**Intra-Aortic Balloon Counterpulsation Therapy and Its Role in Optimizing Outcomes in Cardiac Surgery**

Bharat Datt, Carolyn Teng, Lisa Hutchison and Manu Prabhakar *Southlake Regional Health Centre Canada* 

## **1. Introduction**

42 Special Topics in Cardiac Surgery

[107] Thielmann M, Massoudy P, Schmermund A, et al. Diagnostic discrimination between

graft-related and non–graft-related perioperative myocardial infarction with cardiac troponin I after coronary artery bypass surgery. Eur Heart J 2005;26:2440-7.

> Several discoveries and inventions in medicine have revolutionized it's practice. Examples would include the discovery of Insulin by Dr William Banting in 1920. The discovery of Heparin by Dr Jay McLean and its first clinical use in Toronto in 1933-36, the advent of the membrane oxygenator, heart lung machines with progressively smaller footprints, intra aortic balloon (IAB) pumps and VAD's (ventricular assist device) would be some of the devices which significantly impacted outcomes in cardiac surgery.

> The fundamentals of IAB technology were first tested by Harken in 1958, who is credited with the first use of diastolic augmentation. The pump for Harken's system was a failure due to massive hemolysis. Moulopoulous (in the 1960's) from the Cleveland Clinic developed the first successful prototype of an Intra-aortic balloon pump (IABP) which could be timed to the cardiac cycle.

> The IABP device as we know it was reported by Dr Adrian Kantrowitz (Fig 1) and his team from Grace Sinai hospital in Detroit. The first clinical implant was performed at Maimonides Medical Centre, Brooklyn, NY in Oct 1967 for a 48 yr old woman in cardiogenic shock unresponsive to traditional therapy. The IAB was inserted through a cut down of the left femoral artery (LFA) and pumping performed for 6 hrs. The shock was reversed and the patient discharged. The device was further developed for cardiac surgery by Dr David Bregman at New York Presbyterian Hospital in 1976.

> Studying the history of counterpulsation elucidates the great strides in IAB technology and its clinical applications. The size of the balloons initially inserted were as large as 15 Fr. Two operations were required for balloon usage, one to insert the balloon by cut down in a femoral artery, and a second operation to remove the balloon. Advances in technology afforded progressively smaller IAB catheter sizes and eventually 8 and 9Fr. balloons were developed. Current IAB catheter sizes are 7 and 7.5Fr.

In 1968 –Kantrowitz and his group began to use the IABP regularly in clinical practice. Since 1979 balloon placement utilizes the Seldinger (percutaneous) technique.

The wrapped IAB was developed in 1985. Advances in technology facilitated graduating from cut down insertions to percutaneous and sheathless insertions going from cut down insertions to percutaneous and finally sheathless insertions. Smaller diameter catheters permitted this along with user friendly consoles with automated and real time timing algorithms.

Intra-Aortic Balloon Counterpulsation Therapy

Fig. 2. Phases of electrical and mechanical contraction

of blood ejected by the Left Ventricle with every beat.

LVEDP, produces significant increases in stroke volume.

3. Inotropy or (ventricular contractility) and

**3. Cardiac output** 

1. Preload 2. Afterload

4. Heart rate

**4. Preload** 

**5. Afterload** 

Stroke volume is dependent on

and Its Role in Optimizing Outcomes in Cardiac Surgery 45

Cardiac output is the product of stroke volume and heart rate. Stroke volume is the amount

This concept suggests that the length of ventricular muscle fiber determines the magnitude of contraction. The length of the LV muscle fiber in turn is dependent upon the left ventricular end diastolic volume (LVEDP). In other words increase in left atrial filling would increase the magnitude of LV contraction. The ability of the LV to vary the strength of its contraction as a function of the LVEDP and end diastolic muscle fiber length is defined as Frank Starling law (fig 3). This gain in contractility is impaired when the stretch goes beyond physiological limits. In clinical practice the length of the muscle fiber is proportional to the LVEDP 'which is measured indirectly as the pulmonary artery wedge pressure (PAWP) by means of a Swan Ganz catheter. In a normal LV, very slight changes in PAWP or

Afterload is defined as the resistance to LV ejection. Major components are SVR and AEDP. AEDP is the resistance the LV has to overcome in order to open the aortic valve. Ninety percent of myocardial oxygen consumption takes place during the isovolumetric

Fig. 1. Datascope System 80
