Amiprilose hydrochloride inhibits porcine aortic smooth muscle cell proliferation in vitro.

The effect of amiprilose hydrochloride, a synthetic monosaccharide, on smooth muscle cell proliferation was studied in vitro. Using porcine aortic smooth muscle cell cultures, amiprilose significantly inhibited cell proliferation in a dose-dependent fashion at concentrations of 0.5-1.0 mg/ml. This antiproliferative effect was reversible upon removing amiprilose by cell washing and adding fresh media. Pretreating cells with amiprilose before serum stimulation did not affect subsequent growth. Inhibition of proliferation occurred when amiprilose was added up to 48 hours after serum stimulation. As such, amiprilose deserves further investigation as a potential therapeutic agent in preventing restenosis after angioplasty.

Enalapril in the prevention of restenosis following intracoronary intervention in a swine model.

BACKGROUND: Restenosis following percutaneous transluminal coronary angioplasty continues to be a major limitation of the procedure. To test whether an angiotensin-converting enzyme inhibitor may reduce restenosis, this study utilized an atherosclerotic, stented, Hanford miniature swine model of restenosis. METHODS: Each animal first was started on an atherogenic diet and had balloon abrasion of the left anterior descending and right coronary arteries. Four months later, balloon-mounted coil stents were placed into the abraded coronary arteries of each animal. Twenty-four animals then were randomly assigned to one of two groups: enalapril, and control. The enalapril group received 50 mg orally twice daily starting 1 week before intracoronary stenting. RESULTS: Follow-up 2 months later revealed angiographic stenosis in the control group of 30% +/- 13%/25% +/- 10% (left anterior descending/right coronary artery) versus 37% +/- 9%/20% +/- 11% in the enalapril group (P = not significant). The change in minimal lumen diameter from immediately after stenting to follow-up was not significantly different between control and enalapril groups. Area stenosis and maximal intimal thickness obtained by morphometric analysis were also compared, and the mean percentage area stenosis for the control group was 39 +/- 12%/31% +/- 16% and for enalapril 36% +/- 14%/35% +/- 19%. The maximal intimal thickness in the control group was 573 microns +/- 204 microns/605 microns +/- 266 microns and in the enalapril group 530 microns +/- 220 microns/424 microns +/- 237 microns. There was no statistical difference. CONCLUSIONS: Enalapril fails to reduce restenosis in this animal model.

Rotational ablation of coronary artery lesions using single, large burrs.

Previous clinical use of the Rotablator in coronary artery disease has involved a sequential increase in burr sizes up to 2 mm in diameter and has often utilized balloon adjunct to achieve an optimal result. We report our experience and describe our technique using a single, large burr (2.25, 2.5, or 2.75 mm diameter) without balloon assistance. The burr size was selected to approximate 70-90 percent of the apparent normal lumen diameter. Thirty-one patients with 36 lesions of complex morphology (eccentric, irregular, calcified, ulcerated, at bends, at bifurcations, completely occluded, as well as balloon failures) were successfully treated with the Rotablator. Results were assessed by computerized quantitative angiography. The percent diameter stenosis (mean +/- SD) for the group was reduced from 69.8 +/- 11.3% to 30.9 +/- 10% (p less than 0.001). The mean absolute diameter stenosis increased from 0.9 +/- 0.3 mm to 2.2 +/- 0.3 mm (p less than 0.001). Angiographically visible dissections were seen in 4 patients and were uncomplicated in 2. One patient had a non-Q-wave myocardial infarction. A fourth patient had a presumed acute occlusion 36 hr after the procedure, necessitating emergency bypass surgery, but without Q waves on the electrocardiogram or wall-motion abnormalities on the echocardiogram. Nitroglycerin was infused through the Rotablator catheter and has considerably lowered the degree and frequency of spasm. No other acute complications occurred. The mean procedure time using a single burr was shorter than when multiple burrs were used: 56.5 vs. 97.3 min, respectively (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The coronary artery response to implantation of a balloon-expandable flexible stent in the aspirin- and non-aspirin-treated swine model.

