Intraaortic balloon pump counterpulsation

INTRODUCTION — An intraaortic balloon pump (IABP) is a type of mechanical circulatory support (MCS) device used to quickly provide MCS in an array of clinical scenarios such as cardiogenic shock or persistent myocardial ischemia during myocardial infarction.

The basic principles regarding use of the IABP are presented here. Its efficacy in different clinical conditions is discussed on the appropriate topic reviews. Use of other circulatory assist devices, the cardiopulmonary assist device and the left ventricular assist device, is discussed elsewhere. (See "Short-term mechanical circulatory assist devices".)

TECHNICAL ASPECTS — IABPs are widely available and are the simplest devices to deploy among the various temporary mechanical circulatory support devices. The IABP system is composed of two principal parts:

●A flexible catheter with one lumen that allows for either distal aspiration/flushing or pressure monitoring and a second that permits the periodic delivery and removal of helium gas to a closed balloon. The balloons are manufactured in sizes between 20 and 50 cc.

●A mobile console that contains the system for helium transfer as well as computer control of the inflation and deflation cycle.

The catheter is inserted in most cases through a common femoral artery and advanced under fluoroscopic guidance such that the distal end is positioned in the proximal descending aorta, usually about one centimeter distal to the origin of the left subclavian artery. Alternative percutaneous insertion sites, such as the subclavian and axillary arteries, have been reported [1,2].

Pumping is initiated and controlled by the console using input from both the aortic pressure and the electrocardiogram. Inflation occurs immediately after aortic valve closure and deflation just before aortic valve opening (waveform 1 and figure 1). Using software algorithms, current generation systems are capable of monitoring many aspects of both efficacy and safety, reducing the time required by health care personnel to directly supervise or manually adjust the pump settings.

ROUTINE CARE — The following routine care measures likely decrease complication rates:

●A chest radiograph should be obtained after initial insertion and daily to document the position of the catheter tip, which should be at the level of bifurcation of left and right main bronchi (image 1).

●Documentation of the distal pulses should occur before, after, and three times every day.

●The pressure wave form should be evaluated by a practitioner knowledgeable with the use of the system twice daily.

●Daily measurement of the hematocrit, platelet count, and creatinine.

●Systemic intravenous anticoagulation with unfractionated heparin. While some experts may not anticoagulate if the pump is set to a 1:1 ratio (mechanical inflation:heart beats), the contributors to this topic use systemic anticoagulation with the pump at a ratio of 1:1 unless there is systemic bleeding or a duration of support less than four to six hours.

HEMODYNAMIC EFFECTS

Changes in hemodynamics — The IABP has two main hemodynamic effects:

●Blood is displaced to the proximal aorta by inflation during diastole.

●Aortic volume (and thus afterload) is reduced during systole through a vacuum effect created by rapid balloon deflation.

These effects may be quite variable, and they depend upon the volume of the balloon, its position in the aorta, heart rate, rhythm, the compliance of the aorta, and systemic resistance [3]. The higher the arterial elastance, which is determined in part by compliance, the greater the hemodynamic improvement from IABP counterpulsation [4]. Despite this variability, expected changes in the hemodynamic profile in the majority of patients with cardiogenic shock include (figure 2):

●A decrease in systolic pressure by 20 percent.

●An increase in aortic diastolic pressure by 30 percent, which may increase coronary blood flow to territory perfused by a vessel with a critical stenosis.

●An increase in mean arterial pressure especially in patients with shock due to an acute mechanical abnormality such as mitral regurgitation (MR) or ventricular septal defect (VSD) or to improvement in perfusion of a territory resulting in overall improved ventricular function.

●A reduction of the heart rate by less than 20 percent.

●A decrease in the mean pulmonary capillary wedge pressure by 20 percent.

●An elevation in the cardiac output by 20 percent, especially in patients with MR, VSD, or a large territory of medically refractory ischemia that is improved with the use of an IABP.

