2012-08-05-10 Ventricular septal defect, muscular © Philippe Jeanty www.thefetus.net
Ventricular septal defect, muscular
2 Inner Vision Women’s Ultrasound, Nashville, Tenessee, US
Synonyms: Trabecular ventricular septal defect, muscular trabecular ventricular septal defects.
Definition: A congenital defect of the ventricular septum at the muscular portion in which there is a communication through the inter-ventricular septum result in shunting flow between the two ventricular cavities.
Muscular ventricular septal defects is the second most common type of ventricular septal defects which includes perimembranous, trabecular (muscular), inlet and outlet ventricular septal defects (Figure 1)
Figure 1: The anatomical regional classification of the ventricular septal defects.
According to the region of the muscular septum defects, some authors also divided into 4 groups: midmuscular, apical, anterior, and posterior in which midmuscular is the most common subtype of muscular ventricular septal defects. 1,4
Multiple muscular ventricular septal defects with a very large communication between the ventricles is also described as "Swiss cheese" ventricular septal defects.
Prevalence: The prevalence of muscular ventricular septal defects in population has not been well documented.
The incidence of mucular ventricular septal defects reported in some recently research was approximately 24.9-53.2:1000 neonate. 2, 3, 4
Overall, ventricular septal defects are the most common congenital heart defect. The incidence of ventricular septal defects have been currently reported increased from 1.35–4.0/1000 live births to 3.6–6.5/1000 live births11.
Risk factor: Maternal smoking, alcohol consumption, or age are probably not risk factors for ventricular septal defect. Incidence rates are similar in different races and seasons and are unrelated to maternal age, birth order, sex, and socioeconomic status.
Etiology: The causes of congenital malformations of the heart is not well understood, 80 percent of cardiac abnormalities are multifactorial which supposed to be the interaction of the environment and the genetic.
Associated anomalies: Muscular ventricular septal defects can be isolated or associated with other cardiac defects.
Either isolated or associated with the other anomalies, there is an increased risk of chromosomal anomalies.
An isolated ventricular septal defect can be well tolerated and may not cause hemodynamic disturbances in utero. The pressure in both ventricles is similar, and even large ventricle septal defects could cause small bidirectional shunts. Some reports indicate that there is slightly increased systolic pressure in the right ventricle than in the left one, so the shunt would be right to left on systolic and left to right on diastolic15. Other case reports evaluated the direction based on 3 Dopler techniques including Color M mode, Pulsed Doppler, Continuous Doppler and found that there was a bidirectional shunting flow during systole; No shunt flow was detectable during diastole. This phenomenon results from a more rapid increase in systolic pressure in the left ventricle or delayed onset of pressure development in the right ventricle.14
The septation of the ventricle and the outfow tract begins at the end of the fourth weeks, the inferior part of the bulboventricular sulcus begins to protrude into the cardiac lumen along the interface between the presumptive right and left ventricular chambers forming the muscular interventricular. This septum formation halts in the middle of seventh week to wait for the septation of outflow tract and the formation of atrioventricular valves which occurs from 5th to 8th weeks. The further septation of the ventricles and the outflow tract must occur in tight coordination for the properly functional heart. If the fusion of this complex does not properly work at this period, it will not only result in ventricular septal defects but the other cardiac abnormalities as well.
Diagnosis: The muscular septal defects are better visuallized in the four-chamber view with color Doppler than in gray scale.
Many muscular defects are small and will not be desmonstrated by antenatal ultrasound. The large ones can be seen on the 4-chamber view, but angulation of the transducer may be required at times, to magnify the Doppler shift.
Apical defects are also difficult to evaluate on the right ventricular side because they can be covered by trabeculations.
Occasionally, a plume of color signal may reveal their existence. The jets is usually from the left ventricle to the right or from the right to the left during systolic.
Isolated muscular septal defects with small to moderate-sized defects mostly have good prognosis and show a high rate of spontaneous closure in utero and early infancy 9;10 11,3.
