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Ultrasound angioplasty is a newly developed technology for percutaneous arterial recanalization. Data suggest that ultrasound is particularly effective in ablating fresh thrombi. Arterial walls were found to be resistant to ultrasound ablation. Thrombi, aortic wall segments, and hydroxy-proline gelatin were studied in vitro to determine their respective ablation rates. The elasticity of the samples was determined in a force-mode apparatus. The cavitation threshold was determined in an arterial phantom apparatus. Thrombi displayed ablation rates that were [greater than> 20 times higher than those of aortic wall samples (591 [+ or -] 82 vs 25 [+ or -] 14 mg/s, p [less than] 0.001). The differences in ablation rates were accompanied by significantly lower elasticities in the thrombus group compared with those in the aortic wall group (0.16 [+ or -] 0.05 vs 312 [+ or -] 37 g/[cm.sup.2], p [less than] 0.001). Experiments with hydroxyproline gelatin suggest a negative correlation (r = -0.90) between elasticity and ultrasound ablation. Ultrasound ablation of thrombi was evident only above the cavitation threshold. Thus, ultrasound angioplasty has the potential to induce the selective injury required for successful transluminal intervention in the treatment of thrombus rich lesions.

The effects of plasma lipids on the clinical and angiographic parameters of 134 patients, in whom coronary angioplasty was in 157 vessels, were prospectively examined. During a 6-month follow-up, restenosis was detected angiographically in 39 patients (29%; 45 vessels). None of the clinical, biochemical, or angiographic variables examined was predictive of stenosis and the tendency of a vessel to restenose was not patient-dependent but rather lesion-related. However, restenosis developed in 31 of 102 vessels (300A) in patients with high-density lipoprotein (HDL) cholesterol [less than or equal to] 40 mg/dl, compared with restenosis in 10 of 55 vessels (19%) in patients with HDL cholesterol >40 mg/dl (p = 0.092). No significant differences were observed when restenosis rates were compared in patients with total cholesterol levels >250 mg/dl or 160 mg/dl and

An in vitro model was designed to test the hypothesis that thrombi of varying composition have different echogenic patterns. Thrombi were prepared in specially designed tubes, mounted on a holder that allows introduction of an intravascular ultrasound catheter rotated inside a subselective sheath. The thrombi were made by the addition of thrombin to whole blood, platelet-rich plasma, and to mixtures of whole blood and platelet-rich plasma with increasing concentration of whole blood relative to the volume of the mixture in the following ratios: 1:5, 2:5, 3:5 and 4:5. Sixty-six thrombi prepared from 11 blood samples of healthy subjects were studied and compared with control tubes filled with saline solution. Platelet-rich thrombi showed low echogenicity similar to saline solution. Whole blood thrombi appeared uniformly 'speckled.' Mixtures of whole blood and platelet-rich plasma showed a gradual increase in echogenicity with an increasing amount of whole blood in the mixture. Quantitative videodensitometry compared the gray scale intensity of each image relative to background saline. The mean value of echogenicity of platelet-rich thrombi was 0.9 [+ or -] 1.2, and the mean value of whole blood thrombi was 13 [+ or -] 5.3 Platelet-rich thrombi are echolucent, and the main echogenic reflectance of thrombi originates from red blood cells. The ultrasound intensity is in linear relation to the amount of red blood cells in the thrombus. (Am J Cardiol 1994;73:1053-1057)

Electrophysiologic studies have shown that intravenous magnesium sulfate prolongs atrioventricular (AV) nodal conduction and refractoriness and thus could play a role in the management of patients with paroxysmal AV reentrant supraventricular tachycardia (SVT). The present study evaluates the clinical and electrophysiologic effects of intravenous magnesium sulfate in patients with SVT and compares them with those of adenosine triphosphate (ATP), one of the most potent drugs in the treatment of this arrhythmia. Patients with inducible sustained SVT were treated with ATP (10 or 20 mg) and magnesium sulfate (2 g over 15 seconds) during electrophysiologic study. If the tachycardia failed to terminate by the sixth minute, an additional 2 g dose of magnesium was given. ATP (10 or 20 mg) was significantly better than magnesium for terminating induced tachycardias (14 of 14 vs 6 of 14, p

Heart attacks (myocardial infarction) occur when ischemia (decrease in oxygen supply due to reduced or no blood flow) is so severe that a portion of the heart muscle can not function and may die. Heart attacks may be precipitated by the lodging or formation of a clot in a coronary artery. A relatively novel therapeutic approach has been to give thrombolytic (clot-breaking) agents that disrupt the clot and restore blood flow. However, thrombolytic therapy is not successful in a number of heart attack patients, who may need emergency treatment if they are to survive. To improve survival of patients with myocardial infarction, it is important to determine which patients are most likely to be responsive to thrombolytic therapy. Electrocardiogram provides an indication of heart function during each heartbeat, and elevation of the ST segment of the electrocardiogram has generally been regarded as an indicator of heart ischemia. However, some studies have suggested that ST elevation is not sensitive enough to detect restoration of coronary artery flow following a heart attack. The usefulness of ST elevation and other indicators of heart function were evaluated in 286 heart attack patients treated with alteplase, a thrombolytic agent. Alteplase was given within four hours of symptom onset, the period when thrombolytic therapy is most likely to be effective. ST elevation diminished quickly in 189 patients, but persisted in 97 patients. Rapid resolution of ST elevation was significantly associated with a good medical outcome; the group in which this occurred had a better initial medical status. However, early reperfusion was independent of this factor and correlated significantly with better heart function and a lower rate of illness and death. Although angiography was used to determine if reperfusion of coronary arteries occurred, correction of ST segment elevation was a better predictor of medical outcome. Rapid resolution of pain was not associated with persistent elevation or normalization of ST segment. Resolution of ST elevation may also reflect the contribution of other factors important to survival of heart tissue, as well as reperfusion. The results also indicate that high-risk patients, such as those with congestive heart failure, may require additional therapy, in spite of resolution of ST elevation. (Consumer Summary produced by Reliance Medical Information, Inc.)

