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Ouabain-induced tachyarrhythmias in cats can be abolished by bolus injection of NaHCO3 solution. This effect is consistent, rapid and of short duration. The antiarrhythmic effect appears to be due to high sodium concentration of this solution, as hypertonic NaCl solution with equal concentration of sodium exerts the same effect. Alkalinity and hyper-osmolality cannot account for the antiarrhythmic effect of NaHCO3 as respiratory alkalosis and mannitol solution with equal osmolality did not relieve the arrhythmias. Overdrive suppression is not responsible for this effect as the heart rate slows down during normalization of the cardiac rhythm. It is postulated that high Na+ concentration abolished ouabain-induced arrhythmias by competition with calcium ion in the myocardial cell sarcotubular system thus replacing it. This hypothesis is supported by the known effect of other agents such as sodium-EDTA and magnesium chloride, in digitalis-induced arrhythmias, which exert their antiarrhythmic properties by removal or displacement of calcium in the myocardial cells.

A comparative morphometric study was performed on the aortomitral valve apparatus of the embryonic and adult chicken hearts. It was found that the thickness of the aortic and mitral valve cusps diminishes dramatically as the embryo matures, however the relative length of the aortic valve, mitral valve and subaortic conus remains constant. A comparison of the aortomitral valve apparatus in chicken and man revealed that the subaortic conus is not completely resorbed in the fowl, whereas this process is well documented in the mammalian hearts. The implications of this observation on "the differential conal growth hypothesis" of transposition of the great arteries are discussed.

Previous reports from this laboratory have shown that penicillamine effectively reduces serum digoxin levels and is a clinically useful drug in correcting digoxin intoxication. To elucidate further the antidigitalis effects of penicillamine a prospective study was undertaken in 10 children aged 4--14 years with congestive heart failure. Plasma and intracellular erythrocyte concentrations of sodium, potassium, calcium as well as Na+/K+ and Na+/Ca++ ratios were measured before digitalization, 6 days after full digitalization while the patients were on maintenance doses of digoxin (0.02 mg/Kg/day, po, maximum 0.25 mg/day) and 6 hours after 1 Gm of oral penicillamine. After digitalization RBC Na+, Ca++, Na+/K+, and Na+/Ca++ increased, whereas RBC K+ levels decreased significantly. Administration of penicillamline not only reduced serum digoxin levels, but it also caused significant alterations in RBC electrolyte concentrations, toward pre-digoxin values. All values were significantly changed after penicillamine. Plasma and RBC magnesium levels were not altered significantly, neither after digitalization nor after penicillamine. It is concluded that in addition to RBC Na+ and K+ levels, intra-erythrocyte levels of calcium are sensitive indicators of digoxin effect; and that penicillamine reverses digoxin-induced RBC electrolyte alterations towards pre-digitalization values.

The electrophysiologic effects of verapamil, a slow channel blocker, were investigated during diagnostic cardiac catheterization in 24 children premedicated with lytic cocktail. The ages ranged from 50 days to 12 years. Twenty had congenital and 4 had rheumatic heart disease. Surface EKG, high intra-atrial and His bundle electrograms were obtained in all before and 5 min after a single dose of verapamil (0.15 mg/Kg, max 5 mg iv). In 14 cases complete electropysiologic studies were performed using the atrial pacing and extrastimulus technique. Due to variability of the resting heart rates and the effect of cycle length on refractory periods each paced with identical S1-S1 interval before and after verapamil, thus allowing each case to serve as his own control. Verapamil prolonged the corrected AH interval in all (mean +/- SD; from 116 +/- 37 to 152 +/- 41 msec, p less than 0.01) and shortened the HV interval in 15/24 (mean +/- SD: from 55 +/- 13 to 47 +/- 9.9 msec, p less than 0.05). The effective and functional refractory periods of the total conduction system, the AV node (ERPAVN) and atrium (ERPA) increased significantly in 10/14. The most profound effect was on ERPAVN and ERPA (25.54 +/- 29 and 19.27 +/- 21.81 percent mean percent increase +/- SD respectively, p less than 0.01 and p less than 0.02). Our findings show that verapamil prolongs the effective and functional refractory periods of the cardiac conduction system with maximal effects on the AV node, thus suggesting the mechanism of its effectiveness in the treatment of reentrant supraventricular arrhythmias.

