Index Of Microcirculatory Resistance Values Research Articles

Feasibility, safety and effectiveness in measuring microvascular resistance with regadenoson.

AIMThe study aims to test whether simultaneous measurement of fractional flow reserve (FFR), coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) is feasible, safe and effective during regadenoson-induced hyperemia.METHODS AND RESULTSFFR, CFR and IMR were measured simultaneously during regadenoson (Rapiscan 400 μg) -induced hyperemia in 50 patients with stable coronary artery disease with a SYNTAX score of <22. Simultaneous measurement of FFR, CFR and IMR was technically feasible in all cases (50/50). No side effects occurred and even patients fulfilling classical contraindications for the use of adenosine (10/50) could be included. Regadenoson-induced hyperemia remained stable after maximal pressure drop for more than 35 sec as measured by systemic aortic and distal coronary pressure. There was a significant drop in transit mean time from baseline to hyperemia of more than 50% (1.0 ± 0.6 s vs. 0.4 ± 0.2 s, p < 0.01). Patients' mean IMR value was 23.4, and IMR values above 75th percentile significantly correlated with metformin demanding diabetes mellitus with OR 21.76 and nicotine abuse with OR 10.28.CONCLUSIONA single intravenous regadenoson bolus via peripheral line increases coronary blood flow without harmful systemic side effects enabling interventionists to simultaneously assess FFR, CFR and IMR in patients with stable coronary artery disease.

Combined Primary PCI with Multiple Thrombus Burden Reduction Therapy Improved Cardiac Function in Patients with Acute Anterior Myocardial Infarction.

High thrombus burden induced slow-flow and no-reflow during primary percutaneous coronary intervention (PCI) and is associated with a poor prognosis. We aimed to investigate whether a combined thrombus burden reduction therapy during primary PCI, could improve microcirculation and enhance cardiac function in the long-term.Anterior wall STEMI patients with high thrombus burden were randomly assigned to receive a combined thrombus burden reduction therapy or thrombus aspiration alone. The primary end points included the percentage of patients with TMPG (TIMI myocardial perfusion grade) 3, STR (ST-segment resolution) above 70%, the index of microcirculatory resistance (IMR) and left ventricular ejection fraction (LVEF) difference.Twenty-two patients in the combined interventional group and 24 in the control group completed 1-year follow-up. The percentages of patients with TMPG 3 (68.2% versus 33.3%, P = 0.006) and STR above 70% (63.6% versus 25%, P = 0.016) were significantly higher in the combined group. IMR was significantly lower in the combined interventional group (31.50 ± 13.39 U versus 62.72 ± 22.80 U, P = 0.002). At 3 months and 1 year, the overall LVEF value was better in the combined interventional group (42.1% versus 40.0%, P = 0.049; 41.9% versus 39.8%, P = 0.042), respectively. The IMR value was negatively correlated with the EF value at 3 months (r = -0.145, P = 0.013) and 1 year (r = -0.333, P = 0.031).A combined thrombus burden reduction therapy during primary PCI can safely reduce thrombus burden, improve myocardial tissue perfusion, and improve cardiac function among STEMI patients with high thrombus burden. IMR might be a good predictor for post-myocardial infarction cardiac function.

Optical Coherence Tomography–Defined Plaque Vulnerability in Relation to Functional Stenosis Severity and Microvascular Dysfunction

