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Biomedical subjects

M D Lowe

Publications and source records attributed to M D Lowe.

16 recordsLinked to original sources
PubMed2001

Beta(2) adrenergic receptors mediate important electrophysiological effects in human ventricular myocardium.

OBJECTIVE: To define the effects of beta(2) adrenergic receptor stimulation on ventricular repolarisation in vivo. DESIGN: Prospective study. SETTING: Tertiary referral centre. PATIENTS: 85 patients with coronary artery disease and 22 normal controls. INTERVENTIONS: Intravenous and intracoronary salbutamol (a beta(2) adrenergic receptor selective agonist; 10-30 microg/min and 1-10 microg/min), and intravenous isoprenaline (a mixed beta(1)/beta(2) adrenergic receptor agonist; 1-5 microg/min), infused during fixed atrial pacing. MAIN OUTCOME MEASURES: QT intervals, QT dispersion, monophasic action potential duration. RESULTS: In patients with coronary artery disease, salbutamol decreased QT(onset) and QT(peak) but increased QT(end) duration; QT(onset)-QT(peak) and QT(peak)-QT(end) intervals increased, resulting in T wave prolongation (mean (SEM): 201 (2) ms to 233 (2) ms; p < 0.01). There was a large increase in dispersion of QT(onset), QT(peak), and QT(end) which was more pronounced in patients with coronary artery disease-for example, QT(end) dispersion: 50 (2) ms baseline v 98 (4) ms salbutamol (controls), and 70 (1) ms baseline v 108 (3) ms salbutamol (coronary artery disease); p < 0.001. Similar responses were obtained with isoprenaline. Monophasic action potential duration at 90% repolarisation shortened during intracoronary infusion of salbutamol, from 278 (4.1) ms to 257 (3.8) ms (p < 0.05). CONCLUSIONS: beta(2) adrenergic receptors mediate important electrophysiological effects in human ventricular myocardium. The increase in dispersion of repolarisation provides a mechanism whereby catecholamines acting through this receptor subtype may trigger ventricular arrhythmias.

Action Potentials↗
PubMed2000

Comparison of central venous and inferior vena caval pressures.

Inferior vena caval pressures were measured in 60 patients undergoing cardiac catheterization and compared with central venous pressure from within the right atrium. Mean pressures within the abdominal inferior vena cava were essentially the same as mean right atrial pressure, suggesting that the inferior vena cava provides a useful safe alternative for measuring central venous pressure.

Aged↗
PubMed2000

Coronary angiography in the presence of peripheral vascular disease: femoral or brachial/radial approach?

Peripheral vascular disease is considered a relative contraindication to the femoral approach for coronary angiography, but no data exist comparing the femoral and brachial/radial routes under these circumstances. We examined the influence of vascular approach on outcome. Two hundred and ninety-seven patients, mean age 67.1 +/- 8.4 years, with clinical or radiographic evidence of aortofemoral peripheral arterial disease underwent diagnostic coronary angiography during a 3-year period at this cardiothoracic center. The approach was successful in 121 of 154 femoral cases (79%) compared with 130 of 143 brachial/radial cases (91%; P < 0.01). Of the 33 failed femoral cases, 15 were then approached from the other femoral artery, with success in 6 (40%), while 18 were approached from the arm, with success in all (100%; P < 0.01). Brachial/radial cases took significantly longer than femoral cases (51 +/- 19 vs. 42 +/- 22 mins; P < 0.01). In cases where the femoral pulse was considered normal, the femoral approach nonetheless failed in 19 of 95 (20%). Major vascular complications (e.g., pulseless limb, arterial dissection, hemorrhage, or false aneurysm) occurred in nine femoral cases vs. zero brachial/radial cases (P < 0.01). Patients with peripheral vascular disease who undergo coronary angiography from the femoral artery have a 1-in-5 risk of procedural failure, necessitating use of an alternative vascular approach, and a 1-in-20 risk of a major vascular complication. Normality of femoral arterial pulsation is not a good predictor of femoral success. Brachial/radial approaches take longer, but succeed more frequently and have a negligible major vascular complication rate. We believe that patients with peripheral vascular disease should undergo coronary angiography via brachial or radial approach. Cathet. Cardiovasc. Intervent. 49:32-37, 2000.

