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Biomedical subjects

A Hamer

Publications and source records attributed to A Hamer.

At least 19 recordsLinked to original sources
PubMed1999

Significance of isolated bradycardia detected by home monitoring.

OBJECTIVE: To determine the cause of isolated bradycardia during home cardiorespiratory monitoring. SETTING: A tertiary care hospital. STUDY DESIGN: A retrospective review of the charts of 8 patients with severe isolated bradycardia on their home monitoring reports. All subjects underwent polysomnography including a pH probe. RESULTS: Monitor reports showed a characteristic pattern of long (30 to 60 seconds) periods of bradycardia, sometimes with asystole, associated with irregular respiratory efforts. All patients had severe gastroesophageal reflux, with a pH <4 for 63% +/- 22% (mean +/- SD) of recording time. No patient had other abnormalities to explain the bradycardia. Bradycardia resolved after successful treatment of reflux. CONCLUSION: A pattern of isolated bradycardia associated with irregular respiratory efforts on home monitoring is highly suggestive of gastroesophageal reflux and should prompt further evaluation and treatment.

Apnea↗
PubMed1999

Developmental changes in response to subatmospheric pressure loading of the upper airway.

Children snore less than adults and have fewer obstructive apneas, suggesting a less collapsible upper airway. We therefore hypothesized that the compensatory upper airway responses to subatmospheric pressure loading decrease with age because of changes in upper airway structure and ventilatory drive. We measured upper airway upstream pressure-flow relationships during sleep in 20 nonsnoring, nonobese children and adults. Measurements were made by correlating maximal inspiratory airflow with the level of nasal pressure applied via a mask. The slope of the upstream pressure-flow curve (S(PF)) was used to characterize upper airway function. We found that S(PF) was flatter in children than in adults (8 +/- 5 vs. 30 +/- 18 ml x s(-1). cmH(2)O(-1), P < 0.002) and that S(PF) correlated with age (r = 0.62, P < 0.01) and body mass index (r = 0. 63, P < 0.01). The occlusion pressure in 100 ms during sleep was measured in six children and two adults; it correlated inversely with S(PF) (r = -0.80, P < 0.02). We conclude that the upper airway compensatory responses to subatmospheric pressure loading decrease with age. This is associated with increased body mass index, even in nonsnoring, nonobese subjects. Ventilatory drive during sleep plays a role in modulating upper airway responses.

Adolescent↗
PubMed1998

Natural history of primary snoring in children.

It is not known whether children with primary snoring (PS) progress to develop obstructive sleep apnea syndrome (OSAS). Therefore, we repeated polysomnography in a cohort of 20 children diagnosed 1-3 years previously with PS. All children initially presented with symptoms suggestive of OSAS. They were diagnosed with PS when initial polysomnography demonstrated snoring, with less than one obstructive apnea per hour, normal gas exchange, and infrequent arousals. Of 75 potential candidates, 20 were available for reevaluation (33 could not be contacted, 8 had undergone tonsillectomy and adenoidectomy, and 14 declined). Mean age was 6 +/- 4 (SD) years at the time of the initial study. The initial apnea index was 0.2 +/- 0.3, SpO2 nadir 95 +/- 2%, and peak end-tidal PCO2 was 47 +/- 3 mm Hg. At follow-up, all children were reported by their parents to still be snoring; in 20% snoring had reportedly increased, and in 70% there was no change. Eighty percent were thought to have difficulty breathing during sleep. For the group as a whole, there were no significant changes in apnea index, SpO2, or peak end-tidal PCO2. However, two children had mild OSAS on repeat polysomnography (apnea index of 3). We conclude that, in most children, primary snoring does not progress to OSAS over the course of several years. This study indicates that OSAS in the few individuals who do progress is mild. Parental concern about children's breathing patterns during sleep is a poor predictor of polysomnographic abnormalities. However, because many patients were lost to follow-up in this study, further prospective studies are needed.

Adolescent↗
PubMed1996

To determine the effects of ultraviolet light, natural light and ionizing radiation on pyridinium cross-links in bone and urine using high-performance liquid chromatography.

