752
JACC Vol. 17, No.3
March 1, 1991:752-7
Treatment of Recurrent Ischemia After Thrombolysis and Successful
Reperfusion for Acute Myocardial Infarction: Effect on In-Hospital
Mortality and Left Ventricular Function
STEPHEN G. ELLIS, MD, FACC, DARRELL DEBOWEY, BS, ERIC R. BATES, MD, FACC,
ERIC J. TOPOL, MD, F ACC
Ann Arbor, Michigan
=
To determine the effect of treatment of recurrent ischemia after
reperfusion for acute myocardial infarction on in-hospital mortality and left ventricular function recovery and to identify patients
at highest risk of serious consequences in the event of recurrent
ischemia in this setting, 405 consecutively treated patients were
studied retrospectively. All patients received intravenous thrombolytic therapy within 6 h of ST segment elevation-documented
infarction and had angiographic confirmation of their reperfusion
status performed within 120 min of treatment.
Three hundred three patients had successful reperfusion with
or without rescue angioplasty and had no recurrent ischemia
(group 1), 74 patients had initially successful reperfusion but
subsequent recurrent ischemia (group 2) and 28 patients had
failed reperfusion (group 3). The in-hospital mortality in groups 1
to 3 was 2.0%, 14.9% and 32.1 %, respectively (p < 0.001) and
the change from baseline to prehospital discharge left ventricular
ejection fraction was 1.2 ± 9.3%, -0.8 ± 8.7% and -4.3 ±
5.3%, respectively (p NS). Within the recurrent ischemia group
(group 2), multiple regression analysis found absence of cardiogenic shock at presentation (p 0.002) and successful treatment
initiated within 90 min of recurrent ischemia (p 0.045) to be the
only variables independently correlated with in-hospital survival.
Later successful reperfusion was not associated with improved
hospital survival. The timing and success of treatment did not
affect recovery of global or regional left ventricular function in the
patients with paired angiographic studies.
Thus, 1) recurrent ischemia after successful reperfusion for
acute myocardial infarction was associated with decreased inhospital survival, 2) successful early treatment of ischemia in this
setting was associated with improved survival compared with later
successful treatment or unsuccessful treatment at any time, and 3)
mortality risk with recurrent ischemia was not easily stratified
with readily available clinical variables.
(J Am Coll CardioI1991;17:752-7)
Treatment of acute myocardial infarction with intravenous
thrombolytic therapy has clearly been demonstrated to improve patient survival (1-4) and, to a lesser but significant
extent, to improve left ventricular functional recovery (5-8).
However, recurrent in-hospital ischemia develops in 5% to
18% of patients depending on the definition and perhaps on
the thrombolytic regimen utilized (9-11) and has been associated with worsened in-hospital survival (12,13). The effect
of the success and timing of treatment of recurrent ischemia
and the patients at highest risk for adverse outcomes with
recurrent ischemia have not been identified. Better understanding of the outcome of treatment of recurrent ischemia
might allow optimal management and decision concerning
interhospital transfer of patients who have been treated with
thrombolytic therapy for acute myocardial infarction.
Methods
From the Division of Cardiology, Department of Internal Medicine,
University of Michigan Medical Center, Ann Arbor, Michigan.
Manuscript received May 8, 1990; revised manuscript received July 25,
1990, accepted August 22, 1990.
Address for reprints: Stephen Ellis, MD, University of Michigan Medical
Center, Department of Internal Medicine. Division of Cardiology. BI F245,
Ann Arbor, Michigan 48109-0022.
© 1991
by the American College of Cardiology
=
=
Study patients. From January 5, 1984 through January
12, 1990, 822 patients were treated for acute myocardial
infarction with intravenous thrombolytic or mechanical
reperfusion therapy and had urgent angiographic definition
of their coronary anatomy at the University of Michigan. All
patients had given informed consent for the procedure based
on guidelines provided by the University of Michigan Medical School Committee to Review Investigation Involving
Human Beings. Data on these patients have been prospectively coded on standard case report forms and entered into
the University of Michigan Interventional Cardiology Databank.
For the purpose of this study, all patients meeting the
following criteria were identified: 1) presentation with ST
segment elevation 2:2 mm in two or more contiguous precordial electrocardiographic (ECG) leads or 2: 1 mm in two
or more contiguous limb leads, 2) treatment with intravenous
thrombolytic therapy within 6 h of clinical presentation and
3) angiographic evaluation of coronary artery patency within
120 min of the initiation of thrombolytic therapy. Supple0735-1097/91/$3.50
lACC Vol. 17, No.3
March 1, 1991:752-7
ELLIS ET AL.
