systole (Fig. 42.2) (see Chapter 7). These phases are important for understanding the mechanism of the IABP therapy because it uses the cardiac cycle to augment cardiac output during systole and coronary blood flow during diastole, a process called counterpulsation.
▪ FIGURE 42.1 Cutaway of heart and aorta showing placement of an IABP in aorta just distal to the subclavian artery.
ejection, where approximately 65%-75% of the stroke volume is ejected. After the blood is ejected, the pressure in the ventricles drops dramatically, but blood continues to flow into the aorta until the end of systole. The end of systole is signaled by the onset of myocardial relaxation and closure of the aortic valve.
TABLE 42.1 INDICATIONS AND CONTRAINDICATIONS FOR IABP USE
▪ FIGURE 42.2 The cardiac cycle. Changes in aortic pressure, left ventricular pressure, left atrial pressure, left ventricular volume, the electrocardiogram (ECG), and heart sounds. (From Porth CM. Pathophysiology Concepts of Altered Health States. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2005, with permission.)
patient’s electrocardiogram, a pacemaker, a set rate, or the patient’s blood pressure. Key Points:
During diastole, the balloon inflates and augments coronary perfusion.
At the beginning of systole, the balloon deflates and increases cardiac output while decreasing myocardial oxygen consumption.
The balloon is inflated with helium, a gas that can be easily absorbed by the body without damage in the case of balloon rupture.
Electrocardiogram (ECG) leads
Arterial blood pressure waveform monitoring
Balloon volume monitoring
Electric console to adjust triggering and inflation timing of the balloon
Battery backup power
TABLE 42.2 PLACEMENT OF AN IABP