Table of Contents
Effects of IABP Therapy
of the IABP
at a Single Center
In 1958 Harken described for the first time a method to treat left
ventricular failure by using counterpulsation or diastolic augmentation.
He suggested removing a certain blood volume from the femoral artery
during systole and replacing this volume rapidly during diastole. By
increasing coronary perfusion pressure this concept would therefore
augment cardiac output and unload the functioning heart simultaneously. This method of treatment was limited because
of problems with access (need for arteriotomies of both femoral
arteries), turbulence and development of massive hemolysis by the
pumping apparatus. Even experimental data showed that no augmentation of
coronary blood flow was obtained .
Then in the early 1960s Moulopoulus et al. from the Cleveland Clinic, developed an
experimental prototype of the intra-aortic balloon (IAB) whose inflation
and deflation were timed to the cardiac cycle. In 1968 the initial use
in clinical practice of the IABP and it`s further improvement was
realized resp. continued by A. Kantrowiz`s group.
In its first years, the IABP required surgical insertion and surgical
removal with a balloons size of 15 French. In 1979 after subsequent
development in IABP technology a dramatic headway with the introduction
of a percutaneous IAB with a size of 8,5 to 9,5 French was achieved. This advance made it for even nonsurgical
personnel possible, to perform an IAB insertion at the patientís
bedside. In 1985 the first prefolded IAB was developed.
Today continued improvements in IABP technology permit safer use and
earlier intervention to provide hemodynamic support. All these
progresses have made the IABP a mainstay in the management of ischemic
and dysfunctional myocardium.
Physiologic Effects of IABP Therapy
After correct placement of the IAB in the descending aorta with it`s
tip at the distal aortic arch (below the origin of the left subclavian
artery) the balloon is connected to a drive console. The console itself
consists of a pressurized gas reservoir, a monitor for ECG and pressure
wave recording, adjustments for inflation/deflation timing, triggering
selection switches and battery back-up power sources. The gases used for
inflation are either helium or carbon dioxide . The advantage of helium
is its lower density and therefore a better rapid diffusion coefficient.
Whereas carbon dioxide has an increased solubility in blood and thereby
reduces the potential consequences of gas embolization following a
Inflation and deflation are synchronized to the patientsí cardiac
cycle. Inflation at the onset of diastole results in proximal and distal
displacement of blood volume in the aorta. Deflation occurs just prior
to the onset of systole (Fig. 1) .
Figure 1: Intra aortic balloon (IAB) during systole and diastole
The primary goals of IABP treatment are to increase myocardial oxygen
supply and decrease myocardial oxygen demand. Secondary, improvement of
cardiac output (CO), ejection fraction (EF), an increase of coronary
perfusion pressure, systemic perfusion and a decrease of heart rate,
pulmonary capillary wedge pressure and systemic vascular resistance
There are several determinants of oxygen supply and demand
Table 1: Hemodynamic effects of IABP Therapy
Table 2: Determinants of Myocardial Oxygen Supply and
In particular systolic wall tension uses approximately 30% of
myocardial oxygen demand. Wall tension itself is affected by
intraventricular pressure, afterload, end-diastolic volume and
myocardial wall thickness. Regarding to the studies of Sarnoff et al.
the area under the left ventricular pressure curve, TTI (= tension-time
index ), is an important determinant of myocardial oxygen consumption. On the other hand, the integrated pressure
difference between the aorta and left ventricle during diastole (DPTI =
diastolic pressure time index) represents the myocardial oxygen supply
(i.e. hemodynamic correlate of coronary blood flow).
Figure 2: Schematic representation of coronary blood flow, aortic and
left ventricular pressure wave form with / without IABP. (Effects on
DPTI and TTI . Balloon inflation during diastole augments diastolic
pressure and increases coronary perfusion pressure as well as improving
the relationship between myocardial oxygen supply and demand (DPTI:TTI
- a) Inflation of the balloon during diastole (= augmentation of the
aortic diastolic pressure) increases coronary blood flow ( DPTI ).
- b) Deflation of the balloon occurs just prior to the onset of
systole and reduces impedance to left ventricular ejection (TTI ).
This results in less myocardial work, decreased myocardial oxygen
consumption and increased cardiac output.
Control of the IABP
To achieve optimal effect of counterpulsation, inflation and
deflation need to be correctly timed to the patientís cardiac cycle.
This is accomplished by either using the patientís ECG signal, the
patientís arterial waveform or an intrinsic pump rate. The most common
method of triggering the IAB is from the R wave of the patientís ECG
signal. Mainly balloon inflation is set automatically to start in the
middle of the T wave and to deflate prior to the ending QRS complex.
Tachyarrhythmias, cardiac pacemaker function and poor ECG signals may
cause difficulties in obtaining synchronization when the ECG mode is
used. In such cases the arterial waveform for triggering may be
TIMING and WEANING
It is important that the inflation of the IAB occurs at the beginning
of diastole, noted on the dicrotic notch on the arterial waveform.
Deflation of the balloon should occur immediately prior to the arterial
upstroke. Balloon synchronization starts usually at a beat ratio of 1:2.
This ratio facilitates comparison between the patientís own ventricular
beats and augmented beats to determine ideal IABP timing. Errors in
timing of the IABP may result in different waveform characteristics and
a various number of physiologic effects (Fig. 3).
