Myocardial infarction with angiographically normal coronary arteries

Interleukin-36 is vasculoprotective in both sexes despite sex-specific changes in the coronary microcirculation response to IR injury

Aims

Risks and outcomes of myocardial infarction (MI) are different between men and women and some studies have demonstrated that the latter have a higher risk of mortality. Whilst there are many reasons for this, it may also partially be linked to stronger innate and adaptive immune responses mounted by females compared to males. However, little is known about how sex impacts the coronary microvessels, the site where inflammatory processes take place, after an MI. Intravital and laser speckle microscopy was used to image coronary microvessels and ventricular perfusion in vivo in response to myocardial ischaemia-reperfusion (IR) injury in male and female mice. Interleukin-36 (IL-36) is the latest addition to the IL-1 superfamily of pro-inflammatory cytokines and has recently been shown to mediate inflammation in a number of non-cardiovascular diseases. Its role in mediating potential sex-related microcirculatiory pertubations in the heart are unknown. Therefore, the vasculoprotective efficacy of an IL-36 receptor antagonist (IL-36Ra) was also investigated.

Methods and results

Immunostaining and flow cytometry demonstrated higher expression of IL-36 and its receptor in female hearts, an observation confirmed in human samples. Intravital imaging of the anaesthetised mouse beating heart identified significantly greater neutrophil recruitment in female hearts, but a greater burden of thrombotic disease in male hearts. Male mice had reduced functional capillary density and were unable to restore perfusion to baseline values as effectively as females. However, female mice had significantly larger infarcts. Interestingly, IL-36Ra decreased inflammation, improved perfusion, and reduced infarct size in both sexes despite increasing platelet presence in male hearts. Mechanistically, this was explained by IL-36Ra attenuating endothelial oxidative damage and VCAM-1 expression. Importantly, IL-36Ra administration during ischaemia was critical for vasculoprotection to be realised.

Conclusion

This novel study identified notable sex-related differences in the coronary microcirculatory response to myocardial IR injury which may explain why some studies have noted poorer outcomes in women after MI. Whilst contemporary MI treatment focuses on anti-platelet strategies, the heightened presence of neutrophils in female IR injured coronary microvessels necessitates the development of an effective anti-inflammatory approach for treating female patients. We also emphasise the importance of early intervention during the ischaemic period in order to maximise therapeutic effectiveness.

Diffuse LAD and LV Thrombus as Possible Manifestation of Protein-S Deficiency in a Young Patient

Patients with inherited hypercoagulopathies such as protein-S deficiency commonly present with venous thrombosis. However, there are rare cases of arterial thrombosis. We describe a rare case of a diffuse left anterior descending and left ventricular thrombus in a young patient with protein-S deficiency complicated with mid cerebral artery occlusion. (Level of Difficulty: Intermediate.).

Targeting IL-36 improves age-related coronary microcirculatory dysfunction and attenuates myocardial ischaemia-reperfusion injury in mice

Following myocardial infarction (MI), elderly patients have a poorer prognosis than younger patients, which may be linked to increased coronary microvessel susceptibility to injury. Interleukin-36 (IL-36), a newly discovered proinflammatory member of the IL-1 superfamily, may mediate this injury, but its role in the injured heart is currently not known. We first demonstrated the presence of IL-36(α/β) and its receptor (IL-36R) in ischemia/reperfusion-injured (IR-injured) mouse hearts and, interestingly, noted that expression of both increased with aging. An intravital model for imaging the adult and aged IR-injured beating heart in real time in vivo was used to demonstrate heightened basal and injury-induced neutrophil recruitment, and poorer blood flow, in the aged coronary microcirculation when compared with adult hearts. An IL-36R antagonist (IL-36Ra) decreased neutrophil recruitment, improved blood flow, and reduced infarct size in both adult and aged mice. This may be mechanistically explained by attenuated endothelial oxidative damage and VCAM-1 expression in IL-36Ra–treated mice. Our findings of an enhanced age-related coronary microcirculatory dysfunction in reperfused hearts may explain the poorer outcomes in elderly patients following MI. Since targeting the IL-36/IL-36R pathway was vasculoprotective in aged hearts, it may potentially be a therapy for treating MI in the elderly population.

Non-traditional risk factors and the risk of myocardial infarction in the young in the US population-based cohort

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Young patients with myocardial infarction (MI) have both traditional risk factors and non-traditional risk factors.

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HTN, smoking, obesity, HLD and a family history of CAD were risks of MI in the young.

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HIV, SLE, and OSA were all associated with an elevated risk of MI, independent of traditional atherosclerotic risk factors.

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Close attention should be paid to emerging risk factors such as SLE, HIV and OSA.

