Myocardial infarct size and location in relation to the coronary vascular bed at risk in man

Impact of cardiac patch alignment on restoring post-infarct ventricular function

Acute myocardial infarction (MI) leads to a loss of cardiac function which, following adverse ventricular remodeling (AVR), can ultimately result in heart failure. Tissue-engineered contractile patches placed over the infarct offer potential for restoring cardiac function and reducing AVR. In this computational study, we investigate how improvement of pump function depends on the orientation of the cardiac patch and the fibers therein relative to the left ventricle (LV). Additionally, we examine how model outcome depends on the choice of material properties for healthy and infarct tissue. In a finite element model of LV mechanics, an infarction was induced by eliminating active stress generation and increasing passive tissue stiffness in a region comprising 15% of the LV wall volume. The cardiac patch was modeled as a rectangular piece of healthy myocardium with a volume of 25% of the infarcted tissue. The orientation of the patch was varied from 0 to 150 ∘ relative to the circumferential plane. The infarct reduced stroke work by 34% compared to the healthy heart. Optimal patch support was achieved when the patch was oriented parallel to the subepicardial fiber direction, restoring 9% of lost functionality. Typically, about one-third of the total recovery was attributed to the patch, while the remainder resulted from restored functionality in native myocardium adjacent to the infarct. The patch contributes to cardiac function through two mechanisms. A contribution of tissue in the patch and an increased contribution of native tissue, due to favorable changes in mechanical boundary conditions.

Post-infarct evolution of ventricular and myocardial function

Adverse ventricular remodeling following acute myocardial infarction (MI) may induce ventricular dilation, fibrosis, and loss of global contractile function, possibly resulting in heart failure (HF). Understanding the relation between the time-dependent changes in material properties of the myocardium and the contractile function of the heart may further our understanding of the development of HF post-MI and guide the development of novel therapies. A finite element model of cardiac mechanics was used to model MI in a thick-walled truncated ellipsoidal geometry. Infarct core and border zone comprised 9.6 and 8.1% of the LV wall volume, respectively. Acute MI was modeled by inhibiting active stress generation. Chronic MI was modeled by the additional effect of infarct material stiffening, wall thinning and fiber reorientation. In acute MI, stroke work decreased by 25%. In the infarct core, fiber stress was reduced but fiber strain was increased, depending on the degree of infarct stiffening. Fiber work density was equal to zero. Healthy tissue adjacent to the infarct showed decreased work density depending on the degree of infarct stiffness and the orientation of the myofibers with respect to the infarct region. Thinning of the wall partially restored this loss in work density while the effects of fiber reorientation were minimal. We found that the relative loss in pump function in the infarcted heart exceeds the relative loss in healthy myocardial tissue due to impaired mechanical function in healthy tissue adjacent to the infarct. Infarct stiffening, wall thinning and fiber reorientation did not affect pump function but did affect the distribution of work density in tissue adjacent to the infarct.

Health position paper and redox perspectives on reactive oxygen species as signals and targets of cardioprotection

The present review summarizes the beneficial and detrimental roles of reactive oxygen species in myocardial ischemia/reperfusion injury and cardioprotection. In the first part, the continued need for cardioprotection beyond that by rapid reperfusion of acute myocardial infarction is emphasized. Then, pathomechanisms of myocardial ischemia/reperfusion to the myocardium and the coronary circulation and the different modes of cell death in myocardial infarction are characterized. Different mechanical and pharmacological interventions to protect the ischemic/reperfused myocardium in elective percutaneous coronary interventions and coronary artery bypass grafting, in acute myocardial infarction and in cardiotoxicity from cancer therapy are detailed. The second part keeps the focus on ROS providing a comprehensive overview of molecular and cellular mechanisms involved in ischemia/reperfusion injury. Starting from mitochondria as the main sources and targets of ROS in ischemic/reperfused myocardium, a complex network of cellular and extracellular processes is discussed, including relationships with Ca2+ homeostasis, thiol group redox balance, hydrogen sulfide modulation, cross-talk with NAPDH oxidases, exosomes, cytokines and growth factors. While mechanistic insights are needed to improve our current therapeutic approaches, advancements in knowledge of ROS-mediated processes indicate that detrimental facets of oxidative stress are opposed by ROS requirement for physiological and protective reactions. This inevitable contrast is likely to underlie unsuccessful clinical trials and limits the development of novel cardioprotective interventions simply based upon ROS removal.

Translational large animal model of coronary microvascular embolism: characterization by serial cardiac magnetic resonance and histopathology

This study aimed to construct a large animal model of coronary microvascular embolism, and investigate whether it could mimic the clinical imaging phenotypes of myocardial hypoperfusion in patients with ST-segment elevation myocardial infarction (STEMI). Nine minipigs underwent percutaneous coronary embolization with microspheres, followed by cardiac magnetic resonance (CMR) on week 1, 2 and 4 post operation. Microvascular obstruction (MVO) was defined as the isolated hypointense core within the enhanced area on late gadolinium enhancement images, which evolved during a 4-week follow-up. Fibrotic fraction of the segments was measured by Masson trichrome staining using a panoramic analysis software. Iron deposit and macrophage infiltration were quantified based on Perl's blue and anti-CD163 staining, respectively. Seven out of 9 (77.8%) minipigs survived and completed all of the imaging follow-ups. Four out of 7 (57.1%) minipigs were identified as transmural infarct with MVO. The systolic wall thickening (SWT) of MVO zone was similar to that of infarct zone (P = 0.762). Histopathology revealed transmural deposition of collagen, with microvessels obstructed by microspheres. The fibrotic fraction of infarct with MVO segments was similar to that of infarct without MVO segments (P = 0.954). The fraction of iron deposit in infarct with MVO segments was higher than that of infarct without MVO segments (P < 0.05), but the fraction of macrophage infiltration between these two segments did not show statistical difference (P = 0.723). Large animal model of coronary microvascular embolism could mimic most clinical imaging phenotypes of myocardial hypoperfusion in patients with STEMI, demonstrated by serial CMR and histopathology.

Three-Year Clinical Outcomes Based on Pre-Percutaneous Coronary Intervention Coronary Blood Flow Grade and Symptom-to-Balloon Time in Patients with Non-ST-Segment Elevation Myocardial Infarction

We compared the 3-year clinical outcomes according to the degree of pre-percutaneous coronary intervention thrombolysis in myocardial infarction flow grade (pre-PCI TIMI) and symptom-to-balloon time (SBT) individuals who underwent successful stent implantation with a diagnosis of non-ST-segment elevation myocardial infarction (NSTEMI). A total of 4910 patients with NSTEMI were divided into two groups: pre-PCI TIMI 0/1 (SBT < 48 h: n = 1328, SBT ≥ 48 h: n = 558) and pre-PCI TIMI 2/3 (SBT < 48 h: n = 1965, SBT ≥ 48 h: n = 1059). The primary outcome was a 3-year all-cause death rate, and the secondary outcome was the composite endpoint of 3-year all-cause death, recurrent MI, or any repeat revascularization rate. After adjustment, in the pre-PCI TIMI 0/1 group, the 3-year all-cause death (p = 0.003), cardiac death (CD, p < 0.001), and secondary outcome (p = 0.030) values were significantly higher in the SBT ≥ 48 h group than in the SBT < 48 h group. However, patients with pre-PCI TIMI 2/3 had similar primary and secondary outcomes, regardless of the SBT group. Within the SBT < 48 h group, the pre-PCI TIMI 2/3 group exhibited significantly higher rates of 3-year all-cause death, CD, recurrent MI, and secondary outcome values than the pre-PCI TIMI 0/1 group. Patients in the SBT ≥ 48 h group with either pre-PCI TIMI 0/1 or TIMI 2/3 had similar primary and secondary outcomes. Our results suggest that shortening the SBT may confer a survival benefit in patients with NSTEMI and those in the pre-PCI TIMI 0/1 group compared to those in the pre-PCI TIMI 2/3 group.

A myocardial infarct border-zone-on-a-chip demonstrates distinct regulation of cardiac tissue function by an oxygen gradient

After a myocardial infarction, the boundary between the injured, hypoxic tissue and the adjacent viable, normoxic tissue, known as the border zone, is characterized by an oxygen gradient. Yet, the impact of an oxygen gradient on cardiac tissue function is poorly understood, largely due to limitations of existing experimental models. Here, we engineered a microphysiological system to controllably expose engineered cardiac tissue to an oxygen gradient that mimics the border zone and measured the effects of the gradient on electromechanical function and the transcriptome. The gradient delayed calcium release, reuptake, and propagation; decreased diastolic and peak systolic stress; and increased expression of inflammatory cascades that are hallmarks of myocardial infarction. These changes were distinct from those observed in tissues exposed to uniform normoxia or hypoxia, demonstrating distinct regulation of cardiac tissue phenotypes by an oxygen gradient. Our border-zone-on-a-chip model advances functional and mechanistic insight into oxygen-dependent cardiac tissue pathophysiology.