In addition, IABP counterpulsation reduces mean systemic impedance and developed systolic pressure, and causes a 14 percent decline in calculated peak left ventricular wall stress. The reductions in afterload and wall stress lead to a fall in myocardial oxygen consumption, a goal of treatment of patients with myocardial ischemia. (See "Approach to the patient with suspected angina pectoris", section on 'Pathophysiology'.)

Effects on coronary artery blood flow — The IABP has a variable effect on total coronary blood flow. Some studies have found little or no change in coronary blood flow [5,6], while others noted a significant augmentation [7,8].

Increased blood flow is most likely to occur in coronary vascular beds maximally dilated by ischemia, a setting in which autoregulation is at a maximal level and flow becomes pressure-dependent [7,8]. As an example, autoregulation of the peripheral coronary bed tends to maintain flow across a stenotic area until the severity of the stenosis is sufficient to produce a distal perfusion pressure of 40 to 50 mmHg. At lower pressures, autoregulation is maximal and coronary flow to the territory affected by the stenosis cannot be maintained. IABP counterpulsation is able to enhance blood flow to these areas via an increase in perfusion pressure.

Timing of inflation and deflation — Optimal timing of the inflation and deflation can increase the clinical efficacy of the IABP, while suboptimal timing can reduce the efficacy of the IABP or lead to adverse hemodynamics.

●Early balloon deflation – Early deflation of the IABP reduces balloon-induced diastolic flow and pressure augmentation and eliminates or reduces the afterload-reducing effect of the IABP. These effects can result in a loss of "assisted systole" beats and loss of augmented coronary blood flow (retrograde blood flow in the coronary arteries can occur).

●Early balloon inflation – Early inflation leads to the IABP acting against the systolic effort of the heart (ie, "stepping on systole"), which increases LV afterload and decreases cardiac output.

●Late balloon deflation – Late deflation may result in increased afterload during early systole and worsen LV cardiac output and myocardial oxygen requirements.

●Late balloon inflation – Late inflation will shorten the period of diastolic augmentation reducing blood pressure support and benefits of increased diastolic coronary blood flow.

The approach to correcting these abnormalities requires experience with troubleshooting of the algorithms that govern pump timing or with manual operation of the IABP timing and inflation parameters.

INDICATIONS — An IABP may be an effective temporary therapeutic option for a number of clinical situations [9,10]:

●Cardiogenic shock (left ventricular failure or mechanical complications of an acute myocardial infarction)

●Intractable angina

●Low cardiac output after cardiopulmonary bypass

●Adjunctive therapy in high risk or complicated angioplasty [11,12]

●Prophylaxis in patients with severe left main coronary arterial stenosis in whom surgery is pending [13]

●Intractable myocardial ischemia awaiting further therapy

●Refractory heart failure as a bridge to further therapy

●Intractable ventricular arrhythmias as a bridge to further therapy

Refractory myocardial ischemia — Use of an IABP reduces electrocardiographic ST-segment abnormalities in patients with acute coronary syndromes, and is effective in the treatment of angina unresponsive to medical therapy that cannot be treated promptly with percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery (CABG) [14,15]. However, the availability of effective medical therapy and prompt revascularization has all but eliminated this indication. Rarely, patients with surgical disease and persistent ischemia do require IABP support pending surgery.

Cardiogenic shock — An IABP can be used for the treatment of cardiogenic shock.

There was no mortality benefit at 30 days or at six years associated with use in 600 acute MI patients with cardiogenic shock randomized in the IABP-Shock II trial [16,17]. The use of an IABP in patients in this setting is discussed in detail elsewhere. (See "Prognosis and treatment of cardiogenic shock complicating acute myocardial infarction", section on 'Intraaortic balloon pump'.)

High-risk percutaneous coronary intervention — We do not suggest routine placement of an IABP electively before PCI in high-risk (as defined in the BCIS-1 trial discussed below) patients. However, placement of an IABP prior to PCI is potentially of benefit in those patients who are hemodynamically unstable before the procedure, or those who are judged highly likely to become unstable during the procedure. While the IABP does not have a US Food and Drug Administration indication for this use, the Impella percutaneous ventricular assist device does. (See "Short-term mechanical circulatory assist devices", section on 'Left ventricle to aorta'.)

