The Relationship between Microcirculatory Resistance and Fractional Flow Reserve in Patients with Acute Myocardial Infarction

Different Microcirculation Response Between Culprit and Non-Culprit Vessels in Patients With Acute Coronary Syndrome

Background

This study investigated whether the microvascular dysfunction differed between culprit and non‐culprit vessels in patients with acute coronary syndrome who underwent percutaneous coronary intervention.

Methods and Results

In 115 prospectively recruited patients, after successful percutaneous coronary intervention, culprit and non‐culprit intracoronary hemodynamic measurements were performed and repeated at 6‐month follow‐up. ¹³N‐ammonia positron emission tomography was performed at 6‐month follow‐up visit to determine absolute myocardial blood flow. The resistance values of each vessel were calculated using the coronary pressure data and the myocardial blood flow values obtained from ¹³N‐ammonia positron emission tomography data. We compared the measurements between culprit and non‐culprit vessels and assessed changes in microvascular dysfunction during the study period. In 334 vessels (115 culprit and 219 non‐culprit), the culprit vessel group showed a lower fractional flow reserve and coronary flow reserve than the non‐culprit vessel group at baseline and 6‐month follow‐up, respectively. The value of index of microcirculatory resistance was different between the 2 groups in the baseline but not at 6‐month follow‐up. The microvascular resistance at rest and hyperemic microvascular resistance were not different between the 2 groups, but resistance to stenosis was higher in the culprit vessel group, under both resting and hyperemic status (P=0.02 and P<0.01, respectively). In the culprit vessel analysis, the fractional flow reserve and index of microcirculatory resistance decreased whereas coronary flow reserve increased (P<0.01 for all) at 6‐month follow‐up. However, there was no change in index of microcirculatory resistance, coronary flow reserve, and fractional flow reserve from baseline to 6‐month follow‐up in the non‐culprit vessel analysis.

Conclusions

The observed microvascular dysfunction in acute coronary syndrome is limited to the culprit vessel territory in the acute phase, which is relatively recovered in the chronic phase and there is no out‐of‐culprit territory involvement.

Registration

URL: https://www.clini​caltr​ials.gov; Unique identifier: NCT04169516.

Association between Cardiac Troponin Level and Coronary Flow Reserve in Patients without Coronary Artery Disease: Insight from a Thermodilution Technique Using an Intracoronary Pressure Wire

BACKGROUND AND OBJECTIVES

Cardiac troponins are associated with increased mortality, even among patients with no coronary artery disease. Elevated cardiac troponin levels are frequently observed in patients without significant coronary lesions, although the mechanism underlying this finding is unclear. The aim of our study was to evaluate the association between the levels of cardiac troponin and coronary flow reserve (CFR).

SUBJECTS AND METHODS

We evaluated serum cardiac troponin-I in 19 patients (9 female; age 61.9±10.9 year-old). All patients had an ejection fraction >40% and angiographically normal coronary arteries. Simultaneous measurements of fractional flow reserve (FFR), the index of microcirculatory resistance (IMR), and CFR measurements using an intracoronary temperature- and pressure-sensing guidewire under basal conditions and during maximal hyperemia were performed in three vessels: the left anterior descending artery (LAD), left circumflex artery (LCX) and right coronary artery (RCA).

RESULTS

All patients were followed for a median of 13 months. FFR, IMR, and CFR measurements were performed successfully in all subjects. Mean CFRs of LAD, LCX, and RCA were 1.98±1.20, 2.75±2.11, and 4.44±2.51, respectively. Mean IMRs of LAD, LCX and RCA were 33.28±18.78, 29.11±26.70, and 30.55±23.65, respectively. There was a poor correlation between CFR and troponin-I values in each vessel. In selecting the lowest value of CFR in each patient as the corresponding value, the lowest CFR was not associated with troponin-I levels (r=-0.219, p=0.367).

CONCLUSION

In patients without significant coronary lesions, the correlation between CFR and troponin-I level was not significant using a thermodilution technique. Further study of a larger population with longer-term follow-up may be needed to more fully understand microvascular dysfunction.