Introduction of nurse led DC cardioversion service in day surgery unit: prospective audit.

PROBLEM: Atrial fibrillation is the most common persistent arrhythmia in adults and carries an increased risk of thromboembolism and stroke. Electrical (DC) cardioversion is an effective treatment, but logistical difficulties in many institutions lead to problems providing a prompt service. This reduces the rate of long term success, delays relief of symptoms, and increases the burden on anticoagulation clinics. DESIGN: Prospective audit of introduction of a collaborative, nurse led DC cardioversion service in a day surgery unit. SETTING: Day surgery unit 5 km from an acute hospital in southeast London. KEY MEASURES FOR IMPROVEMENT: Waiting times, success of procedures, and complication rates. STRATEGIES FOR CHANGE: Collaborative working across traditional specialty boundaries; empowerment of patients within the process; using a nurse consultant as a single point of reference to coordinate the service. EFFECTS OF CHANGE: Sinus rhythm was restored in 131 (92%) of the first 143 patients treated. Three patients needed hospital admission; all were discharged uneventfully within 24 hours. No important complications occurred. Waiting times were reduced from 27 weeks to eight weeks for patients eligible for the service. LESSONS LEARNT: Elective DC cardioversion under general anaesthesia can be safely done by an appropriately trained nurse in a day surgery unit remote from an acute general hospital. This model of care is effective and can reduce waiting times and relieve pressure on acute beds and junior doctors.

S-nitrosoglutathione inhibits platelet activation and deposition in coronary artery saphenous vein grafts in vitro and in vivo.

OBJECTIVE: To investigate platelet activation and deposition in human saphenous vein and internal mammary artery grafts following coronary artery bypass in vitro and in vivo, as well as inhibition of activation by the platelet selective nitric oxide donor S-nitrosoglutathione (GSNO). DESIGN: Controlled in vitro and in vivo studies. SETTING: Tertiary cardiac centre. PATIENTS: 24 patients undergoing coronary artery bypass surgery requiring vein and artery grafts. INTERVENTIONS: In vitro: human platelet rich plasma was perfused through segments of vein and artery, with or without GSNO 10(-6) M, and the platelet count was measured in the effluent. In vivo: indium-111 labelled antibody against the platelet alpha granule protein GMP-140 was injected at the end of coronary bypass grafting and gamma counts were compared between vein and artery grafts with or without systemic infusion of GSNO (40 nmol/min). RESULTS: In vitro: platelet count in perfused vein (< 70% of baseline) decreased more than in artery segments (89-94% of baseline) (p < 0.001). The platelet count was unchanged with GSNO in vein and artery segments. In vivo: gamma counts were greater at all time points over vein than artery grafts (p < 0.05), and were reduced by infusion of GSNO (p < 0.05). CONCLUSIONS: Platelet activation is greater in vein than in artery grafts in vitro and in vivo. Activation, which contributes to early vein graft failure, was inhibited by GSNO.

Non-invasive cardiac investigations in patients awaiting renal transplantation.

Patients with chronic renal failure undergoing renal transplantation have a high prevalence of cardiovascular disease. Invasive investigation may identify those at risk of cardiac death during or after renal transplantation, but which patients should undergo cardiac catheterization is currently not clear. In 95 patients awaiting renal transplantation we assessed the ability of echocardiography and exercise electrocardiography to identify patients at risk of cardiac death. Echocardiography identified impaired left ventricular (LV) systolic function in 20%, severe in 8%. Of the patients with severe LV dysfunction, 25% died before transplantation. Of those undergoing exercise electrocardiography, 44% did not achieve 85% of maximum predicted heart rate. No coronary artery disease requiring intervention was identified by exercise testing. These findings indicate that echocardiography, but not exercise electrocardiography, should be part of the assessment for renal transplantation.

Determining optimal atrial sensitivity settings for single lead VDD pacing: the importance of the P wave histogram.

In order to provide atrioventricular synchrony, VDD pacing systems require reliable atrial sensing. Variations in atrial signals with exercise and daily activities may lead to undersensing, with loss of physiological pacing. The aim of this study was to determine, for a single lead VDD pacing system, the maximal variation in atrial signals in order to facilitate optimal programming of atrial sensitivity. Fifteen patients underwent implantation of a Vitatron Saphir VDD pacemaker with a Vitatron Brilliant electrode. At a mean (+/-SD) follow-up of 67.3 +/- 38.8 days, resting P wave amplitude was compared with the P wave amplitude histogram obtained from the pacemaker, which recorded atrial signals over the preceding 30 days. Resting P wave amplitude was also compared with P wave amplitudes during variations in posture, respiration, and during exercise. P wave amplitude showed great variation with changes in posture and respiration, but there was no consistent increase or reduction. During exercise, the mean P wave amplitude fell by 36.6% +/- 31.3% compared with the resting value (P < 0.05). During daily activities, 22.6% of P wave amplitudes recorded on the P wave histogram were < 0.5 mV. The smallest P wave amplitudes were detected by the P wave histogram in 11 (79%) of 14 patients. These data suggest that atrial sensitivity may need to be programmed higher than that indicated by single readings or exercise. The P wave amplitude histogram is the most reliable indicator of the smallest atrial signal and should be used to optimize atrial sensitivity settings.

