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Biomedical subjects

Andrew J Burger

Publications and source records attributed to Andrew J Burger.

At least 19 recordsLinked to original sources
PubMed2004

Elevated blood urea nitrogen level as a predictor of mortality in patients admitted for decompensated heart failure.

BACKGROUND: Hospitalization for decompensated heart failure is associated with high mortality after discharge. In heart failure, renal function involves both cardiovascular and hemodynamic properties. We studied the relation between renal dysfunction and mortality in patients admitted for decompensated heart failure. METHODS: The prognostic importance of four measures of renal function-blood urea nitrogen, serum creatinine, blood urea nitrogen/creatinine ratio, and estimated creatinine clearance-was evaluated in 541 patients (mean [+/- SD] age, 63 +/- 14 years; 377 men [70%]) with a previous diagnosis of heart failure (96% with New York Heart Association class III or IV symptoms) who were admitted for clinical decompensation. RESULTS: During a mean follow-up of 343 +/- 185 days, 177 patients (33%) died. In multivariable Cox regression models, the risk of all-cause mortality increased with each quartile of blood urea nitrogen, with an adjusted relative risk of 2.3 in patients in the upper compared with the lower quartiles (95% confidence interval [CI]: 1.3 to 4.1; P = 0.005). Creatinine and estimated creatinine clearance were not significant predictors of mortality after adjustment for other covariates. Blood urea nitrogen/creatinine ratio yielded similar prognostic information as blood urea nitrogen (adjusted relative risk = 2.3; 95% CI: 1.4 to 3.8; P = 0.0007 for patients in the upper compared with the lower quartiles). CONCLUSION: Blood urea nitrogen is a simple clinical variable that provides useful prognostic information in patients admitted for decompensated heart failure. In this setting, elevated blood urea nitrogen levels probably reflect the cumulative effects of hemodynamic and neurohormonal alterations that result in renal hypoperfusion.

Aged↗
PubMed2004

Relation between pulse pressure and survival in patients with decompensated heart failure.

Elevated pulse pressure (PP), an indicator of increased arterial stiffness, has been shown to predict adverse outcome in patients with stable heart failure. However, the dependence of PP on hemodynamic factors, such as stroke volume and peak aortic blood flow, suggests that the relation between PP and outcome may depend on the clinical setting. We evaluated the relation between PP and all-cause mortality in 489 patients with decompensated heart failure. We found that the association of PP with outcome in this setting is reversed, with low PP being an independent predictor of mortality.

Adult↗
PubMed2004

Measures of heart period variability as predictors of mortality in hospitalized patients with decompensated congestive heart failure.

Depressed heart rate variability (HRV) is a powerful independent predictor of a poor outcome in patients with chronic and stable congestive heart failure (CHF). However, the prognostic value of HRV analysis in patients hospitalized for decompensated CHF is not known. The aim of this study was to investigate whether HRV parameters obtained during admission for decompensated CHF could predict survival after hospital discharge. We studied 199 patients (131 men, aged 60 +/- 14 years) with a previous diagnosis of New York Heart Association class III or IV CHF who were admitted to the hospital for decompensated CHF. Twenty-four-hour Holter recordings were obtained on admission, and measures of HRV were calculated in the time and frequency domain. During a mean follow-up of 312 +/- 150 days, 40 patients (21.1%) died. Kaplan-Meier analysis indicated that patients with SD of the RR intervals over a 24-hour period (p = 0.027), SD of all 5-minute mean RR intervals (p = 0.043), total power (p = 0.022), and ultra-low-frequency power (p = 0.008) in the lower tertile were at a higher risk of death. In a multivariate Cox regression model, the same indexes in the lower tertile were independent predictors of mortality: SD of the RR intervals over a 24-hour period (risk ratio [RR] 2.2, 95% confidence interval [CI] 1.05 to 4.3, p = 0.036), SD of all 5-minute mean RR intervals (RR 2.1, 95% CI 1.05 to 4.2, p = 0.04), total power (RR 2.2, 95% CI 1.08 to 4.2, p = 0.03), and ultra-low-frequency power (RR 2.6, 95% CI 1.3 to 5.3, p = 0.007). Therefore, the severity of autonomic perturbations during hospital admission for CHF decompensation, as reflected by measures of overall HRV, can predict survival after hospital discharge. Together with previous studies, our findings suggest that indexes of overall HRV provide useful prognostic information in the full spectrum of CHF severity.

