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Long-term effects of intracoronary bone marrow cell transfer on diastolic function in patients after acute myocardial infarction: 5-year results from the randomized-controlled BOOST trial—an echocardiographic study

Arnd Schaefer, Carolin Zwadlo, Martin Fuchs, Gerd P. Meyer, Peter Lippolt, Kai C. Wollert, Helmut Drexler
DOI: http://dx.doi.org/10.1093/ejechocard/jep191 165-171 First published online: 28 November 2009

Abstract

Aims We have recently observed that intracoronary autologous bone marrow cell (BMC)-transfer improves parameters of diastolic function in patients after acute myocardial infarction at 6 and 18 months. There is no clinical study addressing the long-term effect of BMC transfer on diastolic function. Therefore, we conducted a 5-year follow-up of the BOOST trial to evaluate a sustained benefit on echocardiographic parameters on diastolic function.

Methods and results After successful primary percutaneous coronary intervention (PCI) for acute ST-elevation MI, patients were randomized to a control (n = 28) or BMC transfer group (n = 28). Echocardiography was performed at 4.5 ± 1.5 days after PCI, at 6, 18, and 60 months. Diastolic function was determined by measuring transmitral flow velocities (E/A ratio), diastolic myocardial velocities (Ea/Aa ratio), isovolumic relaxation time (IVRT), and deceleration time (DT). All analyses were performed in a blinded fashion. There was an overall treatment effect of BMC transfer on E/A (0.25 ± 0.10; 95% CI 0.05–0.44; P = 0.01). E/A ratio was significantly lower at 6 (Control 0.90 ± 0.07; BMC 1.23 ± 0.14; P = 0.03) and 18 months (Control 0.87±0.04; BMC 1.13 ± 0.09; P = 0.01) in the control group, whereas E/A ratio was not different at 60 months between both groups (Control 0.90 ± 0.06; BMC 1.05 ± 0.07; P = 0.12). We found no overall effect of BMC transfer on Ea/Aa ratio (0.21 ± 0.14; 95% CI −0.03 to 0.46; P = 0.09), DT (−12 ± 11 ms; 95% CI −21 to 28; P = 0.75), IVRT −6 ± 7 ms; 95% CI −9 to 19; P = 0.43), and E/Ea ratio (0.58 ± 0.88; 95% CI −1.18 to 2.34; P = 0.51).

Conclusion Intracoronary autologous BMC transfer provides an overall treatment effect on echocardiographic parameters of diastolic function in patients after AMI. However, this effect is basically related to an early improvement of parameters of diastolic function without a sustained effect on long-term follow-up.

  • Bone marrow cell therapy
  • Diastolic function
  • Acute myocardial infarction
  • Echocardiography

Introduction

Left ventricular (LV) diastolic dysfunction is a frequent complication after acute myocardial infarction (AMI) and is associated with an increased risk for the development of heart failure, even when LV ejection fraction (LVEF) is well preserved.14 Therefore, prevention of diastolic dysfunction after AMI should receive a high priority, especially since treatment strategies for patients with diastolic dysfunction remain poorly defined.5

In this context, animal studies suggesting that myocardial transfer of bone marrow-derived stem and progenitor cells may enhance recovery of systolic and diastolic function after AMI have created a lot of excitement.611 Building on these experimental findings, we have conducted the randomized-controlled BOOST trial to assess the impact of intracoronary autologous bone marrow cell (BMC) transfer on LV systolic and diastolic function in patients recovering from an acute ST-segment elevation AMI. As previously reported, intracoronary BMC application led to a significant improvement in regional systolic wall motion and global LVEF after 6 months in the BOOST trial,12 a treatment effect that was, however, not maintained after 18 months.13 Notably, echocardiographic parameters of diastolic function (E/A and Ea/Aa ratio) were improved up to 18 months after BMC transfer in the BOOST trial.14 In the present investigation, we have re-assessed echocardiographic parameters of diastolic function in the BOOST study population after 60 months to explore, if BMC therapy can lead to a sustained improvement of LV diastolic function after AMI.

