Search PubMed⌕ Search

Biomedical subjects

B S Lewis

Publications and source records attributed to B S Lewis.

At least 145 records · Page 8Linked to original sources
PubMed1984

Improvement in regional ventricular function after percutaneous transluminal coronary angioplasty.

We performed atrial pacing and radionuclide ventriculography in 12 patients before and after percutaneous transluminal coronary angioplasty (PTCA). Successful dilatation was achieved in 9 patients while in 3 the procedure was unsuccessful. Atrial pacing before PTCA showed ischemic dysfunction of the region supplied by the narrowed coronary artery. Regional ejection fraction decreased by 36 +/- 12% during rapid atrial pacing, while global left ventricular ejection fraction fell by 11 +/- 7% with a secondary increase in end-diastolic and end-systolic ventricular volume with the onset of ischemia. After successful PTCA, ischemic dysfunction was ameliorated or abolished. Measurements made at identical heart rates showed that both global and in particular regional left ventricular ejection fraction were significantly higher after successful angioplasty and did not fall during the stress of atrial pacing. There was no improvement in regional or global LV function in patients in whom angioplasty was not successful. The study showed that nuclear ventriculography with the stress of graded atrial pacing was a useful method for analysing the immediate results of coronary angioplasty and for studying its effects on regional myocardial function.

Adult↗
PubMed1984

The effect of nifedipine on normal and ischemic left ventricular function during atrial pacing stress.

We studied 44 patients (group I: 9 with insignificant disease and group II: 35 with significant coronary artery disease) by nuclear angiography during the controlled increase in heart rate by atrial pacing to evaluate the effect of 20 mg of sublingual nifedipine on left ventricular function. Left ventricular volumes were calculated using count-derived changes: end-diastolic (EDE), end-systolic (ESE), stroke volume (SVE) and cardiac output equivalents (COE) and ejection fraction (EF) and ejection rate (ER) were calculated during basal sinus rhythm (C) and at the maximal atrial pacing (AP) rate with and without nifedipine. In normal subjects, AP decreased ventricular volumes. The administration of nifedipine decreased blood pressure but had no further effect on left ventricular volume. In the ischemic ventricle, AP produced reversible ventricular wall paresis with a smaller decrease in EDE, an increase in ESE and a significant fall in EF. Nifedipine induced a striking improvement in EF and ER. This was probably a consequence of afterload reduction and increased coronary blood flow.

Adult↗
PubMed1984

Left ventricular function during asynchronous ventricular pacing: a radionuclide study.

This study was undertaken to assess ventricular volumes and function by radionuclide angiography during asynchronous ventricular pacing in a group of 22 patients who needed an artificial pacemaker. 14 had ischaemic heart disease and 8 had primary disturbances of conduction of the impulse-forming system. The transition from sinus to a paced rhythm or increasing the pacing rate had little effect on patients with primary conduction disturbances. In contrast, in patients with ischaemic heart disease, the transition to a paced rhythm decreased significantly left ventricular end-diastolic (15.3 +/- 4.7%) and stroke (26.3 +/- 4%) volumes, ejection fraction (9.0 +/- 4.4%), and cardiac output (21.0 +/- 3.9%). Pacing at a progressively increasing heart rate showed that each patient had an optimal rate of pacing.

Aged↗
PubMed1984

The hyperacute phase of right ventricular infarction.

In summary, the hyperacute phase of RV infarction presents three possible patterns on the surface ECG (Fig. 3): the typical repolarization picture of hyperacute myocardial infarction, with slope elevation of the ST segment and tall T waves; rounded elevation of the ST segment, where the typical changes are "damped" by negative or posterolaterally directed, LV repolarizing forces; and ST elevation concave upward in the right chest leads, where anteriorly directed, underlying left ventricular ST segment and T wave vectors enhance the hyperacute picture.

Acute Disease↗
PubMed1983

Localization of lesions in the coronary circulation.

The location of coronary artery narrowings in coronary disease (CAD) is of considerable importance in assessing the mass of myocardium at risk as well as patient prognosis. The detailed distribution of coronary lesions was mapped in 302 patients with CAD who had coronary angiography for chest pain. All identifiable coronary lesions were measured manually and the site and degree of narrowing were stored in a computer-based multisegmental model of the coronary tree. A high prevalence of CAD was found in proximal vessels and especially at, or adjacent to, proximal points of branching. In the left anterior descending coronary artery, the lesions were most prevalent immediately after the first diagonal branch and at the origin of this branch. In the right coronary artery, there was a high prevalence of narrowing between the infundibular and acute marginal branches and specifically around the origin of the right ventricular branch. In the left circumflex coronary artery, there was a predilection for narrowing in and around the origin of the first marginal branch. When a ramus intermedius was present, its origin was frequently the site of narrowing.

