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Open Heart. 2016 Dec 12;3(2):e000535. doi: 10.1136/openhrt-2016-000535. eCollection 2016.

Impact of microvascular obstruction on semiautomated techniques for quantifying acute and chronic myocardial infarction by cardiovascular magnetic resonance.

Author information

1
The Hatter Cardiovascular Institute, Institute of Cardiovascular Science, University College London, London, UK; The National Institute of Health Research University College London Hospitals Biomedical Research Centre, London, UK; Cardiovascular and Metabolic Disorders Program, Duke-National University of Singapore, Singapore, Singapore; National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore.
2
Barts Heart Centre, St Bartholomew's Hospital , London , UK.
3
The National Institute of Health Research University College London Hospitals Biomedical Research Centre, London, UK; National Amyloidosis Centre, University College London, Royal Free Hospital, London, UK.
4
The Hatter Cardiovascular Institute, Institute of Cardiovascular Science, University College London , London , UK.
5
The National Institute of Health Research University College London Hospitals Biomedical Research Centre, London, UK; Barts Heart Centre, St Bartholomew's Hospital, London, UK.

Abstract

AIMS:

The four most promising semiautomated techniques (5-SD, 6-SD, Otsu and the full width half maximum (FWHM)) were compared in paired acute and follow-up cardiovascular magnetic resonance (CMR), taking into account the impact of microvascular obstruction (MVO) and using automated extracellular volume fraction (ECV) maps for reference. Furthermore, their performances on the acute scan were compared against manual myocardial infarct (MI) size to predict adverse left ventricular (LV) remodelling (≥20% increase in end-diastolic volume).

METHODS:

40 patients with reperfused ST segment elevation myocardial infarction (STEMI) with a paired acute (4±2 days) and follow-up CMR scan (5±2 months) were recruited prospectively. All CMR analysis was performed on CVI42.

RESULTS:

Using manual MI size as the reference standard, 6-SD accurately quantified acute (24.9±14.0%LV, p=0.81, no bias) and chronic MI size (17.2±9.7%LV, p=0.88, no bias). The performance of FWHM for acute MI size was affected by the acquisition sequence used. Furthermore, FWHM underestimated chronic MI size in those with previous MVO due to the significantly higher ECV in the MI core on the follow-up scans previously occupied by MVO (82 (75-88)% vs 62 (51-68)%, p<0.001). 5-SD and Otsu were precise but overestimated acute and chronic MI size. All techniques were performed with high diagnostic accuracy and equally well to predict adverse LV remodelling.

CONCLUSIONS:

6-SD was the most accurate for acute and chronic MI size and should be the preferred semiautomatic technique in randomised controlled trials. However, 5-SD, FWHM and Otsu could also be used when precise MI size quantification may be adequate (eg, observational studies).

KEYWORDS:

Infarct size; Microvascular obstruction; Myocardial infarction; cardiovascular magnetic resonance; extracellular volume fraction

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