A randomised trial of selective intracoronary hypothermia during primary PCI

BACKGROUND

While experimental data suggest that selective intracoronary hypothermia decreases infarct size, studies in patients with ST-elevation myocardial infarction (STEMI) are lacking.

AIMS

We investigated the efficacy of selective intracoronary hypothermia during primary percutaneous coronary intervention (PCI) to decrease infarct size in patients with STEMI.

METHODS

In this multicentre randomised controlled trial, 200 patients with large anterior wall STEMI were randomised 1:1 to selective intracoronary hypothermia during primary PCI or primary PCI alone. Using an over-the-wire balloon catheter for infusion of cold saline and a pressure-temperature wire to monitor the intracoronary temperature, the anterior myocardium distal to the occlusion was selectively cooled to 30-33°C for 7-10 minutes before reperfusion (occlusion phase), immediately followed by 10 minutes of cooling after reperfusion (reperfusion phase). The primary endpoint was infarct size as a percentage of left ventricular mass on cardiovascular magnetic resonance imaging after 3 months.

RESULTS

Selective intracoronary hypothermia was performed in 94/100 patients randomised to cooling. Distal coronary temperature decreased by 6°C within 43 seconds (interquartile range [IQR] 18-113). The median duration of the occlusion phase and reperfusion phase were 8.2 minutes (IQR 7.2-9.0) and 9.1 minutes (IQR 8.2-10.0), respectively. The infarct size at 3 months was 23.1±12.5% in the selective intracoronary hypothermia group and 21.6±12.2% in the primary PCI alone group (p=0.43). The left ventricular ejection fraction at 3 months in each group were 49.1±10.2% and 50.1±10.4%, respectively (p=0.53).

CONCLUSIONS

Selective intracoronary hypothermia during primary PCI in patients with anterior wall STEMI was feasible and safe but did not decrease infarct size compared with standard primary PCI. (ClinicalTrials.gov: NCT03447834).

A novel intracoronary hypothermia device reduces myocardial reperfusion injury in pigs

BACKGROUND

Hypothermia therapy has been suggested to attenuate myocardial necrosis; however, the clinical implementation as a valid therapeutic strategy has failed, and new approaches are needed to translate into clinical applications. This study aimed to assess the feasibility, safety, and efficacy of a novel selective intracoronary hypothermia (SICH) device in mitigating myocardial reperfusion injury.

METHODS

This study comprised two phases. The first phase of the SICH was performed in a normal porcine model for 30 minutes ( n = 5) to evaluate its feasibility. The second phase was conducted in a porcine myocardial infarction (MI) model of myocardial ischemia/reperfusion was performed by balloon occlusion of the left anterior descending coronary artery for 60 minutes and maintained for 42 days. Pigs in the hypothermia group ( n = 8) received hypothermia intervention onset reperfusion for 30 minutes and controls ( n = 8) received no intervention. All animals were followed for 42 days. Cardiac magnetic resonance analysis (5 and 42 days post-MI) and a series of biomarkers/histological studies were performed.

RESULTS

The average time to lower temperatures to a steady state was 4.8 ± 0.8 s. SICH had no impact on blood pressure or heart rate and was safely performed without complications by using a 3.9 F catheter. Interleukin-6 (IL-6), tumor necrosis factor-α, C-reactive protein (CRP), and brain natriuretic peptide (BNP) were lower at 60 min post perfusion in pigs that underwent SICH as compared with the control group. On day 5 post MI/R, edema, intramyocardial hemorrhage, and microvascular obstruction were reduced in the hypothermia group. On day 42 post MI/R, the infarct size, IL-6, CRP, BNP, and matrix metalloproteinase-9 were reduced, and the ejection fraction was improved in pigs that underwent SICH.

CONCLUSIONS

The SICH device safely and effectively reduced the infarct size and improved heart function in a pig model of MI/R. These beneficial effects indicate the clinical potential of SICH for treatment of myocardial reperfusion injury.

Investigation of the active ingredients of Shuangshen Ningxin Fomula and the mechanism underlying their protective effects against myocardial ischemia-reperfusion injury by mass spectrometric imaging

BACKGROUND

Traditional Chinese medicine, particularly Shuangshen Ningxin Capsule (SSNX), has been studied intensely. SSNX includes total ginseng saponins (from Panax ginseng Meyer), total phenolic acids from Salvia miltiorrhiza Bunge, and total alkaloids from Corydalis yanhusuo W. T. Wang. It has been suggested to protect against myocardial ischemia by a mechanism that has not been fully elucidated.

