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Biomedical subjects

R K Myler

Publications and source records attributed to R K Myler.

At least 19 recordsLinked to original sources
PubMed1995

Dyslipoproteinemias in atherosclerosis, thrombosis and restenosis after coronary angioplasty.

Lipids play a vital role in normal metabolic function in mammals. However, dyslipoproteinemias have been implicated in the pathophysiologic process of atherogenesis, thrombogenesis and restenosis after interventional procedures. Lipoproteins provide important chemical linkages among these three complex phenomena. Lipoproteins participate in atherogenesis and play a major role in plaque fissuring, the pathophysiologic common denominator of acute ischemic syndromes. Thrombogenesis is majoraly affected by the action of lipids on platelets, coagulation and fibrinolysis. LDL tend to destabilize platelet membrane activity, macrophages, endothelial and smooth muscle cell function; HDL tend to reverse these abnormalities. The metabolism of arachidonic acid, a metabolite of the essential polyunsaturated lipoprotein, linoleic acid, is integral to platelet and endothelial cell membrane formation, via the cyclooxygenase-prostanoid pathway. Arachidonic acid also is metabolized by the lipoxygenase-leukotreine pathway in neutrophils and monocytes. The relationship of dyslipoproteinemias (increased LDL and Lp(a); decreased HDL) to restenosis after angioplasty has been reported, though there is not universal agreement about causality. Lipid lowering regimens and other pharmacotherapy have had favorable effect slowing the rate of atherogenesis, decreasing the frequency of cardiac events (perhaps by "stabilizing" vulnerable plaques) and causing regression in some atheromata. The salutary effect of lipid-lowering agents upon the incidence of restenosis after angioplasty is problematic. Some investigators have found a statistically significant correlation, while others have not; but studies have not been standardized. In conclusion, the study of lipid metabolism across a wide range of physiochemical activities and the interaction of these phenomena describe complex, genetically determined linkages which instruct (and often humble) investigators in their study of lipids in health and disease.

Angioplasty↗
PubMed1994

Coronary stenting with a new ultra-short balloon expandable device: early and late animal results.

The early and late effects of a new balloon-expandable coronary stent (Boneau II) were studied in 16 adult mongrel dogs. Thirty-three balloon-expandable stents were deployed using standard transfemoral coronary angioplasty technique. Single stents were placed in eight dogs and multiple (two to four) stents were placed in eight dogs. Intravenous heparin (3,000 units) was administered at the beginning of the procedure. Aspirin, dipyridamole, dextran, and warfarin were not administered before or after the procedure. All stent deployments were successful. Angiographic or pathologic examinations were performed within 24 hr of deployment on two of the dogs, at 2 weeks on two of the dogs, at 2 months on three of the dogs, at 6 months on six of the dogs, and at 1 year on three of the dogs. All successfully deployed stents were noted to be widely patent. There was no evidence of side-branch vessel occlusion. There was no evidence of acute or late vessel thrombosis. Histologic examination at 2 months showed a mean intimal thickness of 153 microns. The stainless steel Boneau II coronary stent is relatively short and easily deployed. This balloon-expandable coronary stent was successfully deployed in normal canine arteries without the use of anticoagulation or antiplatelet therapy before or after the procedure. The Boneau II intracoronary stent has a very low thrombogenic potential in dogs.

Angioplasty, Balloon, Coronary↗
PubMed1994

Comparative study of the angiographic morphology of coronary artery lesions treated with PTCA, directional coronary atherectomy, or high-speed rotational ablation.

To evaluate trends in morphology-based intervention selection, series of 110 consecutive procedures of each of three devices, percutaneous transluminal balloon coronary angioplasty (PTCA), directional coronary atherectomy (DCA), or high-speed rotational ablation (HSRA), were reviewed. PTCA was used mainly in discrete, concentric, smooth, ACC/AHA type A and B1 lesions. PTCA was used less frequently on a bend, branching points or in calcified lesions. Using PTCA as a reference, DCA was used more often for the treatment of discrete, proximal, eccentric, and noncalcified lesions, often complicated with thrombus and located on straight segments. HSRA was used more frequently in diffuse, calcified multiple complicated and B2+C type lesions with frequent side branches and bend points. These results suggest that directional atherectomy and rotational ablation may be helpful in expanding the capacity of the operator to approach prognostically unfavorable lesions.

