Derek T. Connelly

An Entirely Subcutaneous Implantable Cardioverter–Defibrillator

BACKGROUND Implantable cardioverter-defibrillators (ICDs) prevent sudden death from cardiac causes in selected patients but require the use of transvenous lead systems. To eliminate the need for venous access, we designed and tested an entirely subcutaneous ICD system. METHODS First, we conducted two short-term clinical trials to identify a suitable device configuration and assess energy requirements. We evaluated four subcutaneous ICD configurations in 78 patients who were candidates for ICD implantation and subsequently tested the best configuration in 49 additional patients to determine the subcutaneous defibrillation threshold in comparison with that of the standard transvenous ICD. Then we evaluated the long-term use of subcutaneous ICDs in a pilot study, involving 6 patients, which was followed by a trial involving 55 patients. RESULTS The best device configuration consisted of a parasternal electrode and a left lateral thoracic pulse generator. This configuration was as effective as a transvenous ICD for terminating induced ventricular fibrillation, albeit with a significantly higher mean (+/-SD) energy requirement (36.6+/-19.8 J vs. 11.1+/-8.5 J). Among patients who received a permanent subcutaneous ICD, ventricular fibrillation was successfully detected in 100% of 137 induced episodes. Induced ventricular fibrillation was converted twice in 58 of 59 patients (98%) with the delivery of 65-J shocks in two consecutive tests. Clinically significant adverse events included two pocket infections and four lead revisions. After a mean of 10+/-1 months, the device had successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia. CONCLUSIONS In small, nonrandomized studies, an entirely subcutaneous ICD consistently detected and converted ventricular fibrillation induced during electrophysiological testing. The device also successfully detected and treated all 12 episodes of spontaneous, sustained ventricular tachyarrhythmia. (ClinicalTrials.gov numbers, NCT00399217 and NCT00853645.)

Radiofrequency ablation for persistent atrial fibrillation in patients with advanced heart failure and severe left ventricular systolic dysfunction: a randomised controlled trial

Objective To determine whether or not radiofrequency ablation (RFA) for persistent atrial fibrillation in patients with advanced heart failure leads to improvements in cardiac function. Setting Patients were recruited from heart failure outpatient clinics in Scotland. Design and intervention Patients with advanced heart failure and severe left ventricular dysfunction were randomised to RFA (rhythm control) or continued medical treatment (rate control). Patients were followed up for a minimum of 6 months. Main outcome measure Change in left ventricular ejection fraction (LVEF) measured by cardiovascular MRI. Results 22 patients were randomised to RFA and 19 to medical treatment. In the RFA group, 50% of patients were in sinus rhythm at the end of the study (compared with none in the medical treatment group). The increase in cardiovascular magnetic resonance (CMR) LVEF in the RFA group was 4.5±11.1% compared with 2.8±6.7% in the medical treatment group (p=0.6). The RFA group had a greater increase in radionuclide LVEF (a prespecified secondary end point) than patients in the medical treatment group (+8.2±12.0% vs +1.4±5.9%; p=0.032). RFA did not improve N-terminal pro-B-type natriuretic peptide, 6 min walk distance or quality of life. The rate of serious complications related to RFA was 15%. Conclusions RFA resulted in long-term restoration of sinus rhythm in only 50% of patients. RFA did not improve CMR LVEF compared with a strategy of rate control. RFA did improve radionuclide LVEF but did not improve other secondary outcomes and was associated with a significant rate of serious complications. Clinical trials registration number NCT00292162.

First prospective, multi-centre clinical experience with a novel left ventricular quadripolar lead

AIMS Cardiac resynchronization therapy (CRT) is sometimes complicated by elevated pacing thresholds and phrenic nerve stimulation (PNS), both of which may require that the coronary sinus lead be repositioned. The purpose of this study was to evaluate the performance of a novel quadripolar electrode lead and cardiac resynchronization therapy-defibrillator (CRT-D) device that enables electrical repositioning, potentially obviating a lead reposition procedure. METHODS AND RESULTS Patients indicated for CRT were enrolled and received a quadripolar electrode lead and CRT-D device (Quartetmodel 1458Q and Promote Q; St Jude Medical, Sylmar, CA, USA). Electrical data, and the presence of PNS during pacing from each left ventricular (LV) configuration, were documented at pre-hospital discharge and at 1 month. Seventy-five patients were enrolled and 71 were successfully implanted with a Quartetlead. Electrical measurements were stable over the follow-up period. Ninety-seven per cent (64 of 66) of patients had one or more programmable configurations with a threshold < 2.5 V and no PNS vs. 86% (57 of 66) if only conventional bipolar configurations were considered. Physicians were able to use the increased programming options to manage threshold changes and PNS. CONCLUSION The new quadripolar electrode LV lead provides more programming options to address common problems faced when managing CRT patients. Electrical measurements from new vectors are comparable with conventional configurations. Furthermore, 11% of patients in the study suffered PNS on all conventional bipolar vectors.

