A critical review of the efficacy and safety in the use of low-molecular-weight heparin in acute ST-elevation myocardial infarction: a Bayesan approach.

BACKGROUND: ST segment elevation myocardial infarction (STEMI) is an important risk factor of death worldwide. Significant clinical research has been done to assess ideal reperfusion strategies in the setting of STEMI, including the role of the antithrombin agents: unfractionated heparin (UFH) and low molecular weight heparin (LMWH). Given the evidence that LMWH may be safer than UFH in the treatment of other thrombotic disorders, its role in the management of STEMI needs to be more defined. OBJECTIVE: To assess the safety and efficacy of LMWH compared to UFH and/or placebo for the treatment of STEMI. MATERIALS AND METHODS: The Cochrane Library, MedLine and EMABASE databases were searched for randomized controlled trials pertinent to the study objective. Selection criteria included all randomized controlled trials comparing LMWH to either UFH or placebo in the treatment of STEMI through December 2010. Two Authors performed the search independently.After identifying appropriate studies, a random effect model and Bayesian sensitivity analysis were used to combine results from original trials and assess the consistency of results. RESULTS: We identified 13 studies that met the described selection criteria; 8 comparing LMWH to UFH and 5 to placebo in STEMI patients. The combined Odd's ratio was 0.79 with a 95% confidence interval of 0.67-0.94 for all studies and 0.74 (0.54-1.02) for those comparing LMWH to UFH only. A trend toward more frequent hemorrhagic events was identified in the LMWH group (Odd's ratio 1.40) which did not meet statistical significance (95% confidence interval 0.80-2.47). Sensitivity analysis demonstrated clinical benefits of 6% and 12.5% with probabilities of 99% and 95% respectively. CONCLUSION: Compared to placebo or UFH, LMWH is effective as a first line treatment of STEMI patient with no significant increase in major hemorrhagic events.

Heart rate variability and myocardial infarction: systematic literature review and metanalysis.

BACKGROUND: Heart rate, measured as beat-to-beat intervals, is not constant and varies in time. This property is known as heart rate variability (HRV) and it has been investigated in several diseases, including myocardial infarction (MI). The main hypothesis is that HRV embed some physiological processes that are characteristics of regulatory systems acting on cardiovascular system. It is possible to quantify such a complex behaviour starting from RR intervals properties itself with the idea that any event affecting the cardiac regulatory system significantly will disrupt and change HRV. In this article, we first review different methodologies previously published to calculate HRV indexes. We then searched literature for studies published on HRV and MI and we derive a metanalysis where published data allow calculation of composite outcomes. MATERIAL AND METHODS: Articles considered eligible for metanalysis were original retrospective/prospective studies investigating HRV after myocardial infarction, reporting follow up for mortality or significant cardiac complications. Random effect model was used to assessed for homogeneity and calculate composite outcome and its 95% confidence interval (CI). RESULTS: 21 studies were identified as eligible for subsequent analysis. Among these studies 5 large trials were eligible for metanalysis: "they included 3489 total post-MI patient with an overall mortality of 125/577 (21.7%) in patients with standard deviation of RR intervals (SDNN) less than 70 msec compared to 235/2912 (8.1%) in patients with SDNN > 70 msec". Metanalysis demonstrates that, after a MI, patients with SDNN below 70 msec on 24 hours ECG recording have almost 4 times more chance to die in the next 3 years. CONCLUSION: Results from metanalysis and other studies considered (but not included in the analysis) are consistent with the final finding, that a disrupted HRV dynamic (low SDNN) is associated with higher adverse outcome. In this perspective, although data are strongly positive for a direct relationship between SDNN and mortality after MI, SDNN value must be considered carefully on a single patient. The primary purpose of the metanalysis was to address whether studies conducted on HRV and MI were consistent rather than established a cut-off for SDNN. HRV is simple, non invasive and relatively not expensive to obtain.