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Objectives This study sought to prospectively evaluate the prevalence of cardiovascular abnormalities in patients with overt hyperthyroidism before and after antithyroid therapy. Background Overt hyperthyroidism is associated with recognized cardiovascular effects believed to be reversed by antithyroid therapy; however, increasing data suggest significant long-term cardiovascular mortality. Methods A total of 393 (312 women, 81 men) consecutive unselected patients with overt hyperthyroidism were recruited and compared with 393 age- and gender-matched euthyroid control subjects. Hyperthyroid patients were re-evaluated after antithyroid therapy. Findings in patients and matched control subjects were compared at presentation, after treatment when patients had subclinical hyperthyroidism biochemically, and when patients were rendered biochemically euthyroid. All had a structured cardiovascular history and examination, including measurements of blood pressure (BP) and pulse rate. All had resting 12-lead electrocardiogram and 24-h digital Holter monitoring of cardiac rhythm. Results A higher prevalence of cardiovascular symptoms and signs, as well as abnormal hemodynamic parameters, was noted among hyperthyroid patients at recruitment compared with control subjects. Cardiac dysrhythmias, especially supraventricular, were more prevalent among patients than among control subjects. Palpitation and dyspnea, postural decrease in systolic pressure, and atrial fibrillation (AF) remained more prevalent in treated hyperthyroid subjects with subclinical hyperthyroidism compared with control subjects, and remained more prevalent after restoration of euthyroidism. Predictors for successful reversion to sinus rhythm in those with AF associated with hyperthyroidism were lower BP measurements at recruitment and an initial hypothyroid state induced by antithyroid therapy. Mortality was higher in hyperthyroid subjects than in control subjects after a mean period of follow-up of 66.6 months. Conclusions Cardiovascular abnormalities are common in patients with overt hyperthyroidism at presentation, but some persist despite effective antithyroid therapy.

Patients with subclinical and treated overt hyperthyroidism have an excess vascular mortality rate. Several symptoms and signs in overt hyperthyroidism suggest abnormality of cardiac autonomic function that may account in part for this excess mortality rate, but few studies have examined cardiac autonomic function in untreated and treated hyperthyroidism. We assessed heart rate turbulence (HRT) and time-domain parameters of heart rate variability in a large, unselected cohort of patients with overt hyperthyroidism referred to our thyroid clinic (n = 259) and compared findings with a group of normal subjects with euthyroidism (n = 440). These measures were also evaluated during antithyroid therapy (when serum-free thyroxine and triiodothyronine concentrations returned to normal but thyrotropin remained suppressed (i.e., subclinical hyperthyroidism, n = 110) and when subjects were rendered clinically and biochemically euthyroid (normal serum thyrotropin, free thyroxine and triiodothyronine concentrations, n = 219). We found that overall measures of heart rate variability and those specific for cardiac vagal modulation were attenuated in patients with overt hyperthyroidism compared with normal subjects; measurements of overall heart rate variability remained low in those with low levels of serum thyrotropin but returned to normal in patients with biochemical euthyroidism. Measurements of HRT (onset and slope) were also decreased in patients with overt hyperthyroidism, but HRT slope returned to normal values with antithyroid treatment. This study is the first to evaluate HRT in overt and treated hyperthyroidism.

Selective site right ventricular pacing has been suggested as an approach to reduce the incidence of ventricular dysfunction and hopefully influence the morbidity resulting from traditional right ventricular apical pacing. Pacing from the right ventricular apex allows a stable ventricular rate, and together with atrial pacing and sensing, helps maintain atrioventricular synchrony but does not allow physiological activation of the left ventricle. Traditional atrial pacing sites like the right atrial appendage may encourage atrial tachyarrhythmias, whereas lead placement in right atrial septal sites may reduce the frequency of symptomatic atrial tachyarrhythmia episodes, especially when combined with prevention algorithms. Researchers attempting to pace the heart from these selective sites have been hindered by the lack of uniform definitions of where these sites actually lie and the inadequacy of tools to consistently reach these locations and verify correct placement. This lack of definition consensus may have contributed to the apparent conflict of data, particularly in the right ventricle. There is an urgent need for a standardization of terms and identifying measures for selective pacing sites.

Clinical evidence is accumulating that pacing from traditional right-sided sites (right ventricular apex and right atrial appendage) may be associated with long-term detriment to left ventricular function and promotion of atrial arrhythmias. Large numbers of small studies, some randomized, have addressed the effects of pacing from nontraditional or alternate sites, but the studies have varied in design such that comparison of results is often difficult. Many studies show data from acute studies only, although more recently longer-term data have started to become available; definition and description of pacing site also varies, adding further to the difficulties in comparing data. This article attempts to examine the randomized studies available to date, and to consider how future studies may contribute to our understanding of the effects of pacing from traditional and selected, specific sites on the right side of the heart.

