Sarah D. Blumenschein

Successful Surgical Interruption of the Bundle of Kent in a Patient with Wolff-Parkinson-White Syndrome

Recurrent supraventricular tachycardia is a frequent complication in patients with the Wolff-Parkinson-White (WPW) syndrome. Our patient was unusual in that the arrhythmia was the predominant rhythm, and it was felt that the sustained tachycardia was responsible for signs and symptoms of congestive heart failure. The arrhythmia could not be controlled adequately with digitalis, quinidine, diphenylhydantoin, or propranolol. Atrial or ventricular pacing also failed to prevent recurrent episodes of tachycardia.Physiological and pharmacological studies suggested that an anomalous pathway was responsible for the WPW abnormality and participated in a re-entrant circuit which sustained the episodes of tachycardia. Isopotential body surface mapping suggested anomalous ventricular excitation at the lateral aspect of the right atrioventricular groove. Epicardial mapping at the time of surgery was used to localize the earliest area of anomalous ventricular activation, and surgical transection of the atrioventricular junction at that point abolished the electrocardiographic features of WPW and the recurrent tachycardia. Five months after surgery neither the ECG features of WPW nor the tachycardia has recurred. The signs and symptoms of congestive heart failure have subsided, and the patient has returned to work.

Genesis of Body Surface Potentials in Varying Types of Right Ventricular Hypertrophy

Isopotential body surface maps and the sequence of epicardial excitation were studied in children with three types of pure right ventricular hypertrophy; that is, secundum atrial defects, valvular pulmonic stenosis, and tetralogy of Fallot. Patients with similar types of hypertrophy demonstrated internal consistency as to the anatomy, sequence of epicardial excitation of the right ventricular free wall, and body surface potential distribution; however, these phenomena varied between the three groups for each type of hypertrophy. These studies indicate that diagnostic information is available on the body surface to distinguish: (1) right ventricular hypertrophy due primarily to dilatation (secundum atrial septal defects), (2) right ventricular hypertrophy with symmetrical increase in thickness throughout the right ventricle (valvular pulmonic stenosis with moderate to severe right ventricular hypertrophy), and (3) right ventricular hypertrophy proximal to infundibular narrowing (tetralogy of Fallot) from one another. The body surface events could be accounted for in part by the events measured at the epicardial surface.

Influence of respiration on recording cardiac potentials. Isopotential surface-mapping and vectorcardiographic studies*

Abstract Isopotential surface-mapping studies in normal children indicated that inspiration produces an inferior shift of potential maxima and minima on the body surface with a concomitant decrease in their absolute potential values. There was a terminal maximum under the right clavicle with inspiration which was absent during expiration. Review of the body surface potential distribution provided a clearer picture of changing events of respiration than could be acquired from analysis of data acquired from a few selected points, as is done in vector-cardiography. Respiratory changes were more prominent in abnormal than in normal vector-cardiograms. It is suggested that when quantitative vectorcardiographic analysis is used for comparison of patient groups, it would be optimal to compare beats recorded during resting expiration.

Genotype-phenotype relationships in patients with type I hyperlipoproteinemia

CONTEXT Type I hyperlipoproteinemia (T1HLP) is a rare, autosomal recessive disorder characterized by extreme hypertriglyceridemia that fails to respond to lipid-lowering agents, predisposing to frequent attacks of acute pancreatitis. Mutations in lipoprotein lipase (LPL), apolipoprotein CII (APOC2), lipase maturation factor 1 (LMF1), glycosyl-phosphatidylinositol anchored high-density lipoprotein-binding protein 1 (GPIHBP1), and apolipoprotein AV (APOA5) cause T1HLP, but we lack data on phenotypic variations among the different genetic subtypes. OBJECTIVE To study genotype-phenotype relationships among subtypes of T1HLP patients. DESIGN/INTERVENTION Genetic screening for mutations in LPL, APOC2, GPIHBP1, LMF1, and APOA5. SETTING Tertiary referral center. PATIENTS Ten patients (7 female, 3 male) with chylomicronemia, serum triglyceride levels about 2000 mg/dL, and no secondary causes of hypertriglyceridemia. MAIN OUTCOME MEASURES Genotyping and phenotypic features. RESULTS Four patients harbored homozygous or compound heterozygous mutations in LPL, 3 had homozygous mutations in GPIHBP1, and 1 had a heterozygous APOA5 mutation. We failed to fully identify the genetic etiology in 2 cases: 1 had a heterozygous LPL mutation only and another did not have any mutations. We identified 2 interesting phenotypic features: the patient with heterozygous APOA5 mutation normalized triglyceride levels with weight loss and fish oil therapy, and all 7 female patients were anemic. CONCLUSIONS Our data suggest the possibility of novel loci for T1HLP. We observed that heterozygous APOA5 mutation can cause T1HLP but such patients may unexpectedly respond to therapy, and females with T1HLP suffer from anemia. Further studies of larger cohorts may elucidate more phenotype-genotypes relationships among T1HLP subtypes.

