Cardiology · Medical Literature
Intracoronary stem cell transplant in ischemic heart disease: a meta-analysis of randomized trials.
Abstract
Ischemic heart disease is a leading cause of morbidity and mortality. In this study, we assessed the efficacy of intracoronary stem cell transplantation on left ventricular function (LVEF) in acute myocardial infarction, chronic ischemic heart disease, and severe ischemic heart failure. MATERIALS AND METHODS: We conducted a meta-analysis of randomized trials from 2002 to 2025. Mean difference in LVEF between treated and control patients at 6-months after infusion was calculated according to analysis of covariance. Heterogeneity among studies was assessed by the Cochrane's Q, Tau2, and I2 statistics. The primary outcome was the LVEF difference at follow-up. Secondary outcomes were comparisons among the type and number of transplanted stem cells. The analysis included 82 randomized controlled trials totaling 5,781 patients (3,048 treated and 2,733 controls) affected by acute myocardial infarction (AMI, n. 70), chronic ischemic heart disease (CIHD, n. 5), and ischemic heart failure (IHF, n. 7). Stem cells were bone marrow, mesenchymal, peripheral blood, and cardiac stem cells in 58, 15, 6 and 3 studies, respectively. Median infused cells were 100 x 106. LVEF increased 3.3% overall and 8.2%, 5.3% and 2.7% in CIHD, IHF and AMI, respectively. LVEF increased 2% per each 109 cells. CIHD improved from mild (46%) to normal (54%) and IHF from severe (30%) to moderate (38%) functional class. Study heterogeneity decreased over publication year, and there is evidence for publication bias, although the Egger's test resulted in a non-significant result. Intracoronary stem cells induced a significant decrease in mean New York Heart Association (NYHA) functional class from baseline to 6 and 12 months after transplant (2.6, 1.8, and 1.9, respectively; t-test p = 0.002) in ischemic heart failure patients. CONCLUSIONS: Intracoronary stem cell transplantation improves LVEF in acute and chronic ischemic heart disease and is associated with a reduction of functional class severity. The intracoronary route may be taken into consideration in future trials of stem cell therapy for ischemic heart disease due to its relative manageability and simplicity.
Clinical relevance
Does intracoronary stem cell transplantation improve left ventricular ejection fraction (LVEF) compared to control in patients with acute myocardial infarction, chronic ischemic heart disease, or ischemic heart failure, and does the magnitude of benefit vary by disease subtype, cell type, or cell dose? __SNAPSHOT__ {"studyDesign":"Systematic review with meta-analysis of randomized controlled trials (2002–2025); between-group LVEF difference analyzed by analysis of covariance (ANCOVA); heterogeneity assessed by Cochrane's Q, Tau², and I² statistics","setting":"Multi-national; 82 RCTs conducted across diverse international centers; specific institutional settings not reported at the aggregate level","sampleSize":"n = 5,781 (treated: 3,048; controls: 2,733) across 82 RCTs — AMI: 70 trials; CIHD: 5 trials; IHF: 7 trials","population":"Adult patients with acute myocardial infarction (AMI, n = 70 trials), chronic ischemic heart disease (CIHD, n = 5 trials), or ischemic heart failure (IHF, n = 7 trials); specific inclusion criteria (age range, baseline LVEF thresholds, prior revascularization requirements) not reported in the available abstract","intervention":"Intracoronary stem cell transplantation; cell types included bone marrow (58 studies), mesenchymal (15 studies), peripheral blood (6 studies), and cardiac stem cells (3 studies); median infused cell dose: 100 × 10⁶ cells","comparator":"Control group (specific nature — placebo infusion, standard of care, or sham procedure — not uniformly specified in the available abstract; varied across included trials)","primaryOutcome":"Mean difference in LVEF (%) between treated and control groups at 6 months post-infusion, calculated by ANCOVA","followUp":"Primary endpoint at 6 months; NYHA functional class also assessed at baseline, 6 months, and 12 months post-transplant","fundingSource":"Not reported"}
Key findings
Across 82 RCTs (n = 5,781), intracoronary stem cell transplantation was associated with a mean overall LVEF increase of 3.3 percentage points vs. control at 6 months. When stratified by disease subtype, the LVEF increase was 8.2% in chronic ischemic heart disease (CIHD), 5.3% in ischemic heart failure (IHF), and 2.7% in acute myocardial infarction (AMI) — with the AMI subgroup constituting the large majority of enrolled patients and trials. A dose-response relationship was observed, with LVEF increasing approximately 2 percentage points per 10⁹ cells infused. Functional class improvement was also reported: CIHD patients improved from mild (NYHA class corresponding to ~46% of patients) to normal (54%), and IHF patients improved from severe (30%) to moderate (38%) functional class. Mean NYHA class declined from 2.6 at baseline to 1.8 at 6 months and 1._ at 12 months (the 12-month value was truncated in the available abstract and is not reported). Confidence intervals, p-values, NNT, and absolute risk differences for any individual comparison were not reported in the available abstract. Study heterogeneity decreased over publication year. Publication bias was noted as a concern; however, Egger's test was non-significant. No specific safety data or adverse event rates are reported in the available abstract.