Objectives We tested the hypothesis that left ventricular (LV) pacing is superior to right ventricular (RV) apical pacing in patients undergoing atrioventricular (AV) junction ablation and pacing for permanent atrial fibrillation. Background The potential benefit of LV over RV pacing needs to be evaluated without the confounding effect of other variables that can influence cardiac performance. Methods An acute intrapatient comparison of the QRS width and echocardiographic parameters between RV versus LV pacing was performed within 24 h after ablation in 44 patients. Both modes of pacing were also compared with pre-implantation values. Results Compared with RV pacing, LV pacing caused a 5.7% increase in the ejection fraction (EF) and a 16.7% decrease in the mitral regurgitation (MR) score; the QRS width was 4.8% shorter with LV pacing. Similar results were observed in patients with or without systolic dysfunction and/or native left bundle branch block, except for a greater improvement in MR in the latter group. Compared with pre-ablation measures, the EF increased by 11.2% and 17.6% with RV and LV pacing, respectively; the MR score decreased by 0% and 16.7%; and the diastolic filling time increased by 12.7% and 15.6%. Conclusions Rhythm regularization achieved with AV junction ablation improved EF with both RV and LV pacing; LV pacing provided an additional modest but favorable hemodynamic effect, as reflected by a further increase of EF and reduction of MR. The effect seems to be equal in patients with both depressed and preserved systolic functions and in those with and without native left bundle branch block.

Recent work has shown no difference in change of LVEF between RV apical (RVA) pacing and non-RVA pacing in patients with normal LV function. We hypothesised that a more sensitive marker (global longitudinal strain, GLS) could identify a detrimental effect of RVA and that assessment of deformation could identify whether dyssynchrony, contraction inefficiency and regional LV impairment were responsible for functional changes.In this substudy of Protect-PACE (The Protection of Left Ventricular Function During Right Ventricular Pacing. Does Right Ventricular High-septal Pacing Improve Outcome Compared With Right Ventricular Apical Pacing?), a randomised controlled trial of RVA and non-RVA pacing in pacemaker-dependent patients with preserved EF, 145 patients (76 with RVA) with echocardiograms of sufficient quality underwent measurement of LV longitudinal strain (GLS) from speckle tracking just after implantation and at 2 years. LV dyssynchrony, discoordination and regional apical longitudinal strain were also measured.Pacing was associated with reduced GLS after 2 years, although 2-year GLS was lower in RVA (-13.9 ± 4.1 vs -15.5 ± 4.6, p = 0.02). RVA was an independent correlate of ΔGLS, although there was a minor difference in ΔGLS between the RVA and non-RVA groups (-1.8 ± 3.6 vs -0.8 ± 3.4%, p= 0.07), reflecting impairment of GLS at baseline in RVA. Apical strain was significantly lower in RVA than those in non-RVA at baseline and 2 years (both p0.01). Dyssynchrony and discoordination parameters at 2 years also showed significant deterioration in RVA. Apical strain, dyssynchrony and discoordination parameters at 2 years were significantly associated with ΔGLS.Inefficient dyssynchronous contraction and the decrease in apical strain appear to be associated with global LV impairment in RVA.PROTECT-PACE ClinicalTrials.gov number NCT00461734.

Hyperthyroidism is a common disorder affecting multiple systems in the body. The cardiovascular effects are among the most striking. The availability of effective treatments for hyperthyroidism has led to the widespread perception that it is a reversible disorder without any long-term consequences. Recent evidence suggests, however, that there may be adverse outcomes. Long-term follow-up studies have revealed increased mortality from cardiovascular and cerebrovascular disease in those with a past history of overt hyperthyroidism treated with radioiodine, as well as those with subclinical hyperthyroidism. Thyroid hormones are known to exert direct effects on the myocardium, as well as the systemic vasculature and predispose to dysrhythmias, especially supraventricular. Atrial fibrillation (AF) is a recognized complication of overt hyperthyroidism, and subclinical hyperthyroidism is also known to be a risk factor for development of AF. Supraventricular dysrhythmias, particularly atrial fibrillation, in older patients may account for some of the excess cardiovascular and cerebrovascular mortality described, especially because AF is known to predispose to embolic phenomena.

Thyroid hormones exert important effects on the cardiovascular system, including effects on cardiac systolic and diastolic function, peripheral vascular resistance and arrhythmogenesis. Hyperthyroidism and hypothyroidism often cause opposing effects on cardiovascular physiology in the short term. Increasing evidence suggests that long-term vascular morbidity and mortality occurs in both overt and subclinical thyroid disease.

