4.
Onset Of STEMI
4.1. Recognition of Symptoms by Patient
Early recognition of symptoms of STEMI by the patient or someone
with the patient is the first step that must occur before evaluation
and life-saving treatment can be obtained. Although many lay persons
are generally aware that chest pain is a presenting symptom of STEMI,
they are unaware of the common associated symptoms, such as arm
pain, lower jaw pain, shortness of breath, and diaphoresis (111)
or anginal equivalents. The average patient with STEMI does not
seek medical care for approximately 2 hours after symptom onset,
and this pattern appears unchanged over the last decade (45,87,112).
Average and median delays for patients with STEMI were 4.7 and 2.3
hours, respectively, from the 14-country Global Registry of Acute
Coronary Events (GRACE) project. Approximately 41% of patients with
STEMI presented to the 94 study hospitals within 2 hours of acute
cardiac ischemia symptom onset (113).
A
baseline analysis from the REACT research program demonstrated longer
delay times among non-Hispanic blacks, older patients, and Medicaid-only
recipients and shorter delay times among Medicare recipients (compared
with privately insured patients) and among patients who came to
the hospital by ambulance (87).
In the majority of studies examined to date, women in both univariate
and multivariate adjusted analyses (in which age and other potentially
confounding variables have been controlled) exhibit more prolonged
delay patterns than men (113).
A
number of studies have provided insight into why patients delay
in seeking early care for heart symptoms (Table
2) (114). Focus groups conducted
for the REACT research program (92,115)
revealed that patients commonly hold
a pre-existing expectation that a heart attack would present dramatically
with severe, crushing chest pain, such that there would be no doubt
that one was occurring. This was in contrast to their actual reported
symptom experience of a gradual onset of discomfort involving midsternal
chest pressure or tightness, with other associated symptoms often
increasing in intensity. The ambiguity of these symptoms, due to
this disconnect between prior expectations and actual experience,
resulted in uncertainty about the origin of symptoms and thus a
“wait-and-see” posture by patients and those around
them (114). Other reported reasons
for delay were that patients thought the symptoms were self-limited
and would go away or were not serious (95,116,117);
that they attributed symptoms to other pre-existing chronic conditions,
especially among the elderly with multiple chronic conditions (e.g.,
arthritis), or sometimes to a common illness such as influenza;
that they were afraid of being embarrassed if symptoms turned out
to be a “false alarm”; that they were reluctant to trouble
others (e.g., providers, EMS) unless they were “really sick”
(95,116,117);
that they held stereotypes of who is at risk for a heart attack;
and that they lacked awareness of the importance of rapid action,
knowledge of reperfusion treatment, or knowledge of the benefits
of calling EMS/9-1-1 to ensure earlier treatment (Table
2) (Figure 5) (51,114).
Notably, women did not perceive themselves to be at risk (53).
4.1.1.
Silent and Unrecognized Events
Patients experiencing STEMI do not always present with chest discomfort
(118). The Framingham Study was
the first to show that as many as half of all MIs may be clinically
silent and unrecognized by the patient (119).
Canto et al. (100)
found that one third of the 434 877 patients with confirmed MI in
the National Registry of Myocardial Infarction (NRMI) (100)
presented to the hospital with symptoms other than chest discomfort.
Compared with MI patients with chest discomfort, MI patients without
chest discomfort were more likely to be older (74.2 versus 66.9
years), women (49.0% versus 38.0%), diabetic (32.6% versus 25.4%),
and/or have prior heart failure (26.4% versus 12.3%). MI patients
without chest discomfort delayed longer before they went to the
hospital (mean 7.9 versus 5.3 hours) and were less likely to be
diagnosed as having an MI when admitted (22.2% versus 50.3%). They
also were less likely to receive fibrinolysis or primary percutaneous
coronary intervention (PCI) (25.3% versus 74.0%), aspirin (60.4%
versus 84.5%), beta-blockers (28.0% versus 48.0%), or heparin (53.4%
versus 83.2%). Silent MI patients were 2.2 times (95% confidence
interval [CI] 2.17 to 2.26) more likely to die during the hospitalization
(in-hospital mortality rate 23.3% versus 9.3%).
