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Biomedical subjects

R S Stack

Publications and source records attributed to R S Stack.

At least 19 recordsLinked to original sources
PubMed1992

Intracoronary ultrasound predictors of adverse outcomes after coronary artery interventions.

OBJECTIVES: The purpose of this study was to determine the association between qualitative and quantitative lesion characteristics as assessed by intracoronary ultrasound imaging and adverse outcomes after coronary artery interventions. BACKGROUND: Restenosis and other adverse outcomes after coronary artery interventions may be difficult to predict from clinical or angiographic data. Intracoronary ultrasound imaging provides additional data that could prove useful. METHODS: Immediately after successful coronary artery interventions (angiographic residual stenosis < or = 50%), 69 patients underwent intracoronary ultrasound imaging. Images were assessed qualitatively for plaque composition and topography and for dissection. Quantitative data included measurement of minimal lumen diameter, lumen area, plaque area and percent area stenosis at the treatment and adjacent reference sites. Adverse outcome was defined as death, coronary bypass surgery, myocardial infarction or angiographic restenosis. RESULTS: Of the 69 patients, 1 died, 3 had bypass surgery and 1 had a myocardial infarction before planned 6-month repeat catheterization. Two patients were lost to follow-up study. Of the remaining 62 patients, 56 (90%) agreed to follow-up catheterization and 25 (45%) of the 56 had restenosis. Thus, 30 patients had an adverse outcome and 37 had no adverse event. The incidence of dissection detected by ultrasound imaging after an intervention was significantly greater in patients with than in those without a subsequent adverse event (63% vs. 35%, p < 0.05). The severity of dissection also appeared to be related to outcome (p < 0.05). Other qualitative and quantitative variables were not significantly different between the two patient groups. CONCLUSIONS: Dissection, as assessed by intracoronary ultrasound imaging after a coronary artery intervention, can identify patients at increased risk of subsequent adverse events. Additional studies are warranted to explore whether such imaging may allow modification of interventional procedures to improve outcome.

Angioplasty, Balloon, Coronary↗
PubMed1992

Outcome of patients sustaining acute ischemic mitral regurgitation during myocardial infarction.

OBJECTIVE: To describe outcomes of patients sustaining an acute myocardial infarction complicated by mitral regurgitation managed with contemporary reperfusion therapies. DESIGN: Inception cohort case study. Long-term follow-up was obtained in 99% of all patients. SETTING: University referral center. PATIENTS: A series of 1,480 consecutive patients presenting between April 1986 and March 1989 who had emergency cardiac catheterization within 6 hours of infarction. Fifty patients were found to have moderately severe or severe mitral regurgitation. OUTCOME MEASURES: Mortality; follow-up cardiac catheterization in patients with regurgitation. RESULTS: Acute ischemic moderately severe to severe (3+ or 4+) mitral regurgitation was associated with a mortality of 24% at 30 days (95% CI, 12% to 36%), 42% at 6 months (CI, 28% to 56%), and 52% at 1 year (CI, 38% to 66%); multivariable analysis identified 3+ or 4+ mitral regurgitation as a possible independent predictor of mortality (P = 0.06). Patients with mitral regurgitation tended to be female, older, and to have cerebrovascular disease, diabetes, and preexisting symptomatic coronary artery disease. A physical examination did not identify 50% of patients with moderately severe to severe regurgitation. Acute reperfusion with thrombolysis or angioplasty did not reliably reverse valvular incompetence. In this observational study, the greatest in-hospital and 1-year mortalities were seen in patients reperfused with emergency balloon angioplasty, whereas patients managed medically or with coronary bypass surgery had lower mortalities. CONCLUSIONS: Moderately severe to severe (3+ or 4+) mitral regurgitation complicating acute myocardial infarction portends a grave prognosis. Acute reperfusion does not reduce mortality to levels experienced by patients with lesser degrees of mitral regurgitation nor does it reliably restore valvular competence.

Acute Disease↗
PubMed1992

Outcome after prolonged balloon inflations of greater than 20 minutes for initially unsuccessful percutaneous transluminal coronary angioplasty.