The aims of the study were to characterize the denaturation of urinary free and conjugated pyridinoline (Pyr) and deoxypyridinoline (Dpyr) on exposure to ultraviolet (UV) and natural light at different pH levels and to study the effects of X- and gamma-irradiation on Pyr and Dpyr in urine and in the mineralized and non-mineralized compartments of human bone. Urine samples from six normal subjects, adjusted to pH 3.0, 7.0 and 9.0 were exposed to UV light for up to 3 days. Urine collections (2 mL and 24 h) from three subjects, pH adjusted to 1.0, 2.0, 3.0, 4.0 and 5.0, were exposed to natural light for up to 1 day. Urine samples and bone slices from seven human cadaveric femurs were irradiated with increasing doses of X-rays (0-100 Gy) and high-dose gamma-radiation (28 kGy). Mineralized and non-mineralized bone were separated using a modification of a published method employing heat denaturation followed by trypsin hydrolysis and analysed for Pyr, Dpyr and hydroxyproline (Hypro). The rate of UV photolysis of urinary Pyr and Dpyr increased with pH and was faster in the free fraction (after 3 days' exposure: free Pyr and Dpyr at pH 7.0 vs. 9.0, P < 0.05, conjugated pH 3.0 vs. 9.0, P < 0.05). Exposure to natural light for 3 h did not significantly decrease urinary Pyr and Dpyr in either sample collections, but levels were reduced in the 2-mL aliquots after exposure for 1 day (P < 0.05). X-irradiation of urine and bone did not affect Pyr and Dpyr. Pyr content was similar in both bone compartments (Pyr/ Hypro = 0.12 +/- 0.004), but Dpyr was higher in the non-mineralized compartment (Dpyr/Hypro = 0.047 +/- 0.002 vs. 0.038 +/- 0.002, P < 0.001). UV light and gamma-irradiation result in denaturation of pyridinium cross-links in urine. These cross-links are present in both the mineralized and non-mineralized bone compartments but are not affected by the doses of gamma-irradiation that denature these cross-links in urine.

Amino Acids↗
PubMed1994

Determinants of growth in children with the obstructive sleep apnea syndrome.

Failure to thrive is a common complication of childhood obstructive sleep apnea syndrome (OSAS). To further evaluate its cause, we obtained 3-day dietary records, anthropometric measurements, polysomnography, and measurements of energy expenditure during sleep (SEE) in children with OSAS before and after tonsillectomy and adenoidectomy. Fourteen children were studied (mean age, 4 +/- 1 (SD) years). During initial polysomnography, patients had 6 +/- 3 episodes of obstructive apnea/hr, an arterial oxygen saturation nadir of 85% +/- 8%, and peak end-tidal carbon dioxide tension of 52 +/- 6 mm Hg. After surgery, OSAS resolved in all patients. The standard deviation score (z score) for weight increased from -0.30 +/- 1.47 to 0.04 +/- 1.34 (p < 0.005), despite unaltered caloric intake (91 +/- 30 vs 90 +/- 27 kcal/kg per day; not significant). The initial SEE (averaged over all sleep states) was 51 +/- 6 kcal/kg per day; postoperatively, it decreased to 46 +/- 7 kcal/kg per day (p < 0.005). Although SEE decreased during all sleep stages, the greatest decrease occurred during rapid eye movement sleep. The patients with the highest SEE on initial study had the lowest z scores (r = -0.62; p < 0.05). We conclude that SEE decreases and weight improves after resolution of OSAS. We speculate that the poor growth seen in some children with OSAS is secondary to increased caloric expenditure caused by increased work of breathing during sleep.

Child↗
PubMed1992

Tissue plasminogen activator using a rapid-infusion low-dose regimen for unstable angina.

The clinical effect of a low-dose rapid-infusion intravenous regimen was assessed using human recombinant tissue-type plasminogen activator (rt-PA) in unstable angina. Fifty patients with unstable angina pectoris were randomly assigned to blinded treatment with either placebo (24 patients) or low-dose (20 mg bolus, 30 mg infusion over 1 hour) intravenous rt-PA (26 patients). Before randomization, all patients were treated with aspirin, twice-daily subcutaneous heparin, and maximally tolerated antianginal therapy. Of the 50 patients assigned, 26 received rt-PA and the outcome was successful in 15 (58%) (angina settled, no myocardial infarction or urgent intervention) compared with 9 (38%) successful outcomes in the 24 who received placebo (0.5 greater than p greater than 0.1). Angina remained refractory in 8 (31%) of the rt-PA group and in 13 (54%) of the placebo group (0.1 greater than p greater than 0.05). Urgent interventions were required in 6 patients (23%) who received rt-PA and in 11 patients (46%) who received placebo. Three patients in each group sustained a myocardial infarction within 72 hours of entering the trial and there were 3 deaths (1 in the active treatment group, 2 in placebo group) within 2 weeks of the trial (p = not significant). Administration of intravenous rt-PA was not associated with any complications. Low-dose rt-PA administration in patients with unstable angina was associated with a tendency to stabilization of anginal symptoms and a reduction in the need for urgent intervention. However, these trends did not achieve statistical significance.