Intracoronary stents may potentially alleviate some of the problems associated with coronary angioplasty. Since the anatomy and physiology of swine coronary arteries closely resemble those of humans, the response to implantation of the Glanturco-Roubin, balloon-expandable, flexible stent was studied in this model. Additionally, the effect of aspirin, 1 mg/kg/day orally, on this response was evaluated. Eighteen Hanford minature swine underwent stenting of the left anterior descending coronary artery. Two died within 24 hours of stent implantation. The 16 survivors were put to death at 4 (n = 4), 11 (n = 4), 28 (n = 4), 56 (n = 3), and 180 (n = 1) days. Angiographically, reduction of stent lumen diameter of 0.1 to 1.3 mm was observed and was maximum at 11 days, with gradual improvement at subsequent time periods. Scanning electron microscopy, transmission electron microscopy, and light microscopy showed early disruption of subjacent endothelium, and adherence of platelets to exposed subendothelium and stent wires. Microthrombi were readily apparent. At 11 days, intimal thickening, made up predominantly of smooth muscle cells with abundant extracellular matrix, was observed and covered the stent wires. At 28 days, regression of intimal thickening was apparent and a confluent endothelium with flow-directed orientation was seen. At 56 and 180 days, the luminal surface was smooth; intimal thickening averaged 525 microns over the stent wires and 55 microns away from the wires. Findings in aspirin-treated animals were similar to results in those that did not receive aspirin. Thus in this swine model, stent implantation results in a time-dependent and self-limited vascular response.

Factors determining improvement in left ventricular function after reperfusion therapy for acute myocardial infarction: primacy of baseline ejection fraction.

Improvement in left ventricular ejection fraction is a measure of salvage of ischemic myocardium after reperfusion therapy for acute myocardial infarction. The degree of improvement in left ventricular ejection fraction may be influenced by many factors. Therefore, 137 patients in whom paired radionuclide angiograms were obtained within 24 h of acute infarction and before hospital discharge were retrospectively evaluated to determine which factors most affect improvement in ejection fraction. Only baseline ejection fraction correlated significantly with improvement in ejection fraction by both univariate analysis (ejection fraction as a continuous variable; p less than 0.001; ejection fraction as a categorical variable, less than or equal to 45% versus greater than 45%, p less than 0.0001) and multivariate analysis (p less than 0.0001). Reperfusion status (patent versus occluded infarct artery) and extent of coronary artery disease (one, two or three vessel) were significant factors by multivariate but not by univariate analysis. Location of infarction, treatment modality and time to treatment did not correlate with change in ejection fraction by either statistical technique. Thus, of those factors tested, baseline left ventricular ejection fraction is the most potent predictor of improvement in ventricular function after acute infarction. Knowledge of baseline ejection fraction may be helpful in deciding whether to treat some patients with equivocal indications or contraindications for reperfusion therapy. Clinical trials of reperfusion strategies should stratify patients on the basis of baseline ejection fraction if ejection fraction is to be used as an end point for myocardial salvage.

Percutaneous transluminal coronary angioplasty in octogenarians.

OBJECTIVE: To assess the safety and short- and long-term outcomes of percutaneous transluminal coronary angioplasty in octogenarians. DESIGN: Retrospective chart review of clinical series. SETTING: Referral-based university medical center. PATIENTS: Consecutive series of 54 octogenarian patients (mean age, 82.4 years) who had percutaneous transluminal coronary angioplasty between March 1980 and December 1988. Of these patients, 91% presented with severe angina (Canadian Cardiovascular Society Class III or IV); 59% had unstable angina. Twenty-six patients (48%) had had a previous myocardial infarction and 15 (28%) had had previous coronary artery bypass surgery. Multivessel disease was present in 44 patients (81%). Follow-up ranged from 1 to 50 months (mean, 19 months). INTERVENTION: Percutaneous transluminal coronary angioplasty. MEASUREMENTS AND MAIN RESULTS: The angiographic success rate was 50 of 54 (93%; 95% CI, 81% to 98%) and the clinical success rate was 49 of 54 (91%; CI, 79% to 97%). Two patients had procedure-related myocardial infarction. Two patients died in the hospital, 1 from cardiac tamponade because of pacemaker perforation and 1 from cardiogenic shock after a myocardial infarction despite successful angioplasty. During the follow-up period 4 patients required bypass surgery, 2 had myocardial infarction, and 7 died (4 deaths were cardiac). Eleven patients (20%) had re-stenosis, 7 of whom were managed with repeat angioplasty, including 1 patient who had four procedures. At follow-up, 42 of 45 survivors (93%) were asymptomatic or had class II angina. The Kaplan-Meier survival for all patients, including those who died in the hospital, was 87% at 1 year and 80% at 3 years. Cumulative freedom from major cardiac events (death, myocardial infarction, or coronary bypass surgery) was 81% at 1 year and 78% at 3 years. CONCLUSIONS: Percutaneous transluminal coronary angioplasty can be done in octogenarians with a high rate of angiographic and clinical success, low complication rate, and a favorable long-term (3-year) outcome. As such, it is a treatment option in managing advanced coronary artery disease in this fragile group of patients.

