Most patients are asymptomatic and here, MVP is usually an incidental finding diagnosed in routine cardiac auscultation.

Some patients present with non-specific symptoms like fatigue, dizziness, chest pain, palpitations and arrhythmias. Dyspnea may be reported and indicates moderate heart insufficiency. Repeated syncopes may result from momentarily diminished cerebral blood flow and should be interpreted similarly. It is not uncommon to hear that psychological stress triggers or aggravates complaints, particularly palpitations and arrhythmias, anxiety and panic attacks.

Because MVP increases the risk for endocarditis, symptoms generally associated with the latter may dominate the clinical presentation. Such patients present with malaise, fever, signs of thromboembolism or ischemic cerebral infarction. Weight loss may be noted after prolonged times of illness.

Auscultation typically reveals a mid-systolic heart murmur, often described as a click. This click corresponds to displacement of one or both mitral cusps into the left atrium and may be followed by a late-systolic murmur that indicates mitral regurgitation [9]. Posture changes may provoke a relative delay of the aforementioned mid-systolic click. Any posture associated with an increased left ventricular volume tenses the tendinous chords and thus aids in delaying or even preventing MVP. In turn, body postures that decrease the volume of the left ventricle have the opposite effect and move the MVP-click closer to the first heart sound. This phenomenon cannot be observed in patients suffering from stenosis of semilunar valves.

Auscultation, echocardiography and possibly electrocardiography are the basis of MVP diagnosis.

Mid-systolic click and late-systolic murmur are characteristic signs and should prompt further cardiological evaluation. Echocardiographic visualization of the mitral valve during heart action allows for precise measurements of displacement into the atrium and thickness. The mitral annular diameter may be another parameter of interest. Such measurements should be realized in images obtained from parasternal long-axis view. That way, MVP may be confirmed and classical cases may be distinguished from non-classical ones [5]. While use of the parasternal long-axis view helps to avoid overestimation of mitral cusp displacement, short axis views may be considered useful in questionable cases [10].

Electrocardiography may be carried out if doubts remain as to the origin and severity of arrhythmias. MVP-associated arrhythmias are benign. Sudden cardiac arrest does rather result from rupture of the tendinous chords and congestive heart failure. This is a very rare occurrence, but it may happen and should be considered when advising about therapeutic options.

Treatment largely depends on the severity of MVP and, if present, the underlying disease.

Most patients are asymptomatic and will remain asymptomatic. They should be reassured that MVP is a benign condition with a low rate of complications. Disease progress should be monitored in regular intervals and thus, patients should undergo echocardiographic examination every five years if comorbidities don't indicate shorter periods of re-evaluation. Asymptomatic patients need not adjust their life style, i.e., they may continue to do sports, even practice intensive training. Similar to any other person, their cardiovascular health may benefit from non-smoking.

Patients diagnosed with moderate MVP may receive symptomatic treatment. Beta-sympatholytics are most frequently administered to relieve autonomic complaints [11]. These patients should be strongly advised to stop smoking and to reduce consumption of coffee, energy drinks and similar stimulants. Because moderate MVP is associated with an increased risk of cardiac arrhythmias, 24-hour ambulatory electrocardiographic monitoring should be realized to detect such irregularities.

Severe MVP may require surgical intervention. If surgery is delayed, left ventricular function will worsen and patients are kept at risk of chordae tendineae rupture and congestive heart failure. This also applies to asymptomatic patients with left ventricular dilation, pulmonary hypertension and/or considerable arrhythmias.

In general, prophylaxis of thromboembolism and stroke may be achieved by administration of anti-coagulants like acetylsalicylic acid. Possible side effects should be considered before choosing this treatment [12].

In patients presenting with signs of endocarditis, antibiotic treatment should be provided accordingly. If an individual is considered to be at high risk of endocarditis due to mitral regurgitation, antibiotics may be administered prophylactically.

Although MVP is often referred to as a benign disorder that does not cause any symptoms in the vast majority of patients, if this condition becomes symptomatic severe consequences and even death are possible, yet unlikely outcomes:

• While mitral regurgitation may not be noted upon diagnosis, MVP may exacerbate and mitral regurgitation may develop. Rupture of tendinous chords provokes a sudden, significant worsening of the patient's condition. Dilation of the left ventricle and reduction of myocardial contractility may ultimately lead to congestive heart failure.
• Insufficiency of the mitral valve does not only affect the left heart but also compromises pulmonary circulation and right heart. In severe cases, global heart insufficiency may result from this condition.
• Additionally, MVP patients are at higher risks of cardiac arrhythmias and sudden cardiac arrest as well as endocarditis. The latter, in turn, augments the likelihood of suffering thromboembolism and stroke.

The etiology of MVP is largely unknown. However, familial accumulation has been observed and genetic screens allowed for the identification of several marker sequences associated with an increased risk of MVP. According to the order of description, they have been designated MMVP1, MMVP2 and MMVP3, respectively. They are located at positions 16p11.2-p12.1, 11p15.4 and 13q31.3-q32.1 [2] [3] [4].

Connective tissue disorders like Marfan's syndrome and Ehlers Danlos syndrome may be associated with MVP, but other symptoms usually dominate the clinical picture.

Most MVP patients neither present a marker sequence nor do they suffer from connective tissue disorders. Thus, the majority of MVP cases is deemed idiopathic.

Due to the lack of a uniformly accepted definition, epidemiological data regarding MVP vary largely. There is consensus about MVP being a very common condition, though. It has been estimated that 2.4% of the overall population of the United States is affected by this condition [3]. Elsewhere, prevalence rates of less than 0.5% have been reported, but such results have subsequently been questioned. On the other hand, very high estimates of MVP prevalence - more than 10% have been suggested - seem to originate from a loose definition and overdiagnosis.