Arrhythmias, Cardiac↗
PubMed2004

Improved glycemic control induces regression of left ventricular mass in patients with type 1 diabetes mellitus.

BACKGROUND: Diabetes mellitus has been associated with abnormalities of cardiac function and left ventricular hypertrophy. We sought to determine whether improved glycemic control in patients with type 1 diabetes mellitus will induce reversal of those abnormalities. METHODS: We prospectively studied 19 patients (mean age 40+/-9 years) with longstanding type 1 diabetes mellitus (28+/-4 years), who participated in a program of stringent glycemic control. Glycemic control was monitored with hemoglobin A1c levels, and improvement was defined as >1% (absolute) decrease of hemoglobin A1c. Two-dimensional and Doppler echocardiograms and ambulatory 24-h blood pressures were obtained at baseline and after 1 year. Left ventricular mass was determined using the area-length method. RESULTS: In the patients with improved glycemic control (n=12), hemoglobin A1c decreased from 9.8% to 7.8% (p< or =0.0001), interventricular septal thickness decreased from 10.3 to 9.4 mm (p< or =0.05), and left ventricular mass regressed from 205 to 182 g (p< or =0.05). Septal thickness and left ventricular mass remained unchanged in the patients who did not achieve improvement of glycemic control. Left ventricular internal diameters, posterior wall thickness, fractional shortening, E/A ratio of mitral inflow, E-wave deceleration time (DT), and ambulatory 24-h blood pressures did not change significantly after 1 year in either group. CONCLUSIONS: Improved glycemic control in patients with type 1 diabetes mellitus is associated with regression of septal thickness and left ventricular mass without significant effect on systolic or diastolic function, in the absence of significant alterations in ambulatory 24-h blood pressures.

Adult↗
PubMed2003

Neurohumoral activation and ventricular arrhythmias in patients with decompensated congestive heart failure: role of endothelin.

Patients with congestive heart failure (CHF) have a high incidence of ventricular arrhythmias and sudden arrhythmic death. CHF entails profound and complex abnormalities in humoral responses that are thought to promote arrhythmic events. However, it is unknown which of the many endogenous mediators that accumulate as part of neurohormonal activation is important in arrhythmogenesis in the setting of CHF. The study included 83 patients admitted to the hospital for treatment of decompensated CHF. Neurohormonal and cytokine activation was assessed by measuring plasma renin activity, aldosterone, norepinephrine, endothelin-1, tumor necrosis factor-alpha, and interleukin-6 levels. Atrial and ventricular arrhythmic events were assessed by 24-hour Holter monitoring. In a univariate analysis, a highly significant, positive relationship was found between plasma endothelin-1 levels and the average hourly total premature ventricular beats (P = 0.003), the frequency of ventricular pairs (P = 0.0003), and the frequency of ventricular tachycardia episodes (P = 0.001). After inclusion of clinical variables, drug therapies, neurohormones, and cytokine levels in a multivariate analysis, the positive relationship between plasma endothelin-1 level and the average hourly total premature ventricular beats (P = 0.008), the frequency of ventricular pairs (P = 0.007), and ventricular tachycardia episodes (P = 0.009) remained independent. No association between other neurohormones or cytokines and arrhythmic events was demonstrated. The results of the present study suggest that increased endothelin-1 concentrations may be involved in promoting the occurrence of ventricular ectopy in patients with decompensated CHF. Proarrhythmic effects may account, in part, for the poor outcome associated with increased endothelin-1 levels in patients with decompensated CHF.

Arrhythmias, Cardiac↗
PubMed2003

Effects of sulfonylurea hypoglycemic agents and adenosine triphosphate dependent potassium channel antagonists on ventricular arrhythmias in patients with decompensated heart failure.

