Microvascular obstruction in the right ventricle in reperfused anterior myocardial infarction. Macroscopic and pathologic evidence in a swine model

RIGHT VENTRICLE FUNCTION IN PATIENTS WITH ANTERIOR MYOCARDIAL INFARCTION: ARE WE SURE IT IS NOT INVOLVED?

The right and left ventricle of heart are intimately connected by anatomical and functional links. Hence, acute changes in cardiac geometry and function can modify the performance and physiology of both sides of the heart, influencing each other. After a brief overview of the anatomy and related imaging techniques for the study of right ventricular function, we report a review on the interesting correlation of acute anterior myocardial infarction and right ventricular function, very often underestimated.

Cardiac MRI to Visualize Myocardial Damage after ST-Segment Elevation Myocardial Infarction: A Review of Its Histologic Validation

Cardiac MRI is a noninvasive diagnostic tool using nonionizing radiation that is widely used in patients with ST-segment elevation myocardial infarction (STEMI). Cardiac MRI depicts different prognosticating components of myocardial damage such as edema, intramyocardial hemorrhage (IMH), microvascular obstruction (MVO), and fibrosis. But how do cardiac MRI findings correlate to histologic findings? Shortly after STEMI, T2-weighted imaging and T2* mapping cardiac MRI depict, respectively, edema and IMH. The acute infarct size can be determined with late gadolinium enhancement (LGE) cardiac MRI. T2-weighted MRI should not be used for area-at-risk delineation because T2 values change dynamically over the first few days after STEMI and the severity of T2 abnormalities can be modulated with treatment. Furthermore, LGE cardiac MRI is the most accurate method to visualize MVO, which is characterized by hemorrhage, microvascular injury, and necrosis in histologic samples. In the chronic setting post-STEMI, LGE cardiac MRI is best used to detect replacement fibrosis (ie, final infarct size after injury healing). Finally, native T1 mapping has recently emerged as a contrast material-free method to measure infarct size that, however, remains inferior to LGE cardiac MRI. Especially LGE cardiac MRI-defined infarct size and the presence and extent of MVO may be used to monitor the effect of new therapeutic interventions in the treatment of reperfusion injury and infarct size reduction. © RSNA, 2021 Online supplemental material is available for this article.

Short- and long-term prognostic value of right ventricular function in patients with first acute ST elevation myocardial infarction treated by primary angioplasty

INTRODUCTION

Limited data are known about the prognostic value of right ventricle (RV) function in patients with first acute ST-segment elevation myocardial infarction (STEMI). The aim of this study was to investigate the prognostic value of RV dysfunction in predicting both in-hospital and long-term outcomes in these patients, irrespective of the site of necrosis.

METHODS

We enrolled 502 consecutive patients with first acute STEMI treated with primary angioplasty and underwent echocardiography within 48 hours of admission. RV function was evaluated by RV myocardial performance index (RVMPI), RV fractional area change (RVFAC), tricuspid annular plane systolic excursion (TAPSE), pulsed tissue Doppler S' wave velocity, and RV global longitudinal strain (RVGLS) of the free wall. The occurrence of in-hospital major adverse cardiac events (MACE) and 1-year survival rate were recorded.

RESULTS

In MACE group, RVFAC, TAPSE, and RV S' wave velocity were lower. However, RVMPI, RVGLS, and TR Vmax. were higher than MACE free group (P < .001). In multivariable analysis adjusted for other variables that predicted adverse outcomes, RVFAC < 35% (P < .001), TAPSE < 17 mm (P < .001), RVGLS > -17% (P < .001), RV S' wave velocity < 9.5 cm/s (P = .02), RVMPI > 0.43 (P < .001), and TR Vmax. > 2.8 m/s (P = .01) were strong independent predictors of in-hospital MACE. Lower 1-year survival was noted in patients with RV dysfunction, documented by these cutoffs values.

CONCLUSION

RV dysfunction, evidenced by multiparametric echocardiography, is predictive for adverse in-hospital outcomes, and lower 1-year survival rate in first acute STEMI regardless of the site of necrosis.

Cardioprotective Effect of Novel Matrix Metalloproteinase Inhibitors

Background: We recently developed novel matrix metalloproteinase-2 (MMP-2) inhibitor small molecules for cardioprotection against ischemia/reperfusion injury and validated their efficacy in ischemia/reperfusion injury in cardiac myocytes. The aim of the present study was to test our lead compounds for cardioprotection in vivo in a rat model of acute myocardial infarction (AMI) in the presence or absence of hypercholesterolemia, one of the major comorbidities affecting cardioprotection. Methods: Normocholesterolemic adult male Wistar rats were subjected to 30 min of coronary occlusion followed by 120 min of reperfusion to induce AMI. MMP inhibitors (MMPI)-1154 and -1260 at 0.3, 1, and 3 µmol/kg, MMPI-1248 at 1, 3, and 10 µmol/kg were administered at the 25th min of ischemia intravenously. In separate groups, hypercholesterolemia was induced by a 12-week diet (2% cholesterol, 0.25% cholic acid), then the rats were subjected to the same AMI protocol and single doses of the MMPIs that showed the most efficacy in normocholesterolemic animals were tested in the hypercholesterolemic animals. Infarct size/area at risk was assessed at the end of reperfusion in all groups by standard Evans blue and 2,3,5-triphenyltetrazolium chloride (TTC) staining, and myocardial microvascular obstruction (MVO) was determined by thioflavine-S staining. Results: MMPI-1154 at 1 µmol/kg, MMPI-1260 at 3 µmol/kg and ischemic preconditioning (IPC) as the positive control reduced infarct size significantly; however, this effect was not seen in hypercholesterolemic animals. MVO in hypercholesterolemic animals decreased by IPC only. Conclusions: This is the first demonstration that MMPI-1154 and MMPI-1260 showed a dose-dependent infarct size reduction in an in vivo rat AMI model; however, single doses that showed the most efficacy in normocholesterolemic animals were abolished by hypercholesterolemia. The further development of these promising cardioprotective MMPIs should be continued with different dose ranges in the study of hypercholesterolemia and other comorbidities.