Cardioprotective factors against myocardial infarction selected in vivo from an AAV secretome library

Therapies for patients with myocardial infarction and heart failure are urgently needed, in light of the breadth of these conditions and lack of curative treatments. To systematically identify previously unidentified cardioactive biologicals in an unbiased manner in vivo, we developed cardiac FunSel, a method for the systematic, functional selection of effective factors using a library of 1198 barcoded adeno-associated virus (AAV) vectors encoding for the mouse secretome. By pooled vector injection into the heart, this library was screened to functionally select for factors that confer cardioprotection against myocardial infarction. After two rounds of iterative selection in mice, cardiac FunSel identified three proteins [chordin-like 1 (Chrdl1), family with sequence similarity 3 member C (Fam3c), and Fam3b] that preserve cardiomyocyte viability, sustain cardiac function, and prevent pathological remodeling. In particular, Chrdl1 exerted its protective activity by binding and inhibiting extracellular bone morphogenetic protein 4 (BMP4), which resulted in protection against cardiomyocyte death and induction of autophagy in cardiomyocytes after myocardial infarction. Chrdl1 also inhibited fibrosis and maladaptive cardiac remodeling by binding transforming growth factor-β (TGF-β) and preventing cardiac fibroblast differentiation into myofibroblasts. Production of secreted and circulating Chrdl1, Fam3c, and Fam3b from the liver also protected the heart from myocardial infarction, thus supporting the use of the three proteins as recombinant factors. Together, these findings disclose a powerful method for the in vivo, unbiased selection of tissue-protective factors and describe potential cardiac therapeutics.

Faster skin wound healing predicts survival after myocardial infarction

Both skin wound healing and the cardiac response to myocardial infarction (MI) progress through similar pathways involving inflammation, resolution, tissue repair, and scar formation. Due to the similarities, we hypothesized that the healing response to skin wounding would predict future response to MI. Mice were given a 3-mm skin wound using a disposable biopsy punch and the skin wound was imaged daily until closure. The same set of animals was given MI by permanent coronary artery ligation 28 days later and followed for 7 days. Cardiac physiology was measured by echocardiography at baseline and MI days 3 and 7. Animals that survived until day 7 were grouped as survivors, and animals that died from MI were grouped as nonsurvivors. Survivors had faster skin wound healing than nonsurvivors. Faster skin wound healing predicted MI survival better than commonly used cardiac functional variables (e.g., infarct size, fractional shortening, and end diastolic dimension). N-glycoproteome profiling of MI day 3 plasma revealed α2-macroglobulin and ELL-associated factor 1 as strong predictors of future MI death and progression to heart failure. A second cohort of MI mice validated these findings. To investigate the clinical relevance of α2-macroglobulin, we mapped the plasma glycoproteome in patients with MI 48 h after admission and in healthy controls. In patients, α2-macroglobulin was increased 48 h after MI. Apolipoprotein D, another plasma glycoprotein, detrimentally regulated both skin and cardiac wound healing in male but not female mice by promoting inflammation. Our results reveal that the skin is a mirror to the heart and common pathways link wound healing across organs.NEW & NOTEWORTHY Faster skin wound healers had more efficient cardiac healing after myocardial infarction (MI). Two plasma proteins at D3 MI, EAF1 and A2M, predicted MI death in 66% of cases. ApoD regulated both skin and cardiac wound healing in male mice by promoting inflammation. The skin was a mirror to the heart and common pathways linked wound healing across organs.

Effect of Infarction-Related Artery Location on Clinical Outcome of Patients With Acute Myocardial Infarction in the Contemporary Era of Percutaneous Coronary Intervention - Subanalysis From the Prospective Japan Acute Myocardial Infarction Registry (JAMIR)

BACKGROUND

Previous studies have reported that acute myocardial infarction (AMI) related to left anterior descending (LAD) lesion is associated with worse outcomes than left circumflex artery (LCX) or right coronary artery (RCA) lesions. However, it is unknown whether those relationships are still present in the contemporary era of primary percutaneous coronary intervention (PCI), using newer generation drug-eluting stents and potent antiplatelet agents.

METHODS AND RESULTS

This study is a sub-analysis of the Japan AMI Registry (JAMIR), a multicenter, prospective registry enrolling 3,411 AMI patients between December 2015 and May 2017. Among them, 2,780 patients undergoing primary PCI for only a culprit vessel were included and stratified based on infarction-related artery type (LAD, LCX, and RCA). The primary outcome was 1-year cardiovascular death. The overall incidence of cardiovascular death was 3.4%. Patients with LAD infarction had highest incidence of cardiovascular death compared to patients with LCX and RCA infarction (4.8%, 1.3%, and 2.4%, respectively); however, landmark analysis showed that culprit vessel had no significant effect on cardiovascular death if a patient survived 30 days after primary PCI. LAD lesion infarction was an independent risk factor for cardiovascular death in adjusted Cox regression analysis.

CONCLUSIONS

The present sub-analysis of the JAMIR demonstrated that LAD infarction is still associated with worse outcomes, especially during the first 30 days, even in the contemporary era of PCI.

Long-Term Outcomes of Complete Revascularization With Percutaneous Coronary Intervention in Acute Coronary Syndromes

OBJECTIVES

The aim of this study was to evaluate the long-term outcomes of patients with acute coronary syndromes (ACS) with multivessel disease undergoing percutaneous coronary intervention (PCI).

BACKGROUND

Controversy exists regarding the benefit of multivessel PCI across the spectrum of ACS.

METHODS

A total of 9,094 patients with ACS and multivessel disease (≥70% stenosis in 2 or more major epicardial vessels) undergoing PCI from the Alberta COAPT (Contemporary Acute Coronary Syndrome Patients Invasive Treatment Strategies) registry (April 1, 2007, to March 31, 2013) were reviewed. Comparisons were made between patients who underwent complete revascularization and those with incomplete revascularization. Complete revascularization was defined as multivessel PCI with a residual angiographic jeopardy score ≤10%. Associations between revascularization status and all-cause death or new myocardial infarction (primary composite endpoint) and all-cause death, new myocardial infarction, or repeat revascularization (secondary composite endpoint) were evaluated.

RESULTS

Of the study cohort, 66.0% underwent complete revascularization. Compared with incomplete revascularization, the primary composite endpoint occurred less frequently with complete revascularization (event rate within 5 years 15.4% vs. 22.2%; inverse probability-weighted hazard ratio [IPW-HR]: 0.78; 95% confidence interval [CI]: 0.73 to 0.84; p < 0.0001). The secondary composite endpoint was less likely to occur with complete revascularization (event rate within 5 years 23.3% vs. 37.5%; IPW-HR: 0.61; 95% CI: 0.58 to 0.65; p < 0.0001). Complete revascularization was associated with a reduction in all-cause death (IPW-HR: 0.79; 95% CI: 0.73 to 0.86; p = 0.0004), new myocardial infarction (IPW-HR: 0.76; 95% CI: 0.69 to 0.84; p < 0.0001), and repeat revascularization (IPW-HR: 0.53; 95% CI: 0.49 to 0.57; p < 0.0001).

CONCLUSIONS

Results from this large contemporary registry of patients with ACS and PCI for multivessel disease suggest that complete revascularization occurs commonly and is associated with improved clinical outcomes (including survival) within 5 years.

The accuracy of distribution of non-ST elevation electrocardiographic changes in localising the culprit vessel in non-ST elevation myocardial infarction

Introduction

ST-segment elevation distribution on electrocardiogram (ECG) in patients presenting with ST-elevation myocardial infarction (STEMI) accurately localises the culprit vessel. However, the utility of the ECG changes in localising the coronary culprit territory in the setting of non-ST segment elevation myocardial infarction (NSTEMI) is not well established.

Material and methods

This study included patients presenting with NSTEMI, who had dynamic non-ST elevation ischaemic changes in one or more ECG leads and underwent percutaneous coronary intervention (PCI) in a single vessel between October 2011 and November 2017 in a single university hospital institution. The accuracy, sensitivity, and specificity of the distribution of ECG changes in localising the culprit vessel were calculated.

Results

There was a total of 82 patients included in this study, who received PCI to the left anterior descending (LAD), right coronary artery (RCA), and left circumflex (LCX), in 43.9%, 24.4%, and 31.7%, respectively; 51% were male. In this cohort, sensitivity of ECG in localising single-culprit-vessel NSTEMI was 41.5%. The overall accuracy of ECG changes was 50.0%, 72.0%, and 70.0% in LAD, RCA, and LCX distribution, respectively. The sensitivity and specificity were 72.2% and 32.6% in LAD distribution, 20% and 88.7% in RCA distribution, and 15.4% and 82.1% in LCX distributions, respectively.