ObjectivesThis study sought to investigate the relationship of unstable plaque features with physiological lesion severity and microvascular dysfunction. BackgroundThe functional severity of epicardial lesions and microvascular dysfunction are both related to adverse clinical outcomes. MethodsWe investigated 382 de novo intermediate and severe coronary lesions in 340 patients who underwent optical coherence tomography, fractional flow reserve (FFR), and index of microcirculatory resistance (IMR) examinations. Lesions were divided into tertiles based on either FFR or IMR values. The optical coherence tomography findings were compared among the tertiles of FFR and IMR. Each tertile was defined as follows: FFR-T1 (FFR <0.74), FFR-T2 (0.74 ≤ FFR ≤0.81), and FFR-T3 (FFR >0.81); and IMR-T1 (IMR ≥25), IMR-T2 (15 < IMR <25), and IMR-T3 (IMR ≤15). ResultsNo significant relationship was observed between FFR and IMR. The prevalence of optical coherence tomography–defined thin-cap fibroatheroma (TCFA) was significantly greater in IMR-T1 than in IMR-T2 and IMR-T3. An overall significant difference in the prevalence of TCFAs was detected among FFR tertiles, although no pairwise comparison revealed statistical significance. The prevalence of ruptured plaque was significantly greater in IMR-T1 than in IMR-T2 and IMR-T3, although no significant difference was observed between FFR tertiles. Multivariate analysis showed that FFR and IMR were independent predictors of the prevalence of TCFAs (odds ratio: 0.036; 95% confidence interval: 0.004 to 0342; p = 0.004; and odds ratio: 1.034; 95% confidence interval: 1.014 to 1.054; p = 0.001, respectively). ConclusionsLower FFR and higher IMR values were independent predictors of the presence of a TCFA in angiographically intermediate-to-severe stable lesions or nonculprit lesions in acute coronary syndrome.

TCT-870 Do we need wedge pressure for calculation of the index of microcirculatory resistance (IMR) post primary percutaneous coronary intervention (PPCI) in patients with ST segment elevation myocardial infarction (STEMI)?

The index of microcirculatory resistance (IMR) emerges as a valuable prognostic tool in ST elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronay intervention (PPCI). An IMR value more than 40 at the end of the procedure has been related with worse outcomes. In the

Invasive assessment of microvascular function in patients with valvular heart disease.

The aim of this study was to investigate microvascular function in patients with valvular heart disease (VHD), which causes chronic left ventricular volume and/or pressure overload, therefore change in coronary microvascular hemodynamics. We prospectively enrolled 30 patients with VHD considered for surgery (10 aortic stenosis, 12 aortic regurgitation, and eight mitral regurgitation) and 30 controls. Intracoronary physiological assessments were performed in the unobstructed left anterior descending artery using a pressure-temperature sensor guidewire at rest and hyperemia. The index of microcirculatory resistance (IMR) was similar between the two groups (16.2±6.5 vs. 16.2±8.5, P=0.997), whereas coronary flow reserve (CFR) was lower in the VHD group compared with the controls (3.2±1.4 vs. 4.3±1.7, P=0.005). Resting and hyperemic coronary distal pressure, and hyperemic mean transit time were similar between VHD and controls, whereas resting mean transit time was significantly shorter (0.70±0.29 vs. 0.89±0.39, P=0.035) and baseline resting microvascular resistance was significantly lower in the VHD group compared with the controls (58.1±25.4 vs. 78.1±36.7, P=0.011). Patients with aortic stenosis showed numerically higher IMR values than aortic regurgitation, mitral regurgitation, and controls, although this was not statistically significant (20.4±6.9, P=0.14). CFR was significantly correlated with log high-sensitivity cardiac troponin T levels in patients with VHD (r=-0.523, P=0.004). CFR was reduced in patients with VHD compared with controls, despite similar microvascular function as assessed by IMR. This appeared to be mainly because of an increased resting coronary flow accompanied by a decreased resting coronary microvascular resistance rather than microvascular disease.

Long-term prognostic value of invasive and non-invasive measures early after heart transplantation