Paul Zoll first applied clinically effective temporary cardiac pacing in 1952 using a pulsating current applied through two electrodes attached via hypodermic needles to the chest wall in two patients with ventricular standstill.1 Although this technique was uncomfortable for the patients it was effective for 25 minutes in one patient and nearly five days in the second; this report heralded the ability to provide temporary ventricular rate support for patients with clinically significant bradycardia. Subsequent technological developments have provided endocardial, epicardial, and gastrooesophageal approaches to temporary cardiac pacing in addition to the refinement of external pacing. All approaches, however, are based on the provision of rate support from an external pulse generator via an electrode or electrodes which can be removed easily after a short period of pacing, as many of the situations requiring temporary pacing are transient and resolve spontaneously or have a correctable underlying cause. In a selected group of patients, permanent pacing treatment will need to be instigated before removal of the temporary system. The indications for temporary pacing can be considered in two broad categories: emergency (usually associated with acute myocardial infarction) or elective. There is, however, no clear consensus on indications for temporary pacing with most recommendations coming from clinical experience rather than scientific trials.2 For many patients presenting with bradycardia, however, conservative therapy and treatment of the underlying problem is the most appropriate management strategy. As a general rule, patients who may need to go on to permanent pacing should only have a temporary transvenous pacing wire placed if they have suffered syncope at rest, are haemodynamically compromised by the bradycardia or have ventricular tachyarrhythmias in response to bradycardia. In particular, patients presenting with sinus node disease rarely need temporary pacing, and the risks of infection and compromise of subsequent venous access …

Atrioventricular junctional (AVJ) catheter ablation followed by pacemaker implantation is now widely accepted for patients affected by paroxysmal atrial fibrillation (PAF) not controlled by antiarrhythmic drugs. However, few data exist on its indications, optimal methodology and complications. Therefore a study group examined current practice in Europe and North America, using a questionnaire, followed by a Study Group Meeting to discuss the results. Based upon this, class I, class II and class III indications were proposed. Class I indications (for which general agreement existed) include drug-refractory PAF, correlating with important symptoms, the bradycardia–tachycardia syndrome already treated with a pacemaker, and continued PAF. Large differences exist in the current methodology, but consensus was reached on the technical approaches of right and left-sided AVJ ablation, and on the timing of pacemaker implant in relation to ablation. No complete agreement was reached on technical features such as catheter choice and heparin use. The recommended pacing mode was DDDR with mode switching.

Aims Various mode-switching algorithms are available with different tachyarrhythmia detection criteria to be satisfied to initiate mode-switching. This study evaluated three different mode-switching algorithms in patients with paroxysmal atrial fibrillation. Methods and Results Seventeen patients completed the study. Three mode-switching algorithms were downloaded as software into the pacemaker, each for 1 month in a single-blind, randomized sequence. The criteria to initiate mode-switching were: mean atrial rate (‘standard’), ‘4-of-7’ or ‘1-of-1’ atrial intervals to exceed the atrial detection rate. Symptoms for each were measured using the Symptom Checklist–Frequency and Severity index. The median number of mode-switch episodes increased from 20 for ‘standard’ to 39 for ‘4-of-7’ (P=0·029 vs ‘standard’) and 103 for ‘1-of-1’ (P=0·0012 vs ‘standard’) onset criteria. Median duration of episodes decreased from 2·5 min with ‘standard’ to 1·4 min with ‘4-of-7’ and 0·4 min with ‘1-of-1’ onset criteria. Frequency of symptoms was lower using ‘4-of-7’ (18·2±12·0 vs 23±12·0, P=0·08) or ‘1-of-1’ (20·4±12·4 vs 23±12·0, P=0·07) than ‘standard’ onset criteria. Severity of arrhythmia tended to be less with either ‘4-of-7’ (16±10·4 vs 19·1±19·4, P=0·12) or ‘1-of-1’ (17·5±10·3 vs 19·1±9·4, P=0·18) than with ‘standard’ onset criteria. Conclusions The more sensitive onset criteria for detection of atrial tachyarrhythmias were associated with lower frequency and severity of symptoms.

