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* From the Instituto de Ciencias del Corazón, Hospital Universitario, Valladolid, Spain.
Correspondence to: José A. San Román, MD, PhD, Instituto de Ciencias del Corazón, Hospital Universitario, Avda Ramón y Cajal, 47008 Valladolid, Spain
| Abstract |
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Design: We analyzed 59 consecutive patients (42 men) aged
70 years (mean ± SD age, 75 ± 4 years) who underwent DSE
within 10 days after uncomplicated AMI. DSE was carried out following
the standard protocol. Five myocardial responses were considered: (1)
negative, (2) sustained improvement of contractility, (3) biphasic
response (initial improvement followed by worsening), (4) worsening of
contractility in the infarcted area, and (5) worsening at a distance.
Results: Mean follow-up duration was 13 ± 8 months. Twenty-one patients had an event: cardiac death (n = 5), myocardial infarction (n = 1), heart failure (n = 1), unstable angina (n = 10), and revascularization (n = 4). Clinical and stress echocardiographic variables previously related to adverse prognosis were entered in Cox regression analysis, and the predictors of impaired outcome were inducible ischemia during DSE (hazard ratio [HR], 2.97; 95% confidence interval [CI], 1.77 to 4.99; p < 0.001) and resting wall motion score index (WMSI) > 1.6 (HR, 1.68; 95% CI, 1.02 to 2.77; p = 0.04). After excluding revascularization procedures and considering only spontaneous events, the following predictors were found: ischemia during DSE (HR, 2.95; 95% CI, 2.78 to 3.12; p < 0.001) and resting WMSI > 1.6 (HR, 2.53; 95% CI, 1.30 to 4.93; p = 0.006).
Conclusions: Inducible ischemia during DSE within 10 days after uncomplicated AMI predicts an impaired outcome in the elderly.
Key Words: dobutamine echocardiography elderly myocardial infarction risk stratification
| Introduction |
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| Materials and Methods |
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70 years were admitted in the coronary care unit of our
hospital for AMI. Of these 310 patients, there were 68 deaths during
hospitalization. Patients with complicated AMI (Killip class
III [n = 76] and severe ventricular arrhythmias [n = 16])
and those included in other protocols (n = 31) were excluded. Thus,
110 patients were admitted to the hospital for uncomplicated AMI.
Twelve patients did not agree to participate in the study, and 30
patients underwent a revascularization procedure during hospitalization
(percutaneous [n = 22] and surgical [n = 8]), while 9 patients
had malignant or end-stage diseases. We prospectively studied the remaining 59 patients (42 men; mean ± SD age, 75 ± 4 years) who underwent DSE within 10 days after uncomplicated AMI. The criteria for AMI consisted of a rise in serum creatinine kinase MB isoenzyme > 10% of the normal laboratory level combined with chest pain lasting at least 30 min and/or ST-segment upward or downward deviation of at least 0.2 mV in two contiguous leads. Thus, the results are widely generalizable, as the sample is a representative one of elderly people admitted to the hospital in everyday practice due to CAD. No age limit was imposed, and both non-Q-wave and Q-wave AMI and patients who did and did not receive thrombolysis were included. DSE results were not included in the decision-making process regarding the management of the patient.
Dobnutamine Infusion
Dobutamine was IV administered with a pump in 3-min incremental
stages at infusion rates of 5, 10, 20, and 30 µg/kg body weight per
minute; then, dobutamine was administered at a dosage of 40 µg/kg/min
during 6 min. In patients not achieving 85% of their maximal predicted
heart rate or an end point, 1 mg of IV atropine was infused. A 12-lead
ECG and BP were recorded at rest and every 3 min up to 10 min after
finishing the infusion or recovery of contractility if the test result
was positive.
The usual nonechocardiographic end points were considered: maximal predicted heart rate; severe chest pain; intolerable headache or tremor; symptomatic hypotension, systolic BP > 220 mm Hg, diastolic BP > 130 mm Hg; Mobitz type II or third-degree heart block; complex ventricular arrhythmias; and ST-segment downward deviation > 0.3 mV.
Echocardiography
An 11-segment model of the left ventricle was used to assess
regional wall motion. The assessed segments were proximal anteroseptal,
distal anteroseptal, proximal posteroseptal, distal posteroseptal,
proximal anterolateral, distal anterolateral, apical, proximal
posterolateral, distal posterolateral, posterobasal, and diaphragmatic.