Conclusions

Ischaemic non-ST elevation ECG changes had modest accuracy in localising the culprit vessel in patients with PCI-treated NSTEMI. These changes were more sensitive in LAD distribution and more specific in RCA and LCX distributions.

Degree of ST-segment elevation in patients with STEMI reflects the acute ischemic burden and the salvage potential

BACKGROUND

ST-segment elevation myocardial infarction (STEMI) is clinically diagnosed by significant ST-segment elevation (STE) in the electrocardiogram (ECG). The importance of the sum of significant ST-segment elevation (∑STE) before primary percutaneous coronary intervention (PPCI) - considered an indicator of the degree of ischemia - is sparse. We evaluated the association of ∑STE before PPCI with respect to area at risk, infarct size and myocardial salvage.

METHODS

A total of 503 patients with STEMI and available cardiac magnetic resonance (CMR) were included. CMR was performed at day 1 (interquartile range [IQR], 1-1) and at follow-up at day 92 (IQR, 88-96). The ECG before PPCI with the most prominent STE was used for analysis.

RESULTS

∑STE divided into quartiles were progressive linearly associated with area at risk (p < 0.001), final infarct size (p < 0.001) and extent of microvascular obstruction (p < 0.001) and inverse linearly associated with final myocardial salvage (p < 0.001). Similar results were found for linear regression analyses. However, ∑STE was not associated with final myocardial salvage in patients with pre-PCI TIMI (thrombolysis in myocardial infarction) flow 0/1 (p = 0.24) in contrast to patients with pre-PCI TIMI flow 2/3 (p ≤ 0.001).

CONCLUSION

In patients with STEMI presenting within 12 h of symptom onset, the degree of STE in the ECG before PPCI is a marker of the extent of myocardium at risk that in turn affects the infarct size in patients with pre-PCI TIMI flow 0/1, whereas the degree of STE in patients with pre-PCI TIMI flow 2/3 is a marker of the extent of the myocardium at risk as well as myocardial salvage - both affecting the myocardial damage.

“Takotsubo effect” in patients with ST segment elevation myocardial infarction

Background

Myocardial infarction can be a trigger of Takotsubo syndrome. We recently characterized imaging features of acute myocardial infarction-induced Takotsubo syndrome (“Takotsubo effect”). In this study, we investigate diagnostic and prognostic implications of Takotsubo effect in patients with anterior wall ST-segment elevation myocardial infarction.

Methods

We enrolled 111 consecutive patients who developed anterior wall ST-segment elevation myocardial infarction and received percutaneous coronary intervention, and studied systolic/diastolic function, hemodynamic consequences, adverse cardiac events, as well as 30-day and five-year outcomes in patients with and without Takotsubo effect.

Results

Patients with Takotsubo effect showed significantly worse average peak systolic longitudinal strain (–9.5 ± 2.6% vs –11.1 ± 3.6%, p = 0.038), left ventricular ejection fraction (38.5 ± 6.8% vs 47.7 ± 8.7%, p = 0.000) and myocardial performance index (0.54 ± 0.17 vs 0.37 ± 0.15, p = 0.000) within 48 h of myocardial infarction. There was no significant difference between the two groups in diastolic ventricular filling pressures, hemodynamic consequences, and 30-day rehospitalization and mortality (Gehan-Breslow-Wilcoxon test: p = 0.157). However, patients with Takotsubo effect developed more major adverse cardiac events (log-rank test: p = 0.019) when tested at the five-year follow-up. Cox regression analysis revealed that age, hypotension, tricuspid annular plane systolic excursion, and Takotsubo effect were independent prediction factors for five-year major adverse cardiac events. The Doppler/tissue Doppler parameter E/e’ correlated with MACE only in patients without Takotsubo effect.

Conclusion

Takotsubo effect secondary to anterior ST-segment elevation myocardial infarction predicts a worse long-term prognosis.

Vessel-specific coronary perfusion territories using a CT angiogram with a minimum cost path technique and its direct comparison to the American Heart Association 17-segment model

OBJECTIVES

This study compared the accuracy of an automated, vessel-specific minimum cost path (MCP) myocardial perfusion territory assignment technique as compared with the standard American Heart Association 17-segment (AHA) model.

METHODS

Six swine (42 ± 9 kg) were used to evaluate the accuracy of the MCP technique and the AHA method. In each swine, a dynamic acquisition, comprised of twenty consecutive whole heart volume scans, was acquired with a computed tomography scanner, following peripheral injection of contrast material. From this acquisition, MCP and AHA perfusion territories were determined, for the left (LCA) and right (RCA) coronary arteries. Each animal underwent additional dynamic acquisitions, consisting of twenty consecutive volume scans, following direct intracoronary contrast injection into the LCA or RCA. These images were used as the reference standard (REF) LCA and RCA perfusion territories. The MCP and AHA techniques' perfusion territories were then quantitatively compared with the REF perfusion territories.

RESULTS

The myocardial mass of MCP perfusion territories (M_MCP) was related to the mass of reference standard perfusion territories (M_REF) by M_MCP = 0.99M_REF + 0.39 g (r = 1.00; R² = 1.00). The mass of AHA perfusion territories (M_AHA) was related to M_REF by M_AHA = 0.81M_REF + 5.03 g (r = 0.99; R² = 0.98).

CONCLUSION

The vessel-specific MCP myocardial perfusion territory assignment technique more accurately quantifies LCA and RCA perfusion territories as compared with the current standard AHA 17-segment model. Therefore, it can potentially provide a more comprehensive and patient-specific evaluation of coronary artery disease.

KEY POINTS

• The minimum cost path (MCP) technique accurately determines left and right coronary artery perfusion territories, as compared with the American Heart Association 17-segment (AHA) model. • The minimum cost path (MCP) technique could be applied to cardiac computed-tomography angiography images to accurately determine patient-specific left and right coronary artery perfusion territories. • The American Heart Association 17-segment (AHA) model often fails to accurately determine left and right coronary artery perfusion territories, especially in the inferior and inferoseptal walls of the left ventricular myocardium.

Combination of Lesion Stenosis and Myocardial Supply Area Assessed by Coronary Computed Tomography Angiography for Prediction of Myocardial Ischemia

Recent clinical studies revealed that anatomical information assessed by coronary computed tomography angiography (CTA) may be used effectively to diagnose coronary artery disease (CAD). However, a physiological assessment, demonstrating myocardial ischemia, is required to justify a therapeutic strategy for CAD. This study aimed to investigate whether using CTA to assess myocardial supply area can improve the prediction of myocardial ischemia.We analyzed 201 vessels with moderate (luminal narrowing ≥ 50%, < 70%) and severe (luminal narrowing ≥ 70%, < 99%) stenosis on CTA from 174 patients, who were suspected of having stable angina and underwent measurement of fractional flow reserve (FFR). The myocardial area supplied by the coronary artery, distal to the stenosis, was evaluated with CTA, as reported previously (modified Alberta Provincial Project for Outcome Assessment in Coronary Heart score) and was classified into 3 groups (large, medium, and small).Both percentage area stenosis and myocardial supply area were significantly correlated with FFR (r = -0.46, P < 0.01, and r = -0.45, P < 0.01). Among patients who had coronary plaques, with moderate stenosis and a small myocardial supply area, only 3 of 42 lesions (7%) were identified as ischemic; deviation from the ischemic threshold (FFR = 0.80) was P < 0.01. The combined assessment of lesion stenosis and myocardial supply area, using CTA, improved the prediction of myocardial ischemia significantly compared to lesion stenosis alone (77% versus 59%, P < 0.01).Adding the assessment of myocardial supply area to standard CTA might help predict myocardial ischemia in patients with stable angina pectoris.

Gender but not diabetes, hypertension or smoking affects infarct evolution in ST-elevation myocardial infarction patients - data from the CHILL-MI, MITOCARE and SOCCER trials

BACKGROUND

Infarct evolution rate and response to acute reperfusion therapy may differ between patients, which is important to consider for accurate management and treatment of patients with ST-elevation myocardial infarction (STEMI). The aim of this study was therefore to investigate the association of infarct size and myocardial salvage with gender, smoking status, presence of diabetes or history of hypertension in a cohort of STEMI-patients.

METHODS

Patients (n = 301) with first-time STEMI from the three recent multi-center trials (CHILL-MI, MITOCARE and SOCCER) underwent cardiac magnetic resonance (CMR) imaging to determine myocardium at risk (MaR) and infarct size (IS). Myocardial salvage index (MSI) was calculated as MSI = 1-IS/MaR. Pain to balloon time, culprit vessel, trial treatments, age, TIMI grade flow and collateral flow by Rentrop grading were included as explanatory variables in the statistical model.

