Doppler-derived intracoronary physiology indices predict the occurrence of microvascular injury and microvascular perfusion deficits after angiographically successful primary percutaneous coronary intervention

BACKGROUND

A total of 40% to 50% of patients with ST-segment-elevation myocardial infarction develop microvascular injury (MVI) despite angiographically successful primary percutaneous coronary intervention (PCI). We investigated whether hyperemic microvascular resistance (HMR) immediately after angiographically successful PCI predicts MVI at cardiovascular magnetic resonance and reduced myocardial blood flow at positron emission tomography (PET).

METHODS AND RESULTS

Sixty patients with ST-segment-elevation myocardial infarction were included in this prospective study. Immediately after successful PCI, intracoronary pressure-flow measurements were performed and analyzed off-line to calculate HMR and indices derived from the pressure-velocity loops, including pressure at zero flow. Cardiovascular magnetic resonance and H2 (15)O PET imaging were performed 4 to 6 days after PCI. Using cardiovascular magnetic resonance, MVI was defined as a subendocardial recess of myocardium with low signal intensity within a gadolinium-enhanced area. Myocardial perfusion was quantified using H2 (15)O PET. Reference HMR values were obtained in 16 stable patients undergoing coronary angiography. Complete data sets were available in 48 patients of which 24 developed MVI. Adequate pressure-velocity loops were obtained in 29 patients. HMR in the culprit artery in patients with MVI was significantly higher than in patients without MVI (MVI, 3.33±1.50 mm Hg/cm per second versus no MVI, 2.41±1.26 mm Hg/cm per second; P=0.03). MVI was associated with higher pressure at zero flow (45.68±13.16 versus 32.01±14.98 mm Hg; P=0.015). Multivariable analysis showed HMR to independently predict MVI (P=0.04). The optimal cutoff value for HMR was 2.5 mm Hg/cm per second. High HMR was associated with decreased myocardial blood flow on PET (myocardial perfusion reserve <2.0, 3.18±1.42 mm Hg/cm per second versus myocardial perfusion reserve ≥2.0, 2.24±1.19 mm Hg/cm per second; P=0.04).

CONCLUSIONS

Doppler-flow-derived physiological indices of coronary resistance (HMR) and extravascular compression (pressure at zero flow) obtained immediately after successful primary PCI predict MVI and decreased PET myocardial blood flow.

CLINICAL TRIAL REGISTRATION URL

http://www.trialregister.nl. Unique identifier: NTR3164.

Association of serum cystatin C levels with myocardial perfusion and cardiac functional recovery in patients with anterior wall ST elevation myocardial infarction treated with primary coronary intervention

This study sought to investigate the association of baseline serum cystatin C levels with myocardial perfusion and cardiac functional recovery in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). 108 patients with a first anterior STEMI who underwent PPCI were enrolled. Serum cystatin C was measured by immunoturbidimetric method. Patients were divided into two groups according to the median cystatin C levels on admission: group 1 (≥median, n = 54) and group 2 (<median, n = 54). Myocardial perfusion was assessed by angiographic criteria, ST-segment resolution, and the index of microcirculatory resistance (IMR). Echocardiographic wall motion score index was analyzed on admission and at 6-month follow-up. Patients with angiographically, electrocardiographically no-reflow had significantly higher cystatin C levels on admission. Patients with an IMR ≥33.7 U also had significantly higher cystatin C levels. The WMSI showed a greater improvement in group 2 than in group 1 and there was a significant negative correlation between improvement of WMSI and the cystatin C levels. There was no significant difference in MACEs between the 2 groups. However, congestive heart failure (CHF) was observed significantly more frequent in group 1 than in group 2 (18.5 vs. 5.6 %, p = 0.022). Multivariate logistic regression analysis demonstrated that cystatin C levels at admission were a significant independent predictor of angiographic no-reflow and the development of CHF at 6-month follow-up. Elevated cystatin C levels at admission were independently associated with impaired myocardial perfusion, poor cardiac functional recovery and development of CHF in patients with anterior STEMI undergoing PPCI.

