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Biomedical subjects

W Culling

Publications and source records attributed to W Culling.

At least 19 recordsLinked to original sources
PubMed2003

Clozapine associated dilated cardiomyopathy.

A 31-year-old white man was referred for investigation of a persistent sinus tachycardia. His only significant past medical history was of chronic schizophrenia for which he had been taking clozapine for six years. An electrocardiogram demonstrated sinus tachycardia, voltage criteria for left ventricular hypertrophy, and a prolonged QTc. Echocardiographic findings were consistent with a dilated cardiomyopathy. Serious cardiac complications of clozapine use are rare but have been reported previously. It is important to note that sinus tachycardia may be the only obvious clinical sign, and that complications can manifest months or even years (as in this case) after starting the drug. Patients on clozapine should be informed of potential cardiac symptoms and doctors should maintain a high degree of clinical suspicion throughout the duration of treatment.

Adult↗
PubMed1994

Cardiac tamponade after thrombolysis.

Thrombolysis has been very effective in reducing the morbidity and mortality from acute myocardial infarction. Serious adverse events are not uncommon, however. We describe a case in which a haemopericardium and tamponade developed in a patient with a history of recurrent idiopathic pericarditis and to whom streptokinase had been administered following a suspected myocardial infarction. The case highlights the need for caution in the administration of thrombolytics to patients with a documented history of pericarditis.

Adult↗
PubMed1989

Changes in the haemodynamic responses to exercise, posture and nitrates after treatment of congestive heart failure with an arteriolar vasodilator.

1. Haemodynamic responses to exercise, posture and nitrates were measured before and after 8 weeks of therapy with an arteriolar smooth muscle specific calcium antagonist, nicardipine, in eight patients with congestive heart failure (New York Heart Association class II or III). 2. The acute haemodynamic effects of intravenous nicardipine before and after 8 weeks of oral therapy confirmed its vasodilating properties, with similar end-points to the initial response after the 8 week period. 3. After 8 weeks of oral therapy all patients improved by one New York Heart Association class and treadmill exercise duration was significantly increased. In contrast, sitting bicycle exercise duration was not prolonged, although, at the same peak workload, changes in cardiac output, stroke volume and systemic vascular resistance were significantly improved after 8 weeks of therapy. 4. Sublingual glyceryl trinitrate predominantly affected pulmonary vascular resistance before and after chronic therapy with nicardipine, although the effects were less marked after 8 weeks. In contrast, the systemic vascular effects of glyceryl trinitrate were significantly increased after 8 weeks of therapy with nicardipine. 5. Increased vasodilator responses to sublingual glyceryl trinitrate and exercise after chronic treatment with nicardipine, in the absence of significant residual vasodilatation at rest, suggests that indirect changes in systemic arterioles may accompany and possibly contribute to the clinical improvement in heart failure.

Adult↗
PubMed1987

Polymorphous ventricular tachycardia due to alpha-blockade.

We report a case of polymorphous ventricular tachycardia caused by treatment with the post-synaptic alpha-blocking agent indoramin. This has not been reported with indoramin previously, nor to our knowledge with any other alpha-blocker. This pro-arrhythmic effect appears to be related to its class 3 anti-arrhythmic properties (QT interval prolongation) which is dose dependent, occurring only at large doses.

Arrhythmias, Cardiac↗
PubMed1987

Arrhythmogenic and electrophysiological effects of alpha adrenoceptor stimulation during myocardial ischaemia and reperfusion.

To examine possible arrhythmogenic effects of alpha adrenoceptor stimulation, we studied the effects of methoxamine 10(-6) M on arrhythmias and cellular electrophysiology during global myocardial ischaemia and reperfusion in isolated Langendorff perfused guinea-pig hearts. To avoid interference from release of endogenous catecholamines during ischaemia or reperfusion, experiments were performed using catecholamine depleted hearts (myocardial noradrenaline = 11% of control). Catecholamine depletion markedly reduced the incidence of VT and VF during ischaemia and reperfusion and perfusion with methoxamine significantly reversed this. This arrhythmogenic effect of methoxamine was only observed during ischaemia or reperfusion, was independent of beta adrenoceptor blockade and H2 receptor blockade but was abolished by alpha adrenoceptor blockade with phentolamine. Catecholamine depletion blunted the ischaemia induced fall in action potential amplitude and Vmax and prolonged action potential duration and refractory period. Perfusion with methoxamine either partially or completely reversed these effects. Thus, alpha adrenoceptor stimulation has little effect on normally perfused myocardium, but may induce VT or VF during ischaemia or reperfusion.

Animals↗
PubMed1986

Estimation of left ventricular end-diastolic pressure by pulsed Doppler ultrasound.

Left ventricular end-diastolic pressure (LVEDP) measured at cardiac catheterisation and simultaneous mitral flow patterns obtained by pulsed Doppler ultrasound scanning were assessed in twenty patients (fourteen males) with ischaemic heart disease. The ratio of passive and active components of mitral flow showed a significant linear correlation with LVEDP. Active (left atrial) mitral flow diminished as left ventricular end-diastolic pressures increased. Mitral flow ratios greater than 2 were always associated with LVEDP greater than 20 mmHg. This application of Doppler echocardiography provides a simple non-invasive method of estimating LVEDP.