Factors influencing the outcome of balloon aortic valvuloplasty in the elderly.

This study describes the short- and long-term outcome of 44 consecutive percutaneous balloon aortic valvuloplasty procedures performed in 42 elderly patients (age 77.8 +/- 7 years) with calcific aortic stenosis. The initial success rate was 95%, with the peak aortic valve pressure gradient declining from a mean of 82 +/- 32 mm Hg to 44 +/- 23 mm Hg and aortic valve area increasing from a mean of 0.59 +/- 0.15 cm2 to 0.83 +/- 0.40 cm2. One procedure-related death occurred and an additional three patients died less than or equal to 30 days after balloon aortic valvuloplasty. These patients all had New York Heart Association (NYHA) class IV heart failure symptoms prior to the procedure and their mean left ventricular ejection fraction (LVEF) (28 +/- 7%) was lower than that of hospital survivors (52 +/- 13%) (as was their ratio of left ventricular [LV] wall thickness-to-cavity ratio [0.50 +/- 0.10 versus 0.70 +/- 0.15]). At the time of hospital discharge after valvuloplasty, 76% of patients were asymptomatic or markedly improved (NYHA class I or II). After a mean follow-up of 15.5 months (range 2 to 26 months), however, 10 patients had died and 15 had undergone aortic valve replacement for recurrence of NYHA class III or IV symptoms. The adjusted 1- and 2-year survivals were 0.68 and 0.62, respectively, and adjusted 2-year event-free survival was 0.25. Proportional hazard regression analysis indicated that LVEF less than 40% was the only variable affecting survival (p less than 0.01) and was a possible indicator of event-free survival (p = 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)

Adjuvant therapy for intracoronary stents. Investigations in atherosclerotic swine.

Early thrombosis has complicated human stent implantation in several trials. To determine the best anticoagulation/antiplatelet therapy to maintain stent patency after percutaneous transluminal coronary angioplasty, we implanted the flexible balloon-expandable coil stent into the left anterior descending coronary artery of 28 atherosclerotic 8-month-old Hanford miniature swine. Animals were randomly assigned to one of three treatment groups: group A, aspirin (1 mg/kg/day) and dipyridamole (1 mg/kg three times a day); group B, aspirin and dipyridamole (same doses) plus Coumadin (dose required to prolong prothrombin time 1.3-1.5-fold that of normal); and group C, control. Adjuvant therapy was begun 3 days before stenting. Two pigs (one from group A and one from group B) died during implantation, both without thrombosis. Twenty-six animals survived until follow-up angiography and sacrifice at 1 month. No occlusive thrombosis of the stent occurred in survivors. Reduction of the stent lumen diameter was observed in every case at follow-up. Percent lumen reduction was 19% in group A, 26% in group B, and 24% in group C. Marked smooth muscle cell hyperplasia was seen by light and transmission electron microscopy at stent struts. Scanning electron microscopy of the luminal surface showed a variable morphology consisting of normal endothelium, adherent leukocytes, stellate periluminal cells, and occasional fibrin strands and red blood cells. Luminal narrowing was not affected by anticoagulation therapy, antiplatelet drugs, cholesterol level, or stent sizing. We conclude that occlusive thrombosis does not complicate stent implantation in this model but that substantial luminal narrowing due in part to smooth muscle hyperplasia does occur. The significance of luminal narrowing at the stent site requires further study.

Warfarin sodium for anticoagulation of atherosclerotic miniature swine.

Warfarin sodium (Coumadin) has been used as an effective anticoagulating agent in human medicine for many years, although careful monitoring of its effects are necessary to avoid excessive anticoagulation. Previous experience with this drug for chronic anticoagulation therapy in miniature swine has been limited. The effect of warfarin sodium was studied by measuring prothrombin time in twelve 8-month-old Hanford miniature swine. The pigs had been fed a high-cholesterol diet and had undergone a prior coronary artery abrasion procedure for development of an atherosclerotic coronary disease model. Atherosclerosis was induced by feeding a high-cholesterol diet. Baseline prothrombin time ranged from 12.8 to 15.0 s (13.7 s mean). Prothrombin time was determined daily for the first 5 days of treatment and at least twice weekly thereafter until the animals were sacrificed. Animals received warfarin for 37-41 days. Prothrombin time could be increased 33-50% by once daily oral administration of warfarin 0.04-0.08 mg/kg. Oral administration of more than 0.08 mg/kg as a maintenance dose resulted in the death of two pigs. Most animals responded well to 0.08 mg/kg for the first 3 days of treatment followed by a maintenance dose of 0.06 mg/kg. Dosage was adjusted periodically when prothrombin times exceeded 50% above baseline. It is our experience that monitoring prothrombin time at least twice weekly and adjusting the maintenance dose can eliminate death losses due to warfarin intoxication.

