Perimembranous VSD 中文

心室中膈缺損(Ventricular Septal Defect)

回到常見的心臟血管疾病

一、什麼是心室中膈缺損？

係指左、右心室間有一孔洞，稱為「心室中膈缺損」。
這個缺損對心臟的影響，就是使左心室部分含氧的的鮮血經由此填充到右心室，結果左心室要打到全身的血液量減少，營養供應因此不足， 造成發育不良。而右心室的工作量卻因此增加了，並且流向肺動脈到肺部的血也同時增加；這些額外的負擔，會造成心臟的肥大，進而發生心臟衰竭。

二、心室中膈缺損的分類

根據破洞所在的位置可分為四種類型：

又稱東方人型或高位型，約佔心室中膈缺損的30%，其破洞位置較高，緊接在主動脈瓣及肺動脈瓣的下面，容易造成主動脈瓣脫垂及逆流。 一般建議第一型的病人不論破洞的大小都應接受外科手術，以避免主動脈瓣損壞的不幸後果。手術時間一般認為是一歲左右，若發現主動脈瓣已有異常現象則應提早開刀。

又稱為膜型，它是最常見的心室中膈缺損，約佔50%以上，此型容易有纖維組織增生，形成苞苞把破洞包起來，而使破洞自然縮小，根據統計破洞小者有30-50%的機會可能自然完全閉合，但破洞較大者機會較小。

又稱心內膜墊型或房室腔型，約佔所有心室中膈缺損的5-10%，此型在胚胎發育過程中常合併二尖瓣及三尖瓣隙裂，容易造成瓣膜閉鎖不全，加重心臟負擔，而此型破洞靠近心臟傳導系統，開刀縫合時可能傷到而造成房室傳導阻滯。

又稱肌肉型，約佔心室中膈缺損的5-15%，此型除非破洞太大，通常不需吃藥或開刀，而自然閉合的機會大於80%。

三、心室中膈缺損常見的症狀

一般而言，小的心室中膈缺損是完全不會有症狀的。可能只是有異常的心雜音，或是由於肺部的血液較多， 比較常引起肺部的感染，而常常罹患細支氣管炎及肺炎等疾病，而且拖的時間也比較長，常常要等到二、三個星期的時間，症狀才會完全消失。

而較大的心室中膈缺損則會有心臟衰竭的症狀發生，如呼吸急促等。 如果時間更久一點，可能會合併嚴重的心臟衰竭，而造成肺部積水、肝臟腫大等現象；此時應儘速送醫處理，以免延誤病情。

四、診斷方法

1. 心音：除了在左胸骨緣聽到泛心縮期雜音，可摸到心臟前區的震顫(thrill)。
2. 胸部 X 光：可發現心臟擴大，肺紋（lung marking）增加。
3. 心電圖：可顯示正常或左心室肥大。
4. 心臟超音波：左、右心室有分流。
5. 心導管術：常發現左心房左心室負荷過重及右心室的含氧濃度增加，表示左心室動脈血流向右心室，使得右心室的含氧濃度增加，而且肺動脈的壓力增高。從左心室打入對比劑（contrast media）可發現它進入右心室，進而確定心室中隔缺損的位置及大小。

伍、治療方式

臨床上可利用強心劑(Digoxin毛地黃)及利尿劑(Lasix)、血管擴張劑來控制鬱血性心衰竭情形且須長期追蹤到一歲左右來決定是否開刀。
如果有下列情形之一者，可能需要提早開刀：
a. 不易控制的心衰竭。
b.經常肺部感染。
c.發育遲緩。
d.肺高壓。

陸、預後兩大因素

其實心室中膈（VSD）的預後（即病人的嚴重度，是否需要開刀）最有關係的無非是：1.心室中膈的大小(size),2.心室中膈的位置。
80%的心室中膈缺損都是位於心室中膈膜狀部(Membranousportion）周邊；在這類的心室中膈缺損的病患身上，有許多人在追蹤的過程中，可見到三尖瓣因為受到血流的牽引，逐漸形成所謂「三尖瓣瘤」（Tricuspidaneurysm），遮蓋掉心室中膈甚至完全將心室中膈關閉的情形。其實，絕大多數此類的心室中膈缺損，都是會自行癒合的，是癒後較好的一種心室中膈缺損。 但是，如果心室中膈缺損的大小過『大』，可能在三尖瓣完成覆蓋的手續前，便發生心臟衰竭的情形，那就必須輔以藥物治療。但如果心室中膈缺損真的過大，就只有選擇開刀一途了！

What is a ventricular septal defect?

