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C Michael White

Publications and source records attributed to C Michael White.

At least 55 records · Page 3Linked to original sources
PubMed2004

An evaluation of postoperative P-wave variables after cardiothoracic surgery.

Postoperative atrial fibrillation is common after cardiac surgery. Prediction of which patients will develop postoperative atrial fibrillation would be clinically useful. Increased P-wave duration, suggesting atrial conduction delay and measured from preoperative electrocardiograms, predicts postoperative atrial fibrillation. However, postoperative P-wave duration has not been evaluated after cardiac surgery. In this study, we evaluated postoperative P-wave variables (maximum P-wave duration and P-wave dispersion) over 5 days in cardiac surgery patients receiving amiodarone, pacing or no atrial fibrillation prophylaxis. P-wave variables gradually shortened as time passed from surgery. Amiodarone did not shorten P-wave measurements throughout therapy, while pacing shortened P-waves in the immediate postoperative period; however, shortening was not sustained. P-waves did not differ between those who did and did not develop atrial fibrillation with amiodarone or pacing. Our findings suggest that atrial conduction delay resulting from cardiothoracic surgery tends to resolve over time and may not play a critical role in the etiology of postoperative atrial fibrillation.

Aged↗
PubMed2004

Inappropriate implantable cardioverter defibrillator discharge following consumption of a dietary weight loss supplement.

This report describes the clinical course of a 40-year-old female who experienced repetitive ICD firing after consuming Metabolife 356, a multicomponent dietary weight loss supplement. Following the initiation of Metabolife 356, the patient experienced four shocks over a 3 day period with two 30 J shocks being delivered sequentially. Interrogation of the device revealed atrial tachycardia with 1:1 AV conduction at a rate of 240 beats/min. Metabolife 356 was discontinued and the dosage of sotalol was increased to 120 mg twice daily without recurrence of ICD discharge.

Adult↗
PubMed2004

Economic analysis of intravenous plus oral amiodarone, atrial septal pacing, and both strategies to prevent atrial fibrillation after open heart surgery.

STUDY OBJECTIVES: To compare the cost-effectiveness of intravenous plus oral amiodarone, atrial septal pacing, and both strategies combined to prevent atrial fibrillation after open heart surgery. Secondary objectives were to compare the cost-effectiveness of amiodarone versus no amiodarone and of pacing versus no pacing, and to compare hospitalization costs of the various strategies. DESIGN: Piggyback cost analysis of a randomized, 2 x 2 factorial trial. SETTING: Urban academic hospital. PATIENTS: One hundred and sixty patients with coronary artery and/or valvular disease. INTERVENTION: Patients were randomized to receive amiodarone or matching placebo and then further randomized to receive atrial septal pacing or no pacing. MEASUREMENTS AND MAIN RESULTS: The economic analysis was conducted from a hospital perspective. Charges were converted to costs using cost:charge ratios. For the cost-effectiveness analysis, a joint distribution of costs and effectiveness was performed using the nonparametric bootstrap method. Amiodarone plus pacing significantly decreased the frequency of atrial fibrillation after open heart surgery, compared with amiodarone alone, pacing alone, and placebo. Total costs (mean+/-SD) were $27,026+/-30,226 for the placebo group, $22,725+/-17,661 for the amiodarone group, $33,868+/-60,309 for the pacing group, and $18,697+/-8174 for the amiodarone plus pacing group (p=0.27). In the joint distribution cost-effectiveness analysis, when compared with placebo, the probability of lower cost but higher effect (superiority) was 67% for amiodarone, 15% for pacing, and 97% for amiodarone plus pacing. In the multivariate analysis, preoperative beta-blockers and amiodarone were negatively associated with hospital costs (p<0.05). CONCLUSIONS: Data suggest that both amiodarone alone and the combination of amiodarone plus pacing are cost-effective compared with placebo. Additional comparative studies of these strategies are warranted to confirm these findings.

Administration, Oral↗
PubMed2004

Key articles and guidelines in pharmacotherapeutic management of arrhythmias.