Comparison of quantitative coronary angiography to visual estimates of lesion severity pre and post PTCA.

Quantitative coronary angiographic measurements and visual estimates of coronary lesion severity were compared prospectively before, immediately following, and 6 months following percutaneous transluminal coronary angioplasty. Mean percent diameter stenosis before angioplasty was 87.9 +/- 9.9% by visual analysis and 64.6 +/- 9.2% by quantitative coronary angiography (p = 0.0001). Differences between these two techniques were also found immediately post-angioplasty (visual analysis 29.5 +/- 11.8%, quantitative coronary angiography 22.8 +/- 11.8%, p = 0.0002) and at 6 months (visual analysis 46.5 +/- 27.4%, quantitative coronary angiography 30.2 +/- 20.4%, p = 0.0001). These differences significantly affected the determination of restenosis by three definitions. (1) Lesion recurrence with greater than or equal to 50% stenosis at follow-up: 38 of 92 (41%) by visual analysis versus 20 of 92 (22%) by quantitative coronary angiography (p less than 0.01). (2) Increase of greater than or equal to 30% stenosis: 34 of 92 (37%) by visual analysis versus 20 of 92 (22%) by quantitative coronary angiography (p less than 0.01). (3) Loss of 50% of previous improvement: 31 of 92 (34%) by visual analysis versus 24 of 92 (26%) by quantitative coronary angiography (p = 0.08). In addition, determination of success or failure of percutaneous transluminal coronary angioplasty was affected by the interpretative technique, but these differences were not statistically significant. We conclude that visual estimates of lesion severity are consistently and significantly higher than quantitative measurements. Consequently, restenosis rates, using currently applied definitions, differ considerably depending on the method of analyzing lesion severity.

Assessment of myocardial perfusion in humans by contrast echocardiography. I. Evaluation of regional coronary reserve by peak contrast intensity.

Myocardial contrast echocardiography was performed during coronary angiography with 2 ml of sonicated meglumine diatrizoate sodium 76% (meglumine) in 40 patients (ranging in age from 25 to 79 years) before and 10 to 15 s after intracoronary injection of papaverine, 8 mg into the right coronary artery (n = 43) and 10 mg into the left (n = 46). The same protocol was repeated in 17 patients 5 to 10 min after completion of coronary angioplasty. In 13 patients with normal coronary angiograms, peak contrast intensity corrected for background myocardial intensity was measured in 36 regions and was found to increase after papaverine from 36 +/- 16 to 55 +/- 22 U (p less than 0.001). In contrast, in the 27 patients with angiographic evidence of coronary artery disease, peak intensity in 64 regions remained unchanged after papaverine (35 +/- 22 versus 36 +/- 23 U). An increase in peak intensity greater than or equal to 10 U was 80% sensitive and 92% specific for coronary artery disease. After successful coronary angioplasty, peak intensity in the involved regions improved significantly (p less than 0.001) during baseline contrast injections (from 32 +/- 16 to 50 +/- 25 U) as well as in the postpapaverine contrast injections (from 30 +/- 12 to 60 +/- 26 U). In conclusion, measurement of peak contrast intensity after intracoronary injections of sonicated meglumine provides a relative index of myocardial perfusion that allows assessment of regional coronary reserve in patients with coronary artery disease. This may be of particular value in evaluating the immediate effects of coronary angioplasty on myocardial perfusion.

Bretylium and diltiazem in porcine cardiac procedures.

The use of miniature swine as a model for cardiovascular diseases of humans is becoming more popular for many reasons. One of the problems involved in using swine is their propensity for fatal cardiac arrhythmias during surgical procedures requiring general anesthetics, especially cardiac procedures. In preparation for use as a model of human atherosclerotic coronary artery disease, 30 three-month-old (15 kg) Hanford miniature swine underwent left heart catheterization, coronary angiography, and abrasion of the left anterior descending coronary artery. All pigs were treated with diltiazem HCl 30-60 mg (2-4 mg/kg) three times daily and aspirin 25 mg once daily, both given orally for three days before surgery. General anesthesia was induced with a combination of ketamine HCl 25 mg/kg, atropine sulfate 0.1 mg/kg, and acepromazine 0.22 mg/kg, all given intramuscularly. Halothane 1-2% and nitrous oxide 30% were used to maintain general anesthesia after endotracheal intubation. After successful cannulation of the femoral artery, all animals were given 200 units/kg heparin and 5 mg/kg bretylium tosylate intravenously. The electrocardiogram and mean blood pressure were monitored throughout the procedure. No significant change in blood pressure was noted during the procedure. Intracoronary nitroglycerin 200 micrograms was administered prior to abrasion of the left anterior descending with a 2.0-mm angioplasty balloon. The pigs were allowed to recover after routine closure of the incision. One pig (1/30) died during the abrasion procedure as a result of ventricular fibrillation. This represents a low, acceptable mortality using the present regimen compared with other regimens.

