Laser-assisted lead extraction: the European experience.

AIMS: The aim of this study is to investigate the safety and effectiveness of Excimer laser-assisted lead extraction in Europe. The final European multi-centre study experience is presented. METHOD AND RESULTS: The Excimer is a cool cutting laser (50 degrees C) with a wavelength of 308 nm. The energy is emitted from the tip of a flexible sheath and is absorbed by proteins and lipids, 64% of the energy is absorbed at a tissue depth of 0.06 mm. The sheath is positioned over the lead, and the fibrosis surrounding the lead is vaporized while advancing the sheath without damaging other leads. From August 1996 to March 2001, 383 leads (170 atrial, 213 ventricular) in 292 patients (mean age 61.6 years, range 13-96) were extracted at 14 European centres. Mean implantation time was 74 months (3-358). Most frequent indications were pocket infection (26%), non-functional leads (21%), patient morbidity (21%), septicaemia or endocarditis (14%), erosion (5%), and lead interference (8%). Median extraction time was 15 min (1-300). Complete extraction was achieved in 90.9% of the leads and partial extraction in 3.4%. Extraction failed in 5.7% of the leads. Major complications = perforations caused 10/22 (3.4/5.7%) of the failures. Most partially extracted patients were considered clinically successful, as only minor lead parts without clinical significance were left. Femoral non-laser technique was used to remove 8/12 of the non-complication failures. The total complication rate, including five minor complications (1.7%), was 5.1%. No in-hospital mortality occurred. CONCLUSION: Pacing and implantable cardioverter-defibrillator leads can safely, effectively, and predictably be extracted. Open-heart extractions can be limited to special cases. The results indicate that the traditional policy of abandoning redundant leads, instead of removing them, may be obsolete in many patients.

Non-contact left ventricular endocardial mapping in cardiac resynchronisation therapy.

BACKGROUND: Up to 30% of patients with heart failure do not respond to cardiac resynchronisation therapy (CRT). This may reflect placement of the coronary sinus lead in regions of slow conduction despite optimal positioning on current criteria. OBJECTIVES: To characterise the effect of CRT on left ventricular activation using non-contact mapping and to examine the electrophysiological factors influencing optimal left ventricular lead placement. METHODS: and results: 10 patients implanted with biventricular pacemakers were studied. In six, the coronary sinus lead was found to be positioned in a region of slow conduction with an average conduction velocity of 0.4 m/s, v 1.8 m/s in normal regions (p < 0.02). Biventricular pacing with the left ventricle paced 32 ms before the right induced the optimal mean velocity time integral and timing for fusion of depolarisation wavefronts from the right and left ventricular pacing sites. Pacing outside regions of slow conduction decreased left ventricular activation time and increased cardiac output and dP/dt(max) significantly. CONCLUSIONS: In patients undergoing CRT for heart failure, non-contact mapping can identify regions of slow conduction. Significant haemodynamic improvements can occur when the site of left ventricular pacing is outside these slow conduction areas. Failure of CRT to produce clinical benefits may reflect left ventricular lead placement in regions of slow conduction which can be overcome by pacing in more normally activating regions.

Beneficial effects of biventricular pacing in a patient with hypertrophic cardiomyopathy and intraventricular conduction delay.

The beneficial use of biventricular pacing is reported in a patient with hypertrophic cardiomyopathy and intraventricular conduction delay. This resulted in improvements in symptomatic status and exercise tolerance that may be related to cardiac resynchronisation. The improvement in symptoms by biventricular pacing in a patient with hypertrophic cardiomyopathy and intraventricular conduction delay is previously undocumented and requires further investigation.

A randomised comparison of the Omniflex and Magnarail systems in recanalisation of coronary occlusions.