Figure 3: Arterial pressure wave form alterations associated with
inflation and deflation of the IAB
If the patientís cardiac performance improves, weaning from the IABP
may begin by gradually decreasing the balloon augmentation ratio (from
1:1 to 1:2 to 1:4 to 1:8) under control of hemodynamic stability . After
appropriate observation at 1:8 counterpulsation the balloon pump is
Indications and Contraindications (Table 3)
Early purposed indications for intraaortic balloon pumping have
included cardiogenic shock or left ventricular failure, unstable angina,
failure to separate a patient from cardiopulmonary bypass and
prophylactic applications, including stabilization of preoperative
cardiac patients as well as stabilization of preoperative noncardiac
surgical patients. Today more extending indications are:
Cardiac patients requiring procedural support during coronary
angiography and PTCA, or as a bridge to heart transplantation. Further
on in pediatric cardiac patients and as well as in patients with stunned
myocardium, myocardial contusion, septic shock and drug induced
cardiovascular failure the IABP can be life-saving.
IABP therapy should only be considered only for use in patients who
have the potential for left ventricular recovery, or to support patients
who are awaiting cardiac transplantation. Absolute contraindications of
IABP are relatively few (Tab.3). There are successful reports of its
usage in patients with aortic insufficiency.
Table 3: IABP Counterpulsation Indications and
In the early years of IABP - therapy, insertion of the balloon was
performed by surgical cut down to the femoral vessels. After a
longitudinal incision in the groin, the femoral arteries were identified
and controlled. A vascular graft was then sewn to the common femoral
artery in an end-to-side fashion. The balloon was introduced into the
artery via the graft and properly positioned in the thoracic aorta and
the graft tightly secured to the distal portion of the balloon catheter.
Finally the skin incision was closed. Removal of the balloon required a
Since 1979, a percutaneous placement of the IAB via the femoral
artery using a modified Seldinger technique allows an easy and rapid
insertion in the majority of situations. After puncture of the femoral
artery a J-shaped guide wire is inserted to the level of the aortic arch
and then the needle is removed. The arterial puncture side is enlarged
with the successive placement of an 8 to 10,5Fr dilator/sheath
combination. Only the dilator needs to be removed.
Continuing, the balloon is threaded over the guide wire into the
descending aorta just below the left subclavian artery. The sheath is
gently pulled back to connect with the leak-proof cuff on the balloon
hub, ideally so that the entire sheath is out of the arterial lumen to
minimize risk of ischemic complications to the distal extremity.
Recently sheathless insertion kits are available. Removal of a
percutaneously placed IAB may either be via surgical removal or closed
technique. There are alternative routes for balloon insertion. In
patients with extremely severe peripheral vascular disease or in
pediatric patients the ascending aorta or the aortic arch may be entered
for balloon insertion. Other routes of access include subclavian,
axillary or iliac arteries.
Although the incidence of complications has decreased significantly
as experience with the device has increased, IABP therapy in todayís
patients` population does still hold a risk for complications (Tab.4).
Because todayís patient population is elderly (68 - 80 years), very
often female and may suffer from severe peripheral vascular disease and
hypertension or diabetes. The most common vascular complication is limb
ischemia. It may occur in 14-45% of patients receiving IABP therapy . Therefore the patient must be consistently
observed for any symptoms of ischemia during IABP counterpulsation. If
signs of ischemia appear the balloon should be removed. In general,
vascular injuries should be dealt with directly by surgical
interventions and repair. Balloon related problems and infection require
removal and / or replacement of the IAB .
Table 4: Complications of IABP counterpulsation
Experience at a Single Center
Treatment of low cardiac output syndrome using IABP counterpulsation
has been used at our institution since 1983. Till December 1993 a total
number of 440 patients (pts) (9,95%) out of 4420 patients, who underwent
cardiac surgery procedures with the use of cardiopulmonary bypass, were
supported with an IABP.(Age distribution : Tab. 6) There were 294 male
and 146 female patients. Overall survival rate after implantation of the
IABP was 75% (n=330 pts) .
Table 5: Diagnosis prior to IABP implantation
Table 6: Age Distribution of IABP patients
In the early years (1983-1989) as method of choice, implantation of
the balloon was performed via a surgical cut down of the femoral artery.
Complications were observed in 20 pts (8.4%) : In 9 pts (3.7%)
positioning of the balloon was impossible due to severe vascular
disease, 5 pts (2.1%) developed a thrombosis of the femoral artery and 1
patient (0.4%) died because of untreatable thrombosis of the mesenteric
artery. Hospital mortality in this group was 36% (survival rate of 64%).
Mean pumping time was 3 days (1 - 15).
Since 1990 we prefer the percutaneous insertion of the device. After
a learning curve more than 90% of 202 patients received an IABP using
this technique. Complication rate was less than 8% (mainly leg ischemia
with amputation of the leg in 1 patient, 3 infections of the puncture
point and 4 cases of impossible positioning of the balloon ). Survival
rate was 68.5% (hospital mortality of 31.5%) . 278 pts (63%) received
the balloon pump at the operating theater - mainly because of failure to
wean from cardiopulmonary bypass -151 pts (34,3%) at an intensive care
unit and 11 pts (2,5%) as a bridge to transplant. Table 6 shows a
detailed list of all various diagnoses prior to IABP therapy.