Evaluation of Microvascular Disease and Clinical Outcomes

Although coronary microcirculatory dysfunction occurs in numerous cardiac conditions and influences prognosis, it has been largely ignored in clinical practice due to the lack of adequate methods for its assessment. Microcirculatory dysfuntion may result from a variety of causes, including structural remodelling (arterioles or capillaries), dysregulation (paradoxical arteriolar vasoconstriction), hypersensitivity to vasoactive factors or adrenergic drive, and extravascular compression of collapsable elements. Thus, the selection of a method to interrogate coronary microcirculation should be based on the suspected cause of dysfunction. This article reviews such assessment tools and their prognostic information.

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

PURPOSE

We 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 METHODS

We 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].

RESULTS

The 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).

CONCLUSION

Our 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.

Usefulness of Hyperemic Microvascular Resistance Index as a Predictor of Clinical Outcomes in Patients with ST-Segment Elevation Myocardial Infarction

BACKGROUND AND OBJECTIVES

Microvascular function is a useful predictor of left ventricular functional changes in patients with ST-segment elevation myocardial infarction (STEMI). We evaluated the usefulness of the hyperemic microvascular resistance index (hMVRI) for predicting long-term major adverse cardiovascular events (MACEs) in patients with STEMI assessed immediately after primary percutaneous coronary intervention (PCI).

SUBJECTS AND METHODS

hMVRI were evaluated in 145 patients with first acute STEMI treated with primary PCI using an intracoronary Doppler wire. hMVRI was defined as the ratio of mean aortic pressure over hyperemic averaged peak velocity of infarct-related artery. Major adverse cardiovascular events (MACEs) included cardiac death and re-hospitalization for congestive heart failure.

RESULTS

During the mean follow-up of 85±43 months, MACEs occurred in 17.2% of patients. Using a receiver-operating characteristics analysis, hMVRI >2.82 mm Hg·cm-1·sec (sensitivity: 87%; specificity: 69%; and area under curve: 0.818) was the best cut-off values for predicting future cardiac events. The Cox proportional hazard analysis showed that hMVRI was an independent predictor for long-term MACEs (hazard ratio 1.741, 95% confidence interval 1.348-2.264, p<0.001). The Kaplan-Meier survival analysis showed a higher incidence of MACEs in patients with hMVRI >2.82 mm Hg·cm-1·sec (p<0.001).

CONCLUSION

hMVRI was a strong predictor of long-term MACEs in patients with STEMI treated with primary PCI.

Impact of microvascular obstruction on the assessment of coronary flow reserve, index of microcirculatory resistance, and fractional flow reserve after ST-segment elevation myocardial infarction

BACKGROUND

Invasive assessment of coronary physiology (IACP) offers important prognostic insights in ST-segment elevation myocardial infarction (STEMI) but the dynamics of coronary recovery are poorly understood.

OBJECTIVES

This study sought to examine the evolution of coronary flow reserve (CFR), index of microcirculatory resistance (IMR), ratio of distal coronary pressure (Pd) to mean aortic pressure (Pa), and fractional flow reserve (FFR) in patients undergoing primary percutaneous coronary intervention (PPCI).

METHODS

82 patients with STEMI underwent IACP at PPCI. Repeat IACP was performed in 61 patients (74%) at day 1 and in 46 patients (56%) at 6 months. Contrast-enhanced cardiac magnetic resonance imaging (CMR) was performed in 45 patients (55%) at day 1 and in 41 patients (50%) at 6 months. Changes in IACP were compared between patients with and without microvascular obstruction (MVO) on CMR.

RESULTS

MVO was present in 21 of 45 patients (47%). Patients with MVO had lower CFR at PPCI and day 1 (p < 0.05) and a trend toward higher IMR values (p = 0.07). At 6 months, CFR and IMR were not significantly different between the groups. Baseline flow and Pd/Pa remained stable over time but FFR reduced significantly between PPCI and 6 months (p = 0.008); this reduction was mainly observed in patients with MVO (p = 0.006) but not in those without MVO (p = 0.21).

CONCLUSIONS

In PPCI-treated patients with STEMI, coronary microcirculation begins to recover within 24 h and recovery progresses further by 6 months. FFR significantly reduces from baseline to 6 months. The presence of MVO indicates a highly dysfunctional microcirculation.