RESULTS

Women (n = 66) had significantly smaller MaR (mean difference: 5.0 ± 1.5% of left ventricle (LV), p < 0.01), smaller IS (mean difference: 5.1 ± 1.4% of LV, p = 0.03), and larger MSI (mean difference: 9.6 ± 2.8% of LV, p < 0.01) compared to men (n = 238). These differences remained significant when adjusting for other explanatory variables. There were no significant effects on MaR, IS or MSI for diabetes, hypertension or smoking.

CONCLUSIONS

Female gender is associated with higher myocardial salvage and smaller infarct size suggesting a pathophysiological difference in infarct evolution between men and women.

Index of Microcirculatory Resistance as a Tool to Characterize Microvascular Obstruction and to Predict Infarct Size Regression in Patients With STEMI Undergoing Primary PCI

OBJECTIVES

This study aimed to compare the value of the index of microcirculatory resistance (IMR) and microvascular obstruction (MVO) measured by cardiac magnetic resonance (CMR) in patients treated for and recovering from ST-segment elevation myocardial infarction.

BACKGROUND

IMR can identify patients with microvascular dysfunction acutely after primary percutaneous coronary intervention (pPCI), and a threshold of >40 has been shown to be associated with an adverse clinical outcome. Similarly, MVO is recognized as an adverse feature in patients with ST-segment elevation myocardial infarction. Even though both IMR and MVO reflect coronary microvascular status, the interaction between these 2 parameters is uncertain.

METHODS

A total of 110 patients treated with pPCI were included, and IMR was measured immediately at completion of pPCI. Infarct size (IS) as a percentage of left ventricular mass was quantified at 48 h (38.4 ± 12.0 h) and 6 months (194.0 ± 20.0 days) using CMR. MVO was identified and quantified at 48 h by CMR.

RESULTS

Overall, a discordance between IMR and MVO was observed in 36.7% of cases, with 31 patients having MVO and IMR ≤40. Compared with patients with MVO and IMR ≤40, patients with both MVO and IMR >40 had an 11.9-fold increased risk of final IS >25% at 6 months (p = 0.001). Patients with MVO and IMR ≤40 had a significantly smaller IS at 6 months (p = 0.001), with significant regression in IS over time (34.4% [interquartile range (IQR): 27.3% to 41.0%] vs. 22.3% [IQR: 16.0% to 30.0%]; p = 0.001).

CONCLUSIONS

Discordant prognostic information was obtained from IMR and MVO in nearly one-third of cases; however, IMR can be helpful in grading the degree and severity of MVO.

Discrepant myocardial microvascular perfusion and mechanics after acute myocardial infarction: Characterization of the "Tako-tsubo effect" with real-time myocardial perfusion contrast echocardiograph

BACKGROUND

In patients with acute anterior myocardial infarction (MI), sometimes an "apical ballooning" contractile dysfunction pattern that exceeds factual myocardial injury is identified in the ventriculography and bedside echocardiography. The hemodynamic consequences/sequela of this "Tako-tsobu effect" has not been well delineated. Of note, this anatomic imaging finding often misleads frontline physicians who assume reciprocal causation of persistent cardiac pump failure and ventricular pressure overload.

METHODS AND RESULTS

Using real-time myocardial perfusion contrast echocardiography (MCE), we investigated myocardial (microvascular) perfusion in 60 patients after acute MI and coronary revascularization. Twenty-eight percent of the studied patients showed significantly mismatched myocardial perfusion and contractile defects. In these patients, an integrated imaging assessment with coronary angiography/ventriculography, deformation echocardiography, and MCE proved that the myocardial mechanic abnormalities significantly exceeded the defected perfusion areas. Compared with 72% of the patients without perfusion-contractility mismatch, apparently worse systolic functions (left ventricular ejection, wall motion score, and systolic longitudinal strain) in these patients did not change diastolic ventricular filling pressures (E/E' and E/A) or hemodynamic consequences/adverse events. Both systolic and diastolic functions in patients with perfusion-contractility mismatch appeared to be comparable with those in patients with Tako-tsubo syndrome.

CONCLUSIONS

Real-time MCE identifies discrepant myocardial microvascular perfusion and mechanics in patients with acute MI. The "Tako-tsubo effect" in patients with perfusion-contractility mismatch does not cause diastolic filling pressure change or worse hemodynamic consequence/cardiac event.

Diagnostic performance of the quantification of myocardium at risk from MPI SPECT/CTA 2G fusion for detecting obstructive coronary disease: A multicenter trial

BACKGROUND

The effective non-invasive identification of coronary artery disease (CAD) and its proper referral for invasive treatment are still unresolved issues. We evaluated our quantification of myocardium at risk (MAR) from our second generation 3D MPI/CTA fusion framework for the detection and localization of obstructive coronary disease.

METHODS

Studies from 48 patients who had rest/stress MPI, CTA, and ICA were analyzed from 3 different institutions. From the CTA, a 3D biventricular surface of the myocardium with superimposed coronaries was extracted and fused to the perfusion distribution. Significant lesions were identified from CTA readings and positioned on the fused display. Three estimates of MAR were computed on the 3D LV surface on the basis of the MPI alone (MARp), the CTA alone (MARa), and the fused information (MARf). The extents of areas at risk were used to generate ROC curves using ICA anatomical findings as reference standard.

RESULTS

Areas under the ROC curve (AUC) for CAD detection using MARf was 0.88 (CI = 0.75-0.95) and for MARp and MARa were, respectively 0.82 (CI = 0.69-0.92) and 0.75 (CI = 0.60-0.86) using the ≥70% stenosis criterion. AUCs for CAD localization (all vessels) using MARf showed significantly higher performance than either MARa or MARp or both.

CONCLUSIONS

Using ICA as the reference standard, MAR as the quantitative parameter, and AUC to measure diagnostic performance, MPI-CTA fusion imaging provided incremental diagnostic information compared to MPI or CTA alone for the diagnosis and localization of CAD.

Assessment of the area at risk after acute myocardial infarction using 123I-MIBG SPECT: Comparison with the angiographic APPROACH-score

BACKGROUND

Assessment of the area at risk (AAR) associated with an acute myocardial infarction is crucial for evaluating prevention and revascularization strategies. The aim of this study was to evaluate whether 123I-metaiodobenzylguanidine (123I-MIBG) single-photon emission computed tomography (SPECT) provides a more widely available assessment of anatomical AAR than the established anatomical angiographic methods.

METHODS

Seventy patients with ST-segment elevation acute myocardial infarction (STEMI) underwent coronary angiography with percutaneous coronary intervention and subsequent 123I-MIBG myocardial scintigraphy with left myocardial relative radiotracer uptake evaluation 12 ± 10 days after STEMI. Patients were divided into two groups depending on whether the culprit artery was occluded (50 patients) or sub-occluded (20 patients). Two scores were calculated as a percentage of the left ventricular myocardium surface, the first using a standard 17-segment summed rest score derived from the relative quantitative evaluation of 123I-MIBG myocardial uptake (MAR) and the second using the modified APPROACH-score (ApAR).

RESULTS

For the patients with occluded artery, this study showed a high correlation between MAR and the angiographic score (Pearson r = .762 and P < .0001). For the patients with sub-occluded artery, for which the ApAR is not reliable, this study showed no correlation between MAR and the angiographic score (Pearson r = .18 and P = 0.45).

CONCLUSIONS

123I-MIBG myocardial scintigraphy provides ARR assessment similar to that of ApAR in patients with a single occluded coronary artery. However, MAR differs from ApAR when angiographic scores are known to be inaccurate (sub-occluded culprit artery) or impossible to use. Further studies are needed to evaluate the potential clinical interest of 123I-MIBG SPECT as an alternative for area at risk assessment after STEMI even when the culprit artery is sub-occluded or when the angiographic scores cannot be used.

Acute myocardial infarction and lesion location in the left circumflex artery: importance of coronary artery dominance

AIMS

Due to the limitations of 12-lead ECG, occlusions of the left circumflex artery (LCX) are more likely to present as non-ST-elevation acute coronary syndrome (NSTEACS) compared with other coronary arteries. We aimed to study mortality in patients with LCX lesions and to assess the importance of coronary artery dominance on triage of these patients.

METHODS AND RESULTS

From the Eastern Danish Heart Registry, 3,632 NSTEACS and 3,907 ST-elevation myocardial infarction (STEMI) consecutive, single-vessel disease patients were included. LCX was the culprit in 25% of NSTEACS and 14% of STEMIs (p<0.001). LCX lesions presented predominantly as STEMI in left dominant coronary arteries compared with NSTEACS (46% vs. 30%, p<0.001). Higher 30-day mortality was found in LCX-STEMI compared with LCX-NSTEACS (HR 7.9, 95% CI: 3.2-19.7, p<0.001) with no difference in long-term mortality (HR 0.9, 95% CI: 0.7-1.2, p=0.5). LCX-NSTEACS were not associated with higher mortality compared with other NSTEACS lesions.

