Studies were made in anaesthetised dog of the effects of repeated acute occlusions of a branch of the anterior descending coronary artery on ventricular refractory periods in adjacent ischaemic and non-ischaemic myocardium. Differences occurred in refractoriness between normal and ischaemic areas in the ventricle. This was greatest 2.5 min after occlusion, and on release of occlusion, ventricular refractory periods reverted to normal within 5 min. Spontaneous ventricular fibrillation was directly and significantly related to the degree of dispersion of refractoriness in a given dog immediately preceding release and following release of occlusion. Infusion of isoprenaline caused significant shortening of refactory period and increased dispersion of refractoriness during ischaemia. Studies of dispersion of refractoriness should prove valuable in assessing the efficiency of metabolic or antiarrhythmic protection against ventricular fibrillation.

Animals↗

PubMed1978

Haemodynamic effects on the myocardial blood flow supply/oxygen demand ratio in pacing induced angina pectoris.

Angina pectoris results from an imbalance between oxygen supply and demand in the subendocardium. The haemodynamic effects contributing to this imbalance have been studied in 10 patients with coronary artery disease. Myocardial oxygen demand was estimated from the tension time index (TTI), potential subendocardial flow from a diastolic pressure time index (DPTI), and the oxygen supply/demand ratio from (DPTI/TTI. With progressively increasing pacing rates up until induction of angina, no significant change in TTI was found whereas a significant fall in DPTI and DPTI/TTI occurred (P less than 0.001). During pacing runs with induction of angina DPTI/TTI reached a minimum value 5 s before,and at the onset of angina. No such relationship was seen for TTI or DPTI alone. A significant rise in LVEDP (P less than 0.05) and fall in dP/dt min (P less than 0.01) occurred at angina both contributing to a further reduction in DPTI and DPTI/TTI. Changes in DPTI/TTI may then reflect changes in the myocardial blood flow supply/oxygen demand ratio in the presence of coronary artery disease and haemodynamic changes before and at the induction of angina lead to a further reduction of this ratio.

Angina Pectoris↗

PubMed1978

Effect of antilipolytic therapy on ST segment elevation during myocardial ischaemia in man.

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Coronary Disease↗

PubMed1977

Combined electrophysiological technique for assessment of the cellular basis of early ventricular arrhythmias.

A new technique has been used in dogs to make combined measurements in vivo of conduction delay, action potentials, and epicardial ST-segment during myocardial ischaemia. These measurements should provide new information about ionic and metabolic cellular changes relating to the onset of ventricular arrhythmias.

Action Potentials↗

PubMed1977

Praecordial ST segment elevation. New technique for continuous recording and analysis.

The measurement of praecordial ST segment elevation after myocardial infarction is of value in assessing the natural history of ischaemic injury and the effectiveness of intervention. Hand analysis is, however, time consuming and inaccurate. A technique for continuous recording from 35 praecordial leads and subsequent computer analysis is presented, together with illustrative case studies. Changes in body posture and in heart rate are of importance in subsequent data interpretation.

Adult↗

PubMed1976

Clinical experience with left main coronary artery stenosis.

We report the clinical features and the results of investigation and surgery in 20 patients with significant left main coronary artery stenosis. All had moderate to severe angina; 8 had pain at rest. Three had dyspnoea as a major symptom. The electrocardiogram was abnormal in 17, with evidence of previous myocardial infarction in 10. Of the 11 patients exercised, 8 developed chest pain. Nine patients had a normal left ventriculogram. At coronary angiography all patients had major disease elsewhere in addition to the left main coronary artery stenosis. There were no deaths or major complications associated with this investigation. One patient was unsuitable for surgery because of diffuse left ventricular hypokinesia, one had a fatal myocardial infarction while awaiting operation, and there was one preoperative death. Sixteen of the 17 surgical survivors are free from angina. There has been a significant improvement in the maximum exercise capacity in the 10 patients who had pre- and postoperative exercise tests.

Adult↗

PubMed1976

Reversed liver-spleen ratio and the normal liver-spleen scintigram.

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Animals↗

PubMed1975

Proceedings: Positive correlation of coronary angiographic index with maximal exercise level in angina pectoris.

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Angina Pectoris↗

PubMedDate not supplied

Electrophysiological and haemodynamic effects of a new inotropic agent (UK14275) in the dog.

1. Electrophysiological and haemodynamic effects after intravenous administration of a new inotropic agent (UK14275) have been examined in open-chest dogs under pentobarbitone anaesthesia. 2. UK14275 produced slight shortening of QT interval, ventricular functional refractory period and atrio-ventricular conduction time but did not affect action potential duration or endocardial-epicardial conduction time. 3. Cardiac output and left ventricular dP/dt increased, and systemic vascular resistance fell. 4. An end-systolic pressure gradient developed between left ventricle and aorta attributable to left ventricular cavity obliteration.

Animals↗