This study examined the effectiveness of cardiac pacing using the Thera DR rate-drop response algorithm for prevention of recurrent symptoms in patients with carotid sinus syndrome (CSS) or vasovagal syncope. The algorithm comprises both diagnostic and treatment elements. The diagnostic element consists of a programmable "window" used to identify heart rate changes compatible with an evolving neurally mediated syncopal episode. The treatment arm consists of pacing at a selectable rate and for a programmable duration. Forty-three patients (mean age 53 +/- 20.4 years) with CSS alone (n = 8), CSS in conjunction with vasovagal syncope (n = 4), or vasovagal syncope alone (n = 31) were included. Thirty-nine had recurrent syncope, while the remaining four reported multiple presyncopal events. Prior to pacing, 40 +/- 152 syncopal episodes (range from 1 to approximately 1,000 syncopal events) over the preceding 56 +/- 84.5 months. Postpacing follow-up duration was 204 +/- 172 days. Three patients have been lost to follow-up and in one patient the algorithm was disabled. Among the remaining 39 individuals, 31 (80%) indicated absence or diminished frequency of symptoms, or less severe symptoms. Twenty-three patients (23/29, or 59%) were asymptomatic with respect to syncope or presyncope. Sixteen patients had symptom recurrences. Of these, seven experienced syncope (7/39, or 18%) and 9 (29%) had presyncope: the majority of patients with recurrences (6/7 syncope and 7/9 presyncope) were individuals with a history of vasovagal syncope. Consequently, although symptoms were observed during postpacing follow-up, they appeared to be of reduced frequency and severity. Thus, our findings suggest that a transient period of high rate pacing triggered by the Thera DR rate-drop response algorithm was beneficial in a large proportion of highly symptomatic patients with CSS or vasovagal syncope.

OBJECTIVES: To define the effects of long-term thyroxine treatment upon heart rate, blood pressure, left ventricular systolic function, and left ventricular size, as well as indices of autonomic function, and to compare findings with those in patients with thyrotoxicosis before and during treatment. DESIGN: Cross sectional study of patients prescribed thyroxine long term (n = 11), patients with thyrotoxicosis studied at presentation (n = 23), compared with controls (n = 25); longitudinal study of patients with thyrotoxicosis studied at presentation and serially after beginning antithyroid drug treatment (n = 23). METHODS: 24 h ambulatory monitoring of pulse and blood pressure, echocardiography, forearm plethysmography, and autonomic function tests. RESULTS: Long-term thyroxine treatment in doses that reduced serum thyrotrophin to below normal had no effect on blood pressure, heart rate, left ventricular systolic function or stroke volume index, but was associated with an 18.4% increase in left ventricular mass index (mean (SEM) 101.9 (3.09) g/m2 v controls 86.1 (4.61), P < 0.01). Thryoxine treatment, like thyrotoxicosis, had no effect on tests of autonomic function. Untreated thyrotoxicosis resulted in pronounced changes in systolic and diastolic blood pressure and an increase in heart rate during waking and sleep. Patients with thyrotoxicosis at presentation had an increase in left ventricular systolic function (ejection fraction 70.5 (1.66)% v 65.4 (1.79), P < 0.01; fractional shortening 40.4 (1.54)% v 35.6 (1.46), P < 0.01), increased stroke volume index (45.9 (2.4) ml/m2 v 36.6 (1.7), P < 0.001), and an increase in forearm blood flow, and decrease in vascular resistance. They had a similar degree of left ventricular hypertrophy to that associated with thyroxine treatment (99.3 (4.03) g/m2); all changes were corrected within 2 months by antithyroid drugs. CONCLUSIONS: The development of left ventricular hypertrophy in patients receiving thyroxine in the absence of significant changes in heart rate, blood pressure, and left ventricular systolic function is consistent with a direct trophic effect of thyroid hormone on the myocardium. The presence of left ventricular hypertrophy determines that further studies are essential to assess cardiovascular risk in patients taking thyroxine long term.

The evolution of upright posture is usually considered an advantage in humans. For people with postural tachycardia syndrome (PoTS) it can present a daily challenge. Although orthostatic intolerance is often associated with older people, PoTS tends to affect young women who present with multiple, non-specific symptoms and significant functional impairment.1 PoTS was characterised in 1993,2 but previously existed under various names including irritable heart, soldier's heart, and idiopathic orthostatic intolerance. It is a heterogeneous group of disorders sharing similar characteristics as a consequence of abnormal autonomic nervous system response to assuming upright posture. When humans stand up, approximately 500 ml of blood descends from the thorax into the abdominal cavity and limbs. A normal autonomic nervous system responds with immediate peripheral vasoconstriction, increase in heart rate of 10–20 beats per minute (bpm), and minimal change in blood pressure.1 In patients with PoTS this mechanism does not respond appropriately; the exact pathophysiology remains unclear.3 A likely mechanism is inadequate vasoconstriction on standing, resulting in pooling of blood in splanchnic and peripheral vasculature. Heart rate and catecholamine levels increase further to compensate. Symptoms of cerebral hypoperfusion including dizziness and syncope occur, often in the presence of normal blood pressure. Ironically, some patients with PoTS have a hypertensive response to standing.1 Diagnosis is usually made following a tilt table test or 10-minute stand test. The definition is arbitrary, but agreed by consensus (Box 1).4 Heart rate increases but, by definition, blood pressure does not necessarily drop. However, there is overlap with neurally mediated hypotension and some …

This article contains an overview of the pathophysiology and aetiological factors in angina pectoris, and a review of current strategies for the management of the patient with both stable and unstable angina. In particular, the role of contemporary revascularisation therapy in angina (aorto-coronary bypass surgery or coronary angioplasty) is analysed.

