**4. Discussion**

#### *4.1. Changes in Soil and Litter Chemical Characteristics*

The transformation of vegetation-stand types has a certain impact on the physical and chemical properties of soil as well as litter and nutrient cycling [31]. Compared with Japanese cedar forests, the soil NH4 +-N contents of mixed 2 and moso bamboo increased significantly, soil and litter organic matter carbon decreased significantly, and total nitrogen showed a trend of first increasing and then decreasing. The carbon–nitrogen ratio of Japanese cedar forest was significantly higher than that of moso bamboo, indicating that Japanese cedar forest has strong carbon-sequestration ability and strong carbon-assimilation ability. So, the expansion of moso bamboo in Japanese cedar forests has a certain impact on the soil carbon and nitrogen cycle. However, due to the characteristics of moso bamboo, the expansion of moso bamboo will lead to the death of other surrounding plants due to the failure of nutrient competition. Therefore, the underground biomass of plants will decrease, resulting in a decrease in soil organic carbon and total nitrogen content [10]. Conversely, the decreased soil organic carbon and total nitrogen may be related to the decomposition rate of the litter. The rate of decay of Japanese cedar litter is lower than that of moso bamboo litter. This may, therefore, accelerate the degradation of soil organic carbon and the total nitrogen absorption of moso bamboo forests [32,33]. The total nitrogen content of the soil under moso bamboo expansion decreased, indicating that the overall absorption of nitrogen during moso bamboo expansion was higher than that of Japanese cedar, which may be related to the increased available nitrogen in the plant. Moso bamboo expansion resulted in increased soil pH, which may have altered some ammonia-oxidizing bacteria and ammonia-oxidizing archaea or may also be due to changes in chemical properties such as cation exchange [34].

#### *4.2. Changes in Fungal Community Structure*

In this study, there were great differences in the soil fungal-community structure among the four stand structures. Changes in vegetation types will also alter soil fungal communities. The number of soil fungi OTUs of moso bamboo showed an increasing trend. The soil fungi diversity, as measured by the Chao1 and observed species indexes, indicated that *Basidiomycota* and *Mucoromycota* were significantly higher in mixed 2 and moso bamboo than in Japanese cedar. Therefore, the expansion of moso bamboo in Japanese cedar forests significantly increased soil fungal diversity, resulting in increased number of soil pathogens and symbiotic groups, altered soil fungal community structure and function, and enzyme activities [35]. The expansion of moso bamboo is also associated with differences in plant biomass inputs and outputs, thus affecting the composition of soil microbial communities [36,37].

#### *4.3. Changes in Bacterial Community Structure*

Soil bacteria are sensitive indicators of soil change. Increased plant diversity leads to increased soil microbial diversity. In this study, in terms of the simple index of bacterial diversity, *Acidobacteria*, *Chloroflexi*, and *Gemmatimonadetes* were significantly higher in Japanese cedar and mixed 1 than in moso bamboo. This is consistent with the findings of Lin et al. [24], whereby the expansion of moso bamboo reduced the plant diversity and the soil microbial bacterial-community structure and diversity. The allelopathy produced by the leaves of moso bamboo leads to a decrease in the diversity of the bacterial-community structure [13]. Additionally, plant diversity decreases with moso bamboo expansion, resulting in weakened competition between vegetation types, which, in turn, gradually increases the mutual benefit and encourages the frequent exchange of substances between the rhi-

zosphere, and the resulting changes in rhizosphere exudates and decline in community productivity may lead to changes in the composition of the bacterial community [34].

#### *4.4. Relationship between Soil Physical and Chemical Properties and Microbes of Moso Bamboo*

The transformation of vegetation types plays a vital role in the structure of the soil microbial community [28]. This is mainly related to changes in the chemical composition of litter and root exudates and related soil carbon and nitrogen substrate concentrations, which alter the soil microbial activity and community structure [22,38]. Farmers picking bamboo shoots can cause disturbances to the soil. This process is similar to tillage and may reduce soil organic-matter content, which in turn alters bacterial communities [24]. Japanese cedar has high soil carbon and nitrogen content, has complex bacterial microbial diversity and community structure, and is associated with leaf density [26,39]. Understory plants and rhizosphere resources, such as root exudates and nutrient content, all affect the structure of the soil microbial community. Soil fungal communities are decomposers of soil organic matter [40]. Xiao et al. [41] found that soil organic carbon mineralization is directly affected by fungal diversity, and fungal diversity is also affected by pH. In this study, the expansion of soil organic carbon and total nitrogen in moso bamboo was significantly negatively correlated with fungal community diversity (Chao1 and observed species) and species abundance (*Basidiomycota* and *Mucoromycota*).