TREATMENT OF POST-THROMBOLYTIC RECURRENT ISCHEMIA
mental use of coronary angioplasty was allowed but not
required.
Four hundred five patients fulfilled these criteria; 309 of
these patients were treated in one of the Thrombolysis and
Angioplasty in Myocardial Infarction (TAM!) trials, the
entry requirements and treatment protocols of which have
been previously published (14). After initial treatment patients routinely received aspirin, 80 to 325 mg daily, and a
calcium channel antagonist throughout their hospital stay
and they received intravenous heparin adjusted to maintain
the partial thromboplastin time one and one-half to two times
the control level for at least 24 h. Pre hospital discharge
angiography was routinely encouraged during the study
period.
Triage to treatment of recurrent ischemia. Patients routinely underwent continuous ECG monitoring for 2:.72 h after
presentation. Clinical suspicion of recurrent ischemia
prompted immediate evaluation by a 12 lead ECG. Treatment thereafter was individualized, largely on the basis of
knowledge of the patient's presenting coronary anatomy as
well as on the patient's hemodynamic status. Initial treatment for almost all patients included sublingual and intravenous nitrate therapy. Throughout the study period coronary
angioplasty was considered the mainstay of treatment for
recurrent ischemia except in patients who responded readily
to nitrates, patients who were considered to be unsuitable
for the procedure because they had multivessel coronary
involvement or were more likely to benefit from bypass
surgery or those whose infarct-related artery was small and
its reocclusion was believed unlikely to have major consequences.
Angiographic analysis. Angiographic analyses were performed by experienced observers who were unaware of
clinical data. The Thrombolysis in Myocardial Infarction
(TIMI) flow pattern was determined visually (15). Pre- and
postintervention percent diameter stenosis of the infarctrelated artery was determined by calipers. Global left ventricular ejection fraction was determined from right anterior
oblique angiograms with use of the area-length method (16).
Regional wall motion in the infarct zone was determined
with the centerline chord method (17). Ventriculograms
were excluded from analysis for inadequate opacification
and when no sinus beats were recorded within the first seven
beats after injection of contrast medium.
Definitions. Initially successful reperfusion was defined
as TIMI flow 2:.2 (15) at initial angiography after the administration of intravenous thrombolytic therapy with or without rescue angioplasty. Multivessel disease was defined as
2:.50% diameter stenosis present in 2:. two of three major
epicardial coronary vessels or a bypassable branch thereof.
Recovery of global and regional left ventricular ejection
fraction was defined as the improvement between the initial
and prehospital discharge ventriculogram-derived left ventricular ejection fraction and infarct zone regional wall
motion.
Recurrent ischemia was defined as the presence of at
753
least two of the three following clinical variables: angina, ST
segment changes consistent with new ischemia or reelevation of serum creatine kinase levels with isoenzyme
confirmation. Clinically silent reocclusion documented only
at follow-up angiography was not included in this definition.
Successful treatment of recurrent ischemia was defined as
the elimination of angina and ST segment changes suggestive
of ischemia (clinical patency) and (in patients undergoing
immediate angiography) restoration of TIMI grade 3 flow.
Time to treatment of recurrent ischemia was defined as
the time from recurrent symptom onset to either repeat coronary angiography, placing the patient on cardiopulmonary
bypass before bypass surgery or the initiation of definitive
medical therapy (intravenous thrombolytic therapy, if used
without mechanical reperfusion, or intravenous heparin or
nitroglycerin if neither intravenous thrombolytic therapy nor
mechanical reperfusion was attempted), whichever occurred
latest. This was determined by a careful review of physicians'
and nurses' notes in the medical and catheterization laboratory
record. When possible, this determination was made independent of knowledge of the major clinical end points of this study.
Because the restoration of adequate infarct artery flow with
coronary angioplasty or medical therapy was often initially
intermittent, the time to successful restoration of flow was not
chosen as the index variable.
Time to treatment of recurrent ischemia :::;90 min was
prospectively identified to determine the effect of early
treatment on patient outcome. The time 90 min was chosen
as a reasonable time to initiation of therapy when a patient
had ready access to a cardiac catheterization laboratory.