The association of right ventricular dysfunction with in-hospital and 1-year outcomes in anterior myocardial infarction

In anterior ST-segment elevation myocardial infarction (STEMI), attention paid mainly to the left ventricle. The predictive significance of right ventricular (RV) dysfunction in patients with anterior STEMI has been frequently neglected. In this study, we evaluated the prognostic effect of RV dysfunction on in-hospital and long-term outcomes in patients with first anterior STEMI. A total of 350 patients without known coronary artery disease with first anterior STEMI and treated with primary percutaneous coronary intervention were prospectively enrolled in this study. In-hospital and long-term outcomes were compared between two groups of with or without RV dysfunction. In-hospital mortality was significantly higher in the RV dysfunction group (26.7% vs. 1.6%, P < 0.001). The RV dysfunction group also had a higher incidence of cardiogenic shock, recurrent myocardial infarction, target lesion revascularization and stent thrombosis. The 1-year overall survival in patients with and without RV dysfunction was 62.2% and 95.0% respectively. After multivariable analysis, RV dysfunction remained as an independent predictor for in-hospital and long-term mortality. RV dysfunction is an independent predictor of cardiogenic shock, recurrent myocardial infarction, and, in-hospital and long-term mortality in anterior STEMI. Therefore, attention should be paid to the function of right ventricle as in the left ventricle after anterior STEMI.

The Coronary Circulation as a Target of Cardioprotection

The atherosclerotic coronary vasculature is not only the culprit but also a victim of myocardial ischemia/reperfusion injury. Manifestations of such injury are increased vascular permeability and edema, endothelial dysfunction and impaired vasomotion, microembolization of atherothrombotic debris, stasis with intravascular cell aggregates, and finally, in its most severe form, capillary destruction with hemorrhage. In animal experiments, local and remote ischemic pre- and postconditioning not only reduce infarct size but also these manifestations of coronary vascular injury, as do drugs which recruit signal transduction steps of conditioning. Clinically, no-reflow is frequently seen after interventional reperfusion, and it carries an adverse prognosis. The translation of cardioprotective interventions to clinical practice has been difficult to date. Only 4 drugs (brain natriuretic peptide, exenatide, metoprolol, and esmolol) stand unchallenged to date in reducing infarct size in patients with reperfused acute myocardial infarction; unfortunately, for these drugs, no information on their impact on the ischemic/reperfused coronary circulation is available.

Cardiovascular magnetic resonance imaging assessment of outcomes in acute myocardial infarction

Cardiovascular magnetic resonance (CMR) imaging uniquely characterizes myocardial and microvascular injury in acute myocardial infarction (AMI), providing powerful surrogate markers of outcomes. The last 10 years have seen an exponential increase in AMI studies utilizing CMR based endpoints. This article provides a contemporary, comprehensive review of the powerful role of CMR imaging in the assessment of outcomes in AMI. The theory, assessment techniques, chronology, importance in predicting left ventricular function and remodelling, and prognostic value of each CMR surrogate marker is described in detail. Major studies illustrating the importance of the markers are summarized, providing an up to date review of the literature base in CMR imaging in AMI.

Diabetes is an independent predictor of right ventricular dysfunction post ST-elevation myocardial infarction

BACKGROUND

Diabetes mellitus (DM) is estimated to become the 7th leading cause of death by 2030. Right ventricular dysfunction (RVD) complicating ST elevation myocardial infarction (STEMI) is independently associated with a higher mortality; however the relationship between DM and RVD is currently unknown. The purpose of this study was to determine whether DM is an independent predictor for the presence of right ventricular dysfunction (RVD) post STEMI.

METHODS

106 patients post primary PCI for STEMI were enrolled in the study. Cardiac MRI was performed within 48-72 h after admission in order to assess ventricular function. Statistical analysis consisted initially of descriptive statistics including Chi square, Fisher's exact, or the Wilcoxon rank sum as appropriate. Subsequently, logistic regression analysis was performed to determine independent predictors of RVD.

RESULTS

The median age in the study was 58 years (IQR 53, 67). 30 % of the patients had diabetes. Of 99 patients for which RV data was available, 40 had RVD and 59 did not. Patients with DM were significantly more likely to have RVD when compared to those without diabetes (45 vs 22 %, p = 0.03). There was no significant difference in age, hypertension, smoking status, dyslipidemia, serum creatinine or peak CK levels between the two groups. After adjusting for other factors, presence of DM remained an independent predictor for the presence of RV dysfunction (OR 2.78, 95 % CI 1.12, 6.87, p = 0.03). Amongst diabetic patients, those with HbA1C ≥ 7 % had greater odds of having RVD vs those with HbA1C < 7 % (OR 5.58 (1.20, 25.78), p = 0.02).

CONCLUSIONS

The presence of DM conferred an approximately threefold greater odds of being associated with RVD post STEMI. No other major cardiovascular risk factors were independently associated with the presence of RVD.