Compared with soil fungi, the soil bacterial-community structure is more sensitive to soil physical disturbances and changes in chemical properties [42]. In this study, moso bamboo increased the soil organic matter carbon and total nitrogen, and the simple bacterialdiversity index indicated that *Acidobacteria*, *Chloroflexi*, and *Gemmatimonadetes* all exhibited a downward trend. The number of soil bacterial OTUs was significantly higher than the number of fungal OTUs. There were certain differences in the soil microbial-community structure among the four forest-stand structures, demonstrating that the differences among different vegetation types have shaped different soil bacterial communities. The differing chemical compositions of the root exudates produced by different forest-stand structures will have a certain impact on the soil bacterial community structure.


**5.1.5 Management**

Despite lack of symptoms at presentation, closure of the ASD is recommended so as to 1) prevent development of pulmonary vascular obstructive disease later in life, 2) reduce chances for supra-ventricular arrhythmias and 3) prevent development of symptoms during adolescence and adulthood. Elective closure around age 4 to 5 years is recommended. Closure during infancy is not undertaken unless the infant is symptomatic. Right ventricular volume overloading by echocardiogram and a Qp:Qs >1.5 (if the child had cardiac catheterization) are indications for closure.

The conventional treatment of choice is surgical correction. While the secundum ASDs can be successfully repaired by open-heart surgical techniques with a low (<1%) mortality, the morbidity with cardiac surgery is universal, and residual scar is present in all. Because of this reason several transcatheter methods have been developed. Clinical trials have been undertaken in a large number of patients with Bard clamshell septal occluder and buttoned device and feasibility and effectiveness of these devices in occluding the ASD have been demonstrated. Fractures of one or more arms of the clamshell device with occasional embolization, has prompted the investigators and the FDA to withdraw the device from clinical trials. The buttoned device has undergone clinical trials and, immediate and shortterm follow-up results are encouraging (Rao et al 1994). Recently, a large number of other devices (Das Angel-Wing, ASDOS, Amplatzer, CardioSeal, Helex and others) have been introduced and clinical trials began (Chopra and Rao 2000). However, Amplatzer and Helex are the only devices that are approved by FDA for general clinical use. The experience with Amplatzer for most defects has been encouraging. Helex device is only useful in small to medium-sized defects.

Ostium primum and sinus venosus defects are not amenable to transcatheter closure and surgical correction is the treatment of choice. In the ostium primum defect, apart from closing the ASD, the mitral valve should be repaired in such a manner as to preserve its function. In the sinus venosus defect, diversion of the anomalously connected pulmonary veins into the left atrium along with the closure of the ASD should be undertaken.

### **5.2 Ventricular septal defect**

Ventricular septal defect (VSD) is the most common CHD and constitutes 20% to 25% of all CHDs. The defect may be small, medium or large and is classified based on its location in the inter-ventricular septum (Fyler 1992). The defect is most commonly (80%) located in the membranous septum, in the subaortic region and is commonly referred to as perimembranous defect. The defect may also be located in the conal septum in the subpulmonary region and is called supracristal defect and constitutes 5% to 7% of VSDs. This type of defect is more commonly encountered in the Far East including Japan and may constitute up to 29% of VSDs. The third type, in the posterior septum, is commonly referred to as atrioventricular canal defect and approximately 8% of the VSDs are of this type. Finally, the defect may be located in the muscular and apical portion of the ventricular septum and may make-up 5% to 20% of all VSDs, depending on the study selected. When multiple muscular defects are seen, it is often referred to as "Swiss-cheese" type of VSD.

