The dicrotic pulse: a common, non-ominous finding after the Ross operation.

We noted a dicrotic pulse in several patients following a Ross operation. Although the etiology of this unique arterial waveform is not completely understood, it has been reported as a sign of low cardiac output and a poor prognosis. We reviewed preoperative echocardiograms and postoperative radial arterial pressure tracings in 33 patients who underwent a Ross procedure between 2000 and 2004. We found a dicrotic pulse to occur commonly (20/33; 61%) following a Ross operation. Moderate to severe preoperative aortic insufficiency was present in 19/20 patients (95%) in whom a dicrotic pulse was noted and in only 3/13 (23%) who did not exhibit a postoperative dicrotic pulse (p<0.001). A dicrotic pulse was not associated with an increased use of vasoactive infusions or longer hospitalization following the Ross operation. The dicrotic pulse should be recognized as a common postoperative finding in Ross patients that does not herald a delayed postoperative convalescence. The mechanism for a dicrotic pulse in these patients is speculative but may result from changes in vascular compliance secondary to chronic aortic insufficiency.

Hemodynamic and electrophysiologic effects of acute chocolate ingestion in young adults.

The purpose of this study was to determine the hemodynamic and electrophysiologic effects of acute chocolate, and hence theobromine, ingestion on the hearts of young adults. Theobromine was not found to have any cardiovascular effects on subjects in this study.

Acute effects of caffeine ingestion on signal-averaged electrocardiograms.

BACKGROUND: Although moderate caffeine ingestion has not been shown to be arrhythmogenic, caffeine toxicity can cause severe cardiac arrhythmias, including atrial fibrillation and ventricular tachycardia. Atrial fibrillation and ventricular tachycardia have been associated with prolongation of P-wave and QRS complex durations on signal-averaged electrocardiograms. This study investigated acute effects of caffeine ingestion on signal-averaged P-wave and QRS complexes. METHODS AND RESULTS: Signal-averaged electrocardiograms were obtained from 12 normal subjects (6 men, 6 women; ages 21 to 26 years) before and after ingestion of caffeine (5 mg/kg body weight) or placebo in a randomized, double-blind, crossover fashion. Electrocardiograms for signal averaging were recorded from electrodes left in a constant location. After bandpass filtering (30 to 300 Hz) and amplification, signals were sampled over 7.2 minutes at 2000 Hz. Signal-averaged P-wave and QRS complex durations did not significantly change after placebo ingestion. After caffeine ingestion QRS duration prolonged in 9 of 11 subjects at 90 minutes (mean +/- SEM = 0.8+/-0.3 ms, P< .02) and in 8 of 9 after 3 hours (1.1+/-0.2 ms, P< .001). No significant change in P-wave duration or heart rate was found after caffeine ingestion at any test interval. Average caffeine level in saliva 90 minutes after ingestion was 6.6+/-1.6 (SD) microg/dL. CONCLUSIONS: Although probably not arrhythmogenic in normal subjects, moderate caffeine ingestion does produce a small but statistically significant prolongation of signal-averaged QRS complexes. Further prolongation caused by excessive caffeine intake may be a factor in the genesis of arrhythmias associated with caffeine toxicity.

Hemodynamic effects of acute caffeine ingestion in young adults.

This study investigated hemodynamic effects of acute caffeine ingestion in young adults 21 to 26 years of age. Data showed an increase in heart rate corrected velocity of circumferential fiber shortening at an indexed afterload up to 4.5 hours following caffeine consumption.

Hemodynamic effects of acute ethanol in young adults.

Hemodynamics effects of ethanol were studied in young adults at specific predetermined ethanol levels of 0.025%, 0.05%, and 0.75%. Findings included a decrease in end-systolic wall stress (afterload) and myocardial contractility following ingestion of ethanol at concentrations found in "social drinking."

Transcatheter closure of residual atrial septal defect following implantation of buttoned device.

We report a case in which residual shunting after a buttoned device occlusion of atrial septal defect (ASD) was eliminated by transcatheter retrieval of a portion of the device, followed by implantation of a second device. This method may be helpful for those patients with residual ASDs who decline surgical device retrieval and defect closure.

Pulmonary atresia associated with maternal 22q11.2 deletion: possible parent of origin effect in the conotruncal anomaly face syndrome.

A blind study was designed to test the hypothesis that some persons with a relatively rare cardiac malformation, pulmonary atresia with ventriculoseptal defect (PA/VSD), have a recognisable phenotype. Fourteen patients with cyanotic congenital heart lesions were examined by dysmorphologists blinded to the type of cardiac malformation. Six children were judged to have a similar craniofacial appearance; all had PA/VSD. These children were not originally considered to fall within the classic phenotypes of the DiGeorge sequence or the velocardiofacial syndrome, both of which have been shown to be associated with deletions of 22q11. More recently, 22q11 deletions have been documented in the conotruncal anomaly face syndrome and apparently isolated conotruncal heart defects. A new acronym, CATCH 22 syndrome (Cardiac defects, Abnormal facies, Thymic hypoplasia, Cleft palate, and Hypocalcaemia) has been suggested to encompass this very broad phenotypic spectrum. A preliminary molecular study was conducted using the dinucleotide repeat D22S264 located on chromosome 22q11.2. All cases tested with the subtle but recognisable phenotype had deletions, all lacking the maternal contribution at this locus, suggesting there may be a parent of origin effect.