Adult↗
PubMed1983

Hypertrophic cardiomyopathy in South African Blacks.

Hypertrophic cardiomyopathy (HCM) has been considered rare among the Black population of southern Africa. We report 7 patients with the disease who presented during a 14-month period. Current concepts in the approach to the diagnosis and treatment of HCM are discussed. It is possible that with greater awareness of the occurrence of the condition in Blacks the diagnosis of HCM will be made in more members of this population group.

Adult↗
PubMed1983

A graphic computerized system for reporting and analysis of coronary angiograms.

A graphic computer based system for coronary angiographic reporting and data storage has been developed. It uses a multisegmental model of the coronary tree so that precise localization of coronary lesions can be made in relation to major branches. The percentage narrowing of the vessel, the length of the lesion, and diameter of the distal coronary vessel can be measured. Collateral vessels, coronary artery bypass grafts, and coronary artery spasm are recorded. The system is simple to use and useful for routine clinical reporting and for detailed analysis of coronary lesions.

Angiography↗
PubMed1983

The use of calcium with verapamil in the management of supraventricular tachyarrhythmias.

Verapamil, a calcium channel blocking drug, terminates supraventricular arrhythmias but may have a negative inotropic effect and produce peripheral vasodilatation and hypotension. We studied the efficacy of intravenous calcium gluconate in reversing or preventing the hypotensive effect of verapamil in 31 patients with atrial tachyarrhythmias. In 21 instances, verapamil was given first, and in 13 calcium was used as pretreatment before the administration of verapamil. Calcium gluconate, when given as pretreatment, prevented the fall in blood pressure induced by verapamil, and when given after verapamil restored blood pressure to control values. The administration of calcium did not alter the antiarrhythmic effect of verapamil.

Adult↗
PubMed1983

Early postoperative assessment of coronary artery bypass surgery using nuclear left ventriculography and atrial pacing.

Nuclear ventriculography (MUGA) was performed in 22 patients at rest and during the stress of right atrial pacing 6 to 8 days after coronary artery bypass surgery. In 7 patients the MUGA-atrial pacing test was positive for ischemia with chest pain, electrocardiographic ST depression and/or a decrease in global left ventricular ejection fraction of greater than 10%. All 7 patients subsequently developed angina pectoris with a positive treadmill test (performed at a median time of 14 months after operation). In 15 patients, the early postoperative MUGA-atrial pacing test was negative. In this group, 3 patients subsequently developed angina pectoris with a positive treadmill test in one. The sensitivity of the 'one week' early postoperative MUGA-atrial pacing in the identification of patients with residual myocardial ischemia was high (88% for positive GXT, p less than 0.0001; 70% for chest pain, p less than 0.005) with 100% specificity. The early postoperative MUGA scan was also useful in predicting later shortness of breath on exertion and there was a significant correlation between the early resting ejection fraction and the exercise capacity of the patient subsequently. The information obtained from an early postoperative MUGA-atrial pacing study may have far-reaching and important practical application in selecting patients for early recatheterization, possible fibrinolysis and/or possible cardiac reoperation.

Adult↗
PubMed1983

Frame by frame analysis of left ventricular function. Quantitative assessment of regional and temporal function.

We made a frame by frame analysis of the left ventricular cineangiogram to quantitate normal regional left ventricular function. Two different methods were used: contraction of the left ventricle towards a fixed point at the center of its long axis, and a pattern of contraction normal to the outline of the ventricle. Each method was used with and without correction for rotation and translational movement during systole. Left ventricular contraction and relaxation were represented graphically on a three-dimensional perspective plot and also using contour mapping techniques. The normal values and standard deviation were calculated for the extent, velocity and time course of ventricular contraction and relaxation in each region of the ventricle. The study provided a graphic visual display of the regional contractile pattern of the normal ventricle.

Adult↗
PubMed1983

Recurrent obstruction and thrombolysis of the right coronary artery.

A patient presented twice with the hyperacute phase of inferior wall myocardial infarction. Emergency coronary angiography was undertaken on each occasion and the occluded right coronary artery reopened by intracoronary thrombolysis using urokinase. The patient subsequently underwent successful percutaneous transluminal coronary angioplasty to dilate the underlying subtotal obstructive lesion in the proximal right coronary artery. The sequence of events in this patient demonstrates that (1) acute coronary thrombolysis can preserve ventricular myocardium, (2) recurrent thrombolysis can be performed successfully in the same artery in the same patient, and (3) coronary angioplasty may be an effective method of dilating the underlying coronary narrowing after coronary thrombolysis.

Adult↗