lNTRODUCTlON

Coronary arteries are usually distributed on the surface of the epicardium, and occasionally segmental blood vessels run through the myocardium[1]. When this blood vessel is compressed by 70% in systole and 35% in late diastole, it is called a myocardial bridge[2]. Referring to relevant studies, Myocardial bridge (MB) can cause ischaemia in some patients, and the degree of systolic compression is inversely proportional to coronary flow reserve[3]. It has been proposed that drugs are the first choice for the treatment of MB. For isolated MB with severe stenosis, it is necessary to evaluate the state of coronary blood flow. The main evaluation methods are fractional flow reserve (FFR) and instantaneous wave-free ratio (IFR). FFR is defined as the ratio of distal coronary artery pressure to aortic pressure under the condition of maximal dilatation of small vessels and microvessels in the coronary artery supply area and no significant increase in central venous pressure under the action of adenosine[4]. IFR refers to the ratio of distal mean pressure to mean arterial pressure in diastolic nonwaveform interphase stenosis. This principle uses the blood pressure with the lowest diastolic coronary artery resistance to approximately replace coronary artery blood pressure under the action of adenosine[5,6]. In this case, we describe a case of coronary angiography

the distal radial artery pathway. The results showed that the anterior descending branch MB was associated with 100% systolic compression (Figure 1). After intraoperative drug control of the ventricular rate, the improvement of the coronary ischaemic state was confirmed by changes in the evaluation index of coronary artery function.

CASE PRESENTATlON

Chief complaints

A 37-year-old Chinese male was admitted to the hospital with repeated chest tightness for two years.

At the end of the operation, the puncture site was pressed with an elastic bandage to stop bleeding.Three hours later, there were no complications, such as blood oozing and haematoma. The patient was discharged 3 h after operation. After discharge, the patient was treated with metoprolol 47.5 mg qd for one month, and the symptoms of chest tightness were significantly relieved after follow-up.

Physical examination revealed an auscultation heart rate of 74 beats/min and no pathological murmur was found in each valve auscultation area. There was no enlargement of the heart boundary of percussion and no tremor in palpation.

History of present illness

打造“葡萄、枸杞、草畜”三大產(chǎn)業(yè)集群，推進(jìn)一二三產(chǎn)業(yè)深度融合，以產(chǎn)業(yè)發(fā)展為突破口，破解移民戶(hù)增收難題。

History of past illness

The results showed that the MB of the middle part of the left anterior descending branch was accompanied by 100% systolic compression, and the rest of the vessels did not have any other significant stenosis (Figure 2).

Personal and family history

No family history of heart disease.

Physical examination

睡眠是個(gè)體必需的生理過(guò)程，睡眠不足嚴(yán)重危害人體的心理生理健康，對(duì)于冠心病患者來(lái)說(shuō)尤為重要，但冠心病患者往往普遍存在睡眠質(zhì)量差的問(wèn)題，導(dǎo)致患者出現(xiàn)焦慮，乃至抑郁的狀態(tài)[12]。本研究顯示，觀察組實(shí)施認(rèn)知行為護(hù)理模式，遵醫(yī)行為良好率明顯優(yōu)于對(duì)照組，且觀察組睡眠質(zhì)量（PSQI評(píng)分）亦優(yōu)于對(duì)照組。

Laboratory examinations

No obvious abnormality in laboratory examination.

In this paper,we consider two typical distributions ofThey are uniform shape

至于植物萃取護(hù)膚品，我的建議還是別用了。因?yàn)橹参镙腿⊥ǔＲ馕吨峒儾?，雜質(zhì)多，容易造成過(guò)敏，有潛在的威脅。

Imaging examinations

Twenty-four hours before the operation, the electrocardiogram was normal, and echocardiography showed that the left ventricular systolic function was normal.

在初中數(shù)學(xué)的一題多解的教學(xué)中，互動(dòng)合作交流是實(shí)現(xiàn)學(xué)生思維交流互動(dòng)、促進(jìn)學(xué)生多方面探究問(wèn)題答案的有效形式。例如，在“相似三角形”方面的教學(xué)中，相似三角形的判定及其性質(zhì)是教學(xué)難點(diǎn)，它們經(jīng)常要用于多解題和生活問(wèn)題的論證和反論證應(yīng)用方面，考驗(yàn)學(xué)生的探究能力。比如，相似三角形有關(guān)的題目多為多解題，一個(gè)學(xué)生一般是思維指向了哪個(gè)定理，就按照這個(gè)定理去解題，沒(méi)有要求的話(huà)一般不會(huì)再去探究新的解題方法。但是不同的學(xué)生的解題思維是不同的，因此最終會(huì)有許多不同的探究思維。在這種情況下，教師組織起合作學(xué)習(xí)小組來(lái)，目的就是要促進(jìn)不同解題思維的碰撞和共享，促進(jìn)學(xué)生之間的取長(zhǎng)補(bǔ)短，實(shí)現(xiàn)每一位學(xué)生數(shù)學(xué)探究能力的拓展和發(fā)散。

FlNAL DlAGNOSlS

The patient had a history of previous hypertension for 4 years, was not taking medications, denied a history of diabetes and other chronic illnesses, had no history of long-term smoking or hyperlipidaemia,and had no family history of heart disease or other related risk factors for coronary heart disease.