Thrombus aspiration during primary percutaneous coronary intervention for preserving the index of microcirculatory resistance: a randomised study

AIMS

We aimed to investigate whether thrombus aspiration could preserve the index of microcirculatory resistance (IMR) after primary percutaneous coronary intervention (PCI) in patients with ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

Sixty-three patients with STEMI were randomised into two groups: primary PCI after thrombus aspiration (aspiration group, n=33) and primary PCI without thrombus aspiration (non-aspiration group, n=30). IMR was measured using a pressure-temperature sensor-tipped coronary wire. Echocardiography was performed at baseline and at six-month follow-up. No significant differences in baseline ejection fraction (EF, 47.3±8.5% vs. 49.5±7.8%, p=0.281) and baseline wall motion score index (WMSI, 1.45±0.31 vs. 1.37±0.27, p=0.299) were observed between the two groups. However, significant differences in IMR (23.5±10.2 U vs. 34.2±21.7 U, p=0.018), %E2%88%86EF (follow-up EF - baseline EF; 3.33±4.6% vs. 0.73±1.9%, p=0.005), and %E2%88%86WMSI (follow-up WMSI - baseline WMSI; -0.121±0.16 vs. -0.004±0.07, p=0.001) were observed between the two groups.

CONCLUSIONS

Thrombus aspiration as an adjunctive method to primary PCI for STEMI may preserve microvascular integrity and have beneficial effects on myocardial microcirculation.

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.

Efficacy of combination treatment with intracoronary abciximab and aspiration thrombectomy on myocardial perfusion in patients with ST-segment elevation myocardial infarction undergoing primary coronary stenting

PURPOSE

We aimed to investigate whether combination therapy using intracoronary (IC) abciximab and aspiration thrombectomy (AT) enhances myocardial perfusion compared to each treatment alone in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

MATERIALS AND METHODS

We enrolled 40 patients with STEMI, who presented within 6 h of symptom onset and had Thrombolysis in MI flow 0/1 or a large angiographic thrombus burden (grade 3/4). Patients were randomly divided into 3 groups: 10 patients who received a bolus of IC abciximab (0.25 mg/kg); 10 patients who received only AT; and 20 patients who received both treatments. The index of microcirculatory resistance (IMR) was measured with a pressure sensor/thermistor-tipped guidewire following successful PCI. Microvascular obstruction (MVO) was assessed using cardiac magnetic resonance imaging on day 5.

RESULTS

IMR was lower in the combination group than in the IC abciximab group (23.5±7.4 U vs. 66.9±48.7 U, p=0.001) and tended to be lower than in the AT group, with barely missed significance (23.5±7.4 U vs. 37.2±26.1 U, p=0.07). MVO was observed less frequently in the combination group than in the IC abciximab group (18.8% vs. 88.9%, p=0.002) and tended to occur less frequently than in the AT group (18.8% vs. 66.7%, p=0.054). No difference of IMR and MVO was found between the IC abciximab and the AT group (66.9±48.7 U vs. 37.2±26.1 U, p=0.451 for IMR; 88.9% vs. 66.7%, p=0.525 for MVO, respectively).

CONCLUSION

Combination treatment using IC abciximab and AT may synergistically improve myocardial perfusion in patients with STEMI undergoing primary PCI (Trial Registration: clinicaltrials. gov Identifier: NCT01404507).

DETermination of the role of OXygen in suspected Acute Myocardial Infarction trial

BACKGROUND

The use of supplemental oxygen in the setting of suspected acute myocardial infarction (AMI) is recommended in international treatment guidelines and established in prehospital and hospital clinical routine throughout the world. However, to date there is no conclusive evidence from adequately designed and powered trials supporting this practice. Existing data are conflicting and fail to clarify the role of supplemental oxygen in AMI.