Clinical Implications of Isopotential Surface Maps

Abstract Body surface isopotential surface maps are related to electrical events within the heart. The conventional electrocardiogram and vectorcardiogram were compared with the total body potentia...

Evaluation of Coronary Artery Fistula by Color‐Flow Doppler Echocardiography

An asymptomatic newborn infant with a left coronary artery to right ventricular apex fistula was evaluated using color‐flow Doppler techniques. Color flow mapping during diastole showed a prominent turbulent flow signal that could be traced from the proximal left coronary artery, along the interventricular septum, to the right ventricular apex. Color flow Doppler is an important complement to two‐dimensional imaging for the identification and location of coronary artery fistulas.

Cardiac potentials in pulmonary disease. Overdistension of the lung versus cor pulmonale (right ventricular hypertrophy).

Abstract These studies demonstrated the distribution of cardiac potentials on the body surface in children with clinical evidence of overdistension of the lungs without right ventricular hypertrophy. The effect of the overdistended lung was shown to alter body surface events during ventricular activation by causing an inferior shift of potential maxima and minima during the middle third of the QRS. Roentgenographic studies demonstrated an associated inferior shift of the heart in relation to the anterior chest surface. Further shown was the associated diminished values of potentials over the left lateral chest during this interval in the patients with cystic fibrosis, as compared to normal children. The results of surface-mapping and x-ray studies indicated that leads placed in the fourth interspace monitor different body surface events during the middle of QRS in the cystic fibrosis children as compared to normal children due, in large part, to the inferior shift of potential maxima and minima. In the presence of cor pulmonale with marked right ventricular hypertrophy the potential distribution over the body was quite different in normal subjects and in those with cystic fibrosis. Right ventricular hypertrophy produced a migration of the anterior maximum in a rightward direction during the latter part of the QRS. Its terminal position was located beneath the right clavicle. These events differed from those in normal subjects and those with cystic fibrosis who showed a leftward migration of the maximum with a terminal distribution characterized by anterior minimum and posterior maximum.

Quantitative Frank vectorcardiograms of normal children and a comparison to those of patients with atrial defects

Abstract Frank VCGs were subjected to detailed quantitative analysis for a large group of normal children, and a tabulation of normal values is presented. The values are based on examination of the vectors in the form of x, y, and z components. For children with secundum atrial septal defects, statistically significant differences from normal children were found throughout most of the QRS. From these measurements it was determined that easily measurable scalar lead variables Sx, Ry, and Sz were highly discriminating between the two categories, and an arbitrary method was defined for placement of an individual patients vector into either the ASD or the normal category. The results indicate that application of such statistical methods, which do not require a computer, may be useful in differentiating diagnostic categories on an individual patient basis.

Effect of lifibrol on the metabolism of low density lipoproteins and cholesterol

Lifibrol is a powerful cholesterol‐lowering drug of unknown mechanism of action. This investigation was carried out to determine whether the major action of lifibrol is to enhance clearance of low density lipoproteins (LDL) through the LDL‐receptor pathway, and if so, whether the drug exerts its action by altering the excretion of bile acids (acidic steroids), the absorption of cholesterol, or the synthesis of cholesterol. In a first study, in two patients with complete absence of LDL receptors, lifibrol therapy had essentially no effect on plasma LDL concentrations; in two others who had a marked reduction in LDL‐receptor activity, response to the drug was attenuated. These findings suggest that lifibrol requires an intact LDL‐receptor pathway to exert its action. In a second study, in patients with primary moderate hypercholesterolemia, isotope kinetic studies showed that lifibrol enhanced the fractional catabolic rate of LDL‐apolipoprotein B (apo B), but had no effect on transport rates of LDL; these observations likewise support the probability that lifibrol acts mainly to increase the activity of the LDL‐receptor pathway. However, in a third study in hypercholesterolemic patients, lifibrol therapy failed to increase acidic steroid excretion, inhibit cholesterol absorption, or reduce net cholesterol balance. Furthermore, lifibrol treatment did not significantly reduce urinary excretion of mevalonic acid. In contrast, in a parallel study, simvastatin therapy, which is known to inhibit cholesterol synthesis, gave the expected decrease in net cholesterol balance and reduction in urinary excretion of mevalonic acid. Thus, lifibrol, like statins, appears to increase the activity of LDL receptors; but in contrast to findings with statins, it was not possible to detect a significant decreased synthesis of cholesterol, either from balance studies or from urinary excretion of mevalonic acid. This finding raises the possibility that lifibrol activates the LDL‐receptor pathway through a different mechanisms which remains to be determined.