BackgroundInvasively assessed coronary microvascular resistance early after heart transplantation predicts worse long-term outcome; however, little is known about the relationship between microvascular resistance, left ventricular function and outcomes in this setting. MethodsA total of 100 cardiac transplant recipients had fractional flow reserve (FFR) and the index of microcirculatory resistance (IMR) measured in the left anterior descending artery and echocardiographic assessment of left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS) at 1 year after heart transplantation. The primary endpoint was the composite of death and retransplantation occurring beyond the first post-operative year. ResultsThe mean FFR, IMR, LVEF, and GLS values at 1 year were 0.87 ± 0.06, 21.3 ± 17.3, 60.4 ± 5.4%, and 14.2 ± 2.4%, respectively. FFR and IMR had no significant correlation with LVEF and GLS. During a mean follow-up of 6.7 ± 4.2 years, the primary endpoint occurred in 24 patients (24.0%). By ROC curve analysis, IMR = 19.3 and GLS = 13.3% were the best cutoff values for predicting death or retransplantation. Cumulative event-free survival was significantly lower in patients with higher IMR (log-rank p = 0.02) and lower GLS (log-rank p < 0.001). Cumulative event-free survival can be further stratified by the combination of IMR and GLS (long-rank p < 0.001). By multivariable Cox proportional hazards model, higher IMR and lower GLS were independently associated with long-term death or retransplantation (elevated IMR, hazard ratio = 2.50, p = 0.04 and reduced GLS, hazard ratio = 3.79, p = 0.003, respectively). ConclusionInvasively assessed IMR does not correlate with GLS at 1 year after heart transplantation. IMR and GLS determined at 1 year may be used as independent predictors of late death or retransplantation.

Prognostic value of the index of microcirculatory resistance after percutaneous coronary intervention in patients with non-ST-segment elevation acute coronary syndrome.

The prognostic value of physiological indices in non-ST-segment elevation acute coronary syndrome (NSTE-ACS) patients undergoing percutaneous coronary intervention (PCI) is unknown. We investigated the prognostic efficacy of physiological indices obtained after PCI in patients with NSTE-ACS. Eighty-three patients (men: n = 70, age: 63.7 ± 9.7 years) undergoing PCI for NSTE-ACS within 48 hr postadmission were investigated. Fractional flow reserve (FFR), coronary flow reserve (CFR), and the index of microcirculatory resistance (IMR) of the culprit vessels were measured after the completion of PCI. The patients were clinically followed up to determine major cardiac adverse events (MACE), including death, congestive heart failure requiring hospitalization, and remote coronary revascularization. The median FFR, CFR, and IMR values were 0.90 (interquartile range [IQR] 0.86-0.95), 2.38 (IQR 1.75-4.17), and 22.9 (IQR 11.2-31.5), respectively. During a median follow-up of 20.7 months, 19 MACEs (22.9%) were documented. No significant difference in baseline patient characteristics, except for age, was detected between patients with and without MACE. Patients with MACE showed higher IMR and lower CFR than those without (IMR: 27.2 vs. 16.3; P = 0.001, CFR: 1.82 vs. 2.55; P = 0.04), whereas FFR was not significantly different (0.92 vs. 0.89; P = 0.72), irrespective of the MACE occurrence. Post-PCI IMR was the only independent predictor of MACE (hazard ratio 1.033, 95% confidence interval 1.013-1.052, P = 0.001). The MACE-free survival was significantly worse in patients with high post-PCI IMR (χ2 7.12; P = 0.008). Post-PCI IMR may help identify patients at high risk for subsequent adverse coronary events who require adjunctive therapeutic strategies.

Effects of Qishen Yiqi Dripping Pills () in Reducing Myocardial Injury and Preserving Microvascular Function in Patients Undergoing Elective Percutaneous Coronary Intervention: A Pilot Randomized Study.

To evaluate the effect of treatment with Qishen Yiqi Dripping Pills (, QSYQ) on myocardial injury and myocardial microvascular function in patients undergoing elective percutaneous coronary intervention (PCI). Eighty patients undergoing elective PCI were randomly assigned to QSYQ and control groups. The QSYQ group received QSYQ at a dosage of 0.5 g 3 times daily (3-7 days before PCI and then daily for 1 month) and regular medication, which comprised of aspirin, clopidogrel, statin, β-blocker, and angiotensin-converting enzyme inhibitor/angiotensin receptor blocker in the absence of contradiction. The control group received only the regular medication. The index of microcirculatory resistance (IMR) was measured at maximal hyperemia after PCI. The fractional flow reserve was measured before and after the procedure. Troponin I levels were obtained at baseline and 20-24 h after the procedure. Pre-PCI troponin I levels between the two groups were similar (0.028±0.05 vs. 0.022±0.04 ng/mL, P=0.55). However, post- PCI troponin I levels in the QSYQ group were significantly lower than that in the control group (0.11±0.02 vs. 0.16±0.09 ng/mL, P<0.01). IMR values were significantly lower in the QSYQ group as compared to the control group (16.5±6.1 vs. 31.2±16.0, P<0.01). Multivariate analysis identified QSYQ treatment as the only independent protective factor against IMR >32 (odds ratio=0.29, 95% confidence interval: 0.11-0.74, P=0.01). The present study demonstrated the benefit of QSYQ in reducing myocardial injury and preserving microvascular function during elective PCI.