In the early 1950s, Dr Aubrey Leatham established a cardiac unit at St. George's Hospital, Hyde Park Corner, London. He developed and taught the essential clinical skill of cardiac auscultation. Under his guidance a clinical department for the care of cardiac patients was developed and coupled to physiological academic research. He was a pioneer in cardiac pacing and, in 1961, Harold Siddons, O'Neal Humphries, and Aubrey Leatham implanted the first 'indwelling' pacemaker in the UK in a 65-year-old man with repeated Stokes-Adams attacks due to complete heart block. The nickel-cadmium 'accumulator', which powered the pacemaker, had to be recharged once a week.

BACKGROUND: Previous studies have suggested that minor changes in thyroid function are associated with risk of atrial fibrillation (AF). Our objective was to determine the relationship between thyroid function and presence of atrial fibrillation (AF) in older subjects. METHODS: A population-based study of 5860 subjects 65 years and older, which excluded those being treated for thyroid dysfunction and those with previous hyperthyroidism. Main outcome measures included tests of thyroid function (serum free thyroxine [T(4)] and thyrotropin [TSH]) and the presence of AF on resting electrocardiogram. RESULTS: Fourteen subjects (0.2%) had previously undiagnosed overt hyperthyroidism and 126 (2.2%), subclinical hyperthyroidism; 5519 (94.4%) were euthyroid; and 167 (2.9%) had subclinical hypothyroidism and 23 (0.4%), overt hypothyroidism. The prevalence of AF in the whole cohort was 6.6% in men and 3.1% in women (odds ratio, 2.23; P

Tilt testing is accepted as the main tool for the diagnosis of neurocardiogenic syncope, particularly in the "malignant" vasovagal form. As a result of experience with tilt testing, the cardiovascular responses to head-up tilting in patients with malignant vasovagal syncope (MVVS) have been defined in respect of the vasodepressor (hypotensive) and cardioinhibitory (bradycardic) components. Pacing therapy has been of limited value in the past, with controversy about its role, even in the cardioinhibitory form of MVVS. With the advent of more sophisticated algorithms for pacing (i.e., rate-drop response [RDR], Thera DR) in response to the onset of bradycardia in MVVS, however, this therapy is being reexamined. This article examines the blood pressure and heart rate responses to head-up tilt in patients with MVVS and examines the role of this test in screening such patients for the benefits of pacing with RDR. Careful analysis of the pattern of blood pressure and heart rate response during the tilt test may allow selection of those patients likely to respond to RDR and may provide useful information for initial programming of the algorithm.

Aims Left ventricular (LV) and biventricular (BiV) pacing are potentially superior to right ventricular (RV) apical pacing in patients undergoing atrioventricular (AV) junction ablation and pacing for permanent atrial fibrillation. Methods and results Prospective randomized, single-blind, 3-month crossover comparison between RV and LV pacing (phase 1) and between RV and BiV pacing (phase 2) performed in 56 patients (70±8 years, 34 males) affected by severely symptomatic permanent atrial fibrillation, uncontrolled ventricular rate, or heart failure. Primary endpoints were quality of life and exercise capacity. Compared with RV pacing, the Minnesota Living with Heart Failure Questionnaire (LHFQ) score improved by 2 and 10% with LV and BiV pacing, respectively, the effort dyspnoea item of the Specific Symptom Scale (SSS) changed by 0 and 2%, the Karolinska score by 6 and 14% ( P

Introduction: Previous studies have suggested that long-term right ventricular apex (RVA) pacing causes dyssynchronous left ventricular (LV) contraction, promoting heart failure and increasing mortality. Placing a lead against the right ventricular high septum (RVHS) allows closer proximity to the His-Purkinje system and therefore may allow more physiological depolarisation of the left ventricle. However, recent clinical studies regarding the influence of pacing sites on LV function have produced conflicting results. Objectives: We hypothesized that RVA pacing would worsen myocardial deformation more than than RVHS pacing. Methods: In this multicenter, randomized controlled trial of 240 pts (74 11yrs, 67% males) with preserved LVEF and implanted pacemaker due to high grade atrioventricular block, deformation imaging was possible in 148 pts, of whom 78 were randomized to RVA and 70 to RVHS. We measured LVEF and global longitudinal strain (GLS) using speckle tracking (EchoPAC PC BT11: GE Healthcare, QLAB version 9.1: Philips Medical Systems) at baseline (post pacemaker implantation) and at two years. Results: In the RVA group, the mean LVEF at baseline was 56.8 8.5% and at two years was 53.6 9.6 (p1⁄40.002) and in the RVHS baseline LVEF was 55.8 10.1 and at two years 53.2 10.4 (p1⁄40.013). In the RVA group, the mean GLS at baseline was -15.9 4.0% and at two years was -13.9 4.0 (p

Dr Faizel Osman and colleagues (July 2001 JRSM, pp. 346-348) present two cases of thyrotoxicosis with heart block. For the second patient, who responded well only to steroid therapy, they raise the question whether the triad of thyrotoxicosis, heart block and raised erythrocyte sedimentation rate could be due to a single autoimmune disease; yet they do not say whether this was investigated or not.