Healthcare providers should maintain a high index of suspicion for
MI when evaluating women, diabetics, older patients, and those with
a history of heart failure, as well as those patients complaining
of chest discomfort but who have a permanent pacemaker that may
confound recognition of STEMI on their 12-lead ECG (120).
4.2. Out-of-Hospital Cardiac Arrest
Class I
1. All communities should create and maintain a strong “Chain
of Survival” for out-of-hospital cardiac arrest that includes
early access (recognition of the problem and activation of the EMS
system by a bystander), early CPR, early defibrillation for patients
who need it, and early advanced cardiac life support (ACLS). (Level
of Evidence: C)
2. Family members of patients experiencing STEMI should be advised
to take CPR training and familiarize themselves with the use of
an automated external defibrillator (AED). In addition, they should
be referred to a CPR training program that has a social support
component for family members of post- STEMI patients. (Level
of Evidence: B)
The majority of deaths from STEMI occur within the first 1 to 2
hours after symptom onset, usually from ventricular fibrillation
(VF). Survival from VF is inversely related to the time interval
between its onset and termination. For each minute that a patient
remains in VF, the odds of survival decrease by 7% to 10% (121).
Survival is optimal when both CPR and ACLS, including defibrillation
and drug therapy, are provided early.
The AHA has introduced the “chain of survival” concept
to represent a sequence of events that ideally should occur to maximize
the odds of successful resuscitation from cardiac arrest (121).
The links in the chain include early access (recognition of the
problem and activation of the EMS system
by a bystander), early CPR, early defibrillation for patients who
need it, and early ACLS.
Although
estimates of overall survival from out-of-hospital cardiac arrest
in the United States are as low as 5%, survival in patients who
are in VF initially can be much higher. The percentage of patients
who are found in VF and the likelihood of survival are higher if
the patient’s collapse is witnessed, bystander CPR is performed,
and a monitor/defibrillator can be applied quickly. For example,
27% of patients with witnessed out-of-hospital cardiac arrest in
Seattle, WA, survived to leave the hospital when bystanders performed
CPR (122). Only 13% survived without
bystander CPR.
Emerging data suggest that treatment of VF with immediate defibrillation,
irrespective of “down time,” may not be optimal for
all patients and that as the duration of cardiac arrest increases,
different interventions may take priority over defibrillation, such
as a period of chest compressions (with associated tissue oxygen
delivery) after 3 minutes of VF before defibrillation (123).
There is often a long delay from the recognition of cardiac arrest
to defibrillation in rural areas where travel time is long and in
densely populated urban areas. Survival rates are often extremely
low in such settings (124-126).
In Seattle,WA, the majority of out-of-hospital cardiac arrest victims
receive defibrillation within 5 to 7 minutes after the recognition
of out-of-hospital cardiac arrest. In Rochester, MN, the addition
of a police defibrillation program to conventional EMS services
resulted in a median time to first shock of 5.9 minutes for patients
in VF and a 49% rate of survival to discharge (127).
Total cumulative survival experience at 7 years in this community
was 40% (128). Outcomes data on
all Rochester, MN, patients who had an out-of-hospital cardiac arrest
with VF from 1990 to 2000 who received defibrillation from emergency
personnel showed that 72% survived to hospital admission and 40%
were neurologically intact at discharge, with a mean follow-up of
4.8 years (129).
The key to improved survival appears to be the availability of early
defibrillation. In the Ontario Pre-hospital Advanced Life Support
(OPALS) study, which involved 19 suburban and urban communities,
improving the proportion of out-ofhospital cardiac arrest patients
who were reached by a defibrillation-equipped ambulance within 8
minutes from 77% to 93% increased survival to hospital discharge
from 3.9% to 5.2% (130). A 2-year
prospective study at 3 Chicago, IL, airports of readily accessible
AEDs in well-marked areas of the airport reported successful resuscitation
in 11 of 18 patients with VF. Ten of the 18 were alive and neurologically
intact at 1 year of follow-up (131).
Family members of patients with STEMI should be referred to a CPR
program that combines CPR training with social support (132,133)
(see Section 7.12.1). One study of the impact of in-home defibrillators
on post-MI patients and their significant others reported that AEDs
were valued by the participants and increased their perception of
control over their heart disease, notably for those who believed
their risk of cardiac arrest to be high (134).
Research is under way to test the safety and effectiveness of home
use of AEDs by family members of patients after MI (135).
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