The influence of elective percutaneous coronary intervention on microvascular resistance: a serial assessment using the index of microcirculatory resistance.

This study investigates whether hyperemic microvascular resistance (MR) is influenced by elective percutaneous coronary intervention (PCI) by using the index of microcirculatory resistance (IMR). Seventy-one consecutive patients with stable angina pectoris undergoing elective PCI were prospectively studied. The IMR was measured before and after PCI and at the 10-mo follow-up. The IMR significantly decreased until follow-up; the pre-PCI, post-PCI, and follow-up IMRs had a median of 19.8 (interquartile range, 14.6-28.9), 16.2 (11.8-22.1), and 14.8 (11.8-18.7), respectively (P < 0.001). The pre-PCI IMR was significantly correlated with the change in IMR between pre- and post-PCI (r = 0.84, P < 0.001) and between pre-PCI and follow-up (r = 0.93, P < 0.001). Pre-PCI IMR values were significantly higher in territories with decreases in IMR than in those with increases in IMR [pre-PCI IMR: 25.4 (18.4-35.5) vs. 12.5 (9.4-16.8), P < 0.001]. At follow-up, IMR values in territories showing decreases in IMR were significantly lower than those with increases in IMR [IMR at follow-up: 13.9 (10.9-17.6) vs. 16.6 (14.0-21.4), P = 0.013]. The IMR decrease was significantly associated with a greater shortening of mean transit time, indicating increases in coronary flow (P < 0.001). The optimal cut-off values of pre-PCI IMR to predict a decrease in IMR after PCI and at follow-up were 16.8 and 17.0, respectively. In conclusion, elective PCI affected hyperemic MR and its change was associated with pre-PCI MR, resulting in showing a wide distribution. Overall hyperemic MR significantly decreased until follow-up. The modified hyperemic MR introduced by PCI may affect post-PCI coronary flow.

Value of index of microcirculatory resistance in the diagnosis of cardiac syndrome X

Objective To explore the correlation between the index of microcirculatory resistance (IMR) and the corrected thrombolysis in myocardial infarction (TIMI) frame count (CTFC) in patients with cardiac syndrome X (CSX), and to discuss the value of IMR in the diagnosis of CSX. Methods This study selected 28 patients with positive treadmill exercise test (CSX group), and another 28 patients with negative treadmill exercise test (normal control group). First, the baseline CTFC (B-CTFC), and hyperemic CTFC (H-CTFC) were measured. The ratio of B-CTFC and H-CTFC was recorded as CFRCTFC. IMR was calculated by method of thermodilution. Results Proportion of patients with hypertension and diabetes in CSX group was significantly higher than that of normal control group (75% vs 46.4%, 60.7% vs 28.6%, P<0.05). IMR in the CSX group was significantly higher than that in the normal group (39.5±27.6 vs 16.1±5.9, P<0.01). H-CTFC in the CSX group was significantly higher than that in the normal group (13.0±4.2 vs 9.5±2.4, P<0.01). CFRCTFCin the CSX group was significantly lower than that in the normal group (2.0±0.5 vs 2.6±0.5, P<0.01). IMR has significant correlation with CFRCTFC (r=-0.62, P<0.01). Conclusions IMR has a notable association with CFRCTFC calculated from CTFC.IMR can provide clinical application in the evaluation of coronary microcirculation dysfunction, and can be used in the diagnosis of CSX. Key words: Capillary resistance; Microcirculation; Microvascular angina/DI

The Index of Microcirculatory Resistance Postpercutaneous Coronary Intervention Predicts Left Ventricular Recovery in Patients With Thrombolyzed ST-Segment Elevation Myocardial Infarction.