Complex atrial tachycardias and respiratory syncytial virus infections in infants.

Respiratory syncytial virus (RSV), a common cause of respiratory infections in children, has only rarely been associated with acquired heart disease. We reviewed hospital charts, rhythm strips, and electrocardiograms of 8 infants with abnormal supraventricular tachycardia (SVT), > 250 beats/min, associated with acute RSV infections. Cultures of nasopharyngeal specimens from six of eight infants grew RSV. Two infants with negative viral culture results had symptoms typical of an RSV infection during a documented RSV epidemic. Two infants had congenital heart defects. Seven of the eight infants had an ectopic atrial tachycardia, chaotic atrial tachycardia, or atrial flutter, and five of eight had episodes of nonsustained wide-complex SVT. One patient was initially treated with intravenously administered lidocaine for an incorrect diagnosis of ventricular tachycardia. SVT was unrelated to either beta-agonist therapy or hypoxic episodes. SVT did not recur after discharge in any infant with a structurally normal heart. Both patients with structural heart disease had recurrences of SVT. We conclude that RSV infections in infants may be associated with unusual atrial tachycardias and that the diagnosis may be complicated by episodes of nonsustained, wide-complex tachycardias. In patients with RSV and structurally normal hearts, chaotic and ectopic atrial tachycardias are self-limited and do not require prolonged drug therapy.

Dobutamine pharmacokinetics and pharmacodynamics in normal children and adolescents.

Pharmacokinetic and pharmacodynamic data on adrenergic agents in children have revealed wide ranges of plasma clearance rates and hemodynamic responses in patients with critical illnesses or myocardial dysfunction. In order to more clearly elucidate the underlying pharmacologic processes, graded i.v. dobutamine infusions of 0.5, 2.5 and 5.0 micrograms/kg/min were sequentially administered to healthy children and adolescents. Plasma dobutamine concentrations and hemodynamic responses, including echocardiographic measures of systolic and diastolic function, were determined at each infusion rate. Pharmacodynamic data were evaluated by both threshold modeling and mean hemodynamic responses to each infusion rate. Mean plasma dobutamine clearance was 115 +/- 63 ml/kg/min, with an intersubject variability greater than 5-fold. These data establish that the previously published wide variability in dobutamine clearance is not due simply to underlying disease states. Dobutamine clearance was linear over the dosage range evaluated. Dobutamine improved systolic function even at plasma concentrations attained with infusion rates as low as 1 to 2 micrograms/kg/min. The improved systolic function was at least partially due to inotropic effects. In addition, dobutamine improved diastolic function and reduced afterload. Chronotropic effects were observed in only two subjects and only at higher plasma concentrations than the other hemodynamic effects. Individualized threshold modeling effectively described the log-linear relationship between plasma dobutamine concentration and hemodynamic response beyond the threshold concentration.

Dobutamine infusions in stable, critically ill children: pharmacokinetics and hemodynamic actions.

OBJECTIVE: To delineate dobutamine pharmacokinetics and hemodynamic responses in children. DESIGN: Prospective, pharmacokinetic study using sequential, graded dosing of drug. INTERVENTIONS: Graded intravenous dobutamine infusions of 0.5, 2.5, 5, 10, and 20 micrograms/kg/min were sequentially administered for 25 mins each. Plasma dobutamine concentrations and echocardiographically determined hemodynamic data were obtained at baseline and at 15 and 25 mins during each infusion rate. Hemodynamic responses were evaluated by paired t-test and by computerized evaluation of individual dose-response curves. SETTING: Pediatric intensive care unit in a university setting. PATIENTS: Eleven stable, critically ill children previously requiring inotropic support with dobutamine. Seven patients were postcardiac surgical patients; four patients had acute cardiac dysfunction with septic shock and/or adult respiratory distress syndrome. MEASUREMENTS AND MAIN RESULTS: Mean cardiac index increased from 3.8 to 5.2 L/min/m2 (p < .05). Increasing the infusion rate from 10 to 20 micrograms/kg/min increased cardiac index by 16% (p < .05). Cardiac index increased by > 10% in four of seven patients at a dobutamine infusion rate of 0.5 microgram/kg/min (mean 21%). The relationship of plasma dobutamine concentration to cardiac index, systolic blood pressure, and heart rate fit a threshold model with a log-linear relationship after the threshold in seven of nine, seven of 11, and eight of 11 patients, respectively. As anticipated, in the patients who responded, there were linear increases in hemodynamic responses with exponential increases in plasma dobutamine concentrations. Mean plasma clearance rate was 82 +/- 3 mL/min/kg. First-order kinetics were demonstrated by the direct linear relationship of plasma dobutamine concentration to infusion rate (mean r2 = .95; p < .01 for each patient) and by independence of clearance from dose and duration of each infusion. CONCLUSIONS: Dobutamine effectively improves systolic function in critically ill children. Hemodynamic responses to dobutamine generally follow a predicted log-linear dose-response model. Dobutamine clearance in this study was consistent with first-order kinetics. The wide variability in hemodynamic responses and clearance kinetics indicate that dobutamine infusions must be titrated individually.

