Allan J. Hordof

Blade balloon atrial septostomy in patients with severe primary pulmonary hypertension.

BACKGROUND Patients with severe primary pulmonary hypertension have a poor prognosis, but those with a patent foramen ovale may survive longer. A few reports of clinical improvement after blade balloon atrial septostomy in patients with severe pulmonary vascular disease have appeared. The purpose of this study was to systematically evaluate the effects of blade balloon atrial septostomy on clinical signs and symptoms, hemodynamics, and survival in patients with severe primary pulmonary hypertension. METHODS AND RESULTS Blade balloon atrial septostomy was performed on 15 children and young adults with severe primary pulmonary hypertension. Despite maximal medical therapy, prior to septostomy all patients had recurrent syncope and 8 had severe right heart failure. Thirteen patients survived the procedure. After blade balloon atrial septostomy, no patient experienced further syncope, and signs and symptoms of right heart failure improved in all New York Heart Association Class IV patients. Within 24 hours after the procedure and at follow-up catheterization 7 to 27 months after septostomy, there was a significant increase in cardiac index, resulting in an increase in systemic oxygen transport. There was improved long-term survival in the 13 patients who survived blade balloon atrial septostomy compared with similar groups of primary pulmonary hypertension patients who received standard therapy (P < .05). CONCLUSIONS Blade balloon atrial septostomy resulted in clinical and hemodynamic improvement and improved survival in selected patients with severe primary pulmonary hypertension.

Propranolol administration during pregnancy: Effects on the fetus

The case of an infant born to a mother receiving continuous propranolol therapy throughout pregnancy isreported. Perinatal problems included: a small placenta, intrauterine growth retardation, fetal depression at birth, and postnatal hypoglycemia and bradycardia. These responses appeared to be the direct result of the maternal use of propranolol. Hence, infants born to mothers on continuous therapy with this agent should be considered at risk for developing these complications.

Electrophysiologic properties and response to pharmacologic agents of fibers from diseased human atria.

SUMMARY We used standard nicroketrode to record action potentials of human right trial fibers obtained during cardiac surgery, and correlated these potential with dinical and preoperative ECG data. Human atrial fibers were classified as follows: Group A (ten patients) had a maximum diastolic potential (MDP) of −71.4 ± 5.1 mV (mea ± SD), and actin potentials that were primarily fast pe These atria were normal or sdghty dilated. In group B (12 patients) MDP was −50.3 ± 5.7 mV; action potentials were slow responses and the atria were moderately to markedly dilated. Atrial arrhythmias occued in four grop B and no group A patients. The ECG revealed a signfcant (P < 0.005) in P wave duration: group A, 89 ± 3.0 nec; B, 111 ± 6.0 msec. Verapamil, 0.1 mg/L, markedly depre roup B action potentials. Verapamil, 0.1–1.0 mg/L, de only the action potential plateau of group -A. Procanamlde 1–100 mg/L had equivalent effects on fibers of both groups A and B, effects whc were small at dosages of less than 40 mg/L. Procalnamide did ot depress slow response automaticity, but verapamil (0.1–1 mg/L) did.

Ultrastructure and transmembrane potentials of cardiac muscle in the human anterior mitral valve leaflet.

We studied the ultrastructure and electrophysiology of an anterior mitral valve leaflet obtained from the heart of a recipient of a cardiac transplant. The anterior leaflet of this human mitral valve contained atrial muscle in direct continuity with the left atrial myocardium. The muscle fibers were 3-6, in diameter and contained atrial-specific granules. They were arranged in longitudinal bands of two or three muscle cells with intercalated discs at the cellular poles. These groups of cells were separated from one another by abundant loose connective tissue. The muscle fibers had maximum diastolic potentials of -61 ± 8 mV and action potentials with slow upstrokes (Vmax <15 V/sec) and low amplitudes (66 ± 6 mV) occurred during electrical stimulation of the valve. In the absence of electrical stimulation, valve muscle had phase 4 depolarization and initiated automatic impulses at a slow rate. The rate of impulse initiation was increased by epinephrine. During electrical stimulation, epinephrine also caused the appearance of delayed afterdepolarizations. Triggered sustained rhythmic activity could be elicited. Delayed afterdepolarizations and triggered activity were abolished by acetylcholine and verapamil. Our results indicate that cardiac muscle in the human mitral valve can initiate impulses and might be a site of origin of arrhythmias in the human heart.