Although most prevalent in elderly, myocardial infarction (MI) also affects younger adults. We sought to investigate baseline characteristics in young patients (<55 years) with MI using the National Inpatient Sample (NIS) database between 2004 and 2015. Multivariable logistic regression models were used to assess factors associated with acute myocardial infarction (AMI) in young patients. After multivariable analyses adjusted for age, sex, race, family history of atherosclerosis, body mass index (BMI), diabetes, hypertension, hyperlipidemia, chronic kidney disease, and current cigarette smoking; novel risk factors such as human immunodeficiency virus (HIV), systemic lupus erythematosus (SLE), and obstructive sleep apnea (OSA) were associated with a higher risk of developing an AMI in the young (adjusted OR for HIV 4.06; 95 CI 3.48–4.71, p < 0.001), (adjusted OR for SLE 2.12; 95 CI 1.89–2.39, p 0.04), and (adjusted OR for OSA 1.16; 95 CI 1.12–1.20, p < 0.001), respectively. Rheumatoid arthritis was associated with a lower risk of AMI (adjusted OR 0.83; 95 CI 0.76–0.89, p < 0.001). After multivariable analyses, cigarette smoking (adjusted OR 1.98; 95 CI 1.95–2.02, p < 0.001), obesity (adjusted OR 1.37; 95 CI 1.33–1.41, p = 0.003), hyperlipidemia (adjusted OR 1.07; 95 CI 1.04–1.08, p < 0.001) and a family history of CAD (adjusted OR 1.35; 95 CI 1.3–1.4, p < 0.001) were also associated with a higher risk of developing an AMI in the young. In conclusion, young patients with AMI have both traditional risk factors and non-traditional risk factors. In addition to traditional risk factors, close attention should be paid to emerging risk factors such as SLE, HIV and OSA.

Imaging the injured beating heart intravitally and the vasculoprotection afforded by haematopoietic stem cells

Aims

Adequate microcirculatory perfusion, and not just opening of occluded arteries, is critical to salvage heart tissue following myocardial infarction. However, the degree of microvascular perfusion taking place is not known, limited primarily by an inability to directly image coronary microcirculation in a beating heart in vivo. Haematopoietic stem/progenitor cells (HSPCs) offer a potential therapy but little is known about their homing dynamics at a cellular level and whether they protect coronary microvessels. This study used intravital microscopy to image the anaesthetized mouse beating heart microcirculation following stabilization.

Methods and results

A 3D-printed stabilizer was attached to the ischaemia–reperfusion injured (IRI) beating heart. The kinetics of neutrophil, platelet and HSPC recruitment, as well as functional capillary density (FCD), was imaged post-reperfusion. Laser speckle contrast imaging (LSCI) was used for the first time to monitor ventricular blood flow in beating hearts. Sustained hyperaemic responses were measured throughout reperfusion, initially indicating adequate flow resumption. Intravital microscopy confirmed large vessel perfusion but demonstrated poor transmission of flow to downstream coronary microvessels. Significant neutrophil adhesion and microthrombus formation occurred within capillaries with the latter occluding them, resulting in patchy perfusion and reduced FCD. Interestingly, ‘patrolling’ neutrophils were also observed in capillaries. Haematopoietic stem/progenitor cells readily trafficked through the heart but local retention was poor. Despite this, remarkable anti-thromboinflammatory effects were observed, consequently improving microvascular perfusion.

Conclusion

We present a novel approach for imaging multiple microcirculatory perturbations in the beating heart with LSCI assessment of blood flow. Despite deceptive hyperaemic responses, increased microcirculatory flow heterogeneity was seen, with non-perfused areas interspersed with perfused areas. Microthrombi, rather than neutrophils, appeared to be the major causative factor. We further applied this technique to demonstrate local stem cell presence is not a pre-requisite to confer vasculoprotection. This is the first detailed in vivo characterization of coronary microcirculatory responses post-reperfusion injury.

Myocardial Infarction With Nonobstructive Coronary Arteries (MINOCA): Potential Etiologies, Mimics and Imaging Findings

Myocardial infarction with nonobstructive coronary arteries (MINOCA) occurs when a patient presents with positive cardiac enzymes in the absence of obstructive atherosclerosis on coronary angiography. Several hypotheses for the pathogenesis of MINOCA have been suggested and multiple potential underlying etiologies have been reported. This review will outline the reported causes of MINOCA and associated major imaging features. In doing so, it will increase awareness of this entity and equip cardiac imagers with the knowledge to appropriately tailor imaging to make a prompt and accurate diagnosis.

Saddle coronary embolism precipitates flash pulmonary edema

Coronary artery embolism is as an infrequent but important cause of acute myocardial infarction. We present a rare case of a large saddle embolism in the coronary vasculature which led to an acute myocardial infarction and consequently flash pulmonary edema. Despite intensive medical management, our patient did not survive.

Peripartum myocardial infarction associated with coronary spasm and acquired protein S deficiency: A case report

RATIONALE

Coronary angiography (CAG) findings of acute myocardial infarction (AMI) in pregnant women are characterized by a high incidence of normal coronary arteries. This is the first report of AMI with normal coronary arteries during pregnancy, showing coronary spasm and pregnancy-related acquired protein S (PS) deficiency.

PATIENT CONCERNS

A 30-year-old Japanese woman was admitted to an emergency department. One hour before admission, she developed sudden onset of precordial discomfort, back pain, and dyspnea. She was a primigravida at 39 weeks' gestation and had no abnormality in the pregnancy thus far. She had no history of heart disease, diabetes, hypertension, dyslipidemia, deep vein thrombosis (DVT), smoking, or oral contraceptive use and no family history of ischemic heart disease, hemostasis disorder, or DVT. She did not take any medication.

