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Biomedical subjects

P C Block

Publications and source records attributed to P C Block.

At least 91 records · Page 5Linked to original sources
PubMed1987

Prognostic value of computer-quantitated exercise thallium imaging early after percutaneous transluminal coronary angioplasty.

To develop an approach to predicting adverse events after percutaneous transluminal coronary angioplasty (PTCA), 50 patients had thallium-201 exercise testing within 1 month after successful single vessel coronary angioplasty and were followed up for a mean of 18 months. Adverse events were: 1) clinical events consisting of recurrent angina (17 patients) and myocardial infarction (1 patient); 2) treatment events consisting of repeat coronary angioplasty (10 patients) and coronary bypass surgery (1 patient); and 3) restenosis, defined as a greater than 30% increase in luminal stenosis (15 of 38 recatheterized patients). There were no deaths. Of the clinical, exercise, angiographic and thallium scan variables analyzed by stepwise logistic regression, postangioplasty gradient greater than 20 mm Hg predicted clinical events and treatment events, and the number of segments with slower thallium clearance predicted clinical events, treatment events and restenosis. Using Cox Hazards model regression of survival without events, the number of transient qualitative thallium defects also predicted clinical events and restenosis. At 1 year after angioplasty, 24% of patients with these variables had restenosis compared with only 6% of those without these variables and 36% of patients with these variables had a clinical or treatment event compared with 8% of patients without these variables. Three measures of the adequacy of myocardial perfusion (post-angioplasty gradient, reduced thallium clearance and transient thallium defects) were additive predictors of adverse events after coronary angioplasty with the relative risk being approximately four times greater in patients with these variables than in those without. Such adverse events, therefore, are usually a consequence of inadequate revascularization.

Adult↗
PubMed1987

Arterial changes after percutaneous transluminal coronary angioplasty: results at autopsy.

Light and electron microscopic examinations were performed on 20 coronary artery sites from nine patients who had undergone percutaneous transluminal coronary angioplasty. Twelve successfully dilated sites without prior thrombosis showed evidence of a tear in the luminal surface (with or without fracture of an atheroma) even at 140 days after angioplasty. The tear split through a relatively undistensible intima in 9 (75%) of the 12 sites. Two successfully dilated sites with prior thrombosis showed an intraintimal tear with a widely lacerated fibrous cap and thin mural thrombus. After dilation, the occluded prior nonthrombosed site showed marked protrusion of a separated plaque. An occluded prior thrombosed site after dilation revealed intraintimal canal-like hematoma. Four sites that occluded after balloon passage revealed a dissecting hematoma in three and plaque disruption in the other.

Aged↗
PubMed1987

Percutaneous balloon valvotomy for patients with severe mitral stenosis.

Thirty-five patients with severe mitral stenosis underwent percutaneous mitral valvotomy (PMV). There were 29 female and six male patients (mean age 49 +/- 3 years, range 13 to 87). After transseptal left heart catheterization, PMV was performed with either a single- (20 patients) or double- (14 patients) balloon dilating catheter. Hemodynamic and left ventriculographic findings were evaluated before and after PMV. There was one death. Mitral regurgitation developed or increased in severity in 15 patients (43%). One patient developed complete heart block requiring a permanent pacemaker. PMV resulted in a significant decrease in mitral gradient from 18 +/- 1 to 7 +/- 1 mm Hg (p less than .0001) and a significant increase in both cardiac output from 3.9 +/- 0.2 to 4.6 +/- 0.2 liters/min (p less than .001) and in mitral valve area from 0.8 +/- 0.1 to 1.7 +/- 0.2 cm2 (p less than .0001) Effective balloon dilating diameter per square meter of body surface area correlated significantly with the decrease in mitral gradient but did not correlate with the degree of mitral regurgitation. There was no correlation of age, prior mitral commissurotomy or mitral calcification with hemodynamic results. PMV is an effective nonsurgical procedure for patients with mitral stenosis, including those with pliable valves, those with previous commissurotomy, and even those with mitral calcification.