Clinical studies are among the most important literature published in the area of cardiovascular pharmacotherapy and are the basis of many of the standards of practice today. We compiled a list of these clinical trials, as well as well-written, up-to-date review articles and important treatment guidelines, that focus on pharmacotherapeutic management of arrhythmias. This list should be useful not only to practitioners and trainees in cardiovascular pharmacotherapy, but also to other clinicians as an update.

Anti-Arrhythmia Agents↗
PubMed2004

Anemia management in heart failure: a thick review of thin data.

Heart failure is defined as the inability of the heart to pump blood at an amount sufficient to meet the metabolic needs of the body. In heart failure, the inability to meet the body's metabolic needs is based on hemodynamic derangement and suboptimal oxygen-carrying capacity of the blood itself. Current pharmacologic therapy attempts to improve survival and reduce symptomatology by optimizing hemodynamics to increase oxygen delivery, but does not address oxygen-carrying capacity. Unfortunately, there is a high prevalence of anemia in patients with heart failure, which compromises oxygen-carrying capacity, is an independent predictor of mortality, and may be caused in part by pharmacologic agents that confer morbidity and mortality benefits in this population. Recombinant human erythropoietin supplementation improves the functional capacity of the failing myocardium, reverses and antagonizes the detrimental remodeling induced by autoimmune activity, and may reduce mortality and morbidity among patients receiving maximal pharmacologic therapy for heart failure. However, limited clinical data prohibit widespread recommendations for its use in patients with heart failure.

Anemia↗
PubMed2004

Cost effectiveness of ibutilide with prophylactic magnesium in the treatment of atrial fibrillation.

BACKGROUND: In the Treatment with Ibutilide and Magnesium Evaluation (TIME) study, a retrospective multicentre cohort trial, prophylactic magnesium was found to improve the antiarrhythmic efficacy of ibutilide as demonstrated by an increase in the rate of successful chemical conversion and reduction in the need for direct current cardioversion (DCC). OBJECTIVE: The primary objective of this piggyback cost-effectiveness analysis of the TIME study was to compare the cost per successful conversion of atrial fibrillation (AF) for ibutilide in the presence and absence of magnesium prophylaxis. A secondary objective was to determine whether specific factors predict costs in the conversion of AF. METHOD: The study was conducted from the US hospital-payer perspective. Direct medical costs (USD, 2002 values) including drugs, intravenous admixture and administration, DCC, electrocardiographs and physicians' fees were obtained directly from the provider. Nonparametric bootstrapping was conducted to calculate confidence intervals for the incremental cost-effectiveness ratios. One-way sensitivity analysis was conducted varying efficacy, and drug, hospital and physician costs. Multivariate analysis was conducted to determine whether specific baseline factors were predictors of total cost. RESULTS: Total costs per patient were lower in the ibutilide plus magnesium group compared with ibutilide alone (USD1075 vs USD1201); however, the difference was not statistically significant (p = 0.116). Patients receiving ibutilide plus magnesium had lower DCC costs compared with those receiving ibutilide alone (USD261 vs USD399; p = 0.036), but higher magnesium-associated costs (USD0.50 vs USD0; p < 0.001). Bootstrapping revealed that the ibutilide plus magnesium strategy would result in lower costs and greater efficacy 93.4% of the time. These results remained robust to changes in both cost and efficacy. No baseline factors were found to be independent predictors of total costs. CONCLUSION: Our data suggest that adding prophylactic magnesium to ibutilide may be cost effective, from a US hospital-payer perspective, for the acute conversion of patients in AF or flutter compared with ibutilide alone.

Aged↗
PubMed2004

Hawthorn.

Explore the source record for details and available documents.

Cardiovascular Diseases↗
PubMed2003

Impact of prophylactic i.v. magnesium on the efficacy of ibutilide for conversion of atrial fibrillation or flutter.

