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Biomedical subjects

R S Stack

Publications and source records attributed to R S Stack.

At least 91 records · Page 5Linked to original sources
PubMed1988

Comparison of two dose regimens of intravenous tissue plasminogen activator for acute myocardial infarction.

Two dosing schedules of intravenous tissue plasminogen activator (t-PA) for acute myocardial infarction were compared in a multicenter trial. At 2.95 +/- 1.1 hours from onset of chest pain, 386 patients received 150 mg of intravenous t-PA. For the first 178 patients (group A), 60 mg were given in the first-hour dose and the remaining 90 mg were infused over 7 hours. In the subsequent 208 patients (group B), the first-hour dose was 1.0 mg/kg and the remaining 150 mg were given over 5 hours. At initial angiography 94 +/- 30 minutes into therapy, the infarct vessel patency was 64% in group A versus 75% in group B (p = 0.02). By final angiography with up to 4 selective contrast injections, patency was 68% versus 77%, respectively (p = 0.06). Repeat angiography at 7 to 10 days demonstrated reocclusion in 17% of group A and 13% of group B patients (p = 0.35). There was no difference in fibrinogen nadir or mean hematocrit drop between the 2 groups: 120 mg/dl and 11 points, respectively, in group A compared with 120 mg/dl and 10 points in group B. However, bleeding was reduced in group B patients as evident by a decrease in requirement for greater than or equal to 2 units of packed red blood cell transfusion (group A 36%, group B 27%, p = 0.05) and lower incidence of gastrointestinal bleeding (group A 12%, group B 4%, p = 0.002). To further study the importance of weight adjustment, patients were divided into 2 groups according to weight (less than or equal to 90 kg versus greater than 90 kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1988

Survival and cardiac event rates in the first year after emergency coronary angioplasty for acute myocardial infarction.

One year survival and event-free survival rates were analyzed in 342 patients with acute myocardial infarction who were consecutively enrolled in a treatment protocol of early intravenous thrombolytic therapy followed by emergency coronary angioplasty. Ninety-four percent of the patients achieved successful reperfusion, including 4% with failed angioplasty whose perfusion was maintained by means of a reperfusion catheter before emergency bypass surgery. The procedural mortality rate was 1.2% and the total in-hospital mortality rate was 11%. Ninety-two percent of surviving nonsurgical patients who underwent repeat cardiac catheterization were discharged from the hospital with an open infarct-related artery. The related cumulative 1 year survival rate for all patients managed with this treatment strategy was 87%, and the cardiac event-free survival rate was 84%. The 1 year survival for hospital survivors was 98% and the infarct-free survival rate was 94%. Multivariable analysis identified the following factors as independent predictors of subsequent cardiovascular death: cardiogenic shock, greater age, lower ejection fraction, female gender and a closed infarct-related vessel on the initial coronary angiogram. Among patients with cardiogenic shock, despite a 42% in-hospital mortality rate, only 4% died during the first year after hospital discharge. Similarly, the in-hospital and 1 year postdischarge mortality rates were 19 and 4%, respectively, for patients with an initial ejection fraction less than 40, and 25 and 3%, respectively, for patients greater than 65 years. An aggressive treatment strategy including early thrombolytic therapy, emergency cardiac catheterization, coronary angioplasty and, when necessary, bypass surgery resulted in a high rate of infarct vessel patency.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Emergency coronary artery bypass surgery preserves global and regional left ventricular function after intravenous tissue plasminogen activator therapy for acute myocardial infarction.