Statistical analysis. All values are presented as mean
values ± I SD unless otherwise noted. Comparison among
patients with successful initial reperfusion and no recurrent
ischemia (group I), successful initial reperfusion but recurrent ischemia (group 2) and unsuccessful reperfusion (group
3) was made using analysis of variance methods for continuous variables and chi-square analysis for categorical variables. Comparisons between survivors and non survivors
within group 2 were made using the Student t test and
chi-square analysis for continuous and categorical variables,
respectively. MUltiple linear regression analyses were used
within group 2 to determine the independent correlates of
in-hospital survival and the recovery of global and regional
left ventricular function. Given the number of patients and
events studied, it was intended that this be an exploratory
analysis; therefore, standard post-hoc entry into the regression analyses with alpha = 0.15 to enter and alpha = 0.15 to
reject was performed (18). Statistical significance was assumed when the null hypothesis could be rejected with 95%
confidence (two-tailed testing).
When a single patient had more than one ischemic event,
the data were handled as follows: 1) For comparison of
survival and left ventricular functional outcomes the patient
was entered only once if the events were both treated
successfully and the time to treatment was coded as indefinite; if either event was treated unsuccessfully, then only the
754
Table 2. Mortality and Left Ventricular Function
Table 1. Patient Characteristics
Group I
(reperfusion,
no recurrent
ischemia;
n = 303)
Age (yr)
Male gender (%)
Prior myocardial
infarction (%)
Time to thrombolytic
therapy (h)
Anterior myocardial
infarction (%)
Prior angina (%)
Immediate coronary
angioplasty (%)
Tissue-type plasminogen
activator therapy (%)
Streptokinase therapy
(%)
JACC Vol. 17, No.3
March I, 1991 :752-7
ELLIS ET AL.
TREATMENT OF POST-THROMBOLYTIC RECURRENT ISCHEMIA
Other thrombolytic
regimen (%)
Multivessel coronary
disease (%)
Cardiogenic shock (%)
Baseline left ventricular
ejection fraction (%)
Baseline infarct zone
regional wall motion
(SD/chord)
56 ± 10
76.9
11.2
56 ± II
82.7
12.0
60 ± 9
71.4
14.3
3.1 ±
3.3 ± 1.6
3.3 ± 1.9
45.6
39.2
35.0
42.9
58.4
39.7
54.0
35.7
75.0
75.5
82.4
64.2
21.8
13.5
14.3
2.6
4.1
21.5
50.2
60.8
71.4
0.7
51 ± 12
2.7
50 ± 12
3.6
50 ± 14
-2.58 ± 1.02
-2.64 ± 0.95
-2.68 ± 0.55
1.5
Group I
(reperfusion,
no recurrent
ischemia:
n = 303)
Group 2
(reperfusion,
Group 3
recurrent
ischemia; (no reperfusion;
n = 74)
n = 28)
unsuccessfully treated event was analyzed . 2) For assessment of the success of individual therapies all treatment
attempts were analyzed. When coronary bypass surgery was
performed without angiographic follow-up, successful reperfusion was assumed unless a perioperative death occurred,
in which case necropsy data were evaluated, or unless 2:2
new and contiguous Q waves developed in the territory of
the infarct-related artery after bypass surgery.
Results
Baseline patient demographic data (Table 1). There were
no significant differences among groups 1 to 3 with regard to
patient age, infarct location, time to initiation of thrombolytic therapy, presence of multi vessel coronary disease or
initial left ventricular ejection fraction.
In-hospital patient survival and recovery of left ventricular
function (Table 2, Fig. 1). Patients with successful initial
reperfusion and no clinically evident recurrent ischemia
(group 1) had an extremely low mortality (2.0%) and those
without successful reperfusion (group 3) had a very high
mortality (32.1 %). Patients with initially successful reperfusion but subsequent recurrent ischemia (group 2) had an
intermediate mortality (14.9%). No significant differences
were noted among the groups with regard to recovery of left
ventricular function. Recovery tended to be best when
Death (%)
Change in left
ventricular ejection
fraction (%)*
Change in infarct zone
regional wall motion
2.0t
9.3
1.2 ±
0.50 ± 1.02
Group 2
(reperfusion,
recurrent
ischemia;
n = 74)
Group 3
(no reperfusion;
n = 28)
14.9
-0.8 ± 8.7
32.1
-4.3 ± 5.3t
0.47 ± 1.04
-0.18 ± 0.37§
(%)*
'From baseline to prehospital discharge catheterization, n = 208, 30 and
10 for groups I, 2 and 3, respectively; tp < 0.001 versus reperfusion with
recurrent ischemia: tp = 0.12 versus reperfusion with recurrent ischemia;
§p = 0.14 versus reperfusion with recurrent ischemia.
reperfusion was achieved without recurrent ischemia and
recovery was worse when all attempts to achieve reperfusion were unsuccessful.
