Incremental Value of Three-Dimensional Echocardiography Over Transesophageal Multiplane Two-Dimensional Echocardiography in Qualitative and Quantitative Assessment of Cardiac Masses and Defects

In the present study, we compared three-dimensionally (3-D) reconstructed images with multiplane two-dimensional (2-D) transesophageal echocardiographic (TEE) images in 17 patients with various cardiac masses and defects. To overcome the problem of making measurements from 3-D reconstructed images, we carefully "dissected" the 3-D dataset using paraplane and anyplane 2-D sections, which were then used to obtain the maximum sizes of the cardiac masses and defects. Of the 15 vegetations and 9 abscesses detected by 3-D TEE in 7 patients, only 8 (53%) vegetations and 4 (44%) abscesses were detected by multiplane 2-D TEE (P < 0.02). Also, the exact anatomical location, shape, geometry, and extent of various cardiac masses and defects were more clearly delineated by 3-D than 2-D TEE. The maximum dimensions of cardiac masses and defects were larger by 3-D than by 2-D TEE in 17 (89%) of the 19 lesions available for comparison (P < 0.002). In addition, 3-D TEE correlated more closely than 2-D TEE when compared to surgical measurements in three patients in whom they were available. Thus, it would appear that in several instances, the exact size of the cardiac lesion could only be assessed by analysis of the 3-D volumetric dataset. Out preliminary study has demonstrated the superiority of transesophageal 3-D reconstruction over multiplane 2-D TEE in both qualitative and quantitative assessment of various cardiac mass lesions and pathological defects.     

Surgical Treatment of Double Inlet Ventricle ("Single Ventricle")

The surgical techniques described are the result of an evolution over a number of years in the performance of the septation operation and the modified Fontan-Kreutzer repair for patients with double inlet ventricles. Those with associated pulmonary stenosis are best palliated by a classical Blalock-Taussig or Goretex shunt if an operation is required during the first few years of life and later, between two and four years of age, definitive repair by the modified Fontan-Kreutzer operation is advised. Although controversial, we prefer the use of a large nonvalved right atrial-pulmonary artery connection. Ventricular septation remains the best definitive surgical option when pulmonary stenosis is absent or mild. It is contraindicated by severe pulmonary vascular disease and also by less than moderate ventricular enlargement. The need for concomitant AV valve replacement and the use of an extracardiac conduit are associated with increased hospital mortality in our experience. Infants identified during the first year of life who do not have pulmonary stenosis are a difficult subset to manage. If the VSD and subaortic area is large and unobstructed, pulmonary artery banding early in life will control pulmonary vascular resistance and from this standpoint, permit these patients to become ultimately suited to a modified Fontan-Kreutzer repair. Unfortunately, ventricular hypertrophy usually results from pulmonary artery banding and has been associated with higher hospital mortality at the time of definitive repair. When pulmonary artery banding is undertaken for this subset, debanding and definitive repair seems best advised at about two years of age. Pulmonary artery banding is well known to accelerate the development of subaortic stenosis by spontaneous progressive restriction of the VSD. This results in small ventricular cavity size and increased ventricular hypertrophy, which are incremental risk factors for increased hospital mortality by either definitive procedure. When the VSD or subaortic area is narrow and the patient is identified during the first year of life, isolated pulmonary artery banding is inappropriate. The surgical options for these patients include Ebert's two-stage management program consisting of the initial placement of a loose partial septation patch with concomitant pulmonary artery banding, and later debanding and complete septation. Alternatively, a trial of primary complete septation may be warranted, or the use of a procedure consisting of division of the main pulmonary artery with distal closure and anastomosis of the proximal portion to the side of the ascending aorta, coupled with a systemic-pulmonary artery shunt.     