Prolonged balloon inflation with or without autoperfusion techniques is a common initial approach to major dissection or abrupt occlusion after percutaneous transluminal coronary angioplasty (PTCA). To assess such a strategy in the setting of unsuccessful angioplasty, 40 patients who underwent prolonged balloon inflations of greater than 20 minutes between January and July of 1991 after initially unsuccessful angioplasty were studied. These patients (median age 59 years) underwent PTCA for progressive or unstable angina (16[40%]), symptomatic or asymptomatic residual stenosis after myocardial infarction (10[25%]), acute myocardial infarction (3[8%]), stable angina (3[8%]), reinfarction (2[5%]), and other indications (6[15%]). The significant stenoses were primarily in the proximal and midportions of the right coronary (53%), left anterior descending (30%) and left circumflex (17%) coronary arteries. Before prolonged balloon inflation, the longest single inflation was 11 +/- 6 minutes and the total time of all inflations was 17 +/- 8 minutes (mean +/- standard deviation). Stenosis was reduced from 91 +/- 9 to 68 +/- 16% before prolonged inflation. After prolonged balloon inflation of 30 +/- 9 minutes, the residual stenosis was 47 +/- 21% (p = 0.0001 vs value before prolonged inflation). Furthermore, improvements in the appearance of filling defects or dissections, or both, occurred in 19 patients (48%). Procedural success was obtained in 32 of 40 patients (80%). Coronary bypass grafting was performed in 8 patients (20%): 4 after unsuccessful PTCA (3 emergently) and 4 electively after initially successful PTCA. Although 5 patients had creatine kinase-MB elevations greater than 20 IU/liter after the procedure, only 1 sustained a Q-wave myocardial infarction. There were no deaths in the hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Early and late outcome following deployment of a new flexible tantalum intracoronary stent in dogs.

A new radiopaque, highly flexible balloon-expandable tantalum stent was tested. Thirty-six of 40 stents were successfully deployed percutaneously in the coronary arteries of 31 dogs. The dogs were given aspirin before, intravenous heparin during, and aspirin alone after the procedure. One dog died at 24 hours because of coronary occlusion following traumatic implantation. Four dogs were put to death early, revealing re-endothelialization by 9 days. Eleven dogs were put to death from 2 weeks to 9 months during long-term follow-up, showing all vessels widely patent with the stent uniformly embedded within a stable neointimal layer. Follow-up arteriography showed patency in all remaining stents up to 1 year, with no perforation or aneurysm formation. Four stents were placed into canine peripheral arteries and were removed percutaneously after deployment. Pathology revealed no significant trauma to involved vessels. This tantalum stent exhibits feasibility of percutaneous deployment, early neointimal formation, low thrombogenicity on long-term aspirin therapy alone, and patency up to 1 year in this canine model.

Animals↗
PubMed1992

Mechanisms of balloon angioplasty and directional coronary atherectomy as assessed by intracoronary ultrasound.

OBJECTIVE: This study was designed to use intracoronary ultrasound imaging to elucidate the physical effects of balloon angioplasty and directional coronary atherectomy in vivo in humans. BACKGROUND: The proposed mechanisms of coronary artery interventions such as balloon angioplasty and directional atherectomy are based on animal studies or pathologic findings and these data may not be applicable to living patients. Intracoronary ultrasound findings correlate highly with pathologic results and may allow in vivo assessment of the mechanisms of such interventions in humans. METHODS: Intracoronary ultrasound imaging was performed in 45 patients after a successful coronary intervention (balloon angioplasty in 30, directional coronary atherectomy in 15). Ultrasound images obtained at the treatment site and at an adjacent angiographically normal references site were analyzed quantitatively for minimal lumen diameter, cross-sectional lumen area, are enclosed by the internal elastic lamina, plaque area (internal elastic lamina area--lumen area) and percent area stenosis (plaque area/internal elastic lamina area). Qualitative analysis included assessment of presence of dissection, plaque composition and plaque topography. RESULTS: The results of the two procedures were similar with respect to minimal lumen diameter (angioplasty 2.6 +/- 0.5 vs. atherectomy 2.6 +/- 0.3 mm, p = NS), lumen area (0.07 +/- 0.03 vs. 0.07 +/- 0.02 cm2, p = NS) and percent area stenosis (59 +/- 14% vs. 51 +/- 21%, p = NS). However, after angioplasty, the internal elastic lamina area was significantly larger at the treated site than at the reference site (delta = +0.03 +/- 0.04 cm2, p = 0.01). There was no significant difference between the two sites after atherectomy (delta = -0.01 +/- 0.05 cm2, p = NS). In addition, dissection was seen significantly more often after balloon angioplasty than after atherectomy (50% vs. 7%, p less than 0.01). The results were similar when stratified for plaque composition and morphology. These data were confirmed in six additional patients who underwent ultrasound imaging before and after the intervention. CONCLUSIONS: Thus, the improvement in lumen dimensions after coronary balloon angioplasty is a result of both vessel stretch, demonstrated by a larger internal elastic lamina area at the treated site, and dissection. Both vessel stretch and dissection are uncommon after atherectomy, a finding consistent with plaque removal as the major mechanism for improved lumen area after this procedure.