The impact of prophylactic i.v. magnesium on the efficacy of ibutilide for conversion of atrial fibrillation and flutter to normal sinus rhythm was studied. In this multicenter cohort study, all patients in three large, tertiary care centers who received ibutilide for acute chemical conversion of atrial fibrillation or flutter from August 1996 through December 2001 were identified through pharmacy or billing records. Patients who did not receive magnesium before or during ibutilide therapy served as the control group, while those who received magnesium less than two hours before or during ibutilide administration served as the study group. The rate of administration of direct-current cardioversion (DCC) and the occurrence of ventricular arrhythmia were compared between those who did and did not receive magnesium. The rates of successful cardioversion were also assessed. Categorical data were analyzed using chi-square analysis or Fisher's exact test. Demographic data were analyzed using Student's t test. The medical records of 321 patients were analyzed. Successful chemical cardioversion in the study group was approximately 19% higher than in those who did not receive magnesium (p = 0.040). The use of DCC in the group who received magnesium was reduced by approximately 34% (p = 0.045). The conversion rate of atrial fibrillation or flutter with ibutilide was enhanced by magnesium administration (p = 0.040), and the rate of administration of DCC was reduced (p = 0.045) in patients who received magnesium. There was a nonsignificant reduction in the occurrence of ventricular arrhythmias (p = 0.533). The efficacy of ibutilide was enhanced by concomitant administration with intravenous magnesium.

Aged↗
PubMed2003

Acute beta-blockade reduces the extent and severity of myocardial perfusion defects with dipyridamole Tc-99m sestamibi SPECT imaging.

OBJECTIVES: The goal of this study was to examine the effect of acute beta-blockade on dipyridamole Tc-99m sestamibi myocardial perfusion imaging (DMPI). BACKGROUND: Studies suggest that antianginal drugs may reduce the presence and severity of myocardial perfusion defects with dipyridamole stress. However, there are no data regarding specific drugs. METHODS: Patients with catheterization-proven coronary artery disease (CAD) were enrolled in this prospective, double-blind, placebo-controlled study and randomly assigned to DMPI after placebo, low-dose metoprolol (up to 10 mg), and high-dose metoprolol (up to 20 mg). Patients underwent one Tc-99m sestamibi study at rest on a separate day. The interval between DMPI studies was <or=14 days. Images were interpreted by three observers blinded to clinical data using a 17-segment, five-point model. For each image, a summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) were calculated (SDS = SSS - SRS). Images with an SSS <4 were considered normal. RESULTS: Twenty-one patients completed all four Tc-99m sestamibi studies. The sensitivity of DMPI for detection of CAD was 85.7% with placebo versus 71.4% with low- and high-dose metoprolol. In comparison with placebo, the SSS was significantly lower (p < 0.05) with low- and high-dose metoprolol (12.0 +/- 10.1 vs. 8.7 +/- 9.0 and 9.3 +/- 10.6, respectively). The SDS also was significantly lower (8.4 +/- 8.8 with placebo vs. 5.0 +/- 6.7 [p < 0.001] and 5.4 +/- 7.9 [p < 0.01] with low- and high-dose metoprolol, respectively). CONCLUSIONS: The presence and severity of CAD may be underestimated in patients receiving beta-blocker therapy undergoing dipyridamole stress myocardial perfusion imaging.

Adrenergic beta-Antagonists↗
PubMed2003

Intravenous plus oral amiodarone, atrial septal pacing, or both strategies to prevent post-cardiothoracic surgery atrial fibrillation: the Atrial Fibrillation Suppression Trial II (AFIST II).

BACKGROUND: The effect of a hybrid intravenous and oral prophylactic amiodarone regimen on postcardiothoracic surgery (CTS) atrial fibrillation (AF) is unknown. The impact of active atrial septal pacing on post-CTS AF has not been well characterized. In addition, the effect of using both amiodarone and atrial septal pacing together to prevent atrial fibrillation is unknown. METHODS AND RESULTS: Patients (n=160) were randomized to amiodarone or placebo and then to pacing or no pacing using a 2x2 factorial design. All therapies began within 6 hours post-CTS. Amiodarone was given by intravenous infusion for the first 24 hours (1050 mg total) followed by oral therapy for 4 postoperative days (4800 mg total). Atrial septal pacing was given for 96 hours. Amiodarone reduced the risk of AF by 43% and the risk of symptomatic AF by 68% (P=0.037 and P=0.019) versus placebo. Atrial septal pacing did not reduce AF or symptomatic AF incidence versus no pacing. The risk of post-CTS AF in the patients receiving amiodarone+pacing was lower than the placebo+no pacing and the placebo+pacing groups (57.9% and 60.5% reductions, P=0.047 and P=0.040, respectively). CONCLUSIONS: Amiodarone given as both an intravenous and oral regimen is effective at reducing post-CTS AF but atrial septal pacing is ineffective. Combining amiodarone and pacing is better than placebo with or without pacing but not amiodarone alone.