Although both the European Cooperative Study Group and the Thrombolysis in Myocardial Infarcdon IIB trial indicated that aregiography and angioplasty as routine measures after thrombolytic treatment do not improve clincal outcome in patients with acute myocardial infraction, the potential benefit of angioplasty may have been negated by the fact that the precedure was too soon ( (Am J Cardiol 1990;66:538-545), A major heart attack, or an acute myocardial infarction (MI), results from the deterioration of heart tissue due to the cessation of blood supply to the heart. Patients with MI are treated with thrombolytic agents that break up blood clots blocking the blood supply to the heart. Invasive procedures, such as angiography (the X-ray of the blood vessels supplying the heart) and angioplasty (the repair of the narrowed or obstructed blood vessels) may also be performed. Studies have shown that such invasive procedures do not improve the outcome of patients with MI after thrombolytic therapy. However, it is possible that angioplasty is not beneficial when it is performed too early (less than 32 hours after admission). The effectiveness of delayed angioplasty was compared with that of conservative treatment in 201 patients with acute MI. All patients received recombinant-type plasminogen activator, which prevents blood clot formation. The invasive group consisted of 97 patients who underwent angiography and angioplasty five days after drug treatment. The conservative group consisted of 104 patients who only underwent angiography after recurrent chest pain associated with MI or exercise. In the invasive group, 92 patients underwent angiography, 49 had angioplasty, and 11 required coronary artery bypass grafting (CABG), a surgical procedure to restore the blood flow to the heart. Among patients of the conservative group, 40 developed ischemia, an insufficient blood supply to the heart; 39 underwent angiography; 20 had angioplasty; and four required CABG. The recurrence of MI and maintenance of left ventricle function were similar for both invasive and conservative groups eight weeks after discharge from the hospital. If only the deaths which occurred after the scheduled invasive procedures are considered, 5 of 97 patients in the invasive group and none of 100 patients of the conservative group died within the 10-month follow-up period. Re-hospitalization was more frequent among patients of the conservative group and was associated with a history of chest pain. These findings suggest that conservative treatment is preferable to invasive treatment of patients with acute MI. (Consumer Summary produced by Reliance Medical Information, Inc.)

A very important aspect in the successful treatment of patients following an acute myocardial infarction (MI) is prompt initiation of thrombolytic treatment. Thrombolysis relies upon drugs that are capable of dissolving clots in the area of the infarction, the tissue death resulting from reduced blood supply. A thrombolytic agent has been demonstrated to be most effective if administered within two hours after the onset of pain. This prompt drug therapy can preserve heart function, specifically, left ventricular function, and can reduce short- and long-term mortality. The goal of this study was to correlate clinical outcome with the time from onset of symptoms to initiation of thrombolytic treatment with a recently approved new drug, recombinant tissue plasminogen activator (rt-PA). One hundred ninety patients with AMI were administered rt-PA an average of two hours after the onset of their symptoms. Prehospitalization thrombolysis was possible in a substantial number of these patients by use of mobile intensive care units. Short- and long-term effects of early versus late administration of rt-PA were evaluated by examining left ventricular function, and cardiac morbidity and mortality. The overall two-year mortality was low; there were 10 deaths out of the 190 patients treated. Eight of those deaths (4 percent) were cardiac in nature. The patients that were treated within two hours from the onset of symptoms had a lower 60-day and 24-month mortality than patients treated two to four hours after symptoms began. It is also important to understand that the 96 patients who received early treatment were generally more seriously ill, which can be interpreted to mean that sicker patients seek treatment sooner. It is essential that patients seek early treatment in order to salvage heart muscle tissue. Unfortunately, many patients delay seeking treatment by one to two hours and the initiation of valuable thrombolytic treatment is delayed. Mobile intensive care units are valuable in providing treatment early in the homes of patients and this method was found to be both safe and effective. The authors recommend this prehospital therapy to shorten the interval between symptom onset and treatment initiation to potentially reduce mortality. (Consumer Summary produced by Reliance Medical Information, Inc.)

Sami Viskin, M.D.; Bernard Belhassen, M.D.; and Shlomo Laniado, M.D. We report the case of a patient who had development of ventricular fibrillation following rapid intravenous administration of magnesium sulfate [...]