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Biomedical subjects

H V Barron

Publications and source records attributed to H V Barron.

52 records · Page 3Linked to original sources
PubMed1997

Influence of gender on cardiovascular mortality in acute myocardial infarction patients with high indication for coronary angiography.

BACKGROUND: This study was undertaken to study gender differences in the use of coronary angiography (CA), revascularization (RV), and cardiovascular disease (CVD) mortality in patient with acute myocardial infarction (AMI) who were assigned to "High Indication for CA" per the American College of Cardiology/American Heart Association (ACC/ AHA) practice guidelines. METHODS AND RESULTS: This is a historical prospective study based on a stratified random sample of 1165 AMI patients from January 1990 to December 1992 at seven health maintenance organization hospitals. CA was highly indicated in 286 women and 564 men. In a Cox hazard ratio (HR), women received significantly (P<.05) fewer CAs (HR, .78) and RVs (HR, .62) than men after adjusting for age, Charlson index, and congestive heart failure. Crude CVD mortality for women was higher than men (HR, 1.7). After adjustments for age, Charlson index, and congestive heart failure, the HR was reduced to 1.19 for women. Further adjustment for CA and RV lowered CVD mortality in women slightly (HR, 1.14). RV is associated with lowered CVD (HR, .41). CONCLUSIONS: In patients with high indication for CA, use of CA and RV was significantly lower in women. After adjustments were made for risk profile and treatment modalities, women did not have a significantly increased risk for CVD compared with men. However, the apparent protective effect of RV in patients with a high indication for CA suggests that practices in line with ACC/AHA guidelines may reduce CVD in both women and men.

Adult↗
PubMed1997

P-wave morphology during right atrial pacing before and after atrial flutter ablation--a new marker for success.

Fourteen patients with typical atrial flutter underwent pacing from the low lateral right atrium and the proximal coronary sinus in normal sinus rhythm before and after catheter ablation. During low lateral right atrial pacing, a positive change in P-wave morphology in the inferior leads was noted in every patient (n = 12) in whom bidirectional block was achieved; no recurrence was noted in any of these patients.

Aged↗
PubMed1997

Mortality benefit of implantable cardioverter-defibrillator therapy in patients with persistent malignant ventricular arrhythmias despite amiodarone treatment.

Implantable cardioverter defibrillators (ICDs) are very effective in preventing sudden cardiac death. However, debate continues as to whether ICD implantation is superior to amiodarone in prolonging survival in patients with life-threatening ventricular arrhythmias. Of 442 consecutive patients treated with amiodarone, we identified 48 patients with symptomatic ventricular arrhythmias who met all of the following inclusion criteria: (1) had inducible sustained ventricular tachycardia at baseline electrophysiologic study, (2) had an oral amiodarone load of at least 10 g over 10 to 14 days, (3) remained inducible with a hemodynamically unstable ventricular arrhythmia at follow-up electrophysiologic study, and (4) were advised to continue amiodarone therapy and undergo ICD implantation. Patients who agreed to undergo ICD implantation (n = 28) had a lower ejection fraction (29 +/- 9% vs 40 +/- 12% p <0.005) and were younger (61.0 +/- 10 vs 69 +/- 7 years, p <0.01) than patients who refused device implantation (n = 20). Using a Cox proportional-hazards model, defibrillator therapy was the strongest independent predictor of improved survival in patients with an ejection fraction < or =40% (RR = 0.42; 95% confidence interval 0.22 to 0.79). Thus, patients with depressed ejection fraction and continued inducibility of sustained ventricular tachycardia despite oral amiodarone loading have a poor prognosis. In such patients, ICDs are associated with a 58% reduction in total cardiac mortality.

Aged↗
PubMed1997

Effect of beta-adrenergic blocking agents on mortality rate in patients not revascularized after myocardial infarction: data from a large HMO.

We investigated whether patients who do not undergo coronary angiography and therefore any form of revascularization after a myocardial infarction derive greater benefit from chronic beta-blocker therapy than patients who undergo coronary angiography. With multivariate analyses, treatment with beta-blockers was a much stronger predictor of survival in patients who did not undergo coronary angiography (relative risk = 0.38, p = 0.005) than in those patients who did undergo catheterization (p < 0.05 for interaction). Our findings provide direct support for the recommendation by the American College of Cardiology/American Heart Association task force that beta-blocker therapy should be initiated for all infarct survivors who do not undergo revascularization and who have no contraindications.

Adrenergic beta-Antagonists↗
PubMed1996

Variation among hospitals in coronary-angiography practices and outcomes after myocardial infarction in a large health maintenance organization.