Adult↗
PubMed1992

Real-time assessment of experimental arterial angioplasty with transvenous intravascular ultrasound.

Optimal evaluation of experimental angioplasty procedures would allow real-time simultaneous assessment during the procedure without direct manipulation of treated arterial segments. To assess the feasibility and utility of transvenous real-time intravascular ultrasound imaging during experimental angioplasty, 11 consecutive atherosclerotic iliac artery segments in rabbits were imaged before, during and after thermal or conventional perfusion balloon angioplasty. A 20-MHz intravascular ultrasound catheter was positioned in the adjacent vein, and images were correlated with data from quantitative angiography and histologic studies. Images suitable for analysis were obtained at all 11 sites. Arterial distension and recoil were observed during balloon inflation and deflation. Measurements of lumen diameter and cross-sectional area by intravascular ultrasound and angiography were closely correlated (r2 = 0.90, SEE = 0.2 mm, and r2 = 0.90, SEE = 0.8 mm2, respectively). Intimal dissections were identified in six segments by intravascular ultrasound and all were concordant with histologic findings. Thus, real-time transvenous ultrasound avoids manipulation of the treated artery, and is a feasible modality for dynamic quantitative and qualitative assessment of arterial interventions.

Angiography, Digital Subtraction↗
PubMed1992

Gene transfer into coronary arteries of intact animals with a percutaneous balloon catheter.

Genetic manipulation of the vasculature may offer insights into the pathogenesis of coronary artery disease and may lead to gene therapy for disorders such as restenosis after percutaneous coronary angioplasty. The goal of this study was to develop a percutaneous method for gene transfer into coronary arteries of intact animals. Liposomes were used to facilitate transfection in coronary arteries with a plasmid containing the cDNA encoding luciferase. This reporter was chosen since it is not expressed in mammalian cells, and it can be quantified using a sensitive assay (light production). Mongrel dogs were catheterized, and DNA was delivered to coronary arteries via a porous perfusion balloon system. Luciferase expression was measured 3-5 days after the procedure, when the dogs were killed. Luciferase activity in control arteries (n = 12) was no higher than average background activity. Eight of 12 transfected arteries exhibited gene expression, averaging 4.3 +/- 2.1 pg luciferase (p less than 0.01, transfected versus control arteries). In addition, the ability to transfect DNA into femoral arteries without a transfection vehicle was tested. Five dogs were subjected to surgical transfection attempts in their femoral arteries with either DNA alone or DNA plus liposomes. Luciferase was expressed in all 10 femoral arteries; those treated with DNA alone expressed 35.6 +/- 8 pg luciferase, and those treated with DNA plus liposomes expressed 42.3 +/- 14 pg luciferase (p = 0.70). These results demonstrate the use of a percutaneous catheter to achieve gene transfer and expression in coronary arteries of intact dogs and suggest that the efficiency of intra-arterial gene transfer may be similar whether or not a transfection vehicle is used.

Animals↗
PubMed1991

Thrombolytic therapy in patients requiring cardiopulmonary resuscitation.

