T wave alternans in experimental myocardial infarction: Time course and predictive value for the assessment of myocardial damage
Section snippets
Background
T-wave alternans (TWA), an ECG phenomenon reflecting spatiotemporal heterogeneity of repolarization, is known to be associated with the ventricular vulnerability and risk of death in different categories of patients, particularly in post-myocardial infarction (MI) patients.1, 2, 3 The negative association between the presence of TWA and ejection fraction has been reported in post MI patients.4 It was supposed that larger infarcts resulted in low ejection fraction and discordant alternans due to
Experimental protocol
A porcine model of myocardial infarction was used in this work. The experimental preparation, study protocol and imaging technique were previously described in detail.7 In brief, in pigs weighing 40–50 kg, anaesthetised with fentanyl and thiopental, an angioplasty balloon was positioned in the mid portion of the left anterior descending coronary artery (LAD), immediately distal to the first diagonal branch. Twelve-lead ECG monitoring ((“Kardiotechnica-04-8 m”, Incart, St. Petersburg, Russia) with
Results
Twenty three experimental animals comprised the study group. One pig was lost due to unsuccessful resuscitation after ventricular fibrillation during the occlusion period. In one more animal, TWA could not been assessed due to a poor signal quality. TWA was therefore calculated in 21 pigs. Indexes of myocardial damage could not be measured in three more pigs, which had died during reperfusion period from resistant VF or electromechanical dissociation. Thus data on MaR, IS and TWA were available
Discussion
We performed quantitative TWA-assessement in the settings of complete and prolonged coronary occlusion, resulting in acute ischemia followed by myocardial necrosis. In earlier studies on TWA caused by ischemia, TWA was observed during exercise stress-test,15 accompanied ST elevation in patients with Prinzmetal's angina16 and transitory occlusion of coronary artery during PCI.17, 18 In our study, TWA occurrence was markedly higher (93%) than in studies with even prolonged occlusion during PCI
Conclusion
In experimental myocardial infarction induced by LAD occlusion, the maximal level of TWA during occlusion period was associated with both MaR and IS, which further supports the need for evaluation of TWA in clinical settings for assessment of its prognostic value in patients with acute coronary syndrome.
Acknowledgments
This study was supported by donation funds from The Swedish Heart-Lung Fondation; The Swedish Institute; from Spanish Government (MINECO), and UE (FEDER) under project TEC2010-21703-C03-02; and from European Social Fund and Aragon Government (T30). The CIBER-BBN, is financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund (Spain).
Authors gratefully acknowledge valuable contribution of the imaging research group at the Department of Clinical
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