Elsevier

American Heart Journal

Volume 164, Issue 4, October 2012, Pages 538-546
American Heart Journal

Clinical Investigation
Congestive Heart Failure
Impact of system delay on infarct size, myocardial salvage index, and left ventricular function in patients with ST-segment elevation myocardial infarction

https://doi.org/10.1016/j.ahj.2012.07.021Get rights and content

Background

The association between reperfusion delay and myocardial damage has previously been assessed by evaluation of the duration from symptom onset to invasive treatment, but results have been conflicting. System delay defined as the duration from first medical contact to first balloon dilatation is less prone to bias and is also modifiable. The purpose was to evaluate the impact of system delay on myocardial salvage index (MSI) and infarct size in patients with ST-elevation myocardial infarction treated with primary percutaneous coronary intervention (PCI).

Methods

In patients with ST-elevation myocardial infarction, MSI and final infarct size were assessed using cardiovascular magnetic resonance. Myocardial area at risk was measured within 1 to 7 days, and final infarct size was measured 90 ± 21 days after intervention. Patients were grouped according to system delay (0 to 120, 121 to 180, and >180 minutes).

Results

In 219 patients, shorter system delay was associated with a smaller infarct size (8% [interquartile range 4-12%], 10% [6-16%], and 13% [8-17%]; P < .001) and larger MSI (0.77 [interquartile range 0.66-0.86], 0.72 [0.59-0.80], and 0.68 [0.64-0.72]; P = .005) for a system delay of up to 120, 121 to 180, and >180 minutes, respectively. A short system delay as a continuous variable independently predicted a smaller infarct size (r = 0.30, P < .001) and larger MSI (r = −0.25, P < .001) in multivariable linear regression analyses. Finally, shorter system delay (0-120 minutes) was associated with improved function (P = .019) and volumes of left ventricle (P = .022).

Conclusions

A shorter system delay resulted in smaller infarct size, larger MSI, and improved LV function in patients treated with primary PCI. Thus, this study confirms that minimizing system delay is crucial for primary PCI-related benefits.

Section snippets

Study population

The patients in the present substudy participated in a randomized study comparing intravenous administration of exenatide with placebo in patients with STEMI.24 In that previous study, patients with STEMI were randomized to receive either exenatide or placebo saline intravenously 15 minutes before intervention. This treatment resulted in increased myocardial salvage index in the exenatide group (for more details, see Ref. [24]). The patients were randomized before angiography, and some

Results

In a total of 219 patients with STEMI infarct size measured by CMR, system and prehospital delay times were available (Figure 2). Area at risk could not be measured in 26 patients; thus myocardial salvage index was available in 193 patients (Figure 2). The baseline characteristic of the study population is shown in Table I. Unfortunately, because of logistics and clinical condition, it was not possible to perform a CMR in all patients within 1 week. Eighty-four percent of the patients had their

Discussion

The main finding of our study was an independent association of both system- and prehospital delay with myocardial salvage index and infarct size. In particular, system delay of <121 minutes was associated with reduced myocardial damage and improved LV function. Thus, larger myocardial damage may partly explain the previously observed association between longer system delay and increased mortality.19

The benefit in terms of myocardial salvage and infarct size with early reperfusion therapy has

Conclusions

A shorter system delay resulted in smaller infarct size, larger myocardial salvage index, and improved LV function in patients treated with primary PCI. Thus, this study confirms that minimizing system delay is crucial for primary PCI–related benefits.

Acknowledgements

We thank research study nurses Lene Kløvgaard, Bettina Løjmand, and Bente Andersen, and the entire staff of the Department of Cardiology at Copenhagen University Hospital, Rigshospitalet, for skilful assistance.

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