Reducing the incidence of sudden infant death syndrome in the Delta region of Mississippi: a three-pronged approach.

Since the "Back to Sleep" campaign in 1994, which encouraged positioning infants on their backs for sleeping, the incidence of sudden infant death syndrome (SIDS) has decreased dramatically in the United states but remains high in some rural Mississippi communities. We discuss some of the hypotheses and etiologic factors of SIDS. The high incidence of SIDS in the Delta region of Mississippi could be dramatically reduced, primarily through an intensified Back to Sleep campaign. Furthermore, the importance of health education in increasing breast-feeding rates and reducing passive smoke exposure rates in this community is emphasized.

Performance of first-line management functions on productivity of hospital unit personnel.

Eight management functions influence the productivity of unit personnel differently. Although leadership of the first-line manager is the primary driving force, time and effort expended in operations detract from this unit output. Better use of second-line managers is a choice strategy to enhance productivity. Benner's model of professional development, in combination with the creation of a first-second line shared leadership operational framework, is recommended, with follow-up evaluations on unit productivity effect.

Breast-feeding initiation: predictors, attitudes, and practices among blacks and whites in rural Mississippi.

OBJECTIVES: We attempted to determine the incidence, predictors, attitudes, and practices of breast-feeding initiation among women in a low-income rural Mississippi community. METHODS: We interviewed 420 new mothers regarding breast-feeding. RESULTS: Ninety-six women (24%) initiated breast-feeding. More whites (44%) than blacks (20%) initiated breast-feeding. Of those 96, 59% planned to breast-feed for <6 months and 38% for 6 to 12 months. Among women who breast-fed, 78% said they did so because it was healthier. Among those not breast-feeding, most (48%) specifically stated, "I have no reason," while 20% hated the idea and 19% lacked time. About 73% of all women had been encouraged to breast-feed by nonphysicians (83%). For both races, the most significant predictor was a breast-feeding friend or relative. CONCLUSION: Breast-feeding rates in the Mississippi Delta are low, especially among blacks. Effective education programs are needed to increase these rates, and such programs should include friends, spouses, relatives, and significant others.

Long-term follow-up of cardioverter-defibrillator implanted under conscious sedation in prepectoral subfascial position.

BACKGROUND: Implantable cardioverter-defibrillators (ICDs) with intravenous electrode systems and downsized generators can be implanted by use of operative techniques similar to those employed for the insertion of permanent pacemakers. However, the safety, efficacy, and long-term follow-up of simplified implantation procedures remain to be evaluated. This report is a prospective long-term evaluation of nonselected patients receiving ICDs in the prepectoral subfascial position under conscious sedation. METHODS AND RESULTS: Clinical characteristics of the 231 consecutive patients included a mean age of 63 years, a male-to-female ratio of 6.4, a left ventricular ejection fraction of 0.34, a mild-to-moderate heart failure in 91%, coronary artery disease in 84%, and a history of aborted sudden cardiac death or refractory ventricular tachyarrhythmias. Insertion of transvenous leads and prepectoral subfascial ICD implantation were performed in electrophysiology laboratories under local anesthesia and conscious sedation with intravenous midazolam and propofol. Successful implantation in all patients (operation time, 80 +/- 32 minutes, mean +/- SD) irrespective of body size and skin thickness was free of major complications, including need for emergency intubation. After surgery, 1 pocket hematoma, 1 seroma, and 1 pneumothorax required treatment. There was no operative or first-month mortality. During long-term follow-up averaging 453 +/- 296 days, six leads required repositioning, but pocket erosions or infections did not occur. First-year total survival was 97%. CONCLUSIONS: Implantation under conscious sedation of ICDs in the prepectoral subfascial position is a safe and effective procedure with low operative and postoperative morbidity and favorable long-term outcome.

Mosquito (Diptera: Culicidae) and arbovirus activity on the south coast of New South Wales, Australia, in 1985-1988.