Hypoglycemic sulfonylureas block cardiac ATP-sensitive potassium channels (K(ATP)). The opening of these channels in cardiomyocytes can induce arrhythmias. In animal studies, sulfonylureas exert an antiarrhythmic effect on the ischemic myocardium, but data on human arrhythmic events are lacking. The study population included 207 patients (age 61 +/- 14 years) admitted for decompensated CHF. The severity of ventricular arrhythmias was assessed by 24-hour Holter monitoring. None of the patients were on parenteral vasoactive therapy or antiarrhythmics during Holter recording. Diabetic patients comprised 48% of the study population, and 34% of diabetic patients were prescribed sulfonylureas. The mean hourly ventricular pairs (3.6 +/- 0.5 vs 1.8 +/- 0.3, P = 0.03), the mean hourly repetitive ventricular beats (5.7 +/- 1.0 vs 2.6 +/- 0.1, P = 0.03), and the frequency of ventricular tachycardia episodes per 24 hours (4.7 +/- 0.8 vs 2.2 +/- 0.4, P = 0.03) were significantly lower in patients with diabetes who were receiving sulfonylureas compared with nondiabetics. No significant difference occurred between patients with diabetes who were not receiving sulfonylureas and nondiabetic patients. Multivariate regression revealed a negative independent relationship between sulfonylurea therapy and hourly ventricular pairs (P = 0.03), the mean hourly repetitive ventricular beats (P = 0.03), and ventricular tachycardia episodes (P = 0.04). In a multiple logistic regression, sulfonylurea therapy was a negative predictor of repetitive ventricular beats (P = 0.01, adjusted OR, 0.31; 95% CI, 0.12-0.78). Concomitant sulfonylurea therapy may reduce the occurrence of complex ventricular ectopy in the setting of severe CHF. These results suggest that cardiac K(ATP) channel activation may be involved in the genesis of ventricular arrhythmias in CHF.

Aged↗
PubMed2002

Marked abnormalities in heart rate variability are associated with progressive deterioration of renal function in type I diabetic patients with overt nephropathy.

BACKGROUND: Cardiac autonomic neuropathy is a common complication of long-standing, type 1 diabetes and is associated with increased morbidity and mortality. Impaired heart rate variability is a sensitive and reproducible marker of cardiac autonomic neuropathy. We sought to examine the relationship between cardiac autonomic neuropathy as assessed by heart rate variability and overt nephropathy, with emphasis on the progression of renal dysfunction over 1 year. METHOD: Baseline and 12 month clinical and biochemical characteristics, as well as autonomic function tests, were analyzed in 23, type 1 diabetic patients (mean age 37+/-10 years, 65% males), who were prospectively enrolled as a part of a multi-center investigation. In addition, ambulatory, 24-h, 3-channel electrocardiograms were recorded, and heart rate variability indices were assessed in the time and frequency domains over the same period. RESULTS: All heart rate variability indices were markedly decreased in our study population. On univariate analysis, heart rate variability was associated with creatinine clearance, and to a lesser extent, mean 24-h blood pressures and cholesterol. On multivariate analysis, only heart rate variability was a significant and independent predictor of abnormalities in creatinine clearance. Severe reduction in heart rate variability at baseline was also significantly associated with the further deterioration in renal function at 1 year. CONCLUSION: Heart rate variability is significantly reduced in long-standing, type 1 diabetics with proteinuria or overt nephropathy. Marked abnormalities in heart rate variability are significantly associated with and predictive of progressive renal deterioration at 1 year. These findings may have implications for aggressive medical intervention to improve prognosis and survival in this population.

Adult↗
PubMed2002

The effect of sex on ventricular arrhythmic events in patients with congestive heart failure.

The propensity to develop specific arrhythmias varies between the sexes. Patients with congestive heart failure (CHF) have a high prevalence of ventricular ectopy. However, it is not known if sex related differences exist in the susceptibility to arrhythmias in the setting of CHF. The study population included 159 men and 77 women (mean age 61 +/- 14 years) admitted for decompensated CHF. The severity of atrial and ventricular arrhythmias was assessed by 24-hour Holter monitoring. None of the patients were on parenteral vasoactive therapy during Holter recording. All measures of ventricular ectopy were markedly lower in women compared to men. The mean hourly ventricular pairs (283 +/- 67 vs 106 +/- 30, P = 0.04), mean hourly repetitive ventricular beats (28 +/- 7 vs 10 +/- 3, P = 0.04), and the frequency of ventricular tachycardia episodes per 24 hours (31 +/- 9 vs 7 +/- 3, P = 0.01) were significantly lower in women. After inclusion of clinical variables and drug therapies in a multivariate analysis, the negative relationship between female sex and the frequency of ventricular pairs (P = 0.04), repetitive ventricular beats (P = 0.04), and ventricular tachycardia episodes (P = 0.0005) remained independent. No differences in atrial ectopy between men and woman were found. Complex ventricular ectopy and episodes of ventricular tachycardia are significantly lower in women with CHF. Whether these finding are relevant to female survival advantage in the setting of heartfailure can only be determined by a prospective study. Further understanding of the mechanisms involved in the protection conferred by the patient's sex would advance our understanding about arrhythmias in heart failure.