The index of microcirculatory resistance (IMR), an invasive measure of microvascular function, has been shown to correlate with clinical outcomes in patients with ST-segment elevation myocardial infarction (STEMI). The aim of this study is to evaluate the predictive value of IMR on left ventricular recovery in patients undergoing a pharmacoinvasive strategy for STEMI. The index of microcirculatory resistance was assessed following percutaneous coronary intervention (PCI) in 31 patients with STEMI who were initially managed with thrombolysis. Other markers of microvascular function such as coronary flow reserve (CFR), TIMI flow grade, corrected TIMI frame count (cTFC), and ST-segment resolution were also recorded. All indices were evaluated against measures of left ventricular function and recovery 3 months postindex event. The IMR correlated with left ventricular function, as assessed by wall motion score and ejection fraction at 3-month follow-up (r = 0.652, P = 0.005; r = -0.452, P = 0.011, respectively). The traditional methods of assessing microvascular function, such as CFR, TIMI flow grade, cTFC, and ST-segment resolution did not correlate with wall motion score and ejection fraction at 3 months. Post-PCI IMR was significantly lower in those patients with left ventricular recovery at 3 months (18 U vs 39 U, P < 0.001). The optimal cut-off value for post-PCI IMR and left ventricular recovery was 32 U. In patients in whom the IMR was greater than 32 U, the percent change in ejection fraction was significantly lower than in those patients in whom the IMR was less than 32 U (2 ± 11 vs 12 ± 8, P = 0.012). In patients presenting with STEMI initially managed with thrombolysis and subsequently undergoing PCI, IMR correlates with measures of left ventricular function and has the potential to predict left ventricular recovery at 3 months.

Intracoronary injection of tirofiban prevents microcirculation dysfunction during delayed percutaneous coronary intervention in patients with acute myocardial infarction

ObjectiveTo determine whether tirofiban can prevent microcirculation dysfunction during delayed percutaneous coronary intervention (PCI) of spontaneously recanalized and severe narrowing coronary artery in patients with acute myocardial infarction. Methods62 patients who have a single angiographically confirmed narrowing culprit coronary artery for more than 75% between 7 and 14days after the onset of acute myocardial infarction were randomly divided into the tirofiban group (32 cases) and the placebo group (30 cases). All the patients received measurement of the index of microcirculatory resistance (IMR) before tirofiban/placebo administration and PCI. After PCI, IMR value was measured again. ResultsThere was no significant variation between the two groups before PCI (11.67±6.45 of placebo group vs. 14.65±12.45 of tirofiban group, P=0.158). After PCI, the IMR value of the tirofiban group is significantly lower than that of the placebo group (23.63±9.91 of placebo group vs. 16.75±9.98 of tirofiban group, P=0.008). ConclusionsIntracoronary injection of tirofiban can significantly prevent the abnormal increase of IMR value during delayed PCI in patients with acute myocardial infarction.

Epicardial Artery Stenosis with a High Index of Microcirculatory Resistance Is Frequently Functionally Insignificant as Estimated by Fractional Flow Reserve (FFR).