Continuous two-dimensional echocardiography from parasternal (long-axis and short-axis) and apical (four-chamber, two-chamber, and three-chamber) views was performed throughout dobutamine infusion and up to 10 min after the end of the test. In those patients without adequate transthoracic view, transesophageal echocardiography was performed (n = 2).
Each segment was graded as follows: (1) normal and hyperkinetic, (2) mild hypokinetic, (3) severe hypokinetic, and (4) akinetic and dyskinetic. Wall motion score index (WMSI) was derived by dividing the sum of individual segment scores by the number of interpretable segments. It was evaluated at baseline, at low dose, and at peak stress. The difference between low-dose WMSI and baseline WMSI and the difference between peak-stress WMSI and baseline WMSI were used to estimate the extent of myocardium with contractile reserve and the extent of ischemic myocardium, respectively.
The following five myocardial responses were considered: (1) negative (improvement of contractility and thickening from a normal myocardium or no changes at all); (2) sustained improvement of contractility from a hypokinetic, akinetic, or dyskinetic segment; (3) biphasic response (improvement of contractility from a hypokinetic, akinetic, or dyskinetic segment followed by worsening of contractility); (4) worsening of contractility in the infarcted zone (homozonal ischemia); and (5) worsening of contractility at a distance (heterozonal ischemia). Patients were separated into three groups according to the myocardial responses: negative group (response 1), viable and nonischemic group (response 2), and viable and ischemic group (responses 3, 4, and 5).
Image acquisition was gated with ECG signal and was digitized comparing four images of the same view at the different stages (basal, low dose, high dose, and atropine) in order to analyze them. The studies were also recorded on conventional videotape. Dobutamine tests were performed by the same echocardiographist with proven proficiency (> 500 studies done).
Follow-up Data
Follow-up data were obtained from regular outpatient
clinic visits, phone interviews by medical personnel, and reviews of
patient clinical files when needed. The worst adverse event was the
only one taken into account. Adverse events considered were
cardiac-related death, AMI, severe congestive heart failure (hard
events), unstable angina, and revascularization (soft events). Death
was assumed to be cardiac when it was sudden and/or noncardiac death
was ruled out after detailed analysis of clinical and laboratory data
obtained during hospital admission and/or pathology findings in
necropsy. Noncardiac deaths were censored at follow-up. Nonfatal AMI
was defined as a hospital admission for prolonged chest pain (> 30
min) and/or ECG changes and documented typical creatinine kinase MB
curve. Severe congestive heart failure included pulmonary edema, New
York Heart Association functional class IV/IV, and that which needed
hospital admission. Unstable angina was defined as that with an
accelerated pattern or at rest requiring hospital admission.
Statistical Analysis
Prognosis after AMI depends strongly on aging: the older the
patient, the more adverse the prognosis. During the first year after
AMI, 40% of patients > 65 years old will have an adverse
cardiovascular event.5
6
To predict at least 50% of those
events (a 20% difference) with a type-1 error of 0.05 and a
type-2 error of 0.10, and thinking that 5% of the patients could be
unavailable for follow-up, the necessary sample was 58 patients. The
statistical power was 90%.
Numerical data are expressed as mean (SD). The results of categorical
variables are given in percentages. Clinical variables (n = 11) and
echocardiographic variables (n = 17) previously related with poor
prognosis entered the univariate analysis. Continuous variables were
compared by the unpaired two-sample t test and proportions
by the
2 statistic; two-tailed Fishers Exact
Test was used when appropriate. A p value < 0.05 was considered
statistically significant. Prognostic indicators were obtained by Cox
regression carried out using software (SPSS 9.0; SPSS; Chicago,
IL). The Cox model met assumption of proportionality, and hazard ratios
(HRs) with 95% confidence intervals (CIs) were calculated for those
variables with statistically significance. Kaplan-Meier curves were
used to compare survival free of events using the log-rank test.
| Results |
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Cardiac deaths were as follows: AMI, cardiogenic shock due to heart failure, sudden death, pulmonary edema, and cardiogenic shock due to refractory unstable angina. There were five noncardiac deaths, three caused by stroke (ischemic [n = 2] and hemorrhagic [n = 1]) and one by respiratory distress secondary to Haemophilus influenzae pneumonia, and one patient died after catheterization due to severe bleeding.
