(Circulation. 1995;92:1110-1116.)
© 1995 American Heart Association, Inc.
Articles |
From the Thoraxcenter, Erasmus University, Rotterdam, the Netherlands (T.L., M.L.S., G.A.V.), University of Leuven (Belgium) (F.V., M.V.), and Medisch Centrum Alkmaar, Netherlands.
Correspondence to Maarten L. Simoons, MD, Thoraxcenter, BD 434, Erasmus University, PO Box 1738, 3000 DR Rotterdam, The Netherlands.
| Abstract |
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Methods and Results Five-year follow-up information on mortality was collected. Hospital mortality was lower after rTPA than placebo (2.5% versus 5.7%, P=.04) and higher after rTPA with immediate PTCA compared with rTPA without additional intervention (6.0% versus 2.2%, P=.07). Of the 1043 hospital survivors, data were available for 923 patients, of whom 109 died. In the placebo group, mortality after hospital discharge was 10.7% versus 11.0% in the comparative rTPA group. The patients treated with rTPA and immediate PTCA had a mortality rate of 10.5% versus 8.9% in the rTPA group without PTCA (all P=NS). Significant determinants of mortality in multivariate proportional hazards analysis were enzymatic infarct size, indicators of residual left ventricular function, number of diseased vessels and TIMI perfusion grade at discharge. Patients with TIMI grade 2 flow had mortality rates similar to those with TIMI flow grades 0 and 1, while prognosis was better in patients with TIMI flow grade 3.
Conclusions The initial in-hospital benefit of thrombolysis with intravenous rTPA is maintained throughout 5 years, with no early or late beneficial effect of systematic immediate PTCA. Enzymatic infarct size, left ventricular function, and extent of coronary artery disease are predictors for long-term survival. TIMI perfusion grade 2 at discharge should be considered as an inadequate result of therapy.
Key Words: thrombolysis infarction angioplasty
| Introduction |
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To assess which factors are associated with improved long-term survival after thrombolytic therapy with recombinant tissue plasminogen activator (rTPA), 5-year follow-up data were collected in 1043 hospital survivors of two studies performed by the European Cooperative Study Group.5 14 The following questions were addressed. Is the improved 1-year survival after thrombolytic therapy with rTPA sustained or increased at 5-year follow-up? Is there a late benefit for patients who underwent systematic immediate percutaneous transluminal coronary angioplasty (PTCA), even though such intervention did not result in any benefit at hospital discharge or at 1 or 2 years of follow-up?9 10 14 15 16 Which parameters available at hospital discharge predict 5-year survival, and are these the same as those factors predicting 1-year survival?
| Methods |
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Clinical data were collected and blood samples were drawn for
calculation of infarct size based on
hydroxy butyrate
dehydrogenase.17 Exercise testing, radionuclide
ventriculography, coronary angiography, and left
ventriculography were performed before hospital discharge. Before
beginning the trial, each clinic participating in the study was
assigned a specific time window for the performance of these
examinations: 10 to 14, 12 to 16, 14 to 18, 16 to 20, or 18 to 22 days
after allocation. ß-Adrenergic blocking agents were to be prescribed
unless contraindications were present. ECGs, infarct size,
ventriculograms, and angiograms were centrally assessed.
There were 45 in-hospital deaths: 21, 9, 4, and 11 in the placebo, rTPA, rTPA without PTCA, and rTPA with PTCA treatment arms, respectively. Survival status was collected from all 1043 patients who were discharged alive (691 patients in the rTPA/placebo trial and 352 in the rTPA/PTCA trial). Follow-up was obtained from the treating physician, municipal registries, or the patient.
Data Analysis
Survival curves for the different treatment
groups and other
variables were obtained as described by Kaplan and Meier.
Variables were classified in four different groups. Group 1,
clinical variables, were age; sex; sum of ST elevation at the
J-point on different times during hospital stay; time from symptom
onset to treatment allocation; previous myocardial infarction; site of
infarction; Killip class at admission; angina at rest and during
effort; clinical signs of heart failure, atrial fibrillation, or
pericarditis; and use of ß-blockers, digitalis,
diuretics, or a combination of the latter two between 24 hours
and hospital discharge. A new variable was defined
representing several clinical indices of impaired left
ventricular function when the patient experienced one of
the following: a period of systolic blood pressure below 90 mm Hg or
cardiogenic shock between 24 hours and hospital discharge, New York
Heart Association class III or IV at discharge, use of
diuretics and/or digitalis, and not giving ß-blockade to
the patient. Patients in whom an exercise test was not performed on
clinical grounds were also included in this variable. Group 2
variable was infarct size, as assessed from cardiac enzyme
release.17 Group 3 variables included exercise test
results; systolic blood pressure rise from baseline to peak exercise;
maximum heart rate during exercise; occurrence of angina; ST segment
depression and elevation during exercise; and maximum workload and
percentage of predicted workload achieved according to age and
height. Group 4 variables included left ventricular
ejection fraction from radionuclide ventriculography and variables
obtained from coronary angiography and left ventriculography:
TIMI perfusion grade of the infarct related vessel, extent, and
severity of coronary artery disease, and
end-diastolic and end-systolic volumes. In the
studies, left ventricular ejection fraction was measured
both by radionuclide ventriculography and by contrast angiography. The
former measurement was used in the analysis because this was
obtained in a larger group of patients.