Transesophageal Echocardiographic Findings in Primary Leiomyoma of Inferior Vena Cava

We describe for the first time the usefulness of transesophageal echocardiography for the identification of a primary leiomyoma of the inferior vena cava, which originated near its junction with the right atrium. A portion of the tumor was initially visualized in the right atrium during a transthoracic echocardiographic study, but its attachment in the inferior vena cava was evident only by transesophageal echocardiography using the transgastric approach. (ECHOCARDIOGRAPHY, Volume 10, November 1993)     

Right Side Implant of the Unipolar Single Lead Defihrillation System

The active can defibrillator has been designed for implantation in the left prepectoral region. Whether this system can be successfully implanted on the right side is unknown. We describe six cases in which placement of the unipolar single lead defibrillation system was successfully attempted in the right prepectoral region due to impediments on the left side. The mean age of the patients was 62 ± 12 years. Five patients had is–chemic heart disease and one idiopathic dilated cardiomyopathy. The endocardial defibrillation electrode was placed in the right ventricle through the right subclavian vein and positioned at the apex in two patients and in the septal position in four patients. Defibrillation threshold testing was performed using a step-up/step-down protocol beginning at 12 J with 3-J increments or decrements. Defibrillation threshold was defined as the lowest energy of the first shock able to terminate ventricular fibrillation. The generator models used were the Medtronic 7218C in 1 patient, the Medtronic 7219C in 3 patients, and the Ventritex Cadet 115 AC in 2 patients. The mean defibrillation threshold was 15 ± 3 J. The defibrillation thresholds were retested at 1,3, and 6 months, and showed no significant change in five patients but decreased from 15 J to 12 J in one patient. The presence of impediments on the left side should not preclude attempts to place the unipolar active can system in the right prepectoral region.     

Improved Spatial Resolution for Cardiac Mapping Using Current Source Density-Based Electrode Arrays

The time of the minimum slope (i.e., the fastest negative deflection) in monopolar (MP) electrograms from normal hearts compares closely with time of phase 0 of the action potential in cells underlying the electrode, but poor rejection of far-field activity may limit the utility ofMP electrode technology in dense arrays used for the study of ventricular tachycardia and fibrillation. The purpose of this study is to evaluate more myopic discrete bipolar (BP) and nondirectional, two-dimensional current source density (CSD) based arrays for rejection of far-field potentials and precision of activation time determination. Simultaneous recordings of the CSD, MP, and multiple BP electrograms were performed on normal dog epicardium. The time of the minimum slope in MP electrograms was compared to activation times in CSD and BP derivations using: (1) peak; (2) steepest slope; (3) zero crossing of the steepest sloping segment in either direction; and (4) waveform morphology. In vivo, CSD amplitude was reduced significantly more than MP and BP amplitudes by insertion of inert media between the heart and the electrodes. The time of the steepest slope in CSD electrograms designated activation times closest to the time of the minimum slope in MP electrograms (0.9 ± 1.3 msec). We conclude that CSD provides a nondirectional electrode system that accurately defines the time of local activation and possesses better spatial specificity than MP electrode systems and BP electrode systems having the same interelectrode distances.     

The Epicardial Field Potential in Dog: Implications for Recording Site Density During Epicardial Mapping

Investigations into mechanisms and successful surgical therapy of ventricular tachycardia (VT) depend upon accurate endocardial/epicardial mapping. Deduction of local activation is based upon parameters derived from the field potentiai (FP) (monopolar recording) or its first spatial derivative (bipolar recording). Adequate electrode spacing is an assumption fundamental to the mapping process, but the electrode spacing required for accurate representation of the FP is unknown. The purpose of this work is to derive the electrode spacing necessary to accurately describe the FP on the epicardium. In 11 dogs, electrograms from vertical (V) (base to apex h) bands having 40 electrodes and horizontal (H) bands having 40 to 80 electrodes were sampled at I kHz. The spatial handwidths (BW) were computed according lo two criteria: (1) the frequency yielding 2% mean squared error (MSE) computed at the time of the greatest integrated magnitudes of the Fourier transform; and (2) the highest frequency bounding 95% power computed at each msec throughout the beat. Implied electrode spacings were defined according to the sampling theorem. The 5th percentiles of the implied electrode spacing distributions were used to define the widest interelectrode distance required to prevent spatial aliasing. H-5th percentile and V-5th percentile were, respectively; 2% MSE (3.5 mm, 2.3 mm); 95% power (3.6 mm, 2.3 mm). Thus, a typical 20-kg dog requires more than 250 recording sites for accurate epicardial mapping. Extrapolating to man, these results suggest inadequate electrode density may partially be responsible for incomplete and ambiguous reentry patterns often observed during intraoperutive mapping.     

Transesophageal Echocardiographic Findings of a Dehisced Duran Mitral Annuloplasty Ring

We describe multiplane transesophageal echocardiographic findings in a patient with severe mitral regurgitation secondary to dehiscence of a Duran ring.