Megan C. Sherwood

Management of coronary artery fistulae: Patient selection and results of transcatheter closure

OBJECTIVES We report short-term findings in 33 patients after transcatheter closure (TCC) of coronary artery fistulae (CAF) and compare our results with those reported in the recent transcatheter and surgical literature. BACKGROUND Transcatheter closure of CAF has been advocated as a minimally invasive alternative to surgery. METHODS We reviewed all patients presenting with significant CAF between January 1988 and August 2000. Those with additional complex cardiac disease requiring surgical management were excluded. RESULTS Of 39 patients considered for TCC, occlusion devices were placed in 33 patients (85%) at 35 procedures and included coils in 28, umbrella devices in 6 and a Grifka vascular occlusion device in 1. Post-deployment angiograms demonstrated complete occlusion in 19, trace in 11, or small residual flow in 5. Follow-up echocardiograms (median, 2.8 years) in 27 patients showed no flow in 22 or small residual flow in 5. Of the 6 patients without follow-up imaging, immediate post-deployment angiograms showed complete occlusion in 5 or small residual flow in 1. Thus, complete occlusion was accomplished in 27 patients (82%). Early complications included transient ST-T wave changes in 5, transient arrhythmias in 4 and single instances of distal coronary artery spasm, fistula dissection and unretrieved coil embolization. There were no deaths or long-term morbidity. Device placement was not attempted in 6 patients (15%), because of multiple fistula drainage sites in 4, extreme vessel tortuosity in 1 and an intracardiac hemangioma in 1. CONCLUSIONS A comparison of our results with those in the recent transcatheter and surgical literature shows similar early effectiveness, morbidity and mortality. From data available, TCC of CAF is an acceptable alternative to surgery in most patients.

From Stem Cells to Viable Autologous Semilunar Heart Valve

Background—An estimated 275 000 patients undergo heart valve replacement each year. However, existing solutions for valve replacement are complicated by the morbidity associated with lifelong anticoagulation of mechanical valves and the limited durability of bioprostheses. Recent advances in tissue engineering and our understanding of stem cell biology may provide a lifelong solution to these problems. Methods and Results—Mesenchymal stem cells were isolated from ovine bone marrow and characterized by their morphology and antigen expression through immunocytochemistry, flow cytometry, and capacity to differentiate into multiple cell lineages. A biodegradable scaffold was developed and characterized by its tensile strength and stiffness as a function of time in cell-conditioned medium. Autologous semilunar heart valves were then created in vitro using mesenchymal stem cells and the biodegradable scaffold and were implanted into the pulmonary position of sheep on cardiopulmonary bypass. The valves were evaluated by echocardiography at implantation and after 4 months in vivo. Valves were explanted at 4 and 8 months and examined by histology and immunohistochemistry. Valves displayed a maximum instantaneous gradient of 17.2±1.33 mm Hg, a mean gradient of 9.7±1.3 mm Hg, an effective orifice area of 1.35±0.17 cm2, and trivial or mild regurgitation at implantation. Gradients changed little over 4 months of follow-up. Histology showed disposition of extracellular matrix and distribution of cell phenotypes in the engineered valves reminiscent of that in native pulmonary valves. Conclusions—Stem-cell tissue-engineered heart valves can be created from mesenchymal stem cells in combination with a biodegradable scaffold and function satisfactorily in vivo for periods of >4 months. Furthermore, such valves undergo extensive remodeling in vivo to resemble native heart valves.

