A comparison of T-wave alternans, signal averaged electrocardiography and programmed ventricular stimulation for arrhythmia risk stratification.

OBJECTIVES: The goal of this study was to compare T-wave alternans (TWA), signal-averaged electrocardiography (SAECG) and programmed ventricular stimulation (EPS) for arrhythmia risk stratification in patients undergoing electrophysiology study. BACKGROUND: Accurate identification of patients at increased risk for sustained ventricular arrhythmias is critical to prevent sudden cardiac death. T-wave alternans is a heart rate dependent measure of repolarization that correlates with arrhythmia vulnerability in animal and human studies. Signal-averaged electrocardiography and EPS are more established tests used for risk stratification. METHODS: This was a prospective, multicenter trial of 313 patients in sinus rhythm who were undergoing electrophysiologic study. T-wave alternans, assessed with bicycle ergometry, and SAECG were measured before EPS. The primary end point was sudden cardiac death, sustained ventricular tachycardia, ventricular fibrillation or appropriate implantable defibrillator (ICD) therapy, and the secondary end point was any of these arrhythmias or all-cause mortality. RESULTS: Kaplan-Meier survival analysis of the primary end point showed that TWA predicted events with a relative risk of 10.9, EPS had a relative risk of 7.1 and SAECG had a relative risk of 4.5. The relative risks for the secondary end point were 13.9, 4.7 and 3.3, respectively (p < 0.05). Multivariate analysis of 11 clinical parameters identified only TWA and EPS as independent predictors of events. In the prespecified subgroup with known or suspected ventricular arrhythmias, TWA predicted primary end points with a relative risk of 6.1 and secondary end points with a relative risk of 8.0. CONCLUSIONS: T-wave alternans is a strong independent predictor of spontaneous ventricular arrhythmias or death. It performed as well as programmed stimulation and better than SAECG in risk stratifying patients for life-threatening arrhythmias.

Intestinal helminths of spiny mice (Acomys cahirinus dimidiatus) from St Katherine's Protectorate in the Sinai, Egypt.

Spiny mice, Acomys cahirinus dimidiatus, inhabiting the wadis close to St Katherine in the mountains of the Sinai peninsula, were trapped and their helminth parasites were studied. Sixty one mice provided faeces for analysis and 27 were killed and autopsied. Six species of helminths were recorded (the spirurid nematodes, Protospirura muricola (74.1%) and Mastophorus muris (11.1%), the oxyuroid nematodes, Dentostomella kuntzi (59.3%), Aspiculuris africana (3.7%), and Syphacia minuta (3.7%) and the hymenolepidid cestode Rodentolepis negevi (18.5%)). The spirurids were the dominant species present, accounting for up to 0.87% of total host body weight. Analysis of worm weights and lengths suggested that transmission had been taking place in the months preceding our study. No sex difference in the prevalence or abundance of spirurids was detected. Significant differences were identified in the abundance of total nematode burdens and the mean helminth species richness between the three wadis which provided multiple captures of mice. There was also a marked effect of host age on both parameters. A highly significant positive correlation between spirurid egg counts and total worm biomass indicated that non-invasive techniques based on egg counts could be used to quantify worm burdens and when this technique was applied to a larger sample size (n = 61), a significant difference between sites but no host sex or age effects were detected for spirurid faecal egg counts. The data suggest that there are differences between helminth component communities infecting spiny mice in different neighbouring wadis, a hypothesis which will be explored further through our continuing studies in the Sinai.

Influence of feeding and starvation on the persistence and transmission of Quaranfil virus by Argas (Persicargas) arboreus (Acari: Argasidae).

Viral antigen was detected in the cytoplasm and in associated membranes of salivary gland acinus cells by indirect immunofluorescence and immunoperoxidase staining. Viral ribonucleoproteins (indicated histochemically by presence of pyroninophilic granules) which had accumulated in the cytoplasm of salivary gland type B (granular) acini of unfed Argas (Persicargas) arboreus Kaiser, Hoogstraal & Kohls were no longer visible 24 h after feeding. Virus in tick salivary glands increased from 300 to 500 plaque-forming units during the brief feeding interval (approximately 1 h), but virus was not detectable by 72 h. Overall salivary gland, ovarian, and synganglion tissue levels of Quaranfil virus decreased in the 96 h after feeding, except for synganglion samples in which virus titers increased during 24 h after feeding. Starvation for 105 d resulted in a sevenfold increase in salivary gland viral content compared with those starved 45 d, whereas synganglion tissue titers for Quaranfil virus became undetectable, and ovarian tissue values were similar to those starved for 45 d. Feeding had a greater effect on viral persistence in tissues for ticks starved 60 additional d (comparing 45 with 105 d) in that no Quaranfil virus was detected in any tissue after 48 h (compared with 72 h). Feeding infected ticks (with short extrinsic incubation) on chicks resulted in a peak of host mortality on days 7 and 8, whereas long extrinsic incubation resulted in sporadic mortality over 20 d of monitoring.

His bundle recordings: their contribution to the understanding of human electrophysiology.

His bundle electrocardiography has increased our understanding of the electrophysiology of the conducting system and has confirmed a number concepts which evolved from analysis of surface electrocardiograms. Electrophysiologic evaluation of conduction disease in the cardiac catheterization laboratory has become an accepted diagnostic procedure in determining the site of atrioventricular and ventriculo-atrial block as well as in the evaluation of patients with pre-excitation resulting from conduction through Kent and James bundles. Recent reports suggest that His bundle electrograms may prove to be of clinical and therapeutic significance in determining the site of re-entry in patients with PSVT as well as in determining the short-term prognosis of patients with acute myocardial infarction complicated by incomplete bundle branch block. As our knowledge and understanding of the basic mechanisms, specific therapy, and prognosis of cardiac arrhythmias are expanded, the data derived from His bundle electrocardiography will become more useful in the clinical practice of cardiology.

Prognostic significance of chronic versus acute bundle branch block in acute myocardial infarction.

Of 1125 patients with acute myocardial infarction admitted to Mount Sinai Medical Center in 1971 and 1972, 292 (28.8 percent) had intraventricular conduction defects. In 210 of the 292 patients with intraventricular conduction defect, it was possible to determine if the conduction defect, was present before the infarction (Group 1, 123 patients) or developed acutely with the infarction (Group 2, 87 patients). Of the 210 patients, 52.8 percent died (mean age 72.1 years). Fifty-three patients in Group 1 and 18 patients in Group 2 had isolated left axis deviation (LAD). The mortality was 35 percent and 28 percent respectively. This difference was not significant (p greater than 0.60). Sixty-four of the 210 patients presented with a left bundle branch block (LBBB) pattern. The overall mortality of 54 percent was the same in both groups. Right bundle branch block(RBBB), with either normal axis, left (LAD) or right axis deviation (RAD), was found in 74 patients. Of 40 patients in Group 1, 62 percent died, and of 35 patients in Group 2, 80 percent expired. Again this difference was not significant (p greater than 0.10). In 13 of 25 patients with RBBB in Group 1, death was possible related to progression of the conduction defect. The use of prophylactic temporary pacing is suggested for these patients.