Emergency coronary bypass surgery was performed in 24 (6.2%) of 386 consecutive patients enrolled in the Thrombolysis and Angioplasty in Myocardial Infarction (TAMI) Multicenter Trial. Intravenous tissue plasminogen activator was administered 2.6 +/- 0.7 h and bypass surgery was performed 7.3 +/- 1.9 h after the onset of infarction. Infarct artery patency was achieved in 21 (88%) of the 24 patients (pharmacologically in 18 or mechanically with coronary angioplasty in 3) in the catheterization laboratory before bypass surgery. The indication for surgery was left main or equivalent coronary artery disease in 7 patients, coronary anatomy unsuitable for angioplasty in 4 patients and unsuccessful coronary angioplasty in 13 patients. A coronary perfusion catheter was inserted before surgery in 11 of 13 patients with unsuccessful angioplasty. All three deaths occurred postoperatively in patients with preoperative cardiogenic shock. Three patients required surgical reexploration for postoperative hemorrhage. Comparison of preoperative and predischarge contrast left ventriculograms demonstrated significant preservation of global (left ventricular ejection fraction 49 +/- 6 to 56 +/- 6%; p = 0.008) and regional (standard deviation/chord -2.6 +/- 0.5 to -1.5 +/- 1.1; p = 0.001) left ventricular function. Emergency coronary bypass surgery can be performed with a low morbidity and mortality in patients treated with intravenous tissue plasminogen activator therapy for acute myocardial infarction. Such therapy is associated with significant preservation of global and regional (infarct zone) left ventricular function.

Adult↗
PubMed1988

Transluminal intracoronary reperfusion catheter: a device to maintain coronary perfusion between failed coronary angioplasty and emergency coronary bypass surgery.

The reperfusion catheter is a 4.3F catheter with 30 holes over its distal 10 cm. It is used to maintain coronary blood flow in patients awaiting emergency coronary bypass surgery after failed coronary angioplasty. The insertion of the reperfusion catheter was attempted in 20 patients (14 with total occlusion and 6 with severe residual stenosis judged to be in jeopardy of reclosure before operation). The reperfusion catheter was successfully placed across the obstruction in 18 patients (90%). After successful insertion of the reperfusion catheter, 16 patients had good anterograde flow (Thrombolysis in Myocardial Infaction [TIMI] trial grade II or III); angiographic improvement was associated with significant lessening of ST segment elevation as well as a decrease in chest pain in most patients. Two patients had poor or absent anterograde flow (TIMI grade O or I) because of extensive preexisting intracoronary thrombosis; one died from refractory ventricular fibrillation. In each of the remaining patients emergency coronary bypass surgery was performed with no deaths or significant cardiac complications. The reperfusion catheter is a safe and effective method to reestablish and maintain coronary blood flow before coronary bypass surgery after failed coronary angioplasty. Because there is the potential risk of serious complications, particularly thrombus formation within this catheter, the reperfusion catheter should be used cautiously and the patient should undergo immediate bypass surgery.

Angioplasty, Balloon↗
PubMed1988

Coronary perfusion during acute myocardial infarction with a combined therapy of coronary angioplasty and high-dose intravenous streptokinase.

Two hundred and sixteen patients with acute myocardial infarction were treated with immediate infusion of high-dose (1.5 million units) intravenous streptokinase followed by emergency coronary angioplasty. The infarct lesion was crossed and dilated in 99% and persistent coronary perfusion after the procedure was achieved in 90% (including 3% with significant residual stenosis). Total in-hospital mortality was 12%. Multivariable analysis showed a higher hospital mortality with cardiogenic shock (41% vs 5% without shock), older age, lower left ventricular ejection fraction, and female sex. Final patency of the infarct-related vessel was determined by follow-up in-hospital cardiac catheterization. Coronary reocclusion occurred in 11% (symptomatic in 7%, treated with emergency angioplasty or bypass surgery; silent in 4%, treated medically). Of the surviving patients with successful initial establishment of infarct vessel patency, 94% were discharged from the hospital with an open infarct artery or a bypass graft to the infarct vessel. There was significant improvement in both ejection fraction (44% to 49%; p less than .0001) and regional wall motion in the infarct zone (-3.0 SD to -2.4 SD; p less than .0001) among patients with persistent coronary perfusion and insignificant residual stenosis at the time of the follow-up cardiac catheterization. Thus, a treatment strategy for acute myocardial infarction that includes immediate administration of streptokinase followed by emergency coronary angioplasty, and coronary bypass surgery when necessary, results in a high rate of early and sustained patency of the infarct-related vessel.

Angioplasty, Balloon↗
PubMed1988

Myocardial protection during coronary angioplasty with an autoperfusion balloon catheter in humans.

