Biomedical subjects

D O Martin

Publications and source records attributed to D O Martin.

7 recordsLinked to original sources

PubMed2005

Preimplantation B-type natriuretic peptide concentration is an independent predictor of future appropriate implantable defibrillator therapies.

OBJECTIVE: To assess prospectively whether preimplantation B-type natriuretic peptide (BNP) and C reactive protein (CRP) concentrations predict future appropriate therapies from an implantable cardioverter-defibrillator (ICD). DESIGN AND SETTING: Prospective cohort study conducted in a tertiary cardiac care centre. METHODS: 345 consecutive patients undergoing first time ICD implantation were prospectively studied. Serum BNP and CRP concentrations were obtained the day before ICD implantation. Patients were followed up with device interrogation to assess for appropriate shocks or antitachycardia pacing. Inappropriate therapies were excluded. Mean (SD) follow up was 13 (5) months. RESULTS: Patients had ischaemic (71%), primary dilated (17%), and valvar or other cardiomyopathies (12%). About half (52%) had ICDs implanted for primary prevention. Sixty three (18%) received appropriate ICD therapies. Serum creatinine, beta blocker, statin, and angiotensin converting enzyme inhibitor usage did not differ between therapy and no therapy groups. By univariate comparison, ejection fraction (p = 0.048), not taking amiodarone (p = 0.033), and BNP concentration (p = 0.0003) were risk factors for ICD therapy. However, by Cox regression multivariate analysis, only BNP above the 50th centile was a significant predictor (hazard ratio 2.19, 95% confidence interval 1.07 to 4.71, p = 0.040). Median BNP was 573 ng/l versus 243 ng/l in therapy and no therapy patients, respectively (p = 0.0003). More patients with BNP above the 50th centile (27% v 10%, p = 0.006) received ICD therapies. CONCLUSIONS: A single preimplantation BNP concentration determination is independently predictive of ICD therapies in patients with cardiomyopathies undergoing first time ICD implantation. CRP was not independently predictive of ICD therapies when compared with BNP.

Biomarkers↗

PubMed2005

C reactive protein concentration and recurrence of atrial fibrillation after electrical cardioversion.

BACKGROUND: To test the hypothesis that a high C reactive protein (CRP) concentration would predict recurrence of atrial fibrillation (AF) after cardioversion in patients taking antiarrhythmic drugs. METHODS: 111 patients who underwent direct current cardioversion for symptomatic AF were enrolled. Blood was drawn for CRP determination before cardioversion on the same day. All patients were taking antiarrhythmic drugs before and after electrical cardioversion. RESULTS: After a mean follow up of 76 days, 75 patients had recurrence of AF. In univariate analysis, the median CRP concentration was significantly higher in patients with AF recurrence (3.95 mg/l v 1.81 mg/l, p = 0.002). Among the 55 patients with CRP in the upper 50th centile, 44 (80%) experienced recurrence of AF over a total follow up of 8.98 patient years, whereas among the 56 patients with CRP in the lower 50th centile, 31 (55%) experienced recurrence of AF over a total follow up of 14.3 patient years (p < 0.001). The adjusted hazard ratio comparing the upper 50th centile of CRP with the lower 50th centile of CRP was 2.0 (95% confidence interval 1.2 to 3.2, p = 0.007). CONCLUSIONS: CRP is independently associated with recurrence of AF after electrical cardioversion among patients taking antiarrhythmic drugs. These results suggest that inflammation may have a role in the pathogenesis of AF resistant to antiarrhythmic drugs.

Aged↗

PubMed2001

C-reactive protein elevation in patients with atrial arrhythmias: inflammatory mechanisms and persistence of atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) may persist due to structural changes in the atria that are promoted by inflammation. C-reactive protein (CRP), a marker of systemic inflammation, predicts cardiovascular events and stroke, a common sequela of AF. We hypothesized that CRP is elevated in patients with atrial arrhythmias. METHODS AND RESULTS: Using a case-control study design, CRP in 131 patients with atrial arrhythmias was compared with CRP in 71 control patients. Among arrhythmia patients, 6 had frequent atrial ectopy or tachycardia, 86 had paroxysmal AF, 39 had persistent AF lasting >30 days, and 70 had lone arrhythmias. CRP was higher in arrhythmia than in control patients (median, 0.21 versus 0.096 mg/dL; P<0.001). Arrhythmia patients in AF within 24 hours before sampling had higher CRP than those in sinus rhythm (0.30 versus 0.15 mg/dL; P<0.001). CRP in controls was not different than in patients with atrial ectopy or tachycardia. Lone arrhythmia patients had a CRP of 0.21 mg/dL, which was not significantly lower than arrhythmia patients with structural heart disease (CRP, 0.23 mg/dL) but higher than controls (P=0.002). Persistent AF patients had a higher CRP (0.34 mg/dL) than paroxysmal AF patients (0.18 mg/dL; P=0.008); both groups had higher CRP levels than controls (P</=0.005). CONCLUSIONS: CRP is elevated in AF patients. This study is the first to document elevated CRP in non-postoperative arrhythmia patients. These findings are reinforced by stepwise CRP elevation with higher AF burden. Although the cause of elevated CRP levels in AF patients remains unknown, elevated CRP may reflect an inflammatory state that promotes the persistence of AF.

