Acute Response in the Noninfarcted Myocardium Predicts Long-Term Major Adverse Cardiac Events After STEMI

BACKGROUND

Acute ST-segment elevation myocardial infarction (STEMI) has effects on the myocardium beyond the immediate infarcted territory. However, pathophysiologic changes in the noninfarcted myocardium and their prognostic implications remain unclear.

OBJECTIVES

The purpose of this study was to evaluate the long-term prognostic value of acute changes in both infarcted and noninfarcted myocardium post-STEMI.

METHODS

Patients with acute STEMI undergoing primary percutaneous coronary intervention underwent evaluation with blood biomarkers and cardiac magnetic resonance (CMR) at 2 days and 6 months, with long-term follow-up for major adverse cardiac events (MACE). A comprehensive CMR protocol included cine, T2-weighted, T2∗, T1-mapping, and late gadolinium enhancement (LGE) imaging. Areas without LGE were defined as noninfarcted myocardium. MACE was a composite of cardiac death, sustained ventricular arrhythmia, and new-onset heart failure.

RESULTS

Twenty-two of 219 patients (10%) experienced an MACE at a median of 4 years (IQR: 2.5-6.0 years); 152 patients returned for the 6-month visit. High T1 (>1250 ms) in the noninfarcted myocardium was associated with lower left ventricular ejection fraction (LVEF) (51% ± 8% vs 55% ± 9%; P = 0.002) and higher NT-pro-BNP levels (290 pg/L [IQR: 103-523 pg/L] vs 170 pg/L [IQR: 61-312 pg/L]; P = 0.008) at 6 months and a 2.5-fold (IQR: 1.03-6.20) increased risk of MACE (2.53 [IQR: 1.03-6.22]), compared with patients with normal T1 in the noninfarcted myocardium (P = 0.042). A lower T1 (<1,300 ms) in the infarcted myocardium was associated with increased MACE (3.11 [IQR: 1.19-8.13]; P = 0.020). Both noninfarct and infarct T1 were independent predictors of MACE (both P = 0.001) and significantly improved risk prediction beyond LVEF, infarct size, and microvascular obstruction (C-statistic: 0.67 ± 0.07 vs 0.76 ± 0.06, net-reclassification index: 40% [IQR: 12%-64%]; P = 0.007).

CONCLUSIONS

The acute responses post-STEMI in both infarcted and noninfarcted myocardium are independent incremental predictors of long-term MACE. These insights may provide new opportunities for treatment and risk stratification in STEMI.

Graft flow assessment and early coronary artery bypass graft failure: a computed tomography analysis

OBJECTIVES

We evaluated graft patency by computed tomography and explored the determinants of intraoperative mean graft flow (MGF) and its contribution to predict early graft occlusion.

METHODS

One hundred and forty-eight patients under a single surgeon were prospectively enrolled. Arterial and endoscopically harvested venous conduits were used. Intraoperative graft characteristics and flows were collected. Graft patency was blindly evaluated by a follow-up computed tomography at 11.4 weeks (median).

RESULTS

Graft occlusion rate was 5.2% (n = 22 of 422; 8% venous and 3% arterial). Thirteen were performed on non-significant proximal stenosis while 9 on occluded or >70% stenosed arteries. Arterial and venous graft MGF were lower in females (Parterial = 0.010, Pvenous = 0.009), with median differences of 10 and 13.5 ml/min, respectively. Arterial and venous MGF were associated positively with target vessel diameter ≥1.75 mm (Parterial = 0.025; Pvenous = 0.002) and negatively with pulsatility index (Parterial < 0.001; Pvenous < 0.001). MGF was an independent predictor of graft occlusion, adjusting for EuroSCORE-II, pulsatility index, graft size and graft type (arterial/venous). An MGF cut-off of 26.5 ml/min for arterial (sensitivity 83.3%, specificity 80%) and 36.5 ml/min for venous grafts (sensitivity 75%, specificity 62%) performed well in predicting early graft occlusion.