An investigation of the seasonal activity of adult mosquitoes and arboviruses in two native forests revealed a mosquito fauna comprising 33 species for the Mogo State Forest-Batemans Bay locality and 34 species for the Termeil State Forest. The mosquito Aedes vigilax was the most abundant species in salt marshes at Mogo State Forest-Batemans Bay, whereas the freshwater species Anopheles annulipes s.l. and Coquillettidia linealis were most abundant at Termeil State Forest. Major faunal differences between the two environments reflected the extensive saline marsh and mudflat estuarine habitats at Batemans Bay and the predominantly freshwater stream, marsh, and lake habitats of Termeil State Forest. A total of 218 virus isolates was recovered from the mosquitoes, comprising Ross River virus (86 isolates), Gan Gan virus (123 isolates), Termeil virus (2 isolates), and 7 unidentified viruses. The period of greatest arbovirus activity was from midsummer through midautumn and coincided with the overall peak activity of the most common mosquito species. Ae. vigilax yielded most isolates of Ross River and Gan Gan viruses and appeared to be the vector of greatest public health concern.

Electrocardiographic signal-averaging during atrial pacing and effect of cycle length on the terminal QRS in patients with and without inducible ventricular tachycardia.

Electrocardiographic signal-averaging during sinus rhythm (61 to 99 beats/min) and atrial pacing (100 to 171 beats/min) were performed to determine the effect of heart rate on late potentials in 15 patients without (group 1) and 7 patients with (group 2) inducible sustained ventricular tachycardia (VT). In sinus rhythm (79 +/- 12 vs 77 +/- 12 beats/min, difference not significant), the duration of the low-amplitude signal less than 40 microV was longer in group 2 than group 1 (43 +/- 21 vs 26 +/- 8 ms, p = 0.034) and more patients had late potentials (57 vs 7%, p = 0.021), but QRS duration (121 +/- 32 vs 98 +/- 19 ms) and terminal voltage (33 +/- 33 vs 50 +/- 26 ms) were not significantly different. With atrial pacing in group 1 (128 +/- 16 beats/min), 3 patients developed a simultaneous decrease in terminal voltage and an increase in terminal QRS duration consistent with a late potential, but mean total and terminal durations were unchanged. Terminal voltage increased (50 +/- 26 to 59 +/- 40) but not significantly. With atrial pacing in group 2 (119 +/- 12 beats/min) all patients either had a late potential or developed a simultaneous decrease in terminal voltage and an increase in terminal QRS duration (p = 0.001 vs group 1). Root mean square (p = 0.001 vs group 1). Root mean square voltage decreased (33 +/- 23 to 22 +/- 23) and became significantly different from group 1 (p = 0.017). Mean QRS duration, root mean square terminal voltage and low-amplitude terminal QRS duration, however, were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Entrainment onset in atrioventricular reciprocating tachycardia: value in bypass tract localization and relationship to the preexcitation index.

The timing of entrainment onset has been shown to correlate with the conduction time to critical elements of a tachycardia circuit in a pacemaker model of reentrant ventricular tachycardia (VT). The utility of this method in evaluating clinical reentrant tachycardias was therefore evaluated in 24 patients with symptomatic Wolff-Parkinson-White syndrome and single bypass tracts (left free wall in 17, posteroseptal in 5, anteroseptal in 1, and right free wall in 1). Right ventricular apex (RVA) pacing during orthodromic atrioventricular reentrant tachycardia (oAVRT) at 10-70 msec less than tachycardia cycle length demonstrated concealed entrainment of the tachycardia in all patients studied. An entrainment index (EI), defined as the minimal prematurity of the ventricular stimulus that first resulted in atrial reset, was calculated from multiple entrainments in each patient. The EI was 121 +/- 25, 83 +/- 19, and 55 msec for left free wall, septal, and right free-wall bypass tracts, respectively (P = 0.004 for difference between left free wall and septal). A corrected EI, derived by subtracting the amount of atrial reset from the EI, gave values of 108 +/- 22 and 71 +/- 17 msec for left free wall and septal bypass tracts (P = 0.001). These values were compared to the preexcitation index (PI) by linear regression analysis in these patients. The PI correlated closely with both the EI and the corrected EI (r = 0.90 and 0.93, respectively), but the PI could only be derived in 12/17 (71%) left free-wall tachycardias versus the EI in 17/17 (100%) (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation of cocaine-induced coronary vasoconstriction by beta-adrenergic blockade.