TREATMENT

Considering that the symptoms of chest tightness and discomfort may be related to severe stenotic myocardial bridges, intracoronary function evaluation was performed. The pressure was adjusted to 1 when the pressure guide wire entered the root of the aorta. The pressure was measured after the guide wire passed through the diseased segment, and an IFR of 0.72 was measured. Using an adenosine intravenous pump, an FFR of 0.66 was measured after the patient's blood pressure dropped by 10% .The critical values of FFR and IFR were 0.80 and 0.89, respectively. A value less than the critical value indicates that a myocardial bridge caused significant haemodynamic changes. After myocardial bridge surgery, β-blockers were routinely used to reduce the heart rate of the patient. During the operation, we waited for the completion of the basic metabolism of adenosine and injected esmolol 0.02 μg/kg/min intravenously. After the heart rate dropped to 60 beats/min (basal heart rate 75 beats/min), changes in coronary blood flow could be observed. The results of the retest were FFR = 0.65 and IFR = 0.83(Figure 3).

OUTCOME AND FOLLOW-UP

如果發(fā)現(xiàn)飼料中存在的蛋白質(zhì)不充足，要為其提供一些動(dòng)物性蛋白，如魚(yú)粉；植物性蛋白，如玉米蛋白粉等；如果氨基酸不充足，可以為其提供充足的氨基酸；如果發(fā)現(xiàn)維生素不充足，可以在飼料中增加維生素的含量，如鋅、鐵、銅等。將這些微量元素作為要點(diǎn)，還要引進(jìn)適量硫酸鋅、硫酸亞鐵等。當(dāng)發(fā)現(xiàn)其中存有的硫含量不足時(shí)，可以適當(dāng)增加硫酸鈉，其含量為1%。經(jīng)過(guò)3 d后，可以將硫酸鈉的含量改為0.1%，同時(shí)也需要增加生石膏粉，其含量為1%～2%。如果增加羽毛粉，其含量為5%；如果鹽分不充足，可以將食鹽的含量保持在0.5%～1%；如果發(fā)現(xiàn)飼料中的粗纖維含量不足，可以增加5%的統(tǒng)糠粉[2]。

DlSCUSSlON

多國(guó)國(guó)防部長(zhǎng)贊揚(yáng)中國(guó)提出的“一帶一路”倡議。越南國(guó)防部長(zhǎng)吳春歷大將指出，目前中國(guó)已經(jīng)成為地區(qū)和世界大國(guó)，中國(guó)的“一帶一路”倡議證明中國(guó)在地區(qū)和國(guó)際事務(wù)中正在發(fā)揮更大的作用，世界也期待中國(guó)成為領(lǐng)導(dǎo)者。塞爾維亞國(guó)防部長(zhǎng)亞歷山大·武林指出，中國(guó)提出的“一帶一路”倡議對(duì)塞爾維亞非常重要。希望中國(guó)繼續(xù)推動(dòng)這一倡議，給各方帶來(lái)實(shí)實(shí)在在的好處，也希望看到更多的中國(guó)人到塞爾維亞來(lái)尋求投資機(jī)會(huì)，促進(jìn)塞國(guó)經(jīng)濟(jì)發(fā)展。新加坡國(guó)防部長(zhǎng)黃永宏指出，中國(guó)長(zhǎng)期堅(jiān)持國(guó)家不分大小一律平等，相互尊重、合作共贏，這是我們大家共同的奮斗目標(biāo)。

After taking aspirin, tigrenol and atorvastatin calcium before the operation, the patient still showed chest tightness. Since the chest tightness was not alleviated, coronary angiography was performed.

CONCLUSlON

For isolated MB with severe stenosis, it is novel to observe the improvement of coronary blood flow after intraoperative drug therapy is added to reduce ventricular rate. At present, the main treatment is still drugs. However, the applicable types of evaluation methods and the effectiveness of long-term treatment need to be further evaluated by large-scale studies.

FOOTNOTES

Sun JL conceived and wrote this report; Sun JL and Huang SW operated on the patients; Sun JL, Yan GD organized the data; and Huang SW revised the paper; all authors have read and approved the final manuscript.

All study participants, or their legal guardian, provided informed written consent prior to study enrollment.

