Page 113 - Critical Care Nursing Demystified

98 CRITICAL CARE NURSING DeMYSTIFIED

and mitral valve stenosis, mitral valve prolapse and regurgitation, aortic insuf-
ficiency, atrial septal defects, and pericardial effusions. Currently, there are three
types of echocardiographic methods in use: (1) the M-mode, which is a single,
vertical ultrasound beam that produces cardiac views of chamber size and wall
thickness, as well as valve functioning; (2) the 2-D or 2-dimensional mode,
which is a planar ultrasound beam that provides a wider view of the heart and
its structures; (3) the Doppler method, which is used to demonstrate blood
flow through the heart, intracardiac pressures, ejection fraction, and cardiac
output.

TEE—Transesophageal Echocardiography
This study combines ultrasound with endoscopy. A transducer, or echoscope,
is attached to a flexible tube similar to a gastroscope. This tube is advanced
(under local anesthesia) into the esophagus where high-quality images of intrac-
ardiac structures and the thoracic aorta are produced. The interference of the
chest wall, bones, and air-filled lungs is eliminated. The atrial chambers are well
visualized, making it easier to detect left atrial thrombi. It is also useful in
detecting suspected dissecting aortic aneurysms. TEE is a convenient way to
monitor cardiac function during open-heart surgery because the transesopha- Downloaded by [ Faculty of Nursing, Chiangmai University 5.62.158.117] at [07/18/16]. Copyright © McGraw-Hill Global Education Holdings, LLC. Not to be redistributed or modified in any way without permission.
geal probe can be inserted and left to remain in position during surgery. TEE is
particularly useful in situations where COPD, obesity, and chest wall changes
due to aging create obstacles to clear image visualization.

Stress Tests
Stress tests are considered to be noninvasive and are performed to determine
cardiovascular disease as well as the patient’s functional ability in performing
activities of daily living (ADLs). The test is also known as exercise electrocar-
diography, and for those individuals who can tolerate exercise, the test involves
pedaling a stationary bike or walking on a treadmill while connected to an EKG
machine.
Physical stress is placed on the heart and oxygen demands to the heart are
increased. Any physical symptoms that develop are observed. Inadequate car-
diac perfusion is also noted via a camera scanner or the EKG machine.
Some sources indicate that results of exercise testing are more effective
when combined with radionuclide scanning, such as the intravenous injec-
tion of thallium. When thallium is used, it is measured for its rate of absorp-
tion by the heart muscle. Poorly perfused areas of the heart either do not
absorb the thallium or do so much more slowly than the better-perfused
areas of the heart.