation (deflation after systole):
Interferes with ventricular ejection and decreases stroke volume. (Balloon remains inflated in early systole)
Indication for IABP insertion
1) Angina that does not respond to medical therapy.
2) Cardiogenic shock.
3) Mechanical complications of myocardial infarction, including severe mitral regurgitation and ventricular septal defect.
4) Severe stenosis of the left main coronary artery.
5) Patients undergoing high-risk percutaneous coronary intervention or following primary angioplasty in the context of acute myocardial infarction.
Contraindication for IABP insertion
1) Moderate or severe aortic regurgitation
2) Aortic dissection
3) Aortic aneurysm
4) Patent ductus arteriosus
5) Severe peripheral vascular disease
6) Bleeding disorders
7) Severe sepsis.
References
Bonow, Robert O.; Mann, Douglas L. ; Zipes, Douglas P.; Libby, Peter. Braunwald's Heart Disease E-Book . Elsevier Health Sciences. Kindle Edition.
Parrillo, Joseph E.; Dellinger, R. Phillip. Critical Care Medicine E-Book: Principles of Diagnosis and Management in the Adult. Elsevier Health Sciences. Kindle Edition.