Aged↗
PubMed1994

Adjunctive thrombolytic therapy during angioplasty for ischemic rest angina. Results of the TAUSA Trial. TAUSA Investigators. Thrombolysis and Angioplasty in Unstable Angina trial.

BACKGROUND: Acute closure is increased after angioplasty in unstable angina, and adjunctive intracoronary thrombolytic therapy has been used successfully to increase angiographic success. The role of prophylactic thrombolytic therapy during angioplasty in unstable angina is unknown. METHODS AND RESULTS: Four hundred sixty-nine patients with ischemic rest pain with or without a recent (< 1 month) infarction were randomized in double-blind fashion to intracoronary urokinase or placebo. Randomization was carried out in two sequential phases. In phase I, 257 patients were randomized to 250,000 U of urokinase or placebo given in divided doses at the time of angioplasty. In phase II, 212 patients were randomized to 500,000 U of urokinase or placebo in divided doses. All patients were pretreated with aspirin, and activated clotting times were followed to maintain them at > 300 seconds during angioplasty. Angiographic end points of thrombus after angioplasty were insignificantly decreased by urokinase (30 [13.8%] versus 41 [18.0%] with placebo; P = NS). Acute closure, on the other hand, was increased with urokinase (23 [10.2%] versus 10 [4.3%] with placebo; P < .02). The difference in acute closure between urokinase and placebo was more striking at the higher dose of urokinase (P < .04) than in phase I at the lower urokinase dose (P = NS). Adverse in-hospital clinical end points (ischemia, infarction, or emergency coronary artery bypass surgery) were also increased with urokinase versus placebo (30 [12.9%] versus 15 [6.3%], respectively; P < .02). Angiographic and clinical end points were worse with urokinase in unstable angina without recent infarction than with angioplasty after a recent infarction. CONCLUSIONS: Adjunctive urokinase given prophylactically during angioplasty for ischemic rest angina as administered in this trial is associated with adverse angiographic and clinical events. These detrimental effects may be related to hemorrhagic dissection, lack of intimal sealing, or procoagulant or platelet-activating effects of urokinase.

Angina, Unstable↗
PubMed1994

Triple vessel revascularization: coronary angioplasty versus coronary artery bypass surgery: initial results and five-year follow-up. Comparative costs and loss of working days and wages.

OBJECTIVES: The purpose of this study was to compare early and late outcomes in patients undergoing PTCA or CABG for triple vessel disease. BACKGROUND: Although early results of PTCA/CABG randomized trials have recently become available, at present little data exists on long-term medical and socioeconomic effects of these treatment modalities in patients with triple vessel revascularization. METHODS: During 1986-87, 76 patients undergoing triple vessel PTCA and 85 patients having triple vessel CABG were selected from a consecutive series of patients having multivessel revascularization. Initial results and 5 year outcome, hospital stay and charges and out-of-work time were assessed from prospectively collected data. RESULTS: Clinical and morphological factors were similar in the PTCA and CABG groups. Hospital success and complications were also similar, except for higher mortality in the CABG cohort (0 vs. 3.5%). Five year follow-up showed no differences in survival, nonfatal infarction and angina-free status; however, there was a difference in need for repeat revascularization (PTCA 55.4% vs. CABG 6.3%, p less than 0.001). Repeat PTCA accounted for 49% of the revascularization in the PTCA cohort. Crossovers were similar (PTCA[CABG 6.8%; CABG[PTCA 6.3%, pNS). Predictors of late death in the entire population were female gender (p less than 0.0001), diabetes (p<0.05) and depressed LVEF (p less than 0.05). The choice of revascularization procedure (PTCA vs. CABG) was not an independent predictor of late death or MI. Analysis of initial hospital charges showed a 2:1 advantage in favor of PTCA but this advantage was lost in late followup due to the need for repeat revascularization in the PTCA group. However, the PTCA cohort lost fewer working days than CABG patients (3017 vs 5874 days) and therefore, lost less wages ($7,022 vs. $14,685). CONCLUSIONS: The study shows that for selected triple vessel disease patients, PTCA and CABG results are comparable after 5 years, though repeat revascularization (mainly due to restenosis) was necessary in the PTCA group to maintain these favorable results. After 5 years, hospital charges are similar in the 2 groups, though out-of-work time and lost wages were 2:1 in favor of PTCA.