Prophylactic placement of an IABP has been advocated to improve outcomes in both stable patients and patients with acute coronary syndromes undergoing high-risk or complicated PCI [11,12,18,19]. Such recommendations have been based on the results of small, observational studies that were subject to selection bias and which were carried out before stenting and aggressive antiplatelet therapies were routine.

However, the elective placement of an IABP was not found to improve outcomes in the BCIS-1 trial in which 301 high-risk patients were randomly assigned to either elective insertion of IABP before PCI or not [20]. High risk was defined as severe left ventricular dysfunction (left ventricular ejection fraction ≤30 percent; mean = 24 percent) and complex, multivessel coronary artery disease. Rescue placement of an IABP was allowed in the no planned IABP group for procedural complications of prolonged hypotension, pulmonary edema, or refractory ventricular arrhythmias.

There was no significant difference in the occurrence of the primary endpoint of major adverse cardiovascular and cerebral events (death, acute myocardial infarction, cerebrovascular event, or further revascularization) at 28 days (15.2 and 16.0 percent respectively; odds ratio 0.94, 95% CI 0.51-1.76). Cross-over from no IABP to IABP placement occurred in 12 percent. However, after a median follow-up of 51 months, all-cause mortality was lower among those who received an IABP (28 versus 39 percent; hazard ratio 0.66, 95% CI 0.40-0.98) [21]. The Kaplan-Meier curves appear to continue to diverge at five years.

Primary PCI for acute MI — An IABP is not routinely used in patients undergoing primary PCI without shock. This issue was evaluated in the CRISP-AMI trial that randomized 337 patients to IABP or no IABP. There was no significant difference in infarct size (42.1 percent [95% CI 38.7-45.6 percent] versus 37.5 percent [95% CI 34.3-40.8 percent], respectively; difference of 4.6 percent [95% CI -0.2 to 9.4 percent], p = 0.06) [22]. This issue is discussed in detail elsewhere. (See "Primary percutaneous coronary intervention in acute ST-elevation myocardial infarction: Periprocedural management", section on 'Intraaortic balloon counterpulsation'.)

Refractory ventricular arrhythmias — An IABP can contribute to the management of medically refractory ventricular tachycardia and/or ventricular fibrillation in selected patients. This includes those with severely impaired left ventricular function, those in whom the arrhythmia compromises hemodynamic status, and those for whom an IABP may provide time to implement appropriate therapy, including arrhythmia ablation, durable ventricular assist device, transplantation, or palliative care [23].

Refractory heart failure — An IABP has been used as a bridge to the long-term management of refractory heart failure. This issue is discussed elsewhere. (See "Management of refractory heart failure with reduced ejection fraction", section on 'Mechanical circulatory support'.)

Other potential uses — Other possible indications for IABP placement include mechanical complications of acute myocardial infarction such as acute ventricular septal defect and mitral regurgitation [24], inability to wean from cardiopulmonary bypass support [25], and severe/critical aortic stenosis in patients scheduled to undergo aortic valve replacement. (See "Early cardiac complications of coronary artery bypass graft surgery", section on 'Low cardiac output' and "Medical management of symptomatic aortic stenosis", section on 'Patients awaiting valve replacement' and "Acute myocardial infarction: Mechanical complications".)

The prophylactic placement of an IABP prior to CABG has been performed in patients with left main coronary artery stenosis, severely depressed left ventricular systolic function, diffuse coronary artery disease, and redo surgery [13]. The decision of whether or not to implant an IABP prior to CABG is usually jointly made by the cardiac surgeon and invasive cardiologist integrating these factors and anticipated risk for decompensation at the time of induction of anesthesia.

CONTRAINDICATIONS — The following conditions are contraindications to IABP insertion:

●Absolute contraindications:

•Significant (more than mild) aortic regurgitation since the degree of aortic regurgitation will be increased by IABP counterpulsation. (See "Clinical manifestations and diagnosis of chronic aortic regurgitation in adults" and "Echocardiographic evaluation of the aortic valve".)

