I always used to wonder what people meant by saying that he or she has got a hole in the heart. It always left me confused as to how that could be until I read about it in Biology. All human beings do have a hole in their heart at some point in their life! Did that take you back by surprise? Well, all of us while we were embryos had a hole which wasn't a defect but was vital for our survival. This hole has to close with our first exposure to the outside world and if not it could thus lead to a hole being in the heart. But there are cases where the structures of the heart were not properly formed during the development in the embryo. Even this could ultimately lead to the same defect being present in the post-natal life.
There are different types to this. Namely:
Arterial septal defect (ASD)
Ventricular septal defect (VSD)
Patent Ductus Arteriosus (PDA)
Atrioventricular septal defect (AVSD)
Among this I would highlight upon VSD as they are the most common congenital abnormalities of the heart.
What is a Ventricular Septal Defect?
There are different types to this. Namely:
Arterial septal defect (ASD)
Ventricular septal defect (VSD)
Patent Ductus Arteriosus (PDA)
Atrioventricular septal defect (AVSD)
Among this I would highlight upon VSD as they are the most common congenital abnormalities of the heart.
What is a Ventricular Septal Defect?
A ventricular septal defect (VSD) occurs due to the incomplete closure of the ventricular septum. The ventricular septum separates the right and the left ventricles of the heart. This is the most common form of congenital cardiac anomaly. Most VSDs are associated with other congenital cardiac anomalies such as tetralogy of Fallot. Muscular ventricular septal defects are the most common.
Congenital VSDs are usually associated with other congenital conditions such as Down syndrome.
A VSD can also form after a few days of a heart attack. This is due to the mechanical tearing of the septal wall before it is repaired by the body.
In the embryo during the development of the heart on day 20, the heart tube forms a loop towards the right side. The chambers of the heart are formed by day 28. When there is incomplete looping it can result in VSDs.
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| Normal heart showing the interior and how the blood circulates within it. The septum labelled here shows the ventricular septum. In short the blood comes from the superior vena cava and the inferior vena cava into the right atrium and then to the right ventricle. This blood goes to the lungs through the pulmonary trunk. The blood is then returned to the heart by the pulmonary veins to the left atrium and the left ventricle and then it is pumped into the aorta which will pump the blood to the entire body. |
What really happens to the heart then?
During the beating of the heart, both the atria and the ventricles continuously contract (systole) and relax (diastole). If there is a VSD, when the left ventricle contracts (ventricular systole) some of the blood leaks into the right ventricle via the VSD. This then goes through the pulmonary artery into the lungs and from the lungs it enters the pulmonary veins and then the left atrium and thus back into the left ventricle again. This can have two consequences:
- Due to the circuitous refluxing of the blood, there is a volume overload on the left ventricle.
- The systolic pressure of the left ventricle is normally higher than that of the right. Therefore the leakage into the right ventricle causes elevation of the right ventricular pressure and volume and causes pulmonary hypertension. (Increase in pressure of the blood vessels of the lungs)
Key: Ao, aorta; LA, left atrium; LV, left ventricle; PT, pulmonary trunk; RA, right atrium; RV, right ventricle
How do you know that you have a VSD?
Large VSDs cause difficulties virtually from birth. 50% of muscular VSDs close spontaneously. Large defects are usually membranous or infundibular and cause significant left to right shunting of blood. Therefore it causes right ventricular hypertrophy and pulmonary hypertension from birth. However irreversible pulmonary disease develops in essentially all persons with large, unclosed VSDs which ultimately results in shunt reversal, cyanosis and death.
They are usually asymptomatic at birth and manifest usually a few weeks after birth.
Since the blood is shunted from left to right there is no cyanosis. Cyanosis is seen in the right to left shunting of blood. This is due to the deoxygenated blood of the right ventricle mixing with the left ventricle. A bluish discolouration to the skin and the mucous membranes is imparted. Patients with large VSDs present with breathlessness, poor feeding and failure to thrive in infancy.
How is it diagnosed?
When the patient visits the doctor, he does a cardiac auscultation (listening for the heart sounds using a stethoscope) on the patient which will reveal murmurs (abnormal heart sounds). This indicates a significant VSD. The murmur depends on the abnormal flow of blood from the left to the right ventricle. If the pressure difference is not much then the blood flow via the VSD would not be so great therefore the VSD remains silent. This can happen in 3 cases:
- In the foetus when the pressure of both ventricles are equal
- A short time after birth
- A late complication of unrepaired VSD
To confirm the murmur an echocardiography (an ultrasound of the heart) or cardiac catheterization (insertion of a catheter into the heart and is viewed by x-ray fluoroscopy) can be done.
What is the treatment?
Generally surgical or catheter based closure of asymptomatic VSDs are delayed beyond infancy in hope of spontaneous closure. However in babies with large defects early correction must be performed to prevent the development of irreversible obstructive pulmonary vascular disease.
In cases where surgery is required, a heart-lung machine is used and a median sternotomy (a surgical procedure in which a mid-line incision is made along the breast bone and after that the bone is cracked to reveal the heart) is performed. Percutaneous endovascular procedures (gaining access to the tissues and organs of the body via the large blood vessels through needle puncture of the skin) are less invasive and can be done on a beating heart, but are only suitable for certain patients.
Complications in the repair of VSDs occur due to that fact that the conducting system (allows electrical impulses to travel through the heart) of the heart is close to the area being operated.
VSDs are initially treated in infants with cardiac glycosides, loop diuretics and ACE inhibitors.
Source: Text from Robbins & Cortan; Pathologic Basis of Disease 8th Edition and Wikipedia
Images from Robbins & Cortan; Pathologic Basis of Disease 8th Edition and www.nhlbi.nih.gov
Source: Text from Robbins & Cortan; Pathologic Basis of Disease 8th Edition and Wikipedia
Images from Robbins & Cortan; Pathologic Basis of Disease 8th Edition and www.nhlbi.nih.gov
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