Development of infundibular obstruction after percutaneous pulmonary balloon valvuloplasty.

A 14 month old boy with suprasystemic right ventricular pressure secondary to pulmonary valvular stenosis and anular size of 10 mm underwent percutaneous balloon valvuloplasty with a 12 mm balloon. Right ventricular pressure almost doubled after valvuloplasty and the electrocardiogram revealed development of severe right ventricular strain. Both findings persisted on the following day. A postvalvuloplasty right ventriculogram demonstrated a severe systolic infundibular obstruction not present before. The patient underwent surgical relief of infundibular obstruction; successful opening of the pulmonary valve by the balloon valvuloplasty was observed. It is concluded that a balloon size 20% larger than anular size can be safe in human subjects and that infundibular obstruction may appear or even worsen after balloon valvuloplasty. Such an obstruction may be related to the severity of pulmonary valvular obstruction and a hypercontractile infundibulum.

Maturational changes in left and right ventricular electromechanical intervals in the newborn lamb.

Electromechanical intervals of right and left ventricles were examined in newborn lambs (9 hours to 42 days). The electromechanical interval of the left ventricle did not change with maturation, while that of the right ventricle became progressively longer, resulting in an increasing ventricular mechanical asynchrony. We postulate that the pattern of developing mechanical asynchrony described may occur secondary to postnatal changes in ventricular morphology.

Preserving the patient referral process in the managed care environment.

Referrals are a central component of the American health care system, defining the relationship among generalists, patients, and specialists. The dynamics of the referral process as they existed in a fee-for-service medical environment will evolve under managed care, but retain the basic "Try-out" approach of the generalist and "Rule-out" approach of the specialist. A managed care, contract-based health care system alters some of the assumptions on which the referral relationship has been structured. A four-step approach to assuring quality interactions among patient, generalist, and specialist within the managed care environment is described, including: (1) engage; (2) anticipate; (3) feedback; and (4) reassess. When the referral process is structured as suggested, it can be evaluated for quality and efficacy. Armed with mutual respect and understanding, the forces that polarized specialist and generalist care in the 1980s can be redirected to enhancing patient care in the 1990s.

Evaluation of atrioventricular septal defect by magnetic resonance imaging.

Electrocardiographically gated magnetic resonance imaging (MRI) was successfully performed in 9 patients with atrioventricular (AV) septal defect: 6 had complete AV canal and 3 had partial AV canal. The defect was readily visualized in all patients on transverse scans taken at the level of the AV valve. The size and extent of the defect could be easily determined. All patients demonstrated a similar underlying morphologic pattern on MRI scans, consisting of deficiency of the primum atrial septum and inlet ventricular septum and a "common" AV valve ring with absence of the cardiac crux. The 3 patients with isolated atrial septal defect could be distinguished from the 6 with complete AV canal by the dense, fibromuscular bridging tissue, which coursed from the AV valve to the crest of the ventricular septum, obliterating the interventricular communication. Four patients had angiographically proved ventricular hypoplasia, which was also detected by MRI. AV valves and their patterns of chordal attachment were accurately imaged in 7 patients on systolic sections; accessory chordae were identified in 6 patients. MRI is a useful noninvasive imaging modality that can depict the underlying morphologic abnormalities in AV septal defect as well as important anatomic variations.

Increased systemic vascular resistance in neonates with pulmonary hypertension.

The time necessary for aortic diastolic pressure to decrease to 50 percent of an initially selected value after dissipation of the dicrotic notch (T 1/2) was determined in newborn infants with and without pulmonary hypertension. The mean T 1/2 was 671 +/- 167 msec in seven infants with clinical evidence of pulmonary hypertension and documented right to left ductus arteriosus shunting; 849 +/- 243 msec in nine infants with clinical evidence of pulmonary hypertension but no documented right to left ductus arteriosus shunting; and 457 +/- 66 msec in eight infants with hyaline membrane disease and no clinical evidence of pulmonary hypertension or a patent ductus arteriosus. The mean T 1/2 values in the former two groups were significantly different from that in the group with no pulmonary hypertension (P less than 0.01). An evaluation of factors affecting T 1/2 leads to the conclusion that the patients with pulmonary hypertension had increased systemic vascular resistance as well. This finding has important diagnostic, etiologic and therapeutic implications.

Teaching preventive cardiology in the pediatric setting.

This article presents both the rationale behind and a framework for incorporating pediatric preventive cardiology into undergraduate medical education and pediatric residency training. Such education of physicians in the practice of preventive cardiology requires provision of not only didactic information but also training and practice in clinical skills. A combination of didactic lectures, small group discussions, interactive programs utilizing video tapes and computer programs, family and patient simulation, preventive cardiology clinics, and community cardiovascular health promotion activities all help to provide the optimal framework for an effective medical student and pediatric resident training program in pediatric preventive cardiology. Since pediatricians are in the best position to practice true primary prevention of cardiovascular disease beginning in childhood, it is essential that physicians in training understand the concepts and learn the skills needed to practice this critical component of pediatric medicine.