Absenteeism↗
PubMed1993

Digital supine bicycle stress echocardiography: a new technique for evaluating coronary artery disease.

OBJECTIVES: The objective of this study was to determine the accuracy of digital supine bicycle stress echocardiography, a new technique for evaluating coronary artery disease during peak exercise. BACKGROUND: Prior stress echocardiographic techniques have not utilized peak exercise imaging to determine the extent and location of coronary artery disease. METHODS: Two-hundred twenty-two patients were studied: 180 underwent both supine bicycle stress echocardiography and coronary arteriography; 42 had a < 5% likelihood of disease. Forty-three patients had normal coronary arteries, 55 had single-vessel, 42 had double-vessel and 40 had triple-vessel coronary artery disease. RESULTS: Supine bicycle stress echocardiography was 93% sensitive, 86% specific and 92% accurate for identifying patients with coronary artery disease irrespective of prior myocardial infarction or achievement of > or = 85% maximal predicted heart rate. The "normalcy" rate in the low probability group was 100%. Supine bicycle stress echocardiography was 87% sensitive, 89% specific and 88% accurate for specific vessel identification. The sensitivity was greatest for the left anterior descending compared with the right coronary artery and the left circumflex coronary artery (95% vs. 81% vs. 78%, p < 0.01) and for vessels in patients with double- and triple-vessel compared with single-vessel disease (90% vs. 89% vs. 78%, p < 0.05). The procedure was significantly more sensitive for detection of vessels with 90% to 100% compared with 50% to 70% diameter stenosis (91% vs. 81%, p < 0.05) and was 88% correct in the prediction of multivessel disease. CONCLUSIONS: Supine bicycle stress echocardiography is a highly accurate tool for evaluating coronary artery disease, identifying both the patient with coronary artery disease and the location and extent of disease.

Adult↗
PubMed1993

Usefulness of supine bicycle stress echocardiography for detection of restenosis after percutaneous transluminal coronary angioplasty.

The role of supine bicycle stress echocardiography (SBSE) for detecting restenosis after percutaneous transluminal coronary angioplasty (PTCA) was evaluated in 80 patients: 41 (51%) with single and 39 (49%) with multivessel PTCA (total 129 dilated vessels). Total revascularization was performed in 54 (68%) and partial revascularization in 26 (32%) patients. Restenosis was angiographically demonstrated in 60 patients (75%) and in 72 vessels (56%) 6.1 +/- 2.9 months after PTCA. The results for detecting restenosis were: (1) SBSE versus exercise electrocardiographic sensitivity, 87 versus 55% (p < 0.001); (2) specificity, 95 versus 79%; and (3) accuracy, 89 versus 61% (p < 0.001). SBSE was 83% sensitive, 95% specific and 88% accurate for restenosis detection in specific vessels with comparable results for single versus multivessel PTCA and total versus partial revascularization. Sensitivity, specificity and accuracy were: 91, 93 and 91% for the left anterior descending coronary artery; 77, 94 and 85% for the right coronary artery; and 76, 96 and 88% for the left circumflex coronary artery. Ninety-four percent of the nondilated diseased vessels were correctly identified. It is concluded that SBSE is an excellent tool for identifying restenosis after PTCA.

Aged↗
PubMed1993

Coronary rotational ablation: initial experience in 302 procedures.