CONCLUSIONS

The 12-lead ECG seems sufficient for triage of patients with LCX lesions as a majority of patients with a large LCX due to a dominant left coronary artery present as STEMI. Patients with LCX-NSTEACS do not have higher mortality compared with patients with LCX-STEMI or NSTEACS with lesions in other coronary territories.

The assessment of ischaemic burden: validation of a functional jeopardy score against cardiovascular magnetic resonance perfusion imaging

AIMS

This study assesses the relationship between classical anatomical jeopardy scores, functional jeopardy scores (combined anatomical and haemodynamic data), and the extent of ischaemia identified on cardiovascular magnetic resonance (CMR) perfusion imaging.

METHODS AND RESULTS

In 42 patients with stable angina and suspected coronary artery disease (CAD), CMR perfusion imaging was performed. Fractional Flow Reserve (FFR) was measured in vessels with ≥50 % stenosis. The APPROACH and BCIS jeopardy scores were calculated based on QCA results with both a 70 % (APP₇₀ and BCIS₇₀) and a 50 % stenosis (APP₅₀, and BCIS₅₀) used as the threshold for significance, as well as after integration of FFR and compared with the extent of ischaemia identified on CMR. The correlation between the extent of ischaemia measured by CMR and the anatomical jeopardy scores was moderate (APPROACH: r = 0.58; BCIS: r = 0.48, p = 0.001). Integrating physiological information improved this significantly to r = 0.82, p = 0.0001 for APPROACH and r = 0.82, p = 0.0001 for BCIS scores (z-statistic = -2.04, p = 0.04; z-statistic = -2.63, p = 0.009). In relation to CMR, the APPROACH and BCIS scores overestimated the volume of ischaemic myocardium by 29.2 and 25.2 %, respectively, which was reduced to 12.8 and 12 % after integrating functional data.

CONCLUSIONS

Anatomical and functional jeopardy scores overestimate ischaemic burden when compared to CMR. Integrating physiological information from FFR to generate a functional score improves ischaemic burden estimation.

Multi-vendor, multicentre comparison of contrast-enhanced SSFP and T2-STIR CMR for determining myocardium at risk in ST-elevation myocardial infarction

AIMS

Myocardial salvage, determined by cardiac magnetic resonance imaging (CMR), is used as end point in cardioprotection trials. To calculate myocardial salvage, infarct size is related to myocardium at risk (MaR), which can be assessed by T2-short tau inversion recovery (T2-STIR) and contrast-enhanced steady-state free precession magnetic resonance imaging (CE-SSFP). We aimed to determine how T2-STIR and CE-SSFP perform in determining MaR when applied in multicentre, multi-vendor settings.

METHODS AND RESULTS

A total of 215 patients from 17 centres were included after percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction. CMR was performed within 1-8 days. These patients participated in the MITOCARE or CHILL-MI cardioprotection trials. Additionally, 8 patients from a previous study, imaged 1 day post-CMR, were included. Late gadolinium enhancement, T2-STIR, and CE-SSFP images were acquired on 1.5T MR scanners (Philips, Siemens, or GE). In 65% of the patients, T2-STIR was of diagnostic quality compared with 97% for CE-SSFP. In diagnostic quality images, there was no difference in MaR by T2-STIR and CE-SSFP (bias: 0.02 ± 6%, P = 0.96, r(2) = 0.71, P < 0.001), or between treatment and control arms. No change in size or quality of MaR nor ability to identify culprit artery was seen over the first week after the acute event (P = 0.44).

CONCLUSION

In diagnostic quality images, T2-STIR and CE-SSFP provide similar estimates of MaR, were constant over the first week, and were not affected by treatment. CE-SSFP had a higher degree of diagnostic quality images compared with T2 imaging for sequences from two out of three vendors. Therefore, CE-SSFP is currently more suitable for implementation in multicentre, multi-vendor clinical trials.

Early afterdepolarizations promote transmural reentry in ischemic human ventricles with reduced repolarization reserve

AIMS

Acute ischemia is a major cause of sudden arrhythmic death, further promoted by potassium current blockers. Macro-reentry around the ischemic region and early afterdepolarizations (EADs) caused by electrotonic current have been suggested as potential mechanisms in animal and isolated cell studies. However, ventricular and human-specific arrhythmia mechanisms and their modulation by repolarization reserve remain unclear. The goal of this paper is to unravel multiscale mechanisms underlying the modulation of arrhythmic risk by potassium current (IKr) block in human ventricles with acute regional ischemia.

METHODS AND RESULTS

A human ventricular biophysically-detailed model, with acute regional ischemia is constructed by integrating experimental knowledge on the electrophysiological ionic alterations caused by coronary occlusion. Arrhythmic risk is evaluated by determining the vulnerable window (VW) for reentry following ectopy at the ischemic border zone. Macro-reentry around the ischemic region is the main reentrant mechanism in the ischemic human ventricle with increased repolarization reserve due to the ATP-sensitive potassium current (IK(ATP)) activation. Prolongation of refractoriness by 4% caused by 30% IKr reduction counteracts the establishment of macro-reentry and reduces the VW for reentry (by 23.5%). However, a further decrease in repolarization reserve (50% IKr reduction) is less anti-arrhythmic despite further prolongation of refractoriness. This is due to the establishment of transmural reentry enabled by electrotonically-triggered EADs in the ischemic border zone. EADs are produced by L-type calcium current (ICaL) reactivation due to prolonged low amplitude electrotonic current injected during the repolarization phase.

CONCLUSIONS

Electrotonically-triggered EADs are identified as a potential mechanism facilitating intramural reentry in a regionally-ischemic human ventricles model with reduced repolarization reserve.

Reproducibility and clinical potential of myocardial mass at risk calculated by a novel software utilizing cardiac computed tomography information

To select the best revascularization strategy a correct understanding of the ischemic territory and the coronary anatomy is crucial. Stress myocardial perfusion single photon emission computed tomography (SPECT) is the gold standard to assess ischemia, however, SPECT has important limitations such as lack of coronary anatomical information or false negative results due to balanced ischemia in multi-vessel disease. Angiographic scores are based on anatomical characteristics of coronary arteries but they lack information on the extent of jeopardized myocardium. Cardiac computed tomography (CCT) has the ability to evaluate the coronary anatomy and myocardium in one sequence, which is theoretically the ideal method to assess the myocardial mass at risk (MMAR) for any target lesion located at any point in the coronary tree. In this study we analyzed MMAR of the three main coronary arteries and three major side branches; diagonal (Dx), obtuse marginal (OM), and posterior descending artery (PDA) in 42 patients with normal coronary arteries using an algorithm based on the Voronoi method. The distribution of MMAR among the three main coronary arteries was 44.3 ± 5.6 % for the left anterior descending artery, 28.2 ± 7.3 % for the left circumflex artery, and 26.8 ± 8.6 % for the right coronary artery. MMAR of the three major side branches was 11.3 ± 3.9 % for the Dx, 12.6 ± 5.2 % for the OM and 10.2 ± 3.4 % for the PDA. Intra- and inter-observer analysis showed excellent correlation (r = 0.97; p < 0.0001 and r = 0.95; p < 0.0001, respectively). In conclusion, CCT-based MMAR assessment is reliable and may offer important information for selection of the optimal revascularization procedure.

Quantitative T2 mapping after reperfusion therapy in patients with acute myocardial infarction: A comparison with late gadolinium enhancement and cine MR imaging

PURPOSE

This study evaluates myocardial edema by quantitative T2 mapping in patients with acute myocardial infarction (AMI) and compares the lateral extent of myocardial edema with those of infarcted and dysfunctional myocardium.

MATERIALS AND METHODS

Cardiac magnetic resonance images (MRIs) of 31 patients (M:F=29:2, mean age: 52.5±10.8years) with AMI were reviewed. On cine-MRI, all short axis images of the left ventricle (LV) were divided into 60 sectors. The regional wall motion of each sector was calculated as follows: systolic wall thickening (SWT, %)=[(LV wall thicknessES-LV wall thicknessED)/LV wall thicknessED]*100. Dysfunctional myocardium was defined as sectors with decreased SWT lower than 40%. On LGE-images, myocardial infarction was defined as an area of hyper-enhancement more than 5 SDs from the remote myocardium. On T2 map, myocardial edema was defined as an area in which T2 values were at least 2 SDs higher than those from remote myocardium. The lateral extents of infarcted myocardium, myocardial edema, and dysfunctional myocardium were calculated as the percentage of central angles ((central angle of the involved myocardium/360)*100 (%)) and then compared.

RESULTS

The lateral extent of myocardial edema was slightly larger than that of infarcted myocardium (37.4±13.3% vs. 35±12.9%, p<0.01). The lateral extent of dysfunctional myocardium (50.6±15.3%) was significantly larger than that of infarcted myocardium or myocardial edema (p<0.001).