### **5.2.1 Symptoms**

18 Congenital Heart Disease – Selected Aspects

Selective angiography in the right upper pulmonary vein at its junction with the left atrium in a left axial oblique view will reveal location and the size of the ASD. When anomalous pulmonary venous connection is suspected, selective left or right pulmonary arterial angiography should be performed and the levophase of angiogram should be scrutinized

Despite lack of symptoms at presentation, closure of the ASD is recommended so as to 1) prevent development of pulmonary vascular obstructive disease later in life, 2) reduce chances for supra-ventricular arrhythmias and 3) prevent development of symptoms during adolescence and adulthood. Elective closure around age 4 to 5 years is recommended. Closure during infancy is not undertaken unless the infant is symptomatic. Right ventricular volume overloading by echocardiogram and a Qp:Qs >1.5 (if the child had cardiac

The conventional treatment of choice is surgical correction. While the secundum ASDs can be successfully repaired by open-heart surgical techniques with a low (<1%) mortality, the morbidity with cardiac surgery is universal, and residual scar is present in all. Because of this reason several transcatheter methods have been developed. Clinical trials have been undertaken in a large number of patients with Bard clamshell septal occluder and buttoned device and feasibility and effectiveness of these devices in occluding the ASD have been demonstrated. Fractures of one or more arms of the clamshell device with occasional embolization, has prompted the investigators and the FDA to withdraw the device from clinical trials. The buttoned device has undergone clinical trials and, immediate and shortterm follow-up results are encouraging (Rao et al 1994). Recently, a large number of other devices (Das Angel-Wing, ASDOS, Amplatzer, CardioSeal, Helex and others) have been introduced and clinical trials began (Chopra and Rao 2000). However, Amplatzer and Helex are the only devices that are approved by FDA for general clinical use. The experience with Amplatzer for most defects has been encouraging. Helex device is only useful in small to

Ostium primum and sinus venosus defects are not amenable to transcatheter closure and surgical correction is the treatment of choice. In the ostium primum defect, apart from closing the ASD, the mitral valve should be repaired in such a manner as to preserve its function. In the sinus venosus defect, diversion of the anomalously connected pulmonary

Ventricular septal defect (VSD) is the most common CHD and constitutes 20% to 25% of all CHDs. The defect may be small, medium or large and is classified based on its location in the inter-ventricular septum (Fyler 1992). The defect is most commonly (80%) located in the membranous septum, in the subaortic region and is commonly referred to as perimembranous defect. The defect may also be located in the conal septum in the subpulmonary region and is called supracristal defect and constitutes 5% to 7% of VSDs. This type of defect is more commonly encountered in the Far East including Japan and may constitute up to 29% of VSDs. The third type, in the posterior septum, is commonly referred to as atrioventricular canal defect and approximately 8% of the VSDs are of this type.

veins into the left atrium along with the closure of the ASD should be undertaken.

for anomalous connections.

catheterization) are indications for closure.

**5.1.5 Management**

medium-sized defects.

**5.2 Ventricular septal defect**

The clinical symptomatology is largely dependent upon the size of the VSD. In small defects, the patients are usually asymptomatic and are detected because a cardiac murmur heard on routine examination. Patients with medium and large defects may present with symptoms of congestive heart failure (dyspnea, tachypnea, sweating and failure to gain weight) or with symptoms related to bronchial obstruction and/or respiratory infection.

#### **5.2.2 Physical findings**

These, again, depend upon the size of the defect. In small defects the only abnormality is a loud holosystolic murmur (Figure 1 bottom) heard best at the left lower sternal border and is sometimes referred to as "maladie de Roger". Sometimes, the holosystolic murmur may be heard best at left mid and left upper sternal borders, depending upon the direction of the VSD jet. In very small defects, murmur, though begins with first heart sound, may not last through the entire systole; the shorter the murmur, the smaller is the defect.

In medium and large defects, the right and left ventricular impulses are increased and somewhat hyperdynamic. A thrill may be felt at the left lower sternal border. The second heart sound is split unless there is pulmonary vascular obstructive disease, in which case a loud single second heart sound is heard. The pulmonary component of the second sound may be normal or increased, depending upon the degree of elevation pulmonary artery pressure. Clicks are unusual for VSD patients although they can be heard in patients whose VSDs are undergoing spontaneous closure by aneurysmal formation of the membranous ventricular septum. A holosystolic murmur is best heard at the left lower sternal border and does not usually radiate although it may be heard widely over the precordium. The intensity of the murmur may vary between grades II-V/Vl. There is no significant variation of this murmur with respiration. This murmur is produced by flow across the VSD. The intensity of the murmur does not bear any consistent relationship with the size of the defect. A grade I-II/Vl mid-diastolic flow rumble may be heard at the apex in patients with medium to large-sized defects and large left-to-right shunts; this murmur is heard best with the bell of the stethoscope. The mid diastolic murmur is due to increased flow across the mitral valve and usually indicates a Qp:Qs greater than 2:1.

