Dynamic CO2 therapy in periodic breathing: a modeling study to determine optimal timing and dosage regimes.

We examine the potential to treat unstable ventilatory control (seen in periodic breathing, Cheyne-Stokes respiration, and central sleep apnea) with carefully controlled dynamic administration of supplementary CO(2), aiming to reduce ventilatory oscillations with minimum increment in mean CO(2). We used a standard mathematical model to explore the consequences of phasic CO(2) administration, with different timing and dosing algorithms. We found an optimal time window within the ventilation cycle (covering approximately 1/6 of the cycle) during which CO(2) delivery reduces ventilatory fluctuations by >95%.

A fortuitous syncope. The pitfalls of integrated bipolar defibrillator leads.

Myopotential oversensing in implantable defibrillators causing inhibition of pacing and inappropriate therapies is well described. Current literature is dominated by reports of diaphragmatic muscle as the source of such far-field oversensing. Those reporting pectoral muscle sources were invariably due to unipolar sensing circuits, incorrect DF-1 connections or inappropriate programming.

Ethnicity and left ventricular diastolic function in hypertension an ASCOT (Anglo-Scandinavian Cardiac Outcomes Trial) substudy.

Objectives: We investigated whether diastolic function differs between hypertensive patients of African-Caribbean or white European origin and established whether differences could be explained by confounding variables.

Background: African Caribbeans are known to have a higher prevalence of heart failure than white Europeans but it is unclear whether this is a result of known risk factors. Tissue Doppler technology now allows accurate quantification of diastolic function, which is recognized as an important factor in the development of heart failure.

Quantifying the paradoxical effect of higher systolic blood pressure on mortality in chronic heart failure.

Background: Although higher blood pressures are generally recognised to be an adverse prognostic marker in risk assessment of cardiology patients, its relationship to risk in chronic heart failure (CHF) may be different.

Objective: To examine systematically published reports on the relationship between blood pressure and mortality in CHF.

Methods: Medline and Embase were used to identify studies that gave a hazard or relative risk ratio for systolic blood pressure in a stable population with CHF.

Relationship between vessel size and vascular access patency based on preoperatively ultrasound Doppler.

Vascular access is a critical issue in the management of patients with end-stage renal failure and is the leading cause of hospitalization in this group of patients. The object of this study was to find out whether it would be possible to predict vascular access patency rates based on preoperative Doppler assessment of vessel size. Furthermore, this study sought to define the relationship between access flow rate and access patency.

Induction of oscillatory ventilation pattern using dynamic modulation of heart rate through a pacemaker.

For disease states characterized by oscillatory ventilation, an ideal dynamic therapy would apply a counteracting oscillation in ventilation. Modulating respiratory gas transport through the circulation might allow this. We explore the ability of repetitive alternations in heart rate, using a cardiac pacemaker, to elicit oscillations in respiratory variables and discuss the potential for therapeutic exploitation.

Electrophysiological abnormalities occur prior to the development of clinical episodes of atrial fibrillation: observations from human epicardial mapping.

Background: Atrial fibrillation (AF) is characterized by irregular atrial activation maintained by an arrhythmogenic substrate. We addressed the hypothesis that the substrate of human AF includes changes in atrial conduction properties.

Methods: Patients in sinus rhythm (SR) and permanent AF undergoing cardiac surgery underwent right atrial epicardial mapping.

Should we dump the metabolic syndrome? No.

The number of people with the metabolic syndrome is rising alongside obesity. Nevertheless, believes the diagnosis has little practical value. andhowever, think it increases the detection of people at high risk of diabetes and heart disease

The atrioventricular delay of cardiac resynchronization can be optimized hemodynamically during exercise and predicted from resting measurements.

Background: Atrioventricular (AV) optimization of cardiac resynchronization therapy (CRT) is typically calculated at rest. However, patients often become symptomatic during exercise.