OBJECTIVE: The reported success rates for angioplasty of occluded coronary arteries fall some way short of the success rates for angioplasty of sub-occlusive stenoses. Two angioplasty systems used in this setting were compared. DESIGN: A prospective randomised open study comparing the Magnarail system (Schneider) and the Omniflex system (Medtronic). SETTING: A regional cardiothoracic centre performing over 300 angioplasty procedures a year. PATIENTS AND METHODS: 50 consecutive patients with occluded (thrombolysis in myocardial infarction study (TIMI) grade 0 or 1) arteries thought to be suitable for recanalisation were assigned to undergo angioplasty with either the Magnarail or Omniflex as the primary system. Twenty minutes of fluoroscopic screening was allowed with the primary randomised system before it was considered a failure. The other non-randomised system could then be used at the operators' discretion, and a further 20 minutes' screening was permitted. MAIN OUTCOME MEASURES: A patent coronary artery with a residual stenosis of < 50% with prompt distal opacification (TIMI grade 3 flow) and a reduction in collateral supply to the index artery. RESULTS: The overall success rate in recanalising occluded vessels was 72%-64% for the Magnarail system used as the primary system and 51.7% for the Omniflex (NS). The Magnarail was more successful in angioplasties of the right coronary artery (11/14 v 3/10, p = 0.02) and in mid and distal sites of occlusion (11/17 v 4/14, p < 0.05). There was a trend in favour of the Omniflex in the left anterior descending coronary artery. CONCLUSION: Both systems would seem to be suitable for angioplasty of occluded coronary arteries. The improved steerability of the Magnarail may be advantageous in distal occlusions and lesions in tortuous arteries. The relatively stiffer Omniflex may be superior for proximal occlusions. The study group was too small to confirm this unequivocally.

Influence of platelet size before coronary angioplasty on subsequent restenosis.

Platelet size has been shown to reflect platelet activity. We prospectively measured the mean platelet volume (MPV) in 47 patients undergoing single vessel angioplasty for symptomatic angina. The patients underwent repeat angiography 4-8 months later irrespective of symptomatic status. Restenosis was assessed quantitatively by hand held calliper measurements of the lesion and qualitatively by a return of angina, ST segment changes on an exercise test and visual analysis of the lesion severity by two experienced angiographers. Twenty-four patients developed recurrent angina during the follow-up period, the MPV in the group with chest pain was 8.54 +/- 0.60 fl compared to 8.1 +/- 0.69 fl in the asymptomatic group (P = 0.04). Twenty two patients had significant ST segment changes at exercise. In this group the MPV was 8.6 +/- 0.56 fl compared to 8.0 +/- 0.70 fl for the group with a negative test (P = 0.002). Similarly visually assessed angiographic stenosis showed a significant increase in the restenotic group (8.6 +/- 0.56 vs. 8.0 +/- 0.61 fl, P = 0.001). The relative odds for developing clinically defined restenosis were 10.2 times greater if the pre-procedural MPV lay in the upper compared to the lowest quartile. There was a positive correlation between MPV and change in minimal luminal diameter between post angioplasty and follow-up angiography, assessed quantitatively, r = +0.56, P = 0.016. There was no association between clinical or angiographic definitions of restenosis and haemoglobin, red cell count, mean corpuscular volume, white cell count or platelet count. Platelet size may influence the development of restenosis after successful coronary angioplasty.

Nitric oxide synthase activities in human myocardium.

Myocardial constitutive and inducible nitric oxide (NO) synthase activities were measured in right ventricular tissue from 17 patients with dilated cardiomyopathy (DCM). A significant activity of inducible enzyme was accompanied by a low activity of the constitutive NO synthase. Thus, the myocardium has the capacity to express both NO synthases. NO may have a physiological as well as a pathological role in the human myocardium.

Role of nitric oxide synthesis in the regulation of coronary vascular tone in the isolated perfused rabbit heart.