Methods

Study design

The study protocol and the 6 and 18 months’ follow-up results of the BOOST trial have been published.14, In brief, patients with a first STEMI, who had undergone percutaneous coronary intervention (PCI) with stent implantation of the infarct-related artery, and who demonstrated hypokinesia or akinesia involving more than two-thirds of the LV anteroseptal, lateral, and/or inferior wall, as shown by LV angiography immediately after PCI, were eligible for the trial. Patients were randomized 1:1 to the control (n = 30) and BMC transfer groups (n = 30). In the BMC transfer group, BMCs were harvested, processed by gelatine–polysuccinate density gradient sedimentation, and infused into the infarct related artery 4.8 ± 1.3 days after PCI. The baseline echocardiographic examination was performed 4.5 ± 1.5 days after PCI. Echocardiography was repeated at 6 ± 1, 18 ± 6, and 60 ± 11 months after PCI. No patient was lost to follow-up. All patients were treated according to current practice guidelines. The trial was approved by the Ethics Committee at Hannover Medical School and has been registered at www.clinicaltrials.gov (registration number, NCT00224536).

Echocardiography

Echocardiography and MRI analyses were performed by three investigators blinded for treatment assignment (A.S., M.F., and C.Z.). ATL HDI 5000 CV and Philips iE 33 ultrasound systems with a 2–4 MHz transducer and second harmonic imaging were used. Echocardiographic examinations were performed according to the recommendations for the assessment of systolic and diastolic function and valvular heart disease issued by the American Society of Echocardiography (ASE).1517 LV diastolic function was assessed using transmitral inflow parameters [transmitral peak early (E) and peak late velocity (A), E-wave deceleration time (DT)]. E/A ratio was calculated. Isovolumic relaxation time (IVRT) was recorded from the apical four-chamber view by simultaneous recording of LV outflow tract and mitral flows. Doppler tissue imaging recordings were obtained from the lateral mitral valve annulus. Early diastolic (Ea) and late diastolic (Aa) velocities were measured, and Ea/Aa and E/Ea ratios were calculated. All Doppler-derived parameters were measured and averaged during expiration from five consecutive beats. LVEF was calculated by the biplane disc summation method according to the modified Simpson's rule using the apical four- and two-chamber views.18,19 Aortic and mitral regurgitation were classified according to the ASE recommendations as being mild, moderate, or severe. The presence or absence of pericardial effusion and LV thrombi was assessed from parasternal, apical, and subcostal views. Values for inter-observer and intra-observer variability of echocardiographic parameters were low and have been reported previously.14

Cardiac magnetic resonance imaging

MRI was performed with a General Electric CV/i 1.5 T scanner using ECG gating and a four-element phased array surface coil during repeated breath-holds. Sequence parameters, image planning, and methods for the evaluation of LV volumes, and global and regional LV function have been reported.13 For infarct size determination, LV myocardial tissue showing late contrast enhancement was quantified. Within the myocardial sector displaying late contrast enhancement, infarct transmurality was defined as the ratio of the hyperenhanced (mostly subendocardial) region to the hyperenhanced plus non-hyperenhanced (mostly subepicardial) regions.

Statistical analysis

To analyse effect of BMC transfer on diastolic function throughout the course of 60 months, repetitive measurements were compared using the general linear model (GLM) repeated measures procedure (repeated measures ANOVA) (SPSS version 15.0). In this model, BMC treatment was used as the fixed factor (between-subject factor group) and the echocardiographic measurements at 6, 18, and 60 months as the dependent variable ‘time’ with three levels (within factor time at 6, 18, and 60 months). No random effects were included in the GLM model (fixed model analysis). Estimated overall treatment effects (mean difference between both groups throughout the observation period) and their corresponding confidence intervals were determined by pairwise comparison of the means with Bonferroni correction for multiple comparisons within the repeated measures design. Differences between the means of both groups (independent variable) at baseline, 6, 18, or 60 months (dependent variable) were assessed by one-way ANOVA. For within-group comparison of baseline and 60 months values a paired t-test was used.