Adolescent↗
PubMed1986

Assessment of regional myocardial perfusion with thallium imaging during transient left anterior descending coronary arterial occlusion during angioplasty.

To define the jeopardized territory perfused through a single coronary arterial stenosis, thallium-201, 2 mCi, was injected into the pulmonary artery at the onset of the last of a series of percutaneous transluminal coronary angioplasty (PTCA) balloon inflations in 10 patients with single-vessel left anterior descending coronary artery disease. Imaging was begun immediately after PTCA. Arterial thallium activity peaked 30 seconds after injection and decreased to 34 +/- 6% (mean +/- standard error of the mean) of peak activity at the time of balloon deflation. Regional thallium activity during exercise vs PTCA was scored qualitatively and quantitatively. A computer quantification program was used that permitted automatic realignment and normalization of the 2 initial thallium images. Only mean quantitative posterior activity was lower (93 +/- 1% vs 86 +/- 2%, p less than 0.05) on exercise scans compared with PTCA scans. The other 5 segments showed no difference in mean scores. There were no qualitative differences in initial thallium distribution, nor were there qualitative or quantitative differences in the number of abnormal segments or severity of reduction in activity in the segment with the lowest activity. In conclusion, regional thallium myocardial distribution with a single severe stenoses with injection during peak exercise is similar to that after complete coronary occlusion.

Adult↗
PubMed1986

Comparison of contrast x-ray biplane cineangiography and technetium-99m radionuclide scans for measurement of ventricular volumes in human autopsy hearts.

The area-length method is widely used in the determination of left ventricular volume. Although previous studies have reported that this technique overestimates true volume (TV), it is unknown whether this overestimation is the same at different volumes. In the present study, with the use of 10 postmortem human hearts, left ventricular volumes were determined by contrast x-ray biplane cine ventriculography (LVA), biplane radionuclide (LVR), and absolute-counts (LVC) technetium scans, and the results were correlated with TV. LVA correlated well with TV (r = 0.98). LVR correlated well with TV (r = 0.97), and LVR also correlated well with LVA (r = 0.96). Both area-length techniques (LVA and LVR) resulted in overestimation of TV with an upward shift of the regression line of 30.4ml +/- 3.8 (SEM) for LVA and 28.5 +/- 4.4 for LVR. The percentage of overestimation error was significantly greater at smaller left ventricular volumes (error = 33% at TV = 30ml and 10% at TV = 100ml, p less than 0.001). LVC correlated well with TV (r = 0.99), TVA, and LVR but underestimated TV. Thus left ventricular volumes can be reliably obtained from LVR and LVA by means of the area-length method and from LVC. When the area-length method is utilized, the percentage of error in the determination of left ventricular volume is proportional to 1/TV.

Angiocardiography↗
PubMed1986

Thromboxane release during percutaneous transluminal coronary angioplasty.

The reason for coronary artery occlusion following percutaneous transluminal angioplasty (PTCA) remains an enigma. We postulated that alterations in arachidonic acid metabolism might contribute to coronary artery occlusion, particularly if platelets are perturbed and release thromboxane because of mechanical stimuli during PTCA. We serially monitored coronary sinus and peripheral arterial plasma thromboxane (TX) and prostacyclin (by standard radioimmunoassay of the metabolites TXB2 and 6-keto-PFG1 alpha) during PTCA in 10 patients. TX and prostacyclin were unchanged from control in seven uncomplicated procedures. In one patient with vasospasm, no changes were found. In two patients with occlusion, marked increases were measured in coronary sinus plasma TX. Patient No. 1 increased from 390 to 1375 pg/ml. Patient No. 2 increased from 155 to 1425 pg/ml. Both required emergency bypass grafting. No change in 6-keto-PGF1 alpha was found. Uncomplicated PTCA does not alter arachidonic acid metabolism through cyclooxygenase. Vasospasm need not be associated with TX release, but coronary artery occlusion is. TX may play a role in coronary artery occlusion during PTCA because of (1) increased release and (2) unopposed physiologic effects because increases were not found in the physiologic antagonist prostacyclin.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Percutaneous transvenous balloon valvotomy in a patient with severe calcific mitral stenosis.