OBJECTIVE: The aim was to study the effects on coronary vascular tone of three inhibitors of nitric oxide (NO) synthesis. METHODS: Studies were performed on isolated perfused hearts of 74 male New Zealand White rabbits fed normal laboratory diet. Resting coronary perfusion pressure was increased to 40-60 mm Hg with the thromboxane mimetic 9,11-dideoxy-9 alpha,11 alpha-methanoepoxy prostaglandin F2 alpha (U46619). The effects of NG-monomethyl-L-arginine (L-NMMA), N-iminoethyl-L-ornithine (L-NIO), and NG-nitro-L-arginine methyl ester (L-NAME) (0.3-300 microM) on resting coronary perfusion pressure were determined. The effects of these compounds, at concentrations that increased the resting perfusion pressure to a similar extent, on the fall in perfusion pressure induced by acetylcholine (0.1 microM) and glyceryl trinitrate (1 microM) were also investigated. In these studies the resting perfusion pressure was maintained at 40-60 mm Hg by reducing the concentration of U46619. RESULTS: L-NMMA, L-NIO, and L-NAME induced concentration dependent increases in resting coronary perfusion pressure (n = 3-9, p < 0.05). L-NAME had the greatest potency and efficacy, increasing the resting pressure by 48.0(SEM 9.6) mm Hg at 30 microM. L-NIO and L-NMMA increased perfusion pressure by 27.3(3.0) and 19.5(5.8) mm Hg respectively at the maximum concentration studied (300 microM). However, at concentrations that were equieffective on resting perfusion pressure (15 mm Hg increase), L-NMMA (100 microM), but not L-NIO (25 microM) or L-NAME (4 microM), significantly inhibited the fall in pressure induced by acetylcholine by 57.2(5.0)%, n = 6, p < 0.05. This effect of L-NMMA++ was attributed to a shorter duration of fall and was reversed by L-arginine (300 microM). L-NMMA (100 microM) and L-NIO (25 microM) potentiated the effect of glyceryl trinitrate by increasing the peak fall in perfusion pressure by 75.6(11.0)% and 68.8(24.1)% respectively (n = 6 for each, p < 0.05). CONCLUSIONS: The differential effects of the three inhibitors on resting coronary perfusion pressure and the acetylcholine induced fall in coronary perfusion pressure suggest that basal and stimulated NO synthesis may be differentially regulated. Reduction in the synthesis of endogenous NO by these compounds potentiates the glyceryl trinitrate induced fall in perfusion pressure, which may have important clinical implications.

Supraventricular tachycardia control with Tachylog II: long-term follow-up.

Ten patients aged 16-63 years (mean 36.3) had the Siemens P56T "Tachylog II" pacemaker implanted for treatment of drug refractory supraventricular tachycardia. The pacemaker incorporates a noninvasive electrophysiological study (EPS) facility and a sophisticated Holter function combined with a unique "learning" self-search antitachycardia algorithm. The Holter reveals that new tachycardias arise that are not previously detected at conventional EPS. The number of stimuli in the initiation sequences during noninvasive EPS proved highly variable, however, termination sequences remained constant in the long term. There was variability of timing of stimuli in the long term that was significantly greater for "new" tachycardias than for "original" arrhythmias. Long-term follow-up (at 1 month, 6 months, and 1 year) have shown that 90% of patients have good tachycardia control without the need for drugs. All patients confirm the acceptability of this pacemaker for control of their arrhythmias in the long term.

Comparison of the normal sinus node with seven types of rate responsive pacemaker during everyday activity.