Disopyramide has been successfully used to treat a variety of supraventricular and ventricular arrhythmias. The electrophysiologic effects of this drug were studied following diagnostic cardiac catheterization in 14 children aged 7 months to 14 years, suffering from congential heart disease. Surface EKG, intra-atrial, and His bundle electrogram as well as right atrial pacing with the use of extrastimulus technique were obtained before and after a single intravenous dose of disopyramide (2 mg/Kg, max 50 mg). The drug significantly prolonged the HV interval, effective and functional refractory periods of the atrium and the AV node. The most consistent change was the prolongation of the atrial refractory periods. The electrophysiologic effects of this drug on the conduction system have been variable and this variability has been attributed to the degree of vagal tone. The findings in this age group are similar to adults with simultaneous cholinergic blockade. This might be due to the direct depressant effects of disopyramide on the atrial and AV nodal tissue, and point to the potential usefulness of this drug in the pediatric age group.

We previously reported that pulmonary artery pressures can be assessed in children with chronic rheumatic mitral valve disease by measuring right maximum spatial vector from Frank vectorcardiogram. To simplify the calculation, pulmonary artery systolic pressure was correlated with maximum negative deflection on Frank scalar X-lead (SX), maximum negative deflection on scalar Z lead (SZ), sum total of SX and SZ (SX+SZ) and combined SX and SZ. The patient material consisted of 30 children with chronic rheumatic mitral valve disease, aged 8-14 1/2 years. Eleven were male and 19 were female. Sixteen had mitral stenosis, 8 had mitral regurgitation, and 6 had combined mitral regurgitation and stenosis, documented by cardiac catheterization and angiocardiographic study. The results showed a significant correlation between pulmonary artery systolic pressure and SX (r=0.782). As calculation of SX is considerably easier and less time consuming than that of right maximum spatial vector, this simplified method is preferable to right maximum spatial vector for prediction of the pulmonary artery systolic pressure of children with pulmonary hypertension due to chronic rheumatic mitral valve disease.

Vitamin E (E) and selenium (Se) are important antioxidant nutrients, preventing membrane damage by lipid hydroperoxides. In a previous study on E + Se deficient rats it was shown that plasma levels of lipoproteins increase dramatically. In continuation of this study a quantitative microscopic study was undertaken to determine the behavior of myocardial interstitial tissue space (ITS) in E + Se deficient rats as compared to control rats. Four rats fed on normal laboratory chow and 8 rats fed on basal diet supplemented with adequate E + Se served as control. Eight rats were fed on E + Se deficient diet. The animals were sacrificed after 13 to 20 weeks. Qualitative microscopic study showed patchy areas of hemorrhage, edema, infiltration of macrophages and myocardial damage consisting of pyknosis and coagulation necrosis in the deficient rats. Quantitative microscopic study of the apparently normal areas of myocardium of deficient rats showed a shrinkage of ITS (21.0 +/- 1.29% vs 16.51 +/- 4.62%, alpha = 0.01), whereas the ITS of normal laboratory chow and E + Se supplemented groups were similar. The myocardial fiber diameter was unchanged. Using Starling's hypothesis regarding fluid movement across capillary walls, several mechanisms could be advanced to explain this apparently paradoxical phenomenon. We contend that the interstitial fluid of normal areas of the myocardium is either absorbed by the adjacent damaged areas, or before extravasation of the intravascular proteins and swelling of ITS, the interstitial fluid is first absorbed by the intravascular compartment, due to capillary membrane damage.

The effects of intravenous administration of mexiletine on the refractory periods of the atrium and atrioventricular (AV) node were studied using His bundle recordings and the extrastimulus technique with atrial pacing. The drug was administered to 10 children with heart disease in an intravenous bolus dose of 3 mg/Kg, injected over a 5-min period, followed by an infusion of 1 mg/Kg/hr of mexiletine, achieving a mean therapeutic plasma concentration of 0.762 +/- 0.270 microgram/ml. The AH and HV intervals, the resting sinus cycle length, and the functional and effective refractory periods of the atrium and AV node were measured before and 5 min after initiation of the mexiletine infusion. The sinus cycle length was reduced significantly. However, neither the refractory periods nor the AH and HV intervals changed in a significant manner. Except for the heart rate, these results are similar to those reported in adults without conduction disturbances. In adults, mexiletine did not affect the sinus cycle length. However, in children, it consistently increased the heart rate. The lack of side effects in children is in contrast to adults, who usually suffer from gastrointestinal and neurologic symptoms upon receiving comparable doses parenterally.