In addition to the analyses in the overall patient population, diastolic function was assessed in two subgroups, defined according to infarct transmurality or hypertension at baseline. As previously reported, patients with an infarct transmurality greater than the median appear to benefit from intracoronary BMC transfer with a lasting improvement of LVEF even after 18 months.13 We have also observed that patients with a diagnosis of hypertension at baseline did not benefit from BMC transfer with an improvement of diastolic function at 18 months.14

Categorical variables were compared by using the χ2 test and Mann–Whitney test. All data are expressed as means ± SEM. All tests were two-sided, and P-values less than 0.05 were considered to indicate statistical significance.

Results

Patient population

Sixty patients with a mean age of 56 ± 14 years and a first ST-segment elevation AMI were randomized to the control (n = 30) and the BMC transfer (n = 30) groups, respectively. A detailed characterisation of the study population has been published. Two patients from the control group and two patients from the BMC group died during follow-up. Accordingly, complete echocardiographic follow-up data were obtained in 28 patients from each group, and our analyses were restricted to these patients. At 60 months, 26 control and 27 BMC transfer patients were treated with aspirin and/or clopidogrel, 24 and 25 patients with an ACE-inhibitor or AT1-receptor antagonist, 25 and 25 with a β-blocker, 24 and 24 with a statin, and 2 and 1 with an aldosterone antagonist (P = n.s. for all comparisons).

All patients were in sinus rhythm during echocardiography. There were no significant differences in systolic or diastolic blood pressure and heart rate between the two groups. Throughout the study period, there were no significant differences in the prevalence of LV thrombi (4% for both groups) or pericardial effusion between both groups (0% Control vs. 4% BMC; P = 0.37); there were also no significant differences with regard to the prevalence of mitral regurgitation (21% Control vs. 28% BMC; P = 0.16), aortic regurgitation (7% Control vs. 7% BMC), or mitral and aortic stenosis (0% for both groups). No patient presented with echocardiographic signs of intramyocardial calcifications or tumour formation.

Diastolic function in the overall patient population

Changes in diastolic and additional parameters (heart rate, blood pressure, and ejection fraction) from baseline to 60 months’ follow-up are presented in Table 1 and illustrated in Figures 1 and 2. At baseline, no significant differences in diastolic function were noted between both groups. In the entire patient population, E/A ratio, IVRT, and E/Ea ratio remained unchanged (P = 0.29; P = 0.08; P = 0.51), Ea/Aa ratio decreased (P = 0.003), and DT (P = 0.001) increased over the course of 60 months.

Figure 1

(A) Time course of E/A ratio [ratio of transmitral peak early (E) and peak late velocity (A)]; P-values for between group comparison (one-way ANOVA). P = 0.015 for overall treatment effect. (B) Time course of Ea/Aa, [ratio of early diastolic (Ea) and late diastolic (Aa) mitral anulus velocity]; P-values for between group comparison. P = 0.09 for overall treatment effect. (C) Time course of E/Aa, [ratio of transmitral peak early (E) and late diastolic (Aa) mitral anulus velocity); P-values for between group comparison. P = 0.51 for overall treatment effect.

Figure 2

(A) Time course of deceleration time (DT). P = 0.75 for overall treatment effect. (B) Time course of isovolumic relaxation time (IVRT). P = 0.43 for overall treatment effect.

View this table:
Table 1

Heart rate, blood pressure, and left ventricular ejection fraction

Control group (n = 28)BMC group (n = 28)P-value between group
Heart rate (b.p.m.)
 Baseline71 ± 273 ± 20.45
 6 Months67 ± 268 ± 20.68
 18 Months68 ± 269 ± 20.62
 60 Months69 ± 274 ± 30.23
LVEF (%)
 Baseline50 ± 249 ± 20.62
 6 Months53 ± 252 ± 20.53
 18 Months53 ± 352 ± 20.85
 60 Months55 ± 255 ± 20.92
BP (mmHg)
 Baseline120/72 ± 2/2116/69 ± 3/20.19/0.30
 6 Months117/74 ± 2/1120/75 ± 3/10.23/0.74
 18 Months116/75 ± 2/2119/74 ± 2/10.51/0.61
 60 Months136/80 ± 3/1138/79 ± 4/10.75/0.53
  • BP, arterial blood pressure (systolic and diastolic values are shown); LVEF, left ventricular ejection fraction; P-value denotes the comparison of the means between control and BMC group at baseline, 6 18, and 60 months (one-way ANOVA).