STUDY OBJECTIVE: To determine whether beta-adrenergic blockade augments cocaine-induced coronary artery vasoconstriction. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: A cardiac catheterization laboratory in an urban teaching hospital. PATIENTS: Thirty clinically stable patient volunteers referred for catheterization for evaluation of chest pain. INTERVENTIONS: Heart rate, arterial pressure, coronary sinus blood flow (by thermodilution), and epicardial left coronary arterial dimensions were measured before and 15 minutes after intranasal saline or cocaine administration (2 mg/kg body weight) and again after intracoronary propranolol administration (2 mg in 5 minutes). MEASUREMENTS AND MAIN RESULTS: No variables changed after saline administration. After cocaine administration, arterial pressure and rate-pressure product increased; coronary sinus blood flow fell (139 +/- 28 [mean +/- SE] to 120 +/- 20 mL/min); coronary vascular resistance (mean arterial pressure divided by coronary sinus blood flow) rose (0.87 +/- 0.10 to 1.05 +/- 0.10 mm Hg/mL.min); and coronary arterial diameters decreased by between 6% and 9% (P less than 0.05 for all variables). Subsequently, intracoronary propranolol administration caused no change in arterial pressure or rate-pressure product but further decreased coronary sinus blood flow (to 100 +/- 14 mL/min) and increased coronary vascular resistance (to 1.20 +/- 0.12 mm Hg/mL.min) (P less than 0.05 for both). CONCLUSIONS: Cocaine-induced coronary vasoconstriction is potentiated by beta-adrenergic blockade. Beta-adrenergic blocking agents probably should be avoided in patients with cocaine-associated myocardial ischemia or infarction.

Entrainment onset in a pacemaker model of reentrant ventricular tachycardia: insight into localization of critical elements of a reentrant circuit.

We investigated entrainment in a pacemaker model of reentrant ventricular tachycardia (VT) created in the intact dog heart using a VAT pacemaker with both electrodes on the ventricular epicardium. This produced an incessant wide QRS tachycardia originating from the pacing site with a cycle length equal to the conduction time between the sensing and pacing site plus the pacemaker AV delay. The conduction time between entrainment sites and the critical elements of the reentrant pathway (sensing and pacing sites) was determined by pacing at a comparable cycle length during sinus rhythm. Entrainment was achieved in 12 tachycardias with pacing at 1-4 sites at cycle lengths 10-100 msec shorter than tachycardia and confirmed by constant QRS fusion, progressive QRS fusion, and coupling of the first nonpaced QRS or intracardiac electrogram at the entraining cycle length. By least squares regression, the timing of entrainment onset (first reset of pacing or sensing site electrogram) measured by the prematurity of the local electrogram at the entraining site was highly correlated to the shortest conduction time between the entraining site and the circuit (F value of 84.7 and R = 0.752 [P less than 0.001]). Therefore, the timing of entrainment onset maybe useful in predicting the conduction time from the entraining site to critical elements of a reentrant circuit and may assist in localization of the reentrant pathway.

Influence of anterograde flow in the infarct artery on the incidence of late potentials after acute myocardial infarction.

In patients after myocardial infarction, survival is influenced by the presence or absence of anterograde flow in the infarct artery, and late potentials on signal-averaged electrocardiography identify those at risk for tachyarrhythmias and sudden death. To assess the frequency of late potentials in survivors of first infarction, coronary arteriography and signal-averaged electrocardiography were performed in 109 subjects (64 men, 45 women, aged 30 to 77 years), 49 with (group I) and 60 without (group II) anterograde flow in the infarct artery. The groups were similar in age, sex, infarct artery, severity of coronary artery disease and left ventricular function. However, only 4 (8%) of group I had late potentials, whereas 24 (40%) of group II had late potentials (p less than 0.001). Thus, anterograde flow in the infarct artery after myocardial infarction is associated with a low incidence of late potentials on signal-averaged electrocardiography, whereas the absence of anterograde flow is more often associated with late potentials.

