Summary
Background
Left ventricular systolic function is a useful indicator of in-hospital prognosis in patients with acute myocardial infarction. For long-term risk stratification, however, the variable degree of recovery that may occur during the ensuing period has also to be taken into account.
Aims
To analyse the prevalence, time course, determinants and correlates of late left ventricular function recovery after myocardial infarction, from hospital discharge to 1-year follow-up, using systematic serial assessment of left ventricular function.
Methods
Data from 512 patients with a first anterior myocardial infarction included in two prospective studies on left ventricular remodelling (REVE and REVE-2) were analysed. Serial echocardiographic studies were performed before discharge, at 3 months and at 1 year after myocardial infarction. Left ventricular volumes, ejection fraction, and Wall Motion Score Index were determined at a core echocardiographic laboratory.
Results
In both cohorts, there was a significant decrease in Wall Motion Score Index between discharge and 1 year (from 1.87 ± 0.15 to 1.71 ± 0.21 [ P < 0.0001] in REVE; and from 1.91 ± 0.15 to 1.64 ± 0.28 [ P < 0.0001] in REVE-2), indicating an improvement in systolic function. Left ventricular ejection fraction increased from 49.6 ± 9.5% at baseline to 51.5 ± 9.5% at 1 year in REVE ( P < 0.008), and from 49.8 ± 8.3% to 55.5 ± 9.8% in REVE-2 ( P < 0.0001). Most of the recovery occurred within the first 3 months after discharge, but there was still significant recovery between 3 months and 1 year. Peak creatine kinase was the sole variable independently associated with left ventricular function recovery in both studies. Patients with no or minimal function recovery had the greater increase in left ventricular volumes at 1 year.
Conclusions
Late recovery in left ventricular function is common after discharge in patients with acute myocardial infarction. Further research is needed to identify new parameters that may help to predict this favourable outcome.
Résumé
Introduction
L’existence d’une dysfonction systolique ventriculaire gauche est un paramètre pronostique important en cas d’infarctus du myocarde. Cependant, le pronostic à long terme va aussi dépendre de l’importance de la récupération qui peut survenir secondairement.
Objectifs
Analyser chez des patients ayant un suivi échocardiographique systématique après infarctus, la prévalence, le délai, les facteurs prédictifs et les conséquences de la récupération tardive de fonction systolique entre la sortie de l’hôpital et la fin de la première année.
Méthodes
Nous avons utilisé les données de 512 patients avec un premier infarctus antérieur inclus dans deux études prospectives sur le remodelage ventriculaire gauche (REVE et REVE-2). Une échocardiographie a été réalisée avant la sortie, après trois mois et après un an. Les volumes ventriculaires, la fraction d’éjection et le Wall Motion Score Index ont été obtenus par lecture centralisée des échocardiographies.
Résultats
Une amélioration de la fonction systolique pendant l’année suivant la sortie (diminution du Wall Motion Score Index) a été mise en évidence dans les deux études (de 1,87 ± 0,15 à 1,71 ± 0,21 [ p < 0,0001] dans REVE et de 1,91 ± 0,15 à 1,64 ± 0,28 [ p < 0,0001] dans REVE-2). La fraction d’éjection ventriculaire gauche a augmenté de 49,6 ± 9,5 % à 51,5 ± 9,5 % dans REVE ( p = 0,008) et de 49,8 ± 8,3 % à 55,5 ± 9,8 % dans REVE-2 ( p < 0,0001). L’essentiel de la récupération est survenu lors des trois premiers mois après la sortie mais une amélioration significative a encore été notée entre trois mois et un an. La seule variable associée de manière indépendante à la récupération de fonction dans les deux études a été la valeur maximale de créatine kinase. Les patients avec récupération de fonction minime ou absente ont eu l’augmentation la plus importante des volumes ventriculaires gauches à un an.
Conclusions
La récupération tardive de fonction systolique est fréquente après la sortie de patients hospitalisés pour infarctus du myocarde. Il est nécessaire de mieux définir les variables permettant de prédire cette évolution favorable.
Introduction
The treatment of patients with acute MI has improved considerably over the past decades. The widespread use of acute reperfusion strategies and improvements in medical therapies have been associated with significant decrease in event rates . However, an important proportion of the patients sustaining MI still presents with significant decrease in LV systolic function . Early identification of these patients is important since they may benefit from specific management such as more intense antiremodelling therapy, pronounced follow-up or automated implanted cardioverter-defibrillator .
LV systolic function is a useful indicator of in-hospital prognosis in patients with acute MI . For long-term risk stratification, however, the variable degree of recovery that may occur during the ensuing period, and which has been related to recovery of LV stunning and/or the effect of medical therapies, has also to be taken into account. Most recent investigations in this field have analysed changes in LV function between an early time point (i.e., within the first 24 or 48 hours after admission) and a late time point (i.e., several weeks or months after MI), thereby analysing globally in-hospital and post-discharge recovery . Although this approach encompasses all components of LV function recovery, it does not really match with current practice where predischarge evaluation of LV function is readily available, and where the remaining clinical question is more to anticipate the amount of recovery that occurs after discharge. We therefore designed the present study to analyse the prevalence, time course, determinants and correlates of late LV function recovery, from hospital discharge to 1 year after the acute event, in two recent cohorts of patients, using a systematic serial assessment of LV function.