Objective Differences in microvascular integrity can diversely influence the functional assessment of epicardial coronary artery disease in each patient. We investigated the relevance of the index of microcirculatory resistance (IMR) and fractional flow reserve (FFR) of intermediate coronary lesions. Methods The IMR and FFR were measured in 67 intermediate coronary lesions of the left anterior descending artery of 67 patients, by using a pressure sensor/thermistor-tipped guidewire. Results To assess the differences in FFR in relationship to the IMR value, patients were divided into tertile IMR groups as follows: Low-IMR (n=22, IMR 14±3), Mid-IMR (n=23, IMR 21±2), and High-IMR (n=22, IMR 36±10). An analysis of variance showed that the High-IMR group had significantly higher FFR values (0.87±0.07) than the Low-IMR group (0.81±0.08) (p=0.03). Functionally significant lesions with FFR ≤0.8 accounted for 9% of lesions in the High-IMR group, 36% in the Low-IMR group and 22% in the Mid-IMR group (p=0.02). In the multivariate logistic analysis, the IMR value was an independent determinant of FFR ≤0.8 (p=0.03). Conclusion In patients with a high IMR, intermediate lesions as identified with visual estimation were more frequently functionally insignificant. The IMR can provide additional information in understanding the mismatch between the anatomical and functional severity of intermediate coronary stenosis.

Fractional Flow Reserve Evaluation and Chronic Kidney Disease: Analysis From a Multicenter Italian Registry (the FREAK Study).

To establish if the presence of chronic kidney disease (CKD) influences fractional flow reserve (FFR) value in patients with intermediate coronary stenosis. FFR-guided coronary revascularization reduces cardiac adverse events in patients with coronary artery disease. CKD impairs microcirculation and increases cardiovascular risk. Whether CKD presence may limit FFR accuracy is unknown. We used data from a multicenter prospective registry enrolling 1.004 patients undergoing FFR evaluation for intermediate stenosis. We assessed the relationship between clinical and angiographic variables and FFR measurement. CKD was defined as CrCl value ≤45 ml/min. FFR value was considered potentially flow-limiting, and therefore positive, if ≤0.80. The index of microcirculatory resistance (IMR) was calculated in 20 patients stratified according CrCl value (single-center substudy). FFR measurement was positive in 395 (39%) patients. Overall, 131 (13%) patients had CKD. Patients with CrCl ≤45 ml/min showed significantly higher FFR values as compared to the others (0.84 ± 0.07 vs. 0.81 ± 0.08, p < 0.001). Positive FFR occurrence was lower in patients with CrCl ≤45 ml/min (27% vs. 41%, p < 0.01). After multivariable analysis, diabetes (HR 1.07, 95%CI 1.008-1.13, p = 0.03), left anterior descending (HR 1.35, 95%CI 1.27-1.43, p < 0.001) and CrCl ≤45 ml/min (HR 0.92, 95%CI 0.87-0.97, p = 0.005) emerged as independent predictors of FFR measurement. Accordingly, IMR values were higher in patients with CrCl ≤45 ml/min (32 U [28245] vs. 16 U [11220], p < 0.01). FFR and IMR measurements differ between CKD patients and those with normal renal function. Flow-limiting FFR is less frequent in patients with CrCl ≤45 ml/min. © 2015 Wiley Periodicals, Inc.

Comprehensive assessment of microcirculation after primary percutaneous intervention in ST-segment elevation myocardial infarction: insight from thermodilution-derived index of microcirculatory resistance and coronary flow reserve.

ObjectivesA pathophysiological mechanism of microvascular dysfunction in ST-segment elevation myocardial infarction (STEMI) is multifactorial; thus, multiple modalities were needed to precisely evaluate a microcirculation.MethodsWe complementarily assessed microcirculation in STEMI by the index of microcirculatory resistance (IMR) and coronary flow reserve (CFR) immediately after a primary percutaneous intervention in 89 STEMI patients. Cardiovascular and cerebrovascular events (MACCE) including cardiovascular death, target vessel failure, heart failure, and stroke were assessed during a mean follow-up period of 3.0 years.ResultsThe microcirculation of enrolled patients was classified into four groups using cutoff CFR and IMR values (CFR>2 and mean IMR): group-1 (n=23, CFR>2 and IMR≤27); group-2 (n=31, CFR≤2 and IMR≤27); group-3 (n=9, CFR>2 and IMR>27); and group-4 (n=26, CFR<2 and IMR>27). On echocardiography 3 months later, improvement in the wall motion score index was shown in group-1 (P<0.01), group-2 (P<0.01), and group-3 (P=0.04), whereas group-4 did not show improvement in wall motion score index (P=0.06). During clinical follow-up, there were no MACCE in group-1 and the patients in group-2 and group-3 showed significantly lower MACCE compared with group-4 (group-1=0%, group-2, and group-3=10%, group-4=23.1%, P=0.04).ConclusionComplimentary assessment of microcirculation by the IMR and CFR may be useful to evaluate myocardial viability and the long-term prognosis of STEMI patients.