Percutaneous transvenous balloon mitral valvotomy was performed successfully in a 57 year old man with refractory congestive heart failure due to calcific mitral stenosis. Cardiac surgery was not an option because of other major medical problems. Balloon mitral valvotomy was performed using the transseptal technique. The interatrial septum was dilated with the use of an 8 mm balloon catheter to allow passage of larger balloon valvotomy catheters to the mitral anulus. The procedure resulted in a marked decrease in the diastolic transmitral gradient from 20 to 4 mm Hg. This decrease was associated with an increase in cardiac output from 3.4 to 5.7 liters/min. Mitral valve area increased from 0.7 to 2.5 cm2. Balloon valvotomy did not result in significant mitral regurgitation. This case indicates that further trials are warranted to evaluate percutaneous transseptal mitral valvotomy for the treatment of patients with mitral stenosis.

Calcinosis↗
PubMed1986

Comparison of ejection fraction and pulmonary blood volume ratio as markers of left ventricular function change after coronary angioplasty.

Exercise-induced increases in pulmonary blood volume ratio have been shown to be a sensitive marker of coronary artery disease, and correlate well with exercise-induced increases in left ventricular filling pressure. To compare the impact of single vessel coronary disease on left ventricular systolic function (ejection fraction) versus diastolic filling pressure (pulmonary blood volume) before and after intervention, serial supine exercise gated blood pool scans were performed before and after coronary angioplasty in 32 patients with isolated left anterior descending coronary artery disease. By applying previously established criteria of abnormal ejection fraction (rest less than 50% or failure to rise by 5% with exercise) and pulmonary blood volume ratio (greater than 1.06), 66% of the patients were found to have abnormal responses before angioplasty by ejection fraction compared with 81% abnormal responses by pulmonary blood volume ratio (p = 0.15). After angioplasty, the proportion of patients with abnormal ejection fraction (59%) was essentially unchanged, whereas only 38% continued to have an abnormal pulmonary blood volume ratio (p less than 0.01 compared with before angioplasty). The mean pulmonary blood volume ratio also decreased significantly from 1.15 +/- 0.10 before angioplasty to 1.02 +/- 0.15 after angioplasty (p less than 0.001). It is concluded that in single vessel coronary artery disease: 1) pulmonary blood volume ratio is abnormal at least as frequently as is ejection fraction; 2) in contrast to ejection fraction, pulmonary blood volume ratio improves significantly after successful angioplasty; and 3) pulmonary blood volume ratio may be a more sensitive indicator of changes in ventricular function after an intervention in single vessel coronary disease.

Adult↗
PubMed1985

Increased thallium lung uptake after exercise in isolated left anterior descending coronary artery disease.

Increased thallium lung uptake during exercise correlates with an exercise-induced elevation in left ventricular filling pressure. This finding was analyzed in 48 patients with 1-vessel left anterior descending (LAD) coronary artery disease (CAD) before and after percutaneous transluminal coronary angioplasty. Patients were separated into 2 groups: 13 (27%) patients with increased (group 1) and 35 patients with normal thallium lung uptake (group 2). Compared with group 2, group 1 patients had more severe LAD luminal diameter narrowing (90 +/- 6% vs 81 +/- 11% [mean +/- standard deviation], p less than 0.003); slower clearance of thallium from the LAD territory segments (half-life 13.5 +/- 8.0 vs 6.5 +/- 5.0 hours, p less than 0.007); and more abnormal thallium segments per patient by quantitative criteria (p less than 0.02). After angioplasty, thallium lung uptake became normal in 12 of 13 patients in whom it was previously elevated. Increased thallium lung uptake after exercise occurs in 1-vessel LAD disease, and is related to the severity of ischemia by thallium scan and the severity of stenosis by angiography. Therefore, increased thallium lung uptake identifies a subset of patients with 1-vessel CAD with a greater amount of myocardium at risk.