CONCLUSIONS

The lateral extent of myocardial edema beyond the infarcted myocardium might be narrow, but the dysfunctional myocardium could be significantly larger than myocardial edema, suggesting stunned myocardium without edema.

Relationship of T2-Weighted MRI Myocardial Hyperintensity and the Ischemic Area-At-Risk

RATIONALE

After acute myocardial infarction (MI), delineating the area-at-risk (AAR) is crucial for measuring how much, if any, ischemic myocardium has been salvaged. T2-weighted MRI is promoted as an excellent method to delineate the AAR. However, the evidence supporting the validity of this method to measure the AAR is indirect, and it has never been validated with direct anatomic measurements.

OBJECTIVE

To determine whether T2-weighted MRI delineates the AAR.

METHODS AND RESULTS

Twenty-one canines and 24 patients with acute MI were studied. We compared bright-blood and black-blood T2-weighted MRI with images of the AAR and MI by histopathology in canines and with MI by in vivo delayed-enhancement MRI in canines and patients. Abnormal regions on MRI and pathology were compared by (a) quantitative measurement of the transmural-extent of the abnormality and (b) picture matching of contours. We found no relationship between the transmural-extent of T2-hyperintense regions and that of the AAR (bright-blood-T2: r=0.06, P=0.69; black-blood-T2: r=0.01, P=0.97). Instead, there was a strong correlation with that of infarction (bright-blood-T2: r=0.94, P<0.0001; black-blood-T2: r=0.95, P<0.0001). Additionally, contour analysis demonstrated a fingerprint match of T2-hyperintense regions with the intricate contour of infarcted regions by delayed-enhancement MRI. Similarly, in patients there was a close correspondence between contours of T2-hyperintense and infarcted regions, and the transmural-extent of these regions were highly correlated (bright-blood-T2: r=0.82, P<0.0001; black-blood-T2: r=0.83, P<0.0001).

CONCLUSION

T2-weighted MRI does not depict the AAR. Accordingly, T2-weighted MRI should not be used to measure myocardial salvage, either to inform patient management decisions or to evaluate novel therapies for acute MI.

Integrated FDG PET/MR Imaging for the Assessment of Myocardial Salvage in Reperfused Acute Myocardial Infarction

PURPOSE

To compare the size of the area with reduced myocardial fluorodeoxygluose (FDG) uptake with the endocardial surface area (ESA) method as a marker for the area at risk in patients with reperfused acute myocardial infarction.

MATERIALS AND METHODS

The study was approved by the local institutional review board. All patients gave written informed consent prior to their examination. Twenty-five patients (mean age ± standard deviation, 54 years ± 14) underwent prospective cardiac positron emission tomography/magnetic resonance imaging after acute coronary occlusion and interventional reperfusion. On late gadolinium contrast enhancement images, the size of infarction and the area at risk, as determined with ESA, were assessed and compared with the area of reduced FDG uptake. Statistical analysis comprised paired t tests and Mann-Whitney U tests, as well as Pearson r and Spearman ρ for correlations.

RESULTS

In patients with infarcted myocardium and reduced FDG uptake (n = 18), a good correlation between the area of reduced FDG uptake and the area at risk according to ESA was observed (r = .70, P = .001). The area of reduced FDG uptake (31% ± 11 of left ventricular myocardial mass) was larger than the size of the infarct (10% ± 10, P < .0001) and the area at risk according to ESA (17% ± 13, P < .0001). In six patients, no late contrast enhancement was seen, whereas all patients had an area of reduced FDG uptake (29% ± 8) in the perfusion territory of the culprit artery.

CONCLUSION

In patients with reperfused acute myocardial infarction, the area of reduced FDG uptake correlates with the area at risk as determined with the ESA method and is localized in the perfusion territory of the culprit artery in the absence of necrosis, although the area of reduced FDG uptake largely overestimates the size of the infarct and the ESA-based area at risk.

The ASLA Score: A CT Angiographic Index to Predict Functionally Significant Coronary Stenoses in Lesions with Intermediate Severity-Diagnostic Accuracy

PURPOSE

To identify computed tomographic (CT) coronary indexes independently associated with a fractional flow reserve (FFR) of 0.8 or less, to derive a score that combines CT indexes most predictive of an FFR of 0.8 or less, and to evaluate the diagnostic accuracy of the score in predicting an FFR of 0.8 or less.

MATERIALS AND METHODS

This retrospective study had institutional review board approval and waiver of the need to obtain informed consent. Consecutive patients who underwent CT coronary angiography and FFR assessment with one or more discrete lesion(s) of intermediate (30%-70%) severity at CT were included. Quantitative CT measurements were performed by using dedicated software. The CT indexes evaluated included the following: plaque burden, minimal luminal area and diameter, stenosis diameter, area of stenosis, lesion length, remodeling index, plaque morphology, calcification severity, and the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) score, which approximates the size of the myocardium subtended by a lesion. By using covariates independently associated with an FFR of 0.8 or less, a score was determined on the basis of modified Akaike information criteria, and the C statistics of individual and combined indexes were compared.

RESULTS

Eighty-five patients (mean age, 64.2 years; range, 48-88 years; 65.9% men; 124 lesions; 38 lesions with an FFR ≤ 0.8) were included. Area of stenosis, lesion length, and APPROACH score were the strongest predictors of an FFR of 0.8 or less and were used to derive the ASLA score. The optimism-adjusted Harrell C statistic for the combined score was 0.82, which was superior to that for area of stenosis (0.74), lesion length (0.75), and the APPROACH score (0.71) (P < .001 for trend). The corresponding incremental discrimination improvement indexes were 0.17, 0.11, and 0.19, respectively (P < .001 for all), suggesting that the score improves reclassification compared with any one angiographic index. The average time required for score derivation was 102.6 seconds.

CONCLUSION

The ASLA score, which accounts for CT-derived area of stenosis, lesion length, and APPROACH score, may conveniently improve the prediction, beyond individual indexes, of functionally significant intermediate coronary lesions.

The direct incorporation of perfusion defect information to define ischemia and infarction in a finite element model of the left ventricle

This paper describes the process in which complex lesion geometries (specified by computer generated perfusion defects) are incorporated in the description of nonlinear finite element (FE) mechanical models used for specifying the motion of the left ventricle (LV) in the 4D extended cardiac torso (XCAT) phantom to simulate gated cardiac image data. An image interrogation process was developed to define the elements in the LV mesh as ischemic or infarcted based upon the values of sampled intensity levels of the perfusion maps. The intensity values were determined for each of the interior integration points of every element of the FE mesh. The average element intensity levels were then determined. The elements with average intensity values below a user-controlled threshold were defined as ischemic or infarcted depending upon the model being defined. For the infarction model cases, the thresholding and interrogation process were repeated in order to define a border zone (BZ) surrounding the infarction. This methodology was evaluated using perfusion maps created by the perfusion cardiac-torso (PCAT) phantom an extension of the 4D XCAT phantom. The PCAT was used to create 3D perfusion maps representing 90% occlusions at four locations (left anterior descending (LAD) segments 6 and 9, left circumflex (LCX) segment 11, right coronary artery (RCA) segment 1) in the coronary tree. The volumes and shapes of the defects defined in the FE mechanical models were compared with perfusion maps produced by the PCAT. The models were incorporated into the XCAT phantom. The ischemia models had reduced stroke volume (SV) by 18-59 ml. and ejection fraction (EF) values by 14-50% points compared to the normal models. The infarction models, had less reductions in SV and EF, 17-54 ml. and 14-45% points, respectively. The volumes of the ischemic/infarcted regions of the models were nearly identical to those volumes obtained from the perfusion images and were highly correlated (R² = 0.99).

The origin of monitoring of acute myocardial infarction with continuous vectorcardiography

The continuous change of the ST and QRS vectorcardiograms reflect the underlying ischemic event, and can be used as a tool in the management of the acute event. It also reflects reperfusion, and can guide the clinician on when and how to intervene. Continuous vectorcardiography has proven to add prognostic information, both in the acute phase (can be used already in the ambulance during transportation to CCU) and after discharge from hospital. This paper reviews the origin of continous vectorcardiography as a monitoring device in AMI, including the follow-up research until today.

Impact of myocardial supply area on the transstenotic hemodynamics as determined by fractional flow reserve

OBJECTIVES

The aim of this study was to investigate the impact of myocardial area supplied by the coronary artery on fractional flow reserve (FFR).

BACKGROUND

Various factors other than the degree of epicardial stenosis influence the physiological significance of a coronary artery stenosis.

METHODS

A total of 296 coronary lesions in 217 patients were analyzed by quantitative coronary angiography and FFR. Myocardial area supplied by the coronary artery distal to the stenosis was evaluated by angiography using a modified version of the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) score.