Spontaneous complete closure of a congenital coronary artery fistula

The first documentation is reported of spontaneous closure of a coronary artery to right ventricle fistula that was demonstrated initially in a 14 month old boy. Over a 4 year period after diagnosis, the characteristic continuous murmur gradually disappeared. When the patient was 5 1/2 years of age, selective coronary arteriography showed normal coronary vessels and circulation. Six other cases of coronary fistula observed during the past 10 years are also reviewed. This study supports the rationale for clinical follow-up rather than obligatory surgical intervention in asymptomatic patients with a small shunt who have no evidence of myocardial dysfunction.

The cellular electrophysiologic effects of digitalis on human atrial fibers.

We used microelectrode techniques to study the indirect and direct actions of ouabain on human atrial fibers (HAF) obtained from patients with congenital heart disease undergoing open heart surgery. At 15 min of superfusion ouabain, 2 × 10-7M, induced an increase in maximum diastolic potential (MDP), action potential (AP) amplitude and upstroke velocity of phase 0 depolarization (Vmax) and a decrease in AP duration. Spontaneously beating HAF showed a decrease in automaticity. Acetylcholine (3 × 10-6M) induced identical effects on AP characteristics and automaticity. Prior treatment with atropine (1 × 10-6M) blocked these effects of ouabain and acetylcholine. Superfusion with ouabain (2 × 10-7M) for 30 to 90 min resulted in decreased MDP, AP amplitude and Vma., and a further decrease in AP duration. Phase 4 depolarization and spontaneous rate increased and delayed afterdepolarization and tachyarrhythmia occurred. The ACh-like effects of digitalis decrease automaticity and increase MDP of HAF; the direct effects decrease MDP, increase automaticity, and induce tachyarrhythmia occurred. The ACh-like effects of digitalis decrease automaticity and increase MDP of HAF; the direct effects decrease MDP, increase automaticity, and induce tachyarrhythmias.

Alpha and beta adrenergic effects on human atrial specialized conducting fibers.

We determined the effects of epinephrine on automaticity and action potential characteristics of right atrial specialized fibers (RAF) from human atria obtained during cardiac surgery. RAF were studied with standard microelectrode techniques during superfusion with Tyrodes solution at 37°C. A biphasic response to epinephrine was seen, rate slowing at low agonist concentrations and increasing at high concentrations. The epinephrine-induced slowing of spontaneous rate was due to a decrease in the slope of phase 4 depolarization. At the high epinephrine concentrations RAF hyperpolarized. The a-adrenergic blocker, phentolamine, shifted the dose-response curve upward and to the left and enhanced the hyperpolarization of RAF. The /3 blocker, propranolol, shifted the curve to the right and decreased the degree of hyperpolarization. Our study suggests the presence of a and, B receptors in RAF. The a response consists of a slowing of rate, the # response of an acceleration of rate and hyperpolarization of RAF.

