Andrew M. Tonkin

Atrial Fibrillation After Coronary Artery Bypass Grafting Is Associated With Sympathetic Activation

BACKGROUND We prospectively investigated the role of sympathetic activation in the etiology of atrial fibrillation following coronary artery bypass grafting. METHODS Continuous ambulatory monitoring was performed for 80 hours in 131 patients after coronary artery bypass grafting. Right atrial plasma norepinephrine levels were assessed preoperatively and every 4 hours for 48 hours postoperatively. RESULTS Of the 131 patients, 50% (65) had development of atrial fibrillation and 36% (47) required treatment. Onset of atrial fibrillation was preceded by a significant increase in sinus rate and atrial ectopic activity. On multivariate logistic regression, elevated mean postoperative norepinephrine levels (5.78 +/- 2.83 versus 3.57 +/- 1.31 nmol/L; p < 0.0001), increased age (68.9 +/- 5.7 versus 63.8 +/- 8.7 years; p = 0.02), and decreased postoperative magnesium levels (0.79 +/- 0.09 versus 0.83 +/- 0.10 mmol/L; p = 0.02) were independently associated with the occurrence of atrial fibrillation. CONCLUSIONS Elevated norepinephrine levels suggest that sympathetic activation may be important in the pathogenesis of atrial fibrillation after coronary artery bypass grafting, and this underlines the importance of beta-adrenoceptor blockade as prophylaxis.

Passive ventricular constraint amends the course of heart failure: a study in an ovine model of dilated cardiomyopathy

OBJECTIVE Dilated cardiomyopathy (DCM) is associated with a progressive deterioration in cardiac function. We hypothesised that some of the deleterious effects of DCM could be reduced by mechanically limiting the degree of cardiac dilatation. METHODS A Transonic 20A cardiac output (CO) flow-probe was implanted in the pulmonary artery of 12 adult (52 +/- 4 kg) sheep. Early heart failure was created by rapid right ventricular (RV) pacing for 21 days at a rate which resulted in an initial 10% decrease in CO (to a maximum of 190 bpm). A custom polyester jacket (Acorn Cardiovascular, St Paul, MN) was then placed, via a partial lower sternotomy, on the ventricular epicardium of all sheep. Animals were randomised either to jacket retention (wrap) or removal (sham). Pacing was recommenced at a higher rate (that initiated a further 10% decrease in CO) for 28 days. Haemodynamic and echocardiographic parameters were determined at baseline, implant and at termination. RESULTS At termination, the left ventricular fractional shortening was significantly higher (p = 0.03), the degree of mitral valve regurgitation lower (scaled 0-3) (p = 0.03) and the left ventricular long axis area smaller (p = 0.02) in the wrap animals compared with sham. CONCLUSIONS In this model of heart failure, ventricular constraint with a polyester jacket diminished the deterioration in cardiac function associated with progressive dilated cardiomyopathy. These results suggest that maintainance of a more normal cardiac size and shape may be beneficial in patients with dilated cardiomyopathy.

Evidence that patent foramen ovale is not a risk factor for cerebral ischemia in the elderly.

Patent foramen ovale (PFO) may be a risk factor for ischemic stroke in young patients. The aim of this study was to assess the importance of PFO in subjects with a wider age range using patient-control methodology. Transesophageal contrast echocardiography and carotid imaging were performed in 220 consecutive patients with cerebral ischemia (mean age 66 +/- 13 years) and in 202 community-based control subjects (mean age 64 +/- 11 years). Of patients with stroke, 35 (16%) had PFO compared with 31 control subjects (15%) (p = 0.98). Analysis of PFO prevalence by age did not show a significant difference between patients and controls subjects in the age groups < 50 years (27% vs 11%; p = 0.33), 50 to 69 years (17% vs 15%; p = 0.78), and > or = 70 years (12% vs 17%; p = 0.43). However, the group aged < 50 years was relatively small (26 cases, 19 controls). No significant difference in PFO prevalence was detected between patients with cryptogenic stroke (20%), noncryptogenic stroke (14%), and control subjects (15%). These results suggest that PFO is not a risk factor for cerebral ischemia in subjects aged > 50 years, which would have major implications for the investigation and management of stroke patients in this age group. Longitudinal studies are now required to assess the incidence of stroke in symptom-free patients with PFO.

