Measurement of Myocardial Fractional Flow Reserve
Myocardial fractional flow reserve (FFRmyo) has been demonstrated to be a useful method for determining the physiologic importance of a given coronary lesion. However, the reliability of the FFRmyo measurement is unknown in infarct-related arteries (IRA). The aim of this study was to measure and correlate the FFRmyo results of 14 consecutive patients who had recent acute myocardial infarction (AMI) (Group 1) with 14 consecutive patients who didn't have AMI (Group 2) before and after percutaneous transluminal coronary angioplasty (PTCA). Quantitative coronary angiography (QCA) and FFRmyo measurements were determined both before and after optimal PTCA for all patients. FFRmyo was measured by use of a 0.014 inch guidewire as the ratio of the pressure distal to the target lesion to the aortic pressure taken during the maximal hyperemia induced by intracoronary adenosine. There were no differences between the two groups related to gender, target artery reference diameter, minimal luminal diameter and percent diameter stenosis of the vessel both before and after PTCA. While FFRmyo results after PTCA were not different between the groups, they were statistically different before PTCA (Group 1: 77.6 ± 5.4%, Group 2: 63.3 ± 8.4%; p < 0.001). Although QCA-determined percent diameter stenosis revealed a significant degree of stenosis (66.5 ± 10.5%) for Group 1, FFRmyo values were higher than 75% (77.6 ± 5.4%), indicating insignificant stenosis. Thus, it was concluded that FFRmyo measurements before PTCA were significantly different between IRA and non-IRA and that the method may not be valid for the determination of stenosis significance in IRA.
Coronary-pressure derived myocardial fractional flow reserve (FFRmyo) has emerged as a reliable index of the functional severity of an epicardial coronary stenosis. Previous studies attempting to determine the reliability and validity of this index have not included patients with previous acute myocardial infarction (AMI). Prolonged coronary artery occlusion due to acute thrombosis, in addition to myocardial necrosis, can result in damage of the microvasculature in the correspondent territory. Microvessel dysfunction due to previous MI may interfere with measurements of FFRmyo in the infarct-related artery (IRA). In the absence of microvessel dysfunction of any etiology, computation of less than 0.75 FFRmyo value could reliably separate ischemia with 95% sensitivity. Few data have accumulated so far as to whether to apply this cutoff value to the measurements of FFRmyo in the infarct-related coronary artery.
Theoretically, it can be suggested that in the presence of microvascular dysfunction, drugs which induce hyperemia would not reduce coronary resistance efficiently, and hyperemic distal pressure would be over-measured with the resultant high FFRmyo value. Recently, Takeuchi and colleagues have reported that FFRmyo could also be useful in predicting functional significance of coronary stenosis in the presence of resistance vessel dysfunction due to previous AMI. However, in that study, mean distal coronary pressure was measured by a 2.1 French (Fr) infusion catheter, which is known to be more prone to errors due to its size.
This study aims to calculate FFRmyo during coronary angioplasty in vessels with and without myocardial infarction by using a 0.014 inch pressure guidewire.
Myocardial fractional flow reserve (FFRmyo) has been demonstrated to be a useful method for determining the physiologic importance of a given coronary lesion. However, the reliability of the FFRmyo measurement is unknown in infarct-related arteries (IRA). The aim of this study was to measure and correlate the FFRmyo results of 14 consecutive patients who had recent acute myocardial infarction (AMI) (Group 1) with 14 consecutive patients who didn't have AMI (Group 2) before and after percutaneous transluminal coronary angioplasty (PTCA). Quantitative coronary angiography (QCA) and FFRmyo measurements were determined both before and after optimal PTCA for all patients. FFRmyo was measured by use of a 0.014 inch guidewire as the ratio of the pressure distal to the target lesion to the aortic pressure taken during the maximal hyperemia induced by intracoronary adenosine. There were no differences between the two groups related to gender, target artery reference diameter, minimal luminal diameter and percent diameter stenosis of the vessel both before and after PTCA. While FFRmyo results after PTCA were not different between the groups, they were statistically different before PTCA (Group 1: 77.6 ± 5.4%, Group 2: 63.3 ± 8.4%; p < 0.001). Although QCA-determined percent diameter stenosis revealed a significant degree of stenosis (66.5 ± 10.5%) for Group 1, FFRmyo values were higher than 75% (77.6 ± 5.4%), indicating insignificant stenosis. Thus, it was concluded that FFRmyo measurements before PTCA were significantly different between IRA and non-IRA and that the method may not be valid for the determination of stenosis significance in IRA.
Coronary-pressure derived myocardial fractional flow reserve (FFRmyo) has emerged as a reliable index of the functional severity of an epicardial coronary stenosis. Previous studies attempting to determine the reliability and validity of this index have not included patients with previous acute myocardial infarction (AMI). Prolonged coronary artery occlusion due to acute thrombosis, in addition to myocardial necrosis, can result in damage of the microvasculature in the correspondent territory. Microvessel dysfunction due to previous MI may interfere with measurements of FFRmyo in the infarct-related artery (IRA). In the absence of microvessel dysfunction of any etiology, computation of less than 0.75 FFRmyo value could reliably separate ischemia with 95% sensitivity. Few data have accumulated so far as to whether to apply this cutoff value to the measurements of FFRmyo in the infarct-related coronary artery.
Theoretically, it can be suggested that in the presence of microvascular dysfunction, drugs which induce hyperemia would not reduce coronary resistance efficiently, and hyperemic distal pressure would be over-measured with the resultant high FFRmyo value. Recently, Takeuchi and colleagues have reported that FFRmyo could also be useful in predicting functional significance of coronary stenosis in the presence of resistance vessel dysfunction due to previous AMI. However, in that study, mean distal coronary pressure was measured by a 2.1 French (Fr) infusion catheter, which is known to be more prone to errors due to its size.
This study aims to calculate FFRmyo during coronary angioplasty in vessels with and without myocardial infarction by using a 0.014 inch pressure guidewire.
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