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Biomedical subjects

D Kilpatrick

Publications and source records attributed to D Kilpatrick.

81 records · Page 5Linked to original sources
PubMed1977

QRS voltage of the electrocardiogram and Frank vectorcardiogram in relation to ventricular volume.

Left ventricular volumes were estimated in 59 patients, who were investigated by single plane ventriculography and coronary arteriography. The relation of the left ventricular end-diastolic volumes to the QRS voltage of the 12-lead electrocardiograms and Frank vectorcardiograms was examined. It was found that the maximum spatial QRS voltage and the R wave voltage of leads V5 and V6 in patients without left ventricular hypertrophy were inversely correlated with end-diastolic volume. This inverse relation of QRS voltage and left ventricular volume may explain loss of QRS voltage with dilatation of the heart. In patients with left ventricular hypertropy QRS voltage is usually positively correlated with the degree of hypertrophy, but there is no significant correlation in the presence of cardiac dilatation. If the results of this study are extrapolated to patients with left ventricular hypertrophy and cardiac dilatation, then the inverse correlation of volume and QRS voltage may reduce the diagnostic sensitivity of unipolar chest lead and vectorcardiographic criteria of left ventricular hypertrophy.

Cardiac Volume↗
PubMed1976

Exercise vectorcardiography in diagnosis of ischaemic heart-disease.

The changes in the cardiac electric field during exercise have been studied by conventional vectorcardiographic techniques. Criteria have been developed to distinguish the changes seen in patients with coronary-artery disease proven angiographically from the changes in patients with normal coronary arteriograms. These criteria were derived from a learning set of 105 patients. Vectorcardiograms were taken immediately before and immediately after a maximal treadmill exercise test. In this group of 105 patients--72 with abnormal coronary arteries and 33 with normal coronary arteries--vectorcardiography before and after exercise diagnosed correctly 86% of the abnormals and 82% of the normals. This gives a sensitivity of 86% and a specificity 82%. ST-segment analysis in the same group gave a sensitivity of 60% and a specificity of 85%. The same criteria applied blind to a second testing set of 92 patients gave a sensitivity of 84% and a specificity of 65%. In the same group ST-T analysis gave a sensitivity of 56% and a specificity of 78%. The sensitivity with these criteria compares favourably with the best results so far achieved with ST-segment analysis aided by computer. This technique can be easily used by the clinician and improves the diagnostic accuracy of exercise testing.

Angina Pectoris↗
PubMedDate not supplied

The effects of nifedipine on the systemic and coronary vascular beds of the sheep: a potential method for induction of ischaemia.

Nifedipine has been reported to aggravate symptoms of ischaemic heart disease in some patients. To investigate the possible reasons for this, vascular resistance changes in the systemic and coronary beds of sheep were compared with and without coronary artery stenoses. In six anaesthetized sheep, the dose-response curve comparing vascular resistance to nifedipine dose showed greater sensitivity than that reported for either dogs or humans. The coronary vascular bed was more reactive than the systemic vascular bed but this difference did not reach a level of statistical significance. With fixed non-elastic proximal coronary artery stenoses, the relationship of both coronary flow and coronary resistance to a standard dose of nifedipine (5 micrograms/kg) was indirectly related to the degree of stenosis. With stenosis reducing flow at rest by 50% or more, nifedipine usually produced a reduction in coronary flow in the stenosed artery and associated ST elevation, consistent with severe ischaemia in the distribution of the coronary. This effect is related to the reduction in perfusion pressure.

Animals↗
PubMedDate not supplied

Coronary and peripheral vascular resistance in the anaesthetized diabetic sheep.

To determine whether vascular resistance was altered in diabetes, the vascular resistance in both the peripheral arterial bed and the circumflex coronary artery was compared in six normal and five diabetic adult sheep, under pentobarbitone anaesthesia. Diabetes induced by alloxan significantly increased blood glucose (15.6 mmol/l, s.e.m. = 2.8, vs 5.5 mmol/l, s.e.m. = 0.6; P greater than 0.001) compared with controls. Systolic blood pressure was lower in diabetics (92 mmHg, s.e.m. = 12, vs 123 mmHg, s.e.m. = 5; P less than 0.025) as was diastolic blood pressure (73 mmHg, s.e.m. = 15, vs 104 mmHg, s.e.m. = 4; P greater than 0.05). Basal peripheral resistance was lower in diabetics than controls (36.0 mmHg.min/l, s.e.m. = 7.9, vs 42.3 mmHg.min/l, s.e.m. = 2.8), but not significantly so. Methoxamine markedly increased peripheral vascular resistance in both groups, but did not change coronary vascular resistance, due to autoregulation. The dose-response curves of peripheral or coronary arteries to methoxamine showed no significant difference between diabetic and control sheep. Dose-response curves for isoprenaline and noradrenaline infusion suggested there may be altered beta-receptor sensitivity in diabetes. In conclusion, there are marked differences in the vascular beds of diabetic and normal sheep under basal conditions. In contrast to previous studies, alpha-adrenoceptors are not different in diabetics, but further studies in unanaesthetized animals are indicated, as beta-receptor sensitivity may be altered in diabetes.

Acetylcholine↗