Objective: In this study, we use acute noninvasive hemodynamics to optimize the AV delay of CRT during exercise and investigate whether this exercise optimum can be predicted from a three-phase resting model.

The progress of coronary heart disease in Type 2 diabetes as measured by coronary calcium score from electron beam computed tomography (EBCT): the PREDICT study.

Coronary calcification score (CACS) measured by electron beam tomography is well established in the evaluation of cardiovascular risk in general populations. The PREDICT study aims to evaluate prediction of cardiovascular events by CACS in Type 2 diabetic subjects without previous clinical cardiovascular disease. In the present PREDICT sub-study, the rate of progression of CACS and factors influencing this rate were assessed.

Platelet and leukocyte activation, atherosclerosis and inflammation in European and South Asian men.

Background: Increased platelet activation occurs in ischemic heart disease (IHD), but increased platelet activation is also seen in cerebrovascular atherosclerosis and peripheral artery disease. It is not clear therefore whether platelet activation is an indicator of IHD or a marker of generalized atherosclerosis and inflammation. South Asian subjects are at high risk of IHD, but little is known regarding differences in platelet and leukocyte function between European and South Asian subjects.

Efficiency, reproducibility and agreement of five different hemodynamic measures for optimization of cardiac resynchronization therapy.

Background: Several hemodynamic measures have been used for optimization of the AV delay of cardiac resynchronization therapy (CRT), including pulse pressure (PP), systolic blood pressure (SBP) and cardiac output (CO). We aimed to determine whether these measures identify the same optimum and whether they have the same efficiency and reproducibility at identifying this optimum.

Methods And Results: In 22 patients with cardiac resynchronization therapy, we adjusted the AV delay while atrially pacing at 110 bpm and simultaneously recording SBP, diastolic blood pressure (DBP), PP, mean arterial pressure (MAP) and CO.

RESOLVE-ing sepsis in children--not yet!

The Researching Severe Sepsis and Organ Dysfunction in Children: A Global Perspective study of drotrecogin alpha activated versus placebo was the largest study of adjunctive therapy ever performed in children with severe sepsis. Despite this, the study failed to show any significant differences in outcome between the treatment and placebo groups. The results raise questions about how we should perform meaningful clinical trials in relatively rare conditions such as paediatric sepsis, where the easily measurable endpoints (such as death) are infrequent.

Comparison of temporary bifocal right ventricular pacing and biventricular pacing for heart failure: evaluation by tissue Doppler imaging.

Background: The complications and limitations of biventricular pacing largely relate to left ventricular (LV) pacing. An alternative approach was tested of simultaneously pacing the right ventricular (RV) apex and outflow tract (RVOT) or using bifocal right ventricular pacing (BRVP) to provide cardiac resynchronisation.

Methods: 21 consecutive patients with heart failure and severely impaired left ventricular function were studied.

Intra-coronary guidewire mapping-a novel technique to guide ablation of human ventricular tachycardia.

Hypothesis: Endocardial catheter ablation of ventricular tachycardia (VT) may fail if originating from epicardial or intramural locations. We hypothesized that mapping could be achieved using an angioplasty guidewire in the coronary circulation, to guide trans-coronary ablation.

Methods And Results: Six patients (2 male), 64 +/- 14 years and previously unsuccessful endocardial VT ablation were studied.

Characterization of the effects of single ventricular extrastimuli on endocardial activation in human infarct-related ventricular tachycardia.

Objectives: The purpose of this study was to examine the resetting response in human ventricular tachycardia (VT) circuits with 3-dimensional mapping.

Background: In characterizing re-entry with the resetting response, inferences are made about interaction of single ventricular extrastimuli (SVE) with VT.

Methods: Non-contact mapping was used to examine the effects of SVE from 25 sites on 10 infarct-related VT circuits.

Drotrecogin alfa (activated) in children with severe sepsis: a multicentre phase III randomised controlled trial.