Aged↗
PubMed1992

Clinical experience with surgery for paroxysmal supraventricular tachycardia: a report of 103 cases.

One-hundred-and-three patients underwent surgery for paroxysmal supraventricular tachycardia (PSVT). In eighty-three patients (81%), PSVT was due to an accessory atrioventricular pathway (Group I) and in 20 (19%) to Atrioventricular Junctional (AV nodal) Reentrant Tachycardia (AVJRT:Group II). Initial surgery successfully divided 77 of 83 accessory pathways, including 58 of 60 left free wall pathways, 12 of 15 posteroseptal pathways, six of seven right free wall pathways and one anteroseptal pathway. Twenty patients had successful surgery for AVJRT. Surgery was performed with low morbidity and no early or late mortality in either group. One patient in each group required permanent pacemaker implantation. Immediate (within one week) postoperative electrophysiological study using epicardial wires was performed in 96% of patients and repeat electrophysiological study six months later was possible in 65/103 (63%) patients. Patients with surgery for accessory pathways were followed-up for a mean 34 +/- 23 months, while those with surgery for AVJRT for a mean of 13 +/- seven months. No patient with successful surgery has had a clinical recurrence of PSVT. Thus the results indicate that surgery is a safe and curative therapy for patients with PSVT.

Adolescent↗
PubMed1990

Colorimetric enumeration of Escherichia coli based on beta-glucuronidase activity.

A medium containing a chromogenic substrate was developed for the enumeration of Escherichia coli on the basis of beta-glucuronidase activity. In this medium there was an inverse linear relationship between the log initial E. coli concentration and the time taken for the color to reach a threshold optical density of 0.05. This relationship applied even when the E. coli population contained 5% beta-glucuronidase-negative cells. Incubation at 44 degrees C reduced the time taken for color development and allowed the procedure to be used in the presence of a competitive microflora that outnumbered the E. coli population by a factor of 10(4). Sodium lauryl sulfate as an additional selective agent gave no significant improvement. In the analysis of environmental water samples, the technique gave a good correlation with a standard cultural method. The procedure shows promise as a simple method for testing the compliance of environmental samples with microbiological criteria for E. coli.

Chromogenic Compounds↗
PubMed1985

The yield of programmed ventricular stimulation in mitral valve prolapse patients with ventricular arrhythmias.

A high-risk subset of patients with mitral valve prolapse (MVP) and a predisposition to sudden cardiac death (SCD) has been proposed. We analyzed the results of programmed ventricular stimulation (PVS) in 20 patients with MVP and ventricular arrhythmias (ventricular premature depolarization in 6, ventricular couplets in 2, nonsustained ventricular tachycardia [VT] in 7, ventricular fibrillation [VF] in 5) and in 12 "normal" control subjects. With the use of an identical stimulation protocol from the right ventricular apex (twice diastolic threshold, three extrastimuli), 9 of 20 MVP patients and 1 of 12 normal subjects had inducible ventricular arrhythmias (p less than 0.05). When more aggressive attempts at ventricular stimulation were used, an additional five MVP patients had positive responses to PVS while no normal subjects did. In the MVP group, the following arrhythmias were induced: nonsustained polymorphic VT in 10, VF in three, and ventricular flutter in one. In all but two patients, triple ventricular extrastimuli were required to elicit this response. Two of the 10 MVP patients undergoing electropharmacologic testing had a successful antiarrhythmic regimen identified, while 13 patients were discharged on empiric antiarrhythmic therapy. At a follow-up of 19.8 +/- 13.1 months, all 19 MVP patients who could be contacted were alive. Five patients had symptomatic recurrences at follow-up including two SCD survivors (VT in one and VF in one). In conclusion, it was found that the majority of MVP patients with ventricular arrhythmias have inducible ventricular tachyarrhythmias during PVS and are more susceptible to this than patients without structural heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Evaluation of amiodarone therapy in the treatment of drug-resistant cardiac arrhythmias: long term follow-up.