Accuracy of central venous pressure measurement from the abdominal inferior vena cava.

Central venous pressure measurements in the abdominal inferior vena cava were compared with measurements in the right atrium in 10 infants and 10 children during cardiac catheterization. At end expiration, the mean pressures at these two sites were within 1 mm Hg of each other in all 20 patients, with a mean difference of 0.0 +/- 0.36 mm Hg. The abdominal inferior vena cava is a safe and convenient site for measurement of central venous pressure, and our study confirms that such measurements are accurate.

Dobutamine stress echocardiography: a sensitive indicator of diminished myocardial function in asymptomatic doxorubicin-treated long-term survivors of childhood cancer.

Doxorubicin is an effective anticancer chemotherapeutic agent known to cause acute and chronic cardiomyopathy. To develop a more sensitive echocardiographic screening test for cardiac damage due to doxorubicin, a cohort study was performed using dobutamine infusion to differentiate asymptomatic long-term survivors of childhood cancer treated with doxorubicin from healthy control subjects. Echocardiographic data from the experimental group of 21 patients (mean age 16 +/- 5 years) treated from 1.6 to 14.3 years (median 5.3) before this study with 27 to 532 mg/m2 of doxorubicin (mean 196) were compared with echocardiographic data from 12 normal age-matched control subjects. Graded dobutamine infusions of 0.5, 2.5, 5 and 10 micrograms/kg per min were administered. Echocardiographic Doppler studies were performed before infusion and after 15 min of infusion at each rate. Dobutamine infusion at 10 micrograms/kg per min was discontinued after six studies secondary to a 50% incidence rate of adverse symptoms. The most important findings were that compared with values in control subjects, end-systolic left ventricular posterior wall dimension and percent of left ventricular posterior wall thickening in doxorubicin-treated patients were decreased at baseline study and these findings were more clearly delineated with dobutamine stimulation. End-systolic left ventricular posterior wall dimension at baseline for the doxorubicin-treated group was 11 +/- 1.9 mm versus 13.1 +/- 1.5 mm for control subjects (p less than 0.01). End-systolic left ventricular posterior wall dimension at the 5-micrograms/kg per min dobutamine infusion for the doxorubicin-treated group was 14.1 +/- 2.4 mm versus 19.3 +/- 2.6 mm for control subjects (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Accuracy of central venous pressure monitoring in the intraabdominal inferior vena cava: a canine study.

STUDY OBJECTIVE: To test the hypotheses that in multiple pathophysiologic settings (1) end-expiratory central venous pressure measurements in the intraabdominal inferior vena cava accurately reflect those in the superior vena cava and (2) mean central venous pressure monitoring is as reliable in the inferior vena cava as it is in the superior vena cava. DESIGN: Simultaneous inferior vena caval and superior vena caval pressures were measured during five ventilatory phases: apnea, end-expiratory mechanical ventilation, maximal inspiratory mechanical ventilation, end-expiratory spontaneous ventilation, and maximal inspiratory spontaneous ventilation. Measurements were repeated after progressive intravascular volume depletion. SUBJECTS: Eight puppies. MEASUREMENTS AND RESULTS: Simultaneous inferior vena caval and superior vena caval end-expiratory pressures did not differ significantly (mean differences 0 to 0.1 mm Hg) and the limits of agreement of these measurements were within 2 mm Hg. Differences between mean maximal inspiratory pressures in the inferior vena cava and superior vena cava during mechanical and spontaneous ventilation were -0.7 and 3.6 mm Hg, respectively (p less than 0.01), and the limits of agreement extended beyond 2 mm Hg. Furthermore, mean maximal inspiratory pressures in the superior vena cava differed from end-expiratory pressures in the superior vena cava (1.1 and -3.6 mm Hg, p less than 0.01), whereas those in the inferior vena cava did not differ from end-expiratory superior vena caval pressures. CONCLUSIONS: Under the experimental conditions studied (1) end-expiratory intraabdominal inferior vena caval pressures accurately reflected end-expiratory superior vena caval pressures and (2) mean central venous pressure monitoring was as reliable in the inferior vena cava as in the superior vena cava.