Collaterals to occluded coronary arteries have been observed early after the onset of acute myocardial infarction (AMI). The pressure distal to the occluded segment of the culprit coronary artery (P(d)) is generated by collateral flow from the feeding coronary artery supplied by the systemic circulation. The aim of the study was to assess the relation between systemic blood pressure (BP) and P(d). Systemic BP and P(d) were measured simultaneously during intervention of totally occluded coronary arteries in 152 patients admitted for AMI. Patients were divided into groups by time from symptom onset to P(d) measurement. There was a significant positive correlation between P(d) and the systolic, diastolic, and mean BPs measured during the first 3 hours from symptom onset (n = 60; p <0.05, p <0.006, and p <0.005, respectively), from 3 to 12 hours (n = 56; p <0.02 for all), and >12 hours after symptom onset (n = 36; p <0.003 for all). The collateral flow, represented by calculated collateral flow index (mean 0.37 ± 0.14, median 0.36), was correlated with mean BP (p = 0.05) but not with diastolic or systolic BP (p = NS) in the overall study population. A direct relation was established during AMI between systemic BP and P(d) at all time intervals from symptom onset. Collateral flow index correlated with mean BP and was strongly associated with P(d) at all time intervals. In conclusion, the relation between P(d) and systemic BP suggests caution when administering therapy that may lower systemic BP during AMI before restoring flow in the occluded culprit artery, as it may compromise collateral pressure and exacerbate myocardial ischemia.
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