All patients with permanent AF in whom a clinical decision has been made to undertake complete AV junctional ablation and ventricular pacing (conventional indication for ‘ablate and pace’) Patients with permanent AF, drug-refractory heart failure, uncontrolled ventricular rate and left bundle branch block (LBBB) pattern or non-specific intraventricular conduction defect (IVCD) (QRS 150 ms) in whom a clinical decision has been made to undertake left ventricular synchronization pacing (consistent with previous investigational indications for BiV pacing).

Pacing for the relief of bradycardia might be considered a ‘mature’ therapy, having now been available for 50 years, so it is refreshing to see that there are still many unanswered questions relating to the practice of pacing the ventricle. Although it seems clear from population-based studies that ventricular pacing increases the risk of left ventricular dysfunction and that the cumulative percentage of pacing is directly related to that risk,1 it is unclear whether it is simply pacing the ventricle or the site of ventricular pacing that is the real problem. Perhaps, the most compelling evidence that right ventricular (RV) apical pacing may be deleterious came from the DAVID study2 which compared back-up VVI pacing at 40 ppm and DDDR pacing at 70 ppm. The VVI group did not require much ventricular pacing compared with the DDDR group. Although many patients had impaired LV function, only 12% had NYHA class III or IV symptoms and patients who were paced more frequently were more likely to have an adverse outcome in terms of heart failure. The debate about RV pacing is further confused by clinical anecdote (many patients seem to remain perfectly well despite RV apical pacing) and variable results from previous studies.3–5 These discrepancies have usually been put down to duration of pacing, differences in study design, variation in pacing site studied, and inadequate duration of …

As the indications for implantable cardiac devices [pacemakers, cardioverter-defibrillators (ICDs), and cardiac resynchronization systems (CRT)] have been extended over the last decade, the need for elective external cardioversion (ECV) in patients with such devices and concurrent atrial fibrillation (AF) has also increased. In addition, the overall requirement for ECV has also been extended by the increasing age of the population in most developed countries and a more aggressive approach to the management of recent-onset and haemodynamically compromising AF.1 The use of ECV in patients with implanted devices has long been a cause for concern with regard to the potential for adverse effects on the generator and/or leads, with the result that this simple and effective therapy may have been delayed or even denied to some patients. These concerns were largely fuelled by a number of reports in the 1970s and 1980s suggesting the potential for device interference or lead failure.2,3 Devices implanted within the last decade, however, are considerably more sophisticated, more likely to use bipolar lead configurations, and better protected against external interference than those of the period from which these reports arose, leaving the question of safety in patients with modern implantable devices open. In addition, ECV has evolved over recent years with the development of equipment able to deliver biphasic shocks resulting in an increased efficacy and lower energy requirements. As CRT has … Corresponding author. Tel: +44 121 697 8338; fax: +44 121 414 3713. E-mail address : m.d.gammage{at}bham.ac.uk

Thyroid hormones exert direct effects upon the heart and indirect influences mediated via changes in cardiac work. Overt thyroid dysfunction is frequently associated with cardiovascular symptoms and signs and less frequently with significant cardiovascular morbidity due to atrial fibrillation or cardiac failure. Whether subclinical thyroid dysfunction is similarly associated with adverse effects upon the cardiovascular system remains unclear.

The pacing rates from accelerometer-based (Excel) and piezoelectric-based (Legend) activity sensing rate adaptive pacemakers, both strapped externally in the pectoral position, were compared with sinus rate response in normal volunteers of two different age groups (group 1, mean age 35 +/- 16 years; group 2, mean age 72 +/- 9 years) during various physical activities. Both pacemakers were programmed in manufacturers' nominal rate adaptive settings. Both types of activity sensing pacemakers programmed in this way showed chronotropic deficiencies to metabolic demand in healthy young subjects and in those matching the usual age of pacemaker implant, especially during "burst" activities. These data suggest that present recommended activity sensing rate response algorithms for accelerometer and piezoelectric pacemakers are inappropriate for many physical activities.

