The impact of Vasopressin on coronary microcirculation in ST-elevation myocardial infarction

Abstract

Background: When treating patients with an acute myocardial infarction, the coronary microcirculation is an area that still eludes understanding. One suspected mechanism for microvascular dysfunction in this patient group is ongoing coronary vasoconstriction during reperfusion. Animal models suggest that Arginine Vasopressin (AVP) has a vasoactive effect on the coronary microcirculation. Aims: 1) To evaluate the blood levels of vasopressin in STEMI patients over the course of the myocardial infarction and during reperfusion. 2) To assess the impact of vasopressin on the coronary microcirculation in STEMI. Methods: Arterial blood samples were taken from patients admitted to the Freeman Hospital, Newcastle with an acute STEMI, who subsequently underwent PPCI, over the time course of reperfusion. Copeptin, a precursor of vasopressin was measured. Cardiac MRI was performed to evaluate microvascular obstruction, infarct size and ejection fraction. Index of Microvascular resistance (IMR) was performed to measure microvascular dysfunction. Results: In STEMI patients copeptin levels at baseline are markedly elevated (126.8 ± 13.94 pmol/l) with copeptin levels falling significantly by 90 minutes (86.15 ± 12.57 pmol/l) (p < 0.0001). Copeptin levels at 24 hours are significantly higher in patients where TIMI 3 flow was not achieved post PCI (<0.05). Copeptin levels were not related to the presence of microvascular obstruction or IMR, but higher copeptin levels resulted in significantly lower CFR (p <0.01). Higher copeptin levels at baseline and 30 mins post reperfusion were noted in patients with smaller infarctions (p <0.01). Conclusion: In STEMI patients, circulating copeptin is elevated over the course of reperfusion, with increased levels at 24 hours signifying poor reperfusion. Copeptin does not impact on the coronary microcirculation but does significantly affect the coronary flow after reperfusion. Higher copeptin levels at baseline suggest a cardioprotective element with smaller infarctions.