David P. Chan

Outcome of symptomatic patients undergoing extracardiac Fontan conversion and cryoablation

OBJECTIVEnWe review our experience with Fontan conversion and cryoablation in patients with an atriopulmonary Fontan in low cardiac output from arrhythmia or venous obstruction, including 2 patients with protein-losing enteropathy.nnnMETHODSnTen patients (mean age 21.1 +/- 7.0 years) underwent extracardiac Fontan conversion, cryoablation, and pacemaker placement between November 1999 and April 2002 (13.1 +/- 4.1 years after the original atriopulmonary connection). Eight patients were in New York Heart Association class III and 2 were in New York Heart Association class IV. Nine patients had clinically important intra-atrial reentry tachycardia refractory to medical therapy.nnnRESULTSnFollow-up was between 3.1 and 32.6 months (16.8 +/- 9). One death occurred at 7 days after surgery due to sepsis and multisystem organ failure. The second death occurred at 48 days from complications of protein-losing enteropathy. The second patient with protein-losing enteropathy had improved New York Heart Association classification, cessation of albumin transfusions, and a normal stool alpha antitrypsin level (down from 4.1 mg/g preoperatively). Five patients improved to New York Heart Association class I and 3 patients to New York Heart Association class II. Sustained arrhythmias could not be induced in any patient. Seven patients are on no antiarrhythmics. One patient had recurrence of intra-atrial reentrant tachycardia 11 months postoperatively, which required electrical cardioversion; this patients symptoms are currently well controlled on 1 medication.nnnCONCLUSIONnExtracardiac Fontan, cryoablation, and pacemaker placement reduced atrial arrhythmias and improved New York Heart Association classification in all surviving patients. In selected patients, this operation offers improvement in clinical outcome and is an alternative to transplantation. Protein-losing enteropathy may not be a contraindication to performing Fontan conversion with cryoablation.

Digital Acoustic Analysis of Precordial Innocent Versus Ventricular Septal Defect Murmurs in Children

This study examines whether digital acoustic analysis of individual cardiac sound components for intensity, timing, and frequency could differentiate between innocent and pathologic murmurs. With use of this new technology, sensitive and specific criteria can be established for a fast and easy screening procedure to help differentiate between innocent and ventricular septal defect murmurs in children with suspected heart disease.

Effects of commonly used adrenergic agonists on left ventricular function and systemic vascular resistance in young piglets

This study compared the effects of high-dose infusions of various adrenergic agonists on cardiovascular function in piglets. We hypothesized that agonists would have different effects on systolic, diastolic, and vascular functions. Nine anesthetized 3-week-old piglets underwent cardiac catheterization. Manometric and conductance catheters measured pressures and volumes. Data were acquired at rest and during infusions of epinephrine, norepinephrine, dopamine, dobutamine, isoproterenol, and phenylephrine. End-systolic elastance, preload-recruitable stroke work, cardiac output, the maximum and minimum derivatives of left ventricular pressure, the relaxation constant tau, peak filling rate, and end-diastolic stiffness were obtained. Contractile efficiency and the cardiac output/pressure-volume area ratio were calculated. Regression was used for analysis of variance; p < 0.05 was considered significant. All agonists increased indexes of contractility. beta-Adrenergic agonists enhanced relaxation. Isoproterenol and dopamine increased efficiency. No drug changed diastolic stiffness. Therefore both alpha-adrenergic and beta-adrenergic agonists have inotropic effects in the 3-week-old piglet. Some beneficial effects of beta-agonists on cardiac output may be due to enhancement of relaxation and to afterload reduction. Various agents exert different effects on the cardiovascular system, and these differences may be clinically important.

Left Ventricular Systolic Function, Arterial Elastance, and Ventricular-Vascular Coupling: A Developmental Study in Piglets