Methods
Study population
The design, and inclusion and exclusion criteria of the REVE studies have been published in detail elsewhere . REVE was designed to test the hypothesis that genetic polymorphism in candidate genes may be associated with LV remodelling . REVE-2 was designed to study the association of circulating biomarkers with LV remodelling . Both studies were multicentre and prospective. The inclusion criteria were the same for the two studies: first anterior Q-wave MI with at least three LV segments that were akinetic at predischarge echocardiography. Inclusion periods were February 2002 to June 2004 for REVE (266 patients) and February 2006 to September 2008 for REVE-2 (246 patients). The protocols were approved by the ethics committee of the Centre Hospitalier et Universitaire de Lille, Lille, France, and written informed consent was obtained from each patient. In both studies, the protocol required serial echocardiographic studies at baseline, at 3 months and at 1 year after MI. For those patients who did not return at the designated times, information on their clinical status was obtained through telephone interviews.
Echocardiographic studies
Echocardiographic data were obtained using commercially available second harmonic imaging systems. Echocardiograms were performed by experienced ultrasonographers and repeated by the same operator wherever possible. Images were recorded on optical discs. A standard imaging protocol was used based on apical 4- and 2-chamber views; two-dimensional echocardiograms of the LV short axis were recorded from the left parasternal region at three levels: mitral valve, mid-papillary muscle level and apex. All echocardiograms were analysed at the Lille Core Echo Laboratory on a Philips workstation, with each echocardiographic variable analysed by one investigator. LV volumes and EF were calculated using a modified Simpson’s rule. Intra- and interobserver variability in the evaluation of LV end-diastolic volume and end-systolic volume has been previously reported . To evaluate regional systolic function, the left ventricle was divided according to a 16-segment model as recommended by the American Society of Echocardiography . For each segment, wall motion was scored from 1 (normal) to 4 (dyskinetic), and the WMSI was derived; the normal WMSI value is 1.00. Percent LV function recovery was defined as ((WMSI baseline – WMSI 1 year ) × 100)/(WMSI baseline – 1) as an indicator of the amount of LV dysfunction at discharge that had recovered at 1 year. LV remodelling was defined as a greater than 20% increase in end-diastolic volume between baseline and the 1-year follow-up examination.
Statistical analysis
STATA 9.0 (STAT Corp. College Station, Texas) was used for the statistical analysis. Quantitative variables are presented as the mean ± standard deviation or median with 25th and 75th percentiles unless otherwise indicated. Variables with skewed distribution were log-transformed before being used as continuous variables in statistical analyses. Continuous variables were compared with the paired or unpaired Student’s t -test, ANOVA, or with simple linear regression as appropriate. Discrete variables were compared using Chi-squared analysis. A P value < 0.05 was considered statistically significant. Independent predictors of percent recovery in LV function were identified by multiple linear regression. Variables significant on univariate analysis were entered in the multivariable model. Colinearity was excluded by means of a correlation matrix between candidate predictors.
Results
Patients
Table 1 compares the baseline characteristics of the patients included in the two studies. The patients included in REVE-2 were more often treated by primary PCI and less often by thrombolysis. Baseline echocardiography was performed earlier in REVE-2. Baseline EF was similar in both studies while WMSI was slightly higher in REVE-2.
| REVE | REVE-2 | |
|---|---|---|
| Number of patients | 266 | 246 |
| Recruitment period | 2002–2004 | 2006–2008 |
| Age (years) | 58.2 ± 13.8 | 57.0 ± 13.8 |
| Women | 67 (25) | 46 (19) |
| Body mass index (kg/m 2 ) | 27.0 ± 4.7 | 27.1 ± 4.6 |
| Hypertension | 120 (45) | 89 (36) a |
| Current smoker | 122 (46) | 116 (47) |
| Diabetes mellitus | 60 (23) | 51 (21) |
| Initial reperfusion therapy | ||
| Thrombolysis | 142 (54) | 87 (35) b |
| Primary PCI | 78 (29) | 128 (52) b |
| No reperfusion therapy | 46 (17) | 31 (13) |
| Time from symptom onset to reperfusion (hours) | 4 [2–7] | 3.5 [2–7] |
| Killip class ≥ II | 71 (27) | 79 (32) |
| Peak creatine kinase (IU/L) | 2549 [1234–3984] | 2353 [1447–4198] |
| Coronary angiography during hospitalization | 263 (99) | 243 (99) |
| Multivessel coronary artery disease | 101 (38) | 98 (40) |
| PCI during hospitalization | 235 (89) | 212 (86) |
| Stent implantation | 232 (87) | 208 (85) |
| Final TIMI flow in the infarct-related vessel grade 3 | 220 (84) | 213 (91) a |
| Time from admission to baseline echography (days) | 7 [5–9] | 4 [3–5] b |
| Ejection fraction (%) | 49.2 ± 9.5 | 49.3 ± 8.5 |
| Wall motion score index | 1.87 ± 0.15 | 1.91 ± 0.15 a |
| End-diastolic volume (mL/m 2 ) | 56.5 ± 14.9 | 52.3 ± 14.0 a |
| End-systolic volume (mL/m 2 ) | 29.0 ± 10.6 | 26.9 ± 10.5 a |
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