OBJECTIVES: The aim of this study was to assess the utility of percutaneous transluminal coronary rotational ablation in the treatment of coronary artery disease. BACKGROUND: Although numerous advances have been made in the treatment of coronary artery disease, there are lesions with complex morphology that are not amenable to current intravascular therapy. METHODS: A consecutive series of 242 patients having 302 coronary rotational ablation procedures was analyzed. One hundred nineteen (49%) of the patients had previously undergone attempted coronary angioplasty, which was unsuccessful in 31 patients (13%). The left ventricular ejection fraction was normal in 196 patients (81%). The ablation procedure was attempted in 308 vessels and 346 lesions. Of the 346 lesions treated, 26 (7.5%) were classified as American College of Cardiology/American Heart Association type A, and 320 (92.5%) as either type B or type C. RESULTS: Procedural success was achieved in 284 (94%) of the 302 procedures and 330 (95.4%) of the 346 lesions in which ablation was attempted. Five procedures (1.7%) were unsuccessful, but no cardiac event occurred during the hospital stay. A major cardiac event occurred in 13 cases (4.3%); 9 (3%) of these complications were due to the ablation procedure. Six patients sustained a Q wave myocardial infarction alone, two had a Q wave infarction and required emergency surgery and one needed emergency surgery but did not have a Q wave infarction. No procedural deaths were attributed to the ablation procedure. Follow-up has been obtained in 182 of the 242 patients at a mean interval of 9 +/- 5 months. Of the 182 patients, 174 (95.6%) were alive and free of myocardial infarction. Angiographic follow-up is available thus far in 87 patients. By combining angiographic and clinical outcome, an overall estimated restenosis rate of 37.4% (68 of 182) was calculated. CONCLUSIONS: These data suggest that coronary rotational ablation can be performed on lesions with a variety of morphologic features with high initial success rates. The overall rate of restenosis is similar to that of balloon angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1993

The evolution of a clinical database to evaluate the treatment of coronary artery disease.

BACKGROUND: The field of invasive cardiology has evolved rapidly since the initial use of catheters for treatment of coronary artery disease in the late 1970's. The pace of this change coupled with the complexity of the clinical setting and proliferation of devices and drugs used for therapy have made it extremely difficult to construct and maintain a viable clinical database. METHODS: Using a standard hardware and software system with the direct clinical input from a multidisciplinary team of physicians, nurses and biostatisticians, a clinical database was developed that is capable of tracking complex in-hospital and longterm follow-up data in patients undergoing treatment of coronary artery disease. RESULTS: The database has provided the basis for in-depth analysis of angioplasty results in patients with vessels and lesions of varying morphology, showing greater than 90% success in most complex lesion morphology using contemporary balloon technology and/or new devices. Longterm analysis (14 years) of patients after angioplasty has demonstrated that 76% survived without major cardiac events. Other analyses of various clinical and morphologic subsets have shown favorable results with angioplasty. The databases for angioplasty and coronary bypass surgery have been combined, showing comparable survival and freedom from cardiac events in multivessel disease patients treated with these procedures. CONCLUSIONS: The development of a dynamic and clinically relevant database that has evolved has contributed valuable information to the understanding and effective management of patients with coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1993

Late outcome of multivessel coronary artery disease after angioplasty or bypass surgery.

Background. Results from randomized trials to determine optimal treatment for patients with multivessel coronary disease are not yet available. Thus, the early and late outcomes of 191 PTCA and 221 CABG patients done in 1985-86 were evaluated. Methods and Results. CABG patients selected had more coronary risk factors and more severe coronary artery disease compared to PTCA patients. Comparison of the initial outcome showed that clinical success without major cardiovascular events was similar (93.7% for PTCA vs. 90.0% for CABG; p=n.s.). Five year followup was obtained in 99.0% of PTCA patients and 94.4% of CABG patients. In the PTCA group, 89.8% were alive, 4.8% had sustained an MI, and repeat revascularization was required in 46.8%. In the CABG group, 87.1% were alive, 3.2% had had a MI, and 3.5% required repeat revascularization. Statistical comparison demonstrated no difference between the groups in survival or late cardiac events, but rate of repeat revascularization was significantly higher for PTCA patients (p less than 0.0001). Incompleteness of revascularization (p<0.01) was independently associated with an increased need for repeat revascularization in the PTCA group. In the CABG group, depressed left ventricular function (p less than 0.001) and female sex (p<0.01) were associated with lower survival rates. An analysis of cost per patient showed that the strategies were comparable. Conclusions. PTCA and CABG in multivessel disease patients have similar early results and comparable rates of survival and late cardiac events. Significantly more repeat revascularization is required in PTCA patients to maintain these results.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Lesion morphology and coronary angioplasty: current experience and analysis.