Administration, Oral↗
PubMed2003

Biological variation for N-terminal pro- and B-type natriuretic peptides and implications for therapeutic monitoring of patients with congestive heart failure.

Given the limitations of low enrollments, this study suggests that a change of 130% for B-type natiuretic peptide (BNP) and 90% for N-terminal (NT)-proBNP are necessary before results of serially collected data can be considered statistically different. This study also shows that there are important differences in the performance of BNP versus NT-proBNP in monitoring patients with congestive heart failure that need to be further explored.

Adult↗
PubMed2003

Amiodarone prevents symptomatic atrial fibrillation and reduces the risk of cerebrovascular accidents and ventricular tachycardia after open heart surgery: results of the Atrial Fibrillation Suppression Trial (AFIST).

BACKGROUND: Atrial fibrillation (AF) is a common complication after cardiothoracic surgery (CTS). The role of amiodarone added to beta blocker as a preventive strategy in elderly patients undergoing CTS is not known. The Atrial Fibrillation Suppression Trial (AFIST) was a double blind, placebo-controlled trial that evaluated the efficacy of oral amiodarone in patients 60 years or older undergoing CTS. Beta blockers were administered as part of a critical pathway. METHODS: Elderly patients (n = 220, mean age 72 +/- 6.7 years) received amiodarone (n = 120) or placebo (n = 100). Patients enrolled less than 5 days before CTS received 6 g of drug over 6 days beginning on the day prior to OHS. Patients enrolled 5 days before CTS received 7 g of study drug over 9-10 days, starting on preoperative day 4 or 5. RESULTS: Amiodarone treated patients had a lower incidence of AF (22.5% vs. 38%, p = 0.01), symptomatic AF (4.2% vs. 18%, p = 0.001), cerebral vascular accident (1.7 vs. 7.0%, p = 0.04), and ventricular tachycardia (1.7% vs. 7.0%, p = 0.04) vs. placebo. Beta blocker use (87.5% vs. 91.0% ), nausea (26.7% vs. 16%, p = 0.056), symptomatic bradycardia (7.5% vs. 7%, p = 0.89), hypotension (14.2% vs. 10.0%) and 30 day mortality (3.3 vs. 4.0%, p = 0.79) were similar. Amiodarone treated patients receiving the 4/5 day preoperative regimen had a reduced incidence of AF (19.6% vs. 38%, p = 0.013), while those receiving the 1-day preoperative regimen showed a trend (25% vs. 38%, p = 0.06) vs. placebo. CONCLUSIONS: In an elderly population undergoing CTS, Amiodarone prophylaxis reduces AF, the incidence of symptomatic AF, cerebrovascular accident and ventricular tachycardia.

Administration, Oral↗
PubMed2003

Levosimendan: implications for clinicians.

Levosimendan is a novel calcium sensitizing agent in development for the treatment of acute and chronic heart failure. The agent increases myocardial force without increasing myocyte calcium concentrations, thus reducing the possibility for myocardial necrosis. In addition, the agent also causes vasodilation of coronary and peripheral vessels to improve coronary blood flow and reduce afterload. The short half-life is a benefit for intravenous administration but could be problematic for the drug's use in chronic heart failure. The risk of the development of arrhythmias from levosimendan appears small secondary to an increase in the QTc interval of 15 msec but needs to be evaluated in light of the ability of levosimendan to open adenosine triphosphate (ATP)-sensitive potassium channels. In addition, the agent has not been studied in patients with additional risks for torsades de pointes. Levosimendan has been shown to have beneficial survival effects in several populations; its use improves patient outcomes relative to the standard of care and has the potential to reduce hospital costs associated with heart failure.

