Lipp Vis Nursing ChaptLWBK1630_C02_p013-068

Chapter 2 • Cardiovascular Care  65

Timing IABP Counterpulsation Arterial pressure (mm Hg) U N A S S I S T E D

Non-IABP Percutaneous Mechanical Circulatory Assist Devices • These devices have differing names: percutaneous ventricular assist devices (VADs), percutaneous ventricular support devices, percutaneous mechanical circulatory assist devices, percutaneous mechanical circulatory support devices, and percutaneous VADs. • Left ventricle to aorta assist devices—The Impella System • Left atrial to aorta assist devices—The Tandem Heart

A S S I S T E D ( W I T H I A B P )

100

HANDS ON

90

80

70

60

KEY:

50

Peak systolic pressure Dicrotic notch Peak diastolic pressure End-diastolic pressure

• IABP counterpulsation is synchronized with either the ECG or the arterial waveform. Ideally, balloon inflation should begin when the aortic valve closes—at the dicrotic notch on the arterial waveform. Deflation should occur just before diastole. • Timing of the counterpulsation

forcing it closed, whereas late inflation permits most of the blood

emerging from the ventricle to flow past the balloon, reducing the pump’s effectiveness. • Late deflation may cause cardiac arrest because it increases the resistance to left ventricle pumping. IABP counterpulsation boosts peak diastolic pressure and lowers peak systolic and end- diastolic pressures.

is crucial. Early inflation can damage the aortic valve by

Left VAD

Ventricular Assist Device A VAD is an implantable device that consists of a blood pump, cannulas, and a pneumatic or electrical drive console. The pump is synchronized to the patient’s ECG and functions as the heart’s ventricle. It decreases the heart’s workload while increasing cardiac output. Pump Options VADs are available as continuous flow or pulsatile pumps. A continuous flow pump fills continuously and returns blood to the aorta at a constant rate. A pulsatile pump may work in one of two ways: • It may fill during systole and pump blood into the aorta during diastole.

A completely implanted left VAD is shown here.

Shoulder strap

Aorta

Left ventricle

Diaphragm

External battery pack

Blood pump

Access device