Barlow's syndrome
Barlow's syndrome, also known as mitral valve prolapse (MVP), is a common heart disorder that primarily affects the function of the mitral valve, which regulates blood flow between the heart's upper and lower chambers. In this condition, the valve flaps may bulge into the atrium, potentially causing backward blood flow or leakage. While often benign, certain individuals are at higher risk, including those with a family history of MVP, young adults aged fourteen to thirty, and females, as well as those with conditions like scoliosis or Marfan syndrome.
Genetic factors can play a role, with some cases showing hereditary patterns. There are specific genetic markers associated with the syndrome, though many cases occur sporadically. Symptoms can vary, with some individuals remaining asymptomatic, while others may experience irregular heartbeat, fatigue, and anxiety. Diagnosis is typically made through a stethoscope examination, echocardiograms, or advanced cardiac imaging.
Most patients do not require treatment, but in some cases, medications or surgery may be necessary if symptoms become severe. Lifestyle modifications, such as reducing caffeine intake and regular exercise, can help manage symptoms. Overall, Barlow's syndrome is a manageable condition, with many individuals leading active lives.
Barlow's syndrome
ALSO KNOWN AS: Mitral valve prolapse; floppy valve syndrome; click-murmur syndrome
DEFINITION: Barlow’s syndrome, also known as mitral valve prolapse (MVP), is a common, usually benign, heart disorder. The mitral valve controls blood flow between the upper (atrium) and lower (ventricle) chambers on the left side of the heart. Normally, blood should flow only in one direction, from the upper chamber into the lower chamber. In MVP, the valve flaps do not work properly; part of the valve balloons into the atrium, which may be associated with blood flowing in the wrong direction or leaking back into the atrium.
Risk Factors
Individuals with a family history of MVP, individuals between the ages of fourteen and thirty, and females are at risk for the disorder. Other risk factors include having scoliosis, a thin chest diameter, low body weight, low blood pressure, chest wall deformities, Marfan syndrome, or Graves disease.
Etiology and Genetics
While the majority of cases of Barlow’s syndrome appear sporadically with no demonstrable genetic origin, it has been recognized since the first description of this disorder in the 1960s that in some families there is a distinct hereditary component. With the completion of the Human Genome Project and other molecular genetic studies, at least three autosomal loci and one X-linked gene have been identified in which mutations can lead to development of the disease. The autosomal genes are found on the short arm of chromosome 11 (at position 11p15.4), the long arm of chromosome 13 (at position 13q31-32), and the short arm of chromosome 16 (at position 16p11.2-12.1). Although the genes have been localized to these specific chromosomal regions, little is known about the gene products or their specific association with disease symptoms. In all three cases, inheritance is transmitted as an autosomal dominant, meaning that a single copy of the mutated gene is sufficient to cause full expression of the syndrome. An affected individual has a 50 percent chance of transmitting the mutation to each of his or her children.
The rare X-linked form of Barlow’s syndrome is inherited as a sex-linked recessive trait. Mothers who carry the mutated gene on one of their two X chromosomes face a 50 percent chance of transmitting this disorder to each of their male children. Female children have a 50 percent chance of inheriting the gene and becoming carriers like their mothers. Although females rarely express the syndrome fully, female carriers may occasionally show minor manifestations. Affected males will pass the mutation on to all of their daughters but to none of their sons.
The filamin A gene, located at position Xq28, has been identified as the gene responsible for the X-linked form of Barlow’s syndrome, which is also known as familial cardiac valvular dystrophy. Filamin A is a phosphoprotein that acts in cells to help bind the actin cytoskeleton to the plasma membrane. It is unknown at present how mutations in this gene affect MVP, but research suggests the possibility that filamin A may affect heart valve development by regulating transforming growth factors or affecting some aspect of the signaling pathways for these growth factors.
Symptoms
People with MVP often have no symptoms at all. If symptoms do occur, they may include irregular heartbeat, fatigue, chest pain, panic attacks or anxiety, rapid heartbeat (palpitations), a sensation of missed heartbeats, shortness of breath, dizziness, and intestinal problems (such as irritable bowel syndrome).
Screening and Diagnosis
MVP can be heard through a stethoscope. A small blood leakage will sound like a murmur. When the mitral valve balloons backward, it may produce a clicking sound. Both murmurs and clicks are telltale signs of MVP. An echocardiogram can confirm the diagnosis. A patient may be asked to wear a Holter monitor for a day or two to continuously record the electrical activity of his or her heart (electrocardiograph). These and other types of cardiac imaging, such as cardiac computed tomography (CT), cardiac positron emission tomography (PET), and cardiac MRI, can be particularly helpful in diagnosing MVP in patients with a high risk of sudden cardiac death and complex ventricular arrhythmias.
Treatment and Therapy
In most cases, no treatment is necessary. Patients should ask their doctors whether they should take antibiotics prior to dental work or surgery; antibiotics may help to prevent endocarditis, an infection of the membrane that covers the inside of the heart.
If symptoms include chest pain, anxiety, or panic attacks, a beta-blocker medication can be prescribed. Patients should also ask their doctors if they may continue to participate in their usual athletic activities. In very rare cases, the blood leakage may become severe, requiring surgery to repair and replace the mitral valve.
Prevention and Outcomes
There are no guidelines for preventing MVP of unknown or genetic origin. Patients may be able to prevent symptoms, however, through certain lifestyle changes. They can limit their intake of caffeine; avoid medications, such as decongestants, that speed up their heart rates; and exercise regularly, following their healthcare providers’ recommendations for intensity.
Bibliography
DeSilva, Regis. Heart Disease. Santa Barbara: Greenwood, 2013. Print.
Durante, James F., Cheryl L. Durante, and John G. Furiasse. The Mitral Valve Prolapse Syndrome, Dysautonomia Survival Guide. Oakland: New Harbinger, 2002. Print.
Badash, Michelle. “Mitral Valve Prolapse.” EBSCO Health Library. EBSCO Information Services, 2 May 2014. Web. 22 July 2014.
Frederickson, Lyn. Confronting Mitral Valve Prolaspse Syndrome. New York: Warner Books, 1992. Print.
Hayes, Denise D. “Mitral Valve Prolapse.” Nursing 42.4 (2012): 51. General Science Full Text (H.W. Wilson). Web. 22 July 2014.
Krakor, Ralf. Endoscopic Mitral Valve Surgery: Handbook of Minimal-Invasive Cardiac Surgery. Berlin: Walter de Gruyter, 2012. Print.
Rybczynski, Meike, et al. “Predictors of Outcome of Mitral Valve Prolapse in Patients with the Marfan Syndrome.” American Journal of Cardiology 107.2 (2011): 268–74. Academic Search Alumni Edition. Web. 22 July 2014.
Tayal, Bhupendar, et al. "Cardiac Imaging for Risk Assessment of Malignant Ventricular Arrhythmias in Patients With Mitral Valve Prolapse." Frontiers Cardiovascular Medicine, vol. 8, 17 Mar. 2021, doi.org/10.3389/fcvm.2021.574446. Accessed 10 Sept. 2024.