CONCLUSIONS

We demonstrate that MGF absolute values are influenced by coronary size, gender and graft type. Intraoperative MGF of >26.5 ml/min for arterial and >36.5 ml/min for venous grafts is the most reliable independent predictor of early graft patency. Modern-era coronary artery bypass graft is associated with low early graft failure rates when transit time flow measurement is used to provide effective intraoperative quality assurance.

Pressure-controlled intermittent coronary sinus occlusion improves the vasodilatory microvascular capacity and reduces myocardial injury in patients with STEMI

BACKGROUND

Preliminary data suggest that pressure-controlled intermittent coronary sinus occlusion (PICSO) might reduce the infarct size (IS) in patients with anterior ST-elevation myocardial infarction (STEMI). However, the applicability of this therapy to patients with inferior STEMI and its exact mechanism of action is uncertain.

METHODS AND RESULTS

Thirty-six patients (27 anterior and 9 inferior) with STEMI underwent PICSO-assisted-primary percutaneous intervention (PPCI) and were compared with matched controls who underwent standard PCI (n = 72). Median age was 63 (55-70) years and 82% were male. Coronary microvascular status was assessed using thermodilution-derived index of microcirculatory resistance (IMR) and the vasodilatory capacity was assessed using the resistive reserve ratio (RRR). IS and microvascular obstruction (MVO) were assessed using cardiovascular magnetic resonance imaging (CMR) within 48 h and 6 months of follow-up. At completion of PPCI, IMR improved significantly in PICSO-treated patients compared with controls in patients with either anterior (63.7 [49.8-74.6] vs. 35.9 [27.9-47.6], p < 0.001) or inferior STEMI (60.0 [47.6-67.1] vs. 22.7 [18.4-35.0], p < 0.001). RRR significantly improved after PICSO treatment for anterior (1.21 [1.01-1.42] vs. 1.73 [1.51-2.16], p = 0.002) or inferior STEMI (1.39 [1.05-1.90] vs. 2.87 [2.17-3.78], p = 0.001), whereas it did not change in controls compared with baseline. Patients treated with PICSO presented significantly less frequently with MVO (66.6% vs. 86.1%, p = 0.024) and smaller 6-month IS compared with controls (26% [17%-30%] vs. 30% [21%-37%], p = 0.045).

CONCLUSION

PICSO therapy may improve microvascular function and vasodilatory capacity, which contributes to reducing IS in patients with STEMI undergoing PPCI.

Pre-procedural ATI score (age-thrombus burden-index of microcirculatory resistance) predicts long-term clinical outcomes in patients with ST elevation myocardial infarction treated with primary percutaneous coronary intervention

BACKGROUND

The ATI (Age-Thrombus burden-Index of Microvascular Resistance [IMR]) score was developed to predict suboptimal myocardial reperfusion in patients with ST-Elevation Myocardial Infarction (STEMI). When applied in the early phases of revascularization (e.g. before stent insertion), it predicts which patients are most likely to have a larger infarct size. In this study, we assessed the score's utility in determining which STEMI patients are at highest risk of clinical events during follow-up.

METHODS

The ATI-score was calculated prospectively in 254 STEMI patients using age (>50 years = 1 point), pre-stenting IMR (>40 U and < 100 U = 1 point; ≥100 U = 2 points) and angiographic thrombus score (4 = 1 point, 5 = 3 points); the cohort was stratified in high vs. low-intermediate ATI-score strata (≥4 vs. < 4, respectively).

RESULTS

After 3 years of follow-up, patients with high ATI-score presented a higher rate of Major Adverse Cardiac Events (MACE) defined as the composite of all-cause mortality, resuscitated cardiac arrest and new heart failure diagnosis (Hazard Ratio [HR]: 3.07; 95% Confidence Interval [CI]: 1.19-7.93; p = 0.02). The ATI-score showed a moderate discriminative power (c-stat: 0.69), not significantly different from that of other risk scores used in the STEMI setting. A high ATI-score was an independent predictor of MACE (HR: 3.24; 95% CI: 1.22-8.58; p = 0.018).