Early treatment with captopril after acute myocardial infarction.

OBJECTIVES--To determine the effects of early treatment with captopril on haemodynamic function, neuroendocrine biochemistry, left ventricular structure, clinical outcome, and exercise capacity over one year from acute myocardial infarction. DESIGN--Randomised, double blind, placebo controlled comparison of captopril and placebo. SETTING--Coronary care units and cardiology departments of two university teaching hospitals in Glasgow. PATIENTS--99 haemodynamically stable patients with acute myocardial infarction, selected on clinical grounds as being at risk of late ventricular dilatation. INTERVENTION--Captopril or identical placebo started between six and 24 hours after start of symptoms and continued for 12 months. Target maintenance dose was 25 mg three times a day. MAIN OUTCOME MEASURES--(a) Acute haemodynamic effects of treatment; (b) neuroendocrine biochemistry from admission to two months; and (c) change in echocardiographic measures of left ventricular size, clinical outcome, and exercise capacity after 12 months of treatment with a separate analysis of the effects of one month of treatment withdrawal on left ventricular volumes. RESULTS--Captopril caused acute reductions in mean (SEM) pulmonary artery pressure (2.48 (0.69) mm Hg) and systemic vascular resistance (260 (103)) dyn.s.cm-5). Over the first 10 hours captopril reduced mean arterial pressure by 12.1 (2.4) mm Hg compared with 3.8 (1.9) mm Hg in the placebo group. No patient had to be withdrawn from the captopril group because of hypotension. From day 1 onwards systolic and diastolic arterial pressures in the captopril treated group were slightly but not significantly lower than on placebo. There was no difference in the incidence of ventricular or supraventricular arrhythmia with treatment. Captopril prevented the day 3 peak in angiotensin II that occurred in the placebo group (peak concentration (interquartile range): 10.1 (4.8-19.4) pg/ml v 16.8 (4.3-46.3) pg/ml)) but had no effect on atrial natriuretic factor, arginine vasopressin, or catecholamines. Plasma atrial natriuretic factor remained above normal in both groups at two months after infarction. After one year left ventricular volume indices had increased less on captopril than on placebo: left ventricular end systolic volume index 5.4 ml/m2 v 14.7 ml/m2 (95% confidence interval (95% CI) of difference -14.6 to -3.9; p = 0.0011); left ventricular end diastolic volume index 8.4 ml/m2 v 19.0 ml/m2 (95% CI of difference, -17.0 to -4.2; p = 0.0016). Withdrawal of captopril for one month did not affect ventricular volumes. There was no difference in exercise capacity. CONCLUSIONS--Captopril started between six and 24 hours after acute myocardial infarction is not associated with significant hypotension. It suppresses activation of the renin angiotensin system but has no effect on plasma concentrations of other neurohormones. Atrial natriuretic factor remains raised at two months after myocardial infarction. Captopril significantly decreases left ventricular dilatation. This effect is not lost after one month of treatment withdrawal and is thus due to an alteration of left ventricular structure and not to a short lived haemodynamic action of captopril. Long-term treatment with captopril does not result in improved aerobic exercise capacity after acute myocardial infarction.

Why are patients in clinical trials of heart failure not like those we see in everyday practice

BACKGROUND/OBJECTIVES Evidence-based research has been criticized for not being relevant to the real world of patient care in the community, mainly because participants in research studies are dissimilar to those typically seen in every day practice. This article examines recruitment difficulties, and identifies the main reasons why patients with heart failure declined to participate in a research trial. METHODS Postal survey of potential trial participants (n=667), at time of recruitment. Analysis of (1) clinical and sociodemographic characteristics of respondents and nonrespondents to survey, and decliners and consenters to participation in a randomized controlled trial. RESULTS No significant differences were found between respondents and nonrespondents in respect to sociodemographic or clinical variables. Males (OR=1.58, CI=1.04-2.41), younger patients (OR=1.05, CI=1.03-1.08), and those prescribed an angiotensin converting enzyme (ACE) inhibitor (OR=1.68, CI=1.10-2.57) were significantly more likely to consent to participate. Main reasons for nonparticipation were perceptions of being too old, too unwell, or too busy. CONCLUSIONS Explanations of the purpose of research need to counter against perceptions among participants and clarify the benefits and disadvantages of participating in an intervention study when unwell. Study design should recognize that many elderly patients have busy lives and caring responsibilities. Financial support for participation should be considered.

Paced ventricular electrogram fractionation predicts sudden cardiac death in hypertrophic cardiomyopathy.