Time trend of diastolic function in both groups

In the control group, E/A and Ea/Aa ratios decreased (P = 0.010; P = 0.030), whereas DT increased (P = 0.032) from baseline to 60 months’ follow-up. In the BMC group, E/A and Ea/Aa ratios remained unchanged (P = 0.26; P = 0.06) and DT increased (P = 0.003) over the course of 60 months. IVRT and E/Ea remained unchanged in both groups.

Differences between both study groups

The BMC transfer group had a significantly higher E/A ratio 6 and 18 months after cell transfer when compared with the control group (Figure 1A). No significant difference was observed after 60 months, however. Throughout the course of 60 months, BMC therapy was associated with a significant overall treatment effect (mean difference) on E/A ratio (Table 2).

View this table:
Table 2

Overall treatment effect (mean difference between both groups) of bone marrow cell therapy on diastolic parameters over the course of 60 months

Mean differenceaP-value
E/A0.25 ± 0.10 (0.05–0.44)0.015
Ea/Aa0.21 ± 0.14 (−0.03 to 0.46)0.09
E/Ea0.58 ± 0.88 (−1.18 to 2.34)0.51
DT (ms)−12 ± 11 (−21 to 28)0.75
IVRT (ms)−6 ± 7 (−9 to 19)0.43
  • E/A, ratio of transmitral peak early (E) and peak late velocity (A); Ea/Aa, ratio of early diastolic (Ea) and late diastolic (Aa) mitral annulus velocity; DT, deceleration time; IVRT, isovolumic relaxation time; 95% confidence intervals are between parentheses.

  • aWith Bonferroni correction for multiple comparisons.

Ea/Aa ratio was significantly higher in the BMC transfer group at 18 months (Figure 1B). However, no significant differences in Ea/Aa ratio were noted at 6 and 60 months, and no significant overall treatment effect of BMC transfer was observed over the course of 60 months (Table 2). No significant differences in DT, IVRT, and E/Ea ratio were noted between the control and BMC transfer groups throughout the observation period (Table 2).

Diastolic function at follow-up in subgroups

Patients with an infarct transmurality at baseline above the median (60.2%) displayed a greater overall treatment effect on E/A ratio over the course of 60 months when compared with patients with an infarct transmurality smaller than the median (Figure 3). E/A ratio was significantly higher at 60 months in patients with an infarct transmurality greater than the median but not in patients with an infarct transmurality smaller than the median (Figure 4).

Figure 3

Effect of BMC on mean difference, with Bonferroni correction for multiple comparisons for overall treatment effect in different subgroups. P-value for the comparison between Control and BMC group. E/A, ratio of transmitral peak early (E) and peak late velocity (A). #Infarct transmurality indicates ratio of the hyperenhanced region to the hyperenhanced plus non-hyperenhanced regions as determined by MRI (median = 60.2%).

Figure 4

Effect of BMC on E/A ratio in different subgroups at 60 months. E/A, ratio of transmitral peak early (E) and peak late velocity (A). #Infarct transmurality indicates ratio of the hyperenhanced region to the hyperenhanced plus non-hyperenhanced regions as determined by MRI (median = 60.2%).

BMC transfer was not associated with an overall treatment effect on E/A ratio over the course of 60 months in patients with a diagnosis of hypertension at randomization (Figure 3); conversely, a significant overall treatment effect was observed in non-hypertensive patients.

E/A ratio was not significantly different at 60 months in patients with and without hypertension at randomization (Figure 4). There was no interaction of infarct transmurality or hypertension on IVRT, DT, E/Ea, and Ea/Aa ratio (data not shown).

Discussion

To our knowledge, this is the longest follow-up assessing the course of echocardiographic parameters of diastolic function in patients after AMI. Our data show that in patients after AMI E/A, Ea/Aa ratios decreased over a course of 5 years despite preserved systolic function and optimal medical therapy.

In addition, this is the first study evaluating the long-term effects of intracoronary BMC transfer on echocardiographic parameters of diastolic function after AMI. The present 5-year investigation of the BOOST trial shows that a single dose of BMCs is safe. However, sustained improvement of echocardiographic parameters was not achieved by BMC transfer.

