The implantable cardioverter-defibrillator: postcode prescribing in the UK 1998-2002.

OBJECTIVE: To determine the rate of implantable cardioverter-defibrillator (ICD) implantation across the UK during the period 1998 to 2002. DESIGN: Observational self reporting with cross checking. SETTING: All ICD implanting centres coordinated by the National Pacemaker and ICD Database. PATIENTS: Every patient receiving an ICD in the UK from 1998 to 2002. MAIN OUTCOME MEASURES: Date of implantation and postcode of each ICD recipient during the study period. RESULTS: ICD implantation increased in the UK in the five year period studied but fell far short of the European average and national targets. Implantation rates varied greatly by region. CONCLUSIONS: The low rate of ICD implantation in the UK and the disparity between regions require further study to determine the barriers to this evidence based treatment.

Improving care for patients with acute coronary syndromes: initial results from the National Audit of Myocardial Infarction Project (MINAP).

OBJECTIVE: To describe the improvements in care that have followed the introduction of an electronic data entry and analysis system providing contemporary feedback on the management of acute coronary syndromes in 230 hospitals in England and Wales. DESIGN: Observational study METHODS: A secure electronic system was used to transfer encrypted data on patients with acute coronary syndromes from collaborating hospitals to central servers for analysis. Immediate online data entry to the central servers by hospitals allowed contemporary analyses of performance and immediate comparison with the national aggregate performance. RESULTS: The records of 156 902 patients receiving a final diagnosis of acute coronary syndrome during three years between October 2000 and September 2003 were analysed. Of 69 113 patients with ST segment elevation infarction, 75.4% received thrombolytic treatment. Between the first and last years of the study the median interval from hospital arrival to treatment fell for eligible patients from 38 (interquartile range 22-58) to 20 (interquartile range 14-28) minutes. By mid 2003 77.6% were receiving thrombolytic treatment within 30 minutes of arrival. The proportion treated within two hours of onset of symptoms increased from 32.5% to 40.3% (a difference of 7.8 percentage points, p < 0.0001). The use of secondary prevention medication for acute coronary syndromes increased over this period: angiotensin converting enzyme inhibitors, 62.4% to 72.4%; beta blockers, 76.3% to 82.6%; statins, 69.6% to 83.8%; and aspirin, 89.3% to 90.2%. CONCLUSION: The provision of contemporary online performance analyses has underpinned substantial improvement in the care of patients with acute coronary syndromes.

Left ventricular dysfunction, natriuretic peptides, and mortality in an urban population.

OBJECTIVE: To report the mortality of left ventricular systolic dysfunction (LVD), assessed objectively by echocardiography, and its association with natriuretic peptide hormones in a random sample of 1640 men and women aged 25-74 years from a geographical, urban population. METHODS: Left ventricular function was measured by echocardiography in 1640 attendees studied in 1992-3. LVD was defined as a left ventricular ejection fraction (LVEF) 30% (p < 0.001). The median (interquartile range) BNP concentration in those who died was 16.9 pg/ml (8.8-27) and 7.8 pg/ml (3.4-13) in survivors (p < 0.0001). Similarly, N-ANP had a median concentration of 2.35 ng/ml (1.32-3.36) in those with a fatal outcome and 1.27 ng/ml (0.9-2.0) in those alive at four years (p < 0.0001). Subjects with an LVEF /= 17.9 pg/ml compared with 6.8% if their BNP was below this concentration (p = 0.013). Multivariate analysis revealed the independent predictors of four year all cause mortality to be increasing age (p < 0.001), a BNP concentration >/= 17.9 pg/ml (p = 0.006), the presence of ischaemic heart disease (p = 0.03), and male sex (p = 0.04). CONCLUSIONS: LVD is associated with a considerable mortality rate in this population. BNP also independently predicts outcome. In addition to its role as a diagnostic aid in chronic heart failure and LVD, it provides prognostic information and clarifies the meaning of a given degree of LVD.

Catheter mounted coaxially moveable ablation electrode for the creation of linear transmural endocardial lesions.

INTRODUCTION: Use of a novel ablation catheter for the creation of linear transmural endocardial lesions, which uses a coaxially moving ablation electrode mounted on the terminal portion of a catheter shaft and able to move axially for a distance of up to 4 cm, is reported. METHODS AND RESULTS: The coaxially moving ablation electrode is moved by a sliding mechanism in the catheter handle. The distal portion of the catheter shaft is steerable. Bipolar or unipolar electrograms can be recorded from electrodes on the catheter tip and the coaxially moving ablation. Radiofrequency (RF) current is delivered to the coaxially moving ablation electrode with thermocouple temperature control. This ablation catheter was evaluated in five (30 to 65 kg) anesthetized pigs and introduced via the venous/arterial systems into the right and left atrium (1 lesion) (using the retrograde aortic approach). The catheter was maneuvered to bring the slide range into apposition with atrial endocardium. The coaxially moving ablation electrode was deployed to the terminal portion of the catheter's slide range and then withdrawn in 2-mm steps. RF current was delivered to the coaxially moving ablation electrode at each point (maximum temperature 70 degrees C). Postmortem examination of eight endocardial linear lesions (2.2 to 4.1 cm length) was made 1 to 3 hours after creation. Histopathologic examination confirmed transmural myocyte necrosis along the length of the lesion, that included the trabeculated right atrium. CONCLUSION: We conclude that a catheter using a moveable electrode creates continuous linear transmural lesions and could find clinical application in the therapy of a variety of reentry tachycardia mechanisms.