Limitations of the metabolic rate meter for measuring oxygen consumption and cardiac output.

Over the past few years, a metabolic rate meter has been introduced for easy measurement of oxygen consumption. However, its accuracy is unproved. In 40 patients (26 men, 14 women, ages 34 to 73 years), cardiac output was measured simultaneously by thermodilution and the Fick method using the metabolic rate meter to quantitate oxygen consumption. In comparison with thermodilution, the results using the Fick method were low (5.26 +/- 1.18 vs 4.14 +/- 0.99 liters/min, respectively, p less than 0.01). In 18 patients cardiac output also was measured by the Fick method using a Douglas bag to quantitate oxygen consumption. In these patients, oxygen consumption measured with the metabolic rate meter was lower than that obtained using the Douglas bag (168 +/- 25 vs 216 +/- 42 ml/min, respectively, p less than 0.01). With the Douglas bag, the Fick and thermodilution cardiac output measurements were similar (4.68 +/- 1.08 vs 4.87 +/- 0.86 liters/min, respectively, difference not significant), and they differed by less than or equal to 10% in 15 patients. In contrast, with the metabolic rate meter, the results of thermodilution were higher than those with the Fick method (4.84 +/- 0.95 vs 3.60 +/- 0.71 liters/min, respectively, p less than 0.01), and differed by less than or equal to 10% in only 1 patient (p less than 0.01). Thus, the values for oxygen consumption and cardiac output obtained with the metabolic rate meter are lower than actual values. This device is less accurate than the Douglas bag.

Sudden cardiac death: etiologies, pathogenesis, and management.

Sudden death claims an estimated 350,000 lives per year in the United States. When death occurs within 1 hour of the onset of symptoms, 90% are the result of ventricular tachyarrhythmias. The majority of victims are middle-aged men with coronary artery disease, but in approximately 25%, sudden death is the presenting manifestation of their problem. In some populations, the detection of premature ventricular complexes (PVCs) by ambulatory monitoring is predictive of an increased risk of sudden death. However, the arrhythmia that best predicts this risk is unclear, and ambient arrhythmias are only a modest marker of this risk. Therapy to suppress asymptomatic PVCs has not been shown to be effective in preventing sudden death, and in some cases, lethal arrhythmias can be prevented without significant effects on ambient arrhythmias. Other risk markers such as depressed left ventricular function and the presence of low-amplitude, long-duration, late potentials recorded on a signal averaged electrocardiogram are more powerful predictors of risk than are PVCs. These latter findings in particular support the presence of areas of slow electrical conduction (a requirement for reentrant mechanism arrhythmias) and suggest that an abnormal electrical environment or "substrate" is the most important factor in this problem. The management of patients at risk for sudden death is controversial. While postinfarct survivors with arrhythmias constitute a population at increased risk, the absolute risk is only about 5% in the first year and has not been shown to be improved by conventional antiarrhythmic drugs. Small study size, arrhythmia variability, ill-defined end points, and proarrhythmia may partially explain this apparent lack of efficacy. The prophylactic use of antiarrhythmic drugs other than beta-blockers to prevent sudden death in asymptomatic populations at risk is therefore of unproven benefit. By contrast, patients who have survived a life-threatening arrhythmia unrelated to an acute myocardial infarction have an approximately 30% risk of recurrence in the following year. In these patients, the use of ambulatory monitoring to guide therapy is limited by the high incidence of false-negative responses (lethal arrhythmia recurrence despite ambient arrhythmia suppression) and the lack of frequent spontaneous arrhythmias in many patients. In this patient population, electrophysiological testing can be used to prognosticate recurrence and gain insight into arrhythmia mechanism, stability, and hemodynamic tolerance. The technique is also useful in guiding both pharmacological and nonpharmacological therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of preexisting bundle branch block on the electrocardiographic diagnosis of ventricular tachycardia.

