Enhanced Predictive Power of Quantitative TWA during Routine Exercise Testing in the Finnish Cardiovascular Study

Introduction: We examined whether quantification of T-wave alternans (TWA) enhances this parameter's capacity to evaluate the risk for total and cardiovascular mortality and sudden cardiac death (SCD).
Methods and Results: The Finnish Cardiovascular Study (FINCAVAS) enrolled consecutive patients (n = 2,119; 1,342 men and 777 women) with a clinically indicated exercise test with bicycle ergometer. TWA (time domain-modified moving average method) was analyzed from precordial leads, and the results were grouped in increments of 10 μV. Hazard ratios (HR) for total and cardiovascular mortality and SCD were estimated for preexercise, routine exercise, and postexercise stages. Cox regression analysis was performed. During follow-up of 47.1 ± 12.9 months (mean ± standard deviation [SD]), 126 patients died: 62 were cardiovascular deaths, and 33 of these deaths were sudden. During preexercise, TWA ≥ 20 μV predicted the risk for total and cardiovascular mortality (maximum HR >4.4 at 60 μV, P < 0.02 for both). During exercise, HRs of total and cardiovascular mortality were significant when TWA measured ≥50 μV, with 90 μV TWA yielding maximum HRs for total and cardiovascular death of 3.1 (P = 0.03) and 6.4 (P = 0.002), respectively. During postexercise, TWA ≥60 μV indicated risk for total and cardiovascular mortality, with maximum HR of 3.4 at 70 μV (P = 0.01) for cardiovascular mortality. SCD was strongly predicted by TWA levels ≥60 μV during exercise, with maximum HR of 4.6 at 60 μV (P = 0.002), but was not predicted during pre- or postexercise.
Conclusion: Quantification of TWA enhances its capacity for determination of the risk for total and cardiovascular mortality and SCD in low-risk populations. Its prognostic power is superior during exercise compared to preexercise or postexercise.     

Cesarean Section Prophylaxis: Comparison of Two Doses With Three Doses of Mezlocillin

ABSTRACT: A prospective randomized double-blind comparison of two doses, with three doses of mezlocillin for nonelective cesarean section prophylaxis was performed. One hundred seven (107) patients were evaluated. Mezlocillin (4 g) was given post-cord clamping and then at 4-h intervals for a total of two doses or three doses. The incidence of febrile morbidity was lower in the three-dose group (2 of 46, 4%) than the two-dose group (14 of 61, 23%) (P<0.02). However, the incidence of infectious morbidity was not different between the three-dose group (3 of 46, 7%) and the two-dose group (10 of 61, 16%), and the incidence of endomyometritis was similar in the two groups (6.5% vs 9.8%). Among failures of prophylaxis there were no differences compared to successes in the number of potential commensals or potential pathogens cultured from amniotic fluid. However, the proportion of failures among patients with both commensals and potential pathogens isolated (10/58) was significantly greater than among patients with none or only commensals isolated (1/37) (P<0.03). We found mezlocillin to be an effective agent for perioperative cesarean section prophylaxis with two doses as effective as three doses. The presence of clinically important organisms in the amniotic fluid at the time of operation typified patients with postoperative infectious complications despite perioperative prophylaxis.     

Stress-Specific Influences of Opioids on Cardiac Electrical Stability

Opioids and Arrhythmias. Evidence is provided indicating that the action of opioids on cardiac electrical stability is contingent on the nature of the stress that impinges on the myocardium. This concept is illustrated by the studies of three clinically relevant conditions, namely, acute behavioral stress, hemorrhage, and myocardial ischemia. During aversive conditioning in dogs, morphine sulfate has been found to prevent the stress-induced reduction in cardiac electrical stability. This protective effect is significantly blunted by administration of atropine, indicating that enhanced vagal activity plays a major role. However, there is a remaining component of morphine's action, which is probably due to reduced perception of the aversive stress. In the context of hemorrhage, the mu-selective agonist fentanyl substantially reduces the profibrillatory effect of this physiological stress. The main mechanism involved in this condition is amplification of baroreceptor sensitivity leading to inhibition of cardiac sympathetic drive. Full activation of mu receptors with fentanyl is also effective in reducing vulnerability to fibrillation during acute coronary artery occlusion. This effect was due to vagal efferent activation and not to enhanced baroreceptor responsiveness as in the case of hemorrhage. Administration of the partial mu-agonist buprenorphine does not exert an antifibrillatory action. Collectively, these results not only demonstrate the potent stabilizing influence of opioids on cardiac rhythm but also the stress specificity of the intermediary mechanisms.     