CONCLUSIONS

The ATI-score can discriminate patients at higher risk of long-term adverse events. The score allows predication of subsequent events even before coronary stenting, and consequently it may allow the option of individualized therapy in the early stages of the clinical care-pathway.

Pressure-bounded coronary flow reserve to assess the extent of microvascular dysfunction in patients with ST-elevation acute myocardial infarction

AIMS

Assessment of microvascular function in patients with ST-elevation acute myocardial infarction (STEMI) may be useful to determine treatment strategy. The possible role of pressure-bounded coronary flow reserve (pb-CFR) in this setting has not been determined. In this study we aimed to compare pb-CFR with thermodilution-derived physiology including the index of microcirculatory resistance (IMR) and CFRthermo in a consecutive series of patients enrolled in the OxAMI study. Moreover, we aimed to assess the presence of microvascular obstruction (MVO) and myocardial injury on cardiovascular magnetic resonance (CMR) imaging performed at 48 hours and six months in STEMI patients stratified according to pb-CFR.

METHODS AND RESULTS

Thermodilution-pressure-wire assessment of the infarct-related artery was performed in 148 STEMI patients before stenting and/or at completion of primary percutaneous coronary intervention (PPCI). The extent of the myocardial injury was assessed with CMR imaging at 48 hours and six months after STEMI. Post-PPCI pb-CFR was impaired (<2) and normal (>2) in 69.9% and 9.0% of the cases, respectively. In the remaining 21.1% of the patients, pb-CFR was "indeterminate". In this cohort, pb-CFR correlated poorly with thermodilution-derived coronary flow reserve (k=0.03, p=0.39). The IMR was significantly different across the pb-CFR subgroups. Similarly, significant differences were observed in MVO, myocardium area at risk and 48-hour infarct size (IS). A trend towards lower six-month IS was observed in patients with high (>2) post-PPCI pb-CFR. Nevertheless, pb-CFR was inferior to IMR in predicting MVO and the extent of IS.

CONCLUSIONS

Pb-CFR can identify microvascular dysfunction in patients after STEMI. It provided superior diagnostic performance compared to thermodilution-derived CFR in predicting MVO. However, IMR was superior to both pb-CFR and thermodilution-derived CFR and, consequently, IMR was the most accurate in predicting all of the studied CMR endpoints of myocardial injury after PPCI.

Coronary Microvascular Dysfunction Assessed by Pressure Wire and CMR After STEMI Predicts Long-Term Outcomes

OBJECTIVES

This study sought to evaluate the long-term prognostic implications of coronary microvascular dysfunction (CMD) when assessed with both cardiovascular magnetic resonance (CMR) and index of microcirculatory resistance (IMR) in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI).

BACKGROUND

Post-ischemic CMD can be assessed using the pressure-wire based IMR and/or by the presence of microvascular obstruction (MVO) on CMR.

METHODS

A total of 198 patients with STEMI underwent IMR and MVO assessment. Patients were classified as follows: Group 1, no significant CMD (low IMR [≤40 U] and no MVO); Group 2, CMD with either high IMR (>40 U) or MVO; Group 3, CMD with both IMR >40 U and MVO. The primary endpoint was the composite of all-cause mortality, diagnosis of new heart failure, cardiac arrest, sustained ventricular tachycardia/fibrillation, and cardioverter defibrillator implantation.

RESULTS

CMD with both high IMR and MVO was present in 23.7% of the cases (Group 3) and CMD with either high IMR or MVO was observed in 40.9% of cases (Group 2). At a median follow-up of 40.1 months, the primary endpoint occurred in 34 (17%) cases. At 1 year of follow-up, Group 3 (hazard ratio [HR]: 12.6; 95% confidence interval [CI]: 1.6 to 100.6; p = 0.017) but not Group 2 (HR: 7.2; 95% CI: 0.9 to 57.9; p = 0.062) had worse clinical outcomes compared with those with no significant CMD in Group 1. However, in the long-term, patients in Group 2 (HR: 4.2; 95% CI: 1.4 to 12.5; p = 0.009) and those in Group 3 (HR: 5.2; 95% CI: 1.7 to 16.2; p = 0.004) showed similar adverse outcomes, mainly driven by the occurrence of heart failure.

