Role of Percutaneous Interventions in Adult Congenital Heart Disease
- Volume 20 - Issue 12 - December, 2008
- Posted on: 12/2/08
- 0 Comments
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Congenital heart disease (CHD) is a major public health problem that is largely underrecognized. Surgical and medical advances over the past decades have dramatically improved the once bleak prognosis of patients with CHD. Eighty-five percent of infants born with congenital anomalies can now expect to reach adulthood. The current estimates of the prevalence of adult CHD in North America is 0.9 million.1,2 According to a recent population-based study, there are now more adults with severe CHD than children.2 Adults with both operated and unoperated CHD present with complex problems requiring long-term and close follow-up. The American College of Cardiology and American Heart Association (ACC/AHA) recently came out with guidelines on the management of adults with congenital heart disease (ACHD).3 The percutaneous interventional approach is becoming increasingly recognized as an alternative to surgery for a wide range of CHDs. For adult cardiologists in clinical practice, it is extremely important to have a sound understanding of CHD and the role of percutaneous interventions in the management of these disorders.
Atrial Septal Defect. Incidence. Atrial septal defects (ASD) account for 6–10% of all CHDs, and is the most common congenital heart defect diagnosed in adulthood.4 There are four types of ASDs, the most common being the ostium secundum ASD that is located in the area of the fossa ovalis, and accounts for 75% of all ASDs. It occurs due to either excessive resorption of the septum primum or from deficient growth of the septum secundum. An ostium primum ASD is usually associated with a group of defects that originate from the absence of an atrioventricular septum. A sinus venosus-type ASD is situated high in the septum at the cardiac junction of the superior vena cava and is usually associated with partial anomalous pulmonary venous return. Coronary sinus ASDs are rare and arise from an opening of the wall with the left atrium, allowing for atrial shunting.5
Indications for closure. Patients with uncorrected ASDs can reach old age, but have been shown to have a shortened life expectancy.6 On the other hand, the survival rate of young patients who have undergone surgical closure of an ASD is comparable to an age-matched control population.7 Long-term studies with surgical correction have shown excellent outcomes, with low morbidity and mortality. However, the surgical approach is associated with perioperative complications, longer hospital stays, and time away from work. Percutaneous ASD closure has thus been offered as an alternative to surgical repair.
The ACC/AHA Committee on ACHD recently released recommendations on interventional or surgical closure of ASDs.3 The presence of an enlarged right atrium or ventricle is considered a Class I indication for closure, regardless of symptoms. In patients with ASD, left-to-right shunting causes volume overload of the right heart, leading to right ventricular dilatation and elevation of pulmonary artery pressure. This is usually seen when the ratio of pulmonary-to-systemic blood flow (Qp/Qs) is > 1.5.5,8 Brochu et al showed that in asymptomatic or mildly symptomatic adults, there was subnormal VO2 max, even with modest left-to-right shunting (Qp/Qs 1.2–2.0), and that percutaneous closure improves exercise capacity, hemodynamics and right ventricular dimensions after 6 months.9 The presence of paradoxical embolism, regardless of the ASD diameter or shunt severity, is a Class IIa indication for closure.3
Surgical closure is considered the standard of therapy for ostium primum, sinus venosus and coronary sinus ASDs. Percutaneous closure of secundum ASDs is considered acceptable if certain criteria are met, as listed in Table 1. Transesophageal echocardiography (TEE) with agitated saline provides most, if not all, of the information needed in the evaluation of an ASD. The ACC/AHA guidelines do not require diagnostic cardiac catheterization for uncomplicated ASDs in younger patients with adequate noninvasive imaging.
In patients with an ASD and advanced pulmonary hypertension, it is recommended that careful assessment be performed prior to closure of the defect, since it may be serving as a relief valve, and repairing it could result in further elevations in pulmonary pressures and a drop in cardiac output. One way to assess the feasibility of repair is through right heart catheterization and pulmonary vasodilator testing. Another method is to transiently occlude the defect with a balloon and to examine the effect on pulmonary and systemic pressures.8,10
Surgery versus percutaneous intervention. Several nonrandomized studies have compared percutaneous ASD closure to surgical repair. The largest concurrent, nonrandomized multicenter study was reported by Du et al.11 They followed a total of 614 patients with secundum ASDs, in which 442 were assigned to the device group and 154 to the surgical group. The procedural success rate (no significant residual shunt) was 95.7% for the former and 100% for the latter. Efficacy rates (defined as successful closure without major complications and without a need for surgical intervention) were not significantly different between the two groups on discharge (94.8% vs. 96.1%), at 12 months (98.5% vs. 100%) and after the 2-year study period (91.6% vs. 89.0%). However, the complication rate was statistically higher (24%) for the surgical group compared to the device group (7.2%), which was largely influenced by more pericardial effusion with or without tamponade in the surgical group (p < 0.001). There were no mortalities in either group. Similar findings were observed in a series of 103 patients in Thailand.12
Several improvements have been made to ASD occluder devices, delivery systems and percutaneous techniques since they were first described in 1976.13 Currently, percutaneous closure of secundum ASDs is performed through a femoral venous approach. The defect is crossed with a multipurpose catheter and a sizing balloon is inflated across the septum to determine the diameter. The occlusion device is deployed with the help of TEE and fluoroscopy, and is unscrewed from its cable once in the desired position (Figure 1).