For all variables mentioned
above, a univariate
"crude" relative risk was calculated using data from those
patients of whom survival status at 5 years was known. For continuous
variables, patients were categorized into three subgroups of
approximately equal size or dichotomized in clinically accepted groups,
as indicated in Table 3
. Subsequently, mortality was assessed
in each
subgroup. The category with the lowest expected risk was chosen as the
reference group.
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To obtain independent predictors for mortality, the Cox proportional hazards model was applied, which provides a conditional probability of death for every patient at each moment during follow-up, given a certain combination of risk factors.18 In a stepwise procedure, variables were included in the models if the probability for inclusion was less than .10. A variable was removed if the associated probability exceeded .15. Clinical data, data of the exercise test, radionuclide angiography, and angiographic data were first analyzed in clusters; those retained in the various steps were combined in the final models. The 95% confidence interval for relative risk was derived from the natural antilogarithm of the coefficient ±1.96 times the standard error.
Multivariate analysis was used to develop a composite risk score based on patient characteristics related to 5-year mortality in the univariate analysis. Relative risk estimates were obtained with Cox multivariate regression analysis. Five risk functions were designed in which clinical (subjective) parameters were compared with or combined with objective parameters obtained at hospital discharge. One model consisted of clinical data only (model I). The next model consisted of clinical data combined with enzymatic infarct size (model II), and in the third model, exercise test results were added (model III). All parameters were combined in the last model (model IV). Treatment was forced into all the models. For each model, risk estimates were calculated for each patient and compared with the observed risk.
| Results |
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Complete 5-year mortality information could be obtained for 923
patients (Table 1
). Median follow-up since discharge
was 5.5 years, ranging from 1 day to 7.5 years. The 120 patients with
incomplete follow-up (11.5%) were randomly distributed over the
two studies and the four treatment groups.
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Hospital mortality was 2.5% for alteplase versus 5.7% for patients
receiving placebo and also 6.0% for patients allocated to additional
immediate PTCA (Table 1
). At 1 year and 5 years, this
difference
remained essentially unchanged (Fig 1
). Five-year
survival was similar in the two rTPAonly groups and better than
either the placebo or rTPAplusPTCA group
(P=.06).
Five-year survival of patients discharged alive was 89%. Survival
after discharge was similar in each treatment group, averaging 2.1%
per year. At 5 years, as at 1 year, there was no additional beneficial
effect for immediate PTCA.
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Predictors for increased 5-year mortality risk after discharge
angiography as obtained by univariate analysis
(Table 2
) were aged greater than 60 years;
parameters representing residual left
ventricular function: infarct size, remaining ST elevation
at 6 hours, an increase of systolic blood pressure during exercise less
than 30 mm Hg or inability to perform an exercise test, an ejection
fraction below 40%, and the clinical index of impaired left
ventricular function; as well as parameters
representing the extent of coronary disease: a
history of angina for more than 4 weeks, previous myocardial
infarction, more than two diseased vessels, and a reduced perfusion
(TIMI grade less than 3) of the infarct related artery. The relative
mortality risk for incomplete perfusion (TIMI grade 2) was similar to
that of TIMI grades 0 and 1, while this risk was reduced in patients
with complete TIMI grade 3, flow (Fig 2
). Not
significant, among others, were treatment strategy, infarct location,
and sex. As an example of the interaction between various
parameters, Fig 3
shows survival curves for
patients subdivided on ejection fraction and the extent of
coronary disease.
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In Table 3
, we present the relative risk of each risk factor
conditional on the other factors in the four risk functions as
obtained by multivariate analysis. In the
risk function with clinical data, only four parameters were
retained (in order of decreasing importance): the clinical index of the
impaired left ventricular function, history of previous
infarction, ST elevation of 2 mV or more at 6 hours, and age greater
than or equal to 60 years. In addition to the clinical
parameters, infarct size contributed strongly to the
prediction of mortality at 5 years (model II). However, systolic blood
pressure rise of less than 30 mm Hg during exercise testing did not
contribute independently to mortality prediction (model III).