CONCLUSIONS

Post-ischemic CMD predicts a more than 4-fold increase in long-term risk of adverse outcomes, mainly driven by the occurrence of heart failure. Defining CMD by either invasive IMR >40 U or by CMR-assessed MVO showed similar risk of adverse outcomes.

Reflectance spectral analysis for novel characterization and clinical assessment of aspirated coronary thrombi in patients with ST elevation myocardial infarction

OBJECTIVE

The visual appearance of coronary thrombi may be clinically informative in ST elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (pPCI). However, subjective assessment is poorly reproducible and cannot provide an objective basis for treatment decisions or patient stratification. We have assessed the feasibility of a novel reflectance spectroscopy technique to systematically characterize coronary artery thrombi retrieved by aspiration during pPCI in patients with STEMI, and the clinical utility for predicting distal microvascular obstruction.

APPROACH

Patients with STEMI treated with pPCI and thrombus aspiration (n = 288) were recruited from the Oxford Acute Myocardial Infarction (OxAMI) Study. Of these, 158 patients underwent cardiac magnetic resonance imaging within 48 h for assessment of microvascular obstruction (MVO). Coronary thrombi were imaged by reflectance spectroscopy across wavelengths 500-800 nm.

MAIN RESULTS

Spectral data were analysed using function fitting and multivariate models. The coefficient 'c _red' determined from the fitting procedure correlated with the visually-assessed colour of thrombi ('red' or 'white') and with MVO. When applied to a reduced data set, consisting of spectra from 20 patients with the largest MVO and from 20 propensity-score-matched patients with no MVO, three multivariate analysis methods were able to discriminate spectra of thrombi from patients without MVO and with the largest MVO.

SIGNIFICANCE

Reflectance spectral analysis of coronary thrombus provides new insights into the pathology of STEMI, with potential clinical implications for emergency patient care. Further studies are warranted for validation as a point-of-care stratification tool in predicting the degree of microvascular injury and clinical outcomes in STEMI.

Hyper-acute cardiovascular magnetic resonance T1 mapping predicts infarct characteristics in patients with ST elevation myocardial infarction

BACKGROUND

Myocardial recovery after primary percutaneous coronary intervention in acute myocardial infarction is variable and the extent and severity of injury are difficult to predict. We sought to investigate the role of cardiovascular magnetic resonance T1 mapping in the determination of myocardial injury very early after treatment of ST-segment elevation myocardial infarction (STEMI).

METHODS

STEMI patients underwent 3 T cardiovascular magnetic resonance (CMR), within 3 h of primary percutaneous intervention (PPCI). T1 mapping determined the extent (area-at-risk as %left ventricle, AAR) and severity (average T1 values of AAR) of acute myocardial injury, and related these to late gadolinium enhancement (LGE), and microvascular obstruction (MVO). The characteristics of myocardial injury within 3 h was compared with changes at 24-h to predict final infarct size.

RESULTS

Forty patients were included in this study. Patients with average T1 values of AAR ≥1400 ms within 3 h of PPCI had larger LGE at 24-h (33% ±14 vs. 18% ±10, P = 0.003) and at 6-months (27% ±9 vs. 12% ±9; P < 0.001), higher incidence and larger extent of MVO (85% vs. 40%, P = 0.016) & [4.0 (0.5-9.5)% vs. 0 (0-3.0)%, P = 0.025]. The average T1 value was an independent predictor of acute LGE (β 0.61, 95%CI 0.13 to 1.09; P = 0.015), extent of MVO (β 0.22, 95%CI 0.03 to 0.41, P = 0.028) and final infarct size (β 0.63, 95%CI 0.21 to 1.05; P = 0.005). Receiver-operating-characteristic analysis showed that T1 value of AAR obtained within 3-h, but not at 24-h, predicted large infarct size (LGE > 9.5%) with 100% positive predictive value at the optimal cut-off of 1400 ms (area-under-the-curve, AUC 0.88, P = 0.006).