Adult↗
PubMed1986

Electrophysiological disturbances associated with acute myocardial infarction.

By the time most patients reach hospital with acute myocardial infarction the risk of developing ventricular fibrillation (VF) is receding and Q wave evolution is complete. While these changes are the culmination of a single irreversible ischaemic insult, this may follow several reversible episodes of ischaemia associated with marked ECG changes during the preceding hours or days and further ischaemic episodes may follow the development of Q waves. Cellular electrophysiological changes associated with experimental myocardial ischaemia in an isolated guinea pig preparation were a reduction in refractory period and action potential amplitude, Vmax and duration while conduction time and QRS width were prolonged. Spontaneous recovery in action potential amplitude and Vmax was observed after 12 min of ischaemia and depended on the presence of residual coronary flow. Electrophysiological recovery commenced rapidly on reperfusion but with further shortening of action potential duration. Reperfusion VF was most likely to occur when the associated ischaemic insult was 20-30 min in duration. Myocardial catecholamine depletion significantly reduced these arrhythmias and this antiarrhythmic action was associated with marked attenuation of the electrophysiological effects of ischaemia and reperfusion.

Action Potentials↗
PubMed1986

Antianginal and haemodynamic effects of alpha 1-adrenoceptor blockade.

We studied the effects of alpha 1-adrenoceptor blockade with indoramin on exercise tolerance in 15 patients with chronic stable angina using a double-blind crossover protocol. Thirteen patients had been receiving beta-adrenoceptor blocking drugs and nitrates. The therapy of these patients was continued unchanged throughout the study. Indoramin, in a dose of 25 mg three times daily, prolonged exercise duration by 17% (p less than 0.01) and increased oxygen consumption during exercise by 21% (p less than 0.01), while the maximal double product was unchanged. This increase in exercise capacity was associated with significant attenuation in ST segment depression during exercise. To investigate the mechanism of this antianginal effect, we studied the effects of indoramin (0.2 mg/kg i.v.) on coronary and systemic haemodynamics in a further 11 male patients with chronic stable angina who were receiving beta-adrenoceptor blocking drugs. Measurements were obtained during sinus rhythm and during atrial pacing from 100 beats/min, incremented by 20 beats/min at intervals of 3 min until the onset of angina. Indoramin had no effect on resting heart rate (64 +/- 2 vs. 67 +/- 2 beats/min), but did prolong pacing time to angina (7.4 +/- 0.7 vs. 5.4 +/- 0.5 min; p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1985

Cardiac postjunctional supersensitivity to beta-agonists after chronic chemical sympathectomy with 6-hydroxydopamine.

The sensitivity to sympathomimetic amines of isolated atria removed from sham-injected and 6-hydroxydopamine-treated (6-OHDA) guinea-pigs was examined in the presence of an extraneuronal uptake blocker and an alpha-adrenoceptor antagonist. Three weeks of pretreatment with 6-OHDA resulted in leftwards shifts of the dose-response curves for the positive chronotropic and inotropic responses of right and left atria to isoprenaline. The responses to the partial agonist salbutamol were also potentiated after 6-OHDA pretreatment, revealed as an increase in the maximum response relative to isoprenaline. The supersensitivity was post-synaptic in origin and independent of changes in disposition or metabolism, since it was observed with agonists immune to neuronal uptake and O-methylation, and in the presence of extraneuronal uptake inhibition by metanephrine. It was also specific for the beta-adrenoceptor, no supersensitivity to histamine being found. In the right atria, the supersensitivity was partially masked by an opposing depressant effect after 6-OHDA pretreatment which was observed with histamine. Dissociation constants (KA) for the left atrial inotropic responses to orciprenaline were determined by use of the antagonist Ro 03-7894. Atria from 6-OHDA-pretreated animals were supersensitive to orciprenaline, but the KA value did not differ from that after sham injection. It could therefore be concluded that the increase in sensitivity was not due to an increase in affinity for the beta-adrenoceptor.

Adrenergic beta-Agonists↗
PubMed1985

Antiarrhythmic and electrophysiological effects of alpha adrenoceptor blockade during myocardial ischaemia and reperfusion in isolated guinea-pig heart.

