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Biomedical subjects

A J Burger

Publications and source records attributed to A J Burger.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effect of glycemic control on heart rate variability in type I diabetic patients with cardiac autonomic neuropathy.

Diabetic cardiac autonomic neuropathy (CAN) is associated with a high risk of cardiovascular events. Previous studies have shown that strict glycemic control slows the deterioration of CAN as assessed by standard autonomic function tests but fails to show reversibility. The aim of this study was to evaluate the effect of glycemic control on early and advanced CAN in type I diabetic patients using power spectral analysis of heart rate variability (HRV). Ten patients with early and 13 patients with advanced CAN were enrolled in a program of intensified insulin treatment. Standard autonomic function tests and 24-hour time and frequency domain HRV parameters were obtained at baseline, 3, 6, and 12 months. Hemoglobin A1C decreased from 9.5 +/- 0.4% to 8.4 +/- 0.5% (p = 0.02) in the early CAN group, and from 9.3 +/- 0.4% to 8.2 +/- 0.5% (p = 0.006) in the advanced CAN group. In general, both time and frequency domain HRV indexes tended to improve in patients with early CAN but continued to deteriorate in patients with advanced CAN. The low- and high-frequency power increased in patients with early CAN (229 +/- 95 to 626 +/- 563 ms2 and 62 +/- 30 to 183 +/- 168 ms2, respectively). The high-frequency power significantly improved at 12 months over baseline (p = 0.04), indicating increased parasympathetic tone. By contrast, these parameters continued to deteriorate in patients with advanced CAN (65 +/- 32 to 46 +/- 8 ms2 and 193 +/- 75 to 144 +/- 33 ms2, respectively). Autonomic function tests showed no significant change in both groups. These data show that a reversible metabolic component of CAN exists in patients with early CAN. Power spectral analysis of HRV allows early identification of potential reversibility as early as 1 year after the institution of strict glycemic control.

Adult↗
PubMed1999

Circadian patterns of heart rate variability, fibrinolytic activity, and hemostatic factors in type I diabetes mellitus with cardiac autonomic neuropathy.

Diabetes mellitus is associated with a marked increase in the risk of coronary events but with an altered circadian distribution that demonstrates an absent morning peak and higher infarction rate during the evening hours. To elucidate the mechanism of this phenomenon, the circadian pattern of heart rate variability was evaluated in 22 type I diabetic patients with diabetic autonomic neuropathy in conjunction with circadian changes of fibrinolytic and hemostatic factors. The circadian pattern (6 A.M. to 10 P.M. vs 10 P.M. to 6 A.M.) of 3 indexes of parasympathetic tone was evaluated using 24-hour heart rate variability analysis. The high-frequency power (3.0 +/- 0.2 vs 3.3 +/- 0.2 ms2, p = 0.08) and the percentage of RR intervals with >50 ms variation (0.47 +/- 0.18 vs 0.69 +/- 0.33 ms, p = 0.52) demonstrated no significant circadian variation. The square root of mean squared differences of successive RR intervals showed a small but significant increase during nighttime (8.5 +/- 0.7 vs 9.7 +/- 1.1 ms, p = 0.02). Fibrinolytic activity was significantly lower at 8 A.M. than at 4 P.M. (166.4 +/- 12.5 to 200.2 +/- 9.3 mm2, p = 0.0003), but with a low amplitude. Plasminogen activator inhibitor 1 showed no circadian variation. Factor VII and fibrinogen demonstrated a significant reduction from 8 A.M. to 4 P.M., but both peak and nadir values were elevated. The von Willebrand factor was markedly elevated with no circadian variation. Thus, diabetic autonomic neuropathy is associated with a loss of both the nocturnal predominance of parasympathetic activity and a prothrombotic state that persists throughout the day. These abnormalities may attenuate the relative protection from coronary events during the afternoon and nighttime.

Adult↗
PubMed1999

Effect of beta-adrenergic blocker therapy on the circadian rhythm of heart rate variability in patients with chronic stable angina pectoris.