•Aortic dissection or clinically significant aortic aneurysm. (See "Clinical features and diagnosis of abdominal aortic aneurysm" and "Management of asymptomatic abdominal aortic aneurysm".)

•Uncontrolled sepsis.

●Relative contraindications:

•Uncontrolled bleeding disorder.

•Known aortic atheroma or severe atherosclerosis.

•Severe peripheral artery disease that cannot be pretreated with stenting. Insertion can be carried out in patients with aorto-bifemoral bypass grafts.

•Left ventricular outflow tract obstruction.

•Inability to achieve adequate timing of IABP inflation and deflation due to tachycardia or irregular rhythms (eg, atrial fibrillation, frequent ventricular ectopy).

DURATION OF USE — Hemodynamic support with an IABP should be continued as long as the benefits outweigh the risks. It should be removed as soon as the patient stabilizes or sooner for complications, which are discussed directly below. The risk of complications increases with the duration of implantation.

When the etiology of hemodynamic compromise necessitating mechanical support is thought to be transient, periodic weaning trials (ie, periods of support at a lower ratio of inflations to heart beats) can help determine optimal timing of IABP removal. In cases where the indication is not expected to reverse without a definitive intervention (eg, revascularization), the IABP can remain in place for as long as needed to bridge the patient to that definitive procedure. Meticulous care of the catheter, as well as close monitoring of distal circulation for vascular compromise, are necessary. When prolonged need for IABP support is expected (eg, >10 to 14 days), insertion via axillary approach should be considered.

COMPLICATIONS — Complications associated with the IABP may be divided into vascular and nonvascular events. In the above review of almost 17,000 patients who had an IABP inserted from 1996 to 2000, the incidence of any complication was 7 percent, while major complications (major acute limb ischemia, severe bleeding, balloon leak, death related directly to the IABP insertion or IABP failure) occurred in 2.6 percent [10]. The in-hospital mortality was 21 percent, one-half of which occurred while the IABP was in place. IABP-related mortality was only 0.5 percent.

Vascular — Vascular complications (occurring in six to 25 percent of cases) remain the major risk associated with IABP use [26-28]. The most common major complications include:

●Limb and visceral ischemia

●Vascular laceration necessitating surgical repair

●Major hemorrhage

It is important that the IABP be inserted into the common femoral artery rather than one of its branches (eg, the superficial or profunda femoral artery). Neither of the branches is generally large enough to permit insertion without producing arterial obstruction and limb ischemia. Improper insertion from a needle puncture which is too low is the most common cause of ischemic complications during IABP use, and will often require removal of the IABP and contralateral insertion.

Arterial dissection is most often due to improper advancement of the guidewire with subsequent insertion of the IABP into a false lumen. The balloon may function normally in this position. Dissection may be diagnosed by ultrasonography and requires immediate balloon removal.

Less common vascular complications related to IABP use include spinal cord ischemia and visceral ischemia (including renal ischemia). In one study of 63 cardiac surgical patients who underwent IABP placement and who received both chest radiography and a computerized tomographic (CT) imaging study, the balloon was correctly positioned in only 62 percent [29]. In 61 patients, compromise of at least one visceral artery was found by CT; this was attributable to use of a balloon with a length longer than optimal for the patient’s anatomy in about 68 percent of cases.

Other — Other complications include [25-28,30-35]:

●Additional complications include thrombocytopenia, hemolysis, seromas, groin infection, and peripheral neuropathy.

●Balloon rupture is an uncommon event and is typically related to the balloon pumping against a calcified plaque or long-term IABP use. Balloon rupture can result in helium embolization and thrombus formation on or within the balloon.

Most modern consoles can detect the loss of balloon pressure caused by a rupture and will automatically alarm, withdraw helium from the balloon, and shut down. Balloon rupture may manifest as the presence of blood in the IABP lumen and can occur prior to a console alarm if the leak is small. Emergency management of balloon rupture includes the following steps:

•Turn off the IABP console

•Place the patient head-down

•Remove the IABP as soon as possible

Thrombus formation in the balloon may prevent percutaneous removal [34]. If this occurs, surgical exploration and removal may be necessary.