An autoperfusion balloon catheter was developed to allow passive myocardial perfusion during inflation through a central lumen and multiple side holes in the shaft proximal and distal to the balloon. We report its safety and efficacy in 11 patients undergoing elective angioplasty to a single coronary lesion. Each lesion was dilated three times with the autoperfusion inflation bracketed between two inflations by standard angioplasty catheters. Chest pain score, 12-lead electrocardiogram, heart rate, and mean aortic pressure were recorded before each inflation and at 1-minute intervals after inflation. Inflation duration during autoperfusion angioplasty (513 +/- 303 seconds) was longer than for the pre- (107 +/- 55 seconds, p = 0.0004) and post- (139 +/- 71 seconds, p = 0.0006) standard dilatations. The maximum ST-segment elevation and depression in any lead during autoperfusion angioplasty (0.3 +/- 0.5 and 0.6 +/- 0.8 mm) was significantly less than for the pre- (2.4 +/- 1.7 mm, p = 0.002 and 2.2 +/- 1.3 mm, p = 0.0004) or post- (1.9 +/- 1.3 mm, p = 0.002 and 1.6 +/- 1.3 mm, p = 0.018) standard dilatations at the same point in time. Maximal chest pain score during autoperfusion (3.2 +/- 3.5) was lower than for the pre- (6.1 +/- 2.1, p = 0.003) but not the post- (5.2 +/- 3.1, p = 0.07) standard angioplasty. All 11 patients underwent successful, uncomplicated procedures. We conclude that this autoperfusion catheter significantly reduces ischemic symptoms and signs during coronary angioplasty, allowing prolonged periods of balloon inflation.

Angioplasty, Balloon↗
PubMed1988

Failure of simple clinical measurements to predict perfusion status after intravenous thrombolysis.

To determine whether coronary patency could be detected early during thrombolytic therapy, commonly used markers of perfusion were recorded in 386 patients with acute myocardial infarction treated with tissue plasminogen activator. Infarct artery angiography 90 minutes after initiation of therapy was used to determine perfusion status. Of patients with complete resolution of ST segment elevation before the angiogram, 96% (95% confidence interval, 79% to 100%) showed perfusion on the angiogram, and among those with partial improvement, 84% (95% confidence interval, 76% to 90%) showed perfusion, but these findings occurred in only 6% and 38% of patients respectively. When complete resolution of chest pain occurred before the angiogram, 84% of patients (95% confidence interval, 75% to 90%) showed perfusion, but this finding occurred in only 29% of patients. Although arrhythmias occurred frequently in the first 90 minutes of therapy, none were associated with a higher patency rate. No other factors predicted coronary patency. A logistic regression model showed 25% of patients with 90% or greater probability of patency, but 56% of patients with no ST segment or symptom resolution had patent arteries.

Angina Pectoris↗
PubMed1987

A randomized trial of immediate versus delayed elective angioplasty after intravenous tissue plasminogen activator in acute myocardial infarction.

We compared the efficacy of immediate coronary angioplasty after acute myocardial infarction with that of elective angioplasty at 7 to 10 days in patients treated initially with intravenous tissue plasminogen activator. The plasminogen activator (150 mg) was administered 2.95 +/- 1.1 hours after the onset of symptoms, to 386 patients with acute myocardial infarction. Ninety minutes later, patency of the coronary artery serving the area of the infarct was demonstrated by coronary angiography in 288 patients (75 percent). Bleeding problems were frequently encountered, as evidenced by an average drop in hematocrit of 11.7 +/- 6.5 points from base line to nadir and by a need for transfusion not related to bypass surgery in 70 patients (18 percent). After successful thrombolysis, 197 patients with a patent but severely stenotic vessel suitable for angioplasty were randomly assigned to immediate angioplasty (n = 99) or, if indicated 7 to 10 days after infarction, to deferred (elective) angioplasty (n = 98). The incidence of reocclusion was similar in the two groups: 11 percent in the group assigned to immediate angioplasty and 13 percent in the group assigned to elective angioplasty. Neither group had a significant improvement in global left ventricular function, and regional wall motion in the infarct zone improved to a similar extent in the two groups. In the elective-angioplasty group, the rate of crossover to emergency angioplasty for recurrent ischemia was 16 percent (whereas 5 percent of the immediate-angioplasty group required emergency repeated angioplasty; P = 0.01). In 14 percent of the patients in the elective group, the stenosis was substantially reduced by the time of the seven-day follow-up angiography, obviating the need for angioplasty. We conclude that in patients with initially successful thrombolysis and suitable coronary-artery anatomy, immediate angioplasty offers no clear advantage over delayed elective angioplasty.