The circadian rhythm of heart rate variability is present in normal subjects and in patients with angina, with the greatest variation in the normal population and a smaller but significant variation in the anginal group. With beta-adrenergic blockade, significant improvement occurs in all daytime time domain parameters, nocturnal percentage of RR intervals with >50-ms variation, and square root of mean-squared differences of successive RR intervals, daytime total power, and high-frequency band, representing significant improvement in parasympathetic function.

Adrenergic beta-Antagonists↗
PubMed1999

Low prevalence of valvular heart disease in 226 phentermine-fenfluramine protocol subjects prospectively followed for up to 30 months.

OBJECTIVES: This investigation sought to determine the effect of phentermine-fenfluramine (phen-fen) on the prevalence of valvular heart disease in 226 obese subjects enrolled in a prospective, strict weight loss, research protocol. BACKGROUND: Early reports have suggested that the use of phen-fen for weight loss may be associated with increased valvular heart disease. Such reports were based on small numbers of patients, limited data on dose and duration of phen-fen therapy, and no correlation with matched controls. METHODS: All subjects underwent transthoracic echocardiography for significant valvular lesions within a mean of 97 days from the manufacturer's announcement of the voluntary withdrawal of fenfluramine and dexfenfluramine. All echocardiograms were interpreted by two independent readers. RESULTS: The study population included 183 women and 43 men with a mean age of 46.9 +/- 8.9 years and mean starting body mass index of 39.8 +/- 7.7 kg/m2. Using the Food and Drug Administration criteria, significant aortic regurgitation was detected in 15 subjects (6.6%) and mitral regurgitation in 3 subjects (1.3%). Only one patient had significant regurgitation of both aortic and mitral valves. No valves had severe regurgitation. Significant valvular disease did not correlate with the dose or duration of phen-fen therapy. Furthermore, the prevalence of valvular regurgitation is comparable to the normal offspring in the Framingham Heart Study, who are similar in age, gender, and geographical location. CONCLUSIONS: Phen-fen therapy is associated with a low prevalence of significant valvular regurgitation. Valvular regurgitation in our subjects may reflect age-related degenerative changes.

Adult↗
PubMed1998

Relation of heart rate variability and serum lipoproteins in type 1 diabetes mellitus and chronic stable angina pectoris.

This investigation examines whether serum lipoprotein levels in patients with diabetes mellitus and in those with coronary artery disease are associated with lower heart rate variability (HRV). The study group consisted of 58 subjects divided into 3 groups: normal subjects, chronic stable angina, and type 1 diabetes. Twenty-four-hour ambulatory electrocardiographic recordings were analyzed in the time and frequency domains; standard instantaneous autonomic testing was also performed. On 24-hour ambulatory recordings, patients with chronic stable angina had significantly lower HRV than normals, and diabetics had a more marked reduction in HRV than both normals and anginal patients. When anginal patients and diabetics were stratified by total serum and low-density lipoprotein (LDL) cholesterol levels, diabetics with elevated total and LDL cholesterol had an additional, significant decrease in HRV parameters. No such difference was demonstrated in patients with stable angina. No significant correlations were noted for high-density lipoprotein (HDL) cholesterol, triglycerides, or total cholesterol/HDL ratio and HRV in diabetics or patient with angina. Diabetics with markedly abnormal peripheral reflexes had significantly higher triglycerides and total cholesterol/HDL ratios. Finally, standard tests of autonomic function did not correlate with total, LDL, HDL cholesterol levels, total cholesterol/HDL ratio, or triglycerides. Thus, we found a relation between atherogenic lipid levels and reduced HRV in diabetic patients that has not been previously identified.

Adult↗
PubMed1997

Short- and long-term reproducibility of heart rate variability in patients with long-standing type I diabetes mellitus.