Calcium↗
PubMed2003

Hemodynamic and electrocardiographic effects of short-term Ginkgo biloba.

OBJECTIVE: To evaluate the immediate and short-term hemodynamic and electrocardiographic effects of Ginkgo biloba (ginkgo). METHODS: Healthy volunteers were randomized to receive ginkgo 120 mg or placebo twice daily for 7 days in this prospective, double blind trial. After at least a 7-day washout period, subjects were crossed over to an additional 7 days of alternate therapy. Blood pressure, heart rate, and 12-lead electrocardiograms were evaluated immediately before (baseline), and at 1, 3, and 5 hours after observed ingestion of study drug on days 1 and 7 of therapy. Electrocardiographic parameters (P wave and QRS complex duration; PR, QT, and QTc intervals) were measured in lead II by a blinded investigator. RESULTS: Ginkgo had no effect on any of the evaluated electrocardiographic parameters at any time point on days 1 or 7. Additionally, no changes in heart rate or systolic and diastolic blood pressure were found between the groups at any time point on any evaluative day. CONCLUSIONS: Commonly used doses of Ginkgo biloba do not have any immediate or short-term effects on blood pressure, heart rate, or electrocardiographic variables in young, healthy volunteers.

Adult↗
PubMed2003

Nicardipine to control neonatal hypertension during extracorporeal membrane oxygen support.

OBJECTIVE: To describe the clinical course of a newborn (gestational age 38 wk, 6 d) administered intravenous nicardipine to control hypertension while on extracorporeal membrane oxygen (ECMO) support. SETTING: Urban, university teaching hospital. CASE SUMMARY: A 1-day-old male neonate presenting with a left congenital diaphragmatic hernia developed a sustained elevation in blood pressure following a change of ECMO tubing. After several unsuccessful treatment regimens, nicardipine was started at a rate of 0.5 micro g/kg/min and aggressively titrated to 1.5 micro g/kg/min. Nicardipine produced a sustained antihypertensive effect that was noticed 8 hours after the start of the infusion. The infusion was continued through postoperative day 2. Following a second circuit change, nicardipine was discontinued and sodium nitroprusside therapy was started. Treatment with nitroprusside failed to lower the blood pressure. DISCUSSION: Nicardipine is an effective antihypertensive agent for neonates receiving ECMO therapy. However, the expanded volume of distribution caused by the ECMO circuit may result in a reduced serum concentration and a reduced antihypertensive effect. CONCLUSIONS: We recommend a conservative initial dose of nicardipine of 0.5 micro g/kg/min that is aggressively titrated to reduce blood pressure effectively in neonates receiving ECMO therapy.

Antihypertensive Agents↗
PubMed2003

A 24-hour comparison of serum growth hormone concentrations in patients with heart failure versus healthy controls.

STUDY OBJECTIVE: To compare endogenous serum growth hormone concentrations over a 24-hour period in patients with chronic heart failure (CHF) and matched controls. DESIGN: Prospective, 24-hour, endogenous concentration comparison. SETTING: Hospital research center. PATIENTS: Eight evaluable patients with nonischemic dilated cardiomyopathy and 10 healthy control subjects, matched for age and sex. INTERVENTION: Over a 24-hour period, blood was drawn from the study participants every 20 minutes for determination of growth hormone. MEASUREMENTS AND MAIN RESULTS: For each patient, the area under the concentration-time curve from time 0-24 hours (AUC0-24), maximum concentration (Cmax), and minimum concentration (Cnadir) of growth hormone were determined. The AUC0-24 and Cmax were 74% (p < 0.05) and 62% (p < 0.05) lower in patients with CHF than in controls, respectively. The Cnadir for all participants was 0 microg/L. Variability in growth hormone concentrations over the 24 hours was considerable for all study participants. CONCLUSIONS: Growth hormone concentrations are suppressed over a 24-hour period in patients with CHF versus healthy controls. Variability in levels throughout the day suggests that a single point evaluation cannot be used to determine deficiency or abundance of growth hormone.

Adult↗