We have recently shown that intracoronary autologous BMC transfer improves echocardiographic parameters of diastolic function in patients after AMI.14 At 18 months follow-up of the BOOST trial, there was an overall treatment effect (mean difference) of BMC transfer on E/A ratio (0.33 ± 0.12; 95% CI 0.09–0.57; P = 0.008) and Ea/Aa ratio (0.29 ± 0.14; 95% CI 0.01–0.57; P = 0.04) but no effect on IVRT, DT, and E/Ea ratio. The present 5-year follow-up revealed an overall treatment effect of BMC transfer on E/A ratio but does not provide evidence of any treatment effect on additional echocardiographic parameters of diastolic function (Ea/Aa, IVRT, DT, and E/Ea).

With regard to the recommended classification of diastolic function by echocardiography Stage I diastolic function (mild diastolic dysfunction or impaired relaxation is defined by an E/A ratio less than 1, a prolongation of DT > 220 ms, an increase of IVRT > 100 ms, and a normal atrial pressure with or without reduced LV compliance.15,2022 Therefore, over a period of 5 years patients from the control group developed Stage I diastolic dysfunction after AMI (decreased E/A ratio, and prolongation of IVRT and DT, no change in E/Ea ratio), whereas patients from the BMC transfer group developed a very mild form of early diastolic dysfunction (prolongation of IVRT only).

However, our study shows that the overall benefit of BMS transfer on diastolic parameters was attenuated during long-term follow-up. It appears that a consolidation of E/A and Ea/Aa ratio emerged in the control group starting 18 months after randomization. In addition, BMC transfer only transient improves E/A and Ea/Aa ratio up to 18 months after AMI, because we found no significant difference between both groups at 5-year follow-up for both parameters.

We have previously shown by subgroup analyses that patients with hypertension might benefit less from BMC therapy.14 This is confirmed by our current analyses where in patients with hypertension at baseline no effect of BMC therapy could be detected. In addition, patients with non-infarct transmurality as indicated by MRI did not benefit from BMC transfer. Notably, these findings were in accordance with our analyses of systolic function as determined by MRI. Analyses at the 5-year follow-up of the BOOST trial have indicated that patients with a greater infarct transmurality may respond to BMC therapy with a prolonged treatment effect concerning systolic function as determined by MRI.23 Thus, only patients with greater infarct transmurality seemed to be at greater risk and may benefit more from BMC transfer. However, given the size of our trial, such post hoc subgroup analyses have to be viewed with great caution and should be used as hypothesis generating only. It is interesting to note, however, that subgroup analyses from the Reinfusion of Enriched Progenitor Cells and Infarct Remodelling in Acute Myocardial Infarction (REPAIR-AMI) trial, have indicated that patients with more severely depressed LVEF at baseline may derive the greatest benefit from BMC therapy.24 Furthermore, patients with more severely depressed baseline LVEF benefited more from BMC transfer in terms of LVEF improvement also in the Myocardial Regeneration by Intracoronary Infusion of Selected Population of Stem Cells in Acute Myocardial Infarction (REGENT) trial.25

The BOOST trial is the longest follow-up randomized study. In this context, several safety issues have to be addressed. We observed no increase in the prevalence of LV thrombi, pericardial effusions, or valvular disease after 5 years between both groups.

In conclusion, intracoronary autologous BMC transfer provides a sustained overall treatment effect on echocardiographic parameters of diastolic function in patients after AMI. However, this effect of BMC therapy decline over long-term follow-up of 5 years and is basically related to an early improvement of parameters of diastolic function at 6 and 18 months. A subgroup of patients with more transmural infarcts and no hypertension at baseline may derive a sustained benefit from BMC therapy. Future studies in this area may want to focus on patients with more substantial infarct damage (i.e. BOOST 2). Moreover, pharmacological and genetic strategies should be considered to enhance cell retention after intracoronary delivery and to improve the functionality of the cells.

Conflict of interest: none declared.

Funding

Institutional funding of the Clinic of Cardiology/Angiology, Hannover Medical School.

Footnotes

  • The first two authors contributed equally to the study.

References

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