The heart rate response of 59 patients aged 17-79 years implanted with seven different types of rate responsive pacemakers was evaluated during graded exercise treadmill testing and during standardised daily activities. The heart rate response in patients with pacemakers was compared with the chronotropic response in 20 healthy controls of similar age and sex distribution who performed identical protocols. All pacemaker types adequately simulated the control heart rate response during the graded exercise treadmill test except during the early stages of exercise. However, during everyday activities, the response of ventricular rate responsive (VVIR) pacemakers was varied. Activity sensing systems rapidly overresponded to staircase descent, to changes in walking speed, and to suitcase lifting with the pacemaker arm, and these systems did not respond to mental stress. "Physiological" sensors (QT and minute ventilation units) responded slowly to rapid changes in physiological demand. The QT pacemaker patients did respond to mental stress but showed a paradoxical increase in rate during the recovery phases of burst exercise protocols such as staircase ascent/descent and walking deceleration. Dual chamber pacemakers in VDD, DDD, and DDDR modes most closely simulated the normal chronotropic response during everyday activities. Graded exercise treadmill testing, in isolation, may not be the best way to asses or program the heart rate response in patients with the heart rate adaptive pacemakers because changes in heart rate during everyday activities may deviate considerably from the normal sinus response despite satisfactory simulation of the normal chronotropic response during treadmill testing.

Clinical outcome of coronary angioplasty for single-vessel disease.

The acute and long-term results of coronary angioplasty in 412 patients with single-vessel coronary artery disease are reported. Angiographic success was observed in 85.5% of all lesions and 84.7% of all arteries in which dilatation was attempted. Success rates improved during the study; since 1985, the angiographic success rate for non-occluded arteries has been 91.0%. Early complications occurred in 6.8%; angioplasty achieved clinical success in 80.3% of all patients at discharge from hospital. The median duration of follow-up was 772 days, with clinical status established for 98.8% of patients. 5 years after clinically successful angioplasty, cumulative cardiac survival was 96.6% and freedom from cardiac death and myocardial infarction was 90.4% (95.8% and 85.4%, respectively, on intention-to-treat analysis). Within 5 years of successful angioplasty, 12.4% of survivors underwent coronary bypass surgery and 16.9% had repeat angioplasty. Freedom from all cardiac events at 5 years was 70.2% after clinically successful angioplasty and 60.2% on intention-to-treat analysis. Angina symptoms were improved in over 80% of patients and abolished in 75%.

His bundle ablation with the laser thermal probe ("hot tip"): a feasibility study.

Successful percutaneous ablation of the bundle of His requires accurate localization together with delivery of the minimum effective energy to avoid unwanted effects. The energy output from laser sources can be controlled very precisely but is not easily directed to the bundle of His using conventional fiber optics. The laser thermal probe ("hot tip") consists of an optical fiber and a terminal metal cap that is rapidly heated during energy delivery. When applied to cadaver hearts at energies of 100-150 joules (10 watts for 10-15 seconds) the 2.0-mm diameter peripheral artery probe was able to damage the bundle of His without extensive surrounding damage. The right ventricular free wall and interventricular septum were perforated during some applications at these energies leaving a tract with a diameter of less than 2.0 mm. The atrioventricular (AV) membranous septum, Foramen Ovale, right atrial appendage, and septal leaflet of the tricuspid valve were more resistant at these energy levels and perforations were always less than 1.0 mm in diameter. The probe was modified for use during electrophysiological studies and good quality unipolar electrograms were recorded from the metal cap confirming that the probe could be accurately positioned adjacent to the bundle of His. The laser thermal probe deserves further study as a "self directing" ablation tool.

Transvenous cardioversion for the management of recurrent ventricular arrhythmias.

