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Biomedical subjects

A T Weiss

Publications and source records attributed to A T Weiss.

At least 73 records · Page 4Linked to original sources
PubMed1985

Factors that determine the direction and magnitude of precordial ST-segment deviations during inferior wall acute myocardial infarction.

Sixty-one patients with inferior acute myocardial infarction (AMI) and no evidence of prior AMI were studied to determine which factors influence the magnitude of precordial ST-segment depression. In the total study group, there was a significant but weak correlation between the magnitude of precordial ST-segment depression and the magnitude of inferior ST-segment elevation (r = -0.46, p less than 0.001). In the 29 patients with evidence of concomitant right ventricular (RV) involvement, precordial ST-segment depression was significantly smaller both in absolute terms (-1.3 +/- 1.8 vs -2.8 +/- 1.9 mm, p less than 0.01) and relative to the magnitude of inferior ST-segment elevation (ratio of -0.2 +/- 1.0 vs -1.1 +/- 0.5, p less than 0.01), whereas in the 15 patients with lateral ST-segment elevation (greater than or equal to 1 mm in lead V6), precordial ST-segment depression was significantly greater both in absolute terms (-3.5 +/- 2.3 vs -1.6 +/- 1.7 mm, p less than 0.01) and relative to the magnitude of inferior ST-segment elevation (ratio of -1.1 +/- 0.8 vs -0.5 +/- 0.9, p less than 0.02). Consistent with these findings, the correlation between the magnitudes of precordial and inferior ST-segment deviations was considerably improved when only the 24 patients with neither evidence of RV involvement nor lateral ST-segment elevation were analyzed (r = 0.89, p less than 0.001, n = 24). These data suggest that in patients with inferior AMI, there is a reciprocal relation between precordial and inferior ST-segment deviations, which is distorted by concomitant RV involvement and by concomitant lateral left ventricular wall involvement.

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PubMed1985

Precordial ST segment depression during acute inferior myocardial infarction: early thallium-201 scintigraphic evidence of adjacent posterolateral or inferoseptal involvement.

To investigate the myocardial perfusion correlates of precordial ST segment depression during acute inferior myocardial infarction, a rest thallium-201 scintigram and a closely timed 12 lead electrocardiogram were obtained within 6 hours of the onset of infarction in 44 patients admitted with their first acute inferior myocardial infarction. Thirty-six patients demonstrated precordial ST segment depression (group 1) and eight did not (group 2). A perfusion defect involving the inferior wall was present in all 44 patients. Additional perfusion defects of the adjacent posterolateral wall (n = 20), the ventricular septum (n = 9) or both (n = 6) were present in 35 of 36 patients from group 1 compared with only 1 of 8 patients from group 2 (p less than 0.001). There was no significant difference in the frequency of multivessel coronary artery disease or disease of the left anterior descending artery between group 1 and group 2 or between patients with and those without a thallium-201 perfusion defect involving the ventricular septum. Thus, precordial ST segment depression during an acute inferior myocardial infarction is associated with thallium-201 scintigraphic evidence of more extensive involvement of the adjacent posterolateral or inferoseptal myocardial segments, which probably reflects the extent and pattern of distribution of the artery of infarction, rather than the presence of coexistent multivessel coronary artery disease or disease of the left anterior descending artery.

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PubMed1984

Left ventricular volumes and function during atrial pacing in coronary artery disease: a radionuclide angiographic study.

This study set out to determine the pathophysiologic changes in the left ventricle during atrial pacing in 22 patients with coronary artery disease. Graduated right atrial pacing to a rate of 160 beats/min, or the induction of angina pectoris or significant ST depression was undertaken. Ventricular volumes were measured at rest and at rates of 100, 120, 140 and 160 beats/min using radionuclide angiography. The volumes at a pacing rate of 100 beats/min were used as a reference standard (100%). In the 22 patients with coronary artery disease, left ventricular end-diastolic volume decreased from 118 +/- 3% at rest to 80 +/- 5% at a rate of 160 beats/min; stroke volume from 121 +/- 3% to 54 +/- 5%; and ejection fraction (EF) from 49 +/- 3% to 37 +/- 5%. End-systolic volume decreased from 118 +/- 4% at rest, reached its minimal value of 94 +/- 5% at a rate of 120 beats/min and then increased slightly to 106 +/- 9% at 160 beats/min. Cardiac output and blood pressure did not change significantly. Compared to the control group of 10 normal subjects, the patients had a significantly smaller decrease in end-diastolic volume and end-systolic volume than in normal control subjects. EF in the normal subjects did not change. Blood pressure, cardiac output and stroke volume were similar in both groups. Atrial pacing tachycardia induced reversible ventricular dysfunction with a decrease in EF. Stroke volume was maintained because of relative ventricular dilatation.

Adult↗
PubMed1984

Left ventricular function during atrial pacing: a radionuclide angiographic study.