Transvenous pacemakers in children: Relation of lead length to anticipated growth

Although transvenous pacing is feasible in infants and children, uncertainty remains as to how to allow for future growth at the time of lead insertion. Accordingly, we retrospectively reviewed the relation between age and transvenous lead length. Standard posteroanterior chest roentgenograms were reviewed for 26 patients with transvenous pacemakers inserted at Babies Hospital and Presbyterian Hospital between 1985 and 1989. Sixteen of these were children (age range, 0.75 to 15 years) and 10 were adults (age range, 27 to 90 years). The intravascular length of right ventricular pacing leads was measured as projected on the roentgenogram. In 10 children, the presence of lead loops in the right atrium required the lead length that would have resulted from conventional placement to be estimated. Results for right ventricular pacing lead lengths were correlated with age using linear regression analysis. Average uncorrected lead length measured on the roentgenogram was 345 +/- 35 mm (standard deviation) in adults and 222 +/- 51 mm in children. The use of right atrial loops increased implanted lead length by an estimated 79 mm, from 188 +/- 26 to 267 +/- 43 mm. The difference between lead length in children and adults was analyzed. Approximately 190 mm of additional right ventricular pacing lead in infants and 100 mm in 10-year-old children was needed for growth to adult size. We conclude that an 80-mm right atrial lead loop will allow 6 to 12 years (mean, 8 years) of growth in infants and children without the need for reoperation to adjust lead length.

ACUTE PULMONARY EMBOLISM IN PEDIATRIC PATIENTS AWAITING HEART TRANSPLANTATION

Acute pulmonary embolism with infarction can delay urgently needed heart transplantation and increase the postoperative pulmonary complications. Few data are available concerning pulmonary embolization in the pediatric patient with end-stage congestive heart failure. Sixty-two consecutive pediatric patients awaiting heart transplantation were monitored for evidence of acute pulmonary embolism. Acute pulmonary infarction was documented by ventilation-perfusion scan, pulmonary angiography or pathologic examination in six patients. The prevalence differed by diagnosis; 5 of 36 patients with dilated cardiomyopathy and 1 of 20 patients with congenital heart disease developed acute pulmonary embolism with infarction. No significant difference in age at the time of transplantation evaluation, duration of congestive heart failure, presence of cardiac arrhythmias or degree of cardiac dysfunction was seen between patients with and without pulmonary embolism. Two-dimensional echocardiography failed to detect the presence of an intracardiac thrombus in four of the six patients. Two patients who developed acute pulmonary infarction are alive after successful heart transplantation. The remaining four patients died within 6 weeks of initiation of anticoagulant therapy before transplantation could safely be performed. In summary, pediatric patients with end-stage congestive heart failure are at risk for acute pulmonary embolism. No specific clinical factor identified those patients who developed acute pulmonary infarction. Anticoagulant therapy is strongly recommended in the pediatric patient with poor ventricular function awaiting heart transplantation.

Serial echocardiographic measurements of the pulmonary autograft in the aortic valve position after the Ross operation in a pediatric population using normal pulmonary artery dimensions as the reference standard.

Serial echocardiographic measurements of the annulus and sinus were obtained in children before the Ross operation, and early and late postoperatively. Values were compared with normal standards for the aorta and pulmonary artery (PA). There was no significant difference between PA annulus measurements before surgery and the corresponding autograft immediately afterward (1.73 +/- 0.60 cm preoperatively; 1. 63 +/- 0.58 cm postoperatively, p = NS). Late after surgery the mean annulus diameter was enlarged compared with the normal aorta (DeltaZ 1.9 +/- 2.4), but remained relatively unchanged compared with the normal PA (DeltaZ 0.7 +/- 1.1, p <0.01). In contrast, the autograft sinus was dilated early after surgery (1.83 +/- 0.58 cm preoperatively; 2.18 +/- 0.73 cm postoperatively, p <0.01). Mean sinus Z score further increased compared with both the aorta (DeltaZ 1.3 +/- 1.7) and PA (DeltaZ 1.3 +/- 1.6). Use of standard PA measurements may be important in the assessment of autograft enlargement. Minimal change in autograft Z scores over time suggests that annulus enlargement is mainly due to somatic growth. In contrast, the autograft sinus showed an immediate and continued disproportionate increase in size over time, suggesting that sinus enlargement is largely due to passive dilation.