Summary
The human heart consists of four chambers: The left side and the
right side each have one atrium and one ventricle. Each of the upper
chambers, the right atrium (plural = atria) and the left atrium, acts as a
receiving chamber and contracts to push blood into the lower chambers,
the right ventricle and the left ventricle. The ventricles serve as the
primary pumping chambers of the heart, propelling blood to the lungs or
to the rest of the body .
There are two distinct but linked circuits in the human circulation
called the pulmonary and systemic circuits. Although both circuits
transport blood and everything it carries, we can initially view the
circuits from the point of view of gases. The pulmonary
circuit transports blood to and from the lungs, where it picks up oxygen
and delivers carbon dioxide for exhalation. The systemic
circuit transports oxygenated blood to virtually all of the tissues of the
body and returns relatively deoxygenated blood and carbon dioxide to
the heart to be sent back to the pulmonary circulation.
The autorhythmicity inherent in cardiac cells keeps the heart beating
at a regular pace; however, the heart is regulated by and responds to
outside influences as well. Neural and endocrine controls are vital to the
regulation of cardiac function. In addition, the heart is sensitive to several
environmental factors, including electrolytes.
All patients scheduled to undergo noncardiac surgery should have an
assessment of the risk of a cardiovascular perioperative cardiac event.
The patient functional status is an important determinant of risk.
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Summary
Identification of risk factors is derived from the history and physical
examination; the type of proposed surgery influences the risk of
perioperative cardiac event.
We use either the revised cardiac risk index (RCRI), also referred to
as the Lee index, or the American College of Surgeons National Surgical
Quality Improvement Program (NSQIP) risk prediction rule to establish
the patient’s risk.
The ACC/AHA guidelines has relied on functional capacity, clinical
characteristics of the patient, prescence of active cardiac condition and
the extent of the surgical procedure. After preoperative evaluation, the
physician should determine the clinical predictors as major, intermediate,
or minor.
We obtain an electrocardiogram (ECG) in patients with cardiac
disease (except in those undergoing low-risk surgery) in large part to
have a baseline available should a postoperative test be abnormal.
For patients with known or suspected heart disease (ie,
cardiovascular disease, significant valvular heart disease, symptomatic
arrhythmias), we only perform further cardiac evaluation
(echocardiography, stress testing, or 24-hour ambulatory monitoring) if it
is indicated in the absence of proposed surgery.
For the most part, chronic cardiovascular medications, such as
aspirin, ACE inhibitors, ARBs, and β-blockers, should be continued, but
the decision should be individualized to each patient’s circumstances.
Ideally, P2Y12 inhibitors should be held before surgery, aside from cases
of recent coronary stenting, where expert opinion should be sought.
Finally, there are no compelling data indicating that starting new
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Summary
cardiovascular medications before surgery can decrease perioperative
risk, although there may be a role for perioperative β-blockade in specific
circumstances.
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