Adult↗
PubMed2002

False positive ST segment elevation during dobutamine stress echocardiography due to left ventricular hypertrophy.

The significance of ST segment elevation in dobutamine stress echocardiography (DSE) remains controversial. In patients with prior Q wave myocardial infarction (MI), it may reflect myocardial ischemia, contractile reserve in the infarct-related area, or dyskinesia of the infarcted areas of myocardium. In the nonpost-MI population, it has been attributed to vasospasm or strongly associated with coronary artery disease and ischemia. We hypothesized that ST segment elevation in the absence of inducible ischemia or prior MI is related to the presence of left ventricular hypertrophy (LVH). During DSE, dobutamine was infused from 5 microg/kg/min up to a maximum of 50 microg/kg/min. Echocardiographic images were obtained at baseline, low dose, peak dose, and recovery. Ischemia was defined as either the development of a new wall-motion abnormality or worsening wall motion at peak dose. We reviewed 682 consecutive DSE tests and found ST elevation in 42 patients (incidence = 6.1%). After excluding two patients for > 10% uninterpretable echocardiographic segments, the study population consisted of 40 patients. In 25 patients with ST elevation and without echocardiographic evidence for dobutamine-induced ischemia, 21 (84%) patients had LVH (P = 0.001). In 15 patients with inducible ischemia, only 4 (27%) patients had LVH. No other significant differences were found except that prior MI was more common in the inducible ischemia group. In the subgroup of 18 patients without prior MI, no inducible ischemia was found in 15 (83%). LVH was present in 14 (93%) of these 15 patients (P < 0.005), and all 14 had a normal baseline left ventricular ejection fraction. None of the three patients in the nonpost-MI subgroup with inducible ischemia had LVH. The 22 patients with prior MI had no significant association with LVH (P = 0.39). We conclude that ST segment elevation during DSE can occur without echocardiographic evidence for ischemia and is associated with LVH in the nonpost-MI population. This ST elevation may be related to transient electrocardiographic repolarization changes in the hypertrophied ventricle in the presence of altered loading conditions and/or altered catecholamine influences rather than true ischemia.

Adrenergic beta-Agonists↗
PubMed2002

Concomitant beta-blocker therapy is associated with a lower occurrence of ventricular arrhythmias in patients with decompensated heart failure.

BACKGROUND: Ventricular arrhythmias are nearly universally present in patients with advanced congestive heart failure (CHF) and represent an important cause of mortality in these patients. One of the putative mechanisms for the salutary effects of beta-blockers on sudden death mortality in heart failure is their ability to suppress ventricular arrhythmias. However, supporting data in patients with CHF are sparse, especially in the setting of excessive neurohumoral activation associated with symptomatic decompensated heart failure. METHODS AND RESULTS: We studied 236 patients (159 men; mean age, 61 +/- 14 years) admitted for decompensated CHF. Fifty patients were receiving beta-blockers at the time of the study. The severity of ventricular arrhythmia was assessed by 24-hour Holter recordings by using several prospectively defined measures of ventricular ectopy. All measures of ventricular ectopy were lower in patients receiving beta-blockers. The average hourly total premature ventricular beats (PVCs), hourly ventricular couplets, repetitive PVCs, and frequency of ventricular tachycardia episodes were 15% (P =.02), 75% (P <.05), 72% (P <.05), and 87% (P =.01) lower in patient receiving beta-blockers, respectively. In a multivariate regression analysis, the negative relationship between beta-blockers and the average hourly PVCs (P =.03), the frequency of ventricular pairs (P =.03), repetitive PVCs (P <.05), and ventricular tachycardia episodes (P =.01) remained significant and independent. CONCLUSIONS: Concomitant beta-blocker therapy during heart failure decompensation is associated with a marked reduction in complex ventricular ectopy and episodes of ventricular tachycardia. This effect of beta-blockers may play an important protective role by preventing serious ventricular arrhythmias during transient increases in sympathetic activity.