Aged↗
PubMed2000

Syncope after effort.

A 29-year-old man developed recurrent syncope following exertion. Cardiac investigations revealed no evidence of structural heart disease, but during exercise testing, in the recovery phase, he sustained a bradycardia and then asystole for a prolonged period. Before cardiac massage could be instituted a tonic-clonic fit occurred, and this initiated a return to sinus rhythm. His symptoms were abolished following the implantation of a dual-chamber pacemaker.

Adult↗
PubMed1999

Blockade of putative beta4- and beta1-adrenoceptors by carvedilol in ferret myocardium.

The putative beta4-adrenoceptor mediates positive inotropic effects, action potential shortening and arrhythmias in ferret ventricle. Here we compared the affinity of carvedilol at the putative beta4-adrenoceptor and beta1-adrenoceptor, activated by (+/-)-CGP 12177 and (-)-isoprenaline, respectively. In paced right ventricular preparations, carvedilol (0.01-10 micromol/l) was a simple competitive antagonist of the positive inotropic effects of (+/-)-CGP 12177 (slope of Schild-plot = 1.02, pK(B) = 6.8) and (-)-isoprenaline (slope of Schild-plot = 0.98, pK(B) = 8.1). Carvedilol also blocked putative beta4- and beta1-adrenoceptors of left ventricle, left atrium and sino-atrial pacemaker. Carvedilol therefore interacts with the putative beta4-adrenoceptor according to the law of mass action and may provide a lead in the development of putative beta4-adrenoceptor-selective antagonists.

Adrenergic beta-Agonists↗
PubMed1998

Coronary angiography from the radial artery--experience, complications and limitations.

AIMS: to assess the outcomes, complications and limitations of coronary angiography performed via percutaneous radial artery puncture. METHODS AND RESULTS: two hundred and fifty patients underwent diagnostic coronary angiography from the radial artery, 182 (72.8%) of whom had contraindications to the femoral approach, for example due to peripheral vascular disease (n=85), therapeutic anticoagulation (29), or failed femoral approach (17). Procedural success in this high-risk population was achieved in 231 patients (92.4%). Principle reasons for failure were unsuccessful radial access (5) and arterial spasm (5). Procedure duration (SD) for an operator's first 20 cases compared with cases thereafter (min) was 47.7 (16.7) vs. 41.5 (14.6), P=0.0004; fluoroscopy time (min) 9.7 (7.1) vs. 6.6 (5.1), P=0.0001 and procedural success 89.6% vs. 94.1%, P=ns. Complications included two deaths associated temporally with catheterisation, three cases of arterial dissection without ischaemic sequelae and one transient ischaemic attack. CONCLUSIONS: coronary angiography can be performed successfully from the radial artery, but this approach has limitations, which include the need to demonstrate dual palmar vascular supply, the prolonged learning phase, the procedural failure rate, patient discomfort and a demonstrable incidence of vascular and haemodynamic complications. We believe that radial coronary angiography should only be undertaken when there is a contraindication to the femoral approach.

Chi-Square Distribution↗
PubMed1998

Comparison of radial versus brachial approaches for diagnostic coronary angiography when the femoral approach is contraindicated.

One hundred patients with contraindications to the femoral approach were randomized to undergo diagnostic coronary angiography via percutaneous radial puncture or brachial artery cutdown. Procedure duration, fluoroscopy time, and total radiation dose were significantly less via the radial route, whereas procedural success, complication rates, and pain scores were comparable; we conclude that the radial technique should be the arm approach of choice for new trainees, although there will be occasions when radial access fails and a brachial approach is required.

Aged↗
PubMed1998

Action potential shortening through the putative beta4-adrenoceptor in ferret ventricle: comparison with beta1- and beta2-adrenoceptor-mediated effects.