Analysis of Clinical and Echocardiographic Variables
The main clinical characteristics of patients with and
without events are summarized in Table 1
. Both groups were similar regarding most variables previously known to
be related with poor prognosis, including risk factors and
infarction characteristics, except for a significant higher
prevalence of anterior infarction in the nonevent group. Of patients
with an event, diabetes showed a trend to be more frequent.
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| Discussion |
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70 years who developed
inducible ischemia during DSE are at higher risk of adverse cardiac
events during follow-up and a negative response predicts a good
outcome. The prognostic value of DSE in patients with CAD with and without AMI has been extensively reported on.12 13 14 15 16 17 18 19 It is a safe technique in elderly patients.9 10 11 Furthermore, the usefulness of the test is not dependent on the physical ability of the patient. Although dipyridamole stress echocardiography has been used in the postinfarction period in the elderly,19 the choice of dobutamine instead of dipyridamole might be advantageous. At low dose, dobutamine is a recognized technique for detecting viability.20 21 22 Besides, dobutamine is safer in patients with COPD, whose prevalence is high among this subset of patients. The reduced myocardial response to ß-adrenergic stimulation present in elderly individuals may impair the ability of dobutamine to induce ischemia.23 24 However, the addition of atropine avoids this potential drawback.10 Poldermans et al10 and Baudhuin et al11 assessed DSE in elderly patients. In their studies, DSE sensitivity, specificity, and predictive values were found to be high and similar to those in younger patients.
Previous investigations12
13
14
15
16
analyzed the prognostic
value of DSE in the postinfarction period in the general population.
Picano et al12
showed that the development of ischemia
during DSE was the best predictor of cardiac death in patients with
severe left ventricular dysfunction. In that study,12
viability was associated with a better outcome, and the higher the
number of segments showing improvement of function, the better the
impact on survival; however, patients > 75 years old were excluded.
Carlos et al15
found that the extent of infarction, global
left ventricular function, lack of response to low-dose dobutamine
(nonviability), and ischemia at a distance were powerful predictors of
adverse spontaneous events. Although age was not among the exclusion
criteria, the patients were younger than ours (the study population had
a mean age of 58 ± 13 years). Previtali et al13
studied
patients with a first AMI treated with thrombolysis and concluded that
the presence and extent of ischemia were related to impaired prognosis,
whereas viability was not. Again, older patients (
70 years) were
excluded. Finally, Sicari et al14
obtained somewhat
different results in patients with preserved left ventricular function:
ischemia predicted hard events, and viability was associated with the
appearance of unstable angina.
Therefore, there is agreement that inducible ischemia marks an adverse outcome, but the meaning of viability remains controversial. Our results in the elderly are in agreement with those reported on in the general population and support the negative impact of ischemia on prognosis. Regarding viability, the extent of contractile reserve in the univariate analysis was greater in the nonevent group. Sustained improvement of contractility early after AMI occurs in stunned myocardium, which is likely to recover spontaneously with time. This recovery will improve left ventricular dysfunction and prognosis. However, this variable was related neither to better outcome nor to worse prognosis after stepwise Cox regression analysis. Finally, a moderate-to-severe left ventricular dysfunction (baseline WMSI > 1.6) was also found to predict poor outcome, and this fact has been previously shown25 to impair prognosis.
Limitations of This Study
It can be argued that revascularization is not an event, as it is
a subjective decision. However, results did not differ after excluding
the four patients with revascularization. In other words, DSE predicted
both spontaneous and total events.
Regarding the extent of contractile reserve, a ß-type error cannot be excluded due to the small number of patients. It would be necessary to undertake an analysis with enough patients to show its possible beneficial effect on prognosis.
DSE was performed by one echocardiographer. Although some may deem this improper, this echocardiographer has proven expertise26 by consistently interpreting large numbers of stress echocardiograms, and interinstitutional variability27 was avoided, making the results more homogeneous. Furthermore, it reflects the common clinical practice in a busy echocardiography laboratory of a major center. The lack of postdischarge management data is also a limitation of this study because a better long-term outcome has been shown with several drugs and certain lifestyle modifications.
| Conclusion |
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| Footnotes |
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Received for publication February 28, 2000. Accepted for publication April 17, 2001.
| References |
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This article has been cited by other articles:
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M. Martinez-Selles, R. Lopez-Palop, E. Perez-David, and H. Bueno Influence of Age on Gender Differences in the Management of Acute Inferior or Posterior Myocardial Infarction Chest, August 1, 2005; 128(2): 792 - 797. [Abstract] [Full Text] [PDF] |
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