Adrenergic beta-Antagonists↗
PubMed2002

Effect of nesiritide (B-type natriuretic peptide) and dobutamine on ventricular arrhythmias in the treatment of patients with acutely decompensated congestive heart failure: the PRECEDENT study.

BACKGROUND: Dobutamine is commonly used as a means of treating decompensated congestive heart failure (CHF). Although typically effective at improving short-term hemodynamics and symptomatology, the frequent occurrence of arrhythmias and tachycardia is undesirable. In this randomized, multicenter trial, we compared the safety and clinical effectiveness of the cardiac hormone nesiritide (human B-type natriuretic peptide) with dobutamine in hospitalized patients with decompensated CHF. METHODS: The study population consisted of 255 patients who were randomized to 1 of 2 doses of intravenous nesiritide (0.015 or 0.03 microg/kg/min) or dobutamine (> or =5 microg/kg/min) and stratified by means of an earlier history of ventricular tachycardia. Patients were also assessed with 24 hour Holter recordings immediately before and during study drug therapy and by means of signs and symptoms of CHF. RESULTS: Dobutamine significantly increased the mean (1) number of ventricular tachycardia events per 24 hours by 48 +/- 205 (P =.001), (2) repetitive ventricular beats per hour by 15 +/- 53 (P =.001), (3) premature ventricular beats per hour by 69 +/- 214 (P =.006), and (4) heart rate by 5.1 +/- 7.7 beats per minute (P <.001). These end points were significantly decreased or unchanged in the nesiritide groups. Nesiritide did not increase heart rate, despite a greater reduction of blood pressure. Both drugs were similarly effective means of improving signs and symptoms of CHF. CONCLUSIONS: Dobutamine is associated with substantial proarrhythmic and chronotropic effects in patients with decompensated CHF, whereas nesiritide actually reduces ventricular ectopy or has a neutral effect. Compared with dobutamine, nesiritide may be a safer, short-term treatment for patients with decompensated CHF.

Aged↗
PubMed2002

Age and sex as determinants of ventricular arrhythmic events in patients with decompensated congestive heart failure.

BACKGROUND: The propensity to develop specific arrhythmias varies between the sexes and is influenced by age. Patients with congestive heart failure (CHF) have a high prevalence of ventricular ectopy. However, in the setting of CHF, it is not known whether sex-related or age-dependent differences exist in the susceptibility to arrhythmias. METHODS: The study population included 134 men and 73 women (mean age 61 +/- 14 years) admitted for decompensated CHF. The severity of ventricular arrhythmias was assessed by 24-hour Holter monitoring. None of the patients were on parenteral vasoactive therapy during Holter recording. RESULTS: All measures of ventricular ectopy were markedly lower in women. The average hourly premature ventricular contractions (PVCs), the frequency of ventricular pairs, the mean hourly repetitive ventricular beats, and the frequency of ventricular tachycardia episodes per 24 hours were 40%, 62%, 65%, and 78% lower in women, respectively. Multivariate logistic regression revealed that the risk of developing > 3 ventricular pairs per 24-hour period (OR = 2.2, CI = 1.1-4.2, P = 0.03), > 3 repetitive ventricular beats/hour (OR = 2.5, CI = 1.2-5.3, P = 0.01), or an episode of ventricular tachycardia (OR = 2.1, CI = 1.2-3.9, P = 0.01) were significantly higher in men. Patients in the higher tertile age group had a higher risk for the presence of > 3 ventricular pairs per 24-hour period (OR = 2.3, CI = 1.1-4.2, P = 0.03), and the presence of > 3 repetitive ventricular beats per hour (OR = 5.9, CI = 2.7-13.3, P < 0.0001), compared with patients in the lower age tertile. CONCLUSION: Male sex and age are associated with complex ventricular ectopy in patients with CHF. Further understanding of the mechanisms involved in the relative protection conferred by female sex would advance our understanding about arrhythmias in heart failure.

Age Distribution↗