Ventricular septal defect is the most common congenital heart defect and accounts for 20-30% of children seen in large pediatric cardiology clinics. The exact incidence is not known with estimates ranging from 2 to 5 out of every 1000 babies born. The cause of the problem is not well understood.

A ventricular septal defect (VSD) is a defect or hole(1) in the wall that separates the lower two chambers of the heart. These chambers are called the ventricles (2) and the wall separating them is called the ventricular septum. A child can have single or multiple ventricular septal defects. Ventricular septal defects also occur in association with more complex heart defects such as Tetralogy of Fallot and transposition of the great vessels. The information on this page applies to patients with a ventricular septal defect and an otherwise normal heart.

Ventricular septal defects can be further described by 1) size of the defect, 2) location of the defect, 3) whether there is more than one defect present, and 4) the presence or absence of a ventricular septal aneurysm. The size of the defect is usually described as small, moderate, or large. In general, small defects cause no symptoms during infancy or childhood and often close spontaneously. Moderate and large defects are less likely to close spontaneously, may result in congestive heart failure, and more often require surgical closure. Sometimes, the term restrictive or non-restrictive are used to describe the size of the defect. The term restrictive describes small defects that allow little or no blood to flow from the left side of the heart to the right side of the heart. Non-restrictive defects are large defects that allow a significant amount of blood to flow from the left side to the right of the heart. This results in excessive blood flow to the lungs, high pulmonary artery pressures, extra work for the heart, and congestive heart failure.

Different systems for describing the location of ventricular septal defects are used. Some are located in the lower portion of the septum called the muscular septum. Defects in this location are called muscular ventricular septal defects. Perimembranous ventricular septal defects (also called membranous VSD'S) are located in the membranous septum, a relatively small portion of the septum located near the heart valves. Ventricular septal defects may also be described as inlet or outlet VSDs. These terms further describe where the defect is located. Inlet VSDs are located close to where the blood enters the ventricular chamber and outlet VSDs are located close to where the blood exits the ventricular chamber.

Sometimes a ventricular septal aneurysm is seen when the echocardiogram is done. This is a thin flap of tissue that causes no harm and may increase the chances that the defect will close spontaneously.

What are the effects of this defect on my child's health?

In general, the effects of a ventricular septal defect are related to the size of the defect. As described previously, small ventricular septal defects do not cause symptoms in infancy or childhood and rarely require surgical or medical treatment. The majority of muscular VSDs close spontaneously during early childhood. Membranous VSDs can close at any time if a ventricular septal aneurysm is present. Small ventricular septal defects are not expected to affect the child's growth or development.

Usually, the primary significance of a small ventricular septal defect is a slightly increased risk for subacute bacterial endocarditis (SBE). This is an infection of the heart caused by bacteria in the blood stream. It most commonly occurs after a dental or other medical procedure and can usually be prevented by a dose of antibiotic prior to the procedure.

The effects of larger ventricular septal defects result from the shunting of blood across the defect causing excessive blood flow to the lungs. Ordinarily, the resistance or pressure on the heart's left side is much higher than the pressure on the heart's right side. When there is a large defect, the blood takes the "path of least resistance" and goes back to the right ventricle instead of out to the body. This results in pulmonary overcirculation and extra work for the heart. When the heart is unable to meet this extra work load, symptoms of congestive heart failure develop including excessive sweating (a cold, clammy sweat often noted during feeding), poor feeding, slow weight gain, irritability or lethargy, and/or rapid breathing. If this occurs medicines will usually be started (see treatment options). If the medicines aren't effective, surgery is usually recommended.

A very small number of ventricular septal defects located near the pulmonary valve can result in damage to the aortic valve. When this occurs the aortic valve starts to leak. Since the leakage usually progresses over time, surgical closure of the defect is often recommended even if the defect is small.