Heart rate variability (HRV) has been used to assess cardiac autonomic function noninvasively, understand the pathophysiologic mechanisms of heart disease, evaluate therapy, and assess long-term prognosis. We examined both the short- and long-term reproducibility of the time and frequency domain HRV parameters in 23 type I diabetics over a 12-month interval. Entry criteria included juvenile onset diabetes before age 35 years, >24-year duration of diabetes, diabetes difficult to control, and albuminuria. Standardized noninvasive autonomic testing and 24-hour ambulatory electrocardiographic recordings were obtained. Fifteen men and 8 women (mean age 36.7 years) were enrolled. Fifty-three percent of the men and 75% of the women were smokers, and women had higher cholesterol than men. All HRV parameters were markedly decreased when compared with normal persons. Using Pearson correlation, the time domain indicators of parasympathetic activity demonstrated very strong correlations at 3 and 6 months compared with baseline, with good correlations at 1 year. The average SD of all 5-minute RR intervals maintained a very strong correlation for the entire year (r >0.94). In the frequency domain, the measures of parasympathetic and sympathetic activity maintained a solid correlation for the entire study period. Reproducibility of HRV was also examined using repeated-measures analysis of variance. The time and frequency domain parameters demonstrated very little variation over the study period of 12 months. Thus, our investigation demonstrated that HRV in long-term diabetics using 24-hour ambulatory recordings is abnormal and reproducible over a 12-month interval; very little variation in all HRV parameters, especially in parameters of parasympathetic activity, occurred during the study period.

Adult↗
PubMed1996

Effect of beta adrenergic receptor blockade on cardiac autonomic tone in patients with chronic stable angina.

Decreased heart rate variability, which may be due to increased sympathetic and decreased parasympathetic activity, has been shown to be predictor of cardiac events after acute myocardial infarction. The present study was undertaken to analyze the effect of beta adrenergic blockade on cardiac autonomic system in patients with chronic stable angina. Nineteen patients (15 males and 4 females, age range 44-74 years) with chronic stable angina were enrolled. After stopping all cardiac medications, patients had two baseline treadmill tests with both reproducible angina and ST depression and a baseline 48-hour ambulatory ECG recording. A long-acting beta-blocker (atenolol or betaxolol) was started and titrated to the maximal tolerated dose. After 1-2 months, a repeat 48-hour ambulatory ECG recording on beta-blocker therapy was obtained. Heart rate variability analysis was performed on the baseline and drug therapy ECG recordings. The average heart rate significantly decreased (P < 0.008), and the mean RR interval significantly increased (P < 0.0001). In the time-domain analysis, the standard deviation, variance, ASDNN5, and SDANN5 were not significantly affected, although the PNN50 increased. In the frequency domain, the total power (P < 0.0001) and the low frequency (P < 0.001) components decreased, while the high frequency spectrum was unchanged. Thus, sympathetic activity significantly declined in patients with chronic stable angina on beta-blocker therapy, while parasympathetic tone demonstrated a heterogenous response.

Adrenergic beta-Antagonists↗
PubMed1995

Reproducibility of time and frequency domain analysis of heart rate variability in patients with chronic stable angina.

Before heart rate variability (HRV) can be used to investigate the effects of drugs or other clinical interventions in chronic stable angina, it is important to establish the stability and reproducibility of HRV indices over time. HRV analysis was performed on two consecutive 24-hour ambulatory ECG recordings in 19 patients with chronic stable angina. Time-domain analysis included average heart rate, variance, SDNN, SDANN5, ASDNN5 and PNN50. The power spectral analysis was computed using fast Fourier transformation for the total power (0.003 and 0.40 Hz), low frequency (0.04-0.15 Hz), and high frequency (0.15-0.40 Hz) bands. No statistically significant differences in the time or frequency domains were found between the two ambulatory ECG recordings. HRV indices in the time and frequency domains are consistent and reproducible in patients with chronic stable angina. Thus, cardiac autonomic tone can be evaluated using HRV analyses, and any significant changes that occur after medical therapy or other clinical interventions can be ascribed to the intervention rather than the lability of cardiac autonomic tone.