Neither racial nor gender predilections are known.

Classic MVP has to be distinguished from non-classic MVP. Both conditions differ in pathophysiology and prognosis, although they share a displacement of mitral cusps into the left atrium of more than 2 mm. Additionally, classic MVP requires a diastolic thickness of those cusps that exceeds 5 mm [5]. In contrast, mitral cusps are less than 5 mm thick in cases of non-classic MVP. Both classic and non-classic MVP seem to account for approximately equal amounts of cases.

With regards to classic MVP, histopathological analyses of mitral cusps reveal myomatous degeneration. Of note, the first "M" in MMVP, as mentioned above, stands for myomatous. Collagen and elastin fiber structures as well as glycosaminoglycan production are altered, which renders mitral cusps less resilient [6]. Similar anomalies can be observed in tendinous chords and very distensible chords are unable to prevent displacement of mitral cusps into the left atrium. These conditions tend to worsen over time and may result in mitral regurgitation. Chordae tendineae may even rupture and in these cases, exacerbation of MVP symptoms is usually very sudden. With mitral regurgitation, both left atrium and left ventricle suffer from volume overload and in the long term, the left ventricle dilates and myocardial contractility diminishes [7]. Pressure loads also affect pulmonary veins and may subsequently compromise pulmonary circulation in general as well as right atrium and ventricle.

Non-classic MVP is not associated with mitral valve degeneration. Histopathological analysis of these tissues don't reveal any anomalies in such patients. MVP rather occurs secondary to any other disorder, e.g., volume depletion [8], left ventricular dilation that does not result from classic MVP, relatively small mitral cusps, etc. Progression largely depends on the underlying disease and is not to be expected in cases of momentary hypovolemia, but is likely if the primary disease aggravates.

Because genetic factors seem to play a role in MVP, routine echocardiographic exams may be of use to detect anomalies in first-degree relatives of those patients diagnosed with this disease. However, since most cases are deemed idiopathic, only few patients will truly benefit from this measure. Otherwise, no preventive actions can be recommended.

The mitral valve is located between left atrium and left ventricle. Both atrioventricular valves, i.e., the mitral valve and the tricuspid valve, are open during diastole and thus allow filling of the left and right ventricle, respectively. The abrupt increase in ventricular pressure that occurs at the beginning of systole evokes passive closure of the atrioventricular valves. All cusps - the mitral valve has two, the tricuspid valve three - close flush and form a tight seal that impedes blood to flow back into the respective atrium. Under physiological conditions, the tendinous chords that connect valve cusps and intraventricular papillary muscles prevent the former to protrude into the atrium. Without tendinous chords, systolic intraventricular pressure would suffice to turn atrioventricular valve cusps into the respective atrium.

With regards to the left heart, protrusion of one or both cusps into the atrium is referred to as mitral valve prolapse (MVP). It may be associated with mitral insufficiency and, if blood leaks into the left atrium during systole, mitral regurgitation. The entirety of symptoms related to these conditions is designated mitral valve prolapse syndrome and typically comprises fatigue, dizziness, arrhythmias and chest pain. Mild cases are generally asymptomatic, but an exacerbation is possible [1]. It's etiology is largely unknown and many cases are deemed idiopathic. A genetic component has been suggested and pedigree analyses seem to imply a genetic disorder inherited with an autosomal dominant trait. MVP may also be diagnosed in patients suffering from complex cardiac malformations and connective tissue disorders.

In general, auscultation prompts a strong suspicion for MVP. This diagnosis is subsequently confirmed by means of echocardiography.

There are four chambers in the heart, two atria and two ventricles. Cardiac valves are located between atrium and ventricle on the left and right side of the heart and impair backflow of blood during heart action. In order to do so, these valves open when the ventricle is filling and close upon intraventricular pressure increase, which is necessary to pump the blood through the body. Furthermore, tendinous chords attach atrioventricular valve cusps to intraventricular muscles to avoid protrusion into the atrium. If valvular tissue structure is altered or if those suspending chords rupture, intraventricular pressure will push valvular cusps into the atrium.

The mitral valve is ubicated between left atrium and left ventricle and a mitral valve prolapse (MVP) occurs when one or both of its cusps bulge into the left atrium. The entirety of symptoms that may be associated with this condition is referred to as mitral valve prolapse syndrome.

Causes

In most cases, no precise cause can be determined and MVP is deemed idiopathic.

In some families, MVP may be detected unusually often and this observation implies a genetic component in MVP etiology. Indeed, several marker sequences have been identified that are related to this condition.

MVP may also occur in patients suffering from connective tissue disorders like Marfan's syndrome and Ehlers Danlos syndrome.

Symptoms

Most patients are asymptomatic and will remain asymptomatic. In some cases, patients claim fatigue, dizziness, chest pain, palpitations or breathing difficulties. Symptoms may exacerbate in situations of psychological stress and patients may experience anxiety or panic attacks.

Diagnosis

Auscultation generally prompts a strong suspicion for MVP. Indeed, routine examination often leads to incidental diagnosis of MVP since most patients don't present any symptoms and never consult their physicians due to possible cardiac problems.

Confirmation and evaluation of MVP severity require echocardiography, i.e., an ultrasound examination of the heart.

Treatment

Asymptomatic patients may merely undergo echocardiographic follow-ups in five-year intervals to monitor possible disease progress. Those individuals experiencing any of the above mentioned symptoms may benefit from beta-blockers.

In severe cases, surgical intervention is necessary to avoid global cardiac insufficiency and heart failure although these are very rare complications of MVP.

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