Cardiopulmonary resuscitation (CPR) is often considered a contraindication to thrombolytic therapy for acute myocardial infarction. Of 708 patients involved in the first 3 Thrombolysis and Angioplasty in Myocardial Infarction trials of lytic therapy for acute infarction, 59 patients required less than 10 minutes of CPR before receiving lytic therapy (CPR greater than 10 minutes was an exclusion of the trials) or required CPR within 6 hours of treatment. The patients receiving CPR were similar to the remainder of the group with respect to baseline demographics. The indication for CPR was usually ventricular fibrillation (73%) or ventricular tachycardia (24%). The median duration of CPR was 1 minute, with twenty-fifth and seventy-fifth percentiles of 1 and 5 minutes, respectively. The median number of cardioversions/defibrillations performed was 2 (twenty-fifth and seventy-fifth percentiles of 1 and 3 minutes, respectively). Patients receiving CPR were more likely to have anterior infarctions (66 vs 39%), the left anterior descending artery as the infarct-related artery (63 vs 38%) and lower ejection fractions on the initial ventriculogram (46 +/- 11 vs 52 +/- 12%) than those not receiving CPR. In-hospital mortality was 12 vs 6% with most deaths due to pump failure (57%) or arrhythmia (29%) in the CPR group and pump failure (38%) or reinfarction (25%) in the non-CPR group. At 7 day follow-up the CPR group had a significant increase in ejection fraction (+5 +/- 9%) compared with no change in non-CPR group. There were no bleeding complications directly attributed to CPR.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

The use of intraaortic balloon pumping as an adjunct to reperfusion therapy in acute myocardial infarction. The Thrombolysis and Angioplasty in Myocardial Infarction (TAMI) Study Group.

To assess the risk and possible benefits of use of the percutaneous IABP in patients given thrombolytic therapy as treatment for acute myocardial infarction, we prospectively evaluated 810 consecutive patients entered into the TAMI trials. During hospitalization the 85 patients treated with the IABP had more cardiac risk factors, were slightly older (58 vs 56 years), and more often had anterior infarction (62% vs 38%). At acute cardiac catheterization, patients treated with the IABP also had more multivessel coronary disease (67% vs 43%), more frequent TIMI grade 0 or 1 flow (44% vs 28%), lower global ejection fraction (40% vs 52%), and worse regional infarct (-3.2 vs -2.5 SD/chord) and noninfarct (-0.67 vs +0.36 SD/chord) zone function. Although mortality rates (32% vs 4%) and in-hospital complications were greater in patients treated with the IABP, a greater improvement in global (delta ejection fraction: +1.9% vs +0.7%) and noninfarct zone (delta SD/chord: +0.11 vs -0.09) left ventricular function was observed in patients treated with the IABP at 1-week follow-up angiography. In addition, no reinfarction or reocclusion of the infarct-related artery occurred while patients were being treated with the IABP. These results suggest that the IABP may have a specific role after thrombolytic therapy in treating patients at high risk for reocclusion or at high risk for hemodynamic deterioration because of large infarction or critical stenoses in coronary vessels supplying the noninfarct zone.

Angioplasty, Balloon, Coronary↗
PubMed1991

Restenosis after coronary angioplasty: an overview.

Despite substantial basic and clinical efforts to address the problem of restenosis after percutaneous coronary intervention, effective preventive therapies have not yet been developed. Nevertheless, the accumulated information has provided much insight into the process of restenosis in addition to allowing standards to be developed for adequate clinical trials. The pathophysiology of restenosis increasingly appears to be distinct from that of primary atherosclerosis. Restenosis involves elastic recoil, incorporation of thrombus into the lesion and fibrocellular proliferation in varying degrees in different patients. Lack of an animal model that satisfactorily mimics restenosis is a major impediment to further understanding of the process. Clinical studies are hampered by difficulties in finding a single unifying definition of restenosis and by variable methods of reporting follow-up. Reporting of clinical outcomes of all patients in angiographic substudies would allow a more satisfactory interpretation of the results of clinical trials. Current noninvasive test results are not accurate enough to substitute for angiographic and clinical outcome data in intervention trials. In the majority of observational studies, only diabetes and unstable angina have emerged as consistently associated with restenosis; whereas most of the standard risk factors for atherosclerosis have a less consistent relation. Disappointingly, the new atherectomy and laser technologies have not affected restenosis rates. The one possible exception is coronary stenting, as a result of the larger luminal diameter achieved by the placement of the stent. In conclusion, although substantial continued effort is necessary to explore the basic aspects of cellular proliferation and mechanical alteration of atherosclerotic vessels, attention to the principles of clinical trials and observation are required to detect the impact of risk factors and interventions on the multifactorial problem of restenosis. Adequate sample sizes, collection of clinical and angiographic outcomes and factorial study designs hold promise for unraveling this important limitation of percutaneous intervention.