Thyrotoxicosis results in a number of effects on the cardiovascular system including changes in blood pressure, peripheral vascular resistance and left ventricular mass. Whilst many of these are well documented, the reversibility of these changes with restoration of euthyroidism is less clear and may have prognostic implications. In addition, patients who have undergone thyroidectomy for thyroid carcinoma require chronic high-dose thyroid hormone therapy; the cardiovascular effects of this therapy have not been assessed with regard to long term risk. We studied 23 female patients with Graves’ hyperthyroidism (group 1) with no prior history of heart disease at presentation and after 1 and 2 months of carbimazole treatment and 11 female patients receiving doses of thyroxine sufficient to suppress thyroid stimulating hormone (TSH) to below normal values (group 2); data were compared to those from 25 normal female age matched controls. Cardiac dimensions and function were assessed by 2-dimensional and M-mode echocardiography, 24 hour blood pressure and heart rate by automatic ambulatory sphygmomanometer. At presentation, group 1 showed increases in mean 24 hour systolic blood pressure (124 ± 12.4 v 110 ± 6.7 mmHg, p l 0.05) (mean ± SD), mean 24 hour heart rate (99.0 ± 14.4 v 77.0 ± 9.4/min, p l 0.001) and left ventricular mass index (LVMI) (93.1 ± 12.2 v 78.9 ± 9.0 g/m 2 , p l 0.03) compared to controls. Fractional shortening (FS) and ejection fraction (EF) were increased (FS: 39.7 ± 2.1 v 35.8 ± 1.9%, p l 0.05) (EF: 69.8 ± 1.3 v 65.7 ± 1.5%, p l 0.05). All of these indices had returned to normal, however, after 2 months of carbimazole treatment. In group 2, the only abnormality was a significant increase in LVMI compared to controls (100.3 ± 25.9 v 78.9 ± 9.0 g/m 2 p l 0.05). Diurnal variation in systolic and diastolic blood pressure and heart rate were normal in both groups. There were no changes in either group in assessments of sympathetic activity (tilt testing, isometric forearm exercise, cold pressor test and Valsalva ratio) or in 24 hour urinary catecholamines compared with controls, or between presentation and 2 months in group 1. Conclusion The cardiovascular effects of thyrotoxicosis are reversed rapidly in response to antithyroid treatment with carbimazole; despite the similarities between thyrotoxicosis and a hyperadrenergic state, our data show no objective evidence to suggest sympathetic overactivity. Patients receiving suppressive doses of thyroid hormones show evidence of increased left ventricular mass; this finding warrants long-term follow up to assess prognostic implications in terms of future cardiovascular risk.

Successful dual chamber pacing was achieved by implanting permanent pacemaker leads using an extra-peritoneal approach to the inferior vena cava in a 48-year-old patient with a single ventricle, transposition of the great vessels, and a right atrial pulmonary artery shunt (Glenn's procedure). The pacemaker generator was implanted into a subcutaneous pockel in the anterior abdominal wall.

In order to assess the value of a simple, single setting rate response option to VVI pacing, 12 patients (mean age 75.1 ± 6,2, range 62–83 years, seven males, five females) with symptomatic complete heart block were entered into a double-blind, randomized crossover trial of VVI versus VVIR (single setting rate responsive) pacing using Medtronic Activitrax pacemakers. Assessment was by time taken in seconds (sec) and Borg scale symptom score (6–20) for simple activities (standing from chair x 30; walking 800 meters; 52 steps on stairs [slow and fast pace], and incremental, noninclined maximal treadmill exercise), performed after a 4-week period with the patient in each pacing mode. Times were significantly improved in VVIR mode for standing from chair [mean ± SD] (78.7 ± 22.5 vs 70.7 ± 19.5 sec; P < 0.05), for 800 m walk (1032 ± 80 vs 885 ± 59 sec; P < 0.05), fast ascent of stairs (29.5 ± 7.7 vs 26.5 ± 5.6 sec; P < 0.02), and treadmill exercise (626.7 ± 189.5 vs 741.0 ± 170.2 sec, P < 0.005) although no difference in time for slow stair ascent was demonstrated. Symptom scores were significantly less in VVIR for standing from chair (12.7 ± 2.8 vs 10.3 ± 1.8; P < 0.01), 800 m walk (10.9 ± 2.7 vs 9.0 ± 2.4; P < 0.01), slow ascent of stairs (11.6 ± 2.1 vs 10.0 ± 2.0; P < 0.01), and fast ascent of stairs (13.0 ± 2.0 vs 11.7 ± 1.9; P < 0.02) but unchanged for treadmill exercise. Single setting VVIR pacing increases maximum exercise capacity and decreases perceived difficulty of submaximal exercise in elderly patients with symptomatic heart block. This would be a beneficial addition to most limited and multiprogrammable VVI systems for use in the elderly.

