Discrepancy between plaque vulnerability and functional severity of angiographically intermediate coronary artery lesions

Relation of Thrombolysis in Myocardial Infarction Frame Count to Invasively Measured Coronary Physiologic Indexes

In the international guidelines, higher thrombolysis in myocardial infarction frame count (TFC) is indicated as evidence of coronary microvascular dysfunction (CMD). However, the association of TFC with invasively measured coronary physiologic parameters such as coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) remains unclear. Patients without significant epicardial coronary lesions underwent invasive coronary physiologic assessment using a thermodilution method in the left anterior descending artery. Corrected TFC (cTFC) was evaluated on coronary angiography. The cut-off values of CFR and IMR were defined as ≤2.0 and >25, and patients with abnormal CFR and/or IMR were defined as having CMD. This study aimed to assess whether cTFC >25, a cut-off value in the guidelines, was diagnostic of the presence of CMD. Of the 137 patients, 34 (24.8%) and 32 (23.3%) had cTFC >25 and CMD, respectively. The rate of CMD was not significantly different between patients with and without cTFC >25. cTFC was weakly correlated with at rest and hyperemic mean transit time and IMR, whereas no significant correlation was observed between cTFC and CFR. The receiver operating characteristic curve analysis showed the poor diagnostic ability of cTFC for abnormal CFR and IMR and the presence of CMD. In conclusion, in patients without epicardial coronary lesions, cTFC as a continuous value and with the cut-off value of 25 was not diagnostic of abnormal CFR and IMR and the presence of CMD. Our results did not support the use of cTFC in CMD evaluation.

Thrombolysis in Myocardial Infarction Frame Count for Coronary Blood Flow Evaluation during Interventional Diagnostic Procedures

Background and Objectives: An interventional diagnostic procedure (IDP), including intracoronary acetylcholine (ACh) provocation and coronary physiological testing, is recommended as an invasive diagnostic standard for patients suspected of ischemia with no obstructive coronary arteries (INOCA). Recent guidelines suggest Thrombolysis In Myocardial Infarction frame count (TFC) as an alternative to wire-based coronary physiological indices for diagnosing coronary microvascular dysfunction. We evaluated trajectories of TFC during IDP and the impact of ACh provocation on TFC. Materials and Methods: This was a single-center, retrospective study. Patients who underwent IDP to diagnose INOCA were included and divided into two groups according to the positive or negative ACh provocation test. Wire-based invasive physiological assessment was preceded by ACh provocation tests and intracoronary isosorbide dinitrate (ISDN). We evaluated TFC at three different time points during IDP; pre-ACh, post-ISDN, and post-hyperemia. Results: Of 104 patients, 58 (55.8%) had positive ACh provocation test. In the positive ACh group, resting mean transit time (Tmn) and baseline resistance index were significantly higher than in the negative ACh group. Post-ISDN TFC was significantly correlated with resting Tmn (r = 0.31, p = 0.002). Absolute TFC values were highest at pre-ACh, followed by post-ISDN and post-hyperemia in both groups. All between-time point differences in TFC were statistically significant in both groups, except for the change from pre-ACh to post-ISDN in the positive ACh group. Conclusions: In patients suspected of INOCA, TFC was modestly correlated with Tmn, a surrogate of coronary blood flow. The positive ACh provocation test influenced coronary blood flow assessment during IDP.

Impact of preceding acetylcholine provocation testing on following coronary physiological assessment during an interventional diagnostic procedure

BACKGROUND

Intracoronary acetylcholine (ACh) provocation test and coronary physiological assessment are useful interventional diagnostic procedures for evaluating ischemia with no obstructive coronary arteries (INOCA). However, the appropriate sequential order of the diagnostic procedures has been a matter of debate. We investigated the impact of preceding ACh provocation on following coronary physiological assessment.

METHODS

Patients suspected of INOCA underwent invasive coronary physiological assessment using thermodilution method and were divided into two groups according to the implementation of ACh provocation test. The ACh group was further divided into the positive and negative ACh groups. In the ACh group, intracoronary ACh provocation was performed before the invasive coronary physiological assessment. The main interest of this study was to compare coronary physiological indices among the no ACh, negative ACh, and positive ACh groups.

RESULTS

Of 120 patients, the no ACh, and negative and positive ACh groups included 46 (38.3 %), 36 (30.0 %), and 38 (31.7 %), respectively. Fractional flow reserve was lower in the no ACh group than in the ACh group. Resting mean transit time was significantly longer in the positive ACh group, followed by the no ACh and negative ACh groups (1.22 ± 0.55 vs. 1.00 ± 0.46 vs. 0.74 ± 0.36 s, p < 0.001). Index of microcirculatory resistance and coronary flow reserve did not differ significantly among the three groups.

CONCLUSIONS

Preceding ACh provocation influenced following physiological assessment, particularly when ACh test was positive. Further studies are warranted to determine which interventional diagnostic procedure, ACh provocation or physiological assessment, should be preceded in the invasive evaluation of INOCA.

Factors Associated with Impaired Resistive Reserve Ratio and Microvascular Resistance Reserve

Coronary microvascular dysfunction (CMD) is described as an important subset of ischemia with no obstructive coronary artery disease. Resistive reserve ratio (RRR) and microvascular resistance reserve (MRR) have been proposed as novel physiological indices evaluating coronary microvascular dilation function. The aim of this study was to explore factors associated with impaired RRR and MRR. Coronary physiological indices were invasively evaluated in the left anterior descending coronary artery using the thermodilution method in patients suspected of CMD. CMD was defined as a coronary flow reserve <2.0 and/or index of microcirculatory resistance ≥25. Of 117 patients, 26 (24.1%) had CMD. RRR (3.1 ± 1.9 vs. 6.2 ± 3.2, p < 0.001) and MRR (3.4 ± 1.9 vs. 6.9 ± 3.5, p < 0.001) were lower in the CMD group. In the receiver operating characteristic curve analysis, RRR (area under the curve 0.84, p < 0.001) and MRR (area under the curve 0.85, p < 0.001) were both predictive of the presence of CMD. In the multivariable analysis, previous myocardial infarction, lower hemoglobin, higher brain natriuretic peptide levels, and intracoronary nicorandil were identified as factors associated with lower RRR and MRR. In conclusion, the presence of previous myocardial infarction, anemia, and heart failure was associated with impaired coronary microvascular dilation function. RRR and MRR may be useful to identify patients with CMD.