Effect of hypoxic "dose" on physiological responses and sea-level performance

Live high-train low (LH+TL) altitude training was developed in the early 1990s in response to potential training limitations imposed on endurance athletes by traditional live high-train high (LH+TH) altitude training. The essence of LH+TL is that it allows athletes to "live high" for the purpose of facilitating altitude acclimatization, as manifest by a profound and sustained increase in endogenous erythropoietin (EPO) and ultimately an augmented erythrocyte volume, while simultaneously allowing athletes to "train low" for the purpose of replicating sea-level training intensity and oxygen flux, thereby inducing beneficial metabolic and neuromuscular adaptations. In addition to "natural/terrestrial" LH+TL, several simulated LH+TL devices have been developed to conveniently bring the mountain to the athlete, including nitrogen apartments, hypoxic tents, and hypoxicator devices. One of the key questions regarding the practical application of LH+TL is, what is the optimal hypoxic dose needed to facilitate altitude acclimatization and produce the expected beneficial physiological responses and sea-level performance effects? The purpose of this paper is to objectively answer that question, on the basis of an extensive body of research by our group in LH+TL altitude training. We will address three key questions: 1) What is the optimal altitude at which to live? 2) How many days are required at altitude? and 3) How many hours per day are required? On the basis of consistent findings from our research group, we recommend that for athletes to derive the physiological benefits of LH+TL, they need to live at a natural elevation of 2000-2500 m for >or=4 wk for >or=22 h.d(-1).     

Distribution and characterization of cyclo (His-Pro)-like immunoreactivity in the human gastrointestinal tract

Cyclo (His-Pro) [C(HP)] has been measured by radioimmunoassay in perchloric acid extracts of human gastrointestinal (GI) tract structures derived from autopsy sources and fresh colonic biopsies. C(HP) was identified in all regions of the human GI tract, ranging in concentrations from 599 +/- 102 pg/mg protein in stomach, to 127 +/- 26 pg/mg protein in esophagus. The mean concentration of C(HP) from colonic biopsies was 335 +/- 30 pg/mg protein, statistically similar to values derived from postmortem sources. Since C(HP) concentrations are within the range of other gut peptide modulators, cyclo (His-Pro) is speculated to play a role as a new paracrine modulator of human GI tract function(s).     

Clinical course and implantable cardioverter defibrillator therapy in postinfarction women with severe left ventricular dysfunction

BACKGROUND: There are limited data regarding implantable cardioverter defibrillator (ICD) therapy in postinfarction women with severe left ventricular dysfunction. The aim of this study was to evaluate the risk of cardiac events and effects of ICD therapy in women as compared to men enrolled in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II). METHODS AND RESULTS: Among 1,232 patients enrolled in MADIT II, there were 192 (16%) women and 1,040 (84%) men. When compared to men, women had an increased frequency of NYHA class > or =II (70 vs 63%; P = 0.067), hypertension (60% vs 52%; P = 0.047), diabetes (42% vs 34%; P = 0.027), and LBBB (25% vs 17%; P = 0.011), and less frequent CABG surgery (42% vs 60%; P < 0.001). The 2-year cumulative mortality in patients randomized to conventional therapy was not significantly different in women and men (30% and 20%, respectively; P = 0.19). Adjusting for relevant clinical covariates, the hazard ratios for ICD effectiveness were similar in women (0.57; 95% CI = 0.28-1.18; P = 0.132) and men (0.66; 95% CI = 0.48-0.91; P = 0.011). The risk of appropriate ICD therapy for VT/VF was lower in women than in men (hazard ratio = 0.60 for female vs male gender; 95% CI = 0.37-0.98; P = 0.039). CONCLUSIONS: MADIT II women had similar mortality and similar ICD effectiveness when compared to men. MADIT II women with ICDs had a lower risk of arrhythmic events with fewer episodes of ventricular tachycardia than men.     

Multicenter Automatic Defibrillator Implantation Trial–Cardiac Resynchronization Therapy (MADIT‐CRT): Design and Clinical Protocol

The planned MADIT‐CRT trial is designed to determine if CRT‐D will reduce the risk of mortality and HF events by approximately 25% in subjects with ischemic (NYHA class I‐II) and non‐ischemic (NYHA class II) cardiomyopathy, left ventricular dysfunction (EF ≤ 0.30), and prolonged intraventricular conduction (QRS duration ≥ 130 ms).     

Catheter ablation of ventricular tachycardia

Opinion statement Most patients with ventricular tachycardia (VT) associated with structural heart disease should receive an implantable cardioverter-defibrillator as initial therapy. Patients with symptomatic recurrences of tachycardia, including those with multiple defibrillator shocks, are considered for ablation. The vigor with which antiarrhythmic drug therapy is pursued as antecedent therapy to ablation depends on patient factors (eg, medical comorbidity, type of heart disease, number and hemodynamic tolerance of tachycardias) and the previous history of antiarrhythmic drug exposure (eg, side effects, inefficacy). In patients with mild left ventricular dysfunction and well-tolerated tachycardia, ablation may be offered as primary definitive therapy in selected individuals. In patients without structural heart disease, ablation is usually offered as primary definitive therapy to highly symptomatic patients, and is strongly recommended for patients with recurrent tachycardia following initial attempts at drug suppression. Optimal outcome of VT ablation depends on the availability of an experienced team and sophisticated facilities to accommodate the technical challenges associated with the broad spectrum of clinical presentations and arrhythmia mechanisms. Historically, major complications have been reported in up to 10% of patients, including death, stroke, cardiac tamponade, complete heart block, and myocardial infarction. In our own experience with VT ablation over the past 10 years, major complications occurred in three (1.8%) of 168 patients with structural heart disease and one (0.7%) of 142 patients without structural heart disease.