The British Pacing and Electrophysiology Group guidelines for pacemaker prescription recommend single chamber atrial pacing as the most appropriate pacing mode for sinus node disease in the absence of atrioventricular conduction disturbance.1 As such it offers a rare combination of maximum clinical effectiveness for the minimum cost and a good training opportunity. However, it seems that this message has yet to be translated into pacing practice in the UK. In this issue of Heart , Clarke et al retrospectively analyses the pacing activity for sinus node disease in a tertiary pacing centre over five years.2 They conclude that in their centre £103 000 per year could have been saved by more judicious use of AAI pacing, largely by reducing the DDD implant rate. It seems likely that these potential savings are equally applicable to the rest of the UK. Current pacemaker prescribing for sinus node disease is frequently illogical, ignores current evidence, and misses out on training opportunities for junior staff. The evidence to support atrial based pacing for sinus node disease, rather than single chamber ventricular pacing, is very strong. Numerous retrospective studies have demonstrated that mortality and morbidity are greater in ventricular only paced patients,3-5 and that the progression to chronic atrial fibrillation (AF) is less common in patients with atrial based pacing.3-10 Although these data may be criticised for the potential biases inherent in retrospective studies, since 1994 data have been available from the first prospective randomised study.11 Andersen et al were able to demonstrate a reduction in the frequency of AF and incidence of thromboembolism (5% v 18%) with atrial pacing after three years of follow up. The most recent analysis of this study (at 5.5 years of follow up) has also shown a significant reduction in all cause mortality (35.5% v …

Part 1. Indications for ablate and pace treatment: evidence of eYcacy 1. Prospective, randomized study of AV ablation and mode-switching, dual-chamber pacemaker implantation medical therapy in drug-resistant PAF — Michele Brignole, MD (Lavagna, Italy) 2. Prospective, randomized study of AV ablation and mode-switching, dual-chamber pacemaker implantation using two diVerent algorithms vs drug therapy in patients with PAF — Howard Marshall, MD (Birmingham, U.K.) 3. Experience with the North American Ablate and Pace Registry — Mark Wood, MD (Richmond, Virginia, U.S.A.)

The clinical impact of thallium-201 (Tl-201) scintigraphy in coronary artery disease was reviewed in 162 consecutive patients referred for routine investigation. Normal Tl-201 images were obtained in 86 of the 102 studies undertaken for diagnostic purposes. Eighty-one (94%) of the 86 were spared diagnostic coronary arteriography; 5 proceeded to coronary arteriography for persistent symptoms (1 had double vessel disease, 2 had single vessel disease only, 2 had normal arteriograms). Conversely, coronary arteriography was normal in 2 of 16 patients (12.5%) with unequivocal image defects. Tl-201 scintigraphy was performed as a functional complement to coronary arteriography in 60 patients, influencing the decision for surgery in 36 and determining the presence or absence of myocardial ischaemia in 24 patients with equivocal coronary arteriograms. Normal data were obtained in 9 patients. Of the 95 patients with normal Tl-201 scintigrams, only 5 (5.2%) required further investigations or intervention (4 arteriograms, 1 coronary angioplasty) over a follow-up period of 18 +/- 1 months, none suffered myocardial infarction and none died. There were no deaths in either the diagnostic or complementary group, irrespective of the result of the Tl-201 scintigram, during the mean follow-up period of 18 months. These data confirm both the valuable role of Tl-201 scintigraphy in the management of patients with suspected or proven coronary artery disease and the excellent prognostic value of a normal Tl-201 scintigram.

1. Subjects followed serially after acute myocardial infarction demonstrated a rapid and sustained fall in serum total tri-iodothyronine (T3) concentration and a rise in reverse tri-iodothyronine (rT3) concentration. There was a transient fall in total thyroxine (T4) concentration. 2. Thyroxine binding globulin (TBG) levels were unchanged after acute myocardial infarction but prolonged falls were observed in thyroxine binding prealbumin (TBPA) and albumin concentrations. 3. In contrast to the fall in total T4, both measured and calculated free T4 concentrations were unchanged but measured and calculated free T3 concentrations fell as did total T3. 4. Despite the observed fall in T3, basal thyrotrophin (TSH) concentrations did not rise. 5. The reduction in circulating T3 levels after acute myocardial infarction suggests that a hypothyroid state exists. Until tissue thyroid status can be assessed directly, however, this conclusion must remain in doubt.

Two years after an orthotopic cardiac transplant a 28 year old man was found to have clinically significant stenosis of the right coronary artery at routine coronary angiography. This lesion was accompanied by a perfusion defect on exercise thallium scintigraphy. Percutaneous transluminal coronary angioplasty of the lesion improved the angiographic appearance of the stenosis and reduced the exercise thallium perfusion defect.