Angioplasty, Balloon↗
PubMed1987

Validation of in vivo two-dimensional echocardiographic dimension measurements using myocardial mass estimates in dogs.

The accuracy of in vivo measurements of left ventricular wall thickness and chamber size by means of two-dimensional echocardiography was investigated by comparing left ventricular mass estimates obtained at end diastole in 15 closed-chest dogs with a wide range of left ventricular weights. The systolic and diastolic echocardiographic mass estimates were compared with the actual weights of the freshly excised, stripped left ventricles immediately following death. The mean +/- SD of the weighed mass of the excised ventricles was 104 +/- 25 gm. The mean predicted left ventricular mass with the use of the cylinder-ellipse geometric model and gross anatomic sections corresponding to the echocardiographic imaging planes was 106 +/- 26 gm (r = 0.97 compared to the actual weight). The mean echocardiographic estimate of left ventricular mass at end diastolic was 107 +/- 24 gm (r = 0.98 compared to the weight) and 105 +/- 26 gm at end systole (r = 0.95 compared to the weight). The correlation between the echocardiographic mass estimate at end diastole and the echo mass estimate at end systole was 0.95. Regression analysis failed to demonstrate a significant over- or underestimation of the actual weight by the calculated mass with the use of either the gross anatomic or the in vivo echocardiographic dimension measurements.

Animals↗
PubMed1986

Catheter reperfusion to allow optimal coronary bypass grafting following failed transluminal coronary angioplasty.

At present, intimal dissection, restenosis, or vessel closure occurs in approximately 5 to 10% of patients undergoing percutaneous transluminal coronary angioplasty. Coronary artery bypass grafting is usually required to remedy this complication and prevent substantial myocardial damage. The results of these revascularization procedures, however, are less satisfactory than those of elective coronary bypass grafting. Hemodynamic instability of the patients and the presence of ongoing myocardial ischemia usually necessitate that the operations be performed on an emergent basis. This report describes a series of 9 patients who had either dissected or re-stenosed coronary arteries at the time of angioplasty, as well as acute onset of ischemic symptoms. All underwent emergent coronary bypass grafting, but once it became apparent that angioplasty had failed, a specially designed reperfusion catheter was placed across the coronary lesion to reestablish blood flow to the ischemic area of myocardium. This catheter was removed after aortic cross-clamping and delivery of cardioplegic solution. The presence of the catheter thus reduced the ischemic period to the interval from the onset of dissection until the positioning of the catheter across the lesion. In all patients, the catheter temporarily reestablished coronary blood flow to the region of ischemic myocardium, thereby producing resolution of symptoms, and allowed antegrade delivery of cardioplegic solution infused into the aortic root to this area of myocardium. This, in turn, made it possible to perform the subsequent coronary bypass operation as a controlled, optimal revascularization procedure.

Angioplasty, Balloon↗
PubMed1986

The spectrum of pathology associated with percutaneous transluminal coronary angioplasty during acute myocardial infarction.

The purpose of this study was to determine at necropsy the morphologic consequences of percutaneous transluminal coronary angioplasty performed during acute myocardial infarction. The heart was examined in four patients who died between 6 hours and 4 days after coronary angioplasty. The patients had angioplasty of the left main coronary artery (one patient), left anterior descending coronary artery (two patients) and left circumflex coronary artery (one patient). Necropsy revealed residual stenosis, intimal hemorrhage and plaque disruption in all four patients. Also noted were distal embolization of plaque elements (two patients) and thrombotic occlusion of the coronary artery (one patient). In conclusion, the morphologic changes after angioplasty are varied. These changes illustrate the mechanisms of angioplasty and some of the complications that can be expected in a small number of cases. The morphologic changes associated with coronary angioplasty are similar in patients undergoing elective or emergency angioplasty although medial dissection was not observed in these patients with an evolving myocardial infarction.