#### **5.2.3 Noninvasive evaluation**

#### **<IP_ADDRESS> Chest x-ray**

The x-ray shows cardiomegaly and increased pulmonary vascular markings if the shunt is large. Left atrial enlargement may be noted.

#### **<IP_ADDRESS> Electrocardiogram**

The ECG may be normal in very small defects or may show evidence for left ventricular hypertrophy in small to moderate defects while it may show biventricular or right ventricular hypertrophy in moderate to large defects. Electrocardiographic signs of left atrial enlargement may also be seen.

Congenital Heart Defects – A Review 21

Many of the issues that require definition by catheterization in the past can be resolved by good quality echo-Doppler studies and catheterization is not routinely required. When

Step-up in oxygen saturation is observed in the right ventricle. The saturations in the leftside of the heart are usually normal. The right ventricular and pulmonary arterial pressures are normal in small VSDs and are elevated in moderate to large defects; the magnitude of elevation is proportional to the size of the VSD. Calculated Qp:Qs gives an estimate of degree of left-to-right shunting. A Qp:Qs greater than 2:1 is generally considered an

questions cannot be satisfactorily answered, cardiac catheterization may be useful.

indication for intervention. Pulmonary vascular resistance may be calculated:

oxide[NO]) should be administered to demonstrate the reversibility.

important in the management of children with these defects.

by aneurysmal formation of the membranous ventricular septum.

reduce the incidence of development of pulmonary vascular disease.

**<IP_ADDRESS> Pulmonary vascular obstructive disease**

**<IP_ADDRESS> Development of infundibular stenosis.**

demonstrate size and location of the VSD.

PVR = (Mean PA presence - Mean LA pressure)/Pulmonary blood flow index

Where, PVR is pulmonary vascular resistance, PA and LA are pulmonary artery and left

The calculated resistance is usually 1 to 2 units and a resistance in excess of 3.0 units is considered elevated. Marked elevation of the resistance (>8.0 units) contraindicates surgical repair. When the resistance is elevated, oxygen and other vasodilating agents (Nitric

Selective left ventricular angiography in a left axial oblique view is usually required to

Knowledge of the natural history of these defects is interesting and such understanding is

Approximately 40% of VSDs spontaneously and completely close. Additional 25% to 30% of defects may become small enough not to require surgical intervention. Muscular VSDs tend to close more frequently than membraneous defects. While small defects tend to close more frequently than large defects (60% vs. 20%), even defects large enough to produce congestive heart failure or require pulmonary artery banding in infancy go on to close spontaneously. The majority of the defects close by age 2 years, most close by age 5 to 7 years, but the process of spontaneous closure continues through adolescence and adulthood. Most commonly the defect closes by apposition of leaflets of the tricuspid valve against it or

Pulmonary vascular obstructive disease may develop in 10% of VSDs. This is probably related to the exposure of the pulmonary vascular bed to high pressure and high flow. Prompt diagnosis and closure of the defect at least prior to 18 months of age is likely to

Development of infundibular stenosis, the so called Gasul's transformation of the VSD may occur in 8% of the defects. There may be specific markers such as right aortic arch and increased angle of the right ventricular outflow tract that may predispose a VSD to undergo Gasul's transformation. While development of infundibular stenosis eventually requires the

**5.2.4 Cardiac catheterization & cineangiography**

atrium respectively.

**Natural history of VSDs**

**<IP_ADDRESS> Spontaneous closure**


**Aluminum Alloys and Aluminum-Based Matrix Composites**

Editors

**Di Feng Qianhao Zang Ying Liu Yunsoo Lee**

Basel • Beijing • Wuhan • Barcelona • Belgrade • Novi Sad • Cluj • Manchester

*Editors* Di Feng Jiangsu University of Science and Technology Zhenjiang, China

Yunsoo Lee Korea Institute of Materials Science (KIMS) Changwon, Korea

Qianhao Zang Jiangsu University of Science and Technology Zhenjiang, China

Ying Liu Nanjing University of Science and Technology Nanjing, China

*Editorial Office* MDPI St. Alban-Anlage 66 4052 Basel, Switzerland

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