●Cholesterol embolization is an infrequent occurrence that may result in limb loss [31]. This complication should be suspected in patients with thrombocytopenia, livedo reticularis, eosinophilia, and, with renal atheroemboli, eosinophils in the urine sediment. Chronic anticoagulation may be detrimental in this setting, promoting further embolization [32]. The IABP should be removed in the presence of diagnosed or suspected cholesterol embolization. (See "Embolism from atherosclerotic plaque: Atheroembolism (cholesterol crystal embolism)".)

●Cerebrovascular accident is a rare complication of IABP use, since the balloon is normally positioned distal to the left subclavian artery. Cerebral ischemia only occurs when the IABP has been placed too proximally or has accidentally migrated proximally, or the central balloon lumen has been flushed vigorously and dislodged a thrombus.

●Sepsis is uncommon unless IABP use continues for more than seven days. This observation suggests that infections can be minimized by meticulous attention to sterile technique, analogous to the care given to parenteral nutrition lines [33].

Factors increasing IABP complications — The following factors are associated with an increase in the probability of vascular complications [10,25,35-38]:

●Peripheral artery disease

●Older age

●Female sex

●Diabetes mellitus

●Hypertension

●Prolonged support

●Larger catheter size (>9.5 French)

●Body surface area <1.8 m²

●Cardiac index <2.2 L/min/m²

The higher complication rate in women is most likely related to the size of the iliac and femoral arteries. Patients with diabetes and hypertension suffer more vascular complications due to an increased incidence of peripheral arterial disease.

Clinical expertise is likely important. In an analysis from the National Registry of Myocardial Infarction-2 (NRMI-2) in which 12,771 patients with an acute MI complicated by cardiogenic shock underwent IABP placement, the mortality rate was significantly higher in hospitals with a low volume of IABP insertions [39].

Factors decreasing IABP complications — The following are associated with a decreased incidence of complications:

●Sheathless technique [25,35,40,41]

●Smaller balloon size [25,35]

SUMMARY AND RECOMMENDATIONS

●Technical aspects – Intraaortic balloon pumps (IABPs) are widely available and are the simplest device to deploy among the various temporary mechanical circulatory support devices. (See 'Technical aspects' above.)

●Hemodynamic effects – Expected changes in the hemodynamic profile in the majority of patients with cardiogenic shock include: a decrease in systolic pressure; an increase in diastolic pressure, which may raise coronary blood flow to territory perfused by a vessel with a critical stenosis; a reduction of the heart rate; a decrease in the mean pulmonary capillary wedge pressure; and an elevation in the cardiac output. (See 'Hemodynamic effects' above.)

●Indications – Common situations where an IABP is used include:

•Cardiogenic shock – Cardiogenic shock that is not quickly reversed with pharmacologic therapy

•Acute mitral regurgitation – Acute mitral regurgitation, particularly due to papillary muscle or ventricular septal rupture.

•High-risk PCI – We suggest not routinely placing an IABP even in high-risk patients with planned percutaneous coronary intervention (PCI). High risk is defined as those with a left ventricular ejection fraction ≤30 percent and complex multivessel coronary artery disease. (See 'High-risk percutaneous coronary intervention' above.)

•Refractory symptoms of myocardial ischemia – We suggest placing an IABP in patients with recurrent ischemic chest discomfort despite maximal medical therapy who have signs of hemodynamic instability in whom revascularization with either PCI or coronary artery bypass surgery is planned. (See 'Refractory myocardial ischemia' above.)

●Contraindications – Contraindications to IABP insertion include (see 'Contraindications' above):

•Significant (more than mild) aortic regurgitation

•Abdominal aortic aneurysm or aortic dissection

•Uncontrolled sepsis

•Uncontrolled bleeding disorder

●Complications – Common and potentially life-threatening complications include (see 'Complications' above):

•Limb and visceral ischemia

•Vascular laceration necessitating surgical repair

•Major hemorrhage

ACKNOWLEDGMENTS — The UpToDate editorial staff acknowledges Julian M Aroesty, MD, and Duane Pinto, MD, MPH, who contributed to earlier versions of this topic review.