Class IA phosphoinositide 3-kinase regulates heart size and physiological cardiac hypertrophy

ABSTRACT Class IA phosphoinositide 3-kinases (PI3Ks) are activated by growth factor receptors, and they regulate, among other processes, cell growth and organ size. Studies using transgenic mice overexpressing constitutively active and dominant negative forms of the p110α catalytic subunit of class IA PI3K have implicated the role of this enzyme in regulating heart size and physiological cardiac hypertrophy. To further understand the role of class IA PI3K in controlling heart growth and to circumvent potential complications from the overexpression of dominant negative and constitutively active proteins, we generated mice with muscle-specific deletion of the p85α regulatory subunit and germ line deletion of the p85β regulatory subunit of class IA PI3K. Here we show that mice with cardiac deletion of both p85 subunits exhibit attenuated Akt signaling in the heart, reduced heart size, and altered cardiac gene expression. Furthermore, exercise-induced cardiac hypertrophy is also attenuated in the p85 knockout hearts. Despite such defects in postnatal developmental growth and physiological hypertrophy, the p85 knockout hearts exhibit normal contractility and myocardial histology. Our results therefore provide strong genetic evidence that class IA PI3Ks are critical regulators for the developmental growth and physiological hypertrophy of the heart.

Prognostic significance of clinically silent coronary artery fistulas

Symptomatic coronary artery fistulas (CAF) are associated with significant morbidity and mortality. With the advent of high-resolution 2-dimensional and color Doppler echocardiography, the detection rate of clinically silent CAF has increased, but their clinical significance and outcome have not been defined. The clinical, echocardiographic, electrocardiographic, and angiographic findings and documented follow-up of 31 patients with an echocardiographic finding of a clinically silent coronary artery fistula from 1986 to 1997 were analyzed. Mean age at diagnosis was 7.2+/-8.4 years. Indications for echocardiography were murmur (n = 23), congenital heart disease (n = 2), cardiomegaly (n = 2), chest pain (n = 1), stridor (n = 1), syncope (n = 1), and chest trauma (n = 1). CAF were detected with color Doppler flow mapping in all patients. The origin of the fistula was from the left coronary artery system (n = 27), right coronary artery system (n = 3), and bilateral (n = 1). The exit sites were the pulmonary artery (n = 18), right ventricle (n = 8), right atrium (n = 2), and left ventricle (n = 3). Global and regional left ventricular function were normal in all patients at presentation and follow-up. Spontaneous closure of the fistula was documented in 7 patients (23%) at mean follow-up of 2.6+/-2.0 years. In 23 patients the fistula persisted without intervention. All patients remained asymptomatic, without adverse clinical events or evidence of ischemia at a mean age at follow-up of 9.3+/-9.1 years (range 4 months to 42.0). Based on this experience, there is no evidence that clinically silent CAF diagnosed incidentally by color Doppler echocardiography are associated with adverse clinical outcome in childhood and adolescence. Conservative management with continued follow-up of these patients appears to be appropriate.

Current Management of Severe Congenital Mitral Stenosis Outcomes of Transcatheter and Surgical Therapy in 108 Infants and Children

Background—Severe congenital mitral stenosis (MS) is a rare anomaly that is frequently associated with additional left heart obstructions. Anatomic treatments for congenital MS include balloon mitral valvuloplasty (BMVP), surgical mitral valvuloplasty (SMVP), and mitral valve replacement (MVR), although the optimal therapeutic strategy is unclear. Methods and Results—Between 1985 and 2003, 108 patients with severe congenital MS underwent BMVP or surgical intervention at a median age of 18 months (range 1 month to 17.9 years). Anatomic subtypes of MS were “typical” congenital MS in 78 patients, supravalvar mitral ring in 46, parachute mitral valve in 28, and double-orifice mitral valve in 11, with multiple types in ≈50% of patients. Additional left heart anomalies were present in 82 patients (76%). The first MS intervention was BMVP in 64 patients, SMVP in 33, and MVR in 11. BMVP decreased peak and mean MS gradients by a median of 33% and 38%, respectively (P<0.001), but was complicated by significant mitral regurgitation in 28%. Cross-sectional follow-up was obtained at 4.8±4.2 years. Overall, Kaplan-Meier survival was 92% at 1 month, 84% at 1 year, and 77% at 5 years, with 69% 5-year survival during the first decade of our experience and 87% since (P=0.09). Initial MVR and younger age were associated with worse survival. Survival free from failure of biventricular repair or mitral valve reintervention was 55% at 1 year among patients who underwent BMVP and 69% among patients who underwent supravalvar mitral ring resection initially. Among patients who underwent BMVP, survival free from failure of biventricular repair or MVR was 79% at 1 month and 55% at 5 years, with worse outcome in younger patients and those who developed significant postdilation mitral regurgitation. Conclusions—BMVP effectively relieves left ventricular inflow obstruction in most infants and children with severe congenital MS who require intervention. However, surgical resection is preferable in patients with MS due to a supravalvar mitral ring. Five-year survival is relatively poor in patients with severe congenital MS, with worse outcomes in infants and patients undergoing MVR, but has improved in our more recent experience. Many patients have undergone second procedures for either recurrent/residual MS or mitral regurgitation resulting from dilation-related disruption of the mitral valve apparatus.

