Basics
Description
- Aortic counterpulsation is a means of assisting the failing heart by automatically removing arterial blood just before and during ventricular ejection and returning it to the circulation during diastole.
- Extracorporeal counterpulsation was 1st introduced in 1961.
- Intraaortic balloon pump (IABP) insertion via sheath/dilator was described in 1980.
- IABP is a standard in circulatory assistance (100,000 placed in the U.S. in 1993).
- Counterpulsation improves the myocardial oxygen supply-demand balance. Inflation of the IABP during diastole displaces a volume of blood, increasing diastolic blood pressure. Rapid balloon deflation just prior to systolic ejection reduces afterload and myocardial work.
- Hemodynamic effects:
- Decrease in systolic arterial pressure
- Increase in diastolic arterial pressure
- No change in mean arterial pressure
- Decrease in pulmonary capillary wedge pressure
- Increase in cardiac output
- Increase or no change in coronary blood flow
- Increase in urine output
- Recently, enhanced external counterpulsation (sequential inflation of three cuffs from ankle to thigh on each leg during diastole) has been associated with fewer anginal episodes and with longer exercise duration without ECG evidence of ischemia.
Treatment
Indications for IABP:
- Acute coronary syndrome with:
- Cardiogenic shock
- Recurrent ischemic discomfort and signs of hemodynamic instability, poor LV function, or large area of myocardium at risk
- Refractory ventricular tachycardia
- Refractory pulmonary congestion
- Mechanical complications of acute MI (mitral regurgitation [MR] or ventricular septal defect [VSD])
- Percutaneous coronary intervention in patients with:
- Hemodynamic instability
- High risk or complicated coronary intervention
- Cardiac surgery in patients with:
- Severe LV dysfunction
- Severe left main coronary artery stenosis
- Repeat coronary artery bypass surgery (CABG)
- Critical aortic stenosis:
- Postcardiotomy cardiogenic shock
- Hemodynamic support while awaiting transplant
- Absolute contraindications:
- Significant aortic insufficiency
- Aortic dissection
- Relative contraindications to femoral placement:
- Abdominal aortic aneurysm
- Severe calcific aortoiliac or femoral arterial disease
- Recent groin incision at proposed site
- Surgeons may place via intrathoracic route if femoral route not possible.
General Measures
- IABP insertion:
- Balloon catheter is introduced over wire via common femoral artery.
- Balloon diameter should not be >80-90% of aortic diameter; the 40 mL balloon is adequate for most adults (30-34 mL if small, 50 mL if very large patient).
- Tip of catheter is placed in descending aorta, just distal to left subclavian artery.
- Balloon is inflated at dicrotic notch and deflated during isovolumic contraction (pressure monitored via central lumen in IABP catheter).
- If ECG is used to control balloon, inflation occurs on T-wave, deflation on R-wave.
- Note: If patient is in atrial fibrillation, deflation on the R-wave is the preferred timing method to prevent ventricular contraction against an inflated balloon during a short R-R cycle.
- IABP timing should be adjusted while assisting every other beat (1:2) so that assisted-beat waveforms can be compared with normal beats.
- IABP catheter is attached to bedside control/monitoring console.
- Helium gas (30-50 mL) is used to inflate balloon, due to its low viscosity (rapid shuttling needed in tachyarrhythmias).
- Management of IABP:
- Heparin anticoagulation with partial thromboplastin time 50-70 sec
- Evaluation of the involved limb for ischemia q2-6h
- Daily evaluation for evidence of sepsis, thrombocytopenia, blood loss, hemolysis, vascular obstruction, thrombus, embolus, or dissection
- Thrombocytopenia is expected due to traumatic platelet destruction, but counts rarely fall below 50,000-100,000/mL unless some other problem exists (eg, disseminated intravascular coagulation, heparin-induced thrombocytopenia).
- Monitoring for normal pressure waveform (normally rectangular appearance with brief overshoot and undershoot artifacts)
- If rounding of the waveform occurs, consider a kink in the balloon or connection tubing, an incompletely inflated balloon, or an oversized balloon.
- Patients are kept on bed rest, with restricted hip flexion and head of bed elevated no more than 30 degrees.
- Prophylactic antibiotics (eg, cefazolin) are not given routinely, but should be given at time of insertion if any compromise occurs in sterile technique.
- Daily CXR to evaluate for proper catheter tip position at the level of the carina
Ongoing Care
Prognosis
- 75% of patients who develop cardiogenic shock refractory to medication post-MI will respond to IABP therapy (ultimate outcome determined by coronary pathology; patients with operable disease achieve early survival as high as 93%).
- For ventricular septal rupture post-MI, IABP reduces left-to-right shunt; combined with urgent surgery allows 73-80% survival.
- For papillary muscle rupture post-MI, IABP increases coronary perfusion and reduces ischemic load, MR, and pulmonary capillary wedge pressure; mortality is related to extent of cardiac dysfunction and approaches 55%.
- For postcardiotomy cardiogenic shock, IAPB allows survival in 52-66%.
- 1-yr survival in patients who require IABP pretransplantation is 72-77%.
Complications
- Risk factors:
- DM
- Low cardiac index
- Female gender
- Peripheral vascular disease
- Extended use (eg, >5 days)
- Complication rates range from 6-46%.
- Balloon rupture is rare.
- Major complications in 4-17% (leg ischemia requiring thrombectomy or amputation, aortic dissection, aortoiliac laceration or perforation, and deep wound infection requiring debridement)
- Minor complications in 7-42% (bleeding at insertion site, superficial wound infection, asymptomatic loss of peripheral pulse, and lymphocele)
- Vascular complications are most common (6-24%). Most are due to insertion procedure.
- If leg ischemia develops, IABP should be removed; if ischemia persists, surgical exploration is indicated.
Additional Reading
1Aguirre FV. Intraaortic balloon pump support during high-risk coronary angioplasty. Cardiology. 1994;84:175-186. [View Abstract]2Antman EM. ACC/AHA guidelines for the management of patients with ST-elevation MI: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1999 Guidelines for the Management of Patients with Acute MI). Circulation. 2004;110:282-292.3Arora RR. The Multicenter Study of Enhanced External Counterpulsation (MUST-EECP): Effect of EECP on exercise-induced myocardial ischemia and anginal episodes. J Am Coll Cardiol. 1999;33:1833-1840. [View Abstract]4Baim D. Grossman's cardiac catheterization, angiography, and intervention, 7th ed. Philadelphia: Lippincott, Williams & Wilkins, 2006.5Baskett RJF. The intraaortic balloon pump in cardiac surgery. Ann Thoracic Surgery. 2002;74(4):1276-1287. [View Abstract]6Opie L. The heart. Orlando: Grune & Stratton, 1984.7Patel JJ. Prospective evaluation of complications associated with percutaneous intraaortic balloon counterpulsation. Am J Cardiol. 1995;76:1205-1207. [View Abstract]8Scheidt S. Intra-aortic balloon counterpulsation in cardiogenic shock. Report of a co-operative clinical trial. N Engl J Med, 1973;288:979-984. [View Abstract]9Stedman's medical dictionary, 25th edition. Baltimore: Williams & Wilkins, 1990.