Analysis of Variance↗

PubMed2000

An exact method for meta-analysis of case-control and follow-up studies.

In this paper, we describe an exact method for estimating a common relative risk across different epidemiologic study designs. The types of studies allowed by the method include case-control studies, follow-up studies with an internal comparison group, and follow-up studies with an external comparison group. Because the method is exact, sparseness of individual studies is not an issue. Those wishing to perform a meta-analysis of case-control studies and follow-up studies in which both the exposure and outcome are rare will find the method particularly useful. To allow one to perform the computations efficiently, we present a partial polynomial multiplication algorithm. We also describe a public-domain computer program that performs the necessary calculations.

Case-Control Studies↗

PubMed1998

Accuracy of death certificates for coding coronary heart disease as the cause of death.

BACKGROUND: Death certificates are widely used in epidemiologic and clinical investigations and for national statistics. OBJECTIVE: To examine the accuracy of death certificates for coding coronary heart disease as the underlying cause of death. DESIGN: Community-based inception cohort followed since 1948. SETTING: Framingham, Massachusetts. PATIENTS: 2683 deceased Framingham Heart Study participants. MEASUREMENTS: Sensitivity, specificity, and predictive values of the death certificate. The reference standard was cause of death adjudicated by a panel of three physicians. RESULTS: Among 2683 decedents, the death certificate coded coronary heart disease as the underlying cause of death for 942; the physician panel assigned coronary heart disease for 758. The death certificate had a sensitivity of 83.8% (95% CI, 81.1 % to 86.4%), positive predictive value of 67.4% (CI, 64.4% to 70.4%), specificity of 84.1% (CI, 82.4% to 85.7%), and negative predictive value of 92.9% (CI, 91.7% to 94.1%) for coronary heart disease. The death certificate assigned coronary heart disease in 51.2% of 242 deaths (9.0% of total deaths) for which the physician panel could not determine a cause. Compared with the physician panel, the death certificate attributed 24.3% more deaths to coronary heart disease overall and more than twice as many deaths to coronary heart disease in decedents who were at least 85 years of age. When deaths that were assigned unknown cause by the physician panel were excluded, the death certificate still assigned more deaths to coronary heart disease (7.9% overall and 43.1% in the oldest age group). CONCLUSIONS: Coronary heart disease may be overrepresented as a cause of death on death certificates. National mortality statistics, which are based on death certificate data, may overestimate the frequency of coronary heart disease by 7.9% to 24.3% overall and by as much as two-fold in older persons.

Adult↗

PubMed1997

Estimating a relative risk across sparse case-control and follow-up studies: a method for meta-analysis.

Meta-analysis is the quantitative technique of combining results from different studies. There is a variety of procedures available for combining effect measures across epidemiologic studies. None of these methods provides an overall effect estimate when the data are sparse within studies and come from different study designs. In this paper we discuss the statistical relations between case-control studies and two types of follow-up studies. We use these relations to develop an exact methodology for combining results across study designs. We also use these relations to derive Mantel-Haenszel type formulae for summarizing results across studies. We illustrate these techniques with data pertaining to breast implants and connective tissue disease.

Breast Implants↗

PubMed1996

Exact estimates for a rate ratio.

The incidence rate ratio is a basic measure of association in epidemiology. We present a simple and efficient method for computing exact confidence limits for the common rate ratio in a series of 2 x 2 tables with person-time denominators. The method uses a polynomial multiplication (convolution) algorithm previously described for an odds ratio. We also present two tests, one asymptotic, the other exact, for evaluating rate ratio homogeneity. We extend these homogeneity tests to apply to data where strata have been partitioned into subgroups in which the rate ratio is assumed homogeneous within subgroups, but not necessarily between them. We conclude with a brief description of a microcomputer program that computes exact and asymptotic estimates for both a rate ratio and an odds ratio.

Algorithms↗