Angioplasty, Balloon, Coronary↗
PubMed1991

Myocardial infarction with minimal coronary atherosclerosis in the era of thrombolytic reperfusion. The Thrombolysis and Angioplasty in Myocardial Infarction (TAMI) Study Group.

The incidence of minimal residual atherosclerotic coronary obstruction after successful intravenous thrombolytic therapy was evaluated in 799 patients with acute myocardial infarction. Minimal residual coronary obstruction (less than or equal to 50%) was observed on selective coronary angiography performed 90 min after initiation of thrombolytic therapy in 43 patients (5.5%). In 42 other patients (5.4%), a greater than 50% but less than 100% residual stenosis noted at 90 min demonstrated further resolution of obstruction to less than 50% at an angiographic follow-up study 7 to 10 days later. Patients with minimal residual coronary obstruction were significantly younger (52 +/- 10.7 versus 56.7 +/- 10 years; p = 0.002) and had less multivessel coronary disease (p less than 0.001), better initial left ventricular ejection fraction (54 +/- 12% versus 50.2 +/- 11.4%; p = 0.006) and a lower in-hospital mortality rate (1% versus 7%; p = 0.04) than did patients who had a significant (greater than 50%) residual coronary obstruction after intravenous thrombolysis. Long-term follow-up study of patients with a minimal coronary lesion (average 1.5 +/- 0.6 years) and those with significant residual stenosis (average 1.6 +/- 0.7 years) demonstrated that the incidence of death (2.4% in patients with minimal stenosis versus 3.5% in those with significant stenosis) and recurrent myocardial infarction (5% each) were similar in both groups. New strategies are needed to prevent coronary rethrombosis in patients with minimal atherosclerosis after thrombolytic therapy for acute myocardial infarction.

Coronary Angiography↗
PubMed1991

Mechanisms of angioplasty in hemodialysis fistula stenoses evaluated by intravascular ultrasound.

Quantification of luminal dimensions and the mechanisms by which angioplasty (PTA) corrects non-atheroma venous fistula stenoses have been poorly studied. In 38 consecutive percutaneous balloon angioplasties of hemodialysis fistula stenoses, catheter-based, mechanically-rotated intravascular ultrasound (IVUS) images were obtained along with cineangiography. Images from 24 brachial vein, 11 central vein, 2 graft anastomoses, and 1 brachial artery were quantitatively and qualitatively evaluated. Semiautomated quantitative angiographic stenosis was 64 +/- 13% pre-PTA and reduced to 36 +/- 19% post-PTA (P less than 0.001). Post-PTA IVUS minimal lesion diameter and cross sectional area were 5.7 +/- 1.5 mm and 2.9 +/- 1.5 mm2, respectively. With IVUS, mechanisms observed were: vessel dissection in 16 (42%), arterial stretch (defined as vessel diameter: balloon diameter ratio = 0.75 to 1.0) in 19 (50%), and elastic recoil (defined as vessel diameter: balloon diameter ratio less than 0.75) in 19 (50%). Compared to angiography, morphologic information provided by IVUS were plaque composition (hard 11%, soft 89%), plaque topography (eccentric 94%, concentric 6%), thrombus (IVUS: N = 6 vs. angio: N = 1), dissection (IVUS: N = 16 vs. angio: N = 1). Thus, IVUS can evaluate lesion morphology and define luminal dimensions after angioplasty. Mechanisms of successful angioplasty of hemodialysis fistula stenosis occur primarily by vessel stretching and dissection, and significant post-PTA narrowing is due to elastic recoil.

Adult↗
PubMed1991

Racial differences in responses to thrombolytic therapy with recombinant tissue-type plasminogen activator. Increased fibrin(ogen)olysis in blacks. The Thrombolysis and Angioplasty in Myocardial Infarction Study Group.