A heart specimen is presented which showed a rare combination of atrioventricular valve atresia with single ventricle, truncus arteriosus communis with an anteriorly placed trunk, ie transposition. Because of the problems involved in the classification of this heart, the types of single ventricle are revised with particular attention to the rare cases of atrioventricular valve atresia and single ventricle reported in the literature. Also the rare type of truncus arteriosus communis with truncoatrioventricular valve discontinuity is excluded from the so-called transposition complexes, and properly classified as a form of truncus. The literal meaning of transposition is stressed and it is urged to approach congenital heart defects in a purely anatomic sense with definition of each segment as accurately as possible. Thus the present confusion in terminology and further plethora of new terms are avoided.

A 9-year-old boy is reported who had tetralogy of Fallot, rudimentary pulmonic valve, and supravalvar pulmonic stenosis. The patient lacked almost all of the clinical findings commonly encountered in this syndrome. Thus he never had signs of a large left-to-right shunt, or congestive heart failure. He had no murmur of pulmonic regurgitation and his pulmonary artery was not large on chest roentgenogram. Angiocardiography revealed moderate main pulmonary arterial dilation. The lack of the usual manifestations of tetralogy of Fallot with absent pulmonic valve was due to supravalvar pulmonic stenosis, acting as a natural pulmonary artery band. A quantitative angiocardiographic study was undertaken in order to find a clue for the diagnosis of these atypical cases. The ratio of the transverse diameters of the main pulmonary artery and the aortic root as measured on lateral angiocardiograms in 31 children with uncomplicated tetralogy of Fallot was 0.70 +/- 0.22, whereas this ratio was 1.70 in this particular patient (p less than 0.001). It is concluded that a quantitative evaluation of the ratio of the transverse diameter of the main pulmonary artery to the aortic root on lateral angiocardiogram allows differentiation of tetralogy of Fallot with absent pulmonic valve associated with supravalvular pulmonic stenosis from uncomplicated forms of tetralogy of Fallot.

The effects of verapamil, a slow channel blocker and a potent antiarrhythmic drug, on retrograde V-A conduction were investigated following diagnostic cardiac catheterization in 12 children premedicated with lytic cocktail. Surface EKG, intra-atrial and His bundle electrograms, as well as right ventricular pacing with use of extra stimulus technique were obtained before and after a single intravenous dose of verapamil (0.15 mg/Kg, max 5 mg). Verapamil prolonged the AH interval in 9/12 and abolished or prolonged the retrograde V-A conduction whenever present (abolition in 5/12 and prolongation in 1/12). The duration of retrograde V-A conduction exceeded the antegrade conduction time in all. It is concluded that verapamil abolishes retrograde V-A conduction whenever present and this phenomenon may further explain the antiarrhythmic effects of the drug on retrograde conduction dependent (reentrant) arrhythmias.

