In an era of rapid STEMI reperfusion with Primary Percutaneous Coronary Intervention is there a role for adjunct therapeutic hypothermia? A structured literature review

Efficacy and Safety of Therapeutic Hypothermia as an Adjuvant Therapy for Percutaneous Coronary Intervention in Acute Myocardial Infarction: A Systematic Review and Meta-Analysis

The study aims to compare the use of hypothermia in patients with myocardial infarction (MI) undergoing percutaneous coronary intervention (PCI) with control. We systematically searched four electronic databases until March 2022. The inclusion criteria were any study design that compared hypothermia in patients with MI undergoing PCI with control. The risk of bias assessment of the included randomized controlled trials was conducted through Cochrane Tool, while the quality of the included cohort studies was assessed by the NIH tool. The meta-analysis was performed on RevMan. A total of 19 studies were entered. Regarding the mortality, there were nonsignificant differences between hypothermia and control (odds ratio [OR] = 1.06, 95% confidence interval [CI] 0.75 to 1.50, p = 0.73). There was also no significant difference between the control and hypothermia in recurrent MI (OR = 1.21, 95% CI 0.64 to 2.30, p = 0.56). On the other hand, the analysis showed a significant favor for hypothermia over the control infarct size (mean difference = -1.76, 95% CI -3.04 to -0.47, p = 0.007), but a significant favor for the control over hypothermia in the overall bleeding complications (OR = 1.88, 95% CI 1.11 to 3.18, p = 0.02). Compared with the control, hypothermia reduced the infarct size of the heart, but this finding was not consistent across studies. However, the control had lower rates of bleeding problems. The other outcomes, such as death and the incidence of recurrent MI, were similar between the two groups.

Hypothermia in patients with acute myocardial infarction: a meta-analysis of randomized trials

BACKGROUND

In patients with acute myocardial infarction (MI) receiving percutaneous coronary intervention (PCI), the role of systemic therapeutic hypothermia remains controversial. We sought to investigate the role of systemic therapeutic hypothermia versus standard of care in patients with acute MI treated with PCI.

METHODS

This is a study-level meta-analysis of randomized trials. The primary outcome was all-cause death. The main secondary outcome was infarct size. Other secondary outcomes were recurrent MI, ischemia-driven target vessel revascularization (TVR), major adverse cardiovascular events, and bleeding.

RESULTS

A total of 1012 patients with acute MI receiving a PCI in nine trials (503 randomly assigned to hypothermia and 509 to control) were available for the quantitative synthesis. The weighted median follow-up was 30 days. As compared to controls, patients assigned to hypothermia had similar risk of all-cause death (risk ratio, [95% confidence intervals], 1.25 [0.80; 1.95], p = 0.32), with a trend toward higher risk of ischemia-driven TVR (3.55 [0.80; 15.87], p = 0.09) mostly due to acute or subacute stent thrombosis. Although in the overall cohort, infarct size was comparable between groups (standardized mean difference [95% Confidence intervals], 0.06 [- 0.92; 1.04], p = 0.92), patients effectively achieving the protocol-defined target temperature in the hypothermia group had smaller infarct size as compared to controls (p for interaction = 0.016). Treatment strategies did not differ with respect to the other outcomes.

CONCLUSIONS

As compared to standard of care, systemic therapeutic hypothermia in acute MI patients treated with PCI provided similar mortality with a signal toward more frequent repeat revascularization. Among patients assigned to hypothermia, those effectively achieving the protocol-defined target temperature displayed smaller infarct size.

TRIAL REGISTRATION

PROSPERO, CRD42019138754.

Myocardial tissue salvage is correlated with ischemic border region temperature at reperfusion

OBJECTIVES

Our pilot study investigated the association between region-specific myocardial tissue temperature and tissue salvage using a novel tri-lumen cooling catheter to provide rapid localized cooling directly to the heart in an open-chest porcine model of ischemia-reperfusion.

BACKGROUND

Therapeutic hypothermia remains a promising strategy to limit reperfusion injury following myocardial ischemia.

METHODS

Large swine underwent 60 min of coronary occlusion followed by 3 hr of reperfusion. Prior to inducing ischemia, six temperature probes were placed directly on the heart, monitoring myocardial temperatures in different locations. Hemodynamic parameters and core temperature were also collected. Approximately 15 min prior to reperfusion, the cooling catheter was inserted via femoral artery and the distal tip advanced proximal to the occluded coronary vessel under fluoroscopic guidance. Autologous blood was pulled from the animal via femoral sheath and delivered through the central lumen of the cooling catheter, delivering at 50 ml/min, 27°C at the distal tip. Cooling was continued for an additional 25 min after reperfusion followed by a 5-min controlled rewarming. Hearts were excised and assessed for infarct size per area at risk.

RESULTS

Although cooling catheter performance was consistent throughout the study (38 W), the resulting tissue cooling was not. Our results show a correlation between myocardial tissue salvage and ischemic border region (IBR) temperature at the time of reperfusion (R² = 0.59, p = 0.027). IBR tissue is the tissue located at the boundary between healthy and ischemic tissues.

CONCLUSIONS

Our findings suggest that localized, rapid, short-term myocardial tissue cooling has the potential to limit reperfusion injury in humans.