The intraoperative assessment of ascending aortic atheroma : Epiaortic imaging is superior to both transesophageal echocardiography and direct palpation

OBJECTIVES To determine the optimal method for detecting ascending aortic atheroma intraoperatively by comparing manual palpation by the operating surgeon, intraoperative transesophageal echocardiography, and epiaortic ultrasound (linear and phased-array imaging); and to assess risk factors for severe aortic atheroma. DESIGN A longitudinal prospective study. Assessment of the atheroma by manual palpation was blinded to the results of the ultrasound images. SETTING The study was performed in a single university tertiary referral hospital. PARTICIPANTS One hundred consecutive patients undergoing coronary bypass or valve surgery were studied after their written, informed consent. INTERVENTIONS Potential risk factors were evaluated by both a patient questionnaire and examination of prior hospital records. The ascending aorta was assessed by the following methods: manual palpation by the operating surgeon, intraoperative transesophageal echocardiography, and epiaortic ultrasound (linear and phased-array imaging) performed by an echocardiologist. For analysis, the ascending aorta was divided into three equal segments: proximal, mid, and distal, corresponding to regions of different operative manipulations. MEASUREMENTS AND MAIN RESULTS Age older than 70 years and hypertension were significant risk factors for severe ascending aortic atheroma with adjusted odds ratios of 3.3 (95% CI, 1.2 to 9.3) and 3.9 (95% CI, 1.3 to 12.0), respectively. There was no significant difference in atheroma detection between the two ultrasonic epiaortic probes in any segment; however, epiaortic probes were superior to manual palpation in all segments and also superior to transesophageal echocardiography in the mid and distal segments of the ascending aorta. CONCLUSIONS Age older than 70 years and hypertension are significant risk factors for severe ascending aortic atheroma. Intraoperative detection of ascending aortic atheroma is best achieved by epiaortic ultrasound with either a linear or phased array transducer. Transesophageal echocardiography is an insensitive technique for evaluation of mid and distal ascending aortic atheroma and, therefore, of little value in guiding surgical manipulations such as cross-clamping.

Susceptibility to atrial fibrillation: a study in an ovine model of pacing-induced early heart failure.

Propensity for Extrastimulus to Induce AF. Introduction: The development of susceptibility to atrial fibrillation (AF) is a common consequence of many forms of cardiovascular disease, especially heart failure. In this study we used a sheep model of pacing‐induced stable early heart failure to describe, quantify, and relate the level of susceptibility to AF to changes in structural and electrophysiologic parameters.

Comparison of recruitment strategies for a large-scale clinical trial in the elderly

Formal evaluation of recruitment strategies for clinical trials conducted in the community setting, rather than in hospitals, is limited despite recruitment rates and costs having significant implications for the planning of large trials. As part of the development of a large-scale primary prevention trial of low-dose aspirin in 15,000 elderly persons (aged 70 years and above) to be undertaken in a community setting, a pilot study involving 400 participants was carried out to evaluate different recruitment strategies. Three techniques were compared: recruiting from the electoral roll (by individual invitation using direct mail), local community approach (through retirement villages, local media, elderly community groups), and using general/family practice (identifying persons over 70 within a practice and direct mail invitation to participate). Screening of potential participants was carried out by a trained trial nurse with limited involvement only of medical practitioners. The target recruitment figure was achieved in 4 months using the equivalent of 1.5 full-time nurses. General practice was the most effective method utilized, with a yield of one participant recruited per six approached at an estimated cost of A

VALIDATION OF AN ECHOCARDIOGRAPHIC ASSESSMENT OF CARDIAC FUNCTION FOLLOWING MODERATE SIZE MYOCARDIAL INFARCTION IN THE RAT

48.36 per recruited participant. This compares with yield rates of 1 per 29 (for the local community approach) and 1 per 17 for the electoral roll, and costs per participant of A

Management of the Long-Term Intervention with Pravastatin in Ischaemic Disease (LIPID) study after the Scandinavian Simvastatin Survival Study (4S).

42.54 and A

Importance of electrode design, lead configuration and impedance for successful low energy transcatheter atrial defibrillation in dogs

59.37 respectively. Other less tangible benefits of general practice include the greater cooperation of primary care practitioners in patient follow-up and end-point ascertainment.

Atrial Fibrillation: Epidemiology and the Risk and Prevention of Stroke

1. The present study determined whether two dimensional guided M‐mode echocardiography could assess left ventricular (LV) geometry and function following a moderate size myocardial infarction in the rat.