Background: Drotrecogin alfa (activated) (DrotAA) is used for the treatment of adults with severe sepsis who have a high risk of dying. A phase 1b open-label study has indicated that the pharmacokinetics and pharmacodynamics of DrotAA are similar in children and adults. We initiated the RESOLVE (REsearching severe Sepsis and Organ dysfunction in children: a gLobal perspectiVE) trial to investigate the efficacy and safety of the drug in children.

The interaction of interventricular pacing intervals and left ventricular lead position during temporary biventricular pacing evaluated by tissue Doppler imaging.

Objective: To determine the effects of interventricular pacing interval and left ventricular (LV) pacing site on ventricular dyssynchrony and function at baseline and during biventricular pacing, using tissue Doppler imaging.

Methods: Using an angioplasty wire to pace the left ventricle, 20 patients with heart failure and left bundle branch block underwent temporary biventricular pacing from lateral (n = 20) and inferior (n = 10) LV sites at five interventricular pacing intervals: +80, +40, synchronous, -40, and -80 ms.

Results: LV ejection fraction (EF) increased (mean (SD) from 18 (8)% to 26 (10)% (p = 0.

Ablation of difficult right-sided accessory pathways aided by mapping of tricuspid annular activation using a Halo catheter : Halo-mapping of right sided accessory pathways.

Objective: To demonstrate that the use of a 20-pole catheter (Halotrade mark) positioned around the tricuspid valve annulus (TVA) is helpful in rapidly localising right free wall accessory pathways (AP), enhancing catheter stability during ablation, and leading to increased success in ablating these challenging pathways.

Patients And Methods: Seven consecutive patients who underwent Halo-mapping of right-sided AP were studied. All but one had previously failed ablation.

Development of respiratory control instability in heart failure: a novel approach to dissect the pathophysiological mechanisms.

Observational data suggest that periodic breathing is more common in subjects with low F(ETCO(2)), high apnoeic thresholds or high chemoreflex sensitivity. It is, however, difficult to determine the individual effect of each variable because they are intrinsically related. To distinguish the effect of isolated changes in chemoreflex sensitivity, mean F(ETCO(2)) and apnoeic threshold, we employed a modelling approach to break their obligatory in vivo interrelationship.

Magnetic resonance guided focused ultrasound surgery of uterine fibroids--the tissue effects of GnRH agonist pre-treatment.

Objective: The purpose of this study was to determine the ablative effect of magnetic resonance guided focused ultrasound (MRgFUS) on fibroid tissue following the administration of gonadotrophin releasing hormone (GnRH) agonist.

Study Design: Fifty women with clinically symptomatic uterine fibroids were treated. Those with uterine diameter of 10 cm or greater were given 3 months pre-treatment with GnRH agonists.

Haemodynamic effects of changes in atrioventricular and interventricular delay in cardiac resynchronisation therapy show a consistent pattern: analysis of shape, magnitude and relative importance of atrioventricular and interventricular delay.

Objective: To assess the haemodynamic effect of simultaneously adjusting atrioventricular (AV) and interventricular (VV) delays.

Method: 35 different combinations of AV and VV delay were tested by using digital photoplethysmography (Finometer) with repeated alternations to measure relative change in systolic blood pressure (SBP(rel)) in 15 patients with cardiac resynchronisation devices for heart failure.

Results: Changing AV delay had a larger effect than changing VV delay (range of SBP(rel) 21 v 4.

Determination of optimal atrioventricular delay for cardiac resynchronization therapy using acute non-invasive blood pressure.

Aims: In this study, we apply non-invasive blood pressure (BP) monitoring, by continuous finger photoplethysmography (Finometer), to detect directly haemodynamic responses during adjustment of the atrioventricular (AV) delay of cardiac resynchronization therapy (CRT), at different heart rates.

Methods And Results: Twelve patients were studied with six re-attending for reproducibility assessment. At each AV delay, systolic BP relative to a reference AV delay of 120 ms (SBPrel) was calculated.