To determine whether there are differences in responses to thrombolytic therapy in certain populations, the data for the Thrombolysis and Angioplasty in Myocardial Infarction (phase 1) study were analyzed for black and white patients. Baseline variables including risk factors and extent of coronary artery disease were similar in the 352 white and 24 black patients. The time from onset of chest pain to recombinant tissue-type plasminogen activator (rt-PA) therapy and rt-PA dosing regimens were the same in the two groups. The patency rate of the infarct-related artery at 90 minutes was 91% for blacks and was 72% for whites (p = 0.051). Blacks displayed significantly lower nadir fibrinogen levels (0.57 +/- 0.62 versus 1.3 +/- 0.76 g/l, p less than 0.0001), greater delta fibrinogen (baseline-nadir) (2.7 +/- 1.1 versus 1.7 +/- 1.1 g/l, p less than 0.0001), and increased peak levels of fibrin(ogen) degradation products (837 +/- 865 versus 245 +/- 475 micrograms/ml, p less than 0.0001). rt-PA antigen levels tended to be higher in blacks than in whites (2.8 +/- 2.2 versus 2.2 +/- 3.2 micrograms/ml [p = 0.10] at the peak and 1.6 +/- 1.3 versus 0.99 +/- 1.4 micrograms/ml [p = 0.06] at the end of the maintenance infusion). Major clinical outcomes including survival until time of hospital discharge (92% black versus 93% white, p = 0.68) were not significantly different. However, despite undergoing fewer angioplasty procedures (25% versus 46.3%, p = 0.047), blacks received more transfusions (58.8% versus 19.5% were administered greater than or equal to 2 units packed erythrocytes, p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Black People↗
PubMed1991

Evaluation of combination thrombolytic therapy and timing of cardiac catheterization in acute myocardial infarction. Results of thrombolysis and angioplasty in myocardial infarction--phase 5 randomized trial. TAMI Study Group.

Recent trials of myocardial reperfusion using single-agent thrombolytic therapy and sequential cardiac catheterization have supported a conservative approach to the patient with acute myocardial infarction. To evaluate combination thrombolytic therapy and the role of a previously untested strategy for the aggressive use of cardiac catheterization, we performed a multicenter clinical trial with a 3 x 2 factorial design in which 575 patients were randomly allocated to one of three drug regimens--tissue-type plasminogen activator (t-PA) (n = 191), urokinase (n = 190), or both (n = 194) - and one of two catheterization strategies--immediate catheterization with angioplasty for failed thrombolysis (n = 287) or deferred predischarge catheterization on days 5-10 (n = 288). Patients with contraindications to thrombolytic therapy, cardiogenic shock, or age of more than 75 years were excluded. Global left ventricular ejection fraction was well preserved and almost identical at predischarge catheterization (54%), regardless of the catheterization or thrombolytic strategy used (p = 0.98). Combination thrombolytic therapy was associated with a less complicated clinical course, most clearly documented by a lower rate of reocclusion (2%) compared with urokinase (7%) and t-PA (12%) (p = 0.04) and a lower rate of recurrent ischemia (25%) compared with urokinase (35%) and t-PA (31%). When a composite clinical end point (e.g., death, stroke, reinfarction, reocclusion, heart failure, or recurrent ischemia) was examined, combination thrombolytic therapy was associated with greater freedom from any adverse event (68%) compared with either single agent (urokinase, 55%; t-PA, 60%) (p = 0.04) and with a less complicated clinical course when the composite clinical end points were ranked according to clinical severity (p = 0.024). Early patency rates were greater with combination therapy, although predischarge patency rates after considering interventions to maintain patency were similar among drug regimens. No difference in bleeding complication rates was observed with any thrombolytic regimen. The aggressive catheterization strategy led to an overall early patency rate of 96% and a predischarge patency rate of 94% compared with a 90% predischarge patency in the conservative strategy (p = 0.065). The aggressive strategy improved regional wall motion in the infarct region (-2.16 SDs/chord) compared with deferred catheterization (-2.49 SDs/chord) (p = 0.004). More patients treated with the aggressive strategy were free from adverse outcomes (67% versus 55% in the conservative strategy, p = 0.004), and the clinical course was less complicated when the adverse outcomes were ranked according to severity (p = 0.016). No significant increase in use of blood products resulted from the aggressive strategy.(ABSTRACT TRUNCATED AT 400 WORDS)

Angioplasty, Balloon, Coronary↗