Restoration of coronary patency with angioplasty. "Retrieval" coronary angioplasty was attempted in 52 patients.
Their mean age was 53 ± 10 years; 86% were male and 56%
had multivessel disease. Their initial left ventricular ejection
fraction was 51 ± 12% and dilation of 52 coronary sites was
attempted (left anterior descending artery in 17, left circumflex artery in 4, right artery in 27 and a bypass graft in 4).
Angioplasty was initiated at a median of 1.5 h after the onset
of recurrent ischemic symptoms (range 0.2 to 12.2 h) and
was successful at restoring patency in 39 (75%) of 52 vessels.
Restoration of coronary patency with medical therapy.
Sixteen patients were treated medically. Clinical coronary
patency was achieved in 2 of the 3 patients treated with
intravenous thrombolytic therapy and 2 of the 13 patients
who were treated without thrombolytic therapy.
Treatment of recurrent ischemia with emergency bypass
surgery. Emergency bypass surgery was performed on 11
patients, including 5 who had undergone clinically unsucFigure I. Incidence of recurrent ischemia and the effect on inhospital mortality of recurrent ischemia in 405 patients.
Initial Reperfusion. wilh
Recurrent Ischemia
.J
(%)
Mortality
~o ~j.L-=====,,"-_.l.---'_.....J..
~ D n
_-3:2-':l-%. .J . .
Sustained
Reperfusion
Recurrent
Ischemia
No
Reperfusion
ELLIS ET AL.
TREATMENT OF POST-THROMBOLYTIC RECURRENT ISCHEMIA
lACC Vol. 17. No . 3
March I, 1991 :752-7
755
Table 3. Correlates of In-Hospital Death After
Recurrent Ischemia
Died
= II)
Survived
(n = 63)
Univariate
P
63 ± 9
36.4
55 ± II
41.3
0.01
NS
115 ± 26
\32 ± 27
0.05
18.2
11.3
NS
IS.2
0.0
0.01
0.0
33.3
63.6
30.0
0.0
9.5
49.2
S5.7
41.3
14.3
NS
NS
NS
NS
NS
IS.2
3.4 ± 2.4
9.5
3.3 ± 1.4
NS
NS
IS.2
12.7
NS
47 ± 15
51 ± 12
NS
90.9
IS .2
55.5
12.7
0.02
NS
18.2
12.7
NS
54.5
53.1
NS
(n
Clinical
Age (yr)
Anterior myocardial
infarction (%)
Arterial blood pressure
(mm Hg)
Bradycardia (:s50 bpm)
before catheterization (%)
Cardiogenic shock at
presentation (%)
Diabetes mellitus (%)
Hypertension (%)
Male gender (%)
Prior angina pectoris (%)
Prior myocardial infarction
(%)
Rales at presentation (%)
Time to intravenous therapy
(h)
Ventricular tachycardia
prior to catheterization
(%)
Angiographic
Initial left ventricular
ejection fraction (%)
Multivessel disease (%)
Proximal LAD occlusion
(%)
Proximal right coronary
occlusion (%)
Treatment
Early coronary angioplasty
(%)*
Time to treatment of
recurrent ischemia
(median, range [h])
Successful reperfusion (%)
Successful reperfusion
initiated within 90 min
3.5 (1.4 to 28) 2.0 (0.2 to lOS)
45.5
0.0
69.S
39.7
NS
NS
0.03
(%)
*For failed thrombolysis or " high'risk " anatomy at initial catheterization:
LAD = left anterior descending coronary artery .
cessful coronary angioplasty. Treatment was initiated a
median of 2.9 h after development of recurrent ischemia.
Univariate and multivariate correlates of in-hospital survival after recurrent ischemia (Table 3, Fig. 2). Survival was
correlated in univariate analysis with the absence of cardiogenic shock at initial presentation, successful treatment
initiated within 90 min of recurrent ischemia, younger patient age and higher blood pressure at initial presentation.