A recently research in the population of 2891 neonates reported that 81.8% infants had muscular septal ventricular defect closed spontaneously at 12 months' follow-up in which, 89.2% of mid-muscular type closed within the 1st year of life compared with apical type (70.8%) 4 and anterior type (80%). However, there are no statistically significant difference in rate of closure between anatomic locations nor the size of the defects.1,12
The overall rate of spontaneous closure in ventricular septal defects was 73% by the end of the first year.2
Management:8 An amniocentesis could be recommended because of the association with chromosomal anomalies, mainly trisomy 21, 18 and 13. A careful ultrasound evaluation is necessary. Diagnosis in the third trimester does not alter obstetrical management.
- Ramaciotti C, Vetter JM, Bornemeier RA, Chin AJ. Prevalence, relation to spontaneous closure, and association of muscular ventricular septal defects with other cardiac defects. Am J Cardiol. Jan 1 1995;75(1):61-5
- Lin MH, Wang NK, Hung KL, Shen CT.Spontaneous closure of ventricular septal defects in the first year of life.J Formos Med Assoc. 2001 Aug;100(8):539-42.
- Roguin N, Du ZD, Barak M, Nasser N, Hershkowitz S, Milgram E..High prevalence of muscular ventricular septal defect in neonates.J Am Coll Cardiol. 1995 Nov 15;26(6):1545-8.;
- Chang JK, Jien WY, Chen HL, Hsieh KS. Color Doppler echocardiographic study on the incidence and natural history of early-infancy muscular ventricular septal defect.Pediatr Neonatol. 2011 Oct;52(5):256-60.
- A Sands, F Casey, B Craig, J Dornan, J Rogers, and H Mulholland, Incidence and risk factors for ventricular septal defect in "low risk" neonates.Arch Dis Child Fetal Neonatal Ed. 1999 July; 81(1): F61–F63
- Newman TB. Etiology of ventricular septal defects: an epidemiologic approach. Pediatrics. Nov 1985;76(5):741-9.
- William J. Karsen, Human embryology, Newyork: Churchill Livingstone, 1993, chapter 6: p 143-153.
- Paulo Malkomes, Ventricular septal defect, the fetus.net, 2004
- Hiraishi S, Agata Y, Nowatari M. Incidence and natural course of trabecular ventricular septal defect: two-dimensional echocardiography and color Doppler flow imaging study. J Pediatr. 1992 Mar;120(3):409-15.
- Axt-Fliedner R, Schwarze A, Smrcek J, et al. Isolated ventricular septal defects detected by color Doppler imaging:evolution during fetal and first year of postnatal life. Ultrasound Obstet Gynecol. Mar 2006;27(3):266-73.
- S W Turnera, S Hunterb,J P Wylliea.The natural history of ventricular septal defects.Arch Dis Child 1999;81:413-416
- Paladini D, Palmieri S, Lamberti A, Teodoro A, Martinelli P, Nappi C. Characterization and natural history of ventricular septal defects en the fetus. Obst Ginecol 2000; 16:118-122.
- Allan LD, Sharland GK, Milburn A, et al. Prospective diagnosis of 1006 consecutive cases of congenital heart disease in the fetus. J Am Coll Cardiol 1994;23:1452-1458
- Jean-Paul Lethor, MD; Francois Marçon, MD; Michael de Moor, MD; Mary Etta E. King, MD.Physiology of Ventricular Septal Defect Shunt Flow in the Fetus Examined by Color Doppler M-Mode. Circulation.2000; 101: e93
- Akita A, Harima N, Nawata S, Nakata M, Kato H. Two-dimensional and Doppler echocardiographic evaluation of intrauterine blood flow dynamics in the fetuses with a ventricular septal defect. Nippon Sanka Fujinka Gakkai Zasshi. 1991;43:1606–1612