The myocardial bridge is a segment of the coronary artery in the myocardium. Long-term studies have suggested that MB only blocks systolic coronary blood flow[7]. However, some studies have reported that MB is associated with stable angina pectoris, acute coronary syndrome and malignant arrhythmias that may lead to sudden death[8]. Therefore, a full understanding of the haemodynamic significance of MB during surgery is of great significance to guide treatment. There have been a large number of studies evaluating the intracoronary function of myocardial bridges. First, Teragawa

[8] used FFR and IFR to confirm that myocardial bridges can cause coronary ischaemia and angina pectoris in patients. Second, Ryan and Escaned[9] measured the FFR of patients with myocardial bridges stimulated by baseline and dobutamine. This study ultimately found that the average FFR measurement increased artificially due to excessive systolic blood pressure, and diastolic FFR should be the first choice. Compared with adenosine, dobutamine seems to be more accurate in evaluating myocardial bridge FFR, highlighting the importance of muscle strength in the development of vascular compression. Third, Klues found that a myocardial bridge causes coronary haemodynamic abnormalities by combining intracoronary Doppler blood flow with pressure measurement. This is characterized by a continuous decrease in diastolic diameter, an increase in blood flow velocity and retrograde blood flow, and a decrease in blood flow reserve. However, there are few reports on the evaluation of the intracoronary function of myocardial bridges after intraoperative drug treatment. In this case, the MB was located near the middle part of the anterior descending branch. Here, the muscle bridge is longer, so the degree of systolic compression is more serious. Angiography also indicated that the muscle bridge had a systolic compression of 100%. To understand the blood flow changes of severely stenotic myocardial bridges, intraoperative coronary functional evaluation was used. The decrease in coronary flow reserve has a significant inhibitory effect on diastolic coronary blood flow.There are several possible mechanisms for this effect. One such mechanism is that the blood flow in the proximal end of the myocardial bridge with severe systolic compression can be stopped or even retrograde. This results in a partial decrease in the distal perfusion pressure of the bridging vessel and leads to ischaemia[9]. Vascular contraction and compression of the myocardial bridge segment causes turbulence and high shear stress, which leads to the disturbance of vascular endothelial function, an increase in the expression of vasoactive substances and morphological changes in endothelial cells and smooth muscle cells in this region. This leads to self-repair of the vascular endothelium, thickening of the vessel wall, stenosis of the lumen and a decrease in coronary blood flow reserve. The more serious the systolic vascular compression of the myocardial bridge is, the worse the diastolic diameter recovery,the higher the intracoronary filling pressure, and the lower the blood supply rate., All of these conditions seriously affect the main perfusion period of the coronary artery. Another mechanism by which the coronary flow reserve effects diastolic coronary blood flow occurs when the change in diastolic blood flow is more obvious. An obvious abnormality in flow velocity further leads to a decrease in coronary flow reserve. In this case, the coronary blood flow reserve decreased seriously in the severely narrow myocardial bridge, and the symptoms of myocardial ischaemia, such as chest tightness, became more obvious once the heart rate increased. In the face of isolated MB with such severe stenosis, in addition to percutaneous coronary intervention, coronary artery bypass grafting and surgical unroofing, the main treatment is still drugs. To understand the improvement of coronary artery ischaemia in patients with severe myocardial bridge stenosis, esmolol 0.02 μg/kg/min was injected intravenously during the operation. When the heart rate dropped to 60 beats/min, the FFR and IFR were measured again. FFR was 0.65 and IFR was 0.83. The IFR was significantly higher than it was before treatment, suggesting that the coronary flow reserve was better than before. One possible reason is that esmolol inhibits the automaticity of the sinoatrial node, prolongs atrioventricular conduction and reduces heart rate. Thus the diastolic period is prolonged, the time of myocardial bridge blood supply is prolonged, and the myocardial contractility and myocardial oxygen consumption are reduced. The average peak value, diastolic peak value and maximum instantaneous peak velocity in the myocardial bridge were significantly increased[10]. A second possible reason is that β-blockers can also reduce systemic and intramural pressure to reduce vascular compression in vitro, They can also reduce the indirect effect of sympathetic drive, further improve the state of coronary ischaemia, and relieve ischaemic symptoms, such as chest tightness and chest pain, in patients[11]. Other possible reasons could be a decrease in heart rate, decrease in peak blood flow in early diastole, prolongation of diastolic platform, disappearance of reverse blood flow, recovery of normal diastolic blood flow velocity, and relief of coronary flow reserve.

The authors declare that they have no conflicts of interest.

The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).

This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BYNC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is noncommercial. See: https://creativecommons.org/Licenses/by-nc/4.0/

China

Long-Jun Sun 0000-0003-4274-8829; Ding-Guang Yan 0000-0002-7863-7955; Shu-Wei Huang 0000-0001-7537-219Χ.

Χing YΧ

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Χing YΧ

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