METHODS

A total of 6,600 normoxemic (oxygen saturation [SpO2] ≥90%) patients with suspected AMI will be randomly assigned to either supplemental oxygen 6 L/min delivered by Oxymask (MedCore Sweden AB, Kista, Sweden) for 6 to 12 hours in the treatment group or room air in the control group. Patient inclusion and randomization will take place at first medical contact, either before hospital admission or at the emergency department. The Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies registry will be used for online randomization, allowing inclusion of a broad population of all-comers. Follow-up will be carried out in nationwide health registries and Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies. The primary objective is to evaluate whether oxygen reduces 1-year all-cause mortality. Secondary end points include 30-day mortality, major adverse cardiac events, and health economy. Prespecified subgroups include patients with confirmed AMI and certain risk groups. In a 3-month pilot study, the study concept was found to be safe and feasible.

CONCLUSION

The need to clarify the uncertainty of the role of supplemental oxygen therapy in the setting of suspected AMI is urgent. The DETO2X-AMI trial is designed and powered to address this important issue and may have a direct impact on future recommendations.

Beneficial effects of intracoronary nicorandil on microvascular dysfunction after primary percutaneous coronary intervention: demonstration of its superiority to nitroglycerin in a cross-over study

PURPOSE

In patients undergoing primary percutaneous coronary intervention (PCI) for the treatment of ST-segment elevation myocardial infarction (STEMI), coronary microvascular dysfunction is associated with poor prognosis. Coronary microvascular resistance is predominantly regulated by ATP-sensitive potassium (KATP) channels. The aim of this study was to clarify whether nicorandil, a hybrid KATP channel opener and nitric oxide donor, may be a good candidate for improving microvascular dysfunction even when administered after primary PCI.

METHODS

We compared the beneficial effects of nicorandil and nitroglycerin on microvascular function in 60 consecutive patients with STEMI. After primary PCI, all patients received single intracoronary administrations of nitroglycerin (250 μg) and nicorandil (2 mg) in a randomized order; 30 received nicorandil first, while the other 30 received nitroglycerin first. Microvascular dysfunction was evaluated with the index of microcirculatory resistance (IMR), defined as the distal coronary pressure multiplied by the hyperemic mean transit time.

RESULTS

As a first administration, nicorandil decreased IMR significantly more than did nitroglycerin (median [interquartile ranges]: 10.8[5.2-20.7] U vs. 2.1[1.0-6.0] U, p=0.0002).As a second administration, nicorandil further decreased IMR, while nitroglycerin did not (median [interquartile ranges]: 6.0[1.3-12.7] U vs. -1.4[-2.6 to 1.3] U, p<0.0001). The IMR after the second administration was significantly associated with myocardial blush grade, angiographic TIMI frame count after the procedure, and peak creatine kinase level.

CONCLUSION

Intracoronary nicorandil reduced microvascular dysfunction after primary PCI more effectively than did nitroglycerin in patients with STEMI, probably via its KATP channel-opening effect.

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

BACKGROUND AND OBJECTIVES

It was demonstrated that the fractional flow reserve (FFR) with partial balloon obstruction may have implications for assessing viable myocardium. In a different way, the index of microcirculatory resistance (IMR) was introduced as a useful indicator for assessing microvascular function. We evaluated the relationship between the FFR0.8 and the IMR.

SUBJECTS AND METHODS

We studied 48 consecutive patients who had undergone coronary intervention for acute myocardial infarction (AMI). After revascularization using stent(s), an undersized short balloon was positioned inside the stent and inflated to create a specific normalized pressure drop of FFR (distal coronary/aortic pressure=0.80) at rest. The FFR0.8 was obtained during hyperemia with the fixed state balloon-induced partial obstruction. IMR was measured by three injections of saline. The association between the FFR0.8 and the IMR was investigated.

RESULTS

The mean age of the patients was 60±12 years and 36 (75%) overall presented with ST-segment elevation myocardial infarction. The mean FFR0.8 was 0.68±0.06. A statistically significant correlation between the FFR0.8 and the log-transformed IMRtrue (LnIMRtrue) was found through a multivariable linear regression analysis (β=0.056, p<0.001). Both the FFR0.8 and the LnIMRtrue had a positive correlation with the log-transformed peak troponin I (TnI) with statistical significance (r(2)=0.119, p=0.017; r(2)=0.225, p=0.006, respectively).