From July 1, 1990 to February 28, 1991, 533 consecutive patients with 764 target vessels and 1,000 lesions underwent coronary angioplasty. Procedural success was achieved in 92.3%, untoward (major cardiac) events occurred in 3% (0.8% myocardial infarction, 1.3% emergency coronary bypass grafting and 0.9% both; there were no deaths). An unsuccessful uncomplicated outcome occurred in 4.7%. Lesion analysis using a modified American College of Cardiology/American Heart Association classification system showed that 8% were type A, 47.5% were type B and 44.5% were type C (36% of type B and 11% of type C were occlusions). Angioplasty success was achieved in 99% of type A, 92% of type B and 90% of type C lesions (A vs. B, p less than 0.05; B vs. C, p = NS; A vs. C, p less than 0.01). Untoward events occurred in 1.2% of type A, 1.9% of type B and 2% of type C lesions (p = NS). An unsuccessful uncomplicated outcome occurred in 0% of type A, 6% of type B and 7% of type C lesions (A vs. B, p less than 0.05; B vs. C, p = NS; A vs. C, p less than 0.05). Among the unsuccessful uncomplicated outcome group, occlusion occurred in 49%: 38% of type B and 59% of type C lesions. With B1 and B2 subtypes, success was obtained in 95% and 89.5% and untoward events occurred in 1.5% and 2.3% and an unsuccessful uncomplicated outcome in 3.7% and 8%, respectively. C1 and C2 subtyping showed success in 91% and 86%, untoward events in 1.3% and 6% and an unsuccessful uncomplicated outcome in 7.5% and 8.5%, respectively. Among the 764 vessels, success was obtained in 89.5% and untoward events occurred in 2.5% and an unsuccessful uncomplicated outcome in 8%. Assessment of lesion-vessel combinations showed a less favorable outcome with type C lesions and combinations of A-B, B-C and multiple (more than three lesions) type B and C vessels. Statistical analysis of morphologic factors associated with angioplasty success included absence of (old) occlusion (p less than 0.0001) and unprotected bifurcation lesion (p less than 0.001), decreasing lesion length (p less than 0.003) and no thrombus (p less than 0.03). The only significant factor associated with untoward events was the presence of thrombus (p less than 0.003). Predictors of an unsuccessful uncomplicated outcome included old occlusion (p less than 0.0001) and increasing lesion length (greater than 20 mm) (p less than 0.001), unprotected bifurcation lesion (p less than 0.05) and thrombus (p less than 0.03).

Angioplasty, Balloon, Coronary↗
PubMed1991

Causes and correlates of death after unsupported coronary angioplasty: implications for use of angioplasty and advanced support techniques in high-risk settings.

To better understand the factors predisposing a patient to death after elective percutaneous transluminal coronary angioplasty (PTCA) and to gain insight into indications for high-risk PTCA both with and without adjunctive use of support devices, the outcomes of 8,052 consecutive procedures were reviewed. Death occurred after 32 procedures (0.4%) and was directly related to coronary artery closure in 26 (81%) of these cases. Left ventricular failure due to vessel closure at the dilated site, the most common cause of death, was independently correlated with female sex (p less than 0.001), "jeopardy score" (p less than 0.001) and PTCA of a proximal right coronary artery site (p = 0.002), but not with left ventricular ejection fraction or presence of multivessel disease. Right ventricular failure after closure of the proximal right coronary artery, and left main coronary dissection accounted for the majority of the remaining deaths. Systolic blood pressure immediately after coronary artery closure was also closely correlated with jeopardy score, and cardiogenic shock was frequent in women with scores greater than or equal to 3.5 and in men with scores greater than or equal to 5.0. These data highlight the superiority of the jeopardy score versus ejection fraction in the determination of risk, stress the importance of gender in determining outcome and point to the need for better means of right ventricular protection from severe ischemia. Therefore, an initial framework for rational use of PTCA and support devices in the high-risk setting is established.

Aged↗