BACKGROUND: Wide geographic variation in the use of coronary angiography after myocardial infarction has been documented internationally and within the United States. An associated variation in clinical outcomes has not been consistently demonstrated. METHODS: We assessed the risk of death from heart disease and of any heart disease event (death, reinfarction, or rehospitalization) over a follow-up period of one to four years in 6851 patients hospitalized with acute myocardial infarction at 16 Kaiser Permanente hospitals from 1990 through 1992. The percentage of patients who underwent angiography within three months after infarction ranged from 30 to 77 percent. We selected a subcohort of 1109 patients from three hospitals with higher rates of angiography and four with lower rates for a record review to assess the severity of infarction, the number of coexisting conditions, treatments received, and the appropriateness and necessity of angiography, using established criteria. RESULTS: The rates of angiography were inversely related to the risk of death from heart disease (P= 0.03) and the risk of heart disease events (P<0.001) among the 16 hospitals after adjustment for age, sex, race, coexisting conditions, and the location of the infarction (subendocardial vs. transmural). In the subcohort, 440 patients met criteria indicating that angiography was necessary and 669 did not. Among the former, patients treated at hospitals with higher rates of angiography had a lower risk of death and of any heart disease event than those treated at hospitals with lower rates (hazard ratios, 0.67 and 0.72, respectively). Among the latter, the apparent benefits of being treated at hospitals with higher angiography rates were smaller (hazard ratios, 0.85 to 0.90 for death and any heart disease event, respectively). CONCLUSIONS: During the one to four years after myocardial infarction, patients treated at hospitals with higher rates of angiography had more favorable outcomes than those treated at hospitals with lower rates. This association was stronger among patients for whom published criteria indicated that angiography was necessary.

Aged↗
PubMed1996

Mode of onset of torsade de pointes in congenital long QT syndrome.

OBJECTIVES: We sought to describe the mode of onset of spontaneous torsade de pointes in the congenital long QT syndrome. BACKGROUND: Contemporary classifications of the long QT syndrome (LQTS) refer to the congenital LQTS as "adrenergic dependent" and to the acquired LQTS as "pause dependent." Overlap between these two categories has been recognized, and a subgroup of patients with "idiopathic pause-dependent torsade" has been described. However, it is not known how commonly torsade is preceded by pauses in the congenital LQTS. METHODS: We reviewed the electrocardiograms (ECGs) of all our patients with congenital LQTS evaluated for syncope or sudden death (30 patients). Documentation of the onset of torsade de pointes was available for 15 patients. All these patients had "definitive LQTS" by accepted clinical and ECG criteria. RESULTS: Pause-dependent torsade de pointes was clearly documented in 14 of the 15 patients (95% confidence interval 68% to 100%). The cycle length of the pause leading to torsade was 1.3 +/- 0.2 times longer than the basic cycle length, and most pauses leading to torsade were unequivocally longer than the preceding basic cycle length (80% of pauses were > 80 ms longer than the preceding cycle length). CONCLUSIONS: The "long-short" sequence, which has been recognized as a hallmark of torsade de pointes in the acquired LQTS, plays a major role in the genesis of torsade in the congenital LQTS as well. Our findings have important therapeutic implications regarding the use of pacemakers for prevention of torsade in the congenital LQTS.

Adult↗
PubMed1996

Beta blockers prevent cardiac death following a myocardial infarction: so why are so many infarct survivors discharged without beta blockers?

Too often, infarct survivors are discharged from physician's care and/or hospital stay without beta-blocker therapy. This reflects concerns by physicians regarding precipitation of adverse effects. Ironically, many of the infarct survivors not receiving beta blockers could actually derive the greatest benefits from this treatment.

Adrenergic beta-Antagonists↗
PubMed1996

Autonomic nervous system and sudden cardiac death.

In the United States, sudden cardiac death is a major public health problem, accounting for approximately 300,000 deaths annually. Accurate identification of those patients at highest risk for this event has been problematic. The use of signal-averaged electrocardiography, Holter monitoring and assessment of left ventricular function have been shown to be predictive of future arrhythmic events in patients after a myocardial infarction. However, the clinical utility of these tests has been limited by their low sensitivity and positive predictive value. It has become increasingly clear that the autonomic nervous system is extremely important in the pathogenesis of ventricular arrhythmias and sudden cardiac death. The two most important techniques used to study the autonomic nervous system--heart rate variability and baroreflex sensitivity--are reviewed, and the clinical and experimental data suggesting that these techniques are powerful predictors of future arrhythmic events are discussed in depth.

Animals↗
PubMed1996

Postextrasystolic U wave augmentation, a new marker of increased arrhythmic risk in patients without the long QT syndrome.

