Page 347 - Cardiac Nursing

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C HAPTER 1 5 / Electrocardiography 323
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V V V V V V V V
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V33
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6 6 6 6
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VF
VF
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V V V V V V V V V V V
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VF
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B
■ Figure 15-34 (A) NSTEMI. Note widespread ST depression in leads I, II, III, aVF, and V 2–6 . The ST seg-
V
ment elevation in aVR and V 1 along with ischemic changes in all other leads is suggestive of left main or sig-
nificant triple vessel coronary artery disease. This patient’s troponin and CK-MB were elevated, leading to the
diagnosis of NSTEMI. (B) NSTEMI. There is T-wave inversion in several leads, especially deep in V 3 –V 5 , but
no significant Q waves in any lead. Cardiac biomarkers were elevated.
to both pressure and volume overload by dilating, whereas the regurgitation, systemic hypertension, and left heart failure. Left
thicker-walled ventricles tend to dilate with volume overload and atrial enlargement can be manifested on the ECG in the follow-
hypertrophy (increase wall thickness) with pressure overload. 6 ing ways (Fig. 15-36):
1. The P wave is wider than 0.12 second and often notched in leads
V
Atrial Enlargement I, II, aVL, and V 4–6 (termed P mitrale). The interval between thee
notches is 0.04 second, and the P wave may encroach into the
Atrial enlargement is reflected on the ECG as changes in P wave PR segment, making the PR segment appear shorter than normal.
size and morphology. Normal P waves are no wider than 0.11 sec- 2. Increased width and depth of the terminal negative component
ond or taller than 2.5 mm. They are usually upright in leads I, II, of the P wave in lead V 1 or V 2 .
V
and V 4–6 and diphasic with the initial portion upright and the ter- 3.Leftward shift of P wave axis to between 30 and
45 degrees.
V
minal portion negative in V 1 . Right atrial depolarization forms
the first half of the P wave, and left atrial depolarization forms the Right Atrial Enlargement
second half (Fig. 15-35). Atrial enlargement usually accompanies Right atrial enlargement is commonly caused by conditions that
ventricular enlargement, so the presence of ECG signs of atrial en- increase the work of the right atrium, such as pulmonary hyper-
largement is suggestive of ventricular enlargement as well. tension, pulmonary or tricuspid stenosis or regurgitation, and
congenital heart disease. Right atrial enlargement can be mani-
fested on the ECG in the following ways (see Fig. 15-36):
Left Atrial Enlargement
Left atrial enlargement is caused by conditions that increase pres- 1. The P waves are tall and peaked ( 2.5 mm) in leads II, III, and
e
e
sure or volume in the left atrium, such as mitral stenosis, mitral aVF (termed P pulmonale).