DIAGNOSIS

Electrocardiography showed ST-segment elevations in leads II, III, aVF, and V2-V6. Heart-type fatty acid-binding protein was positive. Echocardiography showed hypokinesis of the anterior interventricular septum and inferior wall. Continuous intravenous infusion of isosorbide dinitrate was initiated. Coronary computed tomography angiography revealed diffuse narrowing of the apical segment of the left anterior descending coronary artery. Three hours after admission, troponin T became positive, and the following enzymes reached their peak levels: creatine kinase (CK), 1,886 U/L; CK-muscle/brain, 130 U/L. She was diagnosed with transmural AMI due to severe coronary spasm and administered benidipine hydrochloride. Five hours after admission, premature membrane rupture occurred.

INTERVENTIONS

Emergency cesarean section was performed. There were no anesthetic or obstetrical complications during the operation. On postpartum day 1, the free PS antigen level was low (29%). On postpartum day 18, she was discharged with no reduction in physical performance.

OUTCOMES

Four months after the infarction, CAG showed normal coronary arteries. Acetylcholine provocation test showed diffuse vasospasm in the coronary artery. She was advised that her next pregnancy should be carefully planned. Two years after delivery, free PS antigen level was within normal range, at 86%. She had not experienced recurrence of angina during the 2-year period. Her child was also developing normally.

LESSONS

In addition to coronary spasm, pregnancy-related acquired PS deficiency may be involved in AMI etiology.

Posterobasal left ventricular aneurysm after myocardial infarction with normal coronary arteries: Case-report

We present a case of a 64-year-old woman with signs of debilitating condition including anginal chest pain, exertional dyspnea, and depression. The patient had previously suffered from a myocardial infarction after a loss of a close family member. Workup showed a posterobasal left ventricular aneurysm and moderate to severe mitral regurgitation in the absence of coronary atherosclerosis. Routine ultrasonography revealed abdominal aortic aneurysm and intraabdominal aortic deviation. The patient was immediately started on optimal medical treatment. On repeat assessment general condition was satisfactory, vital signs were normal, and investigations showed no signs of progressive heart failure or other significant clinical changes. Although prognosis in patients with myocardial infarction with normal coronary arteries is generally considered favorable, mechanical complications such as posterobasal left ventricular aneurysm with moderate to severe mitral regurgitation are possible.

The Role of Coronary Computed Tomography Angiography and Cardiac Magnetic Resonance in STEMI Patients with Normal Coronary Angiography

Usually, the diagnosis of myocardial infarction based on patient symptoms, electrocardiogram (ECG) changes, and cardiac enzymes, is not a challenge for cardiologists. The correlation between coronary anatomy and the ECG territories that present ischemic changes can help the clinician to estimate which coronary artery presents lesions upon performing a coronary angiogram. In certain situations, the diagnosis of myocardial infarction can be difficult due to the lack of correlations between the clinical and paraclinical examinations and the coronary angiogram. In some cases, patients with chest pain and ST-segment elevation on the ECG tracing present with a normal coronary angiography. In other cases, patients without important changes on the ECG can present critical lesions or even occlusions upon angiographic examination. The aim of this article is to highlight the role of noninvasive coronary magnetic resonance and multi-slice computed tomography in patients with ST-segment elevation myocardial infarction and normal coronary angiography.

[41-year-old female patient with ST-elevation myocardial infarction and multiple arterial emboli]

A 41-year-old woman presented with acute angina in the emergency unit. Additionally, she reported pain in both legs and a weight loss of 5 kilograms within the last 10 days. ECG revealed an acute anterior myocardial infarction. However, immediate coronary angiography showed open arteries with minimal arteriosclerosis. A characteristic rise of cardiac enzymes together with an akinesis of the anterior wall and an adjacent mural thrombus was highly suggestive of a transient coronary thrombosis. Further investigations showed occlusion of multiple arteries in both legs and a splenic infarct. Although there was a typical risk profile including smoking, hyperlipidemia and regular estrogen medication, a further work-up was started. Urin analysis was decisive for the presence of proteinuria and a severe nephrotic syndrome. The definite diagnosis was made by direct biopsy of the kidney that revealed the characteristic findings of a minimal change glomerulopathy. Rapid remission could be induced by high-dose oral steroids. During routine work-up of coronary syndromes, especially in those with normal coronaries, rare but treatable causes of myocardial infarction and coagulopathy have to be thought of and should carefully be excluded.

Keep off the grass: marijuana use and acute cardiovascular events

Marijuana is one of the most widely used recreational substances in the world, considered by many consumers as a relatively safe drug with few significant side-effects. We report the case of a 21-year-old man who suffered an acute myocardial infarction following the use of marijuana, despite having no other identifiable risk factors for an acute cardiovascular event. We review the published medical literature regarding acute cardiovascular events following marijuana use and postulate a possible mechanism for this unusual pathological consequence of marijuana use.