C h a p t e r 1 9
Disorders of Cardiac Function
451
longer interval can salvage some ischemic myocardial
cells. Reestablishing blood flow may also prevent the
microvascular injury that occurs over a longer period.
Even though much of the viable myocardium existing
at the time reperfusion recovers, critical abnormalities
in biochemical function may persist, and these changes
can lead to chronic impairment of ventricular function.
The recovering area of the heart is often referred to as
a
stunned myocardium.
Because myocardial function is
lost before cell death occurs, a stunned myocardium may
not be capable of sustaining life, and persons with large
areas of dysfunctional myocardiummay require support-
ive care until the stunned regions regain their function.
6
The onset of STEMI involves abrupt and significant
chest pain. The pain typically is severe, often described as
being constricting, suffocating, and crushing. Substernal
pain that radiates to the left arm, neck, or jaw is common,
although it may be experienced in other areas of the chest
and back. Unlike that of angina, the pain associated with
MI is more prolonged and not relieved by rest or nitro-
glycerin; this pain frequently requires morphine for relief.
Some persons may not describe it as “pain,” but as “dis-
comfort.” Women may experience atypical ischemic-type
chest pain, whereas the elderly may complain of shortness
of breath more frequently than chest pain.
17
Complaints
of fatigue and weakness, especially of the arms and legs,
are common. Pain and elevated sympathetic activity
invoke tachycardia, anxiety, and restlessness, as well as
emotional responses (e.g., a feeling of impending doom).
Impairment of myocardial function may lead to hypoten-
sion and shock. In addition, gastrointestinal complaints
are common with acute MI. There may be a sensation of
epigastric distress; nausea and vomiting may occur. These
symptoms are thought to be related to the severity of the
FIGURE 19-5.
Acute myocardial infarct. A cross-section
of the ventricles of a man who died a few days after the
onset of severe chest pain shows a transmural infarct in the
posterior and septal regions of the left ventricle.The necrotic
myocardium is soft, yellowish, and sharply demarcated. (From
Rubin E, Farber JL. Rubin’s Pathology: Clinicopathologic
Foundations of Medicine. 3rd ed. Philadelphia, PA: Lippincott
Williams &Wilkins; 1999:558.)
Left circumflex artery
Right coronary artery
Right coronary artery
obstruction
Left anterior descending
coronary artery obstruction
Left circumflex coronary
artery obstruction
Left anterior descending
artery
A
B
C
LV
RV
LV
RV
LV
RV
FIGURE 19-4.
Areas of the heart
affected by occlusion of the
(A)
right coronary artery,
(B)
left
anterior descending coronary
artery, and
(C)
left circumflex
coronary artery. LV, left ventricle;
RV, right ventricle.