Circulatory changes occur during perinatal life that increase cardiac output and left ventricular contractile reserve. To examine postnatal changes in left ventricular systolic function and ventricular-vascular coupling, piglets underwent cardiac catheterization at 1, 2, 4, and 6 wk of age. We measured end-systolic elastance (Ees), preload-recruitable stroke work, dP/dtmax, the dP/dtmax end-diastolic volume relation, cardiac index, heart rate, arterial elastance (Ea), and the ratio Ea/Ees at rest, during isoproterenol infusions (0.05-1.0 μg/kg/min), and after propranolol (1 mg/kg i.v.). Resting heart rate and cardiac index decreased between 1 and 6 wk. In 1 wk olds, resting Ees was at maximum and was unchanged during isoproterenol infusion; isoproterenol increased other contractility indices. Two, 4, and 6 wk olds demonstrated reserve using all contractility indices. Contractile efficiency was not different between ages. In 1 wk olds, Ea decreased during isoproterenol infusion; isoproterenol did not change Ea at 6 wk .Ea/Ees was higher at rest at 6 wk than at 1 wk, and fell significantly on isoproterenol; isoproterenol did not change Ea/Ees at 1 wk. Withβ-adrenergic stimulation, 1 wk olds increased cardiac index by increasing heart rate and decreasing afterload, 6 wk olds increased cardiac index by increasing heart rate and contractility; no change in contractile efficiency was found in either group. In summary, contractile reserve is limited at 1 wk when measured by Ees, but other indices demonstrated reserve. Indexed Ea falls in response to β-adrenergic stimulation in all ages but 6 wk. Ventricular-vascular coupling is optimized at 1 wk even under baseline conditions.

Tissue Doppler Changes in Pediatric Complete Heart Block Patients Who Are Chronically Paced

INTRODUCTIONnPediatric patients with complete heart block (CHB) often require pacemaker therapy. Adult studies have shown chronic right ventricular pacemaker therapy may be associated with decreased echocardiographic parameters and increased brain natriuretic peptide (BNP) values. The goal of this study was to determine if there are echocardiographic or BNP changes in a pediatric population that is chronically paced.nnnMETHODSnPatients were recruited if they had CHB and had a pacemaker. Patients were excluded if they had congenital structural heart disease. Standard two-dimensional echocardiograms, including tissue Doppler imaging (TDI), were performed. BNP values were obtained. Nonparametric Spearmans rank correlation was used for analysis. Rho < or = 0.05 was considered significant.nnnRESULTSnEighteen patients (16.4 +/- 7.3 years) with CHB were studied. Age at implant was 8.6 +/- 6.6 years and length of pacing was 7.8 +/- 6.6 years. Pacing mode was VDD, DDD, DDDR, or VVIR. All patients were ventricularly paced >95% of the time. Ejection fraction was 58.5 +/- 7.5%. All BNP values were <40 pg/mL. There was no correlation between ejection fraction or BNP level with the length of pacing years. Pacing years significantly correlated with mitral and tricuspid E/A ratios (rho =-0.56, -0.56, respectively). Pacing years also correlated with right ventricular and interventricular TDI a wave (rho = 0.61 and 0.68, respectively). Furthermore, pacing years correlated with right ventricular TDI e/a ratio (rho =-0.58).nnnCONCLUSIONSnEjection fraction and BNP levels were not sensitive parameters in evaluating pediatric patients who are chronically paced. Subtle diastolic changes, especially of the right ventricle, were detected by TDI.

Persistent electrical and morphological atrial abnormalities after early closure of atrial septal defect.

Atrial arrhythmias are associated with enlarged atrial chambers and an increased duration of the P wave. Repair of atrial defects within the oval fossa is expected to normalize atrial size. Few studies, however, have evaluated electrical and morphological atrial features after repair. Our study was performed to determine if atrial abnormalities exist after surgical closure of such atrial septal defects, and whether early closure improves outcome. We recruited patients who had undergone surgical closure of a defect within the oval fossa, so-called secundum atrial septal defects. Electrocardiograms, signal averaged electrocardiograms, and echocardiograms were performed. Two-tailed test and Pearson correlation was utilized for statistical analysis. The population consisted of 20 patients and 27 controls, with the mean age of the patient being 11.25 +/- 5.10 years, their age at surgery 6.55 +/- 5.10 years, and the time since surgery 4.70 +/- 2.61 years. The size of the right (23.88 +/- 6.35 ml/m2 versus 18.84 +/- 4.43 ml/m2) and left (21.91 +/- 12.47 ml/m2 versus 17.72 +/- 4.83 ml/m2) atrium were significantly larger in the patients. The duration of the P wave (108 +/- 16 ms versus 96 +/- 8 ms) and the duration of the PR interval (155 +/- 18 ms versus 138 +/- 23 ms) were longer. No correlation existed between age or interval since surgery with atrial sizes or measurements of the signal averaged electrocardiogram. We conclude that, despite surgical repair, abnormalities exist in patients with an atrial septal defect. Early surgery does not appear to prevent the atrial abnormalities.