RESULTS

Percent diameter stenosis of the coronary lesion was 57 ± 15% (mean ± standard deviation). FFR <0.80 was seen in 132 (45%) lesions. FFR was significantly correlated with minimum lumen diameter (r = 0.584, P <0.001), percent diameter stenosis (r = -0.565, P <0.001), lesion length (r = -0.306, P <0.001), and myocardial supply area (r = -0.504, P <0.001). Multivariate logistic analysis demonstrated that minimum lumen diameter (odds ratio [OR] = 0.031, 95% confidence interval [CI] = 0.013-0.076, P < 0.001), lesion length (OR = 1.038, 95% CI = 1.009-1.069, P = 0.001), and myocardial supply area (OR = 1.113, 95% CI = 1.079-1.147, P <0.001) were independent determinants for FFR <0.80.

CONCLUSIONS

FFR, which is the index of physiological significance of coronary artery stenosis, is influenced by myocardial supply area distal to the stenosis as well as by its own minimal lumen diameter and lesion length.

Relationship between fragmented QRS and no-reflow, infarct size, and peri-infarct zone assessed using cardiac magnetic resonance in patients with myocardial infarction

BACKGROUND

The relation between fragmented QRS complex (fQRS) and cardiac magnetic resonance parameters is poorly documented in ischemic cardiopathy.

METHODS

Among 209 consecutive patients, those with fQRS were compared with those without fQRS. Cardiac magnetic resonance studies with late gadolinium-enhanced sequences were done during the week after acute myocardial infarction.

RESULTS

fQRS was present in 113 (54%) patients, and associated with a significantly lower left ventricular ejection fraction, increased left ventricular volumes, a larger infarct size (IS), and a larger peri-infarct zone. Microvascular obstruction was more frequent in patients with fQRS (62% vs 45%; P = 0.014) and the extent of the microvascular obstruction was significantly larger (1.6% [range, 0.0-4.4] vs 0.0 [range, 0.0-2.1]; P = 0.004). Finally, the transmurality score in the 2 study populations was identical (48% vs 47%; P = 0.895). In multivariate logistic regression analysis, only IS (odds ratio [OR], 1.06; 95% confidence interval [CI], 1.03-1.09; P < 0.001), systolic blood pressure (OR, 1.02; 95% CI, 1.01-1.04; P < 0.001), and left ventricular end-systolic volume (OR, 1.02; 95% CI, 1.00-1.03; P = 0.013) remained independent predictors of fQRS.

CONCLUSIONS

This study revealed that fQRS was associated with increased IS, myocardial perfusion abnormalities, decreased left ventricular ejection fraction, and increased left heart volumes. These findings show that fQRS is a reliable marker of infarct size and acute ventricular remodelling.

Quantification of myocardial area at risk in the absence of collateral flow: the validation of angiographic scores by myocardial perfusion single-photon emission computed tomography

OBJECTIVES

Our study aimed to compare the area at risk (AAR) determined by single-photon emission computed tomography (SPECT) with the Bypass Angioplasty Revascularization Investigation (BARI) and modified Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) angiographic scores in the setting of patients undergoing coronary angioplasty for either unstable angina or an STEMI.

BACKGROUND

Radionuclide myocardial perfusion imaging prior to reperfusion has classically been the most widely practised technique for assessing the AAR and has been successfully used to compare the efficacy of various reperfusion strategies in patients with an ST-segment elevation myocardial infarction (STEMI). The BARI and modified APPROACH scores are angiographic methods widely used to provide a rapid estimation of the AAR; however, they have not been directly validated with myocardial perfusion single-photon emission computed tomography (SPECT).

METHODS

Fifty-five patients with no previous myocardial infarction who underwent coronary angioplasty for single-vessel disease (unstable angina: n = 25 or an STEMI: n = 30) with no evidence of collaterals (Rentrop Collateral Score <2) were included in a prospective study. In STEMI patients, the (99m)Tc-tetrofosmin was injected prior to opening of the occluded vessel and, in patients with unstable angina after 10-15 seconds of balloon inflation. Acquisition was performed with a dual-head gammacamera with a low-energy and high-resolution collimator. A total of 60 projections were acquired using a non-circular orbit. No attenuation or scatter correction was used. Maximal contours of hypoperfusion regions corresponding to each coronary artery occlusion were delineated over a polar map of 17 segments and compared with the estimated AAR determined by two experienced interventional cardiologists using both angiographic scores.

RESULTS

Mean AAR percentage in SPECT was 35.0 (10.0%-56.0%). A high correlation was found between BARI and APPROACH scores (r = 0.9, P < .001). Furthermore, a high correlation was also observed between BARI versus SPECT and APPROACH versus SPECT to estimate the AAR (r = 0.9, P < .001 and r = 0.8, P < .001, respectively). Better correlations were observed when the left anterior descending artery (LAD) was revascularized (r = 0.8, P < 0.001 with BARI; r = 0.8, P = .001 with APPROACH) compared to other territories (r = 0.8, P = .001 with BARI; r = 0.7, P = .001 with APPROACH). Also, better correlations were observed in patients who underwent an elective rather than a primary percutaneous revascularization procedure.

CONCLUSIONS

In the absence of collateral flow, BARI and APPROACH scores constitute valid methods for AAR estimation in current clinical practice, with more accurate results when used for the LAD territory; both are useful not only in STEMI patients but also in patients with unstable angina.

Controversies in cardiovascular MR imaging: T2-weighted imaging should not be used to delineate the area at risk in ischemic myocardial injury

The use of T2-weighted MR imaging to delineate the area at risk and subsequently quantify myocardial salvage is problematic on many levels. The validation studies available thus far are inadequate. Unlike the data validating DE MR imaging, in which pathologic analysis has shown the precise shape and contour of the bright region exactly match the infarcted area, this level of validation does not exist for T2-weighted MR imaging. Technical advances have occurred, but image contrast between abnormal and normal regions remains limited, and in this situation, measured size differences between MR imaging data sets should not be overinterpreted. Moreover, with any T2 technique, there remains the key issue that there is no physiologic basis for the apparent T2 findings. Indeed, a homogeneously bright area at risk on T2-weighted MR images is incompatible with the known levels of edema that occur in infarcted and salvaged myocardium, and the finding that the lateral borders of T2 hyperintense regions frequently extend far beyond that of infarction is contrary to the wavefront phenomenon. Even if T2-weighted MR imaging provided an accurate measure of myocardial edema, the level of edema within the area at risk is dependent on multiple variables, including infarct size, age, reperfusion status, reperfusion injury, and therapies that could have an antiedema effect. The area at risk is a coronary perfusion territory. There is a fundamental limitation with defining the area at risk by using a nonperfusion-based indicator that can vary with different postreperfusion therapies. There are several applications for T2 myocardial imaging, including differentiation of acute from chronic MI and identification of acute myocarditis. On the basis of the currently available data; however, we conclude that T2-weighted MR imaging should not be used to delineate the area at risk in patients with ischemic myocardial injury.

Myocardium at risk can be determined by ex vivo T2-weighted magnetic resonance imaging even in the presence of gadolinium: comparison to myocardial perfusion single photon emission computed tomography

AIMS

Determination of the myocardium at risk (MaR) and final infarct size by cardiac magnetic resonance imaging (CMR) enables calculation of salvaged myocardium in acute infarction. T2-weighted imaging is performed prior to the administration of gadolinium, since gadolinium affects T2 tissue properties. This is, however, difficult in an ex vivo model since gadolinium must be administered for determination of infarct size by CMR. We aimed to test the ability of ex vivo T2-weighted imaging to assess MaR using myocardial perfusion single photon emission computed tomography (SPECT) as reference and to investigate whether MaR could be assessed by ex vivo T2-weighted imaging after injection of gadolinium. Materials and methods In 18 domestic pigs, the left anterior descending artery was occluded for either 30 or 40 min, followed by 4 h of reperfusion. After explantation of the hearts, myocardial perfusion SPECT and T2-weighted imaging were performed for determination of MaR, either with or without gadolinium. Infarct size was determined by T1-weighted imaging and by triphenyl tetrazolium chloride (TTC) staining.

RESULTS

T2-weighted imaging agreed with myocardial perfusion SPECT, both with and without gadolinium (r(2)= 0.70, P < 0.01) with a bias of 2.6 ± 5.1% (P = 0.04). Infarct size was 15.4 ± 5.3 and 22.1 ± 5.6% with TTC and T1-weighted imaging, respectively (P = 0.008) in nine pigs who had both infarct measures.

CONCLUSION

T2-weighted CMR imaging can be used to determine MaR in an ex vivo experimental model, both with and without the presence of gadolinium. Thus, CMR alone can be used to assess myocardial salvage in experimental studies.

