# # The Heart

The heart is a muscular structure with four chambers including two atria, which are the filling chambers and two ventricles, which are the pumping chambers.

The venous blood is drained from the body to the right chambers of the heart, then oxygenated in the lungs and ejected to the entire body by the left chambers of the heart.

The human heart has four valves (flaps made of tissue) that control the direction of blood flow in the circulation. 人类心脏有四个瓣膜 (由组织构成的皮瓣)，控制血液在循环中的流动方向。
Normal valves act like a system of one-way doors, which assures unidirectional blood flow through the various chambers of the heart.

The aortic and mitral valves are part of the "left" heart and control the flow of oxygen-rich blood from the lungs to the body, while the pulmonic and tricuspid valves are part of the "right" heart and control the flow of oxygen-depleted blood from the body to the lungs.

The aortic valve lies between the left ventricular chamber and aorta, preventing blood from leaking back into the left ventricle after it has been ejected into the circulation.

The mitral valve lies between the left atrium and left ventricle preventing blood from leaking back into the left atrium during ejection (systole).

Similarly on the right side, the pulmonic valve separates the right ventricle from the pulmonary artery, whereas the tricuspid valve separates the right ventricle from the right atrium.

The normal mitral valve opens when the left ventricle relaxes (diastole) allowing blood from the left atrium to fill the decompressed left ventricle.

When the left ventricle contracts (systole), the increase in pressure within the ventricle causes the valve to close, preventing blood from leaking into the left atrium and assuring that all of the blood leaving the left ventricle (the stroke volume) is ejected through the aortic valve into the aorta and to the body.

Proper function of the valve is dependent on a complex interplay between the annulus, leaflets and subvalvular apparatus.

Long-standing mitral regurgitation due to mitral valve prolapse is well established as a significant cause of cardiovascular morbidity and mortality [2] [3], with surgical intervention often required in patients with severe regurgitation to preserve life expectancy in affected patients.

Mitral valve repair is now well established and is applicable in practically all patients with clinically significant mitral valve prolapse due to degenerative mitral-valve disease [4] [5].

Valve repair offers a distinct event-free survival advantage compared with replacement with a bioprosthetic or mechanical valve [6] [7] [8].

# # Leaflets 瓣叶

The mitral valve has two leaflets.

The anterior leaflet has a semi-circular shape and attaches to two fifths of the annular circumference.

There is continuity between the anterior leaflet of the mitral valve and the left and non-coronary cusp of the neighboring aortic valve, referred to as the aortic-mitral curtain.

These two components of the aorto-mitral curtain are on two separate anatomical planes, situated at an angle of $120 ^{\circ}$ which corresponds to the planes of the aortic and mitral annulus respectively.

The free edge of the anterior leaflet is usually continuous, without indentations.

The lack of redundancy of this leaflet along its margin must be taken into consideration in the setting of anterior leaflet prolapse as only small areas of leaflet can be safely resected.

The motion of the anterior leaflet also defines an important boundary between the inflow (during diastole) and outflow (during systole) tracts of the left ventricle.

 Aortic valve 主动脉瓣 AV Left coronary sinus 左冠窦 Non-coronary sinus 无冠窦 Aortic mitral curtain 主动脉瓣二尖瓣幕帘 Anterior commissure 前交界 AC Posterior commissure 后交界 PC Anterior leaflet 前瓣 Posterior leaflet 后瓣

The posterior leaflet of the mitral valve has a quadrangular shape and is attached to approximately three fifths of the annular circumference.

The posterior leaflet typically has two well defined indentations which divides the leaflet into three individual scallops identified as P1 (anterior or medial scallop), P2 (middle scallop), and P3 (posterior or lateral scallop).

The three corresponding segments of the anterior leaflet are A1 (anterior segment), A2 (middle segment), and A3 (posterior segment)[9].

This nomenclature is an important tool to describe specific anatomic segmental anatomy between echocardiographer and surgeon.

They also imply redundancy to the margin of the posterior leaflet, particularly in the setting of prolapse which triggers a process leading to excess tissue in the prolapsing segment, which therefore allows more aggressive resection compared to the anterior leaflet.

The height of the posterior leaflet is less than the anterior leaflet, however, both leaflets have similar surface areas.

# # Commissures

The commissures define a distinct area where the anterior and posterior leaflets come together at their insertion into the annulus. Sometimes the commissures exist as well defined leaflet segments, but more often this area is a subtle structure, and can be identified using two anatomic landmarks: the axis of corresponding papillary muscles and the commissural chordae, which have a specific fan-like configuration. Several millimeters of valvular tissue separates the free edge of the commissures from the annulus. This area must be respected when dealing with prolapse of a commissure and the corresponding anterior and posterior leaflet segment (P3 and A3) by resection, for example, or a residual regurgitation will occur from this region.

1. Interactive 3D heart tour ↩︎

2. Naji P, Asfahan F, Barr T et al. Impact of duration of mitral regurgitation on outcomes in asymptomatic patients with myxomatous mitral valve undergoing exercise stress echocardiography. J Am Heart Assoc. 2015 Feb 11;4 (2). pii: e001348. 二尖瓣反流持续时间对运动负荷后无症状二尖瓣粘液瘤患者预后的影响。 ↩︎

3. Topilsky Y1, Michelena H, Bichara V, et al. Mitral valve prolapse with mid-late systolic mitral regurgitation: pitfalls of evaluation and clinical outcome compared with holosystolic regurgitation. Circulation. 2012 Apr 3;125 (13):1643-51. 二尖瓣脱垂合并二尖瓣收缩中晚期反流：与全收缩反流比较评估和临床结果的陷阱。 ↩︎

4. Adams DH, Anyanwu AC, Rahmanian PB, Filsoufi F. Current concepts in mitral valve repair for degenerative disease. Heart Fail Rev 2006; 11:241-257. 退行性疾病二尖瓣修复术的最新概念。 ↩︎

5. Nishimura RA et al. 2014 AHA/ACC Guideline for the Management of Patients With Valvular Heart Disease A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. 2014;129:e521-e643. 2014 年 AHA/ACC 心脏瓣膜病患者管理指南美国心脏病学会 / 美国心脏协会特别工作组实践指南的报告。 ↩︎

6. Castillo JG, Anyanwu AC, Fuster V, Adams DH, A Near 100% Repair Rate for Mitral Valve Prolapse is Achievable in a Reference Center: Implications for Future Guidelines. J Thorac Cardiovasc Surg. 2012; 144 (2): 308-12. 二尖瓣脱垂的 100% 修复率是可以在参考中心实现的：对未来指南的影响。 ↩︎

7. David TE. Outcomes of mitral valve repair for mitral regurgitation due to degenerative disease. Semin Thorac Cardiovasc Surg 2007; 19:116-120. 二尖瓣成形术治疗退行性疾病二尖瓣关闭不全的疗效观察 ↩︎

8. Portions excerpted, with permission, Adams DH, Anyanwu AC. The cardiologist's role in increasing the rate of mitral valve repair in degenerative disease. Current Opinion in Cardiology 2008, 23:105-110. 心脏病专家在提高退行性疾病二尖瓣修复率中的作用。 ↩︎

9. Carpentier A. Cardiac valve surgery--the "French correction". J Thorac Cardiovasc Surg 1983 September;86(3):323-37. ↩︎