Lack of rebound during intermittent transdermal treatment with glyceryl trinitrate in patients with stable angina on background beta blocker.

OBJECTIVE: To assess whether intermittent transdermal treatment with glyceryl trinitrate causes clinically significant rebound in patients maintained on beta blockers for stable angina pectoris. DESIGN: Serial treadmill exercise testing in a double blind, randomised, placebo controlled cross over trial. Baseline exercise testing was performed at 0900 and 1100 at visit 1. Transdermal glyceryl trinitrate patches releasing 15 mg/24 h were applied at 2200 the evening before visits 2 and 3, and exercise testing was performed at 0900 the next morning. The patch was removed and replaced with either an identical patch or matching placebo and exercise tests were repeated two hours later. The alternative treatment was given at visit 3. SETTING: Tertiary referral centre. PATIENTS: 14 patients with stable angina pectoris maintained on beta blocker treatment alone. MAIN OUTCOME MEASURES: Time to angina, 1 mm ST segment depression, and total time, together with heart rate, systolic blood pressure, and rate-pressure product. RESULTS: Active treatment improved treadmill performance at 0900 and 1100. Time to angina, time to 1 mm ST segment depression, and total time fell significantly on placebo compared with the 0900 exercise test on active treatment, but were not significantly different to the baseline exercise test either. CONCLUSIONS: Intermittent transdermal treatment with glyceryl trinitrate is not associated with the rebound phenomenon in patients maintained on beta blockers for stable angina pectoris.

Cardiac stimulator for the study of refractory period control using current pulses of programmable duration and shape.

A programmable current stimulator has been developed that allows unipolar current pulses of complex shape, long duration and high current to be generated. The stimulator conforms to the safety requirements for devices connected directly to the heart. It incorporates additional safety features to prevent unintended current being delivered, even under fault conditions. The stimulator has been used to investigate the effects of long duration current pulses on the refractory period of cardiac tissue. The flexibility of the device suggests that it may well have uses in other fields of electrophysiology.

Relationship of the effective refractory period and monophasic action potential duration after a step increase in pacing frequency.

Adaptation of effective refractory period (ERP) and monophasic action potential (MAP) shortening after a step increase in drive frequency was determined at adjacent endocardial sites in the right ventricle of six patients without myocardial disease. ERP and MAP shortening occurred simultaneously. ERP shortening and MAP shortening were similar in time course in individuals, although the degree of shortening varied between individuals as the size of the step increase in pacing frequency varied. Shortening of both ERP and MAP was complete after a mean of 67 +/- 7.5 seconds. To allow group analysis, the percent change from baseline of action potential duration and ERP was calculated for each patient at intervals during adaptation and mean percent change for the group plotted against time from the beginning of the step rate increase. A mean step increase in pacing frequency of 49.3% of baseline for the group caused the ERP to shorten by a mean of 18.12%, and MAP90 by 17.43% of baseline. There was no significant difference (P = 0.05) between the action potential and ERP adaptation curves of the group. We conclude that in normal myocardium, there is a close relationship between shortening of ventricular ERP and action potential duration after a change in rate.

A comparison of isometric exercise, cold pressor stimulation and dynamic exercise in patients with coronary heart disease.

Isometric exercise and cold pressor stimulation have been proposed as alternatives to dynamic exercise in the evaluation of patients with coronary heart disease. We evaluated all three, by gated radionuclide ventriculography, in 13 male controls and 44 male patients with coronary heart disease. In controls, mean left ventricular ejection fraction did not change during isometric exercise or cold pressor stimulation (64 +/- 2 to 63 +/- 2 and 63 +/- 3) but fell significantly in patients (56 +/- 1 to 53 +/- 1 and 53 +/- 1, both P less than 0.001). During dynamic exercise, mean left ventricular ejection fraction rose in controls (64 +/- 2 to 84 +/- 2, P less than 0.001) but did not change in patients (56 +/- 1 to 56 +/- 2). There was considerable overlap between the groups in the left ventricular ejection fraction response to isometric exercise and cold pressor stimulation; only dynamic exercise discriminated between them. Isometric exercise and cold pressor stimulation are of little value in the diagnosis of coronary heart disease by radionuclide ventriculography.