CONCLUSION

Hyper-acute T1 values of the AAR (within 3 h post PPCI, but not 24 h) predict a larger extent of MVO and infarct size at both 24 h and 6 months follow-up. Delayed CMR scanning for 24 h could not substitute the significant value of hyper-acute average T1 in determining infarct characteristics.

Beyond patency: Functional assessment of adequacy using internal mammary artery grafting to the left anterior descending artery

INTRODUCTION

Arterial graft physiology influences the long-term outcome of coronary artery bypass grafting (CABG). We studied factors that can affect the overall resistance to flow using internal mammary artery grafting to the left anterior descending artery.

METHODS

This was a prospective, nonrandomized observational study of 100 consecutive patients who underwent elective on-pump isolated or combined valve surgery and CABG. Coronary stenoses were assessed using conventional and quantitative coronary angiography assessment. The flow and pulsatility index (PI) of the grafts were assessed by transit-time flowmetry during cardioplegic arrest and at the end of the operation. Fractional polynomials were used to explore linearity, followed by multivariable regression analysis.

RESULTS

Univariate analysis demonstrated higher flows at the end of the operation in patients who had higher flows with the cross-clamp on (P < .001), in males (P = .004), in patients with a low PI at the end of the operation (P = .04), and in patients with a larger size of the recipient artery (P = .005). Multivariable regression analysis showed that the graft flow at the end of the operation was significantly associated with the mean flow with the cross-clamp on (P < .001), sex (P = .003), and PI at the end of the operation (P = .003). Concomitant valve surgery did not influence flows. Male patients had 18 mL/min higher flow.

CONCLUSIONS

The graft flow at the end of the operation can be determined by the flow with the cross-clamp on, the PI with the cross-clamp off and coronary artery. We reported differences in the graft flows between sexes, and for first the time, we introduced the concepts of "adequate flow" and "resistance-to-forward-flow" for patent coronary grafts.

Dynamic changes in injured myocardium, very early after acute myocardial infarction, quantified using T1 mapping cardiovascular magnetic resonance

BACKGROUND

It has recently been suggested that myocardial oedema follows a bimodal pattern early post ST-segment elevation myocardial infarction (STEMI). Yet, water content, quantified using tissue desiccation, did not return to normal values unlike oedema quantified by cardiovascular magnetic resonance (CMR) imaging. We studied the temporal changes in the extent and intensity of injured myocardium using T1-mapping technique within the first week after STEMI.

METHODS

A first group (n = 31) underwent 3 acute 3 T CMR scans (time-point (TP) < 3 h, 24 h and 6 days), including cine, native shortened modified look-locker inversion recovery T1 mapping, T2* mapping and late gadolinium enhancement (LGE). A second group (n = 17) had a single scan at 24 h with an additional T2-weighted sequence to assess the difference in the extent of area-at-risk (AAR) compared to T1-mapping.

RESULTS

The mean T1 relaxation time value within the AAR of the first group was reduced after 24 h (P < 0.001 for TP1 vs.TP2) and subsequently increased at 6 days (P = 0.041 for TP2 vs.TP3). However, the extent of AAR quantified using T1-mapping did not follow the same course, and no change was detected between TP1&TP2 (P = 1.0) but was between TP2 &TP3 (P = 0.019). In the second group, the extent of AAR was significantly larger on T1-mapping compared to T2-weighted (42 ± 15% vs. 39 ± 15%, P = 0.025). No change in LGE was detected while microvascular obstruction and intra-myocardial haemorrhage peaked at different time points within the first week of reperfusion.

CONCLUSION

The intensity of oedema post-STEMI followed a bimodal pattern; while the extent of AAR did not track the same course. This discrepancy has implications for use of CMR in this context and may explain the previously reported disagreement between oedema quantified by imaging and tissue desiccation.