METHODS

The composition and content of SSNX were determined by UHPLC-Q-TOFQ-TOF / MS. Then, a rat model of myocardial ischemia-reperfusion injury was established, and the protective effect of SSNX was measured. The protective mechanism was investigated using spatial metabolomics.

RESULTS

We found that SSNX significantly improved left ventricular function and ameliorated pathological damages in rats with myocardial ischemia-reperfusion injury. Using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), the protective mechanism of SSNX was examined by comparing the monomer components of drugs targeted in myocardial tissue with the distribution of myocardial energy metabolism-related molecules and phospholipids. Interestingly, some lipids display inconsistent content distribution in the myocardial ischemia risk and non-risk zones. These discrepancies reflect the degree of myocardial injury in different regions.

CONCLUSION

These findings suggest that SSNX protects against myocardial ischemia-reperfusion injury by correcting abnormal myocardial energy metabolism, changing the levels and distribution patterns of phospholipids, and stabilizing the structure of the myocardial cell membrane. MALDI-TOF MS can detect the spatial distribution of small molecule metabolites in the myocardium and can be used in pharmacological research.

Therapeutic hypothermia for acute myocardial infarction: a narrative review of evidence from animal and clinical studies

Myocardial infarction (MI) is the leading cause of death from coronary heart disease and requires immediate reperfusion therapy with thrombolysis, primary percutaneous coronary intervention, or coronary artery bypass grafting. However, myocardial reperfusion therapy is often accompanied by cardiac ischemia/reperfusion (I/R) injury, which leads to myocardial injury with detrimental consequences. The causes of I/R injury are unclear, but are multifactorial, including free radicals, reactive oxygen species, calcium overload, mitochondria dysfunction, inflammation, and neutrophil-mediated vascular injury. Mild hypothermia has been introduced as one of the potential inhibitors of myocardial I/R injury. Although animal studies have demonstrated that mild hypothermia significantly reduces or delays I/R myocardium damage, human trials have not shown clinical benefits in acute MI (AMI). In addition, the practice of hypothermia treatment is increasing in various fields such as surgical anesthesia and intensive care units. Adequate sedation for anesthetic procedures and protection from body shivering has become essential during therapeutic hypothermia. Therefore, anesthesiologists should be aware of the effects of therapeutic hypothermia on the metabolism of anesthetic drugs. In this paper, we review the existing data on the use of therapeutic hypothermia for AMI in animal models and human clinical trials to better understand the discrepancy between perceived benefits in preclinical animal models and the absence thereof in clinical trials thus far.

Therapeutic Hypothermia in STEMI

In this review article we tried to find an answer to the question, should local coronary hypothermia be a part of the early reperfusion strategy in patients with STEMI to prevent reperfusion injury, no-reflow phenomenon, and to reduce the infarct size and mortality. Hypothermia can save cardiomyocytes if achieved in a timely fashion before reperfusion. Intracoronary hypothermia can be adjunct to PCI by lessening ischemia/reperfusion injury on cardiomyocytes and reduction in infarct size. Reperfusion induced Calcium overload, generation of ROS and subsequent activation of Mitochondrial permeability transition pore (MPT) are major contributors to reperfusion injury. Hypothermia reduces calcium loading of the cell and maintains cellular energy and tissue level glucose which can scavenger ROS. Hypothermia reduces MPT activation and thus reduces infarct size. Systemic cooling trials failed to reduce infarct size, perhaps because the target temperature was not reached fast enough, and it was associated with systemic side effects. The need for rapid induction of hypothermia to <35 °C with the ethical concern of delaying reperfusion while cooling the patient and the inconsistency of endovascular cooling results lead to a belief that endovascular cooling may exceed the acceptable level of invasiveness in the context of other novels cardioprotective, regenerative and reperfusion therapies. Clinical trials showed the safety and feasibility of novel intracoronary hypothermia with rapid induction and maintenance of hypothermia using routine PCI equipment ahead of reperfusion. Two phases of cooling were applied without significant delay in the door to balloon time. Cooling of the coronary artery leads to cooling of its dependant myocardium without affecting adjacent myocardium. Heat transfer occurred by heat conduction during the occlusion phase and heat convention during the reperfusion phase. Fine-tuning of saline temperature and infusion rate helped to improve the protocol. The best duration of hypothermia before and after reperfusion is not known and needs further investigation. A balance between the undoubted cardioprotective effects of hypothermia with iatrogenic prolongation of ischemia time needs to be established. A reduction in infarct size was observed but needs to be validated with large randomized trials. Furthermore, it might be possible to augment the cardioprotective effects of intracoronary hypothermia by combination with other cardioprotective approaches such as antioxidant drugs and afterload reducing agents.

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.

A pilot clinical study of adjunctive therapy with selective intracoronary hypothermia in patients with ST-segment elevation myocardial infarction

OBJECTIVES

We aimed to assess the effect of selective intracoronary hypothermia on outcomes in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI).

BACKGROUND

Intracoronary hypothermia, the feasibility and safety of which has been validated in humans, induced by selective trans-coronary infusion of saline at different temperatures can reduce infarct size (IS) prior to reperfusion in animal models of STEMI.

METHODS

Sixty STEMI patients presenting with thrombolysis in myocardial infarction (TIMI) flow grade 0/1 were randomized after coronary artery angiography. Intracoronary hypothermia was induced by selective trans-coronary infusion of saline at 4°C to the endangered myocardium in the 30 patients. The primary endpoint, absolute IS expressed as IS/myocardium at risk (MaR), was assessed by cardiac magnetic resonance imaging at day 7 post-PPCI in 50 patients. Clinical follow-up was undertaken at day 30 after procedure.

RESULTS

Intracoronary hypothermia was successfully performed in hypothermia group, without increase in arrhythmia or hemodynamic instability. The mean temperature reduction of 5.8 ± 1.1°C in distal coronary artery was achieved before reperfusion. Mean IS/MaR was predominantly reduced in the hypothermia group (44.85 ± 5.89% vs. 50.69 ± 10.75%, P = 0.022), especially in the anterior STEMI subgroup (46.12 ± 7.54% vs. 55.27 ± 11.175%, P = 0.023). The clinical events appeared no statistical difference between the two groups at the 30-day follow-up.

CONCLUSION

The statistical difference in IS/MaR by intracoronary hypothermia as adjunctive therapy to PPCI is an important observation and warrants a larger pivotal trial fully powered for efficacy.

A feasibility and safety study of intracoronary hemodilution during primary coronary angioplasty in order to reduce reperfusion injury in myocardial infarction

OBJECTIVES

We designed a pilot study to evaluate safety and feasibility of an inexpensive and simple approach to intracoronary hemodilution during primary angioplasty (PPCI) to reduce reperfusion injury.

INTRODUCTION

Early revascularization in acute myocardial infarction decreases infarct size and improves outcomes. However, abrupt restoration of coronary flow results in myocardial reperfusion injury and increased final infarct size. Dilution of coronary blood during revascularization may help reduce this damage. If proved effective, such an approach would need to be simple and suitable for widespread adoption.

METHODS

Ten patients presenting with STEMI underwent intracoronary dilution with room temperature Hartmann's solution delivered through the guiding catheter during primary angioplasty (PPCI). Infusion of perfusate began prior to crossing the occluded artery with the guidewire, continuing until 10 min after completion of the balloon and stenting procedure. Infusion was briefly interrupted for contrast injection and pressure monitoring. The outcome measures were safety, including intracoronary temperature reduction and volume of intracoronary perfusate infused, and technical feasibility.

RESULTS

There were no significant symptomatic, hemodynamic, ECG ST/T segment or rhythm changes observed during perfusate administration. The median (interquartile range) volume of perfusate administered was 550 mL (350-725 mL) and the median intracoronary temperature reduction observed was 3.4°Celsius. Myocardial salvage was 0.54 (0.43-0.65).

CONCLUSIONS

Transcatheter intracoronary hemodilution with room temperature perfusate during PPCI is feasible and appears safe. Such a strategy is simple and inexpensive, with potential to be widely applied. Further mechanistic and subsequent outcome powered studies are required to evaluate whether this strategy can reduce reperfusion injury in STEMI.