|Year : 2015 | Volume
| Issue : 6 | Page : 706-707
Ischemic time, infarct size and transmurality in acute ST-elevation myocardial infarction
A. K. M. Monwarul Islam
Department of Cardiology, Jessore Medical College, Jessore, Bangladesh
|Date of Web Publication||19-Nov-2015|
A. K. M. Monwarul Islam
Department of Cardiology, Jessore Medical College, Jessore 7400
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Islam AM. Ischemic time, infarct size and transmurality in acute ST-elevation myocardial infarction. Med J DY Patil Univ 2015;8:706-7
The outcome of acute ST-elevation myocardial infarction (STEMI) depends, to a large extent, on the size and transmurality of the infarct, which, in turn, depend on the artery involved, and the ischemic time to which the territory of the myocardium remain exposed. The present management strategy of acute STEMI directs at reducing the infarct size and transmurality by means of coronary revascularization as early as possible, largely on the principle "minute means muscle." The primary percutaneous coronary intervention (PCI) is the reperfusion strategy of choice. The latest ACC/AHA guideline for management of STEMI recommends the primary PCI as the triage strategy in all patients within 90 min of the first medical contact (FMC) in case of transfer to a PCI-capable hospital, and within 120 min of FMC for a non-PCI-capable center; the primary PCI is to be performed within up to 12 h of onset of the chest pain. 
At present, the reality is far from what is "ideal;" the primary PCI is still under-utilized even in the developed world, and the ischemic time is longer than what is recommended. To overcome these shortcomings, especially in the developed world, different measures have been taken, including the introduction of emergency medical services, arrangement for dedicated cardiac ambulances, and prehospital fibrinolysis followed by PCI. The time from onset of symptom to presentation at hospital is generally longer among the patients in India than in the West; 110-140 min in North America, while in India, it is 180-330 min.  This delay in the presentation is due to several factors, including lack of symptom awareness, longer distances traveled to reach the hospital and problems of transportation. The scenario is probably similar in other South Asian countries and the developing world as a whole. Despite the limitations, cardiac care facilities, especially coronary interventions, are increasing day by day in the Indian subcontinent. In India, as per National Interventional Council database, a total of 24,375 primary angioplasty procedures were performed in 2013 and 41,057 in 2014, indicating a 68% increase by just 1-year. In 2013, the primary PCI comprised 17% of all interventional procedures; door-to-balloon-time was 15-150 min, mean 45 min, indicating a considerable reduction of ischemic time. Hence, remarkable advances are in progress, in the care of STEMI patients in India.
In the present study, titled "Influence of time-to-treatment and other risk factors on infarct size and transmurality in case of STEMI managed by the primary angioplasty and assessed by delayed-enhancement magnetic resonance imaging," the authors have evaluated the effect of time-to-treatment and the risk factors such as diabetes mellitus, hypertension, smoking, family history of coronary artery disease, and obesity on infarct size, transmurality and ST-segment resolution in 50 patients with acute STEMI undergoing the primary PCI; the primary endpoint was final infarct size and transmurality as assessed by delayed-enhanced magnetic resonance imaging (DE-MRI) at 3 months follow-up. Infarct size and transmurality increased and ST-segment resolution decreased with increase in ischemic time. Diabetes mellitus, hypertension, smoking, and obesity did not affect immediate prognosis during treatment. The findings of the present study echo the findings of the previous studies demonstrating the relationship between the time delays before revascularization and the outcome of the primary PCI. ,,,, In De Luca's study  involving 1791 patients, after adjustment for age, gender, diabetes, and previous revascularization, each 30 min of delay was associated with a relative risk for 1-year mortality of 1.075 (95% confidence interval 1.008-1.15; P = 0.041). Studies based on MRI gave more attention on ischemic time, infarct size, and transmurality. Tarantini et al.  found a direct and continuous relationship between the ischemic time, transmural necrosis and severe microvascular obstruction (MVO) in contrast-enhanced MRI; each 30 min delay was associated with a 37% increase in the risk of transmural necrosis and 21% increase in the risk of severe MVO (n = 77). Myocardial salvage percentage was highest and infarct size was lowest when the time from symptom onset to PCI was <90 min in Francone's study (n = 70).  Likewise, myocardial salvage was highest when PCI was performed within 2 h of symptom onset in observation by Eitel et al. (n = 208); both the mortality and the major adverse cardiovascular events were significantly lower in early intervention group at 6-month follow-up (P < 0.001). 
The study endeavors demonstration of the impact of ischemic time on the outcome of the primary PCI in terms of infarct size and transmurality in acute STEMI in Indian context utilizing modern "state-of-the-art" modality, that is, DE-MRI. Larger studies should be carried out in future to revalidate the data of the present study. Furthermore, the other aspects of triage strategy such as the impact of prehospital fibrinolysis followed by PCI can be evaluated in future in a like manner.
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