The electrocardiograms (ECGs) of 80 ventricular tachycardias (VTs) occurring in 52 patients with a normal baseline QRS duration (group 1) were compared with 26 VTs in 18 patients with preexisting bundle branch block (group 2). The effects of bundle branch block on the sensitivity of previously defined electrocardiographic criteria for differentiating VT from supraventricular tachycardia with aberration were under investigation. Specificity was examined by comparing VT to the baseline ECG in group 2 patients. The VTs in groups 1 and 2 were comparable with respect to rate, bundle branch pattern, R-wave pattern in V1 with right bundle, frequency of an R/S ratio less than 1 in V6 with right bundle, Q-wave frequency in V6 with left bundle and quadrant of the frontal plane axis. Precordial QRS concordance was more frequent (35 vs 15%, p = 0.045) and a greater than 30 ms R wave in V1 or V2 with left bundle pattern was less frequent (18 vs 63%, p = 0.015) in group 2 vs group 1 arrhythmias. Right bundle pattern VT usually had a monophasic R wave in V1 (69%), whereas preexisting right bundle usually had a biphasic R wave in V1 (82%, p = 0.001). The quadrant of the frontal plane axis was significantly different between the VT ECGs and the ECGs with preexisting bundle branch block (p = 0.029) with a right superior quadrant axis only seen in VT (19%). A greater than 30 ms R wave in V1 or V2 with left bundle was also only seen in VT (52 vs 0%, p = 0.052).(ABSTRACT TRUNCATED AT 250 WORDS)

Entrainment of ventricular tachycardia in postoperative tetralogy of Fallot.

The mechanism of ventricular tachycardia (VT) in postoperative tetralogy of Fallot has been ascribed to both reentry and triggered automaticity. We performed electrophysiologic studies on a patient with this condition and induced sustained uniform ventricular tachycardia by programmed extrastimulation. Pacing during the tachycardia at multiple cycle lengths from the right ventricular apex (RVA) and outflow tract (RVOT) produced constant but progressive fusion between the paced and tachycardia QRS. With termination of pacing, the last captured complex was unfused but coupled at the paced cycle length and then the tachycardia resumed at its intrinsic rate. Therefore, the VT was entrained. In addition, an area of slow conduction between the RVOT and RVA was demonstrated. These findings support a reentrant mechanism of this arrhythmia.

Potentiation of nitroglycerin-induced coronary dilatation by N-acetylcysteine.

Previous studies have suggested that (1) nitroglycerin causes vasodilatation by interacting with sulfhydryl groups in vascular smooth muscle, thereby activating guanylate cyclase and increasing the intracellular concentration of cyclic GMP, and (2) N-acetylcysteine, a source of sulfhydryl groups, potentiates the peripheral vasodilatory effect of nitroglycerin. This study was performed to explore the influence of N-acetylcysteine on nitroglycerin-induced coronary dilatation. In 18 patients (13 men and five women, 30 to 76 years old), coronary sinus blood flow (by thermodilution) was measured before and during intracoronary administration of nitroglycerin, 25 micrograms, both before and 5 min after a 15 min intravenous infusion of (1) 5% dextrose in water (n = 8, control) or (2) 100 mg/kg N-acetylcysteine (n = 10). Nitroglycerin caused no change in heart rate or systemic arterial pressure. In the control patients, coronary sinus blood flow behaved similarly during the two injections: it was 134 +/- 36 ml/min (mean +/- SD) before and 183 +/- 50 ml/min during injection No. 1 (average increase, 49 +/- 25 ml/min; average percent increase, 38 +/- 21%); and it was 131 +/- 34 ml/min before and 178 +/- 45 ml/min during injection No. 2 (average increase, 47 +/- 23 ml/min; average percent increase, 37 +/- 20%) (NS compared with injection 1). In the patients who received N-acetylcysteine, coronary sinus blood flow was 149 +/- 48 ml/min before and 191 +/- 54 ml/min during injection 1 (average increase, 42 +/- 15 ml/min; average percent increase, 30 +/- 12%) (NS compared with eight control values).(ABSTRACT TRUNCATED AT 250 WORDS)

A dialysis device for use in the determination of density increments.

A procedure for the dialysis of small volumes of solution prior to density-increment determination is described. An easily constructed device, which can also be used for general dialysis procedures, facilitates solution transfer and ensures minimal exposure of the retentate to the atmosphere.