In the final model (model IV), parameters representing left ventricular function and coronary anatomy were retained. A large infarct size and clinical findings related to an impaired ventricular function between 24 hours and discharge were associated with, respectively, 2.3- and 1.7-fold increases in mortality. Multivessel disease and TIMI perfusion grade below 3 also contributed to the risk (1.7- and 1.6-fold increases in mortality risk, respectively).
The information content of the models was compared by use of receiver operator characteristic (ROC) curves.19 The areas under the ROC curves were almost equal in size. This implies that the predictive accuracy of the different models is similar. Thus simple clinical data suffice for long-term risk assessment after myocardial infarction.
| Discussion |
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Indicators for increased mortality risk during 5 years after hospital discharge can be grouped as parameters representing infarct size or residual left ventricular function (enzymatic infarct size, the amount of ST elevation, the clinical index of impaired left ventricular function, blood pressure increase during exercise, and left ventricular ejection fraction) and parameters representing the extent of coronary disease (history of angina, previous infarction, TIMI perfusion grade, and multivessel disease). The indicators that were retained in the multivariate analysis were all interchangeable and appeared or disappeared in the model, depending on which variables were entered to represent left ventricular function or extent of coronary disease. In particular, the strongest predictor of long-term mortality risk in the final analysis, enzymatic infarct size, might be replaced by left ventricular ejection fraction without loss of accuracy in the prediction, the latter being the consequence of a large area of nonfunctioning myocardium after extensive myocardial damage.
Limitations of the Analysis
It should be appreciated that
data from two studies were combined
in this analysis.5 14 These studies were designed
and conducted in parallel, with similar data collection methods. The
actual treatment strategies did not contribute to the prediction of
postdischarge mortality (Table 3
), and similar results
were obtained when the trials were analyzed separately, albeit
with loss of statistical power.
Follow-up was less than 5 years in 120
patients, equally divided
among the trials and patient groups (Table 1
). Still, 1-year
follow-up was complete in 99%. Thus, it is unlikely that the
results are biased by incomplete follow-up.
In all clinical trials,
actual treatment may vary, depending on the
physician's preference. At 1 year, 25.5% of the patients in the
noninvasive arm of the rTPA/PTCA trial had undergone PTCA or bypass
surgery versus 15.6% to 18.5% in the three other
groups.9 A separate analysis was performed using
actual treatment within 14 days after hospital admission. The results
were very similar to the intention-to-treat analysis as
presented in this report. Despite the higher intervention rate
in patients allocated to rTPA in the rTPA/PTCA trial, 5-year survival
was similar between the two rTPA groups (Fig 1
). Thus, it is
unlikely
that the results have been influenced by subsequent unrecorded
interventions after the first year.
Importance of Complete Coronary Perfusion for
Short-term and Long-term Follow-up
It was remarkable, as demonstrated
in Fig 2
, that long-term
prognosis for patients with incomplete perfusion, TIMI grade 2,
appeared to be similar to patients with occluded (TIMI flow grades 0 or
1) vessels, while prognosis was superior in patients with complete,
TIMI grade 3 flow. These observations are in concordance with other
studies that reported greater myocardial salvage in patients with early
complete reperfusion (TIMI grade 3) compared with those with incomplete
perfusion or occlusion of the infarct related artery (TIMI grades 2, 1,
or 0).20 Immediate PTCA during thrombolytic
therapy was performed in some of the patients in an attempt to improve
coronary reperfusion. However, at predischarge angiography,
coronary perfusion was not better after PTCA compared with
patients receiving alteplase only.14 In contrast, other
studies have shown that patients undergoing direct PTCA without
concomitant thrombolysis appeared to do better with a
greater proportion of TIMI grade 3 flow, smaller infarct size, better
preserved left ventricular function, and better
survival.21 22 This supports the notion that early,
complete reperfusion is the determinant of myocardial salvage, whereas
both early and late (before hospital discharge) complete perfusion are
determinants of long-term survival.
Conclusions
The salutary effect of reperfusion therapy with
intravenous rTPA is maintained throughout 5 years of
follow-up. There was no additional late beneficial effect of
systematic immediate PTCA in patients treated with rTPA. Long-term
prognosis for patients with myocardial infarction could be predicted
from infarct size, residual left ventricular function, and
the extent of coronary artery disease at discharge. TIMI
perfusion grade 2 at discharge should be considered as a result of
inadequate therapy.
Received October 25, 1994; revision received March 15, 1995; accepted March 19, 1995.
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