Serial assessment of the index of microcirculatory resistance during primary percutaneous coronary intervention comparing manual aspiration catheter thrombectomy with balloon angioplasty (IMPACT study): a randomised controlled pilot study

ObjectiveUtilising a novel study design, we evaluated serial measurements of the index of microcirculatory resistance (IMR) in patients undergoing primary percutaneous coronary intervention (PPCI) for ST-segment elevation myocardial infarction (STEMI)...

Acute effects of chewing tobacco on coronary microcirculation and hemodynamics in habitual tobacco chewers

Background: Long-term adverse cardiovascular effects of smokeless tobacco are well established, however, the effect of chewing tobacco on coronary microcirculation and hemodynamic have not been studied. We intended to analyze the acute effect of chewing tobacco on coronary microcirculation and hemodynamics in habitual tobacco chewers with stable coronary artery disease undergoing elective percutaneous coronary intervention (PCI). Materials and Methods: We prospectively enrolled seven habitual tobacco chewers with stable coronary artery disease with single vessel disease or double vessel disease satisfying the criteria for elective PCI. Patients were instructed to keep 1 g of crushed dried tobacco leaves in the mouth after a successful PCI. Lesion in last stented vessels was evaluated for fractional flow reserve (FFR), coronary flow reserve (CFR), and index of microcirculatory resistance (IMR) post-PCI, after 15 min and 30 min of tobacco chewing along with the measurement of serum cotinine levels. Results: Oral tobacco led to high levels of cotinine in the majority of patients. There was an insignificant rise in heart rate, systolic and diastolic blood pressure following tobacco consumption. Baseline CFR (median 1.6, range 1.1–5.5) was low in tobacco chewers after PCI even after optimum FFR (0.9 ± 0.05) in the majority of patients suggesting abnormal microvascular hemodynamics (high IMR in 3 patients, overall median 14.2, range 7–36.2). However, there was no significant change in the estimated CFR or IMR values following tobacco chewing. One patient had bradycardia and hypotension which may be related to vagal reaction or acute nicotine poisoning. Conclusion: Tobacco chewers have abnormal coronary microcirculation hemodynamics even following a successful PCI. However, the coronary micocirculation and hemodynamics do not change acutely following tobacco chewing despite high serum cotinine concentrations.

Clinical and Angiographic Predictors of Microvascular Dysfunction in ST-Segment Elevation Myocardial Infarction.

PurposeWe aimed to discover clinical and angiographic predictors of microvascular dysfunction using the index of microcirculatory resistance (IMR) in patients with ST-segment elevation myocardial infarction (STEMI).Materials and MethodsWe enrolled 113 patients with STEMI (age, 56±11 years; 95 men) who underwent primary percutaneous coronary intervention (PCI). The IMR was measured with a pressure sensor/thermistor-tipped guidewire after primary PCI. The patients were divided into three groups based on IMR values: Low IMR [<18 U (12.9±2.6 U), n=38], Mid IMR [18-31 U (23.9±4.0 U), n=38], and High IMR [>31 U (48.1±17.1 U), n=37].ResultsThe age of the Low IMR group was significantly lower than that of the Mid and High IMR groups. The door-to-balloon time was <90 minutes in all patients, and it was not significantly different between groups. Meanwhile, the symptom-onset-to-balloon time was significantly longer in the High IMR group, compared to the Mid and Low IMR groups (p<0.001). In the high IMR group, the culprit lesion was found in a proximal location significantly more often than in a non-proximal location (p=0.008). In multivariate regression analysis, age and symptom-onset-to-balloon time were independent determinants of a high IMR (p=0.013 and p=0.003, respectively).ConclusionOur data suggest that age and symptom-onset-to-balloon time might be the major predictors of microvascular dysfunction in STEMI patients with a door-to-balloon time of <90 minutes.