The importance of metals in normal and pathologic cardiovascular function has been recognized. Significant derangements in myocardial Ca2+, Mg2+, and Cu2+ have been reported in ischemic heart injury. We studied 3 groups of hearts: 1) fifteen specimens obtained from patients who had no heart disease, 2) nine specimens from patients who had expired from cyanotic congenital heart disease, and 3) ten specimens from patients who had expired from acute rheumatic heart disease with carditis and severe heart failure. None of the patients had undergone cardiac surgery. Left ventricular lateral wall Mg2+, Ca2+, Cu2+, and Zn2+ contents were measured by atomic absorption spectrometry. The results showed a significant decrease in myocardial Mg2- (Group I 177.06 +/- 32.71; Group II 155.66 +/- 14.79; Group III 149.00 +/- 13.29, p less than 0.05 and p less than 0.01, respectively), and Cu2+ contents (Group I 3.22 +/- 0.37; Group II 2.94 +/- 0.22; Group III 2.56 +/- 0.32, p less than 0.02 and p less than 0.001, respectively), and a rise in myocardial Ca2+ content (Group I 36.06 +/- 10.72; Group II 43.22 +/- 7.01; Group III 46.30 +/- 4.85, p = not significant, and p less than 0.01, respectively). The myocardial Zn2+ content did not change significantly (Group I 26.53 +/- 3.99; Group II 26.00 +/- 4.15; Group III 26.40 +/- 3.53). The myocardial Mg2+/Ca2+ ratio was reduced markedly in both groups (Group I 5.328 +/- 1.879; Group II 3.685 +/- 0.735; Group III 3.135 +/- 0.291, p less than 0.001 for both Groups II and III vs Group I). The latter results correlated closely with the myocardial Mg2+/Ca2+ ratios reported in experimental models in peri-infarction zones. Thus, the myocardium of patients who had expired from cyanotic congenital heart disease and acute rheumatic carditis is jeopardized by ischemia, with metal contents similar to the border areas in myocardial infarction.

Atrioventricular conduction characteristics were examined by atrial extrastimulus technique in 45 children aged 50 days to 14 years following diagnostic cardiac catheterization. None of the patients had a history of supraventricular tachycardia and none had evidence of pre-excitation on routine electrocardiogram. By plotting the A2H2 and H1H2 intervals against corresponding S1S2 intervals 2 types of conduction curve were obtained. Eight of the 45 children (17.7%) showed discontinuous conduction curves, characteristic of dual atrioventricular nodal pathways, whereas 37 patients had continuous curves. Of the 8 patients with discontinuous curves 3 showed unsustained echo beats following extrastimuli, after the effective refractory period of the fast pathway was reached. This study showed that, as in adults, the atrioventricular node was frequently functionally dissociated in children.

A 10-month-old boy is presented who had isolated unilateral absence of the right pulmonary artery. He suffered from hemoptysis and severe congestive heart failure. The patient underwent prosthetic anastomosis of the right to the main pulmonary artery. Although the hemodynamic response was favorable, his oxygenation did not improve due to diffuse pulmonary arteriovenous fistulae of the affected lung. The patient succumbed 3 months after operation due to massive uncontrollable hemoptysis from the right lung. Isolated unilateral absence of the pulmonary artery is a rare lesion. In our review of the world literature as of November 1976, 47 cases (including this report) of the unilateral absence of the pulmonary artery have been reported. Of these 25.5% had pulmonary hypertension and only 4 cases underwent successful repair of the lesion. Though repair of this defect can be carried out, the result may not be always gratifying. Our experience with this case has led us to consider a lung biopsy before proceeding to the surgical repair of the lesion. If the affected lung shows arteriovenous abnormalities the operation should not be recommended.

Hypertrophic cardiomyopathy (HCM) is most probably a genetically transmitted disease with different clinical and hemodynamic features. In hypertrophic obstructive cardiomyopathy (HOCM) the obstruction is predominantly in the left ventricular outflow tract (IHSS). In a minority of cases the obstruction is strictly located in midventricle (midventricular obstruction, MO). Hypertrophic nonobstructive cardiomyopathy (HNCM) includes asymmetric septal hypertrophy (ASH) and apical hypertrophy (AH). Right ventricular hypertrophic obstruction (RVHO) is an uncommon type of HCM and is almost always combined with other types of left ventricular HCM. We describe in the present report 1 case of RVHO with IHSS, 2 cases with MO and, to our knowledge, the first case with AH.

The effects of intravenous lidocaine on the refractory periods of the atrium, AV node and right ventricular myocardium were studied using His bundle recordings and the extrastimulus technique with and without atrial and ventricular pacing. The drug was administered in an intravenous bolus dose of 1 mg/Kg followed by an infusion of 100 micrograms/Kg/min. The AH, HV intervals and resting sinus cycle length as well as functional and effective refractory periods of atrium, AV node and right ventricle were measured before and 5 min afrer bolus injection of lidocaine. Neither of the refractory periods nor AH and HV intervals changed significantly following administration of lidocaine. The result of this first study in children is in agreement with previous reports of the effects of lidocaine on the cardiac conduction system in adults.