Regression analysis found only shock and time to treatment
to independently predict in-hospital outcome (death = 0.10
+ 0.75 [shock] - 0.16 [successful treatment within 90 min);
multiple r = 0.51, P < 0.01). Successful early (::;90 min)
initiation of therapy was associated with a significantly lower
Mortality
(%)
10
Early
Treatment
Late
Successful
Treatment
Failed
Treatment
Figure 2. Failure of late successful reperfusion to improve inhospital survival after recurrent ischemia in 74 patients.
in-hospital mortality (0 of 25 = 0%) than in patients with
successful later reperfusion (5 of 24 = 21%) or unsuccessful
reperfusion (6 of 25 = 24%) (Fig. 2).
Correlates of left ventricular functional recovery after
recurrent ischemia. Paired left ventricular angiograms of
sufficient quality for analysis were available in only 30 of the
74 group 2 patients. In these patients only the presence of an
anterior myocardial infarction was correlated with improved
recovery of global left ventricular function as measured by
ejection fraction (anterior = 3.7 ± 9.1% versus inferior =
- 3.1 ± 7.0%; p = 0.04). There was a weak and nonstatistically significant trend toward improved recovery of function
when successful reperfusion was achieved (successful reperfusion = 1.1 ± 8.2% versus unsuccessful reperfusion = - 3.8
± 8.8%; p = 0.18). There were no correlates of improved
infarct zone regional ejection fraction, although patients with
single vessel disease tended to have improved recovery
(single vessel = 0.97 ± 1.06 SD/chord versus multivessel =
-0.02 ± 0.10 SD/chord; p = 0.07).
Discussion
The problem of recurrent postinfarction ischemia. The
timely administration of intravenous thrombolytic agents to
patients with acute myocardial infarction has markedly
reduced the in-hospital mortality of selected patient groups
(1-4). However, because none of these agents removes the
underlying stimulus for thrombus formation, a propensity for
recurrent thrombosis and ischemia remains. Recurrent
ischemia occurs in up to 20% of patients in this setting and
has been shown to be associated with an increase in inhospital mortality from approximately 50/0-10% to 100/0-20%
(12, 13). In the mid 1980s several investigations were designed to test the hypothesis that mechanical disruption
(angioplasty) of the underlying atheroma and a reduction in
the consequent "fixed" obstruction would lessen the risk of
recurrent ischemia. The failure of this aggressive strategy to
improve short-term survival or recovery of left ventricular
contractility (19-21) has led to the widespread support of the
approach of watchful waiting (22) , with cardiac catheteriza-
756
ELLIS ET AL.
TREATMENT OF POST-THROMBOL YTIC RECURRENT ISCHEMIA
tion reserved for patients who display postinfarction ischemia. It must be recognized, however, that these results
came from trials in which most of the participating hospital
centers could provide timely and aggressive interventional
therapy to patients with recurrent ischemia.
The consequences of early and successful treatment of
ischemia in this setting and the determination of patients at
highest risk for morbid outcome with recurrent ischemia
have not been adequately studied. The implications of either
a benefit or an inability to demonstrate the benefit of early
aggressive therapy of recurrent ischemia would have considerable ramifications regarding interhospital transfer of these
often acutely ill patients from the community hospitals to
which they are most often admitted.
Animal studies of recurrent ischemia. In animal models
(23) brief periods of ischemia consequent to coronary occlusion may minimize necrosis from a second, temporally
proximate period of ischemia, providing that the duration of
the second occlusion is relatively short. Thus, several 5 min
occlusions have been shown to limit infarct size when a
subsequent 40 min coronary occlusion. but not a 3 h coronary occlusion. is applied (23). This phenomenon is termed
"preconditioning" and appears to affect infarct size but not
to attenuate myocardial stunning (24). The effect of longer
initial periods of coronary occlusion. as might occur in
humans with acute myocardial infarction treated with thrombolytic therapy, on the consequences of a second coronary
occlusion have not been evaluated.
Results of therapy for recurrent ischemia. This study is
the first to report on the effect of treatment of recurrent
ischemia after thrombolytic therapy in a relatively large
number of patients treated for acute myocardial infarction.
Successful early (::;90 min) initiation of therapy for recurrent
ischemia was associated with a significantly lower inhospital mortality (0%) than successful later reperfusion
(21%) or unsuccessful reperfusion (24%). These figures
compare with hospital mortalities of 2% and 32%, respectively, for patients with successful reperfusion and no recurrent ischemia and patients with unsuccessful reperfusion
after initial therapy. The favorable impact of early retreatment on the recovery of left ventricular function in the
relatively limited number of patients with paired ventriculograms was much less pronounced and only a positive trend
was demonstrated.