Aged↗
PubMed1983

Relation of left ventricular mass to geometry of the proximal coronary arteries in the dog.

Proximal epicardial coronary artery luminal diameters were measured from silicone casts formed in situ in freshly excised hearts under a constant pressure of 100 mm Hg. Twenty-five coronary arteries from 15 normal dogs and 22 coronary arteries in 13 dogs with either chronic pressure or volume overload hypertrophy were studied. Mean left ventricular (LV) body weight ratios were 4.75 +/- 1.01 g/kg in the normal dogs, 8.4 +/- 1.7 g/kg in the pressure-overload dogs, and 6.2 +/- 0.6 g/kg in the volume-overload dogs. The cross-sectional area of the left circumflex (LC) coronary artery was determined at 11 branch sites. The ratio of the area of the branches to the area of the parent vessel was 1.095 +/- 0.105, indicating that the cross-sectional area after a branch point increased. A poor correlation existed between LV mass and coronary artery diameter in both normal and hypertrophy groups for the LC (r = 0.44), the left anterior descending (LAD) (r = 0.63), and the combined LC and LAD (r = 0.52). The mean cross-sectional area of the combined LC and LAD was 0.12 cm2 in the normal group and 0.15 cm2 in the hypertrophy group; this increase was not statistically significant (p = 0.13). When the mean cross-sectional area of the combined vessels was adjusted for heart weight, there was a decrease in the cross-sectional area/100 g of myocardium in the hypertrophy group compared with the control group. These data demonstrate that coronary artery luminal diameter in the dog does not increase commensurately with the increase in mass associated with myocardial hypertrophy.

Animals↗
PubMed1983

Functional improvement of jeopardized myocardium following intracoronary streptokinase infusion in acute myocardial infarction.

The effect of reperfusion on regional left ventricular performance following acute myocardial infarction in man was determined. Intracoronary streptokinase was administered in 24 patients within 6 h of the onset of symptoms. 15 patients (62%) were successfully recanalized during the initial study. Mean percent radial shortening (%RS) in both the jeopardized and compensatory regions were determined using 23 radii from the centroid of diastolic and systolic angiographic silhouettes. Sequential measurements were obtained during repeat cardiac catheterization studies at 24 h in 19 patients and before discharge from the hospital (16 +/- 11 d) in 15 patients. At the time of the predischarge study, each acutely reperfused patient showed improvement in %RS in the jeopardized region (P = 0.01) with 56% returning to the normal range. Despite the uniform improvement in the contractile function of the jeopardized region in each reperfused patient, the global ejection fraction showed no improvement or a decrease at the time of the chronic study in 44%. This was due to a decrease in the compensatory wall motion in the uninvolved segments between the acute and chronic study in each case. Neither the %RS nor the ejection fraction changed significantly at the time of the chronic study in the patients who could not be acutely recanalized. These data indicate (a) significant salvage of jeopardized myocardium associated with recovery of contractile function in patients reperfused during the first 6 h of chest pain following acute myocardial infarction; (b) no improvement in regional or global left ventricular performance in patients who could not be reperfused acutely; and (c) the ejection fraction is strongly influenced by changes in the compensatory wall motion of the uninvolved segments and does not accurately reflect changes in the contractile function of the jeopardized myocardium.

Adult↗
PubMed1983

Adverse effects of nifedipine therapy on hypertrophic obstructive cardiomyopathy.

A 62-year-old man with obstructive hypertrophic cardiomyopathy was given sublingual nifedipine, 10 mg, during invasive hemodynamic monitoring. After 15 minutes, his left ventricular outflow gradient increased from 22 to 80 mm Hg while arterial pressure fell from 152/70 to 122/64 mm Hg. Left ventricular end-diastolic pressure increased from 15 to 22 mm Hg. These adverse hemodynamic responses may have been a result of vasodilation of the peripheral circulation induced by nifedipine. Thus, some patients with hypertrophic obstructive cardiomyopathy may develop serious hemodynamic compromise when treated with nifedipine.

Atrial Fibrillation↗