OBJECTIVES: We attempted to determine the correlation between the presence of postextrasystolic changes in the STU segment and a history of sustained ventricular arrhythmias. BACKGROUND: Postextrasystolic U wave augmentation (a marked increment in U wave amplitude after premature ventricular complexes [PVCs]) is an adverse prognostic sign in the "pause-dependent long QT syndrome." However, the prevalence of postextrasystolic changes in patients without the long QT syndrome is unknown. METHODS: We compared the configuration of the STU segment of the postextrasystolic beat (the sinus beat after a PVC) with the STU configuration during sinus rhythm in three patient groups: 1) 41 patients with spontaneous ventricular tachycardia/fibrillation (VT/VF) (VT/VF group), 2) 63 patients with heart disease and high grade ventricular arrhythmias (control group), and 3) 29 patients with high grade ventricular arrhythmias but no heart disease (reference group). RESULTS: Postextrasystolic T wave changes did not correlate with a history of ventricular tachyarrhythmias. However, postextrasystolic U wave changes were more common among the patients with VT/VF than among control subjects (39% vs. 8.7%, p < 0.001). By logistic multiple regression analysis, a low left ventricular ejection fraction (p < 0.001) and postextrasystolic U wave changes (p < 0.005) were independent predictors of ventricular tachyarrhythmias. CONCLUSIONS: Postextrasystolic T wave changes are common and lack predictive value. Postextrasystolic U wave changes may be a specific marker of a tendency to the development of spontaneous ventricular arrhythmias. Prospective studies should be performed to confirm this association.

Aged↗
PubMed1996

Options in antihypertensive drug therapy. Help in choosing from among the many agents.

The fifth report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure (JNC V) states that "because diuretics and beta blockers are the only classes of drugs that have been used in long-term controlled trials and shown to reduce morbidity and mortality, they are recommended as first choice agents unless they are contraindicated or unacceptable." These guidelines are important, but practitioners should remember that many effective and well-tolerated classes of drugs are available for treating hypertension, and one may have greater usefulness than another in a given patient. For example, an angiotensin-converting enzyme inhibitor may be appropriate in a patient with hypertension and congestive heart failure or diabetic nephropathy. A calcium channel blocker may be beneficial in a patient with hypertension and concomitant angina. Results of prospective studies comparing classes of antihypertensive drugs and measuring clinically significant end points may help guide pharmacotherapy in the future.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1990

A1 adenosine receptors inhibit chloride transport in the shark rectal gland. Dissociation of inhibition and cyclic AMP.

In the in vitro perfused rectal gland of the dogfish shark (Squalus acanthias), the adenosine analogue 2-chloroadenosine (2Clado) completely and reversibly inhibited forskolin-stimulated chloride secretion with an IC50 of 5 nM. Other A1 receptor agonists including cyclohexyladenosine (CHA), N-ethylcarboxamideadenosine (NECA) and R-phenylisopropyl-adenosine (R-PIA) also completely inhibited forskolin stimulated chloride secretion. The "S" stereoisomer of PIA (S-PIA) was a less potent inhibitor of forskolin stimulated chloride secretion, consistent with the affinity profile of PIA stereoisomers for an A1 receptor. The adenosine receptor antagonists 8-phenyltheophylline and 8-cyclopentyltheophylline completely blocked the effect of 2Clado to inhibit forskolin-stimulated chloride secretion. When chloride secretion and tissue cyclic (c)AMP content were determined simultaneously in perfused glands, 2Clado completely inhibited secretion but only inhibited forskolin stimulated cAMP accumulation by 34-40%, indicating that the mechanism of inhibition of secretion by 2Clado is at least partially cAMP independent. Consistent with these results, A1 receptor agonists only modestly inhibited (9-15%) forskolin stimulated adenylate cyclase activity and 2Clado markedly inhibited chloride secretion stimulated by a permeant cAMP analogue, 8-chlorophenylthio cAMP (8CPT cAMP). These findings provide the first evidence for a high affinity A1 adenosine receptor that inhibits hormone stimulated ion transport in a model epithelia. A major portion of this inhibition occurs by a mechanism that is independent of the cAMP messenger system.

2-Chloroadenosine↗
PubMedDate not supplied

Reperfusion therapy for acute myocardial infarction: observations from the National Registry of Myocardial Infarction 2.

The National Registry of Myocardial Infarction 2 (NRMI-2) provides a unique opportunity to evaluate the practice patterns among participating cardiology and emergency medicine departments involved in the care of patients with acute myocardial infarction. The data from NRMI-2 suggest that almost 1/3 of all non-transfer-in and non-transfer-out patients are eligible for reperfusion therapy. Furthermore, of those patients who are clearly eligible for reperfusion therapy, 24% are not given this proven therapy. Specifically, women, the elderly, patients without chest pain on presentation, and those patients at highest risk for in-hospital mortality were least likely to be treated with reperfusion therapy. The reason for underuse of reperfusion therapy may in part reflect a concern for adverse bleeding events associated with the use of thrombolytic therapy. The data from NRMI-2 also suggest that patients with contraindications to thrombolysis may be very appropriate for primary angioplasty. Realizing the full potential benefits of reperfusion therapy in terms of reduced cardiovascular morbidity and mortality will require that clinical practice patterns be aligned more closely with the recommended national guidelines, which are based on extensive clinical trial data that show the benefit of reperfusion therapy in a wide range of patients with acute myocardial infarction. By using observational databases, such as the NRMI-2, which describe how clinical care is administered in nonclinical trial settings, we can continually monitor our progress and initiate changes to ensure that patients are given access to the many therapies that have been shown to improve their quality of life and survival.

Adult↗