The electrophysiological responses to (-)-CGP 12177 ((-)-4-(3-tertiarybutylamino-2-hydroxypropoxy) benzimidazol-2-one), an agonist for the putative beta4-adrenoceptor, were investigated on isolated perfused ferret hearts paced at 100 min(-1) and compared to those of (-)-noradrenaline and (-)-adrenaline, mediated through beta1- and beta2-adrenoceptors respectively. The three agonists decreased ventricular monophasic action potential duration but prolonged the action potential plateau; beta3-adrenoceptor-selective agonists had no effect. (-)-CGP 12177 was the most potent, but (-)-noradrenaline the most efficacious; both agonists caused ventricular extra-systoles. Because only (-)-noradrenaline but not (-)-CGP 12177 elicited shortening of the refractory period, the mechanism of arrhythmias mediated through beta1- and putative beta4-adrenoceptors may be different.

Action Potentials↗
PubMed1998

Ventricular pacemaker upgrade: experience, complications and recommendations.

OBJECTIVE: To assess outcomes of pacemaker upgrade from single chamber ventricular to dual chamber. DESIGN: Retrospective analysis of patients undergoing the procedure. SETTING: Specialist cardiothoracic unit. PATIENTS: 44 patients (15 female, 29 male), mean (SD) age at upgrade 68.2 (12.9) years. INTERVENTIONS: Upgrade of single chamber ventricular to dual chamber pacemaker. MAIN OUTCOME MEASURES: Procedure duration and complications. RESULTS: Principal indications for upgrade were pacemaker syndrome (17), "opportunistic"--that is, at elective generator replacement (8), heart failure (7), non-specific breathlessness/fatigue (7), and neurally mediated syncope (3). Mean (SD) upgrade procedure duration (82.9 (32.6) minutes) significantly exceeded mean VVI implantation duration (42.9 (13.3) minutes) and mean DDD implantation duration (56.6 (22.7) minutes) (both p < 0.01). Complications included pneumothorax (1), ventricular arrhythmia requiring cardioversion (2), protracted procedure (10), atrial lead repositioning within six weeks (8), haematoma evacuation (1), superficial infection (1), and admission to hospital with chest pain (1); 20 patients (45%) suffered one or more complications including four of the eight who underwent opportunistic upgrade. CONCLUSIONS: Pacemaker upgrade takes longer and has a higher complication rate than either single or dual chamber pacemaker implantation. This suggests that the procedure should be performed by an experienced operator, and should be undertaken only if a firm indication exists. Patients with atrial activity should not be offered single chamber ventricular systems in the belief that the unit can be upgraded later if necessary at minimal risk.

Aged↗
PubMed1998

Sotalol associated polymorphic ventricular tachycardia and coronary spasm.

Sotalol may induce torsade de pointes through cardiac action potential prolongation, but a proarrhythmic effect secondary to its beta blocking action has not been reported. A 54 year old man presented with symptoms of angina and presyncope, subsequently demonstrated to be associated with coronary spasm. Treatment with sotalol exacerbated his symptoms and resulted in recurrent polymorphic ventricular tachycardia with a pattern indistinguishable from that caused by a class III action. Following sotalol with-drawal polymorphic ventricular tachycardia resolved completely. Polymorphic ventricular tachycardia in patients treated with sotalol may therefore not always be the result of delayed repolarisation, but may be caused by beta adrenoceptor blockade.

Adrenergic beta-Antagonists↗
PubMed1970

Sex attractant of the grass grub beetle.

The sex attractant produced by adult females of the grass grub beetle Costelytra zealandica (White) has been isolated and identified as phenol. Field tests with phenol-water mixtures were attractive to male beetles in particular.

Animals↗
PubMedDate not supplied

Knowledge and attitude of nurses on medical wards to defibrillation.

We questioned 112 qualified nurses working on general medical wards about their resuscitation experience and knowledge of ECG interpretation and defibrillation. Although all but two of them had been formally trained in basic cardiopulmonary resuscitation (CPR) only 16 had received any training in the last six months. Seventy-five per cent of nurses were involved in CPR as first responders but only 18% had used a defibrillator during a cardiac arrest. Identification of ECG rhythms and practical knowledge about defibrillation was encouraging despite the lack of formal training in this field. Almost every one of the nurses would be willing to receive training in advanced cardiac life support. The responses to this inquiry suggest that nurses on medical wards are enthusiastic about advanced cardiac life support and already have some basic practical knowledge. Appropriate training (and retraining) of nursing staff should improve the outcome of resuscitation efforts on medical wards.

Arrhythmias, Cardiac↗