An isolated buffer perfused guinea-pig heart preparation has been used to study the antiarrhythmic and cellular electrophysiological effects of alpha adrenoceptor blockade during myocardial ischaemia and reperfusion. Phentolamine 5 X 10(-6) M and indoramin 2 X 10(-6) M significantly reduced the incidence of ventricular tachycardia (VT) and ventricular fibrillation (VF) during ischaemia and reperfusion. Both drugs prolonged action potential duration (APD) and refractory period and reduced Vmax during normal perfusion and these effects were maintained during ischaemia. Reperfusion led to prompt recovery in all hearts but with initial transient shortening of APD. Phentolamine and indoramin abolished shortening of the APD whether added prior to ischaemia or immediately prior to reperfusion, and attenuated the reduction in refractory period, due to higher values at the end of ischaemia. Myocardial catecholamine depletion also significantly reduced ventricular tachycardia and ventricular fibrillation during ischaemia and reperfusion. Catecholamine depletion had similar effects on APD, refractory period and conduction, but phentolamine produced no additional effects when added to catecholamine depleted hearts suggesting that the effects observed here are mediated via adrenergic rather than direct myocardial effects.

Adrenergic alpha-Antagonists↗
PubMed1985

Electrophysiological effects of alpha-adrenoceptor stimulation in normal and ischemic myocardium.

To investigate the mechanism by which alpha-adrenoceptor blocking drugs prevent ventricular arrhythmias associated with myocardial ischaemia and reperfusion, we studied the effects of alpha blockade, alpha-adrenoceptor agonists, and myocardial catecholamine depletion on arrhythmias and cellular electrophysiology during ischaemia and reperfusion in isolated perfused guinea pig hearts. Perfusion with phentolamine or indoramin significantly reduced ventricular tachycardia (VT) and ventricular fibrillation (VF) during ischaemia and reperfusion, and phentolamine was equally effective during reperfusion when added at the end of ischaemia. Both drugs prolonged action-potential duration (APD) and refractory period during ischaemia and reperfusion, and studies with phentolamine, in catecholamine-depleted hearts, indicated that its action was related to the presence of catecholamines. Myocardial catecholamine depletion also significantly reduced VT and VF during ischaemia and reperfusion. Perfusion with an alpha 1-adrenoceptor agonist, however, significantly reversed this antiarrhythmic effect, increasing the incidence of VT and VF during ischaemia and reperfusion. This arrhythmogenic effect was associated with a reduction in APD and refractory period, i.e., a reversal of the electrophysiological effects of catecholamine depletion. These results indicate that alpha-adrenoceptor stimulation is arrhythmogenic during myocardial ischaemia and reperfusion, and that the antiarrhythmic action of alpha-adrenoceptor antagonists is mediated via adrenergic rather than direct myocardial effects.

Action Potentials↗
PubMed1984

Effects of myocardial catecholamine depletion on cellular electrophysiology and arrhythmias during ischaemia and reperfusion.

The effect of myocardial catecholamine depletion on cellular electrophysiology and arrhythmias was assessed in Langendorff perfused guinea pig hearts during ischaemia and reperfusion. Myocardial noradrenaline was reduced to 0.17 +/- 0.04 microgram X g-1 by intracardiac injection of 6-hydroxydopamine (450 mg X kg-1 in six doses over 20 days) compared with 1.5 +/- 0.2 microgram X g-1 in vehicle injected controls. Myocardial catecholamine depletion significantly reduced the incidence of ventricular tachycardia and fibrillation during 30 min of global ischaemia and subsequent reperfusion. Myocardial catecholamine depletion prolonged action potential duration and refractory period during control perfusion and blunted ischaemia induced reduction in action potential amplitude, Vmax, and duration, but accentuated the prolongation in conduction time and QRS width. Catecholamine depletion abolished or attenuated reperfusion induced shortening of action potential duration and refractory period. Catecholamine depletion increased myocardial glycogen levels from 2.47 +/- 0.3 mg X g-1 wet weight to 4.39 +/- 0.3 mg X g-1; fasting animals for 48 h prior to study reversed this with no attenuation of the electrophysiological or antiarrhythmic action. These results provide further evidence that release of endogenous myocardial catecholamines contributes to the electrophysiological changes and arrhythmias associated with myocardial ischaemia and reperfusion.

Action Potentials↗
PubMed1984

Effects of sotalol on arrhythmias and electrophysiology during myocardial ischaemia and reperfusion.

Isolated, buffer perfused guinea pig hearts were used to study the effects of sotalol on arrhythmias and electrophysiology during 30 min of myocardial ischaemia, induced by reducing coronary flow to 10% of control, and subsequent reperfusion. Action potentials were recorded using the floating microelectrode technique and arrhythmias were noted and defined by extracellular electrical records. Sotalol 10(-4) mol X litre-1 reduced the incidence of ventricular arrhythmias during myocardial ischaemia and reperfusion. Prior to the onset of ischaemia sotalol reduced action potential amplitude and Vmax, and prolonged action potential duration, refractory period, and conduction time, and increased pacing threshold. During myocardial ischaemia the effect of sotalol on action potential duration disappeared, and that on refractory period was diminished. The effect of sotalol on action potential amplitude and Vmax was reduced during the early (2 to 12 min) part of ischaemia, but later, at the onset of arrhythmias, tended to reemerge, while the effect on QRS width was exaggerated. Thus the cellular electrophysiological effects of sotalol on normal myocardium provided a poor guide to the mechanism of its antiarrhythmic action in ischaemic tissue.

Action Potentials↗