Multigated radionuclide angiography was performed at rest and during atrial pacing in 10 normal subjects. Left ventricular volumes in diastole and systole were measured by total counts in the region of interest of the left ventricle. Stroke volume, cardiac output, ejection fraction, and rates of ejection for each heart rate were calculated. As heart rate increased, there was a gradual decrease in end-diastolic, end-systolic, and stroke volumes without a significant change in cardiac output and ejection fraction. Ejection fraction rate increased and the uncorrected ejection rate decreased with the increase in heart rate. The normal response to tachycardia induced by atrial pacing was a decrease in ventricular volumes without a change in ejection fraction or cardiac output.

Adult↗
PubMed1984

Regional and global left ventricular function during intra-aortic balloon counterpulsation in patients with acute myocardial infarction shock.

We evaluated the improvement in hemodynamic and left ventricular (LV) function in 15 patients with acute myocardial infarction and cardiogenic shock, who were treated with intraaortic balloon counterpulsation (IABP). They were studied by flow-directed right heart catheterization and nuclear angiography. IABP decreased LV end-diastolic volume from 134 to 114 ml and LV end-systolic volume from 100 to 72 ml. LV stroke volume increased from 34 to 42 ml and cardiac output from 3.0 to 3.6 L/min. Global LV ejection fraction increased from 27.6% to 36.1%, and this was due to improvement in regional ejection fraction in ischemic areas. Pulmonary capillary wedge pressure and pulmonary blood volume decreased. Right ventricular ejection fraction also increased significantly. IABP improved LV function in acute myocardial infarction.

Adult↗
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.

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PubMed1983

Intravenous verapamil therapy in imminent myocardial infarction.

We studied 16 patients with small myocardial infarction who had further episodes of chest pain with ST-segment elevation, a sign of transmural myocardial ischemia and imminent infarction extension. Coronary angiography in 14 showed a critical lesion in 13. Intravenous verapamil abolished chest pain and ST-segment elevation. It caused a fall in right atrial and left ventricular end-diastolic pressures (LVEDP) and cardiac output, reflex systemic vasoconstriction, and a rise in systemic vascular resistance. There was no reflex tachycardia. Volume expansion raised LVEDP and restored a normal cardiac output. Accelerated junctional rhythm with isorhythmic A-V dissociation occurred in 5 patients. Two patients sustained a transmural infarction, 10 underwent coronary artery bypass grafting, and 4 are symptom-free with oral treatment. Intravenous treatment was an effective method of treating acute episodes of transmural myocardial ischemia and preventing their recurrence in patients with critical coronary artery narrowing. Continuous verapamil infusion stabilized the patients' condition and enabled smooth coronary angiography and induction of anesthesia for surgery.

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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

Nonsurgical myocardial revascularization: initial experience with percutaneous transluminal coronary angioplasty.

Coronary artery atheromata obstruct coronary blood flow and produce myocardial ischemia. Percutaneous transluminal coronary angioplasty (PTCA) was performed to dilate narrowed coronary arteries on 16 occasions in 15 patients with severe proximal coronary artery narrowings and significant clinical angina pectoris. The lesions involved the left-anterior descending (LAD) coronary artery in nine patients (10 dilatation procedures), the right coronary artery (RCA) in five, and the circumflex coronary artery in one. Successful dilatation was achieved on nine occasions (56%): in 7 of the 10 LAD lesions (70%), in 2 of the 5 RCA lesions (40%), but not in the patient with circumflex disease. Successful dilatation was accompanied by a significant improvement in symptoms and in myocardial performance, as judged by atrial pacing MUGA (multigated) ventriculography. The ischemic response of the ventricle to stress the significantly reduced or abolished. PTCA is a useful, nonoperative method for dilating obstructed coronary arteries and for improving myocardial blood flow.

Adult↗
PubMed1983

Atrial pacing thallium scintigraphy in the evaluation of coronary artery disease.

A study was undertaken to examine the value of rapid atrial pacing and thallium-201 scintigraphy in the evaluation of ischemic heart disease. Ten subjects with angiographically normal coronary arteries and 31 patients with coronary artery disease were studied. Six of these patients were studied after coronary artery bypass surgery. Coronary ischemia or infarction could be diagnosed from the ECG alone (rest and atrial pacing) in 87% of the patients with a greater than or equal to 50% narrowing of a coronary artery. The ECG and scintiscan (at rest and pacing) together had a sensitivity of 100%. The ECG could not identify the site of stress-induced ischemia. Rapid atrial pacing with scintigraphy identified 91% of those patients with a right coronary artery narrowing (greater than 50%), 85% with a narrowing of the left anterior descending coronary artery, but only 33% with a narrowing of the circumflex coronary artery. The scintiscan correctly identified 40% of arteries with a 50 to 89% narrowing, 75% with a 90 to 99% narrowing and 88% with a complete obstruction. The scintiscan predicted single- and double-vessel disease, but underestimated the number of vessels involved in patients with triple-vessel disease. This technique was also useful in assessing the patency of implanted coronary artery bypass grafts. Rapid atrial pacing is a simple and safe method of inducing ischemia, while thallium scintigraphy shows the site, extent and severity of coronary artery disease.

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