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Structure and Function of the Heart

As a central part of the circulatory system, the heart is primarily responsible for pumping blood and distributing oxygen and nutrients throughout the body. Because of this task, the heart may be considered one of the most important organs of the body, such that even small dysfunctions or abnormalities may cause drastic changes or effects in the human organism.

The heart is a muscle whose working mechanism is made possible by the many parts that operate together. The organ is divided into several chambers that take in and distribute oxygen-poor or oxygen-rich blood. These chambers are accompanied by veins and arteries that facilitate the same function. With all of its parts working together towards the same goal, the heart successfully pumps blood with ease.

Normally, a good-functioning adult heart could go on three cardiac cycles or 72 beats per minute—this rate changes for children whose heart rates are normally and relatively faster.

Structure of the heart

The heart can be found at the chest’s center, underneath the sternum in a thoracic compartment. It comprises four chambers and several valves that regulate the normal flow of blood within the body.

Two chambers called atria are located in the upper portion of the heart with the left atrium receiving oxygen-rich blood and the right receiving oxygen-free blood. The valves that separate these chambers are called atrioventricular valves, composed of the tricuspid valve on the left and the mitral valve on the right.

On the other hand, ventricles are chambers found on the lower portion of the heart; they pump oxygen-enriched blood into the body’s organs, reaching even the smallest cells. Similar to the atria, valves also separate the ventricular chambers. Collectively-termed as semilunar valves, these are comprised of the pulmonary and aortic valves.

The heart also has a wall that is composed of three layers: the outer layer epicardium (thin layer), the middle layer myocardium (thick layer), and the innermost layer endocardium (thin layer). The myocardium is thick because it is made up of cardiac muscle fibers.

The heart structure is made more complex because of the mechanisms that allow blood to be distributed throughout the body and return to the heart. Facilitating this continuous process are two types of blood vessels: veins and arteries. The vessels that bring oxygen-free blood back into the heart are called veins; those that bring oxygen-rich blood away from the heart and to other body parts are called arteries.

Functioning in the left ventricle, the largest artery is called the aorta. The aorta is considered a main artery in the body. It further splits into two smaller arteries called common iliac arteries.

With regular functioning, the heart can continuously supply a sufficient amount of oxygen to all parts of the body.

Function of the heart

The heart is the main organ in the circulatory system, the structure is primarily responsible for delivering blood circulation and transportation of nutrients in all parts of the body. This continuous task uplifts the heart’s role as a vital organ whose normal operation is constantly required.

The heart’s blood-pumping cycle, called the cardiac cycle, ensures that blood is distributed throughout the body. The oxygen distribution process begins when oxygen-free blood enters into the heart through the right atrium, goes into the right ventricle, enters the lungs for oxygen refill and release of carbon dioxide, and transfers into the left chambers, ready for redistribution. About 5.6 liters of blood circulate the body, and three cardiac cycles are completed per minute.

The performance of the heart could now be easily monitored when any cardiovascular problem or disorder is suspected. For instance, a regularly abnormal heartbeat or beats per minute are characteristic of a heart-related illness. This is because a heartbeat is a manifestation of the heart’s oxygen-reloading process that is made up of two phases.

The systole is a short period that occurs when the tricuspid and mitral valves close; the diastole is a relatively long period when the aortic and pulmonary valves close. The systole-diastole relationship is the reference in measuring blood pressure. Other ways of physically determining the heart’s regular functioning are examining the pulse rate (beats per minute). An adult’s normal heart rate is at 72 beats per minute, while children normally yield higher heart rates.

Percutaneous Closure

Cardiology is the branch of internal medicine dealing with disorders of the heart and blood vessels. The field is commonly divided in the branches of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology.

Percutaneous closure can be described as a less-invasive surgical procedure used to treat patients with atrial septal defect (ASD) or patent foramen ovale (PFO). Since the utilization of percutaneous closure has evolved over the years, clinicians have already discovered multiple and less invasive methods in treatment, such as catheterization.

Contemporary research proposes the use of this procedure as an alternative to other common and more invasive methods. While percutaneous closure is also a surgical process, its success rate and ease-of-use over alternatives have made it a primary choice in treating ASD and PFO.

Because patients with AS and PFO were empirically found to have higher survival rates when treated using surgical procedures, many interventional studies on the topic have been published. For instance, there is evidence of catheterization and percutaneous occlusion devices as effective treatment modalities for the condition. While percutaneous closure is limited only to small diameters, current research projects are trying to expand the treatment scope of the procedure.

Preparing for Percutaneous Closure

Patients expecting to undergo percutaneous closure should be well-prepared and well-informed of the procedure. Therefore, both young and adult patients should be kept in check regarding the following preparations before treatment.

Testing for cardiac functions – Patients acquiring percutaneous closure either for ASD or PFO should have been screened using cardiac MRI or echocardiogram. This allows doctors to visualize the problem and to factor in other cardiac structures before treatment. Usually, post-procedure MRI or echocardiograms will also be requested by the doctor to monitor treatment success.

Take necessary medications on time – In some cases, physicians would prescribe medications before the procedure. Therefore, patients should ensure that these medications are taken regularly unless otherwise specified by the physician.

Limiting the procedure – Patients who experienced a recent bacterial or fungal infection are usually not allowed to undergo percutaneous closure. This is to limit the spread of microorganisms in surgical tools. 

Allot time for recuperation – While percutaneous closure is minimally invasive, patients would still be required to recuperate for at least 24 hours after the procedure. This will allow for further monitoring and evaluation of cardiac activities post-treatment.

Risk factors – Physicians greatly consider cardiovascular risk factors in intervening using percutaneous closure. In patients with a risk for such diseases, additional screening procedures (such as a coronary angiogram) may be performed prior to treatment.

Procedure for Percutaneous Closure

A percutaneous closure is done under local anesthesia and usually takes approximately one to two hours to complete. Below is a detailed process of a typical percutaneous closure directed at treating ASD or PFO.

•   After pre-intervention preparations have been completed, a physician would start the treatment by inducing local anesthesia or analgosedation into the patient – particularly in the patient’s femoral vein where catheterization will also take place.

•   The physician would then insert a catheter within the femoral vein. Through echocardiographic and fluoroscopic guidance, the device travels from the femoral area into the heart.

•    Before entering the heart through the left atrium, medication such as intravenous heparine may be injected. After this process, the ASD size shall be determined.

•    The device size is dependent on the diameter size of the ASD; as such, the specific device to be used shall be determined only after the actual ASD has been screened.

•    A sheath will be positioned near the target area (which is usually left atrium near the pulmonary vein). The device will be deployed through this sheath through echocardiographic guidance.

•    After confirming a secure position through a pull-and-push technique, the device will be released from the sheath, and its final position will be monitored and documented through the aforementioned screening instruments.

The simplicity of a percutaneous closure procedure enables physicians to treat both children and adults with ASD or PFO with ease. With high success rates, the procedure is widely-utilized globally in treating such conditions.