Impact of Smoking on Coronary Microcirculatory Resistance in Patients With Coronary Artery Disease

The aim of this study was to investigate the relationship between coronary microvascular function and smoking using the 3 parameters fractional flow reserve (FFR), coronary flow reserve (CFR(thermo)), and index of microcirculatory resistance (IMR) in patients with coronary artery disease (CAD). A total of 97 CAD patients with 148 intermediate stenotic lesions were divided into two groups: current and former smokers (Smokers: n = 54), and those who had never smoked (Non-smokers: n = 43). Coronary physiology measurements were made following coronary angiography at rest and during hyperemia induced with intravenous adenosine triphosphate. If a patient had several intermediate lesions, the lesion producing the largest IMR value and minimum FFR(myo) and CFR(thermo) value was selected. Averaged over all patients, the FFR(myo), CFR(thermo), and IMR values were 0.86 ± 0.10, 2.66 ± 1.50, and 20.8 ± 10.7, respectively. There was no significant correlation between FFR(myo) and IMR. There were no significant differences between smokers and non-smokers in FFR(myo) value (median: 0.85 [IQR: 0.74-0.90] versus 0.87 [IQR: 0.83-0.90], P = 0.15) and CFR(thermo) value (median: 1.90 [IQR: 1.56-3.16] versus 2.10 [IQR: 1.50-2.67] U, P = 0.95). The IMR value was significantly greater in smokers (median: 24.2 [IQR: 16.8-32.5] U versus 18.5 [IQR: 15.4-27.0] U, P = 0.04). In multivariate analysis, smoking was an independent predictor of increased IMR. Smoking appears to have a detrimental effect on coronary microvascular function as measured by IMR.

Abstract 17658: The Impact of Elective Percutaneous Coronary Intervention on Coronary Microvascular Resistance

Background: The influence of elective percutaneous coronary intervention (PCI) in patients with stable angina pectoris on coronary microvascular function has not been fully elucidated. We performed a prospective study to investigate serial changes of microvascular function in patients undergoing elective PCI. Methods and Results: The index of microcirculatory resistance (IMR) and fractional flow reserve (FFR) was measured before, after PCI, and at follow-up (10 months) in 52 patients treated with single vessel uncomplicated elective PCI (male 80.8%, age 66.5 ± 8.3). IMR was calculated by taking collateral flow into account. The median IMR values before, after PCI, and at follow-up were 24.2 (interquartile range (IQR) 13.1-31.3), 15.8 (IQR 11.8-21.6), and 14.7 (IQR 11.3-20.9), respectively. IMR values significantly decreased after PCI (P=0.006), and showed no further significant change at follow-up. There was no significant relationship between delta IMR (post-pre IMR) values and PCI-related cardiac troponin elevations that distributed in the range of (median: 0.50 ng/dL, IQR 0.22-1.02 ng/dL). Pre-PCI IMR was not correlated with pre-PCI FFR values. Post-PCI IMR was significantly correlated with pre-PCI IMR values (P=0.005). Periprocedural IMR decrease (Pre-Post) was inversely associated with pre-PCI FFR (P=0.008) and greater improvement of FFR values by PCI was significantly associated with greater reduction of IMR values at follow-up (P=0.03). Decrease in FFR values from immediately after PCI to follow-up was greater in patients with DM (P=0.01). Furthermore, IMR at follow-up was worse in patients with DM than those without (P=0.009). Conclusions: Removal of physiologically significant epicardial stenosis leads to a decrease in microvascular resistance in patients with stable angina undergoing electively performed uncomplicated PCI. The periprocedural decrease in microvascular resistance was influenced by the hemodynamic significance of the epicardial stenosis before PCI. The baseline status of microvascular function is a significant determinant of post-PCI and follow-up microvascular function in these patients, and diabetes has an impact on the serial changes in microvascular function after successful PCI.