AIMS Paced electrogram fractionation analysis (PEFA) has been assessed for the prediction of sudden cardiac death (SCD) in a large-scale, prospective study of patients with hypertrophic cardiomyopathy (HCM). METHODS AND RESULTS We determined the positive predictive value (PPV) of PEFA in relation to other risk factors for SCD and outcomes in 179 patients with HCM and no prior history of cardiac arrest. Patients were followed over a mean 4.3 years (range: 1.1-6.3 years). Thirteen patients had SCD-equivalent events: four of these patients died suddenly, three were resuscitated from ventricular fibrillation (VF), and six had implantable cardioverter-defibrillator (ICD) discharges in response to VF. PEFA identified nine of these patients and another 14 non-VF patients yielding a censored PPV of between 0.19 and 0.59 that was greater than the PPV that was the formal stopping point of the trial (0.18). Eighty per cent of patients were followed for 4 years or more. The PPV for the identification of SCD in this group was 0.38 (0.17-0.59). The use of two or more conventional markers to predict SCD identified five patients with SCD-equivalent events in the 4-year follow-up group and 42 other patients without events yielding a PPV of 0.106 (confidence limits 0.02-0.15). CONCLUSION PEFA identifies HCM patients at risk of SCD with greater accuracy than non-invasive techniques and may have an important role in determining indications for ICD prescription.

Clinical Indications for Genetic Testing in Familial Sudden Cardiac Death Syndromes: an HRUK Position Statement

The sudden unexpected death of a young person can have profound implications for the surviving family members beyond those associated with bereavement and the immediate sense of loss. Among these other sequelae may be a concern that the sudden death was caused by a genetic condition and that other family members may suffer the same fate. Increased awareness of these inherited conditions and the transfer of the techniques of genetic testing from the research laboratory into the clinical arena make it possible to identify genetically affected individuals before they have symptoms or experience sudden cardiac death. The development of such tests has been paralleled by the emergence of preventative treatments, which have amplified the clinical importance of such tests. This document provides recommendations regarding the clinical indications for these tests based on the best available evidence.

Use of implantable cardioverter defibrillators in patients with left ventricular assist devices.

Patients with left ventricular assist devices (LVADs) are at high risk of sustained ventricular arrhythmias, but these may be remarkably well tolerated and the association with sudden death is unclear. Many patients who receive an LVAD already have an implantable cardioverter defibrillator (ICD). While it is standard practice to reactivate a previously implanted ICD in an LVAD recipient, this should include discussion of the revised risks and benefits of ICD therapy following LVAD implantation. In particular, patients should be warned that they might receive a significant number of ICD shocks that may not be life saving. When ICDs are reactivated, device programming should minimize the risk of repeated shocks for non‐sustained or well‐tolerated ventricular arrhythmias. Implantation of a primary prevention ICD after implantation of an LVAD is not supported by current evidence, poses potential risks, and should be the subject of a clinical trial before it becomes standard practice.

Implantable cardioverter-defibrillators.

Sudden cardiac death is a common problem, and increasing numbers of patients are surviving a first episode of a life threatening ventricular arrhythmia. In the absence of an acute myocardial infarction, patients who survive either ventricular fibrillation or sustained ventricular tachycardia have a high risk of further episodes, which may be fatal.1 Until recently, class I and class III antiarrhythmic drugs have been the standard treatment for patients with malignant ventricular arrhythmias. Amiodarone2 and sotalol3 have been shown to be superior to class I drugs, but despite using the best appropriate medical treatment, arrhythmia recurrence rates are still 40–50% at five years. There is now growing evidence to support the wider use of implantable cardioverter-defibrillators (ICDs) as primary treatment in certain patients with serious ventricular arrhythmias. These devices were developed in the 1970s, with the first human implant in 1980.4 Original devices had a single therapy option of defibrillation only; the generator was implanted in the abdomen, and thoracotomy was required for electrode placement. With advances in technology the units have become smaller (current ICDs are little bigger than a pacemaker) and can be implanted pectorally. With improvements in sensing, the latest devices offer graded therapeutic responses to a sensed ventricular arrhythmia. Antitachycardia pacing, low energy synchronised cardioversion, and high energy defibrillation shocks can be given via a single transvenous lead. Implantation of an ICD is now technically very straightforward, and only a little more complicated than pacemaker implantation. As with pacemaker implantation, strict attention to asepsis is necessary, and prophylactic antibiotics are generally used. In the past, ICD implants were performed under general anaesthesia; however, many centres now implant these devices using a combination of local anaesthesia and intravenous sedation. Usually an incision 5–8 cm in length is made in the left infraclavicular region, and a …

Effects of intravenous adenosine in patients with preexcited functional tachycardias: Therapeutic efficacy and incidence of proarrhythmic events

Abstract It is concluded that adenosine is effective in terminating preexcited junctional tachycardias, but may be complicated by serious proarrhythmic effects in these patients. These proarrhythmic effects of adenosine (1) preclude its use as the agent of first choice in the acute treatment of arrhythmias in which this diagnosis is suspected, and (2) highlight the need for continuous electrocardiographic monitoring and availability of direct-current cardioversion when adenosine is used as a diagnostic agent in wide-complex tachycardias of unknown origin.