Lyophilised reconstituted human platelets increase thrombus formation in a clinical ex vivo model of deep arterial injury

Platelets are the principal component of the innate haemostatic system that protect from traumatic bleeding. We investigated whether lyophilised human platelets (LHPs) could enhance clot formation within platelet-free and whole blood environments using an ex vivo model of deep arterial injury. Lyophilised human platelets were produced from stored human platelets and characterised using conventional, fluorescent and electron microscopic techniques. LHPs were resuspended in platelet-free plasma (PFP) obtained from citrated whole human blood to form final concentrations of 0,20 and 200 × 109 LHPs/L. LHPs with recalcified PFP or whole blood were perfused through the chamber at low (212 s-1) and high (1,690 s-1) shear rates with porcine aortic tunica media as thrombogenic substrate. LHPs shared morphological characteristics with native human platelets and were incorporated into clot generated from PFP or whole blood. Histomorphometrically measured mean thrombus area increased in a dose-dependent manner following the addition of LHPs to PFP under conditions of high shear [704 μm2 ± 186 μm2 (mean ± SEM), 1,511 μm2 ± 320 μm2 and 2,378 μm2 ± 315 μm2, for LHPs at 0, 20 and 200 × 109 /l, respectively (p= 0.012)]. Lyophil-ised human platelets retain haemostatic properties when reconstituted in both PFP and whole blood, and enhance thrombus formation in a model of deep arterial injury. These data suggest that LHPs have the potential to serve as a therapeutic intervention during haemorrhage under circumstances of trauma, and platelet depletion or dysfunction.

The Difference Between Success and Failure: Subintimal Stenting Around an Occluded Stent for Treatment of a Chronic Total Occlusion Due to In-Stent Restenosis

We present a case where conventional wire and equipment passage through the proximal cap of a chronic total occlusion due to in-stent restenosis was not possible. The lesion was then safely and successfully treated by deliberate passage into the subintimal space outside the previous stent with subsequent subintimal dissection and reentry into the true lumen beyond the occlusion. We then stented around the occluded stent, effectively crushing the previous stent in the true lumen and restoring flow by stenting open the new subintimal lumen. Follow-up angiography and optical coherence tomography at 6 months demonstrated good medium-term results.

Experimental exposure to diesel exhaust increases arterial stiffness in man

Introduction

Exposure to air pollution is associated with increased cardiovascular morbidity, although the underlying mechanisms are unclear. Vascular dysfunction reduces arterial compliance and increases central arterial pressure and left ventricular after-load. We determined the effect of diesel exhaust exposure on arterial compliance using a validated non-invasive measure of arterial stiffness.

Methods

In a double-blind randomized fashion, 12 healthy volunteers were exposed to diesel exhaust (approximately 350 μg/m³) or filtered air for one hour during moderate exercise. Arterial stiffness was measured using applanation tonometry at the radial artery for pulse wave analysis (PWA), as well as at the femoral and carotid arteries for pulse wave velocity (PWV). PWA was performed 10, 20 and 30 min, and carotid-femoral PWV 40 min, post-exposure. Augmentation pressure (AP), augmentation index (AIx) and time to wave reflection (Tr) were calculated.

Results

Blood pressure, AP and AIx were generally low reflecting compliant arteries. In comparison to filtered air, diesel exhaust exposure induced an increase in AP of 2.5 mmHg (p = 0.02) and in AIx of 7.8% (p = 0.01), along with a 16 ms reduction in Tr (p = 0.03), 10 minutes post-exposure.

Conclusion

Acute exposure to diesel exhaust is associated with an immediate and transient increase in arterial stiffness. This may, in part, explain the increased risk for cardiovascular disease associated with air pollution exposure. If our findings are confirmed in larger cohorts of susceptible populations, this simple non-invasive method of assessing arterial stiffness may become a useful technique in measuring the impact of real world exposures to combustion derived-air pollution.