The most frequently implanted ASD devices are the CardioSEAL/STARflex devices (CS/SF) (NMT Inc., Boston, Massachusetts), the Amplatzer Septal Occluder (ASO) (AGA Medical Group, Golden Valley, Minnesota), and the Helex Septal Occluder (HSO) (W.L. Gore and Associates, Flagstaff, Arizona) (Figure 2). The self-centering CS/SF incorporates a self-adjusting flexible spring system so that it can automatically adjust to different shapes and locations of ASDs.14 Initial studies have shown procedural success in 92.5% of cases. Some criticisms of the device include a complicated implantation technique and an inability to close defects > 2.0 cm in diameter. A newer device, the ASO, was approved by the U.S. Food and Drug Administration (FDA) in 2003. A head-to-head comparison of the two devices was made by Butera et al in 274 patients with small-to-moderate (up to 18 mm) ASDs.15 They found that the procedure and fluoroscopy time was shorter in the ASO group. Residual shunting during the procedure and at discharge was significantly more frequent in the CS/SF group. At 1-, 12- and 24-month follow up, the CS/SF group still had higher rates of residual shunting, with ASO achieving 100% complete occlusion after 1 month. Similar success rates were observed by Masura et al in 151 patients using the ASO after a median follow up of 78 months.16 The use of the Helex device in comparison to surgical closure was reported by Jones et al, who showed similar closure success (98.1% vs. 100%) and clinical success after 12 months (91.7% vs. 83.7%; p < 0.001, significant for noninferiority).17
Clinical outcomes with percutaneous intervention. Several authors have reported their experiences with percutaneous closure of secundum ASDs in the past decade (Table 2). In most patients, a defect in the interatrial septum can be occluded by a single device. However, around 2% of cases may require several devices due to multiple or complex fenestrated defects.18 In a registry of 33 patients with large secundum ASDs (> 30 mm but < 45 mm), Lopez et al reported that using the 40 mm ASO resulted in procedural success in 28/33 patients (85%). Of the 5 unsuccessful attempts, 2 involved device embolization and 1 had left atrial wall perforation, all requiring emergent surgery. No major complications were observed after a 6-month follow up period.19 In the series by Post et al evaluating failure rates of the different devices, 6.2% had device embolization requiring immediate surgery, all involving use of the CS/SF device with larger diameters.20
Cardiac perforation is a rare, life-threatening and often avoidable complication of transcatheter closure.21 Divekar et al noted that late perforations account for two-thirds of all reported events, with 1 occurring as many as 3 years after device implantation. It occurs predominantly in the antero-superior walls and the adjacent aorta.22
Ventricular Septal Defect. Incidence. After a bicuspid aortic valve, ventricular septal defects (VSD) are the most common form of CHD, accounting for 20% of all congenital heart abnormalities.23 However, in the adult population, VSD is a rare diagnosis, with the estimated prevalence being only 0.3 in 1000.1 This is because moderate- to large-sized VSDs are usually recognized in childhood due to clinical symptoms that require closure. On the other end of the spectrum, most small-sized VSDs remain asymptomatic in childhood, and 90% close spontaneously by 10 years of age.23 VSDs encountered initially in adulthood (age > 20 years) are unlikely to close spontaneously. They may be asymptomatic or present with left-heart volume overload, pulmonary hypertension, aortic regurgitation, cardiac arrhythmia or infective endocarditis.24 Anatomically, these defects are located either in the perimembranous (more common) or muscular part of the septum. Patients with atrioventricular canal defects or inlet VSDs rarely survive into adulthood due to severe symptoms and pulmonary hypertension.
Indications for VSD closure. According to the recently-published ACC/AHA Guidelines, Class I indications for VSD closure in adults include: i) hemodynamically significant shunt with Qp/Qs ≥ 2.0 and clinical evidence of left ventricular (LV) overload; and ii) a history of infective endocarditis.3,24–26 Closure of a VSD is considered reasonable (Class IIa) when the Qp/Qs is > 1.5 with: i) pulmonary artery pressure less than two-thirds of systemic pressure and pulmonary vascular resistance (PVR) less than two-thirds of systemic vascular resistance; or ii) in the presence of LV systolic or diastolic failure.