Modification of the Smeloff mitral prosthesis.

The simplicity of the ball valve with its random seating capabilities coupled with its durability, reliability, and predictability has made it the attractive choice of many surgeons. A low incidence of embolic phenomena with the Smeloff full-orifice, double-caged, bare-strutted ball valve has made us reluctant to alter the design over 17 years. Recent evaluation of the reasons for reoperation on the Smeloff mitral valve implantation in 376 cases revealed 16 cases in which development of fibrous subvalvular pannus with signs and symptoms of mitral stenosis occurred. The mean occurrence time was 7.5 years for adults and 4.6 years for children under age 8 years. No such problem has been encountered with the valve in the aortic position. Many of these patients are maintained on aspirin and Persantine alone. Valve design was explored as a possible cause of mitral subvalvular stenosis. Alterations of the design were examined in the engineering laboratory and in dog implantations by catheterization, electrophysiologic evaluation, and echocardiography. The results were encouraging.

Conduction abnormalities detected by electrophysiologic testing following repair of ostium primum atrioventricular septal defect.

Since 1983 we have performed electrophysiologic studies in 6 patients who had previously undergone repair of an ostium primum atrioventricular septal defect. Information obtained during electrophysiologic studies was crucial in guiding appropriate pacemaker therapy in these patients. As judged from the resting electrocardiogram, sinus or junctional bradycardia was present in 3/6, atrial flutter / fibrillation in 2/6, and paced rhythm in 2 patients who had had ventricular pacemakers implanted for complete atrioventricular block. During maximal exercise testing 4 patients had reduced heart rates; 2 had sudden drops in heart rate at 1 min postexercise; 1 patient had exercise induced ventricular bigeminy; and 1 patient with atrial flutter and 2: 1-4: 1 block at rest developed 1: 1 conduction during Stage II with an effective ventricular rate of 220/min. During electrophysiologic studies, the maximum corrected sinus node recovery time was abnormal in five of the six, ranging from 410 to 5630 msec. There was no spontaneous atrial rhythm in the other patient. Complete atrioventricular block was present in 2 patients while the atrioventricular Wenckebach phenomenon occurred abnormally at atrial pacing cycle lengths greater than 450 msec in 2 others. Supraventricular tachycardia or atrial flutter/fibrillation, was either spontaneous or induced in 2/6 patients, while ventricular tachycardia was induced in 1/3 patients who underwent programmed ventricular stimulation. Electrophysiologic studies were important in unmasking severe sinus node disease in 3 patients and atrioventricular node disease in 2. We therefore recommend that electrophysiologic studies be strongly considered as part of the evaluation of conduction abnormalities following repair of ostium primum atrioventricular septal defect.

Heart murmurs in infants and children.

A system is presented for evaluation of heart murmurs in infants and children. The system places emphasis on identification of functional murmurs, which the physician encounters so frequently in daily practice. A three-part approach is presented which includes: (1) evaluation of cardiovascular status, (2) assessment of the heart murmur, and (3) decision regarding the need for further evaluation. This approach relieves the physician of the necessity to remember the multiple details of the many congenital cardiac lesions, and requires only the knowledge of a few easily remembered details about functional murmurs. The system enables the physician to confidently distinguish organic and functional murmurs and to decide which children need further evaluation and referral to the pediatric cardiologist.

Occult arrhythmias as the etiology of unexplained syncope in children with structurally normal hearts.

We evaluated six children for syncope of unknown etiology between March, 1983, and March, 1984. All had undergone previous neurologic evaluation which was normal. Cardiac examination, chest roentgenograms, and two-dimensional echocardiograms were also normal in all of the patients. Abnormal noninvasive findings in five patients included Mobitz type II atrioventricular (AV) block (one patient), sinus bradycardia (three patients), and supraventricular tachycardia (one patient). Four patients had one or more abnormal findings at invasive electrophysiologic study including evidence of sinus node dysfunction (three patients), AV node dysfunction (three patients), and distal His-Purkinje system disease (two patients). All children had a normal right heart hemodynamic catheterization. We conclude that arrhythmias are an important cause of syncope in some children with an otherwise normal heart when neurologic causes have been excluded.

Ventricular epicardial activation sequence in the lamb.

