Page 90 - Coronary hemodynamics in acute myocardial infarction - Matthijs Bax

Chapter 5
of hypoxic perfusion cannot be excluded, and may explain part of the increase in baseline flow velocity in the reference coronary artery because of a decrease in myocardial capacitance in this setting of anterior wall STEMI. Moreover, although we have no information on pre-existent microvascular dysfunction in our study population, pre-existent dysfunction would have accounted for a predominant decrease in baseline microvascular resistance. In accordance with previous reports,29,30 the combination of observations in the present study implies that reference vessel CFVR in the setting of STEMI summarizes a complicated interrelation between neurohumoral overactivation induced by the acute ischemic event, pre-existent microvascular dysfunction, or the acute regional and global mechanical myocardial disruption, but is predominantly determined by the neurohumoral overactivation, which accounts for an immediate high risk for fatal cardiac events.
Reference Vessel CFVR at 6-Month Follow-up and Long-term Cardiac Mortality
In contrast to the findings in the acute setting, we observed that an impaired reference vessel CFVR at 6-month follow-up originated from a persistently higher baseline APV in conjunction with a lower baseline microvascular resistance, in the presence of restored minimal hyperemic microvascular resistance. This may result from pre-existent microvascular dysfunction, as was found in patients with stable coronary artery disease and after PCI,45 or possibly from ongoing microvascular adaptation compensatory to the alterations in myocardial workload because of the loss of functioning myocardium, both of which may be responsible for a high risk for fatal cardiac events during subsequent follow-up.
Study Limitations
Assessment of intracoronary blood flow velocity is a technique that is sensitive for technical failures, and accurate evaluation of CFVR is dependent on the experience of the cardiologist. All coronary flow velocity measurements in this study were performed by operators with ample experience in intracoronary flow velocity measurements. Accurate assessment of flow velocity depends furthermore on the achievement of maximal vasodilation. Although there has been an extensive debate on the amount of adenosine needed to achieve a
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