Myocardium at risk by magnetic resonance imaging: head-to-head comparison of T2-weighted imaging and contrast-enhanced steady-state free precession

AIMS

To determine the myocardial salvage index, the extent of infarction needs to be related to the myocardium at risk (MaR). Thus, the ability to assess both infarct size and MaR is of central clinical and scientific importance. The aim of the present study was to explore the relationship between T2-weighted cardiac magnetic resonance (CMR) and contrast-enhanced steady-state free precession (CE-SSFP) CMR for the determination of MaR in patients with acute myocardial infarction.

METHODS AND RESULTS

Twenty-one prospectively included patients with first-time ST-elevation myocardial infarction underwent CMR 1 week after primary percutaneous coronary intervention. For the assessment of MaR, T2-weighted images were acquired before and CE-SSFP images were acquired after the injection of a gadolinium-based contrast agent. For the assessment of infarct size, late gadolinium enhancement images were acquired. The MaR by T2-weighted imaging and CE-SSFP was 29 ± 11 and 32 ± 12% of the left ventricle, respectively. Thus, the MaR with T2-weighted imaging was slightly smaller than that by CE-SSFP (-3.0 ± 4.0%; P < 0.01). There was a significant correlation between the two MaR measures (r(2)= 0.89, P < 0.01), independent of the time after contrast agent administration at which the CE-SSFP was commenced (2-8 min).

CONCLUSION

There is a good agreement between the MaR assessed by T2-weighted imaging and that assessed by CE-SSFP in patients with reperfused acute myocardial infarction 1 week after the acute event. Thus, both methods can be used to determine MaR and myocardial salvage at this point in time.

Left circumflex occlusion in acute myocardial infarction (from the National Cardiovascular Data Registry)

Compared to occlusions of other major coronary arteries, patients presenting with acute left circumflex (LCx) occlusion usually have ST-segment elevation on the electrocardiogram <50% of the time, potentially delaying treatment and resulting in worse outcomes. In contemporary practice, little is known about the clinical outcomes of patients with LCx territory occlusion without ST-segment elevation myocardial infarction (STEMI). We identified patients with myocardial infarction from April 2004 to June 2009 in the CathPCI Registry treated with percutaneous coronary intervention for culprit LCx territory occlusion, excluding those with previous coronary artery bypass grafting. Logistic generalized estimating equation modeling was used to compare the outcomes, including in-hospital mortality between patients with STEMI and non-STEMI (NSTEMI) adjusting for differences in the baseline characteristics. Of the 27,711 patients with myocardial infarction and acute LCx territory occlusion, 18,548 (67%) presented with STEMI and 9,163 (33%) with NSTEMI. With the exception of a greater proportion of cardiac risk factors and cardiac history in the NSTEMI group, the demographic and baseline characteristics were clinically similar between the 2 groups, despite the statistical significance resulting from the large population. The patients with STEMI were more likely to have a proximal LCx culprit lesion (63% vs 27%, p <0.0001) and had greater risk-adjusted in-hospital mortality (odds ratio 1.36, 95% confidence interval 1.12 to 1.65, p = 0.002) compared to patients with NSTEMI. In conclusion, acute LCx territory occlusion often presents as NSTEMI, but patients with NSTEMI and occlusion have a lower mortality risk than those with STEMI, possibly because of factors such as the amount of myocardium involved, the lesion location along the vessel, and/or a dual blood supply.

Prognostic significance and determinants of myocardial salvage assessed by cardiovascular magnetic resonance in acute reperfused myocardial infarction

OBJECTIVES

The aim of the study was to determine the prognostic significance and determinants of myocardial salvage assessed by cardiovascular magnetic resonance (CMR) in reperfused ST-segment elevation myocardial infarction.

BACKGROUND

In acute myocardial infarction, CMR can retrospectively detect the myocardium at risk and the irreversible injury. This allows for quantifying the extent of salvaged myocardium after reperfusion as a potential strong end point for clinical trials and outcome.

METHODS

We analyzed 208 consecutive ST-segment elevation myocardial infarction patients undergoing primary angioplasty <12 h after symptom onset. T2-weighted and contrast-enhanced CMR was used to calculate the myocardial salvage index (MSI). Patients were categorized into 2 groups defined by the median MSI. The primary end point of the study was occurrence of major adverse cardiovascular events defined as death, reinfarction, and occurrence of new congestive heart failure within 6 months after the index event.

RESULTS

The median MSI was 48 (interquartile range 27 to 73). Major adverse cardiovascular events were significantly lower in the MSI >or= median group (2.9% vs. 22.1%, p < 0.001). The stepwise Cox proportional hazards model revealed that the MSI was the strongest predictor of major adverse cardiovascular events at 6-month follow-up (p < 0.001). All prognostic clinical (symptom onset to reperfusion), angiographic (Thrombolysis In Myocardial Infarction flow grade before angioplasty), and electrocardiographic (ST-segment resolution) parameters showed significant correlations with the MSI (p < 0.001 for all).

CONCLUSIONS

This study for the first time demonstrates that the MSI assessed by CMR predicts the outcome in acute reperfused ST-segment elevation myocardial infarction. Therefore, MSI assessment has important implications for patient prognosis as well as for the design of future trials intended to test new reperfusion therapy efficacy. (Myocardial Salvage Assessed by Cardiovascular Magnetic Resonance-Impact on Outcome; NCT00952224).

Quantification of myocardial area at risk with T2-weighted CMR: comparison with contrast-enhanced CMR and coronary angiography

OBJECTIVES

We sought to quantify the myocardium at risk in reperfused acute myocardial infarction (AMI) in man with T2-weighted (T2W) cardiac magnetic resonance (CMR).

BACKGROUND

The myocardial area at risk (AAR) is defined as the myocardial tissue within the perfusion bed distally to the culprit lesion of the infarct-related coronary artery. T2W CMR is appealing to retrospectively determine the myocardial AAR after reperfused AMI. Data on the utility of this technique in humans are limited.

METHODS

One hundred eight patients with successfully reperfused ST-segment elevation AMI were studied between 1 and 20 days after percutaneous coronary intervention (PCI). We compared the volume of hyperintense myocardium on T2W CMR with the myocardial AAR determined by contrast-enhanced CMR with infarct endocardial surface length (ESL) and AAR estimated by conventional coronary angiography with the BARI (Bypass Angioplasty Revascularization Investigation) risk score.

RESULTS

The volume of hyperintense myocardium on T2W CMR (mean 32 +/- 16%, range 3% to 67%) was consistently larger than the volume of myocardial infarction measured with contrast-enhanced images (mean 17 +/- 12%, range 0% to 55%) (p < 0.001). Myocardial salvage ranged from -4% to 45% of the left ventricular myocardium (mean 14 +/- 10%). The AAR determined by T2W CMR compared favorably with the infarct ESL (r = 0.77) with contrast-enhanced CMR, and there was moderate correlation between the BARI angiographic risk score and infarct ESL (r = 0.42). The time between PCI and CMR did not cause a significant difference in the volume of T2W hyperintense myocardium (r = 0.11, p = 0.27) or the calculated volume of salvaged myocardium (r = 0.12, p = 0.23).

CONCLUSIONS

T2W CMR performed early after successfully reperfused AMI in humans enables retrospective quantification of the myocardial AAR and salvaged myocardium.

Cardiac MRI of myocardial salvage at the peri-infarct border zones after primary coronary intervention

The purpose of this study was to use cardiac MRI to define the morphology of the reversibly injured peri-infarct border zone in patients treated with primary percutaneous coronary intervention (PPCI) for acute ST elevation myocardial infarction. In 15 patients, T2-weighted myocardial edema imaging was used to identify the ischemic bed or area at risk (AAR), and late gadolinium enhancement imaging was used to measure infarct size. Images were coregistered, and the boundaries of edema and necrosis were defined using an edge-detection methodology. We observed that infarction always involved the subendocardium but showed variable transmural extension within the AAR. The mean infarct size was 22 +/- 19% (range: 8-48%), and the mean AAR was 34 +/- 12% (range: 20-57%). The infarcted myocardium was always smaller than the ischemic AAR and involved between 34% and 99% (mean 72 +/- 21%) of the ischemic bed primarily due to variation in transmural infarct extension. Although a lateral border zone of potentially viable myocardium was often present, its extent was limited (range: 0-11 mm, mean: 5 +/- 4 mm). As a result of this, infarcts occupied the majority (range: 70-100%, mean: 82 +/- 13%) of the width of the AAR. The mean fractional wall thickening in the infarcted, peri-infarcted, and remote myocardium was 3.6 +/- 16.0%, 40.5 +/- 26.4%, and 88.2 +/- 39.3%, respectively. These findings demonstrate that myocardial salvage is largely determined by epicardial limitation of the infarct within the ischemic AAR after PPCI. The lateral boundaries of necrosis approximate to the lateral extent of the ischemic bed and systolic wall motion abnormalities extend well beyond the infarct border zone.