The efficacy of transvenous cardioversion and defibrillation for treating life threatening spontaneous ventricular arrhythmias was assessed in a study of 17 patients in a cardiac care unit. Eleven had ventricular tachycardia, five had ventricular fibrillation, and one had both. Transvenous cardioversion successfully terminated tachyarrhythmias on 42 separate occasions in ten patients. Stable electrode positions could not be achieved in two patients, recurrent late displacement occurred in one, and four patients had no further arrhythmias requiring cardioversion once the lead was placed. The energy levels required for successful cardioversion ranged from 0.05 J to 25 J for ventricular tachycardia and from 1 J to 25 J for ventricular fibrillation. The nine successful shocks of 1 J or less did not require sedation or general anaesthesia. High energy (25 J) endocardial shocks were unsuccessful in terminating arrhythmias in two patients, one with ventricular tachycardia and the other with both ventricular tachycardia and fibrillation. Minor unwanted effects of endocardial shocks occurred in five patients. These were acceleration of ventricular tachycardia in two patients and complications of pacing via the special lead in three others: failure of sensing occurred in all three and one patient also had a transient rise in pacing threshold. A postmortem examination in one patient who had received three unsuccessful high energy shocks revealed localised endocardial necrosis at the site of the distal electrode. Transvenous cardioversion offers advantages over external cardioversion but at present practical difficulties limit its application to patients with recurrent ventricular arrhythmias that cannot readily be controlled by conventional methods.

Physicians' attitudes to four common problems: hypertension, atrial fibrillation, transient ischaemic attacks, and angina pectoris.

A questionnaire was completed by 341 senior physicians on their attitudes to four common cardiovascular problems. Their replies showed that uncertainty about the end point for diastolic blood pressure still prevails and that their approach to the management of hypertension of differing severity in men and women of varying ages stems more from personal belief than from the results of clinical trials. Unless patients with atrial fibrillation also had mitral valve disease anticoagulation was not thought to be necessary, thereby making it ethically possible to carry out a trial of anticoagulants in stroke prevention on patients with atrial fibrillation but no valvular disease. The physicians' suggestions for very active management in transient ischaemic attacks extended beyond the evidence available to them, whereas their approach to the use of coronary arteriography closely reflected the results of clinical trials. These findings may indicate that recent cardiovascular trials that have provided definitive results have had more impact than earlier inadequate studies.

Intravenous and oral amiodarone for arrhythmias in children.

Oral amiodarone was administered to 30 children (aged one week to 14 years) for treatment of resistant or life threatening tachycardias. Five children received initial intravenous medication. The mean duration of oral treatment ranged from two weeks to 64 months (mean 23 months). Infants required a higher oral dose than older children when this was calculated on the basis of body weight but not when it was calculated on the basis of body surface area, indicating that the prescribed dose of amiodarone for infants should be calculated on the basis of body surface area. Although plasma concentrations of amiodarone were similar in infants and children, the plasma concentration of the metabolite desethylamiodarone was lower in infants. The arrhythmias were effectively controlled, by amiodarone alone in 19 and by amiodarone in combination with other drugs in nine children; amiodarone was ineffective in the remaining two children. Unwanted effects were common but were not significantly related to the dose, duration of treatment, or plasma concentration of amiodarone when group results were analysed. Grey facial skin pigmentation developed in two patients who received high cumulative doses of amiodarone and in whom plasma concentrations of amiodarone were high. Four children with biochemical hepatic dysfunction had high plasma concentrations of amiodarone and a further four children who experienced sleep disturbance had required high doses of amiodarone.

Rehydration in the treatment of severe hypercalcaemia.

Sixteen episodes of severe hypercalcaemia (more than 3.25 mmol/l) were treated by rehydration alone. Sodium repletion was invariably achieved within 48 hours (mean deficit 9.24 mmol/kg) although the fall in serum calcium was more protracted. A substantial fall in serum calcium (mean decrease 0.6 mmol/l) was achieved in thirteen patients; poor responses in three patients were associated with a rapidly increasing calcium load. Presentation of the data in terms of calcium excretion per unit of glomerular filtrate (CaE) and the setting of tubular reabsorption (TmCa/GFR) makes it possible to predict the likely effects of rehydration and patients with non-metastatic hypercalcaemia are easily identified. Rehydration is simple and often effective in the early management of this common metabolic problem but it is important that therapeutic goals are realistic and the intrinsic limitations of rehydration recognized. This depends upon a clear idea of the contribution that the kidney makes to the hypercalcaemia of malignant disease.