CONCLUSION

There was a positive correlation between the LnIMRtrue and the FFR0.8. Both of the values were associated with peak TnI. Those values may be used as appropriate surrogate measures of microvascular function after AMI.

Prognostic value of the Index of Microcirculatory Resistance measured after primary percutaneous coronary intervention

BACKGROUND

Most methods for assessing microvascular function are not readily available in the cardiac catheterization laboratory. The aim of this study is to determine whether the Index of Microcirculatory Resistance (IMR), measured at the time of primary percutaneous coronary intervention, is predictive of death and rehospitalization for heart failure.

METHODS AND RESULTS

IMR was measured immediately after primary percutaneous coronary intervention in 253 patients from 3 institutions with the use of a pressure-temperature sensor wire. The primary end point was the rate of death or rehospitalization for heart failure. The prognostic value of IMR was compared with coronary flow reserve, TIMI myocardial perfusion grade, and clinical variables. The mean IMR was 40.3±32.5. Patients with an IMR >40 had a higher rate of the primary end point at 1 year than patients with an IMR ≤40 (17.1% versus 6.6%; P=0.027). During a median follow-up period of 2.8 years, 13.8% experienced the primary end point and 4.3% died. An IMR >40 was associated with an increased risk of death or rehospitalization for heart failure (hazard ratio [HR], 2.1; P=0.034) and of death alone (HR, 3.95; P=0.028). On multivariable analysis, independent predictors of death or rehospitalization for heart failure included IMR >40 (HR, 2.2; P=0.026), fractional flow reserve ≤0.8 (HR, 3.24; P=0.008), and diabetes mellitus (HR, 4.4; P<0.001). An IMR >40 was the only independent predictor of death alone (HR, 4.3; P=0.02).

CONCLUSIONS

An elevated IMR at the time of primary percutaneous coronary intervention predicts poor long-term outcomes.

Index of microcirculatory resistance as predictor for microvascular functional recovery in patients with anterior myocardial infarction

IMR is useful for assessing the microvascular dysfunction after primary percutaneous coronary intervention (PCI). It remains unknown whether index of microcirculatory resistance (IMR) reflects the functional outcome in patients with anterior myocardial infarction (AMI) with or without microvascular obstruction (MO).This study was performed to evaluate the clinical value of the IMR for assessing myocardial injury and predicting microvascular functional recovery in patients with AMI undergoing primary PCI. We enrolled 34 patients with first anterior AMI. After successful primary PCI, the mean distal coronary artery pressure (P(a)), coronary wedge pressure (P(cw)), mean aortic pressure (P(a)), mean transit time (T(mn)), and IMR (P(d)* hyperemic T(mn)) were measured. The presence and extent of MO were measured using cardiac magnetic resonance image (MRI). All patients underwent follow-up echocardiography after 6 months. We divided the patients into two groups according to the existence of MO (present; n = 16, absent; n = 18) on MRI. The extent of MO correlated with IMR (r = 0.754; P < 0.001), P(cw) (r = 0.404; P = 0.031), and P(cw)/P(d) of infarct-related arteries (r = 0.502; P = 0.016). The IMR was significantly correlated with the ΔRegional wall motion score index (r = -0.61, P < 0.01) and ΔLeft ventricular ejection fraction (r = -0.52, P < 0.01), implying a higher IMR is associated with worse functional improvement. Therefore, Intracoronary wedge pressures and IMR, as parameters for specific and quantitative assessment of coronary microvascular dysfunction, are reliable on-site predictors of short-term myocardial viability and Left ventricle functional recovery in patients undergoing primary PCI for AMI.