Mechanisms of improved survival. The mechanism by
which intravenous thrombolytic therapy improves patient
survival is not well understood. It appears that only very
early treatment of myocardial infarction with thrombolytic
therapy markedly improves left ventricular functional recovery (25). The modest improvement in left ventricular ejection
fraction in most patients (5-8) appears disproportionate to
the gain in survival, leading to speculation that changes in
the threshold for malignant ventricular arrhythmias (26),
improved infarct healing (27) or other factors may be contributing beneficial mechanisms. Because of the small improvement in recovery of left ventricular ejection fraction
JACC Vol. 17. No.3
March 1. 1991 :752-7
with successful thrombolysis (5-8), it is not surprising that
successful treatment of recurrent ischemia also appears not
to have a major impact on left ventricular functional recovery. The mechanism of improved survival with early successful treatment of recurrent ischemia then remains somewhat enigmatic, but demonstration of this relation does
provide further support for the prognostic importance of an
open coronary artery after myocardial infarction (28,29). Of
the 11 deaths in this series, 6 were attributed to primary left
ventricular dysfunction and 4 were attributed to multisystem
failure with left ventricular dysfunction as a contributing
factor. Perhaps if the patients who died had been serially
restudied and if their left ventricular functional recovery had
been found to be especially poor, a beneficial effect of
successful secondary reperfusion by means of relative improvement of left ventricular function might have been
demonstrated.
Limitations. The results of this study should be viewed in
the context of its limitations. First. this is a retrospective
study in which a key variable, time to treatment of recurrent
ischemia, was not prospectively recorded. Careful and unbiased chart review usually allowed an accurate assessment
of this variable. but errors of 15 to 20 min due to imprecise
timing of events were probably not uncommon. The inherent
inaccuracies of measuring time from chest pain onset and
time to reperfusion consequent to changing flow patterns
with incomplete coronary obstruction should also be acknowledged. In fact, reanalysis of the data using 60 and
120 min, but not 150 min, cutoff points yielded similar
results. A related compounding problem is that of the bias
toward earlier treatment of the most gravely ill patients (30).
This could have resulted in earlier therapy of those patients
most likely to benefit from successful reperfusion as well as
later treatment of patients with a smaller infarct in whom
therapy might have had no effect on survival.
Also, although a relatively small number of patients had
recurrent ischemia, mUltiple subgroup analyses were performed, leading to the possible identification of spurious
associations. The previously demonstrated marked survival
benefit with very early treatment of myocardial infarction
(1,2) lends credence to the conclusions of this study and
makes an invalid conclusion less likely (31). Finally, compared with current treatment strategies based on the findings
of randomized trials (18-20), a large proportion of patients
analyzed in this study received coronary angioplasty early
for failed thrombolysis or "high risk" anatomy. Although
early angioplasty was not an independent correlate of inhospital survival, it is possible that the inclusion of such
patients might slightly bias the stated results.
Clinical implications. Given the facts that up to 20% of
patients treated with intravenous thrombolytic therapy will
have recurrent ischemia (9-11), that this process appreciably
increases in-hospital mortality (12,13), that patients likely to
have recurrent ischemia and its major consequences are
difficult to identify prospectively (32) and that early treatment of recurrent ischemia appears to improve patient
JACC Vol. 17. No.3
ELLIS ET AL.
TREATMENT OF POST-THROMBOLYTIC RECURRENT ISCHEMIA
March 1. 1991:752-7
survival, it appears that all patients treated with intravenous
thrombolytic therapy should have rapid access to facilities
where secondary reperfusion can be readily obtained. It is
not known whether a second administration of a thrombolytic regimen can match the 75% reperfusion rates with
"retrieval" coronary angioplasty in this setting. Preliminary
reports suggest high initial patency, but also frequent recurrent ischemia, when tissue-type plasminogen activator is
readministered (33). Until sustained efficacy can be demonstrated, we recommend that provisions be made for interhospital transfer to cardiac catheterization facilities within
60 to 120 min of recurrent ischemia for all patients undergoing thrombolytic therapy.
We express our gratitude for the expert secretarial assistance provided by
Kevin Handy and Lin Nicholson.
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