A study of platelet activation during human cardiopulmonary bypass and the effect of S-nitrosoglutathione.

Cardiac surgery is complicated by the occurrence of post-operative bleeding due to platelet dysfunction. This is largely caused by platelet activation and consumption during cardiopulmonary bypass. Patients undergoing cardiac surgery requiring cardiopulmonary bypass were studied to determine whether early platelet changes due to bypass could be inhibited using the platelet-selective nitric oxide donor S-nitrosoglutathione (GSNO). Flow cytometry was used to measure platelet surface expression of P-selectin (an alpha-granule protein) and glycoproteins (GP) IIb/IIIa and Ib (mediators of aggregation and adhesion) before and 5 and 10 min after commencing cardiopulmonary bypass, in 6 controls and 6 patients receiving GSNO 50 microg/min. Platelet P-selectin expression increased during bypass both in controls and patients receiving GSNO. Glycoproteins IIb/IIIa and Ib fell during bypass in control and GSNO-treated patients. There was no difference between control and GSNO-treated groups. Thus no significant platelet inhibition by S-nitrosoglutathione was demonstrated under these conditions.

Platelet activation in acute myocardial infarction and unstable angina is inhibited by nitric oxide donors.

Platelet activation and thrombus formation within the coronary artery are major factors in acute myocardial infarction (AMI) and unstable angina (UA), and continuing platelet activation is associated with an adverse prognosis. We assessed platelet activation by using flow cytometry to measure platelet surface expression of P-selectin and glycoprotein IIb/IIIa in 20 patients with AMI and 20 with UA, all of whom were treated with aspirin. Platelet studies were repeated after the infusion of a nitric oxide donor (glyceryl trinitrate or S-nitrosoglutathione) that produced a fall in mean arterial pressure of no more than 10 mm Hg. P-selectin was expressed on 2.5% (range, 1.4% to 6.3%) of platelets from AMI and 2.3% (range, 1.6% to 3.3%) from UA subjects compared with 1.0% (range, 0.6% to 1.9%) of platelets from 20 control volunteers without angina (P < .001). Glycoprotein IIb/IIIa expression was 101.6 +/- 2.7 arbitrary units of relative fluorescence in AMI and 100.2 +/- 3.3 in UA compared with 87.8 +/- 2.5 in control subjects (P < .01). In both AMI and UA, S-nitrosoglutathione reduced P-selectin (P < .001) and glycoprotein IIb/IIIa (P < .05) expression, as did glyceryl trinitrate (P < .02 and P < .01, respectively). In 3 of 20 patients receiving glyceryl trinitrate the lowest dose was not tolerated due to headache or hypotension. These findings show that platelet activation persists in AMI and UA despite aspirin treatment and that this can be inhibited by using glyceryl trinitrate or S-nitrosoglutathione. S-nitrosoglutathione is better tolerated at the doses required.

Inhibition of platelet activity by S-nitrosoglutathione during coronary angioplasty.

Platelet activation is associated with acute vessel occlusion and chronic restenosis after percutaneous transluminal coronary angioplasty (PTCA). Organic nitrates, which act by releasing the vasodilator and anti-platelet agent nitric oxide (NO), have a predominantly vasodilator action and cause hypotension at doses required to inhibit platelet activation. S-nitrosoglutathione (GSNO) is an NO donor with a preferential action on platelets. We investigated platelet activation in patients undergoing PTCA and the effect of GSNO. Blood was sampled from the coronary sinus to measure platelet surface expression of P-selectin and glycoprotein IIb/IIIa as indices of platelet activation. In 7 control patients, PTCA caused a rise in platelet surface expression of P-selectin and glycoprotein IIb/IIIa, which was maximal 5 minutes after PTCA, indicating increased platelet activation despite treatment with aspirin, glyceryl trinitrate, and heparin. 6 patients received an intracoronary infusion of GSNO, starting 10 min before PTCA. GSNO significantly inhibited the PTCA-induced increase in platelet surface expression of P-selectin and glycoprotein IIb/IIIa without altering blood pressure. These findings show that platelets are activated following PTCA and that GSNO can prevent this activation.

Atrial permanent pacing for sinus node dysfunction with absent right superior vena cava.

In patients with sinus node dysfunction and normal atrioventricular conduction, single chamber atrial pacing (AAI or AAIR mode) represents the most physiological treatment. Sinus node dysfunction is recognised in association with an absent right superior vena cava, and we present a case in which complete resolution of symptoms was achieved with endocardial atrial permanent pacing.