The ventricular epicardial activation sequence (VEAS) in 15 anesthetized lambs (near term fetus to 3.5 months of age) was determined using 40 simultaneously recorded bipolar electrograms for each animal. Isochrone maps were drawn by hand using relative activation times determined from the maximum first derivative of multiplexed signals recorded and analyzed by computer from single cardiac cycles. VEAS was similar for all ages studied. Earliest left ventricular (LV) activity appeared on the caudal dorsal and/or ventral free wall. Initial right ventricular (RV) activation appeared on the ventral anterior and/or lateral surface either simultaneously with or slightly later (2.5-3.5 msec) than initial LV activation. Excitation then proceeded circumferentially and in an apicobasilar direction and terminated on the right ventricular outflow tract.(RVO). All LV and RV epicardium except RVO activated within 7.5-12.5 msec. RVO required more than 1n.5 msec to activate in 12 of 15 animals. Total duration of RVO activation never exceeded 22.5 msec in any animal. Neither the duration nor the pattern of activation of LV or RV epicardium, including RVO, changed in a consistent fashion with age. These findings are similar to the known VEAS for adult ruminants. The data indicate that the VEAS assumes the adult pattern as of late gestation and suggest that changing right and left ventricular electromechanical events do not contribute to and probably are not affected by the process of ventricular epicardial activation. Speculation Although maturational changes in right and left ventricular electromechanical events do not appear to be related to the sequence of ventricular epicardial activation, such changes may be related to the distrubution of corresponding epicardial and intramural isopotentials.

Maturational Changes in Myocardial Contractile State of Newborn Lambs.

There have been no investigations of chronologic changes in postnatal contractile state of both left and right ventricles of the newborn. Thus, we determined isovolumetric indices of contractility in 32 acutely instrumented newborn lambs (1 day to 12 wk; three exteriorized near term fetuses, and four adult sheep. These studies demonstrated a marked increase in inotropic properties of both ventricles which was especially pronounced during the first 3 days of extrauterine life (group 1, left ventricle Vmax 3.2 +/- 0.27 and VCE10 3.2 +/- 0.28 Ml (muscle lengths)/sec; right ventricle Vmax 2.1 +/- 0.2 and VCE10 2.2 +/- 0.13 ML/sec); and was associated with elevated cardiac output (428 +/- 52 cc/kg/min), largely resulting from an elevated stroke volume (2.1 +/- 0.31 cc/kg). During subsequent postnatal maturation, contractility indices of both ventricles gradually declined to values intermediate between newborn and adult ((group IV, 22 to 84 days) - left ventricle Vmax 1.78 +/- 0.13 and VCE10 1.79 +/- 0.15 ML/sec; right ventricle Vmax 1.48 +/- 0.07 and VCE10 1.31 +/- 0.3 ML/sec); associated with a corresponding decline in cardiac output (group IV, 136 +/- 38 cc/kg/min), related in large measure to a decline in stroke volume (0.76 +/- 0.13) cc/kg). Simulation of birth in exteriorized fetuses was associated with a sudden increase in contractile indices for both left (Vmax 2.1 +/- .2 leads to 3.0 +/- .3 and VCE10 2.1 +/- 0.2 leads to 3.1 +/- 0.3 ML/sec) and right (Vmax 2.0 +/- 0.2 leads to 2.5 +/- 0.2 and VCE10 1.9 +/- 0.1 leads to 2.5 +/- ML/sec) ventricles. We conclude that there is a postnatal elevation of ventricular contractile state which contributes to successful postnatal adaptation of the newborn cardiovascular system.

Maturational changes in myocardial pump performance in newborn lambs.

We examined the left ventricular stroke volume response to fluid loading in 24 acutely instrumented newborn lambs and the right ventricular response in 12 lambs. Newborn lambs (group 1, ages 2 to 4 days) demonstrated a limited response to acute volume loading for both left and right ventricles. With maturation, the left ventricle exhibited a progressively greater ability to respond to acute volume loading, with greater peak stroke volumes achieved at higher end-diastolic pressures. The response of the right ventricle remained limited at all ages examined, with peak stroke volume achieved at lower end-diastolic pressures. We conclude that postnatal maturation of the left ventricle results in a progressively greater stroke volume response in older lambs, while the response of the right ventricle remains limited.

Persistent transitional circulation. Roentgenographic findings in thirteen infants.

Chest roentgenograms in 13 infants and angiocardiograms in 11 infants with persistent transitional circulation (PCT) syndrome were reviewed. Chest radiographs typically revealed congestive heart failure with pulmonary venous congestion, cardiomegaly, hepatomegaly, and pleural effusions. Angiocardiography demonstrated a right-to-left shunt through the ductus arteriosus, ventricular dilatation, poor myocardial function, and ventricular emptying. Cardiopulmonary abnormalities resolved over a period of 2-6 days in survivors. PTC syndrome as seen at the authors' institution has been an important and relatively common cause of congestive heart failure and cyanosis in the newborn. The incidence of congestive failure was higher than in other reported series.