Three-dimensional echocardiography of the atrial septum.

This article details the important contribution of three‐dimensional echocardiography for catheterization device closure of secundum atrial septal defects. Aspects presented include three‐dimensional echocardiographic application in preselection of patients and in selection of the type and size of the atrial septal occluder devices. Unique three‐dimensional echocardiographic imaging planes are shown that depict the size and shape of the defect, the important rim tissue surrounding the defect, and the images that demonstrate successful device placement. Details of the acquisition phase, digital reformatting, and the eventual rendering of standard three‐dimensional echocardiographic imaging planes of the atrial septum are shown. Three‐dimensional echocardiography not only provides important additional information, but also enhances understanding of standard twodimensional studies.

Haploinsufficiency of the cardiac transcription factor Nkx2-5 variably affects the expression of putative target genes

Heterozygous mutations of the cardiac transcription factor Nkx2‐5 cause congenital heart disease. To elucidate the molecular pathways of transcription factor mutant phenotypes or diseases, direct targets are commonly sought in studies of homozygous null mutant animals and by heterologous promoter‐reporter gene transactivation assays. The expression of putative target genes in a physiologic range of transcription factor concentration, however, is often not examined. Heterozygous Nkx2‐5 knockout (Nkx2‐5+/−) mice have no more than half‐normal levels of Nkx2‐5 protein. We therefore measured the mRNA expression of four putative targets of the cardiac transcription factor Nkx2‐5 in wild‐type and Nkx2‐5+/− animals in a variety of developmental and pathologic states. Wild‐type and Nkx2‐5+/− embryonic hearts expressed similar levels of atrial natriuretic factor (ANF), brain natriuretic peptide (BNP), the RNA helicase Csm, and homeodomain only protein HOP. In the failing adult ventricle, ANF and BNP were up‐regulated to the same extent in wild‐type and Nkx2‐5+/− myocardium. Csm and HOP were down‐regulated in heart failure, and Nkx2‐5+/− hearts expressed about half‐normal levels in healthy and failing states. No consistent relationship existed between the expression of putative transcriptional targets and Nkx2‐5 gene dosage in the physiologically relevant range. Any dependence of gene expression on Nkx2‐5 gene dosage is affected by factors specific to the individual gene and the physiologic context.

Noninvasive imaging of the single ventricle

Abstract Single ventricle consists of a group of cardiac malformations that share a common final surgical procedure, the Fontan operation. Echocardiographic evaluation of the anatomy and pathophysiology of these lesions is important in the management of patients prior to, during, and following surgical and transcatheter therapy. Using 2-D imaging, color and spectral Doppler, the cardiologist can assess in detail cardiovascular anatomy, physiology and ventricular function. Advances in ultrasound technology have greatly improved the diagnostic capabilities of fetal echocardiography and a growing number of patients are diagnosed prenatally. Transesophageal echocardiography has an important role in the operating room, in older patients, in the evaluation for thrombus, and in echocardiographic guidance during transcatheter procedures. The role of magnetic resonance imaging (MRI) in the evaluation of patients with single ventricle has increased in recent years as this modality complements echocardiography and overcomes some of its limitations. This article reviews the use of echocardiography and MRI in the initial diagnosis and various stages of palliation of patients with single ventricle.