Effect of bradycardia on dispersion of ventricular refractoriness.

The effect of bradycardia on dispersion of ventricular refractoriness was evaluated. Refractory periods were measured at 3 right ventricular sites in 16 patients with severe bradycardia (average heart rate 39 +/- 5 beats/min) and were compared with those measured in 11 control subjects, (average heart rate 72 +/- 12 beats/min). Patients with bradycardia had significantly longer effective (377 +/- 36 ms) and functional (421 +/- 39 ms) refractory periods (ERP and FRP) than control subjects (ERP 296 +/- 25 ms, FRP 346 +/- 18 ms) (p less than 0.001). However, dispersion of refractoriness was similar in the 2 groups. Dispersion of ERP was 43 +/- 38 ms and FRP was 48 +/- 35 ms in patients with bradycardia. In control subjects dispersion of ERP was 37 +/- 12 ms, and FRP was 36 +/- 20 ms. Pacing of 120 beats/min significantly decreased ERP and FRP in both groups. Pacing shortened dispersion significantly in control subjects. In patients with bradycardia, pacing failed to significantly decrease dispersion. Compared with control subjects with normal heart rates, patients with bradycardia have longer absolute refractory periods but do not have significantly increased dispersion of refractoriness. Single and double, twice threshold ventricular extrastimuli (S2 and S3) failed to induce ventricular tachycardia in any patient during bradycardia. Bradycardia alone does not appear to be a factor in the induction of ventricular tachyarrhythmias.

The isoinhibitors of chymotrypsin/elastase from Ascaris lumbricoides: the reactive site.

Five isoinhibitors of chymotrypsin/elastase present in aqueous extracts of Ascaris were isolated. The reactive site in each isoinhibitor, the peptide bond that during encounter is positioned over the catalytic site in chymotrypsin, is Leu-Met. This bond was hydrolyzed by incubating intact isoinhibitors with 5-25 mol% chymotrypsin at pH 3.2 for 4-6 days (isoinhibitor 1) or 2.5-5 weeks (isoinhibitors 2-5). The reaction under these conditions did not proceed beyond 60% modified isoinhibitor (peptide bond hydrolyzed) and 40% intact inhibitor. The Leu-Met bond, hydrolyzed in modified isoinhibitor, can be resynthesized at pH 7.6 by incubating modified inhibitor with a stoichiometric amount of chymotrypsin bound to Sepharose CL-4B and then dissociating the complex in a kinetically controlled fashion with 5% trichloroacetic acid. The product, intact inhibitor, was obtained in greater than 80% yield. The site in the isoinhibitor that is positioned over the catalytic site in elastase during encounter is the same as for encounter with chymotrypsin. The Leu-Met bond hydrolyzed during encounter with elastase can be resynthesized by chymotrypsin. Chymotrypsin and elastase bind to the inhibitor at the same site.

Modification of the carboxypeptidase A active site residue Glu-270 prevents interaction with a protein protease inhibitor from Ascaris.

The involvement of two active site residues of carboxypeptidase A in binding a protein inhibitor from Ascaris was studied. Glu-270 was modified with N-ethyl-5-phenylisoxazolium-3'-sulfonate and Tyr-248 was modified with tetranitromethane or diazotized arsanilic acid. Modification of Glu-270 abolished protein inhibitor binding and Glu-270 was protected from modification when the enzyme was bound to the protein inhibitor. In contrast, modification of Tyr-248 did not abolish protein inhibitor binding, nor did such binding protect Tyr-248 from modification. The absorption isosbestic point of arsanilazocarboxypeptidase A (Tyr-248 chemically modified) underwent a blue shift from 428 to 416 nm when the modified enzyme was bound to the protein inhibitor between pH 7.7 and 9.0. The 416 nm isosbestic point is characteristic of the loss of interaction between modified Tyr-248 and the active site zinc ion. These results with a protein inhibitor can be compared to substrate catalysis in which Tyr-248 moves away from the active site zinc ion of carboxypeptidase A when substrate binds. The close association of Glu-270 with Ascaris inhibitor interaction is consistent with other results which show that of the active site residues, only the modification of Glu-270 completely abolishes catalysis.