Practice implications
This meta-analysis of 82 RCTs offers the largest aggregate analysis to date of intracoronary stem cell therapy across the full ischemic heart disease spectrum. The overall 3.3-percentage-point mean LVEF improvement is statistically derived but of uncertain clinical significance: a minimum clinically important difference for LVEF is generally accepted as approximately 5 percentage points in heart failure populations, and the AMI subgroup — comprising 85% of trials — achieved only 2.7%, falling below this threshold. The larger benefits seen in CIHD (8.2%) and IHF (5.3%) are notable but are derived from far fewer trials (5 and 7, respectively) with substantially smaller patient numbers, limiting confidence in these estimates. The observed dose-response relationship (2% LVEF gain per 10⁹ cells) is hypothesis-generating but requires prospective validation. Critically, the study does not report hard clinical endpoints (mortality, major adverse cardiovascular events, rehospitalization) which are the outcomes of greatest relevance to contemporary cardiology practice. The field has been significantly confounded by publication bias, small-study effects, and methodological heterogeneity across component trials — limitations the authors acknowledge. The finding that heterogeneity decreased over publication year may reflect improved trial conduct over time or convergence around null results in later, larger, more rigorously blinded trials. Patients underrepresented include those with non-ischemic cardiomyopathy, preserved ejection fraction, and those already on contemporary guideline-directed medical therapy with SGLT2 inhibitors or GLP-1 agonists. Clinicians should not alter practice based solely on surrogate LVEF changes in the absence of demonstrated reduction in hard outcomes. NOTE: This summary is based solely on the published abstract; full-text data including forest plots, subgroup confidence intervals, risk-of-bias assessments, and adverse event tabulations were not available for review. __LIMITATIONS__ Evidence of publication bias acknowledged by authors, with potential overestimation of true effect size; Egger's test was non-significant but this test has limited power in large heterogeneous meta-analyses,Extreme heterogeneity in component trials: variability in stem cell type, preparation method, cell dose, timing of infusion relative to index event, concomitant pharmacotherapy, and LVEF measurement modality (echocardiography vs. MRI vs. nuclear imaging),Surrogate primary endpoint (LVEF change) without reported hard clinical outcomes (all-cause mortality, cardiovascular mortality, heart failure hospitalization, MACE),The CIHD and IHF subgroups are based on only 5 and 7 trials respectively — profoundly underpowered for reliable subgroup conclusions,Blinding integrity across component RCTs is variable; many earlier trials were open-label, introducing performance and detection bias,Individual patient-level data were not used; aggregate ANCOVA approach limits adjustment for baseline imbalances across heterogeneous trial populations,Confidence intervals and p-values for individual subgroup comparisons, cell-type analyses, and dose-response analyses are not reported in the available abstract,NYHA class data at 12 months appears incompletely reported in the abstract, limiting interpretation of functional durability,Funding source not reported; potential conflicts of interest for included trials not addressed in the available abstract,Only abstract available for this summary — full risk-of-bias assessments, sensitivity analyses, and adverse event data could not be independently verified __BOTTOM_LINE_CATEGORY__ promising_but_preliminary __BOTTOM_LINE__ This large meta-analysis of 82 RCTs found a statistically detectable but modest overall LVEF improvement of 3.3 percentage points with intracoronary stem cell therapy, with potentially larger benefits in CIHD and IHF subgroups; however, confidence intervals and hard clinical endpoints are not reported, and publication bias remains a substantive concern. The AMI subgroup — the most heavily populated — showed only a 2.7% LVEF gain, which is unlikely to reach the threshold of clinical meaningfulness. Intracoronary stem cell therapy should not be adopted into routine clinical practice on the basis of surrogate LVEF data alone; confirmation via adequately powered, blinded RCTs with hard outcome endpoints is required.