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James J Bailey

Publications and source records attributed to James J Bailey.

5 recordsLinked to original sources
PubMed2004

The triangular wave test for electrocardiographic devices: a historical perspective.

Baseline wander makes interpretation ECG recordings difficult, especially the assessment of ST deviation. Eliminating baseline wander without distorting the ST segment is a problem. The traditional high pass filter with a 0.5 Hz low frequency cutoff effectively suppresses baseline but introduces considerable distortion in the level of the ST segment. This distortion results from phase nonlinearities that occur when frequency content and wave amplitude change abruptly, as occurs where the end of the QRS complex meets the ST segment. Since the 1980s nonlinear, digital filters have been designed that can increase the low frequency cutoff without the introduction of phase distortion. The triangular wave test, first described in the 1990 AHA Recommendations, is an objective method for measuring the ability to suppress baseline wander without affecting the ST segment. This methodology was adopted in 3 American National Standards.

Artifacts↗
PubMed2003

Risk stratification in diabetic patients with a previous myocardial infarction.

We used Kaplan-Meier 2-year survival analysis on CAST registry patients to estimate prognostic power of VPC frequency (> or =10/hr), presence of nonsustained ventricular tachycardia (NSVT), left ventricular ejection fraction, and presence of diabetes. We also used meta-analysis of reports in the literature to estimate prognostic power of signal-averaged electrocardiogram (SAECG) and electrophysiological tests (EPS) as well as VPCs, NSVT, and LVEF. Combined results from CAST analysis and literature meta-analysis yielded sensitivity and specificity for VPCs, NSVT, SAECG, LVEF, Diabetes, and EPS. The overall 2 year event rate for life-threatening arrhythmias or death was 7.88% for 51,144 cases in the combined CAST and literature data. After segmenting the population 21.3% were diabetic with a predicted 2 yr event rate of 13.5% and 78.7% were nondiabetic event rate of 6.4%. We defined low risk as <10% and high risk as > or =30%. Otherwise predicted event rate was classified as "unstratified." When all possible combination of noninvasive tests were applied, a prominent difference in the proportions of cases at risk between the diabetics and nondiabetics was revealed. When the unstratified cases were subsequently tested with EPS, the difference between the two groups was even more marked.

Cardiac Complexes, Premature↗
PubMed2002

Simultaneous heart rate and blood pressure variability analysis. Insight into mechanisms underlying neurally mediated cardiac syncope in children.

OBJECTIVES: The purpose of our investigation was to examine serial changes in autonomic nervous system activity along with measurements of hemodynamics and cardiac contractility, in assessing the mechanism(s) that underlie neurally mediated cardiac syncope (NMCS) in children. BACKGROUND: Previous research that used heart rate variability analysis alone to understand changes in autonomic activity that result in NMCS has provided conflicting results. We performed simultaneous heart rate and blood pressure variability analyses to characterize dynamic alterations in sympathetic and vagal tone during tilt-table testing in 23 children with a history of syncope or frequent dizziness. METHODS: Power spectra of heart rate and blood pressure variability were analyzed using autoregressive modeling. Maximum dP/dT of systolic blood pressure and the electrical-mechanical activation time were used to assess cardiac contractility. RESULTS: Tilt-table testing was positive in 12 children and negative in 11. Syncope was associated with decreased heart rate, blood pressure and low-frequency (LF) power. Before episodes of syncope, systolic blood pressure dP/dT decreased, and the electrical-mechanical activation time was prolonged. The decrease in blood pressure LF power exceeded and occurred before the decrease in heart rate LF power. Despite similar early increases in LF power to the initial stress of upright tilting, no significant decline in LF power (heart rate or blood pressure) was observed during negative tilt-table tests. CONCLUSIONS: All of these changes considered in total provide evidence supporting the hypothesis of sympathetic withdrawal/failure, resulting in a decrease in peripheral vascular tone and cardiac contractility, which results in profound hypotension in children with NMCS.

Adolescent↗
PubMed2002

Risk stratification applied to CAST registry data: combining 9 predictors. Cardiac Arrhythmia Suppression Trial.

Over 200,000 people in the United States die of sudden cardiac death (SCD) every year. Although many of these deaths occur in asymptomatic individuals, the vast majority of deaths occur in people who are under care for existing coronary heart disease. Implantable cardioverter/defibrillators (ICDs) have been shown in several randomized trials to be effective in prolonging lives of those at high risk for sudden cardiac death, but the criteria used in these trials and the ACC/AHA consensus guidelines would cover only a minority of patients. Developing methods to assign risk to individual patients without prior SCD events could promote the use of this life-saving therapy in those with especially high risk. Given sufficient physiologically relevant measurements from electrocardiogram analysis, clinical assessment, and demographic status, multivariate statistical methods for predicting survival can be used to combine many predictors of risk and calculate the risk for an individual patient. A survival analysis using Cox regression on data from the Cardiac Arrhythmia Suppression Trial (CAST) illustrates this concept. Patient age, sex, ejection fraction, smoking history, and prior myocardial infarction history, along with the frequency of premature beats and the presence of runs of ventricular tachycardia on Holter monitoring and the time from the index myocardial infarction to the baseline Holter and to recruitment into CAST were combined in a multivariate predictor derived from the Cox regression; this predictor significantly outperforms the individual predictors. A proposed test based on this predictor would identify as positive 7% of the CAST registry, with an average risk of death among the positives of 47%; 20% of those dead at 2 years would be positive. With improved component measurements, this approach has the potential for significantly improving risk stratification for the prevention of SCD.

Age Factors↗