Coronary microvascular dysfunction in the clinical setting: from mystery to reality

Far more extensive than the epicardial coronary vasculature that can be visualized angiographically is the coronary microcirculation, which foregoes routine imaging. Probably due to the lack of techniques able to provide tangible evidence of its crucial role, the clinical importance of coronary microvascular dysfunction is not fully appreciated. However, evidence gathered over the last several decades indicates that both functional and structural abnormalities of the coronary microvasculature can lead to myocardial ischaemia, often comparable with that caused by obstructive coronary artery disease. Indeed, a marked increase in coronary microvascular resistance can impair coronary blood flow and trigger angina pectoris, ischaemic ECG shifts, and myocardial perfusion defects, and lead to left ventricular dysfunction in patients who otherwise have patent epicardial coronary arteries. This condition--often referred to as 'chest pain with normal coronary arteries' or 'cardiac syndrome X'--encompasses several pathogenic mechanisms involving the coronary microcirculation. Of importance, coronary microvascular dysfunction can occur in conjunction with several other cardiac disease processes. In this article, we review the pathogenic mechanisms leading to coronary microvascular dysfunction and its diagnostic assessment, as well as the different clinical presentations and prognostic implications of microvascular angina. As such, this review aims to remove at least some of the mystery surrounding the notion of coronary microvascular dysfunction and to show why it represents a true clinical entity.

Pressure-wire based assessment of microvascular resistance using calibrated upstream balloon obstruction: a predictor of myocardial viability

OBJECTIVES

We assess microvascular integrity as a marker of myocardial viability after coronary stenting, using only a pressure guidewire.

BACKGROUND

Microvascular integrity generally is not assessed using pressure-only guidewires because the transducer lies upstream of microvasculature. We partially inflate a balloon inside a coronary stent to achieve a specific normalized pressure drop at rest (distal coronary/aortic pressure = 0.8) and then infuse a vasodilator, to render the wire sensitive to microvascular function. We hypothesize that the further decline in pressure (ΔFFR(0.8) ) predicts MRI myocardial viability.

METHODS

We studied 29 subjects with acute coronary syndrome including myocardial infarction. After successful culprit stenting, the resting coronary/aortic pressure was set to 0.8 using temporary balloon obstruction. ΔFFR(0.8) was defined as 0.8-(distal coronary/aortic pressures) during adenosine-induced hyperemia. The average transmural extent of infarction was defined as the average area of MRI late gadolinium enhancement (after 2.8 ± 1.5 days) divided by the corresponding full thickness of the gadolinium enhanced sector in short axis slices, and was compared with ΔFFR(0.8) .

RESULTS

ΔFFR(0.8) corresponded inversely and linearly with the average transmural extent of infarction (r(2) = 0.65, P < 0.001). We found that a transmural extent of infarction of 0.50 corresponded to a ΔFFR(0.8) threshold of 0.1, and had high sensitivity and specificity (100% and 94.4%, respectively).

CONCLUSIONS

Using only an upstream pressure-sensitive guidewire and a partially obstructing balloon during pharmacologic hyperemia, we were able to predict MRI myocardial viability with high accuracy after relief of epicardial stenosis. With further validation, this may prove a useful clinical prognostic tool after percutaneous intervention.

Relation of circulating osteoprotegerin levels on admission to microvascular obstruction after primary percutaneous coronary intervention

Osteoprotegerin (OPG), a soluble member of the tumor necrosis factor receptor superfamily, has recently been linked to atherosclerosis and development of postinfarction heart failure. This study was designed to assess the association between admission OPG levels and microvascular obstruction (MVO) in patients who underwent primary percutaneous coronary intervention (p-PCI). Plasma samples for OPG analysis were obtained <30 minutes after admission in 47 patients who underwent p-PCI. Angiographic no-reflow (Thrombolysis In Myocardial Infarction [TIMI] flow grade <3 or 3 with myocardial blush grade 0 or 1 after p-PCI) was assessed immediately after p-PCI. MVO was assessed and quantified by the intracoronary hemodynamic measure of index of microcirculatory resistance performed on day 4 or 5 after p-PCI. Patients with angiographic no-reflow had significantly higher OPG levels on admission. On multiple linear regression analysis, OPG (β = 0.412, p = 0.001) and B-type natriuretic peptide (β = 0.409, p = 0.001) levels were independently and directly associated with the index of microcirculatory resistance. In conclusion, plasma OPG levels on admission are strongly associated with MVO and significantly correlated with the degree of MVO after p-PCI. It remains to be established whether improvement of microvascular perfusion is feasible with therapeutic strategies aimed to decrease circulating OPG levels.