The clinical efficacy of amiodarone in the management of patients with complex cardiac arrhythmias refractory to therapy with two or more conventional or other investigational anti-arrhythmic agents was studied by long-term follow-up of patients who had received the drug for a period of at least three months. A total of 181 patients, classified into four groups (Group 1--supraventricular arrhythmias, n = 42; Group 2--frequent VPBs, n = 46; Group 3--nonsustained V-tach, n = 16; and Group 4--sustained V-tach, n = 77) received a daily maintenance dose of 200-800 mg of Amiodarone for a period of up to 30 months. There were a total of 26 deaths (14%). Ten of these were classified as probable arrhythmic deaths; however, all had either good or excellent response to therapy over a mean follow-up period of 14.9 months prior to death. The drug had to be permanently discontinued due to side effects only in three patients and in the majority of patients with side effects symptoms could be alleviated with adjustment of dosage, thyroid replacement therapy or transient cessation of therapy. We conclude that amiodarone is highly effective in the management of high-risk patients with complex refractory cardiac arrhythmias and that close monitoring and prompt recognition of side effects and appropriate adjustment of dosage or institution of supplemental or replacement therapy (in less than 5% of patients) will allow continuation of amiodarone. The benefit of suppression of symptomatic arrhythmias and the potential of prevention of sudden death, far outweighs the incidence of severe side effects.

Adolescent↗
PubMed1984

Prognosis after sudden cardiac death without associated myocardial infarction: one year follow-up of empiric therapy with amiodarone.

Thirty-three consecutively referred patients with cardiac arrest from ventricular arrhythmias unassociated with a new acute myocardial infarction (AMI) were commenced on amiodarone therapy and followed for a minimum of 12 months. The dose of amiodarone was adjusted to maximum tolerance and not according to the incidence of asymptomatic ventricular premature complex activity. Eight patients died including five sudden deaths. Five out of the eight deaths occurred either within 3 months of therapy or when the dose of amiodarone was less than 400 mg/day. The majority of patients were found to have corneal microdeposits or either thyroid or liver function abnormalities, although none had any clinical manifestation. Ten patients had neurologic side effects. In summary, although the overall cardiac mortality seemed to be reduced by amiodarone therapy and the drug appears to be well tolerated by patients, its role in the prophylaxis against recurrent ventricular fibrillation may be enhanced by a regimen of higher loading and maintenance doses.

Adult↗
PubMed1983

Evaluation of amiodarone therapy in the treatment of drug-resistant cardiac arrhythmias: long-term follow-up.

The clinical efficacy of amiodarone in the management of complex cardiac arrhythmias refractory to therapy with two or more conventional or other investigational antiarrhythmic agents was determined by long-term follow-up in patients who had received the drug for at least 3 months. A total of 181 patients, classified into four groups (group 1, supraventricular arrhythmias, n = 42; group 2, frequent ventricular premature complexes, n = 46; group 3, nonsustained ventricular tachycardia, n = 16; and group 4, sustained ventricular tachycardia, n = 77) received a daily maintenance dose of 200 to 800 mg amiodarone for up to 30 months. There was a total of 26 deaths (14%). Ten of these were probably attributable to arrhythmia, although all patients had either good or excellent response to therapy over a mean follow-up of 14.9 months prior to death. The drug had to be permanently discontinued because of side effects in only three patients, and in the majority of patients with side effects, symptoms could be alleviated with adjustment of dosage, thyroid replacement therapy, or temporary cessation of therapy. We conclude that amiodarone is highly effective in high-risk patients with complex refractory cardiac arrhythmias, and that close monitoring and prompt recognition of side effects and appropriate adjustment of dosage or institution of supplemental or replacement therapy (in less than 5% of patients) will allow continuation of amiodarone. The benefit of suppression of symptomatic arrhythmias and the potential of prevention of sudden death clearly outweigh the modest incidence of severe side effects.

Aged↗
PubMed1983

Electrophysiologic studies in survivors of late cardiac arrest after myocardial infarction.

Nine patients resuscitated from life-threatening ventricular arrhythmias (VA) within 3 months of an acute myocardial infarction (AMI) underwent electrophysiologic studies (EPS) with clinical follow-up for at least 12 months. Neither reinfarction, drug therapy, nor electrolyte imbalance was a precipitating factor. VA was induced by ventricular pacing in six of nine patients. Five patients were prescribed empiric drug therapy, while the four other patients had repeated EPS to select optimal drug therapy. One patient remained unstable and died of VA in the hospital. No patient was discharged and successfully maintained on a drug known to prevent induction of VA, yet only two patients (25%) had a further recurrence of VA, one fatal. Our findings suggested that either drug therapy that is determined empirically or found not to suppress the induction of VA during EPS can be associated with a successful outcome in some of these patients, or the natural history of VA after myocardial infarction is that they are self-limiting in the absence of a new ischemic event.

Arrhythmias, Cardiac↗