Voluntary involvement in community health promotion: the Pawtucket Heart Health Program

The Pawtucket Heart Health Program employs a community activationapproach aimed at reducing cardiovascular morbidity and mortality.This approach is put into operation through the recruitmentof lay volunteers from the community to assist in planning,implementing, evaluating and managing various components ofthe Program. This unique approach of voluntary delivery of programmesis presented in this report. Strategies for the recruitment,interview and placement, training, maintenance and evaluationof volunteers are discussed. The characteristics of people whohave volunteered for specific administrative and service deliveryjobs with the Pawtucket Heart Health Program are also described.The volunteer delivery focus of the Program provides a modelfor adaptation by other public health projects.     

Visualisation of the gastrin receptor within rat mucosa using a biotinylated gastrin antagonist

We have previously demonstrated that the peptide Boc-l -Trp-l -Leu-β-Ala is a potent and specific antagonist of pentagastrin-stimulated acid secretion in both the rat and the dog. Using conventional solution phase methodology, the analogue biotinyl-l -Trp-l -Leu-β-Ala was prepared in reasonable yield and purity and applied to cryostat sections of rat intestinal and other tissues. The sections were exposed to 5–10 μg of peptide and the bound analogue was visualised using streptavidin-fluorescein. The binding of the analogue was demonstrated in sections from fundus, duodenum, ileum, colon, and lung. However, the analogue failed to bind to tissue from the pancreas, heart, kidney, or liver. The binding of the probe was greatly reduced or completely inhibited by preincubation with Boc-l -Trp-l -Leu-β-Ala, pentagastrin, or gastrin 1–17. The distribution of the cells recognised by the probe was consistent with the distribution of histamine-containing enterochromaffin-like cells. The results of this study may have some bearing on current theories of the mechanism of gastrin-stimulated acid release.     

Structural and functional changes of the gastric mucosa in rats with portal hypertension

Structural and functional changes of the gastric mucosa were studied in rats made portal hypertensive by partially ligating the portal vein. Studies were carried out at either 3 or 12 days after ligation or sham operation. At 3 days, structural changes were greater than at 12 days, the major effects being vascular congestion in the lamina propria, muscularis mucosa, submucosa, and submucosal oedema. Transmission electron microscopy showed only a mild hyperplasia in the muscularis mucosa. Gastric blood flow appeared to decrease at 3 days post-ligation compared to sham-operated control rats, but was significantly increased by 12 days after ligation (P less than 0.01). Cardiac output also appeared to increase in the portal hypertensive rats by 12 days post-ligation but this was not statistically significant. Portal venous inflow was significantly increased by 12 days (P less than 0.05) but after correction for collateral circulation liver blood flow had returned to normal values by 12 days post-ligation.     

Pacemaker-Mediated Tachycardia: Engineering Solutions

This discussion summarizes the interaction of refractory periods and upper rate behaviors in modern dual-chamber demand (DDD) devices, the data regarding and nine events initiating VA conduction and engineering solutions proposed and/or implemented to address the problem of pacemaker-mediated tachycardia (PMT). Among the causes of PMT are premature atrial depolarization, loss of atrial capture, a return to the demand mode after asynchronous magnet mode pacing, programming from a mode that does not guarantee AV synchrony to a mode in which atrial tracking can occur, noise, certain situations involving Wenckebach behavior, loss of sensing, and the inability of a rate-smoothing algorithm to allow a rapid change in ventricular rate. Engineering solutions to prevent the occurrence of PMT include a programmable postventricular atrial refractory period (PVARP), differential AV delay, adaptive AV delay, and the ability to discriminate between P waves of atrial origin and those resulting from retrograde conduction from the ventricle. Features such as the ability to lengthen the PVARP for one cycle after exiting the magnet or noise reversion modes or programming to a new mode, lengthen the PVARP for a single cycle following a PVC or revert to DVI pacing for one cycle following a PVC have been developed to recognize initiating events. A third solution. a tachycardia termination algorithm, can recognize and terminate PMT; varying the AV delay to determine whether P waves move in a corresponding manner and using a metabolic sensor to confirm the need for a fast heart rate are other possibilities in the detection of PMT. Diagnostic data features may also be used to evaluate the appropriateness of programmed settings. This discussion concludes that PMT is no longer a significant clinical entity when more advanced DDD pacemakers are utilized.     

Cryoablation of Medically Refractory Nodoventricular Tachycardia

Paroxysmal wide QRS tachycardia, based on a nodoventricular accessory connection, is an uncommon arrhythmia. In this report, the endocardial and epicardial mapping and cryoablation of a nodoventricular fiber, documented to participate in medically refractory tachycardia in an 11-year-old boy, are described. Epicardial cryothermia, applied at the earliest site of right ventricular activation, resulted in the abrupt termination of tachycardia. Endocardial cryothermia was subsequently applied in the perinodal region, the presumed site of origin of the nodoventricular fiber. No tachyarrhythmias were inducible postoperatively, and no antiarrhythmic treatment has been required during 18 months of follow-up. Based on precise anatomic localization of the nodoventricular connection, a definitive cure of associated tachyarrhythmias may be possible utilizing cryothermia, without the requirement for extensive intraoperative dissection.