Adult↗
PubMed1985

Clinical, angiographic, hemodynamic, perfusional and functional changes after one-vessel left anterior descending coronary angioplasty.

Percutaneous transluminal coronary angioplasty (PTCA) was successfully performed in 20 patients with 1-vessel left anterior descending (LAD) coronary artery disease. Exercise capacity in terms of peak workload, heart rate and systolic blood pressure all increased significantly 1 week after PTCA. All patients had some decrease in stenosis size and gradient. All patients except 1 had an improvement in functional class. Eight of 12 patients with abnormal exercise electrocardiograms before PTCA had normal electrocardiograms after the procedure. Exercise thallium-201 (TI-201) myocardial perfusion images obtained in all 20 patients before and 1 week after PTCA were analyzed using a new computer method designed to quantitate regional myocardial TI-201 distribution, redistribution and clearance rate. Significant improvement in TI-201 activity was present in the anterior and septal segments of the left ventricle 1 week after PTCA. This increase in TI-201 uptake was associated with a significant reduction in the amount of TI-201 redistribution between initial and delayed postexercise images in the same regions. TI-201 clearance rate in the segments supplied by the dilated vessel also improved significantly. Abnormal TI-201 lung uptake was seen in 17 patients before and in 4 patients after PTCA. Exercise ejection fraction response and septal wall motion also improved after PTCA of the LAD stenosis in all 17 patients who had exercise radionuclide ventriculography. Improvement in clinical, angiographic and hemodynamic factors as well as in global and regional myocardial perfusion and function occurs after PTCA for 1-vessel LAD coronary artery disease.

Adult↗
PubMed1985

The persistent defect on exercise thallium imaging and its fate after myocardial revascularization: does it represent scar or ischemia?

Persistent defects on serial thallium scans are commonly thought to represent fibrosis or scar. However, such a pattern may also represent severe ischemia. To better understand persistent defects, exercise thallium and resting gated blood pool scans were reviewed in 52 patients pre and post coronary angioplasty for single-vessel left anterior descending (LAD) coronary artery disease, and the fate of persistent defects after successful revascularization was determined. Persistent and transient defects were defined from the average scores of three observers. Ten patients with 16 myocardial segments with persistent defects were compared to another 11 patients with 20 myocardial segments with transient defects. After angioplasty (PTCA), 75% of the regions that had persistent defects and 85% of the regions that had transient defects were normal by visual assessment. In the persistent defect group, only regional wall motion on the resting gated blood pool scan pre PTCA helped to distinguish those segments that would or would not revert to normal. We conclude that regions of persistent defect on thallium scan often revert to normal after PTCA (75%), suggesting that persistent defects may represent hypoperfusion of viable myocardium, and should not preclude consideration of an intervention.

Adult↗
PubMed1985

Underestimation of prosthetic mitral valve areas: role of transseptal catheterization in avoiding unnecessary repeat mitral valve surgery.

In patients with symptoms of heart failure after mitral valve replacement, identification of a stenosed prosthesis may be difficult. Twelve such patients were evaluated, presenting at a mean of 8.4 years after mitral valve replacement (four mechanical, eight porcine). Transvalvular pressure gradients were obtained using both indirect (pulmonary capillary wedge) and direct (transseptal catheterization) measurements of left atrial pressure. In all 12 patients, the diastolic gradient across the prosthetic valve was overestimated when pulmonary wedge rather than transseptal measurements were used. Calculated mitral valve prosthetic area was underestimated by the pulmonary wedge determinations. These findings may be caused by either the phase delay of the pulmonary wedge V wave relative to the transseptal V wave, resulting in a higher diastolic mean left atrial pressure, or the faulty wedge determinations in the setting of pulmonary hypertension, or both. In patients being considered for repeat mitral valve replacement because of prosthetic valve stenosis, transseptal catheterization allows for more accurate determination of prosthetic valve area and more accurately defines the need for repeat mitral valve surgery.

Aged↗