Adrenergic beta-Antagonists↗
PubMed1995

Use of dynamic two-dimensional transesophageal echocardiography for renal cell carcinoma with cavoatrial tumor thrombus.

Renal cell carcinoma with inferior vena caval tumor thrombus extending to the level of the right atrium occurs in about 1% of all cases. Dynamic two-dimensional transesophageal echocardiography is a minimally invasive safe technique that can demonstrate preoperatively the cephalad extent of the cavoatrial tumor thrombus with an accuracy that appears equal to or better than that of any other method currently available. When used intraoperatively, it provides invaluable data to aid in the anesthetic and surgical management of the patient, obviating the need for and potential risk of placing a Swan-Ganz pulmonary artery catheter before complete removal of the tumor thrombus.

Aged↗
PubMed1994

Transesophageal echocardiography assisted retrieval of embolized inferior vena cava stent.

A 32-year-old male with Budd-Chiari syndrome and stenosis of the inferior vena cava presented to the hospital with severe abdominal pain. Two contiguous, 14 mm, overlapping (joined) Palmaz stents were placed across the area of stenosis in the inferior vena cava. The stents later embolized to the left pulmonary artery and were retrieved non-surgically over a Grollman balloon catheter with transesophageal echocardiographic assistance. This case report highlights the advantages and limitations of transesophageal echocardiographic assistance in such a procedure.

Adult↗
PubMed1994

Discordance of dual-isotope (hybrid) myocardial perfusion imaging results in patients who have undergone revascularization procedures.

Three hundred twenty-one separate acquisition dual-isotope myocardial perfusion scans were reviewed retrospectively. Studies performed in six patients demonstrated a relative improvement in Tc-99m sestamibi uptake during stress in segments that appeared abnormal on rest injected Tl-201 images. All patients who demonstrated this pattern had a prior history of myocardial infarction and interventional revascularization. While many factors may contribute to this appearance, the authors favor the presence of a patent infarct-related artery as being the most significant.

Angioplasty, Balloon, Coronary↗
PubMed1993

The use of transesophageal echocardiography to avoid left atrial thrombus during percutaneous mitral valvuloplasty.

During mitral balloon valvuloplasty, transesophageal echocardiography (TEE) has been employed for the accurate placement of the transseptal needle, guide wires, and balloon catheters and to provide an immediate evaluation of the results of the procedure. We describe a case demonstrating that TEE can be used to avoid a left atrial appendage thrombus during the placement of wires and catheters. With TEE guidance, we feel left atrial appendage thrombi are no longer an absolute contraindication to percutaneous mitral valvuloplasty.

Aged↗
PubMed1993

Spontaneous calcific embolization to the supraclinoid internal carotid artery from a regurgitant bicuspid aortic valve.

Calcific brain embolization leading to stroke is rarely recognized. We report a case of spontaneous embolization to the right cerebral circulation from a severely regurgitant, calcified bicuspid valve. Bicuspid aortic valves constitute the most common congenital heart abnormality, and have a tendency to become stenosed, regurgitant, calcified, or infected. The presence of heavy calcification in a noninfected bicuspid valve may lead to dislodgement of calcific embolic material which is not necessarily heralded by acute valvular rupture. Accurate localization of the calcific embolus to the right supraclinoid internal carotid artery was provided by spiral CT imaging in this case.

Adult↗
PubMed1993

The diagnosis of a pulmonary artery thrombus by transesophageal echocardiography.

We describe a patient with an acute inferior wall myocardial infarction who underwent percutaneous coronary angioplasty. He subsequently had a cardiac arrest and developed progressive severe hypoxia. Although findings from pulmonary angiography were nondiagnostic, transesophageal echocardiography demonstrated a nonocclusive, right pulmonary artery thrombus. Therapy was changed, and the patient recovered. Transesophageal echocardiography was also used to monitor anticoagulation therapy.

Aged↗