Participation in physical activities and sports: Exercise recommendations are best made by the patient's doctor so all so that all relevant factors can be included in the decision. If otherwise healthy, children with small ventricular defects and those with repaired ventricular defects can participate fully in physical activities including vigorous and competitive athletics.

How is this problem diagnosed?

Clinical findings: Most newborns with VSD do not have heart related symptoms. If the defect is moderate to large in size, symptoms of congestive heart failure usually develop during the first 1 to 2 months of life.

Physical findings: A heart murmur is often the first clue that a child has a VSD. In many children, the murmur is heard right after birth but it may not be heard until the child is 6 to 8 weeks of age. If the child is in congestive heart failure, there will be poor weight gain, the heart rate and breathing rate will be higher than normal, and the liver will be enlarged.

Medical tests: Medical tests that provide helpful information include an electrocardiogram, oxygen saturation test, and chest x-ray. The diagnosis is confirmed by an echocardiogram. If there are questions about the child's heart anatomy that can't be answered by the echocardiogram or if the child's symptoms seem out of proportion to the size of the defect, a heart catheterization may be done.

How is the defect treated?

As described earlier, small ventricular septal defects do not cause symptoms so generally treatment (other than SBE prophylaxis) is not needed. Usually, ventricular septal defects diagnosed in infancy get smaller with time and even large defects can close completely. If the child develops congestive heart failure, treatment is needed. This involves the use of medications to decrease the work of the heart and increase the strength of the heart beat. Medications that may be used include digoxin, diuretics, and afterload reducers. These medications often control the symptoms until the child gets bigger and the defect gets smaller or closes altogether.

If the child's symptoms cannot be controlled by medications, surgical repair will be considered. Often the need for surgery is demonstrated most convincingly by the child's inability to gain weight. Even if the symptoms are minimal, surgical closure is recommended for any defect that is big enough after the first year or two of life to allow excessive pulmonary blood flow. This is to prevent a very serious long term complication called pulmonary vascular obstructive disease.

Surgical repair of a ventricular septal defect involves open heart surgery and placement of a prosthetic patch, sutured in placed, that covers the defect. The heart tissue grows over the patch so the heart never "outgrows" it.

Clinics

Care and services for patients with this problem are provided in the Congenital Heart and Cardiovascular Surgery clinics at the University of Michigan Medical Center in Ann Arbor.

What is the outlook for children with ventricular septal defects?

Overall, the outlook for a child with a ventricular septal defect is excellent. As previously described the majority of defects close on their own or are small so that treatment is not needed. Surgical results are also excellent. If the child has only a ventricular septal defect and an otherwise normal heart, the operative mortality approaches 0%. Major complications are rare and include heart block and incomplete closure of the defect. The incidence of major complications is less than 1%.

References

Gumbiner CH & Takao A. Ventricular septal defect. In Garson A, Bricker J, Fisher D & Neish S (Eds), The science and practice of pediatric cardiology, Vol I. Williams & Wilkins: Baltimore, MD, 1997,1119-1140.

Mavroudis C, Backer Cl, & Idriss FS. Ventricular septal defect. In C Mavroudis & C Backer (Eds) Pediatric Cardiac Surgery. Mosby, St. Louis, MO,1994,201-224.

Onat T, Ahunbay G, Batmaz G & Celebi A. The natural course of isolated ventricular septal defects during adolesence. Pediatr Cardiol 19:230-234, 1999.

The natural history of isolated VSD was studied in 106 patients from infancy through puberty. There was a 22 % closure rate during adolescence which was higher than anticipated. Stature was normal with a significantly lower weight which increased to normal by the end of adolescence. Using Kaplan-Meier curves, 61% of muscular defects and 50% of perimembranous defects closed spontaneously prior to adolescence. Spontaneous closure during adolescence was much higher than anticipated with implications when considering surgical closure. The majority of muscular VSDs close during the first year of life and perimembranous defects could close in any period of life with the development of VSA. Higher rate of closure in infancy and adolescence when growth is rapid suggests a role in spontaneous closure.

Written by: S. LeRoy RN, MSN

Reviewed September, 2012