Post-Conditioning Decreases Infarct Size, Edema after Reperfusion Therapy for STEMI

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In patients receiving percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI), post-conditioning therapy reduces infarct size and edema by one-third compared with controls, according to a small study published in the June 12, 2012, issue of the Journal of the American College of Cardiology.

From May 2008 to October 2012, Franck Thuny, MD, PhD, of the University of Lyon (Lyon, France), and colleagues randomly assigned 50 patients undergoing primary PCI for STEMI to either a control group or to post-conditioning therapy, in which the angioplasty balloon was reinflated 4 times in 1-minute intervals. Within 48 to 72 hours of admission, cardiac MRI was performed in all patients.

Reduced Infarct Size, Edema

Patients who underwent post-conditioning had smaller average infarct size as measured by both late gadolinium enhancement (LGE; 38% difference) and peak serum creatine kinase (CK) release compared with controls. Post-conditioning patients also saw a 32% lower mean extent of myocardial edema, with a significant T2-weighted signal difference between the edema area (58%) and remote area (82%; P = 0.02; table 1).

Table 1. Effect of Post-Conditioning on Infarct Size, Edema Post-Reperfusion

The effect of post-conditioning on edema after reperfusion was dependent on the infarct size (P = 0.35 after correction for infarct size).

Jury Still Out

Although the results of the study are positive, Giuseppe Tarantini, MD, PhD, of the University of Padua (Padua, Italy), told TCTMD in an e-mail communication that it remains difficult to draw any definitive conclusions from studies looking at post-conditioning.

Dr. Tarantini pointed out that given the variety of previous results regarding post-conditioning, the therapy is unlikely to change clinical practice any time soon, especially since all of the studies have had a wide spectrum of inclusion and exclusion criteria as well as infarct size evaluation techniques.

“I believe that the major limitation around post-conditioning is the extreme complexity of the numerous physiological and biochemical mechanisms responsible for the beneficial effects of post-conditioning in experimental models,” Dr. Tarantini said.

Specifically, he emphasized that the translation of experimental studies to the clinical setting is complicated “by the fact that the optimal window for coupling of post-conditioning to beneficial responses may be substantially shorter than the mean duration of ischemia in typical STEMI patients.”

Mechanism of Action Unknown

Study co-author Michel Ovize, MD, PhD, of CIC de Lyon (Lyon, France), told TCTMD in an e-mail communication that while the inconsistency of studies testing post-conditioning to date may be due to the variability of study designs, a general lack of understanding surrounding the mechanism of protection may also be to blame.

“[The mechanism] might involve the inhibition of the opening of the mitochrondrial permeability transition pore, which has been shown to be involved in cardiomyocyte death at the time of reperfusion,” he said.

Dr. Tarantini agreed that previous conflicting results call attention to the need for better understanding of the mechanisms behind post-conditioning and the potential conditions under which it may benefit STEMI patients.

However, as the cardiology community learns more about post-conditioning, Dr. Ovize is confident that it will align well with other methods of STEMI care.

“Angioplasty post-conditioning is one typical technique to fight lethal myocardial reperfusion injury, and one may also use pharmacological post-conditioning, for example cyclosporine,” Dr. Ovize concluded. “Whatever the type of post-conditioning intervention, it goes along very well with the usual care for STEMI patients.”

Study Details

There were no significant differences in baseline characteristics, ischemic time, size of the area at risk, or the ejection fraction between the 2 groups.

 

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Source:
Thuny F, Lairez O, Roubille F, et al. Post-conditioning reduces infarct size and edema in patients with ST-segment elevation myocardial infarction. J Am Coll Cardiol. 2012;59:2175-2181.

 

 

Related Stories:

• Postconditioning